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Poly(ethylene terephthalate) (PET) and polyethylene (PE) are two of the most commonly used polymers in the packaging industry, and they make up a large portion of the recycling stream. Adhesion between these two immiscible polymers is poor without compatibilization. Maleic anhydride (MAH) grafted PE is a popular compatibilizer for PET/PE but is limited by the slow rate of reaction. In this study, we propose tin additives for improving adhesion and explore the mechanism of that improvement. We demonstrate that either dibutyltin oxide (DBTO) or di-n-octyltin oxide (DOTO) can dramatically enhance adhesion with only 60 s of contact time during lamination. A range of MAH and DOTO concentrations are examined, yielding adhesion up to 1300 J/m2. Possible reactions at the interface are investigated with small molecule model compounds, namely 1-hexadecanol, octylsuccinic anhydride (OSA), and ethylene glycol dibenzoate. DOTO does not improve the reaction rate in the hexadecanol–OSA system. This suggests that another...

The extensive researches about the thermodynamic and intrinsic kinetic of disproportionation reaction of methyl phenyl carbonate to diphenyl carbonate were investigated independently with dibutyltin oxide as a catalyst, at a temperature range of 433.15–473.15 K and different catalyst concentrations in a stirred batch reactor, for a deeper knowledge of reaction essence. This reaction was found endothermic and showed hardly any reaction in the absence of catalyst which indicate an inferior kinetic characteristics. The reaction rate increases with an increasing catalyst concentration until the concentration went to 8.08 × 10−4 mol mol−1. A possible mechanism involving an in-situ Sn-based species was proposed and finally verified by a good agreement between experimental and simulated data. The available Sn-based species was then demonstrated to play a real catalytic role by extra experiments. All results can also be further utilized to explore the essence of transesterification reaction network.

A simple approach was developed for the solvent-free regioselective functionalization of carbohydrate polyols with 4-toluesulfonyl (tosyl) group, allowing the easy and quick activation of a saccharide site with a tosylate leaving group. The method is based on the use of catalytic dibutyltin oxide and tetrabuylammonium bromide (TBAB), and a moderate excess of N,N-diisopropylethyl amine (DIPEA) and tosyl chloride (TsCl), leading to the selective functionalization at 75 °C of a secondary equatorial hydroxy function flanked by an axial one in a pyranoside. The procedure is endowed with several advantages, such as the use of cheap reagents, experimental simplicity, and the need for reduced reaction times in comparison with other known approaches.

In this paper degradable shape-memory polymer networks synthesized from oligo[(L-lactide)-ran-glycolide]dimethaycrylates are introduced. The macrodimethacrylates are prepared via a two-step synthesis: hydroxy telechelic oligo[(L-lactide)-ran-glycolide]s with number average molecular weights Mn ranging from 1000 to 5700 g mol−1 were synthesized by ring-opening polymerization from L,L-dilactide, diglycolide and ethylene glycol as initiator using dibutyltin oxide as the catalyst. These oligodiols are reacted with methacryloyl chloride resulting in terminal methacrylate groups. Crosslinking of macrodimethacrylates is performed under exposure to UV light without applying a photo initiator. The polymer networks obtained are transparent and hydrolytically degradable. While the mechanical properties at temperatures higher than Tg depend on crosslinking density, Tg is almost constant at about 55 °C. The shape-memory functionality of the amorphous polymer network was investigated by cyclic, thermomechanical tests under the systematic variation of different programming parameters. Good shape-memory properties with strain recovery rates close to 100% were obtained under stress-controlled programming. Under strain-controlled conditions, it needs to be considered that relatively high stresses can be generated during programming. Potential biomedical applications are intelligent implants or smart drug release systems.

A family of pentacoordinated diorganotin(IV) compounds was synthesized and characterized through the advantageous approach of a multicomponent methodology involving the reaction between 4-(diethylamino)salicylaldehyde, dibutyltin oxide and including a series of l -amino acid fragments (alanine, valine, leucine, isoleucine, phenylalanine, tyrosine and methionine), all carried out in one-step, in excellent yields. Structures were elucidated by FTIR, HRMS and solution NMR (1H, 13C and 119Sn). Diorganotin(IV) derivatives crystallized easily and five unreported molecular structures were solved and analyzed by SC-XRD experiments; depending on the orientation of the alkyl residues different isomorphic arrays were found. Finally, pentacoordinated diorganotin(IV) complexes were tested against tumoral cell lines, HCT-15 (colon adenocarcinoma), HeLa (cervical uterine adenocarcinoma), MCF-7 (breast adenocarcinoma) and PC-3 (human prostate cancer) in order to evaluate their in vitro cytotoxicity.

The “tumor-seeking” role of bleomycin (BLM) disaccharide has been demonstrated to serve as a promising tool for cancer diagnosis and a potential ligand for targeted therapy. However, these practical applications are often hampered by the lack of BLM disaccharide. Herein, an efficient multi-gram synthesis of peracetylated BLM disaccharide 20 is achieved by a TMSOTF-mediated glycosidation coupling manner in 43.6% overall yield in terms of benzyl galactoside. The critical innovation of the synthetic strategy is that inexpensive benzyl galactoside was first adopted to prepare an L-gulose subunit 3 as a glycosyl acceptor, with a much shorter route in 73.0% yield, and a 3-O-carbamoyl-mannose donor 4 was achieved in 47.2% yield by lowering the amount of dibutyltin oxide, and merging aminolysis and selective deacetylation into a one-pot reaction. Next, the incorporation of BLM disaccharide into 10-hydroxycamptothecin (10-HCPT), a non-specific model compound, to form conjugate 1 could significantly improve the antitumor activity and display obvious selectivity toward cancerous and normal cells in comparison with 10-HCPT. Moreover, BLM disaccharide itself was non-cytotoxic, clearly indicating the importance and potential of BLM disaccharide in solving the targeted antitumor therapy of cytotoxic drugs.

Starting from dibutyltin oxide, four catalysts were synthesized, namely the dibutyltin bisphenoxides of phenol (SnPh), 4-chlorophenol (SnCP), 4-hydroxybenzonitrile (SnCN) and pentafluorophenol (SnOPF). With the first three catalysts polymerizations of l -lactide at 160 °C in bulk yielded large fraction of linear chains having phenylester end groups at short reaction times. At longer times the fraction of cycles considerably increased at the expense of the linear chains, when SnCN was used as catalyst. With SnOPF only cyclic polylactides were obtained at low Lac/Cat ratios (

Schiff base butyltin complexes C1 ∼ C3 have been synthesized via the reaction of dibutyltin oxide with the substituted salicylaldehyde-o-aminophenol Schiff base ligands (L1 ∼ L3), respectively. The...

Konjac glucomannan, built of β-1,4-linked mannose and glucose, was methylated after treatment with dibutyltin oxide/MeOH in pyridine. Best results were obtained in acetonitrile/DMF in the presence of TBAB and K2CO3. While total DS was only 0.1–0.15 and not significantly enhanced in the tin-promoted reaction, the manno-/gluco- (cis-/trans-diol) and the regioselectivity was completely changed with DSMan/DSGlc increasing from 0.9 to 1.8, a strong preference for secondary over primary OH, and a total order of reactivity being M3 > M2 ≥ G2 > G6 ≥ M6 ≥ G3. The influence of the amount of K2CO3, Bu2SnO, and temperature was studied. By repeated reaction a DS of 0.28 was gained without loss in selectivity. In a solvent-free one-pot stannylation/methylation reaction, a DS up to 0.3 was achieved. Surprisingly, any differences between the two stereoisomeric sugar constituents were leveled under these conditions, and regioselectivity was changed to the order M6 ≈ G6 ≫ M3 ≈ G3 > M2 ≈ G2.

Four new p-aminobenzenesulfonate organotin complexes, [(n-Bu3Sn)(O3SC6H3-NH2-4)]n (1), [(n-Bu2Sn)4(O)2(OH)2(O3SC6H4-NH2-4)2] (2), [(Me2Sn)4(O)2(OH)2(O3SC6H4-NH2-4)2] (3) and [{(n-BuSn)12O14(OH)6}(O3SC6H4-NH2-4)2·3C4H8O2] (4·diox), were synthesized by reaction of p-aminobenzenesulfonic acid with tributyltin oxide, dibutyltin oxide, dimethyltin oxide and monobutyltin oxide, respectively. These complexes were characterized by elemental analysis, FT-IR, NMR (1H, 13C, 119Sn) spectroscopy as well as single-crystal X-ray diffraction. The crystal structure of complex 1 reveals that it is a 1D zig-zag chain structure and further interlinked into a 2D network by intermolecular interaction (N-H⋯O). The structure analysis indicates that complexes 2 and 3 are the ladder-like structure including three alternate Sn2O2 rings, and further result in the formation of a 3D supramolecular architecture for 2 and a 2D supramolecular network for 3 by extensive hydrogen-bonding interactions (O-H⋯O, N-H⋯O). Complex 4 exhibits a dodecanuclear organooxotin cages, which are connected into a hydrogen-bonded 2D structure. Furthermore, complexes 1-4 were evaluated for their in vitro cytostatic activity against the human lung cancer cells (A549) and the human hepatocellular carcinoma cells (HepG-2). The preliminary screen shows that organotin derivatives with increasing number n-butyl group exhibitsignificantly higher cytostatic activity, and much higher than methyl group.

Schiff base organotin(IV) complexes C1 ∼ C5b have been synthesized via the reaction of the substituted salicylaldehyde-o-aminophenol Schiff base ligands (L1 ∼ L3) with the dibenzyltin dichloride, n-butyltin trichloride or dibutyltin oxide, respectively. The complexes have been characterized by IR, UV–Vis, 1H NMR, 13C NMR spectra, elemental analysis and the crystal structures have been determined by X-ray diffraction. The anticancer activity of the Schiff base ligand and complexes C1 ∼ C5b against five species of cancer cell which are Hela, MCF7, HepG2, Colo205, NCI H460 were tested respectively, the tests showed that C1 ∼ C5b exhibited significant anticancer activity for the cancer cells in comparison with the ligand, and the activity was greater than carboplatin.

Self-assembly of dibutyltin oxide with 3-(1,3-dioxo-2,3-dihydro-1H-phenalen-2-yl)benzoic acid (HL) produces (n-Bu)2SnL2 (complex 1) when benzene is used as solvent, while the reaction generates {[(n-Bu)2SnO]2L}2·C7H8 (complex 2) when toluene is reactive solvent. The novel organotin carboxylate (n-Bu)2SnL2 (complex 1) was characterized by elemental analysis, IR, 1H, 13C, 119Sn NMR spectroscopy. Single crystal X-ray study reveals that 1 is a dialkyltin carboxylate monomer possessing crystallographically imposed two-fold symmetry. Ligand HL in 1 chelates with tin atom in bidentate coordination mode. The molecules of 1 build its complicated 1D, 2D and 3D structures via intermolecular hydrogen bonds, and π···π interactions can be found in the 3D architecture. The preliminary fluorescence activity and antitumor activity of the complex were also studied.

The transesterification reactions to diphenyl carbonate (DPC) from dimethyl carbonate (DMC) and phenol are the key steps to the green production of polycarbonate polymers (PC). The transesterification equilibrium constants were determined under temperatures from 453.2 to 493.2 K, and the reaction kinetics catalyzed by single tetrabutyl titanate, dibutyltin oxide, and their combinations was measured. By taking into account the effect of catalyst, the simplified kinetic model was developed involving the transesterification of DMC and methyl phenyl carbonate (MPC) with phenol respectively, the disproportionation of MPC, and the formation of by-product anisole. The kinetic model fitted experiments well under various temperatures and owns excellent predictive ability on the effect of catalyst concentrations. The reverse reaction of MPC transesterification with phenol, as well as that of the disproportionation of MPC, was found to be independent of temperatures within the investigated conditions. The thermodynamic information and kinetic model reported here will provide valuable insight into the understanding of the transesterification process from DMC to DPC. This article is protected by copyright. All rights reserved

4-(3,4-Dihydroxybenzoyloxymethyl)phenyl-O-?-D-glucopyranoside (DBPG, 1 ), a polyphenolic glycoside previously isolated from Oregano(Origanum vulgare L.) in 0.08% isolated yield, was synthesized in five chemical steps with 41.4% overall yield. First, 4-(hydroxymethylphenyl)-2,3,4,6-tetra-O-acetyl-b-D-glucopyranoside 4 was obtained in 53.2% yield by selective glycosylation of 4-hydroxybenzyl alcohol 3 with 2,3,4,6-tetra-O-acetyl-?-D-glucopyranosyl bromide 2 in a mixture of chlorobenzene and aqueous CsOH using triethylbenzylammonium chloride (TEBAC) as a phase transfer catalyst. Then, this product was esterified with 3,4-diacetoxylbenzoyl chloride 7 to generate 4-(3,4-diacetoxybenzoyloxy-methyl) phenyl 2,3,4,6-tetra-O-acetyl-b-D-glucopyranoside 8 in 95% yield. Finally, selectively global deacetylation of 8 was performed in a mixture of dibutyltin oxide and methanol under reflux to afford 1 in 94.8% yield.

The regio- and stereoselective glycosylation at the 6-position in 2,3,4,6-unprotected hexopyranosides has been investigated with dibutyltin oxide as the directing agent. Perbenzylated hexopyranosyl bromides were employed as the donors and the glycosylations were promoted by tetrabutylammonium bromide. The couplings were completely selective for both glucose and galactose donors and acceptors as long as the stannylene acetal of the acceptor was soluble in dichloromethane. This gave rise to a number of 1,2-cis-linked disaccharides in reasonable yields. Mannose donors and acceptors, on the other hand, did not react in the glycosylation under these conditions.

Dibutyltin oxide (Bu2SnO) mediated cyclodehydration or sulfonylation of 1,2,4-triols is predictably diastereoselective depending on the steric bulk of the substituents at C4. A larger difference (ΔA-value >1 kcal/mol) leads to the syn-1,2,4-triols favouring cyclodehydration (78–85%) to form 3-hydroxytetrahydrofurans, with the anti-1,2,4-triols favouring monosulfonylation (66–87%). Triols from symmetrical ketones preferentially undergo cyclodehydration in high yield (>75%) due to a gem-disubstituent effect. Thus, the 1,2,4-triols derived from simple cyclic ketones also favour cyclodehydration to form spirocyclic 3-hydroxytetrahydrofurans in 72–79% yields.

The methanolysis of jojoba oil has been studied in the presence of tin powder, dibutyltin diacetate (C 4 H 9 ) 2 Sn(OOCCH 3 ) 2 , dioctyltin diacetate (C 8 H 17 ) 2 Sn(OOCCH 3 ) 2 , dibutyltin oxide (C 4 H 9 ) 2 SnO, dioctyltin oxide (C 8 H 17 ) 2 SnO, diphenyltin oxide (C 6 H 5 ) 2 SnO, dibutyltin chloride dihydroxide (C 4 H 9 ) 2 Sn(OH) 2 Cl, butyltinhydroxide hydrate (C 4 H 9 )Sn(=O)OH. x H 2 O, Ni nanoparticles and Pd nanoparticles act as catalysts. Among these, 1 weight % of dibutyltin diacetate shows the maximum conversion. Then, methanolysis of sunflower oil, neem oil, rocket seed oil and linseed oil into methyl esters studied in the presence of 1% dibutyltin diacetate as a catalyst and was compared their percentage conversions. The experimental yield for the conversion of jojoba oil, sunflower oil, neem oil, rocket seed oil and linseed oil into biodiesel was found to be 71%, 51%, 50.78%, 40.90% and 39.66%, respectively. The experimental yield of the conversion of jojoba oil into methyl esters was found to be increased up to 96% by increasing reaction time, without emulsion formation. The synthesis of jojoba seed oil biodiesel (JSOB), soybean oil biodiesel (SOB), neem oil biodiesel (NOB), rocket seed oil biodiesel (RSOB) and linseed oil biodiesel (LSOB) was confirmed by NMR ( 1 H & 13 C) and FT-IR analyses of biodiesel.

Salicin-based phenolic glycosides(PGs) are important defensive substances against herbivore feeding and have good bioactivities. In this work, a novel approach for the synthesis of salicin-based PGs has been developed, by which PGs of 2′-O-acetylsalicin(5a), 3′-O-acetylsalicin(5b) and 3′-O-benzoylsalicin(5d) were hemisynthesized. The effects of acylation reagent, solvent and temperature on the regioselective acylation of 2′- or 3′-hydroxyl groups of salicin mediated by dibutyltin oxide were investigated. The optimal conditions under which the best regioselectivity reached for 5a–5d were discovered, respectively. Moreover, a tentative tin-oxygen coordination mechanism was put forward to explain the different regioselectivities shown under different conditions.

The trans-sialidase of Trypanosoma cruzi (TcTS) is a surface enzyme that modifies the parasite glycocalyx covering it with sialic acid. This process is essential to adhesion and invasion mechanisms in life cycle of the protozoan in the human host, making TcTS a very attractive molecular target for drug design. Using the TcTS substrate 3'-sialyllactose as prototype, D-galactose-derived potential inhibitors of TcTS were designed using strategies of molecular modification. Ten new aryl galactosides modified at carbon-3 were synthesized employing classical carbohydrate chemistry and dibutyltin oxide method for regioselective 3-O-alkylations and evaluated against TcTS by spectrofluorimetry. The 4-methoxycarbonyl-2-nitrophenyl 3-O-carboxymethyl-β-D-galactopyranoside was the most active compound inhibiting 21% of TcTS enzymatic activity at 1 mM.

The transesterification of jojoba oil with methanol has been studied in the presence of various catalysts i.e., sodium hydroxide (NaOH), potassium hydroxide (KOH), dibutyltin diacetate (C 4 H 9 ) 2 Sn (OOCCH 3 ) 2 , dioctyltin diacetate (C 8 H 17 ) 2 Sn (OOCCH 3 ) 2 , dibutyltin oxide (C 4 H 9 ) 2 SnO, dioctyltin oxide (C 8 H 17 ) 2 SnO, diphenyltin oxide (C 6 H 5 ) 2 SnO, monobutyltin chloride dihydroxide ((C 4 H 9 )Sn(OH) 2 Cl) and monobutyltin hydroxide oxide hydrate ((C 4 H 9 )Sn(=O)OH⋅ x H 2 O), with % age conversion of oil into biodiesel was 84.5%, 61.3%, 92.6%, 25.4%, 22.0%, 23.3%, 12.0%, 2.15% and 1.05%, respectively. The optimization of experimental parameters was established to achieve maximum yield of the product by using dibutyltin diacetate (C 4 H 9 ) 2 Sn (OOCCH 3 ) 2 . The physical and fuel properties of jojoba biodiesel like density, dynamic viscosity, kinematic viscosity, pour point, cloud point, flash point, and acid number were determined by ASTM procedures and were found to be comparable to ASTM standards for diesels. The synthesis of jojoba seed oil biodiesel (JSOB) was confirmed by FT-IR and NMR ( 1 H and 13 C) analyses of both oil and biodiesel. Chemical composition of fatty acid methyl esters (FAMEs) in jojoba biodiesel was established by GC–MS analysis and verified by retention time data and mass fragmentation pattern.

Two novel macrocyclic organotin(IV) carboxylates [(n-Bu2Sn)L1]2•C7H8 (1) (L1 = 2-(4-carboxyphenylcarbamoyl)benzoic acid) and [(n-Bu2Sn)L2]3•H2O (2) (L2 = 5-(1,3-dioxo-1,3-dihydro-isoindol-2-yl)-isophthalic acid) were generated by the reactions of dibutyltin oxide with amide dicarboxylic acids and characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy. X-ray crystallography diffraction analyses reveal that 1 is a di-nuclear dicarboxylate ring and 2 is a trinuclear tricarboxylate macrocycle. With the help of intermolecular interactions, 1 and 2 construct supramolecular 3D architectures filled with cavities. Free toluene and water molecules are located in the cavities of 1 and 2 respectively as guests. Thermal analyses suggest that complex 2 is thermally more stable than 1. The antitumour activity of 1 and 2 has also been studied.

The synthetic problems associated with melt polymerizations to form homopolyesters of isosorbide (ISB) and rigid diacids could potentially be solved by using catalyst systems with acetic anhydride (Ac2O). A catalyst consisting of dibutyltin oxide, germanium oxide, and Ac2O exhibited excellent performance characteristics in syntheses of a high-molecular-weight homopolyester of ISB and cis/trans-1,4-cyclohexanedicarboxylic acid (CHDA), also referred to as poly(isosorbide cis/trans-1,4-cyclohexanedicarboxylate) (PICD). The acetylation of ISB using Ac2O during esterification decreased the steric hindrance of ISB and accelerated the chain growth of PICD. Gel permeation chromatography data confirmed the formation of a high-molecular-weight PICD (71 100 weight-average molecular weight and 14 300 number-average molecular weight) using 0.02 mol of Ac2O. The glass transition temperature of PICD was almost 131 °C at 0.02 mol of Ac2O and decreased with increasing amounts of Ac2O due to the breaking of the rigid ring ...

A straightforward procedure is described for the synthesis of (16)-linked saccharides by regioselective glycosylation of unprotected glycosyl acceptors. Phenyl 1-thioglycopyranosides derived from D-glucose, D-galactose and D-mannose were treated with dibutyltin oxide to introduce a stannylene acetal, and then subjected to selective glycosylation at the 6-position with the Koenigs–Knorr protocol. Peracylated glycosyl bromides of D-glucose, D-galactose, D-mannose and D-glucosamine were employed as the donors to give the corresponding (16)-linked disaccharides in moderate to good yields. The best results were obtained with glycosyl donors and acceptors derived from D-glucose and D-galactose. Fully acylated disaccharide thioglycosides could also serve as glycosyl donors for the regioselective coupling. Brominolysis and subsequent Koenigs–Knorr coupling with the stannylene acetal of phenyl 1-thio-β-D-glucopyranoside gave rise to the corresponding (16)-linked trisaccharides in moderate yields.

Organotin oxide was used to catalyze the reaction between BPA (bisphenol A) and DMC (dimethyl carbonate), and Ph 2 SnO (diphenyltin oxide) displays the excellent catalytic performance in transesterification and O-methylation. However, Bu 2 SnO (dibutyltin oxide), (PhCH 2 ) 2 SnO (dibenzyltin oxide) and (C 6 H 11 ) 2 SnO (dicyclohexyltin oxide) exhibited weaker catalytic activity but higher selectivity for C-methylation product formation. The π–π function between Ph 2 SnO and BPA provided more chances for their interaction, and π–d interaction between phenyl ring and Sn resulted in catalyst having higher activity in transesterification and O-methylation. O-methylation product formation over Ph 2 SnO comes from transesterification product decomposition not from direct methylation of BPA with DMC.

Organotin-mediated regioselective protection has been extensively used in organic synthesis for many years. However, the mechanistic origin of the resulting regioselectivity is still not clear. By the comparison of the steric and stereoelectronic effects controlling the geometry of five-membered rings formed from neighboring group participation, from intramolecular acyl group migration, or from orthoester transesterification on pyranoside rings, a theory on the pattern resulting from the reaction with dibutyltin oxide is presented. It is thus suggested that the regioselectivity of organotin-mediated protection is controlled by analogous steric and stereoelectronic effects as in neighboring group participation and acyl group migration, mainly dependent on the stereoelectronic effects of the pyranoside itself, and not related to complex stannylene structures. An organotin protection mechanism is also suggested, emanating from steric and stereoelectronic effects, nucleophilicity, and organotin acyl migration.

The transesterification in acetylated konjac glucomannan/ethylene vinyl acetate (AKGM/EVA) melting blend system with the presence of dibutyltin oxide (DBTO) catalyst was investigated by means of a torque rheometer during compounding. The characteristics of the products were evaluated by DSC and FT-IR. The glass transition temperature at about 179.4 °C was found in the DSC curve of AKGM-EVA, the equilibrium torque of AKGM/EVA with 0.25 wt% DBTO was lower than that without DBTO. The results showed that the transesterification took place in the AKGM/EVA blend system.

Soybean oil-based alkyd resin was prepared using soy-based polyol, maleic anhydride and phthalic anhydride. The soy-based polyol was obtained through the epoxidization of soybean oil, followed by ring-opening with methanol and, the hydroxyl values of soybean oil-based polyols used in this reaction is 169.93 mgKOH/g. In the reactions of soy-based polyol, maleic anhydride and phthalic anhydride, the molar ratio of hydroxyl value is equal to carboxyl value and the molar ratio of maleic anhydride to phthalic anhydride is 2:1, 1:1 and 1:2, respectively. 1% hydroquinone based on total reactants was used as inhibitor of polymerization, 1% dibutyltin oxide was used as catalyst.

Dibutyltin oxide was used to catalyze the synthesis of oligo(glycerol-glutaric acid)s in the absence and presence of solvent. Reaction times were either 10 h or 24 h for reactions performed in DMF and 24 h for the neat reaction. The oligomers had an average yield of 84.6%. Gas chromatography (GC) was used to quantify amounts of unreacted glycerol and diacid. 13C NMR was used to identify branching patterns and determine the degree of branching (DB%), MALDI-TOF mass spectrometry was used to detect ions that were unique to branched species, and gel permeation chromatography (GPC), equipped with a light scattering detector, was used to determine molecular weight (Mn) and the polydispersity index (PDI). Themal stability was determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), while dynamic mechanical analysis (DMA) was used to determine the rheological properties of the products. The materials synthesized in solution had considerably lower average molecular weights (Mn, g/mol) of 1050 (10 h) and 1474 (24 h) but higher polydispersity indexes [PDI (Mw/Mn, where Mw = weight average molecular weight)] of 21.1 (10 h) and 30.5 (24 h), than the corresponding neat-derived material (Mn = 445 000; PDI= 5 8). Degrees of polymerization averaged 5.7 (10 h) and 8.8 (24 h) for the solvent-derived products compared to 2392.5 for products synthesized in the absence of solvent. Viscosity, glass transition temperature (Tg), change in heat capacity ( Cp), and molecular weight increased with reaction time and degrees of branching (DB%). Degrees of branching were lower for the solvent-derived materials [41% (10 h); 45% (24 h)] than observed for material synthesized in the absence of solvent (82%). DB% and Mn largely account for the drastic physical and mechanical differences observed among materials synthesized in solvent and solvent-less systems.

article i nfo Transesterification reaction of dimethyl carbonate with phenol to methylphenyl carbonate and diphenyl carbonate using dibutyltin oxide catalyst in conjunction with Bronsted and Lewis acidic ionic liquids was studied. It was observed that the use of ionic liquids significantly enhances the yield of diphenyl carbonate. The ionic liquid having p-toluenesulfonate as anion and metal halide (e.g. ZnCl2) as Lewis acid precursor exhibited higher activity and selectivity for diphenyl carbonate formation. Furthermore, the Bronsted and Lewis acidity of ionic liquids was measured by IR spectroscopy using pyridine as a probe and their Lewis acidity order was also determined.

The dibutyltin(IV) oxide complex reacts with 5-fluorouracil-l-propanonic or5-fluorouracil-1-acetic acid to give the potential antitumor activity complexes [(5-fluorouracil)-1-(CH2)mCOOSn(Bu-n)2]4O2[m = 1, (1); m = 2, (2)] which were determined by IR and 1H NMR. The crystal structure determination shows that complex 2 is a dimmer, in which two [(5-fluorouracil)-1-CH2CH2COOSn(Bu-n)2]2O units are linked by bridging oxygen atom, and the tin atoms adopt distorted trigonal bipyramids via two carbons from dibutyl group and three oxygen atoms from 5-fluorouracil and bridging oxygen. In vitro test shows complexes 1 and 2 exhibit high cytotoxicity against OVCAR-3 and PC-14.

Chelate tetra(acetylacetonato) tin (IV) was prepared and used as catalyst for polytrimethylene terephthalate synthesis. It exhibited higher catalytic activity than tetrabutyl titanate, butyltinhydroxide oxide and dibutyltin oxide. Decrease in reaction time, content of terminal carboxyl group, color intensity and increase in intrinsic viscosity were observed. The unique molecular structure can be considered as factor remarkably improving the catalytic activity of tetra(acetylacetonato) tin (IV).

The synthesis of the Sn(IV)-complexed, Schiff base derivatives 1a–1l, prepared in one pot by the reaction of 2-amino-4-R-phenol (R = H, Me, Cl, NO2), 2-pyridinecarboxaldehyde, 2-picolinic acid and dimethyl-, dibutyl-, and diphenyltin oxides, is described. The complexes were characterized by IR, MS, 1H, 13C, 119Sn NMR. Suitable crystals of 1e and 1h enabled us to use X-ray diffraction to determine their molecular structures, which exhibited pentagonal–bipyramidal geometries where the butyl groups occupied the axial positions whereas the nitrogen and the oxygen atoms occupied the equatorial positions. The reaction of the Schiff base 2 with dibutyltin oxide led to the pentacoordinated complex, 2h, through the addition of methanol to the C N bond. An unusual reduction–oxidation reaction took place by the reaction of 2-amino-4-nitro-phenol, dibutyltin oxide and 2-pyridinecarboxaldehyde, which produced the corresponding amine, 3h, and the amide, 4h, tin(IV) derivatives. Both structures were established by X-ray crystallography and exhibited a distorted, bipyramidal trigonal (BPT) geometry.

The synthesis of a series of (1,2-) mixed short/long-chain glycerophosphocholines has been performed. Starting from glycerophosphorylcholine (GPC), and using regioselective acylation in the presence of dibutyltin oxide, a set of high-purity isomeric mixed-chain phospholipids was obtained. This has allowed the development of a simple NMR method for the structural determination of the isomeric 1(2)-short-2(1)-long-diacylglycerophosphocholines. The method is based on the observation that selected protons in the two series of isomeric phospholipids undergo systematic chemical shift variations Δδ that can be ascribed to the acyl substituents on the glycerol backbone. The observed patterns can be exploited as a simple method for the discrimination of regioisomeric unsymmetrical 1,2-diacylglycerophosphocholines.

Dibutyltin oxide (Bu2SnO)n (3) reacts with methanol to give the tetrabutyl(dimethoxy)stannoxane dimer (4). The presence of 2,2-dimethoxypropane under a CO2 pressure accelerates the reaction resulting in nearly quantitative yield. Complex 4 exhibits catalytic activity as high as that of {Bu2Sn(OMe)2}2 (1) in the dimethyl carbonate (DMC) synthesis from CO2 and methanol. These results indicate that the conversion of 3 to 4 occurs under catalytic DMC production conditions.

A complete study on the catalytic activity of stannous oxalate for poly(trimethylene terephthalate) (PTT) synthesis via esterification method is carried out by comparison to the well known catalysts (tetrabutyl titanate (TBT), dibutyltin oxide (Bu2SnO), and stannous octoate (SOC)). Their catalytic activity in the esterification process is monitored by measuring the amount of water generated, while intrinsic viscosity (IV) and content of terminal carboxyl groups (CTCG) are used as the index in the polycondensation process. Stannous oxalate shows higher activity than the other catalysts. Decrease in reaction time and improvements in PTT property are observed. The higher catalytic activity of stannous oxalate is attributed to its chelate molecular structure.

Andrographolide glucopyranosides were synthesized from andrographolide and tetra-O-acetyl-β-D-gluco- pyranosyl bromide via a Koenigs-Knorr reaction and deacetylation with a moderate deacetylation reagent dibutyltin oxide in methanol for the first time. The structures of the andrographolide derivatives were confirmed by IR, NMR, and HRMS. Deprotection of the acetylated andrographolide glucopyranoside with dibutyltin oxide in methanol selectively removed all acetyl groups of the sugar moiety, whereas the acetyl group of the andrographolide part and the base- or acid-sensitive functional groups were retained.

Cyclodehydration of syn-triols (I) and (XII) give 3-hydroxytetrahydrofurans whereas the anti-isomers (III) and (XIV) favor monosulfonation under similar conditions.