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On-surface synthesis is a powerful method for the fabrication of π-conjugated nanomaterials. Herein, we demonstrate chemoselective Sonogashira coupling between (trimethylsilyl)ethynyl and chlorophenyl groups in silylethynyl- and chloro-substituted partially fluorinated phenylene ethynylenes (SiCPFPEs) on Ag(111). The desilylative Sonogashira coupling occurred with high chemoselectivity up to 75 %, while the competing Ullmann and desilylative Glaser homocoupling reactions were suppressed. A combination of bond-resolved scanning tunneling microscopy/atomic force microscopy (STM/AFM) and DFT calculations revealed that the oligomers were obtained by the formation of intermolecular silylene tethers (-Me2 Si-) through CH3 -Si bond activation at 130 °C and subsequent elimination of the tethers at an elevated temperature of 200 °C.

The Sonogashira coupling of 1,3,6,8-tetrabromopyrene with 4-[(–)-β-citronellyloxy]phenylethyne was employed to synthesize 1,3,6,8-tetra[4-(citronellyloxy)phenylethynyl]pyrene. The pyrene derivative catalyzed the reductive desulfonylation of ethenyl sulfones via visible-light irradiation (514 nm green light-emitting diodes) in the presence of i-Pr2NEt. The β-citronellyloxy groups provided the sufficient solubility to the highly π-expanded pyrene catalyst, and their polar oxygen functionalities enabled the easy separation of the catalyst from the products via column chromatography.

Diarylethenes were obtained from the corresponding ethenyl sulfones by photocatalyzed desulfonylation using UV or blue LEDs. When perylene and i-Pr2NEt were used as a photocatalyst and a sacrificin...

We have developed a novel diastereoselective iron-catalyzed cross-coupling reaction of various glycosyl halides with aryl metal reagents for the efficient synthesis of aryl C-glycosides, which are of significant pharmaceutical interest due to their biological activities and resistance toward metabolic degradation. A variety of aryl, heteroaryl, and vinyl metal reagents can be cross-coupled with glycosyl halides in high yields in the presence of a well-defined iron complex, composed of iron(II) chloride and a bulky bisphosphine ligand, TMS-SciOPP. The chemoselective nature of the reaction allows the use of synthetically versatile acetyl-protected glycosyl donors and the incorporation of various functional groups on the aryl moieties, producing a diverse array of aryl C-glycosides, including Canagliflozin, an inhibitor of sodium-glucose cotransporter 2 (SGLT2), and a prevailing diabetes drug. The cross-coupling reaction proceeds via generation and stereoselective trapping of glycosyl radical intermediates, representing a rare example of highly stereoselective carbon-carbon bond formation based on iron catalysis. Radical probe experiments using 3,4,6-tri-O-acetyl-2-O-allyl-α-d-glucopyranosyl bromide (8) and 6-bromo-1-hexene (10) confirm the generation and intermediacy of the corresponding glycosyl radicals. Density functional theory (DFT) calculations reveal that the observed anomeric diastereoselectivity is attributable to the relative stability of the conformers of glycosyl radical intermediates. The present cross-coupling reaction demonstrates the potential of iron-catalyzed stereo- and chemoselective carbon-carbon bond formation in the synthesis of bioactive compounds of certain structural complexity.

A new synthetic protocol of 1-arylpropyne was developed by taking advantage of 1-(diphenylphosphoryl)propyne as propyne equivalent in Sonogashira coupling: consecutive subjection of phosphorylpropyne to t-BuOK and to aryl halides in the presence of Pd and Cu catalysts afforded the corresponding 1-arylpropynes. The following olefination of the 1-arylpropyne with aldehyde provided the corresponding diarylenyne. When the enynes thus obtained were irradiated with UV light, they showed strong emission in organic solvents and in the solid states. In solution, Ph2N-substituted enynes exhibited remarkable solvatofluorochromism, and Lippert–Mataga plot analysis demonstrated that they undergo the larger polarization in the excited states than in the ground states.

Ph2P(O)-protected ethynes were successfully transformed to arylethynes in one-pot manner through t-BuOK-catalyzed deprotection followed by Sonogashira coupling with aryl halide. The arylethynes were obtained similarly by Ph2P(O)-deprotection, stannylation of the resulting terminal ethynes, and Migita-Kosugi-Stille coupling. Deprotection followed by intramolecular Eglinton coupling could be carried out in one-pot to provide cyclic butadiynes.

9,10-Bis(phenylethynyl)anthracene (BPEA) derivatives were synthesized from 10-bromo-9-anthracenecarbaldehyde by stepwise Sonogashira coupling with phenylethynes and the one-shot double-elimination reaction with benzyl phenyl sulfones. Those two reactions could be integrated in a one-pot process to give unsymmetrically substituted BPEA derivatives in good yields by simple operations. This integrated process was applied to the synthesis of an extended BPEA derivative having an extra phenylethynyl group. The photophysical properties of the BPEA derivatives were investigated by UV/Vis and fluorescence spectroscopy.

Fluorous distannoxanes (XR f 2 SnOSnR f 2 X) 2 ·nH 2 O (R f =C 6 F 13 C 2 H 4 ) (1: X= C 8 F 17 SO 3 , n=10; 4: X=Cl, n=0) (1) catalyze the Mukaiyama aldol reaction and the allylation of aldehydes with tetraallyltin at room temperature in fluorous/organic biphasic solvent systems, in which the reactions proceed more rapidly than in a single organic or fluorous solvent. Due to the unique surface activity of 1, the catalyst, organic substrate(s), and reagent(s) are distributed in both organic and fluorous phases to facilitate smooth reactions. Upon dilution with toluene after the reaction, the catalyst concentrates to the fluorous phase, while the organic substances migrate to the organic phase to effect facile catalyst recovery and recycling. By virtue of such a unique solvophilicity, a new version of fluorous biphase technology has been developed.

Zirconocene and titanocene bis(perfluorooctanesulfonate)s were synthesized. In contrast to the corresponding triflates and perchlorates, these compounds are air- and water-stable. They were proved to be ionic on the basis of conductivity measurements and X-ray analysis, allowing these complexes to be stored for months. The strong Lewis acidity of these cationic metallocene species, which was proved by ESR study, enabled catalytic glycosylation.

The local structure of tungsten species in tungsten–zirconium–oxide catalysts (WOxZrO2) was first investigated by W K-edge x-ray absorption spectroscopic techniques. A proportion of WO4 to the total WOx species was quantitatively analyzed with W L1-edge x-ray absorption near edge structure (XANES). Tungsten species in 15 wt% WOxZrO2, which is the most active for n-butane skeletal isomerization, consists of a mixture of WO3ZrO2 solid solution, WO6 aggregate and WO4 species on the catalyst surface. The tungsten species does not possess long-range ordering. Copyright © 2008 John Wiley & Sons, Ltd.

The high atom efficiency was achieved through addition of Ac2O in the Sc(OTf)3-catalyzed allylation of aldehyde with tetraallytin in a 4 : 1 molar ratio.

The synthesis of a variety of organotin compounds with 1H, 1H, 2H, 2H-perfluorooctyl groups is reported, together with an improved method for the corresponding distannoxane. Unique properties of this compound are disclosed in terms of fluorophilicity and activity as a Lewis acid catalyst in comparison with other mono-nuclear derivatives. A new criterion for obtaining high solubility in fluorocarbon solvents is presented. Copyright © 2003 John Wiley & Sons, Ltd.

Highly strained cyclic acetylenes 5,6,11,12-tetradehydrodibenzo[a,e]cyclooctenes (Sondheimer–Wong diynes) having various substituents on their benzene rings were synthesized successfully by one-pot treatment of the corresponding formyl sulfones with diethyl chlorophosphate/lithium hexamethyldisilazide (LiHMDS) and then lithium diisopropylamide (LDA). When mixtures of two types of formyl sulfones bearing different substituents were subjected to this protocol, the unsymmetrically substituted Sondheimer–Wong diynes could be synthesized in a stepwise manner by isolation of the heterocoupled vinyl sulfone intermediates followed by their treatment with LDA. The UV–vis absorption spectra and cyclic voltammograms of the substituted Sondheimer–Wong diynes were recorded. The electronic effect of substituents on the diynes was investigated in their click reactions and nucleophilic and electrophilic additions.

Ph2P(O)-protected ethynes were successfully transformed to arylethynes in one-pot manner through t-BuOK-catalyzed deprotection followed by Sonogashira coupling with aryl halide. The arylethynes were obtained similarly by Ph2P(O)-deprotection, stannylation of the resulting terminal ethynes, and Migita-Kosugi-Stille coupling. Deprotection followed by intramolecular Eglinton coupling could be carried out in one-pot to provide cyclic butadiynes.

A variety of reactions which are commonly used in synthetic chemistry are feasible with the automated synthesizer (MEDLEY). Air-sensitive organolithium and Grignard reagents as well as transition metal catalysts like Ni(0) and Pd(0) species are employable. The precise control of both the reaction temperature and the amount of added reagents enables to examine the dependence of chemical yields on the reaction temperature. Since the order of reagent addition is programmed and the reaction temperature is quickly tunable, sequential reactions can be conducted smoothly. An advanced control system was incorporated which allows a task to start immediately after the preceding one has finished. Owing to this function, the time for completing the multistep process can be minimized.

The effectiveness of cationic species for increasing the catalytic activity of organotin Lewis acids has been assessed by comparing two types of cationic organotin clusters, [Bu2Sn(OH)(H2O)]22+2OTf- and [(BuSn)12O14(OH)6]2+Cl-2·2H2O, with neutral clusters in alcohol acetylation. The Sn2 dication is extremely active, with a catalyst concentration of 0.001 mol %, sufficient to give a quantitative yield. The Sn12 dication is slightly less active but gives high levels of chemoselectivity and primary/secondary alcohols selection. The neutral clusters are less effective catalysts. A variety of synthetic applications are feasible by changing the Lewis acidity of the catalysts.

A variety of aromatic hydrocarbons bearing multiple alkyl substituents are accessible with perfect regiocontrol in a one-pot reaction starting from cyclohexenones and their aromatic analogues [Eq. (1)]. The present methodology can be further extended to the synthesis of polycyclic aromatic hydrocarbons. The drawbacks encountered in the Friedel-Crafts reaction are resolved since the reaction proceeds under basic conditions.

Distannoxane catalysts effect acylation of alcohols by action of esters and acetic anhydride. In particular, use of enol esters provides an extremely useful method. Primary alcohols are acylated in preference to secondary ones as well as phenol. Both acid- and base-sensitive functional groups remain intact. Especially unique is the discrimination of thio function which is completely tolerant under the present reaction conditions. This method is highly practical since operation is quite simple. Esters and solvents can be used without purification and no inert atmosphere is necessary. The products can be isolated simply by column chromatography or distillation without aqueous workup.

The reaction of α , ω -bis(organodichlorostannyl)alkanes [R(Cl 2 )SnCH 2 ] 2 Z with their corresponding organotin oxides [R(O)SnCH 2 ] 2 Z or ( t -Bu 2 SnO) 3 provides the new spacer-bridged tetraorganodistannoxanes {[R(Cl)SnCH 2 ] 2 Z]O} n ( 22 , Z=CH 2 , R=Me 3 SiCH 2 ; 23 , Z=CH 2 , R=Me 3 CCH 2 ; 24 , Z=CH 2 CH 2 , R=Me 3 SiCH 2 ; 25 , Z=CH 2 CH 2 , R=Me 3 CCH 2 ; 26 , Z=CH 2 CH 2 , R=Me 2 CHCH 2 ; 27 , Z=Me 2 Si, R=Me 3 SiCH 2 ). The acetate substituted derivative 28 {[R(AcO)SnCH 2 ] 2 CH 2 ]O} n (R=Me 3 SiCH 2 ) is obtained by reaction of 22 with silver acetate or by treatment of the organotin oxide [R(O)SnCH 2 ] 2 CH 2 (R=Me 3 SiCH 2 ) with acetic acid. The crystal structures of 23 , 24 , and 28 are described and reveal that these compounds adopt double ladder structures. Depending on the identity of Z and R in chloroform solution the compounds are either dimers ( n =2, 25 – 28 ) or tetramers ( n =4, 22 – 24 ). Also reported are preliminary studies on the catalytic activity in acylation reactions of compounds 22 , 24 – 26 , and 28 .

Depending on the identity of Z and R the reaction of the spacer bridged tetrachloroditin compounds [R(Cl2)SnCH2]2Z with (t-Bu2SnO)3 or their corresponding organotin oxides {[R(O)SnCH2]2Z} n provides either double ladders {{[R(Cl)SnCH2]2Z}O}4 (Z = CH2; R = CH2SiMe3, CH2CMe3), dimeric tetraorganodistannoxanes { {[R(Cl)SnCH2]2Z}O}2 (Z = Si(Me2), Si(Me2)CzCSi(Me2), Si(Me2)OSi(Me2); R = CH2SiMe3), or mixtures of both of these structures (Z = CH2CH2; R = CH2SiMe3, CH2CMe3, CH2CHMe2). The chlorine atoms can be replaced stepwise by other electronegative groups such as hydroxide or acetate. Preliminary studies on the catalytic activity of some tetraorganodistannoxanes with alkylidene spacers are reported.

Acetylation of alcohols with an equivalent amount of acetic anhydride is feasible in the presence of fluorous distannoxane catalyst in heterogeneous single fluorous system. The fluorous layer containing catalyst can be recycled and reused at least 10 times.

Incorporation of perfluorooctanesulfonate groups at 1,3-positions provides a cationic distannoxane which is acidic enough to catalyze efficient carbon−carbon bond forming reactions for the first ti...

The cationic palladium(II) aquo hydride, trans-(Cy 3 P) 2 Pd(H)(H 2 O) + BF 4 - > is an excellent catalyst for the carbonylation of alkynols to dienoic acids and esters and of alkynediols to cross-conjugated diesters

Distannoxane catalysts effect acylation of alcohols by action of esters and acetic anhydride. In particular, use of enol esters provides an extremely useful method. Primary alcohols are acylated in preference to secondary ones as well as phenol. Both acid- and base-sensitive functional groups remain intact. Especially unique is the discrimination of thio function which is completely tolerant under the present reaction conditions. This method is highly practical since operation is quite simple. Esters and solvents can be used without purification and no inert atmosphere is necessary. The products can be isolated simply by column chromatography or distillation without aqueous workup.

Depending on the identity of Z and R the reaction of the spacer bridged tetrachloroditin compounds [R(Cl2)SnCH2]2Z with (t-Bu2SnO)3 or their corresponding organotin oxides {[R(O)SnCH2]2Z} n provides either double ladders {{[R(Cl)SnCH2]2Z}O}4 (Z = CH2; R = CH2SiMe3, CH2CMe3), dimeric tetraorganodistannoxanes { {[R(Cl)SnCH2]2Z}O}2 (Z = Si(Me2), Si(Me2)CzCSi(Me2), Si(Me2)OSi(Me2); R = CH2SiMe3), or mixtures of both of these structures (Z = CH2CH2; R = CH2SiMe3, CH2CMe3, CH2CHMe2). The chlorine atoms can be replaced stepwise by other electronegative groups such as hydroxide or acetate. Preliminary studies on the catalytic activity of some tetraorganodistannoxanes with alkylidene spacers are reported.

A distannoxane catalyst effects exclusive acetylation of the primary alcohol of 3-chloropropane-1,2-diol. This reaction provides a convenient access to enantiopure epichlorohydrin.

Deprotection of acetyl esters is effected cleanly by the neutral organotin catalyst, [tBu2SnOH(Cl)]2. The mildness of the reaction gives rise to great synthetic versatility and in the process a variety of functional groups are tolerated. Differentiations between primary, secondary, and tertiary alcohols and between acetyl ester and other esters are feasible. No racemization occurs with chiral acetyl esters. Exclusive deprotection of primary acetyl esters in carbohydrates and nucleosides is observed. The crude product thus obtained can be used for further reactions without purification.

Bi(OTf)(3)-catalyzed acylation of alcohols with acid anhydride was evaluated in comparison with other acylation methods. The Bi(OTf)(3)/acid anhydride protocol was so powerful that sterically demanding or tertiary alcohols could be acylated smoothly. Less reactive acylation reagents such as benzoic and pivalic anhydride are also activated by this catalysis. In these cases, a new technology was developed in order to overcome difficulty in separation of the acylated product from the remaining acylating reagent: methanolysis of the unreacted anhydride into easily separable methyl ester realized quite easy separation of the desired acylation product. The Bi(OTf)(3)/acid anhydride protocol was applicable to a wide spectrum of alcohols bearing various functionalities. Acid-labile THP- or TBS-protected alcohol, furfuryl alcohol, and geraniol could be acylated as well as base-labile alcohols. Even acylation of functionalized tertiary alcohols was effected at room temperature.

Novel, practical protocols of transesterification have been advanced with recourse to fluorous biphase technology. The fluoroalkyldistannoxane catalysts enable transesterification in FC-72 solvent to furnish 100% yields of the desired esters by use of reactants ester and alcohol in a 1 : 1 ratio. The catalysts also work in FC-72/organic solvent system as well as in toluene alone. A number of esters and alcohols bearing various functional groups are employable. The catalysts can be totally recovered and reused. More conveniently, the catalyst solution in FC-72 which is separated from the reaction mixture is directly used for the next reaction.

Nucleophilic addition of RLi to a triple bond of dibenzocycloocta[a,e]diyne provides dibenzo[b,f]pentalene motif through trans-annulation of the resulting vinyllithium. Dibenzopentalene anion thus ...

A distannoxane catalyst effects exclusive acetylation of the primary alcohol of 3-chloropropane-1,2-diol. This reaction provides a convenient access to enantiopure epichlorohydrin.

Novel organotin cations, [R2SnOH(H2O)]22+(OTf)-2 (R = n-Bu and t-Bu), were prepared from R2SnO and CF3SO3H (TfOH). The synthetic utility of these compounds due to the increased Lewis acidity was exemplified by their high catalytic activity in the acetylation of alcohols.

Several types of organic reactions were accelerated by immediate evaporation of solvents because of remarkable enhancement of molecule-to-molecule contacts between reactants.

The double elimination reaction of β-substituted sulfones offers a versatile strategy for synthesis of arylene ethynylene kits containing heteroaromatic rings. A sequence of aldol reaction between α-sulfonyl carbanion and aldehyde, trapping the resulting aldolate to give β-substituted sulfone, and double elimination of this intermediate can be integrated in one pot. This protocol allows thiophene, pyridine, and ferrocene units to be accommodated in phenylene ethynylene arrays.Key words: arylene–ethynylenes, heteroaromatic rings, ferrocene, double elimination, sulfones.

The reactions of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane and dialkyltin dihalides with silver perfluorooctanesulfonate provided the corresponding sulfonates as hydrates. The number of water molecules (n) of hydration was dependent on the conditions. The distannoxane derivative was identified as n from 0.5 to 6, while in the hydrated mononuclear species and DMSO complexes n varied widely from 4 to 13. 119Sn NMR spectroscopy and conductivity measurements indicated the ionic dissociation of these compounds in solution. These compounds exhibited unusually high solubility in polar organic solvents. The ionic dissociation together with facile hydration probably causes the unusual solubility. The Lewis acidity of these compounds was found to be high among organotin derivatives on the basis of ESR spectra of superoxide/metal-ion complexes. In contrast to well-known organotin triflates, these compounds suffered no hydrolysis upon storage in open air. The high catalytic activity of the distannoxane 1 was exemplified for various carbon-carbon bond-forming reactions, such as Mukaiyama-aldol as well as -Michael reactions and allylation of aldehydes.

Acetylation of alcohols with an equivalent amount of acetic anhydride is feasible in the presence of fluorous distannoxane catalyst in heterogeneous single fluorous system. The fluorous layer containing catalyst can be recycled and reused at least 10 times.

Pyridine-containing arylene ethynylene strands were connected to the 2- and 2'-positions of (R)- and (S)-1,1'-binaphthyl templates. The arylene ethynylene moieties underwent intramolecular coordination with Ag(I) or Cu(I) ion to afford enantiopure double helicates. The double-helical structure was elucidated on the basis of circular dichroic (CD) spectra. The importance of intramolecular complexation of the double strands for the helicate formation was confirmed by comparison with a ligand bearing a single strand. Connection of the strands through an ether linkage enabled a sorting out of the Cotton effect induced by double-helical arylene ethynylene moieties. The CD exciton chirality method unambiguously proved that the termini of the strands approach each other upon complexation and that the sense of the induced helicity is the same as predicted by molecular modeling.

In contrast to conventional substrate selectivity in Lewis-acid promoted nucleophilic reactions wherein less electrophilic aldehydes react preferentially over the more electrophilic counterparts, addition of tetraallyltin to aldehydes occurs in a reversed sense. The substrate selectivity in Lewis acid-promoted nucleophilic addition is generally dependent on the combinations of substrates, nucleophiles, catalysts, etc. Such diversity leads to two one-pot protocols, parallel recognition and shotgun process wherein different chemical transformations take place directly on the separate reaction sites without recourse to protection–deprotection procedures. These two protocols are tunable by controlling the electronic properties of the substrates.

Bi(OTf)(3)-catalyzed acylation of alcohols with acid anhydride was evaluated in comparison with other acylation methods. The Bi(OTf)(3)/acid anhydride protocol was so powerful that sterically demanding or tertiary alcohols could be acylated smoothly. Less reactive acylation reagents such as benzoic and pivalic anhydride are also activated by this catalysis. In these cases, a new technology was developed in order to overcome difficulty in separation of the acylated product from the remaining acylating reagent: methanolysis of the unreacted anhydride into easily separable methyl ester realized quite easy separation of the desired acylation product. The Bi(OTf)(3)/acid anhydride protocol was applicable to a wide spectrum of alcohols bearing various functionalities. Acid-labile THP- or TBS-protected alcohol, furfuryl alcohol, and geraniol could be acylated as well as base-labile alcohols. Even acylation of functionalized tertiary alcohols was effected at room temperature.

Deprotection of acetyl esters is effected cleanly by the neutral organotin catalyst, [tBu2SnOH(Cl)]2. The mildness of the reaction gives rise to great synthetic versatility and in the process a variety of functional groups are tolerated. Differentiations between primary, secondary, and tertiary alcohols and between acetyl ester and other esters are feasible. No racemization occurs with chiral acetyl esters. Exclusive deprotection of primary acetyl esters in carbohydrates and nucleosides is observed. The crude product thus obtained can be used for further reactions without purification.