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In this study, a new stereospecific strategy for the preparation of C 8 N aminocyclohexenols such as C 7 N, validamine analogs were developed from starting compound 4 via intramolecular aza -michael β -amination reaction between α , β -unsaturated ketones and ammonia in methanol. The strategy was to produce C 8 N derivatives such as validamine C 7 N via Kornblum-DeLaMare rearrangement, which involves stereocontrolled amination of a double bond, esterification, carbonyl group reduction, benzofuran ring opening, ammonolysis of acetate groups. The mechanism of target molecules is discussed. Pseudosugars with different configurations containing an amino group at the anomeric position were tested against α -glucosidase, β -glucosidase, and α -amylase. Among these compounds, compound 12 against α -glucosidase, compound 14 against β -glucosidase, and compound 21 against α -amylase exhibited the best activity compared to acarbose. Moreover, enzyme kinetic studies to understand the enzyme inhibition mechanism and DFT studies to investigate binding interactions with enzyme active sites were performed on these compounds (12 , 14 , and 21). Additionally, the pharmacokinetic parameters (ADME) were examined using the QikProp module to determine their potential as drug candidates. [Display omitted] • Catalyst-free C–N bond production by β -Michael addition. • Compared to acarbose, compounds 12 and 14 exhibited the best activity against (α-, β-) glucosidase, and 21 against α-amylase. • Compounds 12 and 14 meet the parameters specified in Lipinski's rule of five. [ABSTRACT FROM AUTHOR]

Arylamines play a key role in the synthesis of agricultural chemicals, dyes, medicine, rubber and other fine chemicals. The hydrogenation of aromatic nitro is the most convenient protocol for the preparation of arylamines. Therefore, it is of great research significance to develop a stable, efficient and low-cost catalyst in the hydrogenation of nitro compounds. Therefore, the supported single-atom platinum Pt 1 /V 2 O 5 (0.1 wt% of Pt by ICP−OES) was prepared for the efficient hydrogenation of variety of aromatic nitros. The Pt 1 /V 2 O 5 was characterized by SEM, TEM, HAADF−STEM, XRD, XPS, Raman and CO−DRIFT analysis. Amount of aromatic nitros with functional groups (such as CN and carbonyl groups) were hydrogenated smoothly to deliver the amines in 50–95 % yields. The catalytic performances are attributed to the electronic metal−support interactions between Pt 1 atoms and V 2 O 5 with the abundant surface oxygen vacancy, resulting in the enhanced electronic density of Pt 1 atoms, which were confirmed by the results of XPS and Raman spectra. The high activity and reusability of Pt 1 /V 2 O 5 catalyst imply its potential application in fine chemical synthesis. [Display omitted] • Developing a highly efficient Pt 1 /V 2 O 5 based on oxygen vacancy from nano-V 2 O 5. • Strong electronic metal-support interactions (EMSI) exists between Pt and nano-V 2 O nanorods. • EMSI enhancing the Pt 1 /V 2 O 5 performance for specific reaction. • Effective in hydrogenation of nitros by Pt 1 /V 2 O 5 at mild conditions. [ABSTRACT FROM AUTHOR]

Abstract Herein, we present a full account of our studies with respect to the reactivity of insufficiently explored 1λ6-isothiazolidine-1,1,4-triones (so-called β-keto-γ-sultams). This heterocyclic system possesses two reaction centers: the EWG-activated methylene group and the carbonyl moiety which were investigated in the course of present study. 2,3,3-Trimethyl-1λ6-isothiazolidine-1,1,4-trione and 4-methyl-5λ6-thia-4-azaspiro[2.4]heptane-5,5,7-trione were chosen as representatives of the given class of substances. The former is a classical spatially uncomplicated model substance, the latter bearing a spiranic cyclopropane substituent is interesting in terms of evaluation of strain cycle effects. Indeed, the data obtained convey information about the impact of the highly strained substituent on the reaction centers of the ketosultam core. Thus, in addition to less stability of the strained spiranic ketosultam, the reactivity of its carbonyl group is suppressed whereas the activity of the methylene group is enhanced being compared with the nonspiranic substrate. Apart from the difference in the chemical character of the given β-keto-γ-sultams we faced unprecedented products (1,1-dioxo-5-[2-(triphenylphosphonio)acetyl]-2,3-dihydro-1 H -1λ6-isothiazol-4-olates) formed during the course of the reaction with the Wittig reagent triphenylcarbethoxymethylenephosphorane. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Rhodium(I)-catalyzed intermolecular cycloadditions of alkynes with vinyl aziridines bearing a conjugated carbonyl group in the olefin moiety followed by the double migration resulted in the formation of pyrrole derivatives in a one pot fashion. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

The oxidation of both N -substituted hydroxylactams and isoindolinones to the corresponding phthalimides using catalytic iron/ tert -butylhydroperoxide (TBHP) reagent systems is detailed. The 2-substituted-3-hydroxyisoindolin-1-one (hydroxylactam) to imide oxidation constitutes a rather straightforward hydroxyl → carbonyl group conversion while the latter process is a methylene → carbonyl transformation. The iron oxidant Fe (TFA) 3 (10 mol%), prepared by the treatment of iron (III) chloride with trifluoroacetic acid, is used in conjunction with TBHP (one equivalent). For the hydroxylactam substrates, the oxidation system was effective in providing the corresponding phthalimides in isolated yields ranging from 41 to 88% within a reaction time of 24 h. For the N-substituted isoindolinone to phthalimide conversions, the imide products were obtained in isolated yields of 53–96% while using the same catalyst/oxidant system. For comparison, oxidations were run with catalytic iron (III) chloride (10 mol%) and TBHP and the yields were comparable to the reactions using the trifluoroacetate-based reagent. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract A convergent approach for the synthesis of diverse N -heterocycles is described. The reaction involves trapping of diazo-derived rhodium carbenoids with gold activated aminoalkynes, and accommodates both the donor/acceptor (D/A) as well as acceptor/acceptor (A/A) diazo carbonyls. Mechanistic investigations indicate that the Rh(II)/Au(I) catalyzed reaction of aminoalkynes with D/A diazos is concerted, while the reaction with A/A diazo is stepwise and proceeds with carbene N–H insertion and a subsequent Conia-ene cyclization. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

An iodine-promoted fragment assembly strategy for the synthesis of fused heterocycles has been established. It provides an efficient route to construct pyrazolone-oxepine-pyrazoles from phenylhydrazines, aryl methyl ketones and acetoacetate esters. Notably, acetoacetate esters play two distinct pivotal roles in the five-component reaction by realizing the unique reactivities of methyl, methylene and carbonyl groups to construct 3-methyl-5-pyrazolone skeletons and by the reaction of methyl and carbonyl groups to form a C (sp3)-O bond. [ABSTRACT FROM AUTHOR]

In the present work, we synthesised a functionalised calix[4]arene with 5,11-di(N-methyl-E-(4-pyridylethylene) moiety (CX[4]), and investigated interactions of it with HemiMeQ[6], HemiMeQ[7], and Q[8]) in both water and DMSO using fluorescence spectrophotometry and 1 H NMR spectroscopy. Titration 1 H NMR spectra revealed that Q[ n ]s prefers to include the N-methyl-E-(4-pyridylethylene) moiety. In particular, the interaction of CX[4] with Q[8] in water resulted in intense fluorescence emission, and this interaction system can respond to compounds such as amantadine. [ABSTRACT FROM AUTHOR]

Asymmetric hydrogenation and transfer hydrogenation of ketones are efficient and direct methods allowing access to enantiomerically enriched secondary alcohols, and have been widely studied and applied in both academia and industry. While the asymmetric (transfer) hydrogenation of ketones having one carbonyl group has been extensively investigated, the related study on ketones bearing multiple carbonyl groups such as diketones is still relatively underdeveloped. Due to the challenge of regioselectivity control raised by multiple reactive sites, and the difficulty of stereoselectivity control caused by several potential coordination groups, multiple carbonyl substrates are more difficult to be hydrogenated in a highly regio- and stereoselective manner. Nonetheless, significant progress has been achieved in the past several decades. This review summarizes the related investigations and illustrates the influences of catalysts, substrates, temperatures, solvents, and reaction times on the regio- and stereoselectivities of the reactions. The asymmetric hydrogenation and transfer hydrogenation of substrates with multiple carbonyl groups especially diketones are summarized. The factors influencing the regio- and stereoselectivities are discussed, which will be instructive for new reaction design to address the challenging research topic. [Display omitted] [ABSTRACT FROM AUTHOR]

Oxindole derivatives are of growing importance in organic synthesis and in the synthesis of biologically active compounds, therefore, a very important goal is to develop new ways of modifying such scaffold. In this article we proposed a general approach to synthesis of oxindole-based amide-substituted compounds, which includes usage of protecting group. To stabilize the key-molecule for further modifications – amino-isatin, the carbonyl group in the 3-position of the starting nitro-isatin was protected by ketal synthesis. Next, the reduction of nitro-group and further modification of amino-group was carried out. The proposed strategy allows us to obtain mono- and diamido-substituted isatins. The possibility of their modification in the 3-position for synthesis of potent biologically active compounds is demonstrated. [ABSTRACT FROM AUTHOR]

Using (trifluoromethyl)trimethylsilane (TMSCF 3 ) as the trifluoromethylating agent, MgCl 2 -catalyzed trifluoromethylation of carbonyl compounds proceeded readily at room temperature. In the presence of 10 mol% of MgCl 2 , a variety of carbonyl substrates such as aliphatic/aromatic aldehydes, acyclic/cyclic ketones and esters could be trifluoromethylated in DMF, giving the corresponding trimethylsilyl ethers (ketals) in up to 93% isolated yields. Trifluoromethylketones could be readily obtained after hydrolysis of the trimethylsilyl ketals. The reactions could tolerate air and moisture, and the use of oxygen and moisture-free conditions was not required. [ABSTRACT FROM AUTHOR]

Molecular structure of N-trifluoroacetylpiperidine ( NFAPi ) was studied by synchronous gas-phase electron diffraction/mass spectrometry (GED/MS), IR spectroscopy and quantum chemical (QC) calculations. Due to the influence of strong conjugation between the electron lone pair on the nitrogen atom and the double bond of the carbonyl group, NFAPi may exist as only one conformer, in which the trifluoroacetyl group is located in an intermediate, between axial and equatorial, position. Nine atoms (two C α atoms along with their H eq atoms, the nitrogen atom, the carbonyl group and one CF fragment of the trifluoromethyl group) form a single plane. In contrast, partition of the conjugation between the double C O bond and the two lone pairs leads to coexisting intermediate and axial, in 1-piperidinecarboxamide, and axial and equatorial forms in N , N -dimethyl-1-piperidinecarboxamide and 1,1′-carbonyldipiperidine. The conformational ratio for the latter ones is Eq : Ax ≈50:50%. The steric effect and conjugation stabilize the axial conformer. [ABSTRACT FROM AUTHOR]

In order to clarify the importance of the C-3 carbonyl group to the cytotoxicity observed for discorhabdin marine alkaloids a number of semi-synthetic analogues of discorhabdin P were prepared. C-3 Reduction and acetylation typically resulted in a 4- to 10-fold reduction in cytotoxic potency (P388 cell line) compared to the corresponding keto parent compound. X-ray crystallography of a C-3 dienol derivative of discorhabdin P ( 6 ) allowed assignment of (3 r , 6 r ) pseudoasymmetric configuration to the natural product 3-dihydrodiscorhabdin C ( 5 ). Analogues incorporating increasingly bulky substitution at C-3 only retained cytotoxicity if they bore (3 s , 6 s )-configuration at the spiro-dienol moiety. A variety of fluorophore-labelled probes were prepared of which only a dansyl analogue ( 14 ) exhibited (modest) cytotoxicity. [ABSTRACT FROM AUTHOR]

Several Gold's reagents were synthesized from cyanuric chloride and N,N -dialkylformamides. These synthetic equivalents of N,N -dimethylformamide dimethyl acetal were used in an optimized and scalable procedure for the regioselective synthesis of a variety of enaminones from ketone starting materials, whose utility was demonstrated by the stereoselective synthesis of Rawal-type dienes. [ABSTRACT FROM AUTHOR]

A series of novel tricyclic pyrimidine-fused 1,5-benzodiazepines (PFBZDs) was synthesized using an enaminone-based approach. The key step in the synthetic strategy involves the formation of the C C NMe 2 structure on vicinal carbonyl groups of the 1 H -1,5-benzodiazepine-2,4(3 H ,5 H )-dione (BZD). The synthesis of pyrimidine-fused 1,5-benzodiazepines was performed by a simple and efficient method in good to excellent yields under mild and green conditions. The β -enaminoamide intermediates were condensed with thiourea and guanidine derivatives to form the corresponding tricyclic PFBZDs. But reaction of aminoguanidine, thiosemicarbazide, 4-phenylthiosemicarbazide and ethane-1,2-diamine with β -enaminoamides didn't produce any desired product and led to recovery of the corresponding starting BZD. [ABSTRACT FROM AUTHOR]

Parikh–Doering oxidation of diethyl 9-hydroxy-2,6-dimethyl-4,8-dihydro-4,8-methanopyrrol[3,4- f ]isoindole-1,7-dicarboxylate produced diethyl 9-oxo-2,6-dimethyl-4,8-dihydro-4,8-methanopyrrol[3,4- f ]isoindole-1,7-dicarboxylate. This carbonyl derivative spontaneously underwent cheletropic extrusion of carbon monoxide, producing diethyl 2,6-dimethylpyrrol[3,4- f ]isoindole-1,7-dicarboxylate, which showed 14π-electronic aromaticity on the whole five-six-five ring system. [ABSTRACT FROM AUTHOR]

Methyl-monomethoxy conduritol-B and methyl-dimethoxy conduritol-B were synthesized starting from 2-methylbenzo-1,4-quinone. Bromination of 2-methylbenzo-1,4-quinone was followed by the reduction of the carbonyl groups with NaBH 4 to give a dioldibromo compound. Methyl-dimethoxy conduritol-B was synthesized from the reaction of the dioldibromo compound with CH 3 ONa, followed by acetylation with Ac 2 O-pyridine to obtain methyl-dimethoxy diacetate. On the other hand, acetylation of the methyl-dioldibromo compound followed by reaction with LiOH gave a monoepoxide compound stereoselectively. The reaction of the epoxide with H + /Ac 2 O afforded the monobromo triacetate. Controlled reaction of monobromo-triacetate with CH 3 ONa in MeOH furnished the desired new methyl-monomethoxy conduritol-B. The structures of all synthesized compounds were characterized by spectroscopic methods. [ABSTRACT FROM AUTHOR]

Radicals formed by SmI 2 –H 2 O-mediated electron transfer to the carbonyl group of unsaturated five-membered lactones undergo diastereoselective cyclisation to give cyclohexane-1,4-diols. The use of HMPA as an additive with SmI 2 –H 2 O gave improved conversion and diastereoselectivity in the cyclisations. [ABSTRACT FROM AUTHOR]

In this study; novel aryl, heteroaryl, pyrrolyl and phosphoryl groups containing pyrrolizines were synthesized by the ring annulation reaction of aryl or heteroaryl substituted α-phosphoryl-α,β-unsaturated ketones with pyrrole under mild reaction conditions. This domino reaction involves scandium triflate catalyzed addition of pyrrole to the double bond of α-phosphoryl-α,β-unsaturated ketones, carbonyl group and finally ring annulation sequences. The presented work provided a convenient way for the synthesis of novel bispyrrolic compounds. [ABSTRACT FROM AUTHOR]

In this paper, we report reversible capture and release of aromatic amines by diphenylpropanetrione ( DPPT ). Addition of aromatic amines to the central carbonyl group occurred readily at ambient temperature to provide the aromatic amine adducts of DPPT ( DPPT–aromatic amines ), which has a hemiaminal structure. On the other hand, washing a solution of DPPT–aromatic amine with diluted hydrochloric acid (HCl) enabled successful recovery of DPPT to demonstrate the reversible nature of this system. [ABSTRACT FROM AUTHOR]

New non-flattened amino group-containing building blocks and fluorinated analogs based on the spiro[3.3]heptane motif were synthesized. The syntheses included a challenging deoxofluorination of sterically hindered carbonyl groups via an intermediate carbocation. The synthesized compounds could be useful in medicinal chemistry due to their three-dimensional shape, and a different pattern of the fluorine substitution. [ABSTRACT FROM AUTHOR]

Elemental fluorine was successfully added across the double bond of various α,β-unsaturated carbonyl compounds. A necessary ingredient is a presence of alcohol in the solvent mixture. Unlike all other halogen's addition to olefins, fluorine adds itself in a syn mode specificity. The vic difluoro products were easily dehydrofluorinated to form the corresponding α-fluoro carbonyl derivatives. [ABSTRACT FROM AUTHOR]

Biaryl ethers condense directly with carbonyl groups on diazafluorenones, acenaphthenequinone, and isatins, to give a variety of spirocyclic compounds. The condensation reactions are promoted by the Brønsted superacid, CF 3 SO 3 H (triflic acid). This methodology provides a convenient one-pot synthetic route to aromatic spirocycles. [Display omitted] [ABSTRACT FROM AUTHOR]

Developments are reported in the catalytic synthesis of biaryls containing an ortho -carbaldehyde or 6 H -dibenzopyrans in the presence of palladium/norbornene as catalyst. The reaction of o -substituted aryl iodides and o -bromobenzyl alcohols proceeds by unsymmetrical aryl-aryl coupling to form a seven-membered oxapalladacycle intermediate, which may undergo an intramolecular redox process to form carbonyl groups or a C–O coupling to six-membered cyclic ethers. The predominant formation of dibenzopyrans as well as of biaryl structures containing the oxidized CHO group in one ring and the reduced CH 2 OH in the other is described along with some mechanistic insights. [ABSTRACT FROM AUTHOR]

Nitrile oxides afford 2-isoxazoline heterocycles through [2 + 3] cycloaddition reactions with alkenes. These heterocycles can be converted to useful intermediates, such as β-hydroxy ketones and γ-amino alcohols, leading to pharmaceutical and agrochemical compounds. However, nitrile oxides directly connected to a carbonyl group show low reactivity owing to the decrease in energy of the dipole HOMO. Furthermore, when dissymmetric internal alkenes are used, regioselective control is difficult. Herein, we have designed nitrile oxides bound to alkenes through the oxime group and demonstrated their intramolecular [2 + 3] cycloaddition reactions. The desired cycloadducts were obtained in high yields and as single regioisomers. Furthermore, face-selective cycloaddition reactions were achieved by introducing a stereocenter into the linker moiety, affording the desired cycloadducts with good diastereoselectivity. [Display omitted] [ABSTRACT FROM AUTHOR]

The first total synthesis and structural elucidation of cryptomoscatone D1, and a novel synthetic approach for cryptomoscatone D2 were achieved in 30% and 29% overall yield, respectively. The synthesis relied on the use of a key Mukaiyama aldol reaction followed by a diastereoselective carbonyl reduction that allowed the preparation of four cryptomoscatone isomers in a stereochemically divergent manner. Comparison of NMR data and CD curves of the synthetic stereoisomers and natural products confirmed the stereochemical nature of cryptomoscatone D2, and led to establishing the absolute configuration of cryptomoscatone D1. [ABSTRACT FROM AUTHOR]

Abstract: Three new 1,2-dihydro-1-oxabenz[a]azulen-2-one derivatives, 1a (R1=H, R2=Me), 1b (R1=H, R2=Ph), and 1c (R1=COOEt, R2=Me), have been synthesized by the reaction of 2-hydroxyazulene (2a) and its 1-ethoxycarbonyl derivative 2b with ethyl acetoacetate (3a) or ethyl benzoylacetate (3b) in the presence of aluminum chloride. To our knowledge, these are the first examples of this type of compound, although the yield of the products is low in some cases. Their electronic properties were studied in detail utilizing the analyses of 1,2-dihydro-1-oxabenz[a]azulen-2-one derivative 1a by the spectroscopic and voltammetric analyses. The analyses revealed that the fused α-pyrone system lowers both the HOMO and the LUMO energies, relative to those of parent azulene (10), but has much pronounced effect on the LUMO, consequently, leading to decrease in HOMO–LUMO gap, compared with those of 10. These results should be attracted to the development of amphoteric redox materials. Reactivity toward electrophilic reagents was also examined by bromination and Vilsmeier–Haack formylation reactions of 1a. To evaluate the scope of the reaction products we have examined Sonogashira cross-coupling reaction of the bromination products with trimethylsilylacetylene and conversion of the formylation product to dibromoolefin by the reaction with phosphorous ylide prepared with CBr4 and Ph3P. Effective extension of the π-electron system in the ethynyl products has been revealed by the spectroscopic analysis. These reaction products would be attracted to the application as a terminal group for electronic applications. [Copyright &y& Elsevier]

Abstract: Herein a simple one-pot metal-free synthesis of alkyl-, aryl-, heteroaryl- and alkoxycarbonyl substituted 1,3-bis(dimethylamino)benzene derivatives is described. The products were prepared from the corresponding methyl ketones or compounds with an α-methylene group in regard to the carbonyl group, using N,N-dimethylacetamide dimethyl acetal (DMADMA) as the reagent. [Copyright &y& Elsevier]

Abstract: The reductive coupling reaction between benzaldehyde and ethyl trifluoroacetate in the presence of magnesium and chlorotrimethylsilane in N-methyl-2-pyrrolidinone gave the acetal of the corresponding coupling compound in good yields. The yield of the coupling product largely depended on the benzaldehyde concentration in the solution and it was essential to avoid the formation of pinacol type compounds in order to obtain the coupling product in high yields. The subsequent desilylation of the acetal using tetrabutylammonium fluoride easily yielded an acyloin compound as the sole product after the transposition of the carbonyl group through keto–enol tautomerism. [Copyright &y& Elsevier]

Abstract: Zerumbone 1, having powerful latent reactivity and containing two conjugated double bonds and a double conjugated carbonyl group is the major component of the essential oil of wild ginger, Zingiber zerumbet Smith. The conjugation system plays an important role in the expression of biological activity. N-Bromosuccinimide (NBS) reaction of 1 gave high reactive intermediate 2 with an exo-methylene group, which was obtained from 1 quantitatively. Treatment of 2 with nucleophiles gave various zerumbone-pendant derivatives, including C–H, C–O, C–N, and C–C bond formation, maintaining the conjugation system through SN2′-type reaction. Almost all zerumbone-pendant derivatives showed a good value of IC50 against the suppressive effect of NO generation. Among them, amine derivative 5, binding with 2 mol of zerumbone, showed the strongest activity (IC50: 0.24 μM). [Copyright &y& Elsevier]

Abstract: Asymmetric syntheses of (−)-martinellic acid and (−)-4-epi-martinellic acid were achieved in 20 steps from commercially available starting materials using a diastereodivergent strategy. The conjugate addition of lithium (R)-N-allyl-N-(α-methyl-p-methoxybenzyl)amide to tert-butyl (E)-3-[2′-(N,N-diallylamino)-5′-bromophenyl]propenoate and alkylation of the resultant β-amino ester with methyl bromoacetate were used as the key steps to install the C(9b) and C(3a) stereogenic centres, respectively. Subsequent cyclisation to the corresponding pyrroloquinolin-2-one and reduction of the C(4)-carbonyl group was followed by two complementary procedures for olefination and concomitant intramolecular Michael addition, which gave both C(4)-epimers of this tricyclic molecular architecture in >99:1 dr. Subsequent elaboration of these templates provided access to (−)-martinellic acid and, for the first time, (−)-4-epi-martinellic acid. [Copyright &y& Elsevier]

Abstract: For the chemical conversions of a β-trifluoromethyl-β-amino acid ((S)-4,4,4-trifluoro-3-aminobutyric acid, 1), such as the N-terminus protection with benzyloxycarbonyl or tert-butoxycarbonyl group, the C-terminus protection with benzyl or tert-butyl group, and peptide elongation at the both termini, highly practical protocols were established. Through these conversions, the stereochemistry of 1 and/or its condensation counterpart was maintained. Because the protocols developed here are indispensable for the application of 1 in peptide engineering, they would expand the utility of 1 and its derivatives. [Copyright &y& Elsevier]

Abstract: We have designed and synthesized isonetropsin and its one pyrrole unit analogue in which the amine and carbonyl groups have been switched in positions 2 and 4, respectively instead of 4 and 2 positions of the natural antibiotic netropsin. [Copyright &y& Elsevier]

Abstract: (Di)benzoxanthones possessing additional benzene units on one or both sides of xanthone were prepared via dehydration of the corresponding dihydroxybenzophenone, where a catalytic amount of K2CO3 dramatically increased the yields. Chemical transformations of the versatile carbonyl groups of (di)benzoxanthones could derive fluorescent materials. [Copyright &y& Elsevier]

Abstract: A series of l-proline amides with 2-aminoimidazole have been synthesized and found to be highly efficient organocatalysts for aldol reactions when an appropriate acid was added to control and activate the acceptor carbonyl group. Under optimized reaction conditions, high yields (over 80%) and high selectivities (ee 98%, de 98/2) were obtained in intermolecular aldol reaction even with only 1 equiv of ketone. Likewise, these systems also can catalyze intramolecular aldol reactions with good results. [Copyright &y& Elsevier]

Abstract: The regioselectivity of the Baeyer–Villiger oxidation of α-chlorocyclobutanone derivatives is markedly affected by substituents in position γ to the carbonyl group. The reaction of steroidal α-chlorocyclobutanones with m-chloroperoxybenzoic acid results in the formation of γ-chloro-γ-lactones and/or α-chloro-γ-lactones depending on the substitution pattern of the four-membered ring. In the reactions of γ-unsubstituted α-chlorocyclobutanones, the exclusive formation of γ-chloro-γ-lactone results from the migration of the chlorinated substituent (CHCl) versus the alkyl group (CH2), contrary to the expected migratory aptitude. In explaining the unusual regioselectivity observed in these reactions, steric effects and dipole interactions in the formation of the reactive Criegee intermediates are considered and the stereoelectronic effect is postulated to be more important than the intrinsic migratory aptitude. [Copyright &y& Elsevier]

Abstract: A new versatile synthesis of 3-piperidones is described, starting from amino acids. It uses, as a key step, an iron carbonyl-mediated intramolecular tandem isomerization–aldolisation reaction. These new heterocycles appear as useful scaffolds for the total synthesis of various types of bioactive molecules. [Copyright &y& Elsevier]

Abstract: A flexible route for the stereoselective synthesis of a variety of 3-aryl dihydroisoquinolones and tetrahydroisoquinolines has been developed. The key step is a diastereoselective photoinduced 6π-electrocyclic ring closure of enantiopure aromatic enehydrazides via a 1,4-remote asymmetric induction. N–N bond cleavage to release the chiral appendage from the preliminary annulated compounds and/or concomitant reduction of the lactam carbonyl group completed the synthesis of the title compounds. [Copyright &y& Elsevier]

Abstract: A migration of methyloxycarbonyl group from secondary to primary hydroxyl was observed in furanosides (ribosides and xylosides) under usual desilylation conditions using tetrabutylammonium fluoride. The migration was studied further on several alkyloxycarbonyl furanosides under either basic or acidic conditions. As follows from 13C labelling experiments and product distribution, the migration in xylosides, proceeds intramolecularly via six-membered cyclic carbonate, whereas in ribosides, the migration is intermolecular. Acidic conditions prevented the migration in ribosides whereas the migration in xylosides was circumvented under neutral conditions. [Copyright &y& Elsevier]

Abstract: The natural product angelone was readily accessed with a remarkable biomimetic journey that sequentially features carbonyl formation–elimination, 6π-electrocyclization, visible light-promoted singlet O2 Diels–Alder reaction, Kornblum–DeLaMare-type peroxide rearrangement, 6π-electrocyclic ring-opening, and conjugative addition–elimination as the key steps. With key intermediates isolated and characterized, this study stands to reveal a rare system in which bio-inspired synthetic strategies were found to mirror experimental realities. [Copyright &y& Elsevier]

Abstract: 1,2-Benzisothiazolin-3-ones were synthesized from 1,3-benzoxathiin-4-one 1-oxides by means of a nonhazardous and inexpensive method. The 1,3-benzoxathiin-4-one 1-oxides were prepared by oxidation of 1,3-benzoxathiin-4-ones with hydrogen peroxide in the presence of a catalyst. Attack of amines on the carbonyl groups of the 1,3-benzoxathiin-4-one 1-oxides and subsequent elimination of carbonyl compounds likely produced sulfenic acids, which then underwent ring closure to afford the 1,2-benzisothiazolin-3-ones. [Copyright &y& Elsevier]

Abstract: The construction of the title compounds has been achieved from properly substituted linear alkynylamides through the suitable combination of two key cyclization steps. First, an intramolecular PIFA-mediated alkyne amidation protocol leads to the creation of the pyrrolidinone nucleus, which under proper manipulation of the generated keto–carbonyl group permits the assembling of the indolizidinone skeleton by the introduction of a subsequent ring closing olefin metathesis step. Finally, its transformation into a series of substituted mono- and trihydroxylated indolizidinone derivatives is achieved by manipulation of the remaining unsaturated fragment under hydrogenation and dihydroxylation conditions. [Copyright &y& Elsevier]

The photochemical reactivity of acyl azolium salts derived from aliphatic carboxylic acids has been investigated. These species, which serve as models for intermediates generated in N-heterocyclic carbene (NHC) organocatalysis, undergo Norrish type II elimination reactions under irradiation with UVA light in analogy to structurally related aromatic ketones. Moreover, efficient Norrish-Yang cyclization was observed from an adamantyl-substituted derivative. These results further demonstrate the ability of NHCs to influence the absorption properties and photochemical reactivity of carbonyl groups during a catalytic cycle. [Display omitted] [ABSTRACT FROM AUTHOR]