Synthesis and bioactivity of α-galactosylceramide analogues bearing an aryl group within the fatty amide chain

We describe the synthesis and bioactivity of analogues of α-galactosylceramide (1) bearing a long-chain alkyl group substituted at the meta or para position of an aryl group embedded within the amide chain. We compared the ability of these compounds and of 1 and C6Ph (2, which has a phenyl group at the amide chain terminus) to stimulate murine invariant Natural Killer T cells and to dock with human CD1d.     

Selenium catalyzed conversion of vinyl halides into α-alkoxy acetals

The reaction of vinyl halides with phenylselenenyl chloride in alcohols affords α-alkoxy acetals and diphenyl diselenide which can be oxidized to PhSe cations by nitrate or persulfate anions. The reaction can be carried out with catalytic amounts of PhSeCl or PhSeSePh. The reaction proceeds through the formation of the methoxyselenenylation product which then suffers solvolysis. Under controlled conditions, the 1-phenyl-1-methoxy-2-bromo-2-phenylselenenyl ethane was isolated from the reaction of β-bromostyrene and PhSeCl in methanol. Several deselenenylation reactions of this α-halogenoselenide are reported.     

Oxyfunctionalization of ketones bearing α-methylene group with piperidine oxoammonium salt.Synthesis of α-diketones from monoketones

A facile method for the title transformation is described. The reaction of 2,2,6,6-tetramethyl-4-methoxypiperidine oxoammonium chloride (1b) and ketones bearing a-methylene group in acetonitrile proceeded smoothly to give the a-oxyfunctionalized coupling products (6a-h). These coupling products decomposed upon heating in acidic medium to produce a-diketones (7a-h) in good to excellent yields.     

Reactions of bicyclic phosphonates with halides of α-halocarboxylic acids

Novel types of substituted framework phosphonates have been synthesized via functionalization of bicyclic compounds obtained in the reaction of 2-ethoxyvinyl dichlorophosphonate with different phenols. The reactions of functionalized bicyclic phosphonates with triphenyl phosphine have been studied; antimicrobial activity of the prepared compounds has been investigated.     

α-Metallated vinyl carbanionoids: III. Reactions of α-triorganostannylvinyllithiums with group IVB organometallic halides: Formation of α-trimethylplumbylvinyllithiums

Reactions of α-stannylvinyllithiums RR′CC(Li)SnMe₃ with halides Me₃MCl (M = Si, Ge, Pb) give the corresponding mixed bis(trimethylmetal)alkenes RR′CC(SnMe₃)₃. With two equivalents of methyllithium and trimethyllead chloride, RR′CC(SnMe₃)₂ can be converted to RR′CC(PbMe₃)₂. The latter, as well as RR′CC(SnMe₃)PbMe₃, undergoes transmetallation with methyllithium to give α-plumbylvinyllithiums RR′CC(Li)PbMe₃ which are more stable and apparently less basic than the corresponding α-stannyl anions.Multinuclear NMR data for the anionic species are presented and discussed.     

Microwave activation of an asymmetric Michael reaction: unexpected behaviour of chiral α-alkoxy imines

While it has been previously established that chiral α-alkoxy imines undergo thermal rearrangement at temperatures above 50°C, the microwave activation of the Michael addition between chiral imine 3b and methyl acrylate at 100°C led cleanly to the corresponding Michael adduct 5b without the formation of any rearranged product and with the same regio- and stereoselectivity as the corresponding thermal condensation at 40°C (ee 95%).     

Oxazolidinone/enamine ratios in the reactions of α-silyloxy and α-alkoxy aldehydes with proline

α-Silyloxy and α-alkoxy aldehydes (propanal derivatives 1–4), when treated with proline in DMSO-d₆, give oxazolidinones rather than enamines. In fact, the relative trend is much stronger than that of all other carbonyl compounds examined, including simple aldehydes, α-branched aldehydes, α-(alkylthio)aldehydes, and standard ketones. For 1–4, the high prevalence of oxazolidinones prevents or delays the partial racemization of the α-stereocenters.     

Synthesis of polyfunctionalized pyrroles bearing C-2 α-azido side-chains and displacement of the α-azido group by various nucleophiles

Tetrasubstituted pyrroles bearing C-2 α-azido side-chains were synthesized employing a new class of diazides, α,γ-diazido α,β-unsaturated esters, and 1,3-dicarbonyl compounds under simple thermal conditions. Further investigation of the synthetic utility of the obtained pyrroles reveals unexpected displacement of the α-azido group at the C-2 side-chain by a variety of nucleophiles. This two-step process exhibits a broad substrate scope, good functional group tolerance, simple operation, and high reaction efficiency, providing an easy access to polyfunctional pyrroles with novel substitution patterns.     

Iodocarbocyclization of α-iodocycloalkanones bearing an allenyl side chain: synthesis of spirocyclic cycloalkanones

AlCl₃/ICl-mediated iodocarbocyclizations of α-iodocycloalkanones bearing an allenyl side chain are described. Treatment of iodocycloalkanones 4a-i with AlCl₃/ICl gave spirocyclic cycloalkanones 5a-i and 6a-i as a mixture of products.     

Structure and photoelectric properties of LB films of porphyrin bearing pyridinium with long-chain alkyl group

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Synthesis of a β-cyclodextrin derivative bearing an azobenzene group on the secondary face

An oxidative coupling Sonogashira-type reaction has been used to synthesize a β-cyclodextrin derivative bearing an azobenzene group on the secondary face for the first time starting from a β-cyclodextrin propargylated at one of its C-2 positions. The de-O-propargylation reaction and the formation of an oxidative homocoupling dimer were found to compete with the desired product under several Sonogashira-type reaction conditions. However, the use of a diluted reductive atmosphere of H₂ avoided the former and diminished the latter.     

Application of α-alkoxy bridgehead radical for coupling of oxygenated carbocycles

A new coupling methodology for assembly of highly oxygenated carbocycles was developed. An α-alkoxy bridgehead radical was employed as the key reactive intermediate due to its potent reactivity, minimum steric interaction, and predestined stereochemical outcome. The radical of the trioxadamantane structure, generated from the O,Se-acetal, was reacted with electron-deficient cyclic olefins of various ring sizes. Intermolecular formation of sterically congested linkages between two tetrasubstituted carbons and application of the method to a three-component coupling were two significant achievements.     

Reactivity of functional detergents with a pyridine ring and an α-nucleophile fragment in the head group

Functional detergents (FD) based on pyridine and containing aldoximate, ketoximate, and hydroxamate groups were synthesized. Their reactivity in FD/CTAB comicelles toward 4-nitrophenyl 4-toluenesulfonate (NPTS), diethyl phosphate (NPDEP), and diethylphosphonate (NPDEPS) in weakly alkaline media was investigated. Functional detergents based on pyridine are effective in the decomposition of ecotoxicants; the half-lives for the transformation of the substrates into the reaction products in the presence of a functional detergent containing, for example, a ketoximate group amounts to ∼40 s (NPTS), ∼120 s (NPDEP), and ∼5 s (NPDEPS). By analyzing the results it was possible to establish the paths to further modification of the head group of the surfactant, i.e., by varying the structure of the oximate group at various positions of the pyridinium ring aimed at the production of low-basicity functional detergents. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 5, pp. 284–291, September–October, 2008.     

Pd-catalyzed oxidative olefination of arenes with olefins via C–H activation: Retention of the leaving group

Russian Journal of Applied Chemistry - Pd-catalyzed direct oxidative olefination of arenes with olefins via C–H activation is described in the absence of any chelating directing groups. For...     

Cu-catalyzed asymmetric [3+2] cycloaddition of α-iminoamides with activated olefins

A variety of 2-amido pyrrolidines, including Weinreb-type amides, have been prepared with very high exo diastereoselectivity and enantioselectivitiy in the reaction of α-iminoamides with activated alkenes catalyzed by Cu(I)-Segphos ligands.     

Facile [3,3]-sigmatropic rearrangement in the reaction of α-chloroperfluorostyrene with allyl alcohol

The reaction of -chloroperfluorostyrene (1) with allyl alcohol in the presence of KOH at 45–50°C leads to a mixture of the allyl 2-pentafluorophenyl-2-chloro-4-pentenoate (2) and the product of the addition of the starting reagents (3). Ester2 is formed as the result of a mild [3,3]-sigmatropic rearrangement of the reaction intermediate.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1925–1926, August, 1992.