Cyclization of α-furylmethyl derivatives of linalool by "activated" DMSO

The cyclization of two stereoisomeric -furylmethyl derivatives of linalool initiated by "activated" DMSO leads to the corresponding substituted limonene in low yield. The stereochemistry of these products was not established.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, B-334. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 471–473, February, 1992.     

Synthesis ofα-substitutedα-amino acids by the alkylation of 5-oxazolinone derivatives

Methods have been developed for the alkylation of 5-oxazolinone derivatives in DMF in the presence of K₂CO₃, KOH, or diisopropylethylamine and a phase transfer catalyst as well as for the preparation of-methyl-phenylalanine,-methylalanine,-methylalanine, and the methyl ester of N-benzoyl--methylalanine. Increasing the initial concentration of the starting 5-oxazolinone in the reaction mixture leads to a sharp drop in the yield of reaction products due to side condensation reactions. The reaction of 2-phenyl-4-benzyl-5- oxazolinone with ethyl iodide gave a dimer namely, 3-(benzoylamino)-3,5-dibenzylpyrrolidine-2,4-dione.Latvian Institute of Organic Chemistry, LV-1006 Riga. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 829–833, June, 1994. Original article submitted January 21, 1994.     

α-Carbonyl Radical Cyclization for the Total Synthesis of Natural Products

Intramolecular radical cyclization reactions are now used routinely to synthesize carbocyclic and heterocyclicstructures. We have reported that α-carbonyl radicals 1, generated from the corresponding iodo ketones or enones,underwent intramolecular radical cyclization smoothly to afford products 2. [1,2]     

Enantioselective Synthesis of the Platensimycin Core by Silver(I)-Promoted Cyclization of Δ6-α-Iodoketone

A chiral-pool-based synthesis of the platensimycin core was achieved using (S)-lactic acid as an inexpensive starting material. The cyclohexenone ring was closed in a Mukaiyama–Michael domino sequence, while the quaternary stereocenter was created by a highly stereoselective decarboxylative allylation. The spirobicyclic skeleton was constructed by a RCM reaction. A new silver(I)-promoted cyclization reaction of Δ⁶- and Δ⁷-α-iodoketones was developed and applied for the pivotal carbon–carbon bond formation. The scope and limitations of this methodology are also presented.     

α-Aminophosphonate derivatives of triethoxysilane for the synthesis of surface-modified silica

Abstract

A convenient synthetic route for the preparation of α-aminophosphonate derivatives of triethoxysilane, attractive precursors for silica surface functionalization, was developed. The condensation of commercially available APTES with carbonyl compounds followed by Pudovik reaction of imines with diethyl phosphite yielded desired N-phosphonomethyl functionalized (3-aminopropyl)triethoxysilanes in high yields without further purification. The chemical structures of obtained products were undoubtedly proved by ¹H, ¹³C and ³¹P NMR spectroscopy, elemental analysis and mass spectrometry.     

Formation of a Hydroxyperhydroindanone by Reductive Cyclization of γ-Cyanoketone

The reduction of nitrile with alkali metal-ammonia is known to produce amine or hydrocarbon. Arapokos and coworkers^1,2 had shown that such reduction of a tertiary nitrile gave exclusively the hydrocarbon resulting from decyanation, whereas primary and secondary nitrile gave both the amine and decyanation products. Such decyanation pathway can be suppressed in the presence of a proton source e.g. methanol³ and by the proper choice of metal⁴. It is assumed that the reduction of a primary or secondary nitrile to amine involves the intermediate anion (1).     

Cyclization of the methyl ester of α-propionyllevulinic acid

Summary Cyclization of methyl -propionyllevulinate to 2,3-dimethylcyclopenten-2-one and methyl 3,4-dimethylcyclopenten-3-one-2-carboxylate was accomplished.     

Synthesis of fluoroalkyl-containing β-hydroxyketones by reduction of the corresponding β-diketone derivatives

The rcgioselective synthesis of fluoroalkyl-containing P-hydroxyketones by the reduction of the salts of the corresponding -diketones with LiAlH₄ was proposed. This is the sole method for the synthesis of -hydroxyketones with two fluoroalkyl substituents.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1493–1495, June, 1996.     

Conductivity studies of the molecular encapsulation of sodium perfluoroctanoate byβ-cyclodextrin derivatives

The molecular encapsulation of sodium perfluoroctanoate (SPFO) by hydroxypropyl--cyclodextrin (HP--CD) or 2,6-di-O-methyl--cyclodextrin (DM--CD) has been analyzed by measuring the conductivity in solution of the ternary systems formed by CD + SPFO + H₂O. The studies were carried out at 25 °C using a fully computerized electrical conductivity technique. The measurements were made as a function of CD concentration at various non-micellar concentrations of SPFO, and as a function of CD and SPFO concentrations with [CD]/[SPFO] constant at stoichiometric ratio. The inclusion complexes, HP--CD-SPFO and DM--CD-SPFO, were characterized through the stoichiometry, which has been found to be 1 : 1 in both cases, and the binding constants, which have been evaluated from the conductivity data with a model proposed by us considering the variation of the ionic molar conductivities with the concentration and the association of the surfactant counterion to the inclusion complex. The resultingK values indicate that the interaction between the CD cavity and the monomeric SPFO is strong and similar in both cases.     

Oxidation of the α-ketol and enone derivatives of cyclohexanone by tetrazolium salts

A new red-ox reaction, leading to the respective keto derivatives from α-ketol and enone derivatives of cyclohexanone, is reported.     

α,n-Didehydrotoluenes by Photoactivation of (Chlorobenzyl)trimethylsilanes: An Alternative to Enyne-Allenes Cyclization

Doubly radical: A novel entry to α,n-didehydrotoluene (DHT) diradicals is disclosed and proceeds through the photochemical activation of (chlorobenzyl)trimethylsilanes with chloride loss and elimination of the SiMe(3) (+) group. The products formed in solution are indicative of the intermediacy of the three isomers of the α,n-DHT.     

Inhibition of dextransucrase by α-D-Glucose derivatives

alpha-D-Glucopyranosyl fluoride was modified at positions 2, 3, or 5 and these analogs were tested as substrates and inhibitors of dextransucrase from Leuconostoc mesenteroides B-512F. The analogs studied were 2-deoxy-2-fluoro-alpha-D-glucopyranosyl fluoride, 3-deoxy-3-fluoro-alpha-D-glucopyranosyl fluoride, 3-deoxy-3-thio-alpha-D-glucopyranosyl fluoride, and 5-thio-alpha-D-glucopyranosyl fluoride. Kinetic constants for alpha-D-glucopyranosyl fluoride were also determined. None of the alpha-D-glucopyranosyl fluorides were accepted as substrates for dextransucrase. 2-Deoxy-2-fluoro-alpha-D-glucopyranosyl fluoride, 3-deoxy-3-fgluoro-alpha-D-glucopyranosyl fluoride, and 3-deoxy-3-thio-alpha-D-glucopyranosyl fluoride were competitive inhibitors with Ki values of 63, 93, and 53 mM, respectively. The Km for alpha-D-glucopyranosyl fluoride was found to be 26 mM. The data indicate that the hydroxyl groups at C2 and C3 are important for proper binding of alpha-D-glucopyranosyl fluoride for the active site of dextransucrase and that the C3-hydroxyl probably acts as a hydrogen-bond donor.     

Formation of n-α-diazoacetylureas by the reaction of derivatives of 5-hydroxy-1,2,3-triazole-4-carboxamide with phenylisocyanate and phenyl isothiocyanate

The reaction of derivatives of 5-hydroxy-1,2,3-triazole-4-carboxamide with phenyl isocyanate and phenyl isothiocyanate proceeds at the 4-carboxamide fragment of the first, leading to the formation of derivatives of N-phenyl-N-(2-diazo-2-carbamoylacetyl)urea and -thiourea correspondingly.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1347–1350, October, 1992.     

Total Synthesis of Dictyodendrins A–F by the Gold-Catalyzed Cascade Cyclization of Conjugated Diyne with Pyrrole

The total synthesis of dictyodendrins A–F was achieved by using the gold(I)-catalyzed annulation of a conjugated diyne with N-Boc-pyrrole for direct construction of the pyrrolo[2,3-c]carbazole scaffold. Late-stage functionalization of the resulting pyrrolo[2,3-c]carbazole to introduce various substituents provided divergent access to dictyodendrins. Some dictyodendrin analogues exhibited inhibitory activities toward CDK2/CycA2 and GSK3.     

Synthesis of trialkylaluminum derivatives by the reaction of non-solvated aluminum hydride with α-olefins

Hydroalumination of -olefins by non-solvated polymeric aluminum hydride (AlH₃) _n occurs at 120—140 °C. Mechanochemical activation accelerates this reaction. The addition of catalytic amounts of the prepared R₃Al forms to the reaction system decreases the temperature of the process to 90—100 °C. The greatest initiation effect is observed when ate-complexes of the MAlR₄ type (M = Li, Na) are used: the reaction occurs with a higher rate already at 60—90 °C affording R₃Al free of admixtures of carbalumination products and dimers of -olefins.     

Synthesis of Substituted Benzofurans by the Tandem One-Pot Intramolecular Carbolithiation–Cyclization–Substitution Sequence

A convenient methodology for the synthesis of 3-sustituted-2,3-dihydrobenzofurans was developed based on the tandem intramolecular carbolithiation–cyclization of 2-bromophenyl-3-phenylprop-2-enyl ether, followed by trapping of the new lithiated intermediate by suitable electrophiles. Several electrophiles were tested, affording good to excellent yields. Alkyl bromides show better results than chlorides and when doubly halogenated alkyl chains are used as electrophiles only one position reacts, affording substituted benzofurans conveniently functionalized to undergo further reactions. The performance of both butyl and phenyllithium as lithiating agents was examined.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Synthesis of epoxycarbonyl pyrroline derivatives by cycloaddition of benzonitriliop-nitrophenyl-methanide toα,β-unsaturated epoxy ketones

The cycloaddition reaction of benzonitriliop-nitrophenylmethanide to , -unsaturated epoxy ketones gives a mixture of stereoisomeric epoxycarbonyl pyrrolines. Only one of the isomers was isolated as pure compound. The structure, stereo- and regiochemistry of the isolated products was established by NMR and NOE measurements as well as by mass spectral data.Department of Organic Chemistry, Belarus State University of Technology, Minsk 220630, Belarus, Dipartimento di Scienze Chimiche, Universita, 95125, Catania, Italy. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 630–633, May, 1998.     

Aryl-ONN-azoxy-α,α-dinitroalkanes and some of their derivatives

Previously unknownN-dinitroalkyl-NNO-azoxybenzenes have been prepared (by nitration ofN-(-hydroximino) alkyl-NNO-azoxybenzenes) and transformed to some derivatives.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1972–1975, November, 1994     

Synthesis of 17α-bromovinyl- and 17α-iodovinylnortestosterone derivatives

Depending upon the reaction conditions, norethisterone (1) and its ketal 2 can be transformed with tributyltin hydride to either the (E)-or(Z)-17α-(2-tributylstannylvinyl)-nortestosterone derivatives 3, 8 and 13. Further treatment with N-bromo- or N-iodosuccinimide yields the corresponding (E)- and (Z)-17α-halovinyl steroids 6,7,10 and 11. Radio-labelled (Z)-17α-(2-iodovinyl)-nortestosterone was prepared by reaction of the 17α-stannylvinyl derivative 13 with Na¹²⁵I.