A highly regio- and stereo-selective hydrostannation reaction of various fluorine-containing internal acetylene derivatives

The hydrostannation reaction of various fluoroalkylated acetylene derivatives with tributyltin hydride was investigated using a variety of catalysts in toluene. Among them, the Et₃B-induced hydrostannation reaction gave the highest regio- and stereo-selectivity. Their selectivity was mostly influenced upon the difference of the substituent X at the aromatic ring of the aryl-substituted internal acetylenes. Thus, the acetylenes having a halogen atom or an electron-donating group as X reacted smoothly with tributyltin hydride, affording the vinylstannane 4Z exclusively, while the acetylenes having an electron-withdrawing group (X=CO₂Et, NO₂) resulted in the preferential formation of 5E. The plausible mechanism of the formation of these products was discussed.     

Mild and efficient boronic acid catalysis of Diels-Alder cycloadditions to 2-alkynoic acids

The concept of boronic acid catalysis (BAC) for the activation of unsaturated carboxylic acids is applied to the Diels-Alder cycloaddition between 2-alkynoic acids as dienophiles and various dienes. These [4+2] cycloadditions produce cyclohexadienyl carboxylic acids, which can be oxidized in situ to produce polysubstituted aromatic carboxylic acids. The boronic acid catalyst is suspected to provide activation by a LUMO-lowering effect of the unsaturated carboxylic acid likely via a covalent, monoacylated hemiboronic ester intermediate.     

Dual inhibition of mycobacterial fatty acid biosynthesis and degradation by 2-alkynoic acids

2-Hexadecynoic acid and 2-octadecynoic acid have cidal activity against Mycobacterium smegmatis and Mycobacterium bovis BCG. At subinhibitory concentrations, M. smegmatis rapidly transformed [1-(14)C]-2-hexadecynoic acid into endogenous fatty acids and elongated them into mycolic acids. Toxic concentrations of 2-hexadecynoic acid resulted in accumulation of 3-ketohexadecanoic acid, which blocked fatty acid biosynthesis, and 3-hexadecynoic acid, an inhibitor of fatty acid degradation. The combination of these two metabolites is necessary to achieve the inhibition of M. smegmatis. We conclude that 2- and 3-hexa/octadecynoic acids inhibit mycolic acid biosynthesis, fatty acid biosynthesis, and fatty acid degradation, pathways of significant importance for mycobacteria.     

Benzoselenazol-2-ylalkylcarboxylic and benzoselenazol-2-ylarylcarboxylic acids and their derivatives

A preparative method for the synthesis of the previously unknown benzoselenazol-2-ylalkylcarboxylic and benzoselenazol-2-ylarylcarboxylic acids consisting in the condensation of zinc o-aminoselenophenoxide with dicarboxylic anhydrides in the presence of hydrochloric acid is proposed.     

Highly selective hydrohalogenation reaction of substituted 2,3-allenoates

The hydrohalogenation reaction of 1-alkyl substituted 1,2-allenyl carboxylic acid esters (1) with MX (M= Na, or Li, X= Cl, Br, I) afforded a mixture of (5,7-unsaturated 3-halo-3-alkenoates (2) and α,β-unsaturated 3-halo-2-alkenoates (3) in HOAc, while using a mkture of HOAc-CF3CO2H (1:1) or CF3CO2H as the reaction medium the corresponding reaction cleanly produced β,γ-unsaturated 3-halo-3-alkenoates (2) as the sole products in high yields. The subsequent coupling reactions were studied.     

Synthesis of pyrrole-2-carboxylic acids and their N-vinyl derivatives

Haloform cleavage of 2-trifluoroacetyl- and N-vinyl-2-trifluoroacetylpyrroles gives pyrrole-2-carboxylic acids and their N-vinyl derivatives in good yields; most of these compounds do not melt between 120–190C, but rather decompose with CO₂ evolution.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 612–616, May, 1990.     

Synthesis of 2-keto-4-phosphorylbutyric acids and their derivatives

The Claisen condensation of 3-phosphorylated propionitriles with diethyl oxalate has been examined. The product of the condensation of 3-(methylethoxyphosphinyl)propionitrile, following hydrolysis, has been shown to be the enol form (Z-isomer) of 4-(methylhydroxyphosphinyl)-3-cyano-2-ketoburyric acid. On crystallization from water, the other isomers (the E-isomer of the enol or the keto-forms) were not isolated. Distillation of the products of silylation of the reaction mixture with hexamethyldisilazane gave both geometric isomers of the enol (Z and E). In aqueous solution, the enol gradually cyclizes to give 2-hydroxy-3-(methylhydroxyphosphinyl)citraconimide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2120–2127, September, 1990.     

A palladium-catalyzed regio- and stereoselective four-component coupling reaction

Pd(PPh(3))(4) catalytically assembles sulfenamide, alkyne, carbon monoxide, and diphenyl diselenide regio- and stereoselectively in a one-pot four-component coupling reaction to yield (Z)-beta-selenyl acrylamides. The reaction proceeds in good to excellent yields (60-95%) and is tolerant of a range of functional groups on both the nitrogen of the sulfenamide and the alkyne. Moderate selectivities ranging from 4:1 to 7:1 beta-selenyl to beta-sulfenyl acrylamide have been observed despite the initial concentration of 2:1 selenium to sulfur in the reaction. The chalcogeno selectivity was found to depend directly on CO pressure; increased pressure decreased selectivity for selenium over sulfur.     

Some aminophosphinocarboxylic acids and their derivatives

The addition of Schiff bases of α-aminoacid esters to vinylphosphoryl compounds was studied as a method for the synthesis of phosphinothricin and its analogues. The reaction was found to proceed smoothly in DMSO in the presence of strong nitrogen bases and under the conditions of phase transfer catalysis. The Claisen condensation of β-phosphorylated propionitrile with diethyl oxalate was studied; phosphorylated derivatives of hydroxycitraconic acid nitrile were prepared on hydrolysis; transformation of such a derivative into a cyclic imide as well as into trimethylsilyl esters of these acids and their Z → E transformation were investigated. Cyclization reactions between α,ω-dibromoalkanes and phosphoryl compounds containing an active methylene group affording cyclopropane and other cyclic derivatives were studied. The cyclopropane ring is cleaved by amines to give aminophosphinocarboxylic acids.     

A novel synthesis of indole derivatives by the reaction of N‐arylhydroxamic acids with malononitrile

An approach to indole derivatives from N‐arylhydroxamic acids and malononitrile via a [3,3]‐sigmatropic rearrangement and intramolecular cyclization is described. Reactions of N‐arylhydroxamic acids 1a‐c, 2a‐c and 3a‐c with malononitrile in the presence of triethylamine at room temperature gave the corresponding α‐cyanoacetamide derivatives 4a‐c, 5a‐c, 6a‐c, 7a‐c and 8a‐c . Thermal treatment of 4a‐c, 5a‐c and 7a‐c with a base, e.g. triethylamine and sodium methoxide, caused intramolecular cyclization and deacylation to afford the corresponding indole derivatives 9‐11 .     

Solid-phase hydrohalogenation of 2-methyl-2-butene

Complex formation between 2-methyl-2-butene and hydrogen halides (HX, X=Cl, Br) and the hydrohalogenation reaction was studied in the solid phase in the range of 80–150°K by IR spectroscopy. It was shown that 2-methyl-2-butene forms 11 and 12 complexes with HX. The hydrohalogenation reaction is realized by rearrangement of the 12 complex into a complex of the hydrohalogenation product with HX. The kinetics of the transformation depend on the ratio of the reagents. With an excess of the olefin the reaction is described by a kinetic equation of first order with respect to the complex of the initial reagents up to 60–80% conversion; with an excess of HX it is described by an equation of polychronous kinetics. The effective activation energy of the solid-phase halogenation of 2-methyl-2-butene is not greater than 20 kJ/mole. A molecular mechanism of addition to olefins in the solid phase is examined.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 1, pp. 34–40, January–February, 1987.     

A novel access to highly functionalised β-lactams by regio- and stereoselective 1,3-dipolar cycloaddition reaction

A highly regio- and stereoselective synthesis of novel spiro pyrrolidines/pyrrolizidines containing β-lactam and oxazolone moieties under two different conditions is achieved using [3+2] cycloaddition methodology in moderate to good yield.     

Pd-catalyzed regio- and stereoselective cyclization-heck reaction of monoesters of 1,2-allenyl phosphonic acids with alkenes

[reaction: see text] The cyclization-Heck reactions of monoesters of 1, 2-allenyl phosphonic acids with alkenes were studied. The reaction afforded 4-(1-Z-alkenyl)-2-ethoxy-2,5-dihydro[1,2]oxaphosphole 2-oxides regio- and stereoselectively. Pd(II) was regenerated from the in situ formed Pd(0) using CaH2(cat.)/NaI/O2 or benzoquinone to furnish the catalytic cycle.     

A facile formation of cyclic selenuranes and a cyclic selenurane oxide in the reaction of 2-methylseleno- and 2-phenylselenobenzoic acids and their derivatives with t-butyl hydroperoxide

The reaction of 2-methylselenobenzoic acid with 1,1′-carbonyldiimidazole followed by addition of t-butyl hydroperoxide gave cyclic selenuranes $\text{2a}$ and $\text{3a}$, suggesting the intramolecular insertion of the neighboring selenium atom into the OO bond of t-butyl 2-methylselenoperoxybenzoate. In the reaction of 2-phenylselenobenzoyl chloride with t-butyl hydroperoxide, cyclic selenurane $\text{2b}$ and the oxide $\text{7}$ were obtained.     

Formation of benzofuran and 2H-chromene structures in one reaction. A novel synthesis of 2H-chromene derivatives

Heating the morpholinal of nitrosalicylic aldehyde with methyl propiolate in acetonitrile in the presence of Cul affords an equimolar mixture of 2-methoxycarbonylmethyl-3-morpholino-5-nitrobenzofuran and 3-methoxycarbonyl-2-morpholino-6-nitro-2H-chromene, the structures of which were determined by X-ray analysis. Only the 2H-chromene mentioned above was obtained in the absence of Cul and solvent.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1222–1228, May, 1996.