L. I. Lavrinovich

Reductive allylation of pyrrole with allylboranes. Synthesis oftrans- andcis-2,5-disubstituted pyrrolidines

Pyrrole undergoes reductive mono- and diallylation on successive treatment with β,γ-unsaturated organoboron derivatives (triallylborane, allyl(dipropyl)borane, and triprenylborane) and alcohols to give 2-allylated 3-pyrrolines andtrans-2,5-diallylated pyrrolidines. The addition of both the first and second boron-allylic fragment to the heterocycle proceeds with rearrangement. A method for transformation of thetrans-2,5-diallylpyrrolidine into thecis-isomer (heating with triallylborane at 190 °C) was developed and a series ofN-substituted derivatives of these pyrrolidines was synthesized. A method for the preparative synthesis of nonsymmetrically substitutedtrans- andcis-2-alkyl(phenyl)-5-allylpyrrolidines, based on reductive allylboration of pyrrole followed by 1,2-addition of RLi to the 5-allyl-1-pyrroline that formed, was also developed. A direct confirmation of intermediate formation of 2H- and 3H-pyrrole tautomers under the action of allylboranes was obtained. The adduct of 2H-pyrrole with BF3 was detected by NMR spectroscopy.

Synthesis of functional derivatives of 2-methylenecyclopentane and 2-methylenecyclohexane based on the allylborylation of imines, nitriles, isocyanates, and isothiocyanates by cycloalkenylmethyl(dipropyl)boranes

A study has been made of the allylborylation of imines, nitriles, isocyanates, and isothiocyanates by the action of cycloalkenylmethyl(dipropyl)boranes. Preparative methods have been developed for obtaining amines, phenylamides, and phenylthioamides of the 2-methylenecyclopentane and 2-methylenecyclohexane series.

The synthesis of spirane and bicyclic thiolanes from homoallylic thiols

3-Alkenethiols are readily cyclized upon thermal or homolytic initiation with the formation of the corresponding tetrahydrothiophenes (thiolanes) [1,2]o We have found that this reaction may serve as an efficient method for the synthesis of bicyclic thiolanes (IV) and previously unreported spirothiolanes (II). Homoallyl mercaptans (I) obtained by the alkylborylation of thioketones [3] in the presence of the Pr3B-O2-CH3OH system used to generate thiyl radicals from mercaptans [4,5] cyclize to give spirothiolanes (II). The experimental procedure was analogous to that given in our previous work [5].

Synthesis of 2-substituted methylenecycloalkanes from 1-(dialkyl-borylmethyl)cycloalkenes

ConclusionsWe have developed a novel general method for the preparation of 2-substituted methylenecycloalkanes, which is based upon the allylboration of carbonyl compounds and alkoxyacetylenes by means of hitherto unknown cycloalkenylmethyl(dialkyl)boranes.