ИСТИНА

Ionic association of derivatives 1 in the solutions of diethyl ether, THF, HMPA has been studied by UV-Vis spectrophotometry, and both 13C and 1H NMR. 13C NMR data and semiempirical MNDO calculations have shown that the structure of contact (CIP) and solvent separated (SSIP) ion pairs, and free carbanions shifts from propargilic to allenylic with the decrease of delocalizing ability of R1, R2, and R3. Alkylation of derivatives 1 leads to mixtures of acetylenic 2 and allenic 3 products. The regioselectivity of alkylation of derivatives 1 varies in accord with structural changes in carbanions depending on R1, R2, counterion, and the type of ionic species. Benzylation of derivatives 1 occurs by both polar and SET pathways. The contribution of SET increases with the growth of electron-withdrawing ability of substituents in benzyl halides, and leads to a substantial decrease of yield of acetylenic products. Trimethylsilylation, trimethylstannylations, and protonation of derivatives 1 yield allenes as single products.