Публикации

A convenient methodology was developed for a very accurate calculation of 13C NMR chemical shifts of the title compounds. GIAO calculations with density functional methods (B3LYP, B3PW91, PBE1PBE) and 6-311+G(2d,p) basis set predict experimental chemical shifts of 3-ethynylcyclopropene (1), 1-ethynylcyclopropane (2) and 1,1-diethynylcyclopropane (3) with high accuracy of 1–2 ppm. The present article describes in detail the effect of geometry choice, density functional method, basis set and effect of solvent on the accuracy of GIAO calculations of 13C NMR chemical shifts. In addition, the particular dependencies of 13C chemical shifts on the geometry of cyclopropane ring were investigated.

An efficient methodology was developed for performing palladium-catalyzed E–E (E = S, Se) bond addition to alkynes under solvent free conditions. Compared to reaction in solvent significant enhancement of reaction rate, improved efficiency and remarkable catalyst stability were observed under solvent free conditions. The addition reactions were carried out with high stereoselectivity and yields in a short reaction time.

Solvent-free palladium-catalyzed addition of diaryl disulfides and diselenides to terminal alkynes makes it possible to achieve high stereoselectivity and almost 100% yields in ≈10 min using only 0.1 mol.% catalyst. Both Pd(PPh ₃)₄ and easily available Pd(OAc)₂ and PdCl₂ can be used in the reaction with an excess of triphenylphosphine. The catalyst and triphenylphosphine are readily recycled for repeated use. The study of the mechanism of the solvent-free catalytic reaction indicates that the process involves binuclear palladium complexes.