Theoretical estimates of the potential applications of organic phosphazene superbases in the C-vinylation reaction of ketones with acetylene are carried out. It is shown that the product of ethynylation is kinetic; the product of vinylation is thermodynamic. Barriers of kinetic product into thermodynamic one are close in t-Bu-P4 and KOt-Bu. The reaction in t-Bu-P4/DMSO requires temperatures above 80 °C and equimolar amounts of the superbase.

Abstract

This work explores the potential applications of organic phosphazene superbases in the C-vinylation reaction, a process typically associated with inorganic superbases such as MOt-Bu/DMSO and MOH/DMSO (M = K, Na). For the first time, the mechanism of C-vinylation of acetone with phenylacetylene in the presence of t-Bu-P4/DMSO was studied using quantum chemical methods. It has been demonstrated that in the presence of both the organic base t-Bu-P4 and the inorganic bases KOt-Bu or KOH, thermodynamically more stable C-vinylation products are formed from kinetically preferred ethynylation products. The activation barriers for this transformation in the t-Bu-P4/DMSO and KOt-Bu/DMSO systems are similar and estimated to be about 30 kcal/mol, while in the KOH/DMSO system, they are higher. These activation barrier values suggest that the C-vinylation reaction of acetone with phenylacetylene could be carried out in the presence of t-Bu-P4 at high temperatures, above 80 °C.