Stable α-heteroatom-free dialkylcarbenes: a DFT study

Abstract

The stability of the singlet dicyclopropylcarbene (DE S-T = 15.3 kcal/mol, 1) is increased not only by cyclization to 2,5-dicyclopropylcyclopentanylidene (DE S-T = 20.3 kcal/mol, 2), but even more so by unsaturation to 2,5-dicyclopropylcyclopentenylidene (DE S-T = 22.5 kcal/mol, 3). In a further attempt to pave the way toward synthesis of new stable dialkylcarbenes, we introduced different substituents on the a-cyclopropyls of 3, where the stability was increased over twice of 1 (DE S-T = 37.8 kcal/mol) for 2,5-bis(2,3-dihydroxycyclopropyl)-3,4-dinitrocyclopentenylidene, 3 OHÀNO 2 .

Interplay of thermochemistry and Structural Chemistry, the Journal (volume 22, 2011, issues 1–3) and the discipline

“…Kassaee and Momeni [46] used DFT to study stabilization of the singlet relative to the triplet of dicyclopropylcarbene through cyclization and unsaturation. Stabilization of dicyclopropylcarbene by cyclization to 2,5-dicyclopropylcyclopentanylidene is increased by 84.9 kJ mol -1 and by unsaturation to 2,5-dicyclopropylcyclopentenylidene by 94.1 kJ mol -1 .…”