POLYMETHYLATED AND POLY(TERT)BUTYLATED DIPHENYLCARBENES - GENERATION,REACTIONS, KINETICS, AND DEUTERIUM-ISOTOPE EFFECTS OF STERICALLY CONGESTED TRIPLET CARBENES
H. Tomioka et al., POLYMETHYLATED AND POLY(TERT)BUTYLATED DIPHENYLCARBENES - GENERATION,REACTIONS, KINETICS, AND DEUTERIUM-ISOTOPE EFFECTS OF STERICALLY CONGESTED TRIPLET CARBENES, Journal of the American Chemical Society, 119(7), 1997, pp. 1582-1593
Dimesitylcarbene (2a) was shown to decay by undergoing dimerization an
d to have a half-life of 160 ms, some 5 orders of magnitude longer-liv
ed than diphenylcarbene. Didurylcarbene (2b) was twice as long-lived a
s 2a, while decamethyldiphenylcarbene (2c) decayed mainly unimolecular
ly by abstracting Il from the o-methyl group and became shorter-lived
than 2b. 2,4,6-Tri(tert-butyl)diphenylcarbene (14) decayed unimolecula
rly almost exclusively by abstracting H from the o-tert-butyl group an
d showed the lifetime of 125 mu s. The Arrhenius plot for H and D abst
raction of 2c and 14 gave data consistent with a classical atom-transf
er reaction, although the kinetic parameters are very different betwee
n the two systems.