Ring expansion of cyclenones: an unusual regioselectivity
作者:A. Krief、J. L. Laboureur
DOI:10.1039/c39860000702
日期:——
Various cyclenones have been homologated by a two-step sequence involving a reaction with α-selenoalkyl-lithium compounds and further reaction of the resulting β-hydroxyselenides with thallium(I) ethoxide in chloroform; an unusually high propensity of the alkyl groups to migrate in place of the vinyl moiety has been observed.
Aerobic Dehydrogenation of Cyclohexanone to Cyclohexenone Catalyzed by Pd(DMSO)<sub>2</sub>(TFA)<sub>2</sub>: Evidence for Ligand-Controlled Chemoselectivity
作者:Tianning Diao、Doris Pun、Shannon S. Stahl
DOI:10.1021/ja4031648
日期:2013.6.5
The dehydrogenation of cyclohexanones affords cyclohexenones or phenols via removal of 1 or 2 equiv of H-2, respectively. We recently reported several Pd-II catalyst systems that effect aerobic dehydrogenation of cyclohexanones with different product selectivities. Pd(DMSO)(2)(TFA)(2) is unique in its high chemoselectivity for the conversion of cyclohexanones to cyclohexenones, without promoting subsequent dehydrogenation of cyclohexenones to phenols. Kinetic and mechanistic studies of these reactions reveal the key role of the dimethylsulfoxide (DMSO) ligand in controlling this chemoselectivity. DMSO has minimal kinetic influence on the rate of Pd(TFA)(2)-catalyzed dehydrogenation of cyclohexanone to cyclohexenone, while it strongly inhibits the second dehydrogenation step, conversion of cyclohexenone to phenol. These contrasting kinetic effects of DMSO provide the basis for chemoselective formation of cyclohexenones.
KRIEF, A.;LABOUREUR, J. L., J. CHEM. SOC. CHEM. COMMUN., 1986, N 9, 702-704