Evidence for Formation of a Co–H Bond from (H<sub>2</sub>O)<sub>2</sub>Co(dmgBF<sub>2</sub>)<sub>2</sub> under H<sub>2</sub>: Application to Radical Cyclizations
作者:Gang Li、Arthur Han、Mary E. Pulling、Deven P. Estes、Jack R. Norton
DOI:10.1021/ja306037w
日期:2012.9.12
Under H-2, the radical cyclization of appropriate dienes can be catalyzed by cobaloximes. H center dot can be abstracted from an intermediate (presumably a cobalt: hydride) by trityl radicals (Ar3C center dot) or by TEMPO. The rate-determining step in these reactions is the uptake of H-2, which is second order in cobalt and first order in hydrogen; the third-order rate constant is 106(3) M-2.s(-1).
Initiating radical cyclizations by H transfer from transition metals
作者:John Hartung、Mary E. Pulling、Deborah M. Smith、David X. Yang、Jack R. Norton
DOI:10.1016/j.tet.2008.10.030
日期:2008.12
diphosphine) can be used to initiate radicalcyclizations by transferring H to activated terminal olefins. CpCr(CO)3H can catalyze reductive cyclizations, with H2 as the ultimate reductant. Appropriate substrates can be assembled by the Morita–Baylis–Hillman reaction of methyl acrylate with an aldehyde. Six- as well as five-membered rings can be formed, and a tandem cyclization to decalin can be effected.