of highly enantioenriched tetrasubstituted alkene architectures from isatin-based Morita-Baylis-Hillman carbonates and allylic derivatives, under the cooperative catalysis of a tertiary amine and a chiral iridium complex. The success of the switchable construction of the tetrasubstituted alkene motif relies on the diastereodivergent 1,3-oxo-allylation reaction between N-allylic ylides and chiral π-allyliridium
reactions have achieved great success for accessing carbon–carbon and carbon–heteroatom bonds during the past decade, metal-free acceptorless dehydrogenative cross coupling is still scarce and highly desirable. Herein we report a robust metal-free acceptorless dehydrogenative cross-coupling for both carbon–heteroatom and carbon–carbonbondformation. By synergistic catalysis of the organophotocatalyst
scope. Herein, we disclose a practical copper-mediated direct intramolecular cyclopropanation of distal olefinic acetate to synthesize cyclopropane-fused γ-lactones and lactams. This cascade reaction is postulated to proceed through a hydrogen atom transfer event induced radical cyclization and copper-mediated cyclopropanation sequence. The protocol features high atom- and step-economy, excellent diastereoselectivity
N-Heterocyclic Carbene-Mediated Oxidative Esterification of Aldehydes: Ester Formation and Mechanistic Studies
作者:Biswajit Maji、Seenuvasan Vedachalan、Xin Ge、Shuting Cai、Xue-Wei Liu
DOI:10.1021/jo200275c
日期:2011.5.6
An unexpected N-heterocyclic carbene-catalyzed esterification of alpha,beta-unsaturated aldehydes including aromatic aldehydes with reactive cinnamyl bromides in the presence of air oxygen or MnO2 as an oxidant is described. In the presence of oxygen, halogenated and electron-deficient aldehydes react smoothly to furnish esters in good yields. Great efforts have been made on mechanistic studies to deduce a plausible mechanism, based on the experimental results and isotopic labeling experiment.
Burton, Journal of the Chemical Society, 1928, p. 1656