Regio- and Stereocontrol Elements in Rh(II)-Catalyzed Intramolecular C−H Insertion of α-Diazo-α-(phenylsulfonyl)acetamides
作者:Cheol Hwan Yoon、Michael J. Zaworotko、Brian Moulton、Kyung Woon Jung
DOI:10.1021/ol016647l
日期:2001.11.1
see text]. Intramolecular C-H insertion reaction of alpha-diazo-alpha-(phenylsulfonyl)acetamides proceeded with high regio- and stereoselectivities to afford highly functionalized gamma-lactams predominantly or exclusively. The high regioselectivity was attributed to the use of the phenylsulfonyl moiety, which altered electron density at the carbenoid center and exerted a steric effect during the insertion
The axial coordination of N-heterocycliccarbene ligands onto dirhodium(II) complexes was examined, together with its role in the intramolecular C-H insertion reactions of α-diazoacetamides. The formation of a decarbonylated product occurs by a free-carbene mechanism in which the structures of the catalyst and the acetamide play a decisive role. carbenoids - carbenecomplexes - catalysis - diazo compounds
Intramolecular C–H insertion using NHC–di-rhodium(II) complexes: the influence of axial coordination
作者:Luis F.R. Gomes、Alexandre F. Trindade、Nuno R. Candeias、Pedro M.P. Gois、Carlos A.M. Afonso
DOI:10.1016/j.tetlet.2008.10.054
日期:2008.12
insertion of diazo-acetamides catalysed by di-rhodium(II) complexes can be highly influenced by the axial ligand on the di-rhodium(II) complex. Axially monocoordinated NHC–Rh2(OAc)4 complexes have a distinct reactivity from the parent Rh2(OAc)4 complex affording the cyclisation products in different rates and selectivities. Surprisingly, a new reaction mode emerged when using these complexes which led
amide carbeneinsertion into C–H bonds, yielding γ-lactams with 91% ee in up to 99% yield. This reaction uses a ruthenium(II) phenyl oxazoline (Ru(II)-Pheox) complex. The catalytic intramolecular carbenetransferreaction to the primary C–H bond proceeds rapidly and selectively compared to that with secondary C–H, benzylic secondary C–H, tert-C–H, or sp2C–H bonds in the presence of 1 mol % Ru(II)-Pheox