Dirhodium(II)-catalysed CH insertion on α-diazo-α-phosphono-acetamides in an ionic liquid
摘要:
alpha-Phosphono-lactams were obtained, with high regio and stereo selectivities via Rh-2(OAC)(4)-catalysed intramolecular C-H insertion in an ionic liquid. This system proved to be highly efficient over 5-6 cycles. (C) 2003 Elsevier Ltd. All rights reserved.
Asymmetric Intramolecular CH Insertion of α-Diazoacetamides in Water by Dirhodium(II) Catalysts Derived from Natural Amino Acids
作者:Nuno R. Candeias、Carolina Carias、Luis F. R. Gomes、Vânia André、M. Teresa Duarte、Pedro M. P. Gois、Carlos A. M. Afonso
DOI:10.1002/adsc.201200101
日期:2012.11.12
The asymmetricdirhodium(II)-catalyzed intramolecular CH insertion of α-diazo acetamides in water is described for the first time. The use of natural α-amino acids as chiral ligands allowed the preparation of novel dirhodium(II) homochiral complexes by a simple procedure consisting of the in situ ligand exchange starting from dirhodium tetraacetate. The catalytic system was further reused up to 7 cycles
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
C−H Carbene Insertion of α-Diazo Acetamides by Photolysis in Non-Conventional Media
作者:Nuno R. Candeias、Pedro M. P. Gois、Luis F. Veiros、Carlos A. M. Afonso
DOI:10.1021/jo800980c
日期:2008.8.1
Light from a mercury vapor high-pressure lamp was used to induce the photolytic decomposition of alpha-diazo acetamides in hexane and in nonconventional media such as water or a film. The corresponding beta- and/or gamma-lactams were obtained in reasonable yields and in some cases with good diastereoselectivities with no need to use a metallic catalyst. Experimental studies on chiral substrates demonstrated the occurrence of insertion with retention of configuration.
Rh(II)-Catalyzed Intramolecular C−H Insertion of Diazo Substrates in Water: Scope and Limitations
作者:Nuno R. Candeias、Pedro M. P. Gois、Carlos A. M. Afonso
DOI:10.1021/jo060397a
日期:2006.7.1
Preferential Rh(II) carbenoid intramolecular C-H versus O-H insertion derived from R-diazo-acetamides can be achieved in water by using an appropriate combination of the catalyst and amide groups, which creates a larger hydrophobic environment around the reactive carbenoid center.