Anomalous intramolecular C-H insertion reactions of rhodium carbenoids: factors influencing the reaction course and mechanistic implications.
J Org Chem
; 69(11): 3886-98, 2004 May 28.
Article
em En
| MEDLINE
| ID: mdl-15153022
ABSTRACT
The intramolecular insertion of rhodium carbenoids into the alpha-C-H bonds of allylic ethers to give 3(2H)-furanones has been explored. Cyclopropanation is favored irrespective of the complex used for carbenoid generation or the substitution pattern of the allylic ether, unless a substituent is placed on the tether connecting the ether to the alpha-diazo ketone. Unusual acetal products resulting from an anomalous C-H insertion process are obtained in addition to the expected 3(2H)-furanones formed by conventional carbenoid C-H insertion. These acetals are the favored C-H insertion products in certain circumstances and particularly in cases where carbenoid generation is effected using an electron-deficient rhodium complex. Experiments with simple deuterium labeled substrates reveal that anomalous C-H insertion products arise by a mechanism that is distinct from that leading to the formation of conventional C-H insertion products. The formation of acetal products and the outcome of reactions performed using deuterium-labeled substrates suggest that a mechanism involving hydride migration to the rhodium center of the carbenoid is operative.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
J Org Chem
Ano de publicação:
2004
Tipo de documento:
Article
País de afiliação:
Reino Unido