A process for the cyclopropanation of a substituted alkene, comprising the reaction of the alkene with a carbenoide, generated from dibromomethane and a tri-(C
2
-C
8
)-alkyl aluminium compound, in the presence of a catalytic amount of a metal compound selected from the group consisting of Lewis acids, metallocenes and metal carbonyl complexes. The process advantageously uses transition metal compounds as catalysts and the dibromomethane can be recovered.
The process is especially useful for the preparation of ingredients for the flavour and fragrance industry.
US7777084B2
申请人:——
公开号:US7777084B2
公开(公告)日:2010-08-17
Transition-Metal-Catalyzed Cyclopropanation of Nonactivated Alkenes in Dibromomethane with Triisobutylaluminum
Catalytic amounts of CuI salts, CpTiCl3, and [CpFe(CO)2]2 are similarly effective. 2-Methylpropane, generated after quench of excess TIBA can be trapped, and excess dibromomethane can be recycled, which makes the method industrially applicable. Solvent-free DIBAH or TIBA reduction of unsaturatedcarbonylcompounds, followed by in situ TIBA cyclopropanation of the unsaturated aluminum alcoholates in