Carbenoid zincate

Treatment of gem-dibromocyclopropane 34 with Bu3ZnLi from —85 to 0°C generates 1-butylcyclopropylzinc 36 via the 1,2-migration of the zincate carbenoid 35 (equation 27)24. Subsequent Pd°-catalyzed cross-coupling reactions afford cyclopropane... 

Carbomagnesiation of alkenyllithium with allylmagnesium bromide gives rise to gem-bismetallic derivatives 5553. Chlorination of 55 with benzenesulfonyl chloride and treatment with alkyllithium (2 equiv) afford the alkylation product 57 in good overall yield (equation 31)54. A mechanism involving 1,2-migration of the formed intermediate zincate carbenoids 56 has been proposed for this reaction. 

Zincate carbenoids. Reaction of lithium trialkylzincates with a 1,1-dibro-moalkane results in a double insertion into the C-Br bonds to provide a secondary zincate carbenoid.2 These products undergo Pd-catalyzed coupling with acid chlorides or vinyl bromides. 

Generation of homologated organozincs via 1,2-migration of zincate carbenoids... 

C/s-selective alkylation of a gem-dibromocyclopropane via a zincate carbenoid synthesis of r-1 -acetyl-1 -ethyl-f-2-phenylcyclopropane (Structure IS)8 ... 

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