Silicon organozincs

This reaction was successfully applied to various hydrazones derived from acyclic or cyclic ketones and extended to a variety of unsubstituted vinylsilanes as acceptors (trialkyl, triphenyl and alkoxy vinylsilanes). In all cases, the regioselectivity of the addition reaction was consistent with the formation of a silicon-stabilized organozinc reagent. 

Because of the stability of iron tricarbonyl diene complexes, conjugated dienals are protected from polymerization when complexed, while other reactions can be carried out at the aldehyde functionaUty. A number of synthetically attractive nucleophilic transformations of the aldehyde can be performed on these complexes. These include, aldol reactions, Michael additions, reactions with organozinc, -silicon, -boron, and -tin... 

Silicon, an element widely used in many facets of organic chemistry [7], was not effectively employed in cross-coupling reactions until 16 years after the first reported transition-metal-catalyzed coupling reactions by Corriu, Kumada, and Tamao [8], Most early developments in this field were achieved by the use of organoboron (1979) [9], organozinc (1977) [10], and organotin (1977) [11] coupling partners (Scheme 7.1). 

Formation of Organozinc Carbenoids. When aromatic aldehydes and certain , -unsaturated carbonyl compounds are treated with zinc and l,2-bis(chlorodimethylsilyl)ethane, an organozinc carbenoid results. This two-electron process is postulated to occur as depicted in eq 8. Sequential reaction of the two silicon atoms with the zinc carbonyl complex and subsequent extrasion of the cyclic siloxane (23) gives rise to the putative organozinc carbenoid... 

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