Others Organotin Reagents

This ability of allylhalogenotins to extend their coordination sphere allowed the preparation of chiral hypervalent complexes with diamine ligands, which were efficient in the asymmetric synthesis of homoallylic alcohols with up to 82% ee [236]. Similarly, a chiral hypervalent allyltin was prepared from low valent tin catecholate, chiral dialkyltartrate and allylic halide [237]. The allylation of aldehydes and activated ketones proceeded with high enantiomeric excess. 

Other developments involving allyltins supported on solid phase are under study and are shown to proceed with the similar diastereoselectivity to that observed in liquid phase [238]. 

The nucleophilic addition onto aldehydes was also extended to alkynyltributyltins, which were found to be reactive upon transmetallation with catalytic amount of InClj [247]. The direct addition of alkynyltrimethyltins onto j8-alkoxy aldehydes 

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Organomanganese(II) iodides, 210 Organotin reagents, 211 Organovanadium reagents, 219 From carboxylic acids Benzylchlorobis(triphenylphos-phine)palladium(II), 30 From other acyl derivatives Lithium o-lithiophenoxide, 166 Organomanganese(II) iodides, 210 From 1,2-diols or 1,2-amino alcohols Diethoxy triphenylphosphorane, 109... 

Despite the unique synthetic possibilities offered by organotin reagents, their use in the chemical industry has steadily declined in recent years as a result of perceived toxicity and environmental concerns associated with disposal of tin wastes.30-31 Consequently, appreciable efforts have been made to develop heavy metal-free alternatives based on silicon, germanium, or phosphorus chemistry. Other strategies have been applied to immobilize the tin reagents or to reduce their usage to less than stoichiometric amounts. 

Silver BINAP complex was used as well by Yanagisawa and coworkers . The particular feature of this catalyst is the marked anti selectivity when nsing crotyltins, regardless of whether the donble bond is (E) or (Z). This selectivity is explained by a fast transmetaUation step between the chiral complex and the organotin reagent, followed by the addition on the carbonyl gronp via a cyclic transition state. This reaction has been extended to other organometallics snch as 2,4-pentadienylstannanes . 

Hi. The monomer polymerization route. Compared with the resin-functionalization route, the homo- and copolymerization of organotin-containing monomers permits one to influence the polymer resin structure to a greater extent. In principle, it is possible to prepare gel-type, macroporous, microporous or nonporous polymers. The pore structure, tin loading, solubility and other factors which influence the reactivity of the polymer-supported organotin reagents can be controlled by appropriate... 

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