Lappert’s stannylene

Allylstannanes for use in palladium-catalyzed coupling reactions can readily be made from Lappert s stannylene, [(MesSi N Sn , with an ally 1 bromide or iodide. The reaction is immediate at room temperature, and the product can be used without further purification (Equation (92)).258... 

The ability of allyltin halides to extend their coordination sphere allowed the preparation of chiral hypervalent complexes with diamine ligands, which have been efficient in the asymmetric synthesis of homoallylic alcohols with up to 82% ee100. Similarly, a chiral hypervalent allyltin was prepared from a low valent tin (II) catecholate, chiral dialkyl tartrate and ally lie halide101. The allylation of aldehydes and activated ketones proceeded with high enantiomeric excess. Allyltins prepared from Lappert s stannylene and allylic halides were shown to be efficient as well, although the Lewis acid character of the tin atom is much less marked in that case102,103. 

The first landmark syntheses of persistent radicals of the heavier group 14 elements were reported nearly 30 years ago by Lappert s group. ° The first radical of this series, [(Me3Si)2CH]3Sn , was prepared by photolysis of the stable stannylene [(Me3Si)2CH]2Sn with visible light in benzene (Scheme 2.26). ° =... 

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