Distannoxanes with isocyanates

Addition reactions of organotin alkoxides and distannoxanes with compounds containing multiple carbon-nitrogen bonds affording a variety of organotin-nitrogen compounds have been reported (92). The first reactions of this kind studied were additions of trialkyltin alkoxides to alkyl and aryl isocyanates, e.g.. 

Chiral alcohols are smoothly transformed to the corresponding (f )-[l-(l-naphthyl) ethyljcarbamates by treating with (f )-l-(-naphthyl)ethyl isocyanates in the presence of distannoxane catalyst (Eq. 103) [146],... 

The tetraalkyldistannoxanes, XR2SnOSnR2Y, have been reported to be active as catalysts, particularly when X and/or Y is NCS, when a template effect may operate.51 The tetraalkyldistannanes, (R C02)R2SnSnR2(02CR ), can serve as latent catalysts they are not themselves catalytic, and mixtures with the alcohol and isocyanate have a long pot life, but on exposure to air, aerobic oxidation gives the distannoxanes (R C02)R2Sn0SnR2(02CR ) which are catalytic.52... 

Combination of a nonracemic isocyanate and a l,3-disul)sliluted distannoxane has provided a new method for determination of the optical purity of chiral alcohols (Scheme 12.174) [316]. When a chiral alcohol was reacted with commercially available (l )-l-(l-naphthyl)efhyl isocyanate in the presence of 1,3-disubstituted distannoxane, formation of the desired carbamates occurred rapidly, with acid-labile functional groups such as ester, THP and /Miydroxyketone remaining intact. Subsequent HPLC analysis of the resulting carbamate revealed a pair of well-separated peaks of diastereomers derived from both enantiomeric alcohols. 

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