Synthesis of dineophyltin dihydride and stereoselective hydrostannation of alkynes and (E)-trisubstituted alkenes

摘要

This paper reports the synthesis of dineophyltin dihydride (3) following two procedures. The four steps synthesis starting from benzyl chloride and Sn was shown to be more convenient than the two step direct alkylation of SnCl _4. The study of the free radical hydrostannation of mono- and disubstituted acetylenes with hydride 3 shows that they are stereoselective and that the stereoisomers obtained in higher proportion are stable and easily separated by column chromatography. Some preliminary studies on the chemical reactivity of the new divinylsubstituted dineophyltin compounds in Stille reactions are also informed. Radical hydrostannatation of (E)-trisubstituted ethylenes with 3 did not succeed probably due to steric factors. The preparation of dineophyltin bromohydride (27) is also reported. Radical addition of 27 to methyl (E)-2,3-disubstituted propenoates leads to mixtures of the corresponding erythro and threo adducts in diastereomeric excesses (d.e.) in the range of 74-90%.