Organotin compounds. 6. Hydrostannation of methyl (E)-disubstituted propenoates with trimethyltin hydride and dimethyltin chlorohydride

Article abstract of DOI:10.1021/om00125a013

A series of (trimethylstannyl)- and (chlorodimethylstannyl)propyl derivatives having the carboxymethyl functional group has been prepared via free radical additions of trimethyltin hydride and dimethyltin chlorohydride to methyl (E)-2,3-disubstituted propenoates giving high yields of mixtures of diastereomeric products. The relationship between the diastereomers obtained in both reactions is demonstrated by quantitative conversion of the (trimethylstannyl)propyl derivatives into the corresponding (chlorodimethylstannyl)propyl derivatives by methyl/chlorine exchange with trimethyltin chloride. The chlorostannyl esters showed intramolecular coordination with the carbonyl group. Evidence concerning the reversibility of the free radical forming step, resulting in a rapid Z → E isomerization of the olefin, is presented. The high predominance of one diastereomer in the product might be governed by the preferred conformation of the intermediate radicals.