SYNTHESIS OF CHIRAL ORGANOTIN REAGENTS - DIELS-ALDER-REACTIONS OF METHYL 3-(TRIPHENYLSTANNYL)ACRYLATE - SYNTHESIS OF DIPHENYL(3-SUBSTITUTEDBICYCLO[2.2.1]HEPTAN-2-YL)TIN HYDRIDES

Cyclopentadiene undergoes Diels-Alder reactions with methyl (E)- and ( Z)-3-(triphenylstannyl)acrylates 5 and 6 to give the endo-cycloadduct 9, and a mixture of the exo- and endo-isomers 10 and 11, respectively, The endo-product 9 is reduced to the alcohol 12 which is protected as its methyl ether 13, Attempts to remove one of the phenyl substituent s from the tin using iodine are complicated by destannylation to the t ricyclic iodide 14, However, after hydrogenation, treatment with 1 mol equivalent of iodine gives the tin iodide 17 which is reduced to the tin hydride 18, The hydroxyalkyltin hydride 21 is similarly prepared. The unsaturated tin hydrides 24 and 26 have been prepared by reduction of the Diels-Alder adducts 23 and 25 obtained from cyclopentadiene an d methyl (Z)-3-(chlorodiphenylstannyl)acrylate. The tin hydrides 18 an d 21 are found to undergo free-radical reactions as exemplified by add ition to methyl propiolate and reductive dehalogenation of the iodo la ctone 30.