SYNTHESIS AND STRUCTURE OF 3-STANNYLCHOLEST-5-ENE SPECIES

The compounds, 3 alpha- and 3 beta-triphenylstannylcholest-5-ene, 1 an d 2 respectively, have been prepared stereospecifically in reactions o f Ph3SnLi with cholesteryl methane- or toluene-p-sulfonates, and of Ph 3SnCl with the Grignard reagent from cholesteryl chloride, respectivel y, Complete H-1 and C-13 NMR spectral assignments for 1 have been obta ined using HMBC and HMQC techniques: these have been used to aid the C -13 NMR spectral assignments for 2 and 3 alpha- and 3 beta-(InPh3-nSn) cholest-5-enes (n = 1-2) (9-12), Crystal structure determinations of 3 alpha-(IPh2Sn)cholest-5-ene 9 and 3 alpha-(I2PhSn)cholest-5-ene 10 in dicate distorted tetrahedral geometries about the tin centres in both compounds, The Sn-I bond lengths are 2.731(5) Angstrom in 9 and betwee n 2.6979(12) and 2.7173(12) Angstrom in 10. Despite the similarity in the values (ca. 60 degrees) of the dihedral angles, Sn-C(3)-C(2)-C(1) [C(1) aliphatic carbon] and Sn-C(3)-C(4)-C(5) [C(5) olefinic carbon], the values of (3)J[Sn-119-C-13(1)] are about twice the (3)J[Sn-119-C-1 3(5)] values in each of 1, 9 and 10; in contrast, (3)J[Sn-119-C-13(1)] and (3)J[Sn-119-C-13(5)] values are essentially the same in each of 2 , 11 and 12 [Sn-C(3)-C(2)-C(1) and Sn-C(3)-C(4)-C(5) ca, 180 degrees].