Radical cyclization in heterocycle synthesis. 12. Sulfanyl radical addition-addition-cyclization (SRAAC) of unbranched diynes and its application to the synthesis of A-ring fragment of 1 alpha,25-dihydroxyvitamin D-3
O. Miyata et al., Radical cyclization in heterocycle synthesis. 12. Sulfanyl radical addition-addition-cyclization (SRAAC) of unbranched diynes and its application to the synthesis of A-ring fragment of 1 alpha,25-dihydroxyvitamin D-3, CHEM PHARM, 49(2), 2001, pp. 213-224
Sulfanyl radical addition-addition-cyclization (SRAAC) of unbranched diynes
proceeded smoothly to give cyclized exo-olefins, while the sulfanyl radica
l addition-cyclization-addition (SRACA) of diynes having a quaternary carbo
n gave cyclized endo-olefins. This method was successfully applied to the s
ynthesis of A-ring fragment of 1 alpha ,25-dihydroxyvitamin D-3.