Versatile,high 2,4-syn dialkyl diastereoselection in the radical debromination of #alpha#-bromo-#alpha#-methyl-#delta#-valerolactones with tri-n-butyltin hydride and a catalytic amount of triethylbornae

摘要

An interesting 2,4-syn dialykyl diastereoselection has been observed in the radical debromination of #alpha#-bromo-#alpha#-methl-#delta#-valerolactones.The reaction of 4-alkyl-2-bromo-3-hydroxy-2-methyl-5-pentanolides with Bu_3SnH and a catalytic amount of Et_3B gave,essentially, a single diastereomer with a 2,4-syn dialkyl relationship,independent of theorientation of the hydroxy substituent at C-3.