OXIDATIVE REMOVAL OF 1,3-DITHIANE PROTECTING GROUPS BY 2,3-DICHLORO-5,6-DICYANO-P-BENZOQUINONE (DDQ)

A number of 1,3-dithianes have been efficiently converted into the par ent carbonyl compounds in good yields by treatment with 1,5 equiv, of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) in MeCN-H2O (9:1). The r eactions of 2-aryl-substituted 1,3-dithianes bearing electron-donating groups on the benzene ring with DDQ afforded thioesters along with al dehydes, 1,3-Dithiolanes derived from aromatic aldehydes were transfor med to thioesters, whereas 1,3-dithiolanes derived from aliphatic and aromatic ketones were stable under these reaction conditions. Diphenyl dithioacetals were stable except for 4-methoxy- and 3,4-dimethoxy-ben zaldehyde diphenyl dithioacetals which gave the corresponding aldehyde s. Selective cleavage reactions of 1,3-dithiane in the presence of 1,3 -dithiolane or diphenyl dithioacetal have been investigated.