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 parent 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 reactions of 2-aryl-substituted 1,3-dithianes bearing electron-donating groups on the benzene ring with DDQ afforded thioesters along with aldehydes. 1,3-Dithiolanes derived from aromatic aldehydes were transformed 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-benzaldehyde diphenyl dithioacetals which gave the corresponding aldehydes. Selective cleavage reactions of 1,3-dithiane in the presence of 1,3-dithiolane or diphenyl dithioacetal have been investigated.