Deprotection of 1,3-dithianes by antimony pentachloride via single electron transfer processes
作者:Masaki Kamata、Hisashi Otogawa、Eietsu Hasegawa
DOI:10.1016/0040-4039(91)80123-n
日期:1991.12
A variety of 1,3-dithianes was converted to the corresponding carbonyl compounds in good yields when those substances were treated with antimonypentachloride in methylene chloride. Single electron transfer from dithianes to antimonypentachloride was proposed as an initiation step of the reaction.
Photoreactions of various dithioacetals and ketals using tris(p-chlorophenyl)pyrylium perchlorate as a sensitizer were studied. Irradiation (λ&>360 nm) of dichloromethane solutions containing dithioacetals or ketals and pyryliumsalt afforded the corresponding carbonyl compounds in good to excellent yields in the presence of molecular oxygen.
Methyltriphenylphosphoniumtribromide acts as an efficient mild dethioketalization reagent with high selectivity for 2-phenyl and 2-vinyl 1,3-dithiannes versus 2-alkyl 1,3-dithiannes and without any secondary brominationreaction of the investigated substrates. The reaction was also successful with trimethylphenylammonium tribromide.
The reaction of dithioacetals with 30% hydrogen peroxide in the presence of catalytic amounts of tantalum(V) and iodide ion effectively produced carbonyl compounds in high yields. Dithioacetals also can be deprotected using the niobium(V) catalyzed oxidation of iodide ion by hydrogen peroxide under mild conditions.