Opening of thiiranes: Preparation of orthogonal protected 2-thioglyceraldehyde

Treatment of acrolein diethyl acetal sulfide 8 with methanesulfenyl bromide at low temperature results in an efficient thiirane ring opening to a halo disulfide 9. The bromine in this halo disulfide is easily substituted by s ilver acetate, sodium azide, sodium iodide, and silver nitrate. Treatment o f 9 with tetrabutylammonium acetate yields a novel dehydrohalogenation prod uct 12. Silica gel converts bromide 9 into a disulfide-substituted version of acrolein 15. The orthogonal-protected version of 2-thioglyceraldehyde 13 can be deprotected to a useful form of this aldehyde.