Selective Transformations of a Diprotected 2‐Oxobutanedial

The reactivity of 1,1‐diethoxy‐3‐(1,3‐dithian‐2‐yl)propan‐2‐one, a diacetal of oxobutanedial, and some of its derivatives toward selected reagents has been studied. As expected, hydride and Grignard‐type additions take place at the oxo moiety only and give the corresponding alcohols in good‐to‐excellent yields. Standard reductive amination occurs at the oxo moiety as well, but the reaction was in most cases not selective and furnished the expected amine mixed with 3‐(1,3‐dithian‐2‐yl)‐1,1‐diethoxypropan‐2‐ol. The conversion of the diethyl acetal moiety to an aldehyde group is generally an efficient transformation, but some aldehydes are unstable, making the deprotection useless. If the acetal contains a tertiary alcohol or a benzyloxy moiety, however, stable products are formed in good yields. Attempts to convert the 1,3‐dithiane substituent into an aldehyde group without concomitant decomposition of the product were totally unsuccessful. The chemical potential of this moiety, therefore, has to be utilized at an earlier stage and under different conditions.