Stereospecific deoxygenation of 1,2-diols to olefins

✍ Scribed by John L. King; Bruce A. Posner; Kwok Tim Mak; Nien-chu C. Yang

• Publisher: Elsevier Science
• Year: 1987
• Tongue: French
• Weight: 203 KB
• Volume: 28
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)96420-7

✦ Synopsis

The 2-dimethylamino-1,3-dioxolane derivatives of 1,2-diols when treated with trifluoromethane sulfonic anhydride and diisopropylethylamine in toluene give the corresponding olefins stereospecifically under mild experimental conditions.

Many methods are known for the conversion of 1,2-diols into the corresponding olefins. 1

Among the notable methods which proceed stereospecifically are a) the desulfurization of 2-thiono. 1,3-dioxolanes,2 b) decompositions of 2-ethoxy-1,3-dioxolanes3 and c) 2-dimethylamino-1,3-dioxolanes,4y5 and d) the base-induced elimination of 2-phenyl-1,3-dioxolanes. 6 Methods a-c are Recently, the reaction was further extended to the synthesis of the heat-labile dioxy-derivative 2, which could not be synthesized by existing deoxygenation procedures. When the base-induced elimination of Z-phenyl-1.3-dioxolanes6 was applied to lo, the phenyldioxolane fragmented to yield phenol and benzene instead.7d

The mechanism of formation of olefins from dioxolanes has been reviewed by Bloch." The formation of these products may be formulaFed via an ylide intermidiate 2 which subsequently fragments to form the olefin. The fragmentation is more important at higher temperatures, while by-product formation becomes more important at lower temperatures. The detailed mechanism and scope of this reaction are currently under investigation.