A useful methoxyvinyl cation equivalent: alpha-t-butyldimethylsilyl-alpha-methoxyacetaldehyde

作者：McCune Christopher D; Beio Matthew L; Friest Jacob A; Ginotra Sandeep; Berkowitz David B^*

来源：Tetrahedron Letters, 2015, 56(23): 3575-3579.

DOI：10.1016/j.tetlet.2015.02.122

• Methoxyvinylation
• Chelation control
• Peterson elimination
• alpha-Silyl-alpha-methoxyacetaldehyde
• Steric Felkin-Anh model
• Rieke magnesium

Described are the synthesis and application of alpha-t-butyldimethylsilyl-alpha-methoxyacetaldehyde as a formal methoxyvinyl cation equivalent. Addition of Grignard reagents to the title aldehyde, followed by treatment of the intermediate beta-hydroxysilanes with KH, gives good yields of largely Z-methoxyvinylated products. Assuming a Peterson-like elimination mechanism, one can infer that the Grignard addition proceeds with high syn selectivity. These results are consistent with a chelation control model involving coordination to the a-methoxy group in the title aldehyde rather than an alternative stereoelectronic Felkin-Anh-type model. It must be noted that a steric Felkin-Anh model also accounts for the observed stereochemistry. All told, the title reagent can be employed to efficiently append a Z-configured methoxyvinyl group to an appropriate R-M species, in two steps.

• 出版日期2015-6-3