Abstract
The capability of silicon in directing decarbonylation of aldehydes was investigated. In the presence of 1,2-ethanedithiol and BF 3 ·OEt 2 , trans-6-(oxomethyl)-5-(trimethylsilyl)bicyclo[4.4.0]dec-1-en-3-one (2) and trans-6-(oxomethyl)-5-(trimethylsilyl)bicyclo[4.4.0]dec-1-en-3-one 3-(ethylene dithioacetal) (4) were decarbonylated to give cis-5-(trimethylsilyl)bicyclo[4.4.0]dec-1-en-3-one 3-(ethylene dithioacetal) (7), trans-5-(trimethylsilyl)bicyclo[4.4.0]dec-1-en-3-one 3-(ethylene dithioacetal) (8), and 5-(trimethylsilyl)bicyclo[4.4.0]dec-1 (6)-en-3-one 3-(ethylene dithioacetal) (9) in a ratio of 14:1.0:4.0 and 12:1.0:2.5, respectively, in total yields of 81-99%. Under the same reaction conditions, cis-6-(oxomethyl)-5-(trimethylsilyl)bicyclo[4.4.0]dec-1-en-3-one (1) gave a mixture of cis-6-(oxomethyl)-5-(trimethylsilyl)bicyclo[4.4.0]dec-1-en-3-one 3-(ethylene dithioacetal) (3), cis-6-(dimethoxymethyl)-5-(trimethylsilyl)bicyclo[4.4.0]dec-1-en-3-one 3-(ethylene dithioacetal) (11), and cis-6-(oxomethyl)-5-(trimethylsilyl)bicyclo[4.4.0]dec-1-en-3-one 3,6-bis(ethylene thioacetal) (12); no decarbonylation products were formed. Results from 13 C NMR spectrometry indicate that the Me 3 Si and the formyl groups are nearly trans coplanar in 2 and 4. Such alignment as well as sulfur atoms at C-3 is necessary for the Me 3 Si group to direct the C-CHO bond cleavage. © 1989 American Chemical Society.