Conveniently prepared as outlined in eq 1.
Treatment of 1-(trimethylsilyl)propyne (2)2 with 1.1 equiv of
diisobutylaluminum hydride (25??C, 21 h) and 1.1 equiv of
methyllithium (0??C, 0.5 h) in ether¨Chexane,2 followed by reaction of the resulting vinylalanate with anhydrous carbon
dioxide,3 yields (Z)-2-(trimethylsilyl)-2-butenoic acid (3) in
68% yield. Exposure of the potassium salt of this acid (4) to
1.1 equiv of oxalyl chloride in pentane containing a catalytic
amount of N,N-dimethylformamide (0¨C25??C, 1.5 h) then produced a mixture of the acid chloride (5) and its geometric isomer, which was dehydrohalogenated without further purification. A solution of (5) in pentane was added dropwise over
1¨C2 h to a solution of 0.9 equiv of triethylamine in pentane at 25??C, and the resulting mixture was heated at reflux for
15¨C24 h and then filtered with the aid of pentane. Solvent was
evaporated at ?50??C (0.5 mmHg), and the residue was distilled at 25??C (1 mmHg) and then again at 5 mmHg into a receiver cooled at ?78??C. In this manner a yellow-green liquid of
(trimethylsilyl)vinylketene (1) was obtained in 39¨C50% overall
yield (from 3).
