Organic Sonochemistry. Ultrasonic Acceleration of the Reaction of Dicarbonyls with Trimethylchlorosilane in the Presence of Zinc

摘要

Ultrasonic waves increase the rates and the yields of the reactions of some alpha dicarbonyls towards zinc and trimethylchlorosilane to give bis(trimethylsiloxy) alkenes. 1,2-bis(trimethylsiloxy) alkenes, typically prepared by modifications of the acyloin condensation, are valuable synthetic intermediates for preparing a variety of compounds. Modifications notwithstanding, the acyloin condensation is useful only for the preparation of symmetrical bis(siloxy) alkenes. This limitation is circumvented by submitting unsymmetrical alpha-diketones to reductive silylation. Of these the most convenient example is the preparation of 1,2-bis(trimethylsiloxy) alkenes recently described by Rasmussen and coworkers in which zinc, trimethylchlorosilane and an alpha-diketone were stirred in ether for 15 hours. The beneficial effects (i.e., shorter reaction times at lower temperatures, higher yields and narrower product distribution) of ultrasonic waves on a broad spectrum of chemical reactions have been reported by several research groups. Keywords: Ultrasound, Zinc, Ketones, Dicarbonyls, Trimethylchlorosilane, Reprints.