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■ Synthesis and [3+2]Cycloaddition Reaction of 3-[(Trimethylsilylmethylamino)(methylthio)]-methylene-2-coumaranone and -1-methyloxindole: Synthetic Equivalent of Heterocyclic Alkylideneazomethine Ylide as a Novel 1,3-Dipolar Reagent

Yoshinori Tominaga,* Satoshi Takada, and Shinya Kohra

*Faculty of Pharmaceutical Sciences, Nagasaki University, 1-14, Bunkyo-machi, Nagasaki 852-8521, Japan

Abstract

3-[(TrimethyIsilylmethylamino)(methylthio)methylene-2-coumaranone(4a) and -1-methyloxindole (4b), readily prepared by reaction of the corresponding bis(methylthio)methylene-heterocyclic compounds (2a, b) with trimethylsilylmethylamine (3), were found to be syntehtic equivalent of heterocyclic alkylideneazomethine ylides. Reaction of 4a, b with reactive heterodipolarophiles such as aldehydes and ketones in the presence of secium fluoride gave 1,3-dipolar cycloadducts, 3-(2-oxazolidenylidene)-2-coumaranone and -1-methyloxindole derivatives(8a-j, 9a-b), via the 1,3-elimination of (methylthio)trimethylsilane.