Solvent effects in thermal (2+ 2) cycloaddition reactions. Intramolecular capture of 1, 4-dipolar intermediates vs.(2+ 2) cycloaddition in reactions of 3-(1-pyrrolidinyl) …

…, J Geevers, WP Trompenaars, S Harkema…

Index: Reinhoudt, David N.; Geevers, Jan; Trompenaars, Willem P.; Harkema, Sybolt; Hummel, Gerrit J. van Journal of Organic Chemistry, 1981 , vol. 46, # 2 p. 424 - 434

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Citation Number: 33

Abstract

34 1-Pyrrolidiny1) thiophenes (1) react as “pseudo” enamines with electron-deficient acetylenes, such as dimethyl acetylenedicarboxylate (DMAD), dicyanoacetylene, and methyl propiolate. In apolar solvents with DMAD (2+ 2) cycloadducts are formed. These cycloadducts (2) isomerize under the reaction conditions to yield thiepins (3), which are also thermally unstable and eliminate sulfur via the isomeric norcaradienes (4) to give the ...