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Synthesis 1995; 1995(8): 957-963
DOI: 10.1055/s-1995-4024
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Conjugate Addition Reactions of Functionalized Organozinc and Copper Reagents to (2-Propynylidene)morpholinium Triflates

Martina Brunner, Gerhard Maas*
  • *Fachbereich Chemie, Universität Kaiserslautern, Erwin-Schrödinger-Strasse, D-67663 Kaiserslautern, Germany, Fax +49(731)5022803
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Publication Date:
31 December 2000 (online)

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Organozinc and copper reagents of the type IZnCu(CN)-RC-FG [RC-FG = cyanoalkyl (6a, c), ethoxycarbonylalkyl (6b, d), functionalized aryl (10a-c)] undergo conjugate addition to the (2-propynylidene)morpholinium triflates 1a, b. The expected morpholinoallenes or the tautomeric 1- or 2-morpholino-1,3-dienes cannot be isolated, however. After hydrolytic workup, α,β-unsaturated ketones 7 or 12 are usually obtained. In some cases, 2-acylcyclopent-2-en-1-ones 8 or 2-acylindenones 13 are found, which result from cyclization of the initially formed morpholinoallenes. The 2-morpholino-1,3-dienes 17 can be intercepted in a [4+2] cycloaddition with electron-deficient alkenes, and the cyclohexanones 19 are obtained after hydrolytic workup.

iminium salts - zinc-copper organometallics - morpholinoallenes - 2-morpholino-1,3-butadienes - conjugate addition