Homopyrroles by Metal-Mediated Cycloadditions of (NH)-Enamines to Alkynylcarbene Tungsten Complexes via 1-Metalla-1,3,5-Trienes

Rudolf Aumann; Michael Kößmeier; Klaus Roths; Roland Fröhlich

doi:10.1055/s-1994-23079

Synlett 1994; 1994(12): 1041-1044
DOI: 10.1055/s-1994-23079

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Homopyrroles by Metal-Mediated Cycloadditions of (NH)-Enamines to Alkynylcarbene Tungsten Complexes via 1-Metalla-1,3,5-Trienes

Rudolf Aumann^* , Michael Kößmeier, Klaus Roths, Roland Fröhlich

^*Organisch-Chemisches Institut der Universität Münster, Orléans-Ring 23, D-48149 Münster, Germany

Abstract

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2-Aza-bicyclo[3.1.0]hexenes (2,3-homopyrroles) 3a-g are obtained in 65 - 90 % yields by a novel-type cycloaddition of 4-(NH)amino-pent-3-en-2-ones MeC(NHR)=CH-COMe 2a-g (R = C₆H₅, p-Me-C₆H₄, p-MeO-C₆H₄, p-HO-C₆H₄, CH₃, i-C₃H₇, n-C₄H₉) to the alkynylcarbene complex (CO)₅W=C(OEt)C≡CPh 1a. The reaction involves the intermediate formation of 1-tungstena-1,3,5-trienes (CO)₅W=C(OEt)CH=CPh-C(COMe)=C(NHR)Me (Z)-4, which have been isolated in 88 - 93 % yields. Thermolysis of (Z)-4 in unpolar solvents yields homopyrroles 3. But in polar solvents or in the presence of a base (e.g. triethylamine) 1,2-dihydropyridin-2-ylidene complexes 6 and pyran-2-ylidene complexes 7 are formed by the elimination of ethanol.

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