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Benzannulation with Metal Carbene Functionalized Alkynes:  Synthesis and Structure of Bimetallic Naphthohydroquinone Complexes Bearing Tricarbonylchromium and Pentacarbonylcarbenetungsten Moieties1

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journal contribution
posted on 06.08.1996 by Oliver Kretschik, Martin Nieger, Karl Heinz Dötz
Pentacarbonyl(1-methoxybenzylidene)chromium(0) (1) undergoes benzannulation upon reaction with ethyl trans-2-(phenylethynyl)cyclopropanecarboxylate (2) and pentacarbonyl[methoxy(trans-2-(phenylethynyl)cyclopropyl)methylidene]tungsten(0) (6) with surprisingly high regioselectivity (>97/3) but lower diastereoselectivity (60−62% de) to give pairs of naphthohydroquinone complexes 3/4 and 7/8 as 4:1 mixtures of diastereomers arising from Cr(CO)3 coordination to one or the other diastereotopic face of the naphthalene skeleton. The minor diastereomer (Rp,Sp,1RS,2RS)-1,2,3,4,9,10-η6-tricarbonyl[ethyl trans-2-(1-((tert-butyldimethylsilyl)oxy)-4-methoxy-2-phenylnaphthalen-3-yl)cyclopropanecarboxylate]chromium(0) (4) and the major diastereomer (RpSp,1SR,2SR)-pentacarbonyl{{trans-2-[1,2,3,4,9,10-η6-(tricarbonylchromium(0))-1-((tert-butyldimethylsilyl)oxy)-4-methoxy-2-phenylnaphthalen-3-yl)]cyclopropyl}methoxymethylidene}tungsten(0) (7) have been characterized by X-ray analysis.

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