Organische Synthesen mit übergangsmetall‐Komplexen, 51. 1‐Metalla‐1,3,5‐triene und 1‐Metalla‐1,3‐dien‐5‐ine von Chrom und Wolfram durch Insertion von Alkinen in MC‐ bzw. CC‐Bindungen von 1‐Metalla‐1,3‐dienen bzw. 1‐Metalla‐1‐en‐2‐inen

Abstract
Organic Syntheses via Transition Metal Complexes, 51. – 1‐Metalla‐1,3,5‐trienes and 1‐Metalla‐1,3‐dien‐5‐ynes of Chromium and Tungsten by Insertion of Alkynes into MC and CC Bonds of 1‐Metalla‐1,3‐dienes and 1‐Metalla‐1‐en‐3‐ynes, respectively1‐Metalla‐1,3,5‐trienes LnMC(NEt2)–C(Me)C(OEt)–CHCHPh (3,4) and LnMC(OEt)– CHC(NEt2) – C(Me)=CHPh [5, LnMCr(CO)5 (a), W(CO)5 (b)] are obtained for the first time from the corresponding 1‐metalla‐1,3‐dienes LnMC(OEt) – CHCHPh (1a, b) under very mild conditions by the insertion of the electron‐rich alkyne Et2N–C  C – Me (2) into the MC and the CC bonds, respectively, of 1. The chelate complex (6b) and the cyclobutenyl carbene complex 7b are isolated as minor side products. 1‐Metalla‐1,3‐dien‐5‐ynes LnMC(NEt2) – C(Me)=C(OEt) – C  CPh [9, 10, LnMCr(CO)5 (a), W(CO)5 (b)] are formed with high regio‐ and stereoselectivity on insertion of 2 into the MC bonds of 1‐metalla‐1‐en‐3‐ynes 8. X‐ray data are given for the tungsten complex 3b.

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