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Organische Synthesen mit Übergangsmetall‐Komplexen, 63. (β1‐Aminovinyl)carben‐Komplexe und (Alkinyl)aminocarben‐Komplexe von Chrom und Wolfram. — Stereochemie und Isomerisierung

1993; Wiley; Volume: 126; Issue: 2 Linguagem: Inglês

10.1002/cber.19931260220

0009-2940

Rudolf Aumann, Peter Hinterding,

Asymmetric Hydrogenation and Catalysis

Organic Syntheses via Transition Metal Complexes, 63 [1] . — (β1‐Aminovinyl)carbene complexes and (Alkinyl)aminocarbene Complexes of Chromium and Tungsten. — Stereochemistry and Isomerization (Alkinyl)alkoxycarbene complexes L n MC(OEt)–CCR 3 [L n MCr(CO) 5 , W(CO) 5 ; RPh, n Bu, SiMe 3 ] react with primary amines H 2 NR 1 4 (R 1 Me, i Pr, allyl, CH 2 Ph, CHMePh) to give (β1‐aminovinyl)carbene complexes L n MC(OEt)–CHCR‐NHR 1 ( Z )‐ 5 (by a Michael‐type 3‐addition) together with (alkinyl)aminocarbene complexes anti ‐ 6 (by a 1‐aminolysis). The product ratio ( Z )‐ 5 / anti ‐ 6 is strongly influenced by the reaction temperature: at 20°C ( Z )‐ 5 is obtained as the main product, while at –78°C mainly anti ‐ 6 is formed. Both reactions are stereospecifical; they yield 5 in the ( Z ), and 6 in the anti configuration only. An anti / syn isomerization is achieved by acidic treatment of anti ‐ 6i . The (alkinyl)aminocarbene complex 6a adds EtOH/EtO – albeit much slower than the (alkinyl)alkoxycarbene complex 3a . A NH 2 1‐Enamino carbene complexes (CO) 5 CrC(OEt)–CHC(NH 2 )Ph [( Z )‐ 8a ] is obtained on addition of ammonia to 3a at 90°C.