Organische Synthesen mit Übergangsmetall‐Komplexen, 59 [1] Cyclobutanimine aus Carbenchrom‐ oder ‐wolfram‐Komplexen, Isocyaniden und Alkenen durch [2 + 2]‐Cycloadditionen intermediärer Ketenimin‐Komplexe; Liganden‐Abspaltung mit Pyridin

Organic Syntheses via Transition Metal Complexes, 59 [1] . – Cyclobutanimines from Carbenechromium or ‐tungsten Complexes, Isocyanides, and Alkenes by [2 + 2]‐Cycloaddition Reactions of Ketenimine Complexes; Ligand Disengagement with Pyridine 10‐Iminotricyclo[5.3.0.0 2,9 ]deca‐3,5‐diene complexes syn/anti ‐ 4 are obtained in yields higher than 90% by the addition of isocyanides RNC 2 [R = c ‐C 6 H 11 ( a ), CH 3 ( b )] to (cycloheptatrien‐1‐ylmethyl)carbene complexes L n M=C(OEt)CH 2 (C 7 H 7 ) 1 [L n M = Cr(CO) 5 ( a ), W(CO) 5 ( b )]. The reactions involve an intermediate formation of ketenimine complexes L n M[RN=C=C(OEt)CH 2 C 7 H 7 ] 3 by the insertion of 2 into the M=C bonds of 1 . Complexes 3 isomerize to give the cyclo‐butanimines 4 by an intramolecular [2 s + 2 a ]‐cycloaddition reaction of the ketenimine to the alkene unit. The structure of anti ‐ 4c has been determined by a crystal structure analysis. Complexes 4 react with pyridine by the fragmentation of the four‐membered ring to yield a tetrahydroazulen‐1‐imine 6 which was hydrolyzed to the corresponding ketone 7;7 is also obtained along an independent route by the photolysis of 1a in the presence of carbon monoxide. The first isolated product of the latter reaction is the tricyclo[5.3.0.0 2,9 ]deca‐3,5‐dienone 9 , which presumably is formed via an intermediate ketene complex N and the tricyclic ketone O; 9 on warming with pyridine rearranges to 7 .