Organische Synthesen mit übergangsmetall‐Komplexen, 66. 2‐Aminopyrrole durch Metathese von (β‐Aminovinyl)carben‐Chrom‐ und ‐Wolfram‐Komplexen mit Isocyaniden

Organic Syntheses via Transition Metal Complexes, 66 [1] . — 2‐Aminopyrroles by Metathesis of (β‐Aminovinyl)carbene Complexes of Chromium and Tungsten with Isocyanides (β‐Aminovinyl)carbene complexes L n MC(OEt)—CHC(Ph)‐NHR ( Z )‐ 3a—d [L n M = (CO) 5 Cr, (CO) 5 W; R = Ph, i Pr, CH 2 Ph] react with two equivalents of isocyanides R 1 —NC 5 (R = c ‐C 6 H 11 , t ‐C 4 H 9 ) to give 2‐amino‐3‐ethoxypyrroles 7a—e and isocyanide complexes L n M(R 1 —NC) 6 . The reaction involves the formation of ketenimine complexes by metathesis. These are key intermediates. The pyrroles 7 are easily oxidized by air to give amidines PhN(R 1 NH)C—C(OEt)CH—COPh 9 (R = c ‐C 6 H 11 , t ‐C 4 H 9 ). 7a forms a Michael adduct 10a as well as a Diels‐Alder adduct 11a with N ‐phenylmaleimide. A 1‐amino‐2‐ethoxybenzene 12a is obtained from 11a by elimination of aniline.