ORGANIC SYNTHESES VIA TRANSITION-METAL COMPLEXES .66. 2-AMINOPYRROLES BY METATHESIS OF (BETA-AMINOVINYL)CARBENE COMPLEXES OF CHROMIUM AND TUNGSTEN WITH ISOCYANIDES

(Beta-Aminovinyl)carbene complexes L(n)M=C(OEt)-CH=C(Ph)-NHR (Z)-3a-d [L(n)M=(CO)5Cr, (CO)5W; R=Ph, iPr, CH2Ph] react with two equivalents of isocyanides R1-NC 5 (R=c-C6H11, t-C4H9) to give 2-amino-3-ethoxypyrroles 7a-e and isocyanide complexes LnM(R1-NC) 6. The reaction involves the formation of ketenimine complexes by metathesis. There are key intermediates. The pyrroles 7 are easily oxidized by air to give amidines PhN(R1NH)C-C(OEt)=CH-COPh 9 (R=c-C6H11, t-C4H9). 7a forms a Michael adduct 10a as well as a Diels-alder adduct 11a with N-phenylmaleimide. A 1-amion-2-ethoxybenzene 12a is obtained from 11a by elimination of aniline.