ORGANIC SYNTHESES VIA TRANSITION-METAL COMPLEXES .44. CONDENSATION OF METHYL CARBENE COMPLEXES WITH ACID-AMIDES BETA-ALKOXYALKENYL CARBENE AND BETA-AMINOALKENYL CARBENE COMPLEXES OF CHROMIUM AND TUNGSTEN - COMPETITION OF CONDENSATION AND INSERTION

Organic Syntheses via Transition Metal Complexes, 441. ‐ Condensation of Methyl Carbene Complexes with Acid Amides: β‐Alkoxyalkenyl‐ and β‐Aminoalkenyl Carbene Complexes of Chromium and Tungsten ‐ Competition of Condensation and Insertion The condensation of the methyl(ethoxycarbene) complexes LnM = C(OEt)CH3 (4) [LnM = Cr(CO)5, W(CO)5] with acid amides RCONR1R2 (5) under the influence of POCl3/Et3N leads stereoselectively to (E)‐β‐aminoalkenyl(ethoxycarbene) complexes LnM=C(OEt)CH=C(R)NR1R2 [(E)‐6] (R = H, aryl, alkyl). A condensation of 4 can also be achieved via amidium salts 11, which are easily available from 5. In this case, (E)‐6 and (E)‐β‐alkoxyalkenyl(ethoxycarbene) complexes LnM=C(OEt)CH = C(R)OEt[(E)‐13] were obtained. Via the cyclic amidium salts 15 and 20 four‐to seven‐membered lactams (E)‐17 and (E)‐21a‐d are accessible. The reaction of 4 with acid amides RCH2CONR1R2 (2) and POCl3/Et3N yields mainly insertion products LnM=C(NR1R2)C(R)=C(OEt)CH3 [(E)/(Z)‐22] and only small amounts of condensation products LnM=C(OEt)CH=C(CH2R)NR1R2 [(E)‐23]. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim