REACTION OF AMINOCARBENE COMPLEXES OF CHROMIUM WITH ALKYNES .2. INTRAMOLECULAR INSERTIONS LEADING TO POLYCYCLIC LACTAMS

Thermolysis of chromium-containing carbene complexes of the general st ructure (CO)5Cr=C(NR2R3)-(CH2)(n)C=C-R1 has been examined. When nitrog en is part of a strained cycle (R2R3 = (CH2)m, m = 2, 3) or in an ally lic position, or if m > 4, then the insertions of the triple bond and of CO, followed by a rearrangement to tricyclic lactams, are observed. This was the case for 14 (R2R3 = (CH2)3, n = 4, R1 = Ph), for 18 (R2R 3 = (CH2)3, n = 3, R1 = Ph), and for 27 (R2R3 = CH2CH--CHCH2, n = 4, R 1 = Ph), which led respectively to 15,19, and 28, the structures of wh ich could be established by X-ray crystallography. However C-H bond ac tivations, followed by CO insertion, were observed for 31 (R2R3 = CH2C H=CHCH2, n = 3, R, = Me), which gave 32, and for (CO)5Cr=C(Et)N-(Me)(C H2)3C=C-Ph (69) and (CO)5Cr=C(Me)N(Me)(CH2)3C=C-Ph (72), in which the triple bond is tethered to nitrogen and which led to the cyclopentenon es 70 and 73. Finally, double CO insertions, confirmed by an X-ray str ucture determination on 60 were observed for complexes 14, 18, 22, and 58, derived from azetidine and from methylaziridine, whereas double a lkyne insertions, with or without CO insertion and propene elimination , leading to substituted pyridines and dihydropyridines, were observed for 58 and 65, the aminocarbene complexes derived from methylaziridin e.