Reaction of aminocarbene complexes of chromium with alkynes. 2. Intramolecular insertions leading to polycyclic lactams

Thermolysis of chromium-containing carbene complexes of the general structure (CO) 5 Cr=C(NR 2 R 3 )-(CH 2 ) n C=C-R 1 has been examined. When nitrogen is part of a strained cycle (R 2 R 3 =(CH 2 ) m , m=2, 3) or in an allylic 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 (R 2 R 3 =(CH 2 ) 3 , n=4, R 1 =Ph), for 18 (R 2 R 3 =(CH 2 ) 3 , n=3, R 1 =Ph), and for 27 (R 2 R 3 =CH 2 CH=CHCH 2 , n=4, R 1 =Ph), which led respectively to 15, 19, and 28, the structures of which could be established by X-ray crystallography