REACTION OF AMINOCARBENE COMPLEXES OF CHROMIUM WITH ALKYNES .5. INFLUENCE OF THE RING SIZE ON THE PRODUCT DISTRIBUTION - FORMATION OF PYRROLES FROM PYRROLIDINE AND ITS DERIVATIVE-SUBSTITUTED CARBENE COMPLEXES

A series of aminocarbene complexes of chromium derived from piperidine (1), hexa- and heptamethyleneimine (4) and (8), pyrrolidine (13a-d, R (1) = Me, H, Ph, thienyl), perhydroindole (21), thiazolidine (24a,b, R (1) = Me, Ph), pyrroline (30a,b), and azetidine (33a-e and 36) have be en synthesized and subjected to alkyne insertion reactions. Aminocarbe ne complex 24a-E has been fully characterized by X-ray structure analy sis. Crystal data for 24a-E: C10H9O5NSCr, monoclinic, space group P2(1 )/n, a = 8.3011(9) Angstrom, b = 11.949(1) Angstrom, c = 13.101(2) Ang strom, beta = 95.74(1)degrees, V = 1293(1) Angstrom(3), d(calcd) = 1.4 1 g cm(-3), Z = 4. Whereas complex 1 reacted with diphenylacetylene to give first the ylide complex 2, the thermolysis of which led to the b ridgehead lactam 3, complexes 4, and 8 gave directly the expected brid gehead lactams 6 and 11. The structure of 3 has been determined by X-r ay diffraction. Crystal data for 3: C27H25ON, monoclinic, space group P2(1)/c, a = 10.080(4) Angstrom, b = 11.727(3) Angstrom, c 18.014(6) A ngstrom, beta = 102.40(3)degrees, V = 2080(14) Angstrom(3), d(calcd) = 1.21 g cm(-3), Z = 4. In contrast to 1, 4, and 8, all of the new carb ene complexes derived from five-membered cycloamines except 24b gave p yrrole derivatives as the result of the alkyne/CO insertion followed b y migration of an alkyl chain from nitrogen to the carbon atom of the inserted carbonyl group and loss of its oxygen atom. The structures of 14a, the Cr(CO)(3) complex of 15a, and 22 could be unambiguously esta blished by X-ray crystallography. Crystal data for 15: C24H21O3NCr, tr iclinic, space group P1, a = 6.918(1) Angstrom, b = 10.057(1) Angstrom , c = 15.193(2) Angstrom, alpha = 72.410(9)degrees, beta = 84.99(1)deg rees, gamma = 84.66(3)degrees, V = 1001(3) Angstrom(3), d(calcd) = 1.4 0 g cm(-3), Z = 2. For 22: C24H25N, monoclinic, space group P2(1)/n, a = 11.119(3) Angstrom, b = 10.682(2) Angstrom, c = 15.428(3) Angstrom, beta = 102.23(2)degrees, V = 1791(7) Angstrom(3), d(calcd) = 1.21 g c m(-3), Z = 4. Besides these pyrroles, the expected bridgehead lactams 17a-d were isolated from 13a-d together with the lactone complex 18 in the case of 13b. Crystal data for 18: C19H12O5Cr, orthorhombic, space group Pc2(1)/b, a = 10.356(1) Angstrom, b = 12.366(5) Angstrom, c = 1 2.529(2) Angstrom, V = 1604.4(8) Angstrom(3), d(calcd) = 1.54 g cm(-3) , Z = 4. However, 24b gave as the major insertion product the aminofur an 26, and pyrroline-derived carbene complexes 30a,b gave lactams 32a, b and trace amounts of pyrroles 31a,b. Only trace amounts of pyrroles were detected starting from carbene complexes derived from azetidine ( 33a-e) and 36, which gave mainly the lactams 35a,d and 37. Mechanisms for these new transformations of aminocarbene complexes of chromium ba sed on the behavior of the Stevens-type acyl-stabilized N-ylides will be suggested.