135456-05-2Relevant academic research and scientific papers
Organic Syntheses via Transition Metal Complexes, 56. - Homopyrroles and Dihydropyridines from N-Vinylaminocarbene Iron Complexes and Alkynes by Cyclisation of Intermediate 5-Aza-1-metalla-1,3,6-trienes
Aumann, Rudolf,Trentmann, Beate,Krueger, Carl,Lutz, Frank
, p. 2595 - 2602 (2007/10/02)
2,3-homopyrroles 5 and dihydropyridines 7, 8 are obtained by the light-induced addition of alkynes 4a-d (RCCR1; R, R1 = H, CH3, C6H5, CO2H3) to the N-vinylaminocarbene iron complex (= 3-aza-1-ferra-1,4-diene) 3.The formation of the N-heterocycles 5 and 7 as well as that of the pyrrolium carbonylferrates 6 can be explained by assuming the chelated 5-aza-1-ferra-1,3,6-trienes A to be key intermediates in this reaction.Stereochemical considerations lead to the conclusion that the ring expansion of the 4 1/2-membered ring of 3 to the 6 1/2-membered ring of A occurs without prior ? decomplexation by the insertion of a CC unit into the M=C bond.NMR measurements and MNDO calculations suggest that the bicyclic homopyrroles 5 are in equilibrium with the novel monocyclic homopyrrole species 9.The structure of 6c has been established by X-ray diffraction analysis. Key Words: Homopyrroles, mono- and bicyclic / Cycloadditions of N-vinylaminocarbene iron complexes to alkynes / 5-Aza-1-ferra-1,3,6-trienes / Intramolecular cyclopropanation, metal-induced / 2H-Pyrrolium tricarbonyl iron complexes / Pyridine, 1,2-dihydro-, tricarbonyl iron complexes
