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Organic Synthesis via Transition Metal Complexes. 50. - 2H-Pyrrole Complexes by Stepwise Insertion of Alkynes and Isocyanides into M=C Bonds of Carbene Chromium or tungsten Complexes
Aumann, Rudolf,Hinterding, Peter
, p. 213 - 218 (2007/10/02)
2H-Pyrrole complexes 6a, b are obtained in two steps by cycloaddition reactions of the carbene complex (CO)5W=C(OEt)C6H5 (1d), the alkyne EtO-CCH (2) and isocyanides R1-NC 4a, b (R1=CH3, c-C6H11).LnM=C(OEt)R 1 nM=Cr(CO)5, W(CO)5; R=C6H5, CH3) reacts with 2 to give 1-metalla-1,3-dienes 3a-d. (E)/(Z)-3d and 4 yields 6a, b via 1-aza-1,2,4-pentatriene complexes 5, which are open-chain precursors of 6. 2H-Pyrrole complexes 11 and 14 are synthesized in overall cycloadditions with reversed connectivity, or formation of 1-chroma-1,3-dienes 10 and 13 by condensation of the methylcarbene complex 1a with acid amides, and cyclisation again with isocyanides 4.Key Words: Carbene complexes of chromium and tungsten / 1-Metall-1,3-dienes / Insertion of alkynes and isocyanides into M=C bonds / 2H-Pyrrole complexes of chromium and tungsten / Cycloaddition reactions of carbene complexes, alkynes and isocanides
