Reversible pyranyl complex formation and the mechanism of rearrangement to (eta(5)-6-oxocycloheptadienyl)Mn(CO)(3) complexes in the reaction of beta-cyclomanganated 1,5-diarylpenta-1,4-dien-3-ones and alkynes; the crystal structure of [2,4-diphenyl-6

摘要

[1-Phenyl-2-[(E)-3-phenylprop-2-en-1-oyl-kappa O]ethenyl-kappa C-1]tetracarbonylmanganese (1a) reacts with PhCCH in CCl4 at room temperature to form [2,4-diphenyl-6-(2-phenylethenyl)pyranyl-eta(5)]tricarbonylmanganese (2a), whose X-ray crystal structure is reported to complement that of its isomer [6-oxo-2,4,7-triphenylcyclohepta-1,4-dienyl-1,2,3,4,5-eta]tricarbonylmanganese (3a), previously obtained from the reaction under reflux; but for la and PhCCPh the pyranyl complex cannot be isolated before rearrangement to the 3a analogue occurs. More forcing reaction conditions for la with Me3SiCCH and for [1-(2-trifluoromethylphenyl)-2-[(E)-3-(2-trifluoromethylphenyl)prop-2-en-1-oyl-kappa O]ethenyl-kappa C-1]tetracarbonylmanganese (1b) with Me3SiCCH and PhCCH give new analogues of 3a where previously only 2a analogues had been isolated.The reaction in CCl4 under reflux of PhCCH and the beta-deuterio analogue of 1a, [1-phenyl-2-[(E)-3-phenylprop-2-en-1-oyl-3d-kappa O]ethenyl-kappa C-1]tetracarbonylmanganese, gave deuteriated 3a with exo-D at the alpha-carbon, C7. This is inconsistent with the Mn-mediated Ph migration mechanism originally proposed to accommodate the endo position of Ph in 3a, and instead it implicates a cyclopropyl carbonyl-addition intermediate or a cyclopropyl acyl-substitution transition state in the key rearrangement step for 2a -> 3a. (c) 2005 Elsevier B.V. All rights reserved.