Tully, W., Main, L. & Nicholson, B.K. (2001). β-Cyclomanganated 1,5-diphenylpenta-1,4-dien-3-ones and their reactions with alkynes: routes to η5-pyranyl--- and η5-oxocycloheptadienyl---Mn(CO)3 complexes. Journal of Organometallic Chemistry, 633(1-2), 162-172
Permanent Research Commons link: http://hdl.handle.net/10289/142
1,5-Diphenylpenta-1,4-dien-3-ones (4) are cyclometalated with benzylpentacarbonylmanganese to form [[1-phenyl-2-((E)-3-phenylprop-2-en-1-oyl-κO)]ethenyl-κC1]tetracarbonylmanganese derivatives (5). Coupling of 5 with alkynes in some cases gives [4-phenyl-2-(2-phenylethenyl)pyranyl-η5]tricarbonylmanganese complexes (6) analogous to those previously reported for β-manganated chalcones, but in other cases an alternative cyclisation pathway subsequent to insertion of alkyne into the C---Mn bond leads to [6-oxo-4,7-diphenylcyclohepta-1,4-dienyl-1,2,3,4,5-η]tricarbonylmanganese complexes (7). The X-ray crystal structure determination is reported for one such compound, [6-oxo-2,4,7-triphenylcyclohepta-1,4-dienyl-1,2,3,4,5-η]tricarbonylmanganese (7a), derived from 1,5-diphenylpenta-1,4-dien-3-one and phenylacetylene. The 7-phenyl group is found to occupy the endo position, and a mechanism involving Mn-mediated aryl migration is suggested to explain this stereochemistry. The reaction of 7a with ammonium cerium(IV) nitrate gives a low yield of 2-nitro-3,5,7-triphenylcyclohepta-2,4,6-trien-1-one (9), whose structure was established by X-ray crystal structure analysis. The pyranyl complexes (6) provide the corresponding pyrylium triiodide salts (8) when demetalated with iodine.
This article is published in the Journal of Organometallic Chemistry, (c) 2001 Elsevier Science B.V.