Reversible pyranyl complex formation and the mechanism of rearrangement to (η5-6-oxocycloheptadienyl)Mn(CO)3 complexes in the reaction of β-cyclomanganated 1,5-diarylpenta-1,4-dien-3-ones and alkynes; the crystal structure of [2,4-diphenyl-6-(2-phenylethenyl)pyranyl-η5]tricarbonylmanganese

A comprehensive understanding of carbon–carbon bond formation by alkyne migratory insertion into manganacycles

“…In the case of cyclomanganated chalcone derivates this results in the formation of pyranyl complexes. 46,47 This process is analogous to the catalytic oxidative coupling of alkynes with heterocycles and the related formation of 5aa (Fig. 1b).…”

“…In the case of cyclomanganated chalcone derivates this results in the formation of pyranyl complexes. 46,47 This process is analogous to the catalytic oxidative coupling of alkynes with heterocycles and the related formation of 5aa (Figure 1b). 35 Alternatively, manganated aromatic ketones have been shown to react with alkynes to give 1H-inden-1-ols (Figure 6d).…”

“…48,49 A key step in such a process would be the formation of a five-membered ring and it was envisaged that could occur from 3ia through nucleophilic attack of the Mn-coordinated carbon atom onto the carbonyl group of the ketone. 46,47 Both of these potential pathways were successfully modelled by DFT (Figure 6c). In the case of the first pathway, which would afford a six-membered ring, the transition state for C-O bond formation (TS39ai) was located at +39 kJ mol -1 with respect to the alkyne complex 2ia which was taken as the reference state.…”

“…48,49 A key step in such a process would be the formation of a ve-membered ring and it was envisaged that could occur from 3ia through nucleophilic attack of the Mn-coordinated carbon atom onto the carbonyl group of the ketone. 46,47 Both of these potential pathways were successfully modelled by DFT (Fig. 6c).…”

2-Ferrocenyl-substituted pyrylium ions from coupling of ethynylferrocene with cyclomanganated chalcones

“…Chromatography separated two main products. The first of these was an h 5 -(ferrocenyl)pyranylmanganese tricarbonyl, 3a, corresponding to the major product reported from reactions of other alkynes with cyclomanganated chalcones [7,8]. This was fully characterized by elemental analysis, and by an X-ray crystal structure determination (see below), with further validation provided by 1 H and 13 C NMR spectra.…”