Cyclopentenone formation via hydrogen activation in the reactions of chromium carbene complexes with alkynes

Phytochemical and bioactivity studies on constituents of the leaves of Vitex quinata

“…An unusual double bond carbon signal observed in the downfield region at δ C 174.0 (C-9) of the 13 C NMR spectrum, together with signals at δ C 207.0 (C-12), 139.2 (C-13), 78.0 (C-10), and 40.5 (C-11), suggested the presence of a conjugated cyclopentenone structure, which was supported by comparison with reported NMR data of a similar ring system (Challener, 1993). The carbonyl carbon signal at δ C 174.1 (C-1) and seven methylene signals at δ C 34.0 (C-2), 29.7 (C-6), 29.0 (C-4 and 5), 28.1 (C-7), 27.4 (C-8), and 24.9 (C-3), were assignable to a fatty acid chain moiety.…”

Coupling of Fischer Carbene Complexes with Conjugated Enyne−Aldehydes and Ketones: A Novel Synthesis of Furan Derivatives

“…The only enyne−carbonyl compound that failed to produce a furan derivative was the enyne ester (Table , entry D). Neither starting material was recovered from this reaction; no identifiable compounds could be isolated from this complex reaction mixture . This failure is presumably due to the lower nucleophilicity of the carbonyl oxygen; thus, the crucial cyclization to the carbonyl ylide intermediate does not occur.…”

Group 6 Fischer carbene complexes: “chemical multitalents” for multi-component reactions

“…tion of a chromium alkenyl carbene complex can be also achieved if a silicon group is present in the b-position[26].…”