Beilstein J. Org. Chem.2022,18, 1741–1748, doi:10.3762/bjoc.18.183
’-methoxy-γ-pyrone in one step. To construct the quaternary carbon of the 2,5-cyclohexadienone of the target, a strategy based on the Robinson-type annulation of an aldehyde derived from α-crotyl-α’-methoxy-γ-pyrone was applied. The grafting of the simplified target’s side chain was demonstrated through an
oxidative anionic oxy-Cope rearrangement of the tertiary alcohol arising from the 1,2-addition of a 1,3-dimethylallyl reagent to 2,5-cyclohexadienone connected to the α’-methoxy-γ-pyrone motif.
Keywords: α’-methoxy-γ-pyrone; 2,5-cyclohexadienone; oxy-Cope; quaternary carbon; Robinson-type annulation
metabolite tridachiapyrone B is related to tridachiapyrone A (Scheme 1c). As the 1,3-cyclohexadiene motif of the latest is oxidized into 2,5-cyclohexadienone, it is assumed that tridachiapyrone B arises from the ring opening of the epoxide (tridachiapyrone C) of tridachiapyrone A. To our knowledge, the
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Graphical Abstract
Scheme 1:
Routes to crispatene, photodeoxytridachione, aureothin, and tridachiapyrone B.
Beilstein J. Org. Chem.2022,18, 182–189, doi:10.3762/bjoc.18.20
two equivalents of NFSI afforded 4,4-difluoro-3,5-dimethoxy-2,5-cyclohexadienone (2c'') as the major product in 80% yield (Scheme 2a). Mechanistically, formation of 2c'' from 1,3,5-trimethoxybenzene (1c) requires a fluorodemethylation pathway to be operational under the ball-milling conditions, for
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Graphical Abstract
Scheme 1:
Examples of mechanochemical reactions using NFSI.