論文の公開元へTrifluoromethylated Oxidopyridinium Betaines: Unique (5+2) Cycloaddition Selectivity Imposed by 2‐ or 6‐Trifluoromethyl Groups
概要
The (5 + 2) cycloaddition of 3-oxidopyridinium betaines with
activated alkenes as dipolarophiles is a powerful method to
construct a valuable N-heterobicyclic (tropane) framework, in
which an enone moiety can be used in further derivatizations
(Figure 1a).[1] Therefore, oxidopyridinium (5 + 2) cycloaddition has
been successfully applied to the synthesis of tropane alkaloids,
bioactive molecules, and natural-product-like scaffolds.[2,3]
Generally, oxidopyridinium betaines are generated via Nalkylation of pyridin-3-ol and the subsequent deprotonation of the
resultant 3-hydroxypyridinium intermediates. The overall process
is fascinating as a dearomative transformation of pyridin-3-ol.
Although oxidopyridinium (5 + 2) cycloaddition has been
extensively investigated since the pioneering study by the
Katritzky group (Figure 1a),[4] to the best of our knowledge, CF3substituted oxidopyridinium betaines has not been reported. ...
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