Intramolecular cyclization manifolds of 4-Alkylpyridines bearing ambiphilic side chains: Construction of spirodihydropyridines or benzylic cyclization via anhydrobase intermediates
4-Alkylpyridines possessing nucleophilic β- dicarbonyl side chains have been converted to spirodihydropyridines upon treatment with ethyl chloroformate and sub-stoichiometric amounts of Ti(OiPr)4. Alternatively, inclusion of mild base in the reaction medium was found to facilitate generation of anhydrobase intermediates. Subsequent aldol-like condensations with electrophilic side chain moieties followed by hydrolysis delivered benzylically cyclized pyridines in good yield. In situ hydrogenation of cyclized anhydrobase intermediates afforded 4-substituted piperidines.
Parameswarappa, Sharavathi G.,Pigge, F. Christopher
p. 8038 - 8048
(2013/01/15)
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