Unexpected Formation of Highly Functionalized Dihydropyrans via Addition-Cyclization Reactions Between Dimethyl Oxoglutaconate and α,β-Unsaturated Hydrazones.
The condensation between dienophiles and α,β-unsaturated hydrazone azadienes was previously reported to afford piperidines. During an attempt to adapt this reaction to the preparation of piperidine-based conformationally-restricted analogs of glutamate, it was discovered that the electrophile, dimethyl oxoglutaconate (DOG) led to highly substituted dihydropyrans in 20-50% yield. The unexpected pyran product likely results from an initial 1,4-addition of the hydrazone to the oxoglutaconate followed by intramolecular cyclization of the resultant enolate oxygen to the α,β-unsaturated iminium ion. Further manipulations afford substituted tetrahydropyran 6-methamino-2,4-dicarboxylic acids.
Mullins
Jason E
JE
The Department of Chemistry, The University of Montana, Missoula Montana 59812.
Etoga
Jean-Louis G
JL
Gajewski
Mariusz
M
Degraw
Joseph I
JI
Thompson
Charles M
CM