SYNTHESIS AND NUCLEAR MAGNETIC-RESONANCE SPECTRA OF N-CARBOETHOXY-4-SPIRO-1,4-DIHYDROPYRIDINES

A series of N-carboethoxy-J-spiro-1, 4-dihydropyridines (11) has been prepared via condensation reactions of glutaraldehydes with ammonia or ethyl carbamate. While ammonia gives substantial amounts of 2-amino-1, 2, 3, 4-tetrahydropyridines as well as some 1, 4-dihydropyridines, ethyl carbamate condenses in benzene solution in the presence of catalytic amounts of p-toluenesulfonic acid to give 11 exclusively. The latter reaction, run as a one-pot synthesis from diol to N-carboethoxy-1, 4-dihydropyridine, gives yields of 70-80%. NMR data, both 1H and 13C, show that in the ground state the rings in these spirourethanes do not interact. NMR investigation of glutaraldehyde isolated from water solution shows it to consist in Me2SO of a 1: 1 mixture of free dialdehyde and polymeric cyclic acetal. In contrast, periodate cleavage of 3, 3-tetramethine-1, 2-cyclopentanediol gives the monomeric cyclic acetal. © 1979, American Chemical Society. All rights reserved.