5 MEMBERED RING ANALOGS OF NIFEDIPINE .1. 2-NITRO-3-FURANECARBALDEHYDE AND 2-NITRO-3-THIOPHENECARBALDEHYDE IN THE HANTZSCH PYRIDINE SYNTHESIS

The heterocyclic aldehydes 4 in the Hantzsch pyridine synthesis afford ed dependent on the choosen variation, either the 1,4-dihydropyridines (DHP) 5, the 1,2-DHP 6 or the 1,2,3,4-tetrahydropyrimidines (THPM) 7 as main products. 5-7 were dehydrogenated to the corresponding heteroa romatics 8-10 by cerium(IV). The lactames 11 and 12 were isolated by a ppropiate reduction of the nitro group from 8 and 9 by neighbour group participation of an ester function. The synthesis of 12 represents fo r the second time the evidence of an 2-aminofurane compound. 11 and 12 were converted with phosphorous oxychloride to form the annulated chl oronaphthyridines 13 and 14 which were cyclized with sodium azide to y ield the tetrazoles 15 and 16. The half wave potentials E(1/2) of the DHP and THPM 5-7 were determined by anodic oxidation with the rotating platinum electrode using difference pulse voltammetry (DPV). These ar e comparable with those of the 2-nitrophenyl analogues.