Transformation of 2-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)-6-ethoxy-4-phenylpyridine-3,5-dicarbonitrile into 4-aminopyrido[2,3-d]pyrimidines and 2-(pyrid-2-yl)guanidines

Abstract

The reactions of 2-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)-6-ethoxy-4-phenylpyridine-3,5-dicarbonitrile (14) with a range of primary and secondary amines are investigated. Treatment with n-BuNH2 and BnNH2 gave 1,3-di-n-butyl- and 1,3-dibenzyl-2-(3,5-dicyano-6-ethoxy-4-phenylpyrid-2-yl)guanidines 15a (32%) and 15b (82%), respectively. While treatment with Et2NH, n-Pr2NH or Bn2NH gave the analogous 4-dialkylaminopyrido[2,3-d]pyrimidines 16c-e in high yields. Treatment of the dithiazole 14 with pyrrolidine, piperidine or morpholine gave the analogous 4-dialkylaminopyrido[2,3-d]pyrimidines 16f-h, the 2-aminopyridine 13 and 2-(diamino-1-ylmethyleneamino)-6-ethoxy-4-phenylpyridine-3,5-dicarbonitriles 15f-h. The 4-dialkylaminopyrido[2,3-d]pyrimidines 16f-h are converted to the 2-(dialkylamino-1-ylmethyleneamino)-6-ethoxy-4-phenylpyridine-3,5-dicarbonitriles 15f-h upon further reaction with excess dialkylamines. The structure and origins of the two side products 17 and 18 are also discussed. Tentative mechanisms for these transformations are proposed. © 2015 Elsevier Ltd. All rights reserved.