A simple aza wittig‐mediated pyrimidine annulation reaction

Abstract

Treatment of heterocyclic o‐aminonitriles and o‐aminoesters 1a‐5a with dibromotriphenylphosphorane gives iminophosphoranes 1b‐5b which undergo a facile aza‐Wittig reaction at room temperature with phenyl isocyanate to provide the carbodiimides 1c‐5c. Treatment of the latter intermediates with ammonia leads to intramolecular ring closure of the initially formed guanidines to provide the fused 4‐aminopyrimidines and 4(3H)‐pyrimidinones 1d‐Sd.

A facile synthesis and herbicidal activities of novel fluorine-containing thiazolo[4,5-d]pyrimidin-7(6H)-ones

“…For example, the 1 H NMR spectra of 5p showed the signal of NH at d 4.95 as triplet, which was not the same as the proton of PhNH, of which the chemical shift is greater than d 7.0 [15]. And the methylene protons displayed a doublet also, which strongly suggested the existence of an NHCH 2 -group.…”

A facile synthesis and fungicidal activities of novel fluorine-containing pyrido[4,3-d]pyrimidin-4(3H)-ones

“…All products of type 5 were obtained as white solid after recrystallization from CH 2 Cl 2 /petroleum ether, and were characterized by IR, 1 H NMR and elemental analysis, and some of them were confirmed by EI-MS. For example, the 1 H NMR spectrum of 5 m showed the signal of NH at d 4.37 as singlet, which was not the same as the proton of PhNH, of which the chemical shift is greater than d 7.0 [17]. In IR spectrum, the relatively strong absorption of C O appeared at 1674-1704 cm À1 .…”

A new regioselective synthesis and bioactivity of 1H‐pyrazolo[3,4‐d]pyrimidin‐4(5H)‐one derivatives

“…Its chemical shift is 4.02 ~ 4.75, i.e. more shielded than the one in PhNH (δ>7.0) [17]. For example, the 1 H NMR spectral data of 5 c shows the signals of NH at 4.32 as triplet and NCH 2 at 3.35 ~ 3.42 as multiplet, which strongly suggests the existence of NHCH 2 P r-n group in 5c.…”