4-(4-Chloro-phenyl)-pyrimidinium ylides. 1. Structure, stability, reactivity

Abstract

In this paper we present a theoretical and experimental study concerning the structure, stability, and reactivity of 4-(4-chlorophenyl)pyrimidinium ylides. 4-(4-Chlorophenyl)-pyrimidinium ylides are relatively stable compounds, their stability varying with the nature of the ylide carbanion substituent. The stronger the electron-withdrawing effect of these substituents, the more the anionic charge is delocalized, and therefore the higher their stability. The experimental and quantum chemical calculations confirm this hypothesis and are in accordance with each other. The electronic absorption spectra of 4-(4-chlorophenyl)-pyrimidinium 4-X-benzoyl methylides can be assigned to an intramolecular charge transfer band. The quantum chemical calculations show the possibility to use pyrimidinium ylides as nucleophilic reagents as well as 1,3-dipoles in reaction with appropriate reagents. The influence of microwave irradiation for the synthesis of azinium salts was also studied. The reaction of 4-(4-chlorophenyl)pyrimidine with an organic haloalkane shows a remarkable rate acceleration under microwave irradiation and allows a general and facile synthesis of azinium salts. A comparative study of microwave and classical conditions (use of solvents) has been done.

Molecular Construction Using Formamide as a C1 Feedstock

“…In 1995, Hasan and coworkers [21b] used the same approach to construct new pyrimidine (IIa −6 %) by heating the ketone (Ia), TRIFO and a mixture of formamide and DMF for 20 h at 180 °C. In 2005, Moldoveanu et al [21c] . heated formamide with dimethyl sulfate at 80–90 °C for 2 h. The byproduct methyl formate was removed by vacuum distillation, and 4‐chloroacetophenone and p‐toluenosulfonic acid were added.…”