Synthesis of pyrimidinethiones and spiropyrans proceeding from Mannich ketones

Abstract

New synthetic opportunities of conjugated and saturated β-aminoketones were revealed consisting in heterocyclization reactions with the formation of spirochromenes and hydropyrimidinethiones. Alicyclic conjugated Mannich bases under conditions of basic catalysis suffer deamination followed by [4+2]-cycloaddition leading to the stereo- and regiodirected formation of difficultly available spirochromene derivatives. Three-component condensation of acyclic and alicyclic Mannich ketones with thiourea and aromatic aldehydes under aprotic acid catalysis afforded functionalized derivatives of pyrimidine-2-thione series. Optimum conditions were found for О,N-heterocyclization of β-aminocarbonyl substrates.