Ionic liquid phase organic synthesis (IoLiPOS) methodology applied to the preparation of new 3,4-dihydropyrimidine-2(1H)-ones bearing bioisostere group in N-3 position

The ionic liquid phase organic synthesis (IoLiPOS) methodology has been used for the preparation of new 3,4-dihydropyrimidine-2(1H)-ones (DHPMs) bearing bioisostere group in N-3 position. For the 3,4-DHPMs substituted with various thiazole rings, the strategy involved a three-component Biginelli condensation in the second step with good yields (93-96%) from ILP bound acetoacetate, aromatic aldehyde (93-97% yield), and N-methyl urea followed by N-3 alkylation with chloroacetonitrile on the ILP bound 3,4-DHPM. Quantitative thionation of the nitrile group grafted on the ILP bound 3,4-DHPM was realized in MeOH with a 40-48% solution of ammonium sulfide and subsequent addition of α-bromoketone produced the thiazole ring appended on the 3,4-DHPM core. After cleavage by transesterification, the target compounds were obtained in good overall yields (47-50%). The efficiency of the IoLiPOS methodology was also demonstrated by the preparation of new 3,4-DHPMs with a tetrazole ring in N-3 position in 5 steps (53-61% overall yield) via the ILP bound 3-cyanomethyl 3,4-DHPM as key intermediate.