A convenient synthesis of thiazolopyrimidines, thiazolodipyrimidines and heterocyclothiazolopyrimidines

<strong>Synthesis and characterization of 2-arylidene derivatives of thiazolopyrimidines with potential biological activity</strong>

“…Although 2-arylidene derivatives of 5 can be synthesized in a one-pot process, directly from 4, [9] we obtained better yields and purity using the isolated compound 5 as the starting material [8] . Briefly, a mixture of 5 (1 mmol), the appropriate aromatic aldehyde (1 mmol) and piperidine (80 μL, 0.8 mmol) was refluxed in ethanol.…”

“…The thiazolo[3,2-a]pyrimidine 5 was then easily obtained by condensation with either ethyl chloroacetate or chloroacetyl chloride [8] . Although 2-arylidene derivatives of 5 could be synthesized in a one-pot process, directly from 4 (Method A) [9] , we obtained better yields and purity using the isolated compound 5 as the starting material for condensation of the corresponding enolate with the appropriate aldehyde in the presence of piperidine (Method B) [8] (Scheme 1). The known compound 6a and its new analogues, 6b and 6c, were thus prepared as racemates in good yields.…”

“…Yield 88%; Rf 0.64 (tlc, silica, 2/1 hexane/ethyl acetate); mp 175-177 o C (lit [8] , 164-166 o C; lit [9] , 164 corrections were applied using SADABS. [20] The structures were solved by direct methods using SHELXT [21] and refined with full-matrix least-squares refinement against F 2 using SHELXL.…”

Heterocyclic synthesis with activated nitriles : An expeditious synthetic approach to polyfunctionally substituted pyrroles, heterocyclopyrimidines and coumarins

“…The reaction mixture was left aside at room temperature for 3 h, whereby the solid product that separated was collected by filtration, dried and crystallized from the appropriate solvent. -1-[1'-cyano-2'-dimethylaminoethenyl)-4-oxo-3-phenyl-1,2,3,4-tetrahydro-2-thioxopyrimidine (9). To a solution of 8 (5 mmol, 1.34 g) in dry dioxane (30 mL), dimethylformamide dimethylacetal (DMF-DMA) (5 mmol, 0.6 g) was added.…”

“…The reaction apparently involves an intramolecular heterocyclization via the addition of the amine nitrogen of 3 to the carbon of isothiocyanate function and a subsequent alkaline hydrolysis of the imino function under the reaction conditions.17 Reaction of 8 with an equimolar amount of N,Ndimethylformamide dimethylacetal (DMF-DMA) in dry dioxane, under reflux, furnished 5- (9) in an acceptable yield. Treatment of 9 with an equimolar amount of hydrazine hydrate in refluxing ethanol furnished exclusively a single product that could be formulated (10).…”