The Hantzsch thiazole synthesis under acidic conditions: change of regioselectivity

Novel thiophenes and analogues with anthelmintic activity against Haemonchus contortus

“…The in vitro anthelmintic activity of analogues with hydrogen (19) and bromine (20) at the 3-position of the thiophene ring was comparable to the biological activity of the initial lead 1. However, the 3-nitro-thiophene 21 17 was inactive at 100 ppm after 24 h of incubation.…”

“…Thiophenes 1,19,20,6,9,16, and 18 and thiazoles 50 and 52 did not cause a significant reduction of the number of nematodes (H. contortus or T. colubriformis) at 100 mg/kg, whereas levamisole (2) is completely efficacious at 10 mg/kg. Compounds 20, 6, 50, and 52 caused high levels of gerbil mortality at 100 mg/kg.…”

Synthesis of deuterium-, tritium-, and carbon-14-labeled BILN2061, a potent hepatitis C virus protease inhibitor

“…Hexane was then added to give a fluffy white precipitate, which was filtered, washed with hexane, and dried under reduced pressure to give 1.02 g of product in 72% yield. 13 (5) (252.5 mg, 0.33 mmol) in isopropyl alcohol (4 ml) was stirred at 708C in a preheated oil bath for 3 h. After cooling to room temperature, the solution was concentrated in vacuo. The residue was dissolved in chloroform and washed with a saturated aqueous NaHCO 3 (2 Â 60 ml), brine (100 ml), dried over MgSO 4 , filtered and concentrated under reduced pressure.…”

“…The regioselectivity can be altered to give both the 2-substituted and the 3-substituted-2-imino-2,3-dihydrothiazoles under acidic conditions. 13 As shown in Scheme 1, the preparation of ]nonadec-7-ene-4-carboxylic acid methyl ester) at 708C in isopropanol to give the substituted thiazole in 98% yield. This material was then hydrolyzed with a solution of LiOH in THF/methanol at room temperature to give [ 2 H 7 ]-BILN2061 in 91% yield (Scheme 2).…”

Solid-phase synthesis of tetrasubstituted 2-imino-1,3-thiazolines using a functionalizing cleavage strategy

“…11 This method leads to a mixture of regioisomers depending upon the reaction conditions. 12 To overcome this problem, unsubstituted thiourea could be used followed by regioselective alkylation of the nitrogen atom. 13 A different approach is the reaction of a-haloimines with potassium thiocyanate.…”