1,1'-Carbonyldiimidazole → 1-{5-[5-(2-Ethoxyphenyl)-1,3,4-oxadiazol-2-yl]-2-thienyl}-2,2,2-trifluoroethanone

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Reaction Steps

To a solution of the carboxylic acid (A1) in DCM was added to PS-CDI (1.7 eq., loading 1.30 mmol/g), and the suspension stirred at RT for 30 min. 2-Ethoxybenzohydrazide (1.3 eq.) dissolved in DCM/DMF was added, and the resulting suspension was stirred at RT overnight. The suspension was filtered and the filtrate evaporated. The crude N′-(2-ethoxybenzoyl)-5-(trifluoroacetyl)thiophene-2-carbohydrazide (MS (ES) C16H13F3N2O4S requires: 386, found: 427 (M+H20+Na)+ and 385 (M−H+e)−) was used as such, without any purification. It was dissolved in excess thionyl chloride and the solution was heated in a microwave oven (sealed tube, 100° C., 5 min) and the thionyl chloride was evaporated. The desired product was isolated by preparative RP-HPLC, using H2O (0.1% TFA) and MeCN (0.1% TFA) as eluents (column: C18). The pooled product fractions were evaporated to afford the title compound. 1H NMR (300 MHz, CD3CN): 8.1-8.08 (1H, m), 8.06-8.01 (1H, m), 7.95-7.90 (1H, m), 7.63-7.56 (1H, m), 7.23-7.17 (1H, m), 7.16-7.09 (1H, m), 4.23 (2H, q, J=7 Hz), 1.48 (3H, t, J=7 Hz). 19F NMR (282 MHz, CD3CN); δ −74.25 (keto form), −86.14 (hydrate form). MS (ES) C16H11F3N2O3S requires: 368, found: 369 (M+H)+ and 387 (M+H2O+H)+.

Provenance & Evidence