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Peculiar reaction of N2‐acyl derivatives of 2‐aryl‐5‐hydrazino‐1,3‐oxazole‐4‐carbonitriles with the lawesson reagent

“…As shown here, the latter are regioselectively acylated at the N 2 atom of the hydrazino group, if treated under mild conditions with acyl chlorides in the presence of dimethylaniline. Interestingly, the acylation conducted in the presence of triethylamine mostly involves the N 1 atom of the hydrazino group [4]. By comparing the IR and 1 H NMR spectra for isomeric acylated products, we have been able to fully ascertain that compounds 2a-d are free of the primary amino group but contain, instead, the characteristic moiety C(O)NHNHHet (Table 2).…”

“…To a suspension of 1a,b (10 mmol) obtained by the known procedure [4] in THF (25 mL) containing dimethylaniline (5 mL), a solution of acetyl chloride or 4-methylbenzoyl chloride (10 mmol) was added dropwise in THF (5 mL) at 10…”

A challenging synthesis of new 1,3,4‐thiadiazole derivatives starting from 2‐acylamino‐3,3‐dichloroacrylonitriles

“…The cyclocondensation 1→2 was studied before [4,9]. It represents a particular case of a quite general synthetic route to 5-hydrazino-1,3-oxazole derivatives containing various electron acceptor groups, such as CN, C(O)OAlk, P(O)(OAlk) 2 , PPh + 3 , etc., at the position 4 [4,9,12].…”

“…The mixture was allowed to stand at r.t. for 24 h. After filtering off hydrazine hydrochloride, the solvent was evaporated in vacuo, and the residue was treated with H 2 O, filtered off, dried, and purified by recrystallization from EtOH or hexane to give 2a-e (Table 1). Compounds 2a-d were described before [4,9].…”

“…Starting from these reagents, the preparative syntheses were elaborated for a number of functional derivatives c 2004 Wiley Periodicals, Inc. of 1,3-oxazole [1][2][3][4][5][6][7]10,11], 4H-imidazole [8], and 1,3,4-oxadiazole [9]. The present work addresses a new line in harnessing of 2-acylamino-3,3-dichloroacrylonitriles for the preparation of interesting 1,3,4-thiadiazole derivatives.…”