Synthesis and characterization of unsaturated diacyl and alkyl-acyl piperazine derivatives

Authors: SAİT SARI, SEDA ÜNALAN, MEHMET YILMAZ

Abstract: The aim of this study is to obtain new unsaturated piperazine compounds by the reactions of piperazine (1a) and piperazine derivatives (1b-1d) with acylation reactive groups (a-2j). Methacryloyl piperazine (1b) was synthesized from the reaction of methacrylic anhydride with piperazine (1a). Acyl chlorides (2b-2d) were prepared from the reaction of thionyl chloride with carboxylic acids (3a-3c) obtained as a result of the reaction with malonic acid and suitable aldehyde (5-methylfuran-2-carbaldehyde for 3a, cinnamaldehyde for 3b, and thiophene-2-carbaldehyde for 3c), respectively, by literature methods. Acyl chlorides 2ed and 2f }were obtained from the reaction of commercially purchased carboxylic acids 3d and 3e with thionyl chloride. Acyl chlorides (2g-2j) were synthesized from the reaction of thionyl chloride with carboxylic acids (3d-3g) transformed from hydrolyzation of esters (4a-4d}) obtained as a result of the reaction of triethyl phosphonoacetate with a suitable ketone (acetophenone for 4a, benzophenone for 4b, 1-(5-methylfuran-2-yl)ethan-1-one for 4c, and 1-(thiophen-2-yl)ethan-1-one for 4d), respectively, by literature methods. Unsaturated piperazine derivatives 5a and 5b were obtained from the reaction of 1bwith 2b and 2e, respectively. In addition, from the reaction of 1b and acyl chlorides (2b-2j), unsaturated piperazines (5c-5k) were synthesized in medium to good yields (63%-84%). Also, 5l-5g-and 5r-5w were obtained from the reaction of allyl piperazine (2c) and cinnamyl piperazine (2d) with acyl chlorides (2a-2f).

Keywords: Piperazine, acylation, heterocycle

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