Preparation of Fully Substituted 1,3,4-Oxadiazole Derivatives from N-Isocyaniminotriphenylphosphorane, (E)-Cinnamic Acids, Chloroacetone and Primary Amines

Abstract

The 1:1 imine intermediate generated by the addition of primary amine to chloroacetone is trapped by Nisocyaniminotriphenylphosphorane in the presence of (E)-cinnamic acids and the corresponding iminophosphorane intermediate was formed. Disubstituted 1,3,4-oxadiazole derivatives are formed via intramolecular aza-Wittig reaction of the iminophosphorane intermediate. The reactions were completed in neutral conditions at room temperature. The disubstituted 1,3,4-oxadiazole derivatives were produced in excellent yields.

Very Efficient and Rapid Catalyst-free One-pot Three Component Synthesis of 2,5-Dihydro-5-imino-2-methylfuran-3,4-dicarboxylate Derivatives Under Ultrasound Irradiation

“…On the basis of the well-established chemistry of isocyanides, [19][20][21][22][23][24]26 it is reasonable to assume that the 2,5-dihydro-5-imino-2-methylfuran-3,4-dicarboxylate derivatives 4 may result from initial addition of the isocyanide to the acetylenic ester and subsequent addition to the electron-poor carbonyl group of acetic anhydride 3 leading to a dipolar specie 6. Cyclization of 6 leads then to the 2,5-dihydro-5-imino-2-methylfuran-3,4-dicarboxylate 4 (Scheme 2).…”

Four-Component Preparation of Disubstituted 1,3,4-Oxadiazoles from (N-isocyanimino)triphenylphosphorane, Phenylacetylenecarboxylic Acid, Biacetyl and Primary Amines

“…16,17 In recent years, we have confirmed a one-pot method for the preparation of organophosphorus compounds. [18][19][20][21][22][23][24] As part of our ongoing program to develop efficient and robust methods for the preparation of heterocyclic compounds, [25][26][27][28][29][30][31][32][33][34][35][36][37][38] we wish to report the preparation of a new class disubstituted 1,3,4-oxadiazole derivatives 5a-j by a novel four-component condensation reaction of biacetyl (1), primary amine 2, (Nisocyanimino)triphenylphosphorane (4) and phenylacetylenecarboxylic acid (3) in excellent yields under neutral conditions (Scheme 1).…”

“…This intermediate may be attacked by conjugate base of the carboxylic acid to form 1:1:1 adduct 9. The intermediate 9 may undergo intramolecular aza-Wittig reaction [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] of iminophosphorane moiety with the ester carbonyl to afford the isolated sterically congested 1,3,4-oxadiazole derivatives 5 by removal of triphenylphosphine oxide (6) from intermediate 10.…”

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“…anti HIV 10,11 and anticonvulsant 12 , etc. Various methods have been reported in literature for synthesis of 1, 3, 4-oxadiazoles 13,14 . The most of the methods involve cyclization of acid hydrazides by using variety of reagents such as phosphorus oxychloride, carbon disulphide, thionyl chloride, tetrahydrofuran, etc.…”