New heterocycles of 2,3‐diaryl‐substituted maleic hydrazides

Abstract

2,3‐Diaryl‐substituted maleic anhydrides were prepared by a modified one‐pot synthesis of Perkin condensation using mixed sodium salts of arylglyoxylic acid and arylacetic acid with acetic anhydride in 1,4‐dioxane. The treatment of these anhydrides with ammonium bicarbonate, or methanolic hydrazine, offered the corresponding 2,3‐diaryl‐substituted maleimides and maleic hydrazides (4,5‐diaryl‐substituted 1,2‐dihydropyridazine‐3,6‐dione), respectively. Evidence obtained from NMR, UV, and mass spectra suggest that 2,3‐diaryl‐substituted maleic hydrazides do not exhibit monolactim forms. Ring contraction of the diaryl‐substituted maleic hydrazide by nitrosation led to the formation of the corresponding maleimide. Interconversion between the corresponding maleic hydrazide and maleimide was observed following equilibrium reaction. Our experiment proposes that the chemistry of 2,3‐diaryl‐substituted maleic hydrazides rarely involves the function of ethylene moiety and resembles that of succinic hydrazine. J. Heterocyclic Chem.,(2011).

Direct cycle between co-product and reactant: an approach to improve the atom economy and its application in the synthesis and protection of primary amines

“…12,13 To circumvent the long-standing problems that have limited the widespread application of the Gabriel synthesis, modifications of the original Gabriel synthesis, including the addition of catalysts, hydrazinolysis for the cleavage of the N-alkylphthalimide and new Gabriel reagents, have been reported. [14][15][16][17][18] It is necessary and important to improve the yields of every step within the Gabriel synthesis, including the alkylation of phthalimide and the hydrolysis of the resulting N-alkylphthalimide. In our opinion, however, an efficient recovery of the phthalyl co-products after hydrolysis or hydrazinolysis and reapplying them in the same reaction is the key to an atom-economical Gabriel-type amine synthesis.…”

“…Conventional methods for cleavage of the phthalimide in the Gabriel synthesis include using bases, acids, hydrazines or reductants. 18,[28][29][30] In the preliminary hydrolysis of 3, 50 eq. of concentrated hydrochloric acid (6 M) was used in different solvent systems (Table S2 †).…”

“…To our surprise, 3 was quite stable and remained unreacted, even after microwave irradiation at 100 °C for 30 min. Some literature 18,29,31 reports have indicated that 3,4-diarylmaleic anhydrides can be obtained from the corresponding 3,4-diaryl maleimides under basic conditions followed by acidification. Using a similar approach, 6 eq.…”