Iminofuran chemistry: VII. Intramolecular cyclization of 2-N-aryl-substituted derivatives of 2-amino-4-aryl-4-oxobut-2-enoic and 2-amino-5,5-dimethyl4-oxohex-2-enoic acids

Abstract

The cyclization at the treatment of acetic anhydride of 4-aryl-2-arylamino-4-oxobut-2-enoic and 2-arylamino-5,5-dimethyl-4-oxohex-2-enoic acids was investigated furnishing derivatives of 5-aryl-3-aryl-imino-3H-furan-2-ones and 4-arylamino-2-tert-butyl-2,5-dihydro-5-oxofuran-2-yl acetate respectively. 2-N 2 -Methylenesubstituted 4-aryl-2-hydrazino-4-oxobut-2-enoic and 5,5-dimethyl-2-hydrazino-4-oxohex-2-enoic acids cleanly underwent cyclization under the effect of acetic anhydride into 5-aryl-3-hydrazono-3H-furan-2-ones and 5-tertbutyl-3-hydrazono-3H-furan-2-ones.The analysis of published data shows that iminofuranones are available and convenient compounds for preparation of versatile acyclic and heterocyclic structures [2][3][4][5][6]. The application of iminofuranones in synthetic procedures requires an existence of a convenient method for their preparation with the possibility of substituents variation. We formerly developed a method of the synthesis of N-substituted 5-aryl-3-imino-3H-furan-2-ones consisting in the intramolecular cyclization of N-substituted 2-amino-4-aryl-4-oxobut-2-enoic acids [7-9] and providing a possibility of variation in a relatively wide range of substituents both at the imine nitrogen and the position 5 of the furan ring.To test the potential of this method and to increase the versatility of substituted 3-imino-3H-furan-2-ones we formerly synthesized N-substituted 2-amino(hydrazono)-4-aryl-4-oxobut-2-enoic and 2-amino(hydrazono)-5,5-dimethyl-4-oxohex-2-enoic acids and investigated their tautomeric rearrangements [1,10].

Chemistry of iminofurans: IX. Synthesis and cyclization of (2Z)-2-{(2Z)-2-[2-(3-R-adamantan-1-yl)-2-oxoethylidene]hydrazinyl}-4-(het)aryl-4-oxobut-2-enoic acids

“…Unlike structurally related compounds [13,[20][21][22][23][24][25][26], no β-ketohydrazone tautomers of 3a-3f were detected. Structure A displayed in the 1 H NMR spectrum a multiplet at δ 1.62-2.48 ppm from protons in the adamantyl substituent, a singlet at δ 6.24-6.88 ppm from the vinylic proton, a multiplet at δ 7.04-8.03 ppm from aromatic (heteroaromatic) protons, and singlets at δ 7.77-8.06 (CH=N) and 12.46-13.42 ppm (NH).…”

“…Introduction of a pharmacophoric adamantyl fragment [16][17][18][19] into molecules of 3-hydrazinylidenefuran-2(3H)-ones extends the potential of these compounds as biologically active substances. Cyclization of 4-aryl-2-(2-methylidenehydrazinyl)-4oxobut-2-enoic acids by the action of aliphatic carboxylic acid anhydrides [20][21][22] is one of the most convenient methods of synthesis of 5-aryl-3-hydrazinylidenefuran-2(3H)-ones containing various substituents in the hydrazine moiety. The initial acids can be prepared by reaction of (triphenyl-λ 5 -phosphanylidene)hydrazones (phosphazenes) with 4-aryl-2,4-dioxobutanoic acid derivatives [13].…”