3‐Substituted acylindoles 8 are obtained via refluxing carboxylic acids with indole in acetic anhydride solutions. The formed 3‐substituted acylindole 8a is readily converted into 4‐aminopyrazol‐3‐ylindoles 20, and into 22. Indole reacts with chloroacetyl chloride to yield: 3‐chloroacetylindole 9 which could also be utilized for synthesis of a number of 3‐substituted indoles.
3‐Amino‐3‐phenyl‐2‐phenylazoacrylonitrile 6 is obtained in good yield via reaction of 5 with phenyl magnesium bromide. The compound 6 is readily converted into 4a. The so formed alkanenitrile reacted with phenylmagnesium bromide to yield 8. Compound 8 could be also obtained from reaction of 9 with phenylmagnesium bromide. The arylhydrazononitriles 8 and 4a reacted with chloroacetonitrile to yield the 4‐aminopyrazoles 12a,b. Compound 12a reacted with acetic anhydride to yield the 15a and with benzoyl chloride to yield the pyrazole 16 which was converted into 15b. Refluxing 10 in acetic acid gave a mixture of the azadiene 21 and the cinnoline 22 is obtained. The azadiene 21 is converted into 22 either thermally or photochemically.
Substituted 3-Acylindoles. -Carboxylic acids in the presence of acetic anhydride acylate indole regioselectively at the C-3 position. Moreover, chloroacetyl chloride reacts directly. The 3-functionalized products are excellent precursors for the synthesis of biologically interesting azolyl indoles [cf. (VII)] that are otherwise difficult to access. -(ABDEL-MOTALEB, R. M.; MAKHLOOF, A.-M. A.-S.; IBRAHIM, H. M.; ELNAGDI*, M. H.; J. Heterocycl. Chem. 44 (2007) 1, 109-114; Dep. Chem., Fac. Chem., Cairo Univ., Giza, Egypt; Eng.) -R. Staver 23-108
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