DDQ dehydrogenative Diels–Alder reaction for the synthesis of functionalized spiro[carbazole-1,3′-indolines] and spiro[carbazole-1,5′-pyrimidines]?

New Journal of Chemistry Pub Date: 2021-07-19 DOI: 10.1039/D1NJ02836G

Abstract

DDQ promoted the reaction of 3-(indol-3-yl)-1,3-diphenylpropan-1-ones with 3-methyleneoxindoles in refluxing ethanol resulting in functionalized dihydrospiro[carbazole-1,3′-indolines] in good yields and with high diastereoselectivity. Similar reactions with 5-arylidene-1,3-dimethylbarbituric acids also afforded functionalized spiro[carbazole-1,5′-pyrimidines] in satisfactory yields. The reaction actually proceeded via the DDQ oxidative dehydrogenation of 3-(indol-3-yl)-1,3-diphenylpropan-1-ones to the corresponding 3-vinylindoles, their sequential Diels–Alder reaction with dienophiles and further isomerization process. DFT calculations showed that the Diels–Alder reaction has a normal electron-demanding character.

Graphical abstract: DDQ dehydrogenative Diels–Alder reaction for the synthesis of functionalized spiro[carbazole-1,3′-indolines] and spiro[carbazole-1,5′-pyrimidines]
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