Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor

Abstract

A convergent strategy is reported for the construction of nitrogen-containing heterocycles from common substrates: 1,4-diketones and primary amines. Indeed, by just varying the substrates, the substituents, or the heating mode, it is possible to selectively synthesize indole, indolone (1,5,6,7-tetrahydroindol-4-one), or cinnoline (5,6,7,8-tetrahydrocinnoline) derivatives in moderate to excellent yields.

Indole frameworks via transition-metal-free annulation: a current perspective

“…The reaction could be carried out under acidic conditions (3 mol% AcOH in toluene). 61 The probable mechanism is presented in Scheme 3. At first, protonation of conjugated carbonyl group of 1,4-diketone 7 generated protonated species A which upon reaction with primary amine 8 resulted in imine B .…”

tert-Butyl Hydroperoxide Promoted the Reaction of Quinazoline-3-oxides with Primary Amines Affording Quinazolin-4(3H)-ones

“…Primary amines are low-cost, readily available, and chemically diverse starting materials. For these reasons, primary amines are commonly used in the preparation of nitrogen-containing heterocycles, such as quinolines, quinoxalines, indoles, and quinazolines . In recent years, several efforts have been directed toward the synthesis of nitrogen-containing heterocycles by treating easily prepared N -oxides with a variety of primary amines.…”