Synthesis of fused N-heterocycles utilizing the heterocyclic enamine protocol

Abstract

Heterocyclic enamines 1 underwent regioselective C-benzylation and C-benzoylation with obromobenzyl bromide and o-halobenzoyl chloride to yield the corresponding C-benzylated and C-benzoylated heterocyclic enamines 2 and 8, respectively. Subsequent intramolecular substitution reactions of 2 and of 8 led to, respectively, the fused 1,4-dihydroquinolines 3 and quinolin-4-ones 9. The ring size effect of the heterocyclic enamines on the reactivity of both the enaminic carbon and the secondary amine was observed.

A Novel Route to Imidoylbenzotriazoles and Their Application for the Synthesis of Enaminones

“…The enaminone class of compounds represents versatile and useful building blocks for the synthesis of heterocyclic compounds, such as 1,5-benzodiazepine, 1,4-dihydropyridine, furoisoquinoline, indole, isoxazole, pyrrolo-1,2,4-triazine, pyrimidine, pyridinone, and quinoline, 19b, derivatives.…”

“…The available methods for the preparation of enaminones can be classified according to the bond formed (Scheme ). Five approaches form bond a : (i) reactions of 1,3-diketones with amines in the presence of catalysts; , (ii) addition of amines to acylacetylenes; ,20a, (iii) palladium-assisted amination of α-keto olefines , or amination with O -methylhydroxylamines in the presence of base; (iv) additions of amines to 3-oxo-2,3-dihydrothiophene 1,1-dioxides with extrusion of sulfur dioxide; and (v) substitution of a β-functional group, such as alkylthio, imidazolyl, and methoxy . Oxidative cleavage of pyridinium perchlorates with hydrogen peroxide (route xi) provides enaminones via bond d .…”