Domino Aza-Annulations of Enynyl-/(Alkynyl)aryl-acetonitriles to Access Nitrogen-Enriched Heterocycles

Abstract

Unprecedented domino aza-annulations of (E)-2-en-4-ynyl-acetonitriles (generated from the Morita–Baylis–Hillman acetates of propiolaldehydes for the first time) with sodium azide under metal- and oxidant-free conditions for the assembly of triazolo-pyridines are accomplished. The developed strategy offers broad substrate scope, extending to (2-alkynyl)­aryl and indolyl-acetonitriles to provide the corresponding triazolo-fused isoquinolines and β-carbolines, respectively, in good yields. Additionally, the synthetic utility of the products is demonstrated via denitrogenative coupling of fused triazoles with different nucleophiles.

Base-Promoted (5 + 2) Annulation between 2(Alkynylaryl)acetonitriles and Arylalkynes for the Synthesis of Benzocycloheptene Derivatives

“…9, 148.7, 132.1, 131.4, 128.7, 128.1, 128.1, 125.0, 123.0, 117.5, 114.6, 114.1, 111.0, 95.8, 84.6, 55.9, 55.9, 22.8;IR νmax(KBr): 22931, 2838, 2206, 1629, 1514, 1455, 1411, 1362, 1329, 1179, 1134, 1027 ; HRMS (APCI) m/z: calcd for C18H15NO2, [M] + , 278.1176; found 278.1172. [8] Brown solid (582 mg, 87%), m.p. : 47.2-47.9 ℃; Isolation by column chromatography (petroleum S16 ether/ethyl acetate: 100/1, Rf = 0.2); 1 H NMR (400 MHz, CDCl3) δ ppm 7.54 (dd, J = 7.5, 1.6 Hz, 1H), 1H),7.38 (td,J = 7.5,1.7 Hz,1H),3H),7.03 (dd,J = 5.1,3.7 Hz,1H), 3.94 (s, 2H); 13 C NMR (101 MHz, CDCl3) δ ppm 132.…”