Bridgehead nitrogen heterocycles which contain the quinazoline moiety – synthesis and cycloaddition of 1,2-dihydroquinazoline 3-oxides

Abstract

A novel synthesis of 1,2-disubstituted 1,2-dihydroquinazoline 3-oxides 8 and the first ever examples of 1,3-dipolar trapping of these nitrones to homonuclear dipolarophiles is described. The new dipoles 8 reacted with N-methyl maleimide, generating diastereomeric adducts 14-16. In the reaction between 8 and dimethyl acetylenedicarboxylate, primary cycloadducts 17 and/or stable rearrangement products, azomethine ylides 18, are formed depending on the substitution pattern of the dipole. The structure of 18c is unambiguously assigned by X-ray crystallographic analysis. An X-ray crystal structure determination is also presented for the cyclopropylisoxazoloquinazoline 22 formed by a [3 + 2] addition of 8a to 21, the dimethyl acetylenedicarboxylate tetramer.

Aerobic C–C Bond Cleavage of Indoles by Visible‐Light Photoredox Catalysis with Ru(bpy)32+

“…( E )‐2‐(Methylamino)benzaldehyde Oxime (3d): Yellow solid (39.2 mg, 87 % yield). 1 H NMR (400 MHz, CDCl 3 ): δ = 8.26 (s, 1.0 H), 7.30–7.26 (m, 1.0 H), 7.13 (dd, J = 7.6, 1.2 Hz, 1.0 H), 7.01 (s, 1.0 H), 6.97 (s, 1.0 H), 6.79–6.66 (m, 2.0 H), 2.94 (d, J = 4.8 Hz, 3.0 H) ppm.…”

“…(E)-2-(Methylamino)benzaldehyde Oxime (3d): [16] 3, 148.2, 132.7, 130.9, 115.2, 114.0, 109.8, 29.7 ppm. [17] Yellow solid (42.8 mg, 90 % yield).…”

Visible-light-mediated reaction: synthesis of quinazolinones from 1,2-dihydroquinazoline 3-oxides

“…As shown in Scheme 4, the synthesis of 16a-g started with N-methylation of quinoline (17) with methyl iodide in toluene to give the 1methylquinolin-1-ium iodide (18). As shown in Scheme 4, the synthesis of 16a-g started with N-methylation of quinoline (17) with methyl iodide in toluene to give the 1methylquinolin-1-ium iodide (18).…”

Transformations of Di‐ and Tetrahydropyrimidine Derivatives into Condensed Heterocycles with Retention of their Partially Saturated Structure

“…F. Heaney and coworkers have described first examples of 1,3‐dipolar cycloadditions of 1,2‐dihydroquinazoline 3‐oxides 121 to homonuclear dipolarophiles (Scheme ). Reaction of 121 with N ‐methylmaleimide in dichloromethane afforded diastereomeric tetracyclic adducts 122 – 124 with varying selectivity.…”