Transition Metal‐Free α‐C(sp³)H Bond Functionalization of Amines by Oxidative Cross Dehydrogenative Coupling Reaction: Simple and Direct Access to C‐4‐Alkylated 3,4‐Dihydroquinazoline Derivatives

Abstract

A transition metal-free catalytic system has been developed for the cross dehydrogenative coupling of amines with nitroalkanes under mild condition employing potassium iodide/tert-butyl hydrogen peroxide catalytic system. This methodology was further extended for the construction of biologically important N-heterocycles, namely, 3,4-dihydroquinazoline derivatives. This novel strategy provides a simple, efficient, and direct access to 4alkyl-3,4-dihydroquinazoline derivatives.

Selective copper(II) acetate and potassium iodide catalyzed oxidation of aminals to dihydroquinazoline and quinazolinone alkaloids

“…2). In addition, Reddy and co-workers have developed a catalytic system in which 2,3-substituted tetrahydroquinazoline aminals are converted to quinazolinones using tert- butylhydroperoxide (TBHP) and catalytic potassium iodide [36–37]. While these examples deal with the oxidation of bicyclic aminals, we were interested in developing methods to create dihydroquinazoline and quinazolinone alkaloids from ring-fused aminals.…”

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

“…TBHP catalytic system and only then nitroalkanes (Scheme ). The authors proposed the following mechanism of this reaction (Scheme ), which was further confirmed by NMR experiments . The first step involves the oxidation of KI with TBHP to generate molecular iodine and potassium hydroxide.…”

“…As starting material for CDC, reactions with various pronucleophiles were chosen 2,3‐disubstituted 3,4‐dihydroquinazoline derivatives 10 , which were obtained in situ via the condensation of N ‐(2‐aminobenzyl) substituted anilines and aldehydes (Scheme ). Reaction of 10 with nitroalkanes (sp 3 –sp 3 coupling) was carried out under mild transition‐metal‐free conditions in the presence of potassium iodide as a catalyst and tert ‐butyl hydrogen peroxide (TBHP) as an internal oxidant . The desired aza‐Henry type reaction products 11 were obtained in moderate to good yields by adding reagents in a stepwise manner beginning with the KI/aq.…”

“…Both of these species could be transformed to products 11 by nitromethane without the influence of catalyst. The reaction of 10 with dialkylmalonate as pronucleophile was carried under same conditions and leads to dialkyl 2‐(2,3‐diphenyl‐3,4‐dihydroquinazolin‐4‐yl)malonate derivatives 12 in moderate yields .…”

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

“…Kumar et al demonstrated transition metal-free α-C(sp 3 )–H bond functionalization of amines via an oxidative cross-dehydrogenative coupling reaction [ 44 ]. They reported a one-pot synthesis of substituted dihydroquinazolines 35 from a variety of o -aminobenzylamines with appropriate aldehydes and alkylnitrates.…”