Direct CH/CH functionalization of 1,3-dihydroxy-9H-xanthen-9-one and 1,3-dimethoxy-9H-xanthen-9-one with 1,2,4-triazines and quinazoline

O. N. Chupakhin,I. A. Khalymbadzha,A. D. Sharapov,R. F. Fatykhov

doi:10.15826/chimtech.2020.7.4.17

Abstract

An electron-deficient series of 1,2,4-triazines and quinazoline have been used for cross-dehydrogenative coupling with 1,3-dihydroxy and 1,3-dimethoxyxanthones to give stable nucleophilic addition products. The adducts and their subsequent oxidation products were obtained in good yields and the structures of the compounds were confirmed by 1H NMR spectroscopy. These results expand the scope of the methodology of nucleophilic substitution of hydrogen with the participation of xanthones with azines. Moreover, this methodology makes it possible to obtain new organic materials based on xanthones, which have a wide spectrum of biological activity.

Highlights

Reactions of nucleophilic substitution of hydrogen (SNH) in a series of π-deficient heterocycles are one of the types of crossdehydrogenation coupling (CDC) and proceed as the addition of a nucleophile to an electrophile with the formation of the so-called σH-adduct, which can subsequently be oxidized to a product with a completely aromatic structure (Scheme 1)
We found that when 1,3‐dihydroxyxanthone 1 interacts with 1,2,4‐triazines a or b and quinazoline c in trifluoroacetic acid a mixture of two σH-adducts 2 and 3 is formed
Using calculations in the “Gaussian Interface program”, in the case of 1,3‐dihydroxanthone, carbon C2 has a more negative charge than carbon atom C4. It can be assumed in connection with the data obtained that in the case of xanthone 1 there is a competition between orbital and charge control, which leads to the formation of a mixture of products

Summary

Introduction

It is present in significant quantities in higher plants and in particular in fruits, stems, leaves, bark and kernels of mangoes. It is a promising antioxidant with many health-related properties such as antiviral, antineoplastic, antidiabetic, antioxidant, immunomodulatory, hepatoprotective, and analgesic (Fig. 1) [1]. The transformation of xanthones with azaheterocyclic compounds may be promising for obtaining new biological properties, and for developing the methodology of nucleophilic substitution of hydrogen in chemistry of natural compounds. Reactions of nucleophilic substitution of hydrogen (SNH) in a series of π-deficient heterocycles are one of the types of crossdehydrogenation coupling (CDC) and proceed as the addition of a nucleophile to an electrophile with the formation of the so-called σH-adduct, which can subsequently be oxidized to a product with a completely aromatic structure (Scheme 1)

H Nu Catalyst

Results and discussion

Conclusions