Photochemistry of 1,4-Dihydropyridine Derivatives: Diradical Formation, Delocalization and Trapping as a Route to Novel Tricyclic and Tetracyclic Nitrogen Heterocyclic Ring Systems.

Nader Al-Jalal,Yehia Ibrahim,Osama Sayed,Nouria Al-Awadi,Maher Ibrahim

doi:10.3390/molecules21070866

Nader Al-Jalal, Yehia Ibrahim + Show 3 more

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https://doi.org/10.3390/molecules21070866

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Journal: Molecules (Basel, Switzerland)	Publication Date: Jun 30, 2016
Citations: 6	License type: CC BY 4.0

Affiliation: Kuwait University

Abstract

Irradiation of an acetonitrile solution of 4-aryl-3,5-dibenzoyl-1,4-dihydropyridine derivatives 1a–c and maleimides 2a–c using medium pressure Hg-arc lamp (λ > 290) nm afforded three different cycloadducts 4, 5, 6 in addition to the oxidation products 3. These results indicate that compounds 1a–c undergoes intermolecular cycloaddition reaction through three biradical intermediates and behave photochemically different than those reported previously for the analogous 3,5-diacetyl and 3,5-dicarboxylic acid derivatives. The present work also offers simple access to novel tricyclic and tetracyclic nitrogen heterocyclic ring systems of potential biological and synthetic applications. The structure of the photoproducts was established spectroscopically and by single crystal X-ray crystallography.

Highlights

Most photolytic reactions of 1,4-dihydropyridine (DHP) take place with elimination of molecular hydrogen followed by dimerization or aromatization products [7,8,9]
Ponticelli reported that [10,11,12,13] photocycloaddition of acrylonitrile to 1-benzyl-1,4-dihydropyridine dicarboxylate derivatives afforded two diastereomeric azabicyclo[4.2.0]octane derivatives
We describe the photochemical behavior of 4-aryl-3,5-dibenzoyl-1,4-dihydropyridine

Summary

Introduction

1,4-Dihydropyridines have historically played a very important role in the synthesis and mechanistic organic chemistry. Derivatives of 1,4-dihydropyridine (DHP) are drugs belonging to a class of pharmaceutical agents known as calcium channel blockers. They are inhibitors of calcium ion penetration inside cells and weaken the contractility of the cardiac muscle. These compounds have been shown to be very effective vasodilators and are useful in the treatment of hypertension, ischemic heart disease, and other cardiovascular disorders [1,2,3,4,5,6]. Most photolytic reactions of 1,4-dihydropyridine (DHP) take place with elimination of molecular hydrogen followed by dimerization or aromatization products [7,8,9].

Reported

Results and Discussion

Trapping of the

General

Conclusions