The photochemistry of 1-alkenyl-substituted-1,2,3-benzotriazoles leading to formation of indole and fused indole derivatives

Nader Al-Jalal,Mohamed H Elnagdi,Maher R Ibrahim,Nouria A Al-Awadi

doi:10.3998/ark.5550190.0012.a24

Nader Al-Jalal, Mohamed H Elnagdi + Show 2 more

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https://doi.org/10.3998/ark.5550190.0012.a24

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Abstract

Under photolysis conditions involving irradiation with a 16 W low pressure mercury arc-lamp (254 nm) or sunlight, functionally substituted 1-vinylbenzotriazoles react efficiently to produce 2-acylindoles, 2-benzotriazol-1-yl-4-methylquinolin-3-ol, isatin, indolo[2,1-b]quinazoline-6,12dione (tryptanthrin) and dihydropyrazolo[4,3-b]indole.

Highlights

It is generally known that 3-substituted indoles can be readily generated via reactions of indoles with electrophilic reagents and that 2-substituted indoles are better produced by using Nenitzescu, Madelung and Gassman ring synthesis methodologies.[1]
We described a protocol for the synthesis of 3-acylindoles,[2] in which difficultly obtained C-2 substituted indoles could be prepared
In Scheme 1 are summarized the results of reactions promoted by irradiation of acetonitrile solutions of 1a-c in quartz glass tubes with a 16 W low pressure mercury arc-lamp (254 nm) under a nitrogen atmosphere for 24 h at room temperature

Summary

Introduction

It is generally known that 3-substituted indoles can be readily generated via reactions of indoles with electrophilic reagents and that 2-substituted indoles are better produced by using Nenitzescu, Madelung and Gassman ring synthesis methodologies.[1]. Previous studies have shown that thermolytic and/or photolytic reactions of 1-substituted benzotriazole derivatives take place with elimination of N2 followed by subsequent ring closure of the resulting biradical intermediates to form heterocyclic products (Figure 1).[3,4,5,6,7,8] These efficient processes have been described by Katritzky and his coworkers.[9] In a follow up to our earlier efforts in which syntheses of the benzotriazole derivatives 1a-c, 10 and 15 were developed,10a-d we gained have explored the photochemistry of these substances, postulating that the reactions would afford 2-substituted indoles in good yields. We report the results of this investigations aimed at the synthesis of substances of 2-substituted indoles through photochemical reactions of benzotriazoles 1a-c, 10 and 15

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Results

Conclusion