# Synthesis and photooxygenation of 3-(p-substituted phenyl)-3a,8a-dihydro-4H-cyclohepta[d]isoxazoles: facial selectivity

## TL;DR

The paper describes the synthesis and photooxygenation of specific cyclohepta[d]isoxazoles and confirms their structures using X-ray and computational methods.

## Contribution

A facially selective synthesis of endoperoxides from isoxazole derivatives is presented with high yields and structural confirmation.

## Key findings

- Endoperoxides were synthesized as facially selective products in high yields (93%–95%).
- X-ray analysis confirmed the configurations of the endoperoxide and its derived diol.
- Computational simulations using Gaussian 09 and DFT calculations supported the experimental results.

## Abstract

Two 3-(p-substituted phenyl)-3a,8a-dihydro-4H-cyclohepta[d]isoxazoles were synthesized by 1,3-dipolar cycloaddition of the corresponding nitrile oxides with cycloheptatriene. Two endoperoxides were synthesized as facially selective and single products in high yields (93%–95%) from the reactions of isoxazole derivatives with singlet oxygen. The exact configurations of the endoperoxide with a methyl group in the phenyl ring and the diol synthesized from it were confirmed by X-ray analysis. To elucidate the mechanism, the formation energy of the endoperoxide was investigated by simulations using the software package Gaussian 09 and density functional theory calculations via the M06-2X/6-311+G(d,p) level method in dichloromethane. The results were consistent with experimental findings showing the formation of isoxazole products.