Mechanistic Studies on Garratt–Braverman Cyclization: The Diradical–Cycloaddition Puzzle

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• 作者：Joyee Das ; Subhendu Sekhar Bag ; Amit Basak
• 刊名：Journal of Organic Chemistry
• 出版年：2016
• 出版时间：June 3, 2016
• 年：2016
• 卷：81
• 期：11
• 页码：4623-4632
• 全文大小：606K
• 年卷期：0
• ISSN：1520-6904

文摘

In this work, we present the results of extensive multiprong studies involving the fate of deuterium-labeled substrates, EPR, trapping experiments, and LA-LDI mass spectrometry to sort out the controversies relating to the mechanism of Garratt–Braverman cyclization in two systems, namely bis-propargyl sulfones and ethers. The results are in conformity with a diradical mechamism for the sulfone, while for the ether, the anionic [4 + 2] appears to be the preferred pathway. This shows that the mechanistic pathway toward GB cyclization is dependent upon the nature of heteroatom (O or S in sulfone) bridging the propargyl arms.