Mechanistic Studies on Garratt–Braverman Cyclization: The Diradical–Cycloaddition Puzzle
作者:Joyee Das、Subhendu Sekhar Bag、Amit Basak
DOI:10.1021/acs.joc.6b00490
日期:2016.6.3
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
A green protocol (compared to the existing methodology) for carrying out Garratt-Braverman cyclization has been developed. The method involves stirring a pre-absorbed bispropargyl sulfone/ether/sulfonamide over basic alumina. The reaction with sulfones was over within 10-15 mm at room temperature whereas for the ether/sulfonamide the reaction took 6-8 h at 130 degrees C. The products, aryl naphthalene derivatives, are obtained by simple filtration through Celite, in excellent yields. (C) 2014 Elsevier Ltd. All rights reserved.