Mechanistic Studies on Garratt-Braverman Cyclization: The Diradical-Cycloaddition Puzzle.
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.
Department of Chemistry, Indian Institute of Technology Kharagpur , Kharagpur 721302, India.
Joyee
J
Das
Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati 781039, India.
Subhendu Sekhar
SS
Bag
Department of Chemistry, Indian Institute of Technology Kharagpur , Kharagpur 721302, India.
Amit
A
Basak