By means of electrochemical strategy, very recently, the research group of Professor Shu-Jiang Tu and Bo Jiang from Jiangsu Normal University reported an impressive sulfonylation/halogenation
via the radical cyclization with bifunctionalization of the 1, 6-enynes with high stereoselectivity, avoiding the use of oxidants and metal catalyst (
Scheme 1) [
5]. The authors firstly conceived that the sulfonyl radicals, from sulfonyl hydrazide in the presence of sodium halide with electric current, add into terminal C=C double bond of 1, 6-enynes and subsequent
5-exo-dig cyclization forms the exocyclic vinyl radical intermediates, which would be trapped by halogen atom. Next, they made great effort to establish the following optimal conditions, namely the reaction of 1, 6-enynes
1 (0.2 mmol) with arylsulfonyl hydrazides
2 (0.6 mmol, 3.0 equiv.) in the presence of NaI (0.4 mmol) in the co-solvent of THF-H
2O (4 mL, v/v=1/1) in an undivided cell using two platinum plates as the working electrode and cathode under 10 mA constant current for 4.0 h, and used to produce a wide range of 1-indanones
3 with good stereoselectvity (
Scheme 1a).