Journal
TETRAHEDRON
Volume 69, Issue 26, Pages 5348-5354Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tet.2013.04.123
Keywords
Thiol-vinylsulfone Michael addition; Amine; Organophosphine; Base-catalyzed mechanism; Nucleophile-initiated mechanism
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Funding
- NSFC [21172149, 21202102]
- Shaoxing University [20115010]
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The mechanisms of nitrogen- and phosphorus-centered nucleophile promoted thiol vinylsulfone Michael addition reactions have been studied by theoretical calculations. It is found that the trimethylamine-promoted thiol-vinylsulfone Michael addition proceeds by the base-catalyzed mechanism, in which the attack of the methanethiolate-trimethylammonium ion pair at divinylsulfone is the rate-limiting step. Comparison of different types of nitrogen-centered nucleophiles suggests that the aliphatic amine-promoted reactions undergo the base-catalyzed mechanism whereas the aza-aromatic compound-promoted reactions undergo the nucleophile-initiated mechanism. The trimethylphosphine-promoted thiol-vinylsulfone Michael addition is found to proceed via the nucleophile-initiated mechanism, in which the attack of trimethylphosphine at divinylsulfone is the rate-limiting step. An amine is superior to an organophosphine for the base-catalyzed mechanism because of its stronger basicity. On the other hand, an organophosphine tends to undergo the nucleophile-initiated mechanism more easily than an amine because phosphorus can stabilize the charged intermediates. (C) 2013 Elsevier Ltd. All rights reserved.
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