Chlorosulfonyl isocyanate (CSI) reacts with hydrocarbon alkenes via a stepwise pathway to give chlorosulfonyl beta-lactams which are readily reduced to beta-lactams.  We found that a vinyl fluorine on the alkene inductively raises the energy of the stepwise transition state for the reaction with CSI so that a concerted process is favored.  Rate constants were measured for reactions of monofluoroalkenes with CSI.  A natural log plot of the second order rate constants vs. Ionization Potentials (IP) indicates that fluoroalkenes with IP values greater than 9.0 eV react by a concerted one step process.  Monofluoroalkenes with IP values less than 8.6 eV do proceed by a stepwise pathway.

Kinetics and studies on the reaction of chlorosulfonyl isocyanate with monofluoroalkenes

243rd National Meeting (2012)

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