Chlorosulfonyl isocyanate (CSI) is the most reactive isocyanate and it reacts with alkenes to give N-chlorosulfonyl-beta-lactams that are readily reduced to beta-lactams. beta-Lactams are a class of antibiotics. CSI was found to react with alkenes via a Single Electron (SET) pathway. However, the mechanism changes to a concerted pathway for reaction of CSI with monofluoroalkenes that have ionization potential O=C=N-X CSI: X=-SO2Cl Tosyl isocyanate: X= -SO2-C6H4-CH3 Trichloromethyl isocyanate: X= -CCl3 values greater than 8.9 eV. Quantum chemical calculations show that the nature of the transition state becomes more concerted as the isocyanate substituent (X) becomes less electron-withdrawing. In this study we use the radical trap reagent TEMPO to probe the concerted nature of less reactive isocyanates like p-Toluenesulfonyl isocyanate (X = -SO2-C6H4-CH3) and Trichloromethyl isocyanate (X = -CCl3).

Concerted nature of isocyanate reactions with alkenes

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.