Brønsted Acid TfOH-Mediated [3 + 2] Cycloaddition Reactions of Diarylvinylidenecyclopropanes with Nitriles
摘要:
Diarylvinylidenecyclopropanes undergo a [3 + 2] cycloaddition reaction with MeCN in the presence of Bronsted acid TfOH to give the corresponding 3,4-dihydro-2H-pyn-ole derivatives 2 in moderate to excellent yields under reflux within a short time. As for the diarylvinylidenecyclopropane substrate containing a strongly electron-donating methoxy group on the benzene ring, the reaction leads to the formation of a different type of 3,4-dihydro-2H-pyrrole derivatives 4 under the same conditions.
development of this procedure has been the synthesis of a sulfonium salt bearing a trifluorovinyl substituent. This reagent suffers the addition of alcohols to the activated double bond and subsequently generates alkyl fluoride radicals by mesolytic cleavage of the S−C bond after one electron reduction.