Trifluoromethyl-substituted superelectrophiles were generated in superacid (CF3SO3H) and their chemistry was examined. The strong electron withdrawing properties of the trifluoromethyl group are found to enhance the electrophilic character at cationic sites in superelectrophiles. This leads to greater positive charge-delocalization in the superelectrophiles. These effects are manifested by the superelectrophiles showing unusual chemo-, regio-, and stereoselectivity in reactions.

The superacid-promoted reactions of vinyl-substituted N-heterocycles have been studied. Diprotonated pyrimidines, quinoxalines, and quinazolines exhibit an unusual regioelectronic effect that controls the type of addition reaction observed. Depending on the ring position of the vinyl-substituent, either conjugate addition or Markovnikov addition occurs. The mode of addition has been shown to correlate well to NBO calculated charges.

No abstract

In this Note, we describe superacid-promoted cyclodehydrations leading to functionalized indenes. The product indenes are synthesized having N-heterocyclic substituents, including pyridyl, imidazolyl, pyrimdyl, and other groups. A mechanism is proposed involving dicationic, superelectrophilic intermediates. The protonated N-heterocyclic rings are shown to dramatically lower the LUMO energy level of the carboxonium electrophile (compared to that of a similar uncharged system).

A superacid-promoted method for the synthesis of 9,9-diarylfluorenes is described. The chemistry involves cyclizations and arylations with biphenyl-substituted heterocyclic ketones and a mechanism is proposed involving superelectrophilic intermediates. The key reactive intermediates-dicationic and trication fluorenyl cations have been observed by low-temperature NMR and the mechanism has been further studied using DFT calculations.