Selective alkylation by photogenerated aryl and vinyl cation

Abstract

Seven para-substituted phenyl cations and the parent phenyl cation were prepared from iodonium salt precursors. Product studies revealed remarkable chemoselectivity and regioselectivity that could be related to the spin multiplicity of the cations. Also an universal method to fingerprint singlet and triplet aryl cations was developed. Next, the 1- and 2-naphthyl, 9-phenanthryl and 9-anthryl cations were generated from a variety of precursors. Product studies were used to reveal the initial multiplicity of the cations. The generation and selectivity of aryl cations was put to use studying their profitable reactions with guanosine and phenylalanine. Finally, the powerful iodonium photochemical leaving group ability was employed to generate cyclic vinyl cations. Apart from the 1-cyclohexenyl cation, unequivocal evidence was found for the generation of the 1-cyclopentenyl cation.