Enthalpic and Polar Effects in the Reactions of Perfluoroalkyl Radicals. New Selective Synthetic Developments with Alkenes and Heteroaromatic Bases.

Abstract

In the presence of alkenes perfluoroalkyl radicals add very rapidly to the double bond and the polar character of the radical adduct is reversed, allowing the selective substitution of protonated heteroaromatic bases. The mechanism of the reaction and the key role of enthalpic and polar effects are discussed. -(ANTONIETTI, F.; MELE, A.; MINISCI*, F.; PUNTA, C.; RECUPERO, F.; FONTANA, F.; J. Fluorine Chem. 125 (2004) 2, 205-211; Dip. Chim., Politec. Milano, CNR, I-20131 Milano, Italy; Eng.) -M. Paetzel 21-028

Heteroarene Phosphinylalkylation via a Catalytic, Polarity-Reversing Radical Cascade

“…This C-centered radical may then chemoselectively combine with heteroarenes to afford a three-component coupling adduct. To our knowledge, only Minisci, Barriault, Liu, and Hong have reported examples of heteroaryl difunctionalization of alkenes, albeit initiated by alkyl or azide radicals . Despite this inspiration, we were cognizant that hydrophosphinylation via the Pudovik reaction may be a competing pathway .…”

Photocatalytic Minisci Reaction

“…At the same time, catalytic quantities of cobalt(II) salts in the presence of oxygen were used together with N-hydroxyphthalimide to promote the acylation of bases [20]. Similarly, nucleophilic fluorinated radical intermediates allowed to insert perfluoroalkyl substituents onto heteroaromatic bases (Scheme 12, product 12) [22] and quinones (Scheme 12, product 13) [23]. Similarly, nucleophilic fluorinated radical intermediates allowed to insert perfluoroalkyl substituents onto heteroaromatic bases (Scheme 12, product 12) [22] and quinones (Scheme 12, product 13) [23].…”