Electrophilic [N—F]⁺ catalysed asymmetric allylation of (E)‐N,1‐diphenylmethanimine

Abstract

New efficient catalysts based on electrophilic N‐fluoro quaternary ammonium salts are reported for catalytic allylation of (E)‐N,1‐diphenylmethanimine. The chiral version of the catalyst based on cinchonidine (F‐CD‐BF4) shows high catalytic activity with approximately 94% ee and TOF (>800 h−1). The F‐CD‐BF4 is prepared from cinchonidine and Selectfluor by one‐step transfer fluorination.

Benzoates as photosensitization catalysts and auxiliaries in efficient, practical, light-powered direct C(sp3)–H fluorinations

“…Even protected 1° amide 7 did not fluorinate in this case. One explanation could be that if the desired reactivity is too slow, nucleophilic destruction of SelectFluor (known to occur with 1° and 3° amines) 13 may emerge as a competitive thermal reaction, arising lower yields or no reactivity. The steric hindrance of 3° alcohols – the only class of free alcohols that worked in the previous reports – may explain their tolerance.…”

N‐Fluoro Ammonium Salts of Cinchona Alkaloids in Enantioselective Electrophilic Fluorination

“…In the same vein but more successfully, the allylation of ( E )‐ N ‐benzylideneaniline using allyltributyltin in the presence of F‐CD‐BF 4 afforded the corresponding enantioenriched amine with 94 % ee (Scheme 25). [60] A single example was provided with HPLC trace but the mechanism was not investigated. It was proposed that the chiral [N−F] + reagent behaves as a Lewis acid to activate the imine moiety in the nucleophilic allylation.…”

Recent Advances in the Application of Selectfluor as a “Fluorine‐free” Functional Reagent in Organic Synthesis

“…Very recently, the Sharma group discovered a Selectfluorcatalysed selective allylation reaction of imines (Scheme 20a). [38] In this study, Selectfluor was proposed to behave as a Lewis acid catalyst for the activation of an imine in a nucleophilic addition process. Futhermore, a Selectfluor-catalyzed oxidative cyclization reaction of ynamide to oxazolidine-2,4-dione was studied by the Luo and He group (Scheme 20b).…”