Heterocyclic group transfer reactions with I(iii) N-HVI reagents: access to N-alkyl(heteroaryl)onium salts via olefin aminolactonization

Abstract

Complex N-alkyl (heteroaryl)onium salts are accessed via heterocyclic group transfer reactions of N-ligated I(iii) reagents with alkenoic acids. The reactions proceed in excellent yields, under mild conditions, and with broad substrate scope.

Updates on hypervalent-iodine reagents: metal-free functionalisation of alkenes, alkynes and heterocycles

“…90 Considering their importance to the scientific community a (bis)cationic nitrogen-ligated I( iii ) HVI reagent, or an N -HVI mediated synthesis of N -alkyl(heteroaryl)onium salts via the aminolactonisation of alkenoic acids ( 51 ) has been reported by the Wengryniuk group in 2021. 91 The present protocol utilises N -HVIs as the heterocyclic group transfer reagents to provide a broad range of N -alkyl(heteroaryl)onium salts ( 52 ) under mild conditions. The proposed mechanism involves olefin activation followed by 5- exo-trig lactonisation to form an intermediate (alkyl)(aryl)iodonium salt ( B ).…”

“…113 Owing to their importance, the synthesis of isoxazolines and isoxazoles has become an interesting area of research. [114][115][116] In this regard, a one-pot, regioselective 1,3dipolar cycloaddition of in situ generated (diethoxyphosphoryl) difluoromethyl nitrile oxide (91) with alkenes and alkynes has been reported by the Pajkert group. This protocol enables facile access to 3,5-disubstituted isoxazolines (92) and isoxazoles bearing a CF 2 P(O)(OEt) 2 moiety in good to excellent yields, under mild reaction conditions (Scheme 57).…”

“…This protocol enables facile access to 3,5-disubstituted isoxazolines (92) and isoxazoles bearing a CF 2 P(O)(OEt) 2 moiety in good to excellent yields, under mild reaction conditions (Scheme 57). 117 In the proposed mechanism, the acetoxy group of DIB is replaced by a nucleophilic attack from the aldoxime oxygen (91) Similarly, the He group reported a PIDA-mediated trifluoromethylthiolation/oxidative cyclisation of ynamides (93) with the Shen reagent giving easy access to CF 3 S-functionalised oxazolidine-2,4-diones (94). The desired products bearing a quaternary carbon centre were obtained in 38-85% yields with chemoselectivities of up to 99/1 (Scheme 59).…”

Iodine-based reagents in photoredox-organocatalysis

“…Several reviews are covering the role of HIRs as group transfer reagents, oxidizing agents, and synthetic applications with metal-based photocatalysts. [40][41] Studer and Wang recently published a review article where they have shown the use of Iodine(III) reagents in the radical chemistry as group transfer reagents [42][43] via thermolysis. 44 However, this particular review highlights the merging of HIRs as group transfer and oxidizing reagent with organophotocatalyst (OPC).…”

Site-Selective Synthesis of 2,4,6-Collidinium Salts via Electrooxidative C–H Functionalization

“…13 Our laboratory has a growing interest in developing novel oxidative strategies for the conversion of alkenes and C-H bonds directly to N-alkyl and N-aryl pyridinium salts. 15 Inspired by the Weaver report, we felt that a method enabling the direct synthesis of benzylic pyridinium salts via oxidative C-H amination would be of high value. Such a method could broaden the scope of accessible pyridinium scaffolds as well as obviate the need for prefunctionalized benzylic halides and potentially proceed under more mild conditions.…”