Facile synthesis of α-aminoboronic acids from amines and potassium acyltrifluoroborates (KATs)viatrifluoroborate-iminiums (TIMs)

Abstract

We report the formation of iminium-trifluoroborates (TIMs) from potassium acyltrifluoroborates (KATs) and the synthesis of α-aminotrifluoroborates and α-aminoboronic acids from TIMs.

Synthesis of secondary and tertiary amides without coupling agents from amines and potassium acyltrifluoroborates (KATs)

“…1). 8 Given their ease of formation, we hypothesized that TIMs could also serve as intermediates to secondary and tertiary amides via oxidation. Using TIM 1a as a model substrate, we screened oxidation conditions and found successful formation of the desired tertiary amide with several oxidants and basic additives under a variety of conditions (detailed screening data can be found in the ESI †).…”

“…The TIMs are formed under simple conditions by mixing KATs and amine salts and their oxidation occurs rapidly and chemoselectively. 8 Although KATs are far less common starting materials than carboxylic acids, they are increasingly available from commercial sources or a plethora of recently reported methods for conversion of common starting materials to KATs. In the past few years, their syntheses from aryl halides, 9 Grignard reagents, 10 aldehydes, 11 vinyl boronic acids, 12 alkynes, 13 and acid chlorides 14 have been reported.…”

Synthesis of Polymers Containing Potassium Acyltrifluoroborates (KATs) and Post‐polymerization Ligation and Conjugation

“…[14] Acyltrifluoroborates can be accessed from trifluoroborate-iminiums (TIMs) upon hydrolysis. [11] Motivated by the stability and solubility of zwitterionic TIMs,wee nvisioned TIM-bearing monomers as being ideal for controlled polymerization. Zwitterionic polymers have been reported to display unique properties including self-assembly and stimuli-responsive behavior.…”

“…[10] In situ hydrolysis of the TIM functional group affords watersoluble OEGMA-KATc opolymers and water/THF-soluble MMA-KATc opolymers containing polar KATf unctional groups. [11] These polymers undergo direct, quantitative postpolymerization amide-bond formation with molecules containing hydroxylamines or in situ generated N-chloroamines. [12] Polymers that contain as ingle KATm oiety at aterminus are synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization [13] utilizing aTIMbearing RAFT agent.…”

Concise Synthesis of Potassium Acyltrifluoroborates from Aldehydes through Copper(I)‐Catalyzed Borylation/Oxidation

“…Since this seminal work, the preparation and reactivity of acylborons have been studied enthusiastically . Among these acylboron species, potassium acyltrifluoroborates (KATs) are of particular interest due to their unique reactivity and remarkable stability toward air and moisture ,. In 2012, Dumas, Bode, and Molander reported a highly chemoselective and rapid amide‐bond‐forming reaction between KATs and hydroxylamines, that is, KAT ligation .…”