Photoinduced Deaminative Borylation of Alkylamines

Abstract

An operationally simple deaminative borylation reaction of primary alkylamines has been developed. The formation of electron-donor-acceptor complexes between N-alkylpyridinium salts and bis(catecholato)diboron enables photoinduced single-electron transfer and fragmentation to carbon-centered radicals, which are subsequently borylated. The mild conditions allow a diverse range of readily available alkylamines to be efficiently converted into synthetically valuable alkylboronic esters under catalyst-free conditions.

Deaminative Borylation of Aliphatic Amines Enabled by Visible Light Excitation of an Electron Donor–Acceptor Complex

“…The borylation of primary amines has previously been reported for aromatic and benzylic amines through the use of the corresponding diazonium or trimethylammonium salts . However, the borylation of simple aliphatic amines remains an unresolved challenge in organic synthesis . One method to activate aliphatic primary amines is the formation of redox‐active pyridinium salts (Katritzky salts), which were originally used in two‐electron pathways .…”

Metal‐Free Radical Borylation of Alkyl and Aryl Iodides

“…[6] However,a ll these valuable methods require at ransition metal catalyst, al igand and as toichiometric amount of ab ase.T oo ur knowledge,m etal and additive-free radical borylation of alkyl halides with diborons is unknown. [7] Arylboronates can be obtained from haloarenes and diborons via reactive aryl radicals [8][9][10][11][12][13] (Scheme 1B). Along these lines,Marder developed azinc(II)-catalyzed borylation of aryl halides using astoichiometric base [8] and photoinduced aryl halide borylation was reported by Larionov, [9] Li [10] and Fu.…”

Selective C−N Borylation of Alkyl Amines Promoted by Lewis Base

“…[16] We envisioned that if the transient alkyl radical generated from Katritzky pyridinium salts and the stabilized boryl radical were formed in one reaction system, selective cross-coupling of these two species might lead to C(sp 3 ) À Bbonds. [17] Herein, we report our results on the utilization of pyridinium-salt-activated alkylamines as the electrophilic component in aL ewis base promoted deaminative borylation reaction ( Figure 1c).…”