Molecular Oxygen-Mediated Radical Alkylation of C(sp³)–H Bonds with Boronic Acids

Abstract

A direct and site-specific alkylation of (sp3)­C–H bond with aliphatic boronic acid was achieved. By simply heating glycinates and amines together with alkylboronic acids under an oxygen atmosphere, a variety of unnatural α-amino acids and peptides could be obtained in good yields.

Photoredox-Catalyzed Site-Selective Generation of Carbanions from C(sp3)–H Bonds in Amines

“…A yield of 60–70% was obtained (Schemes S4–S6), which is comparable to the small-scale synthesis. Moreover, the cleavage of the PMP protecting group was tested for the deuterated model compound 1 , applying a previously reported cerium ammonium nitrate method . Gratifyingly, the corresponding secondary amine was obtained, retaining the same deuterium incorporation (Scheme S7).…”

“…Moreover, the cleavage of the PMP protecting group was tested for the deuterated model compound 1, applying a previously reported cerium ammonium nitrate method. 58 Figure 5. Site-specific tritiation of complex molecules.…”

Molecular Oxygen‐Mediated Radical Cyclization of Acrylamides with Boronic Acids

“…For example, acyl‐, [7] polyfluoroalkyl‐, [8] phosphoryl‐, [9] thiocyanyl‐, [10] sulfonyl‐ and bromo‐substituted [11] indolo[2,1‐ a ]isoquinolinones were constructed from 2‐arylindoles via tandem radical addition/cyclization. On the other hand, organoboronic acid was demonstrated as an efficient radical precursor to construct C−C bonds in the past few years [2i–k,12–14] . However, except for Liu's work, 2i−2k these protocols suffered from usage of excess amounts of metal and/or nonmetal chemical oxidants.…”

Advances in free-radical alkylation and arylation with organoboronic acids

“…4 Interestingly, several elegant methods for direct radical alkylation/arylation of the (sp 3 )C–H bond with organoboronic acids have been developed independently by Lei, Huo and Liu. 5 In 2013, Lei and co-workers reported a first example of this conversion via Ni( ii )-catalysis. 5 a As depicted in Scheme 1, various saturated C–H bonds in ethers, amines and amides can be smoothly arylated with aryl boronic acids by a Ni(acac) 2 /PPh 3 -catalyzed free-radical process.…”