Photochemical benzylic bromination in continuous flow using BrCCl3 and its application to telescoped p-methoxybenzyl protection
BrCCl3 represents a rarely used benzylic brominating reagent with complementary reactivity to other reagents. Its reactivity has been revisited in continuous flow, revealing compatibility with electron-rich aromatic substrates. This has brought about the development of a p-methoxybenzyl bromide generator for PMB protection, which was successfully demonstrated on a pharmaceutically relevant intermediate on 11 g scale, giving 91% yield and a PMB-Br space-time-yield of 1.27 kg L?1 h?1
Otake, Yuma,Williams, Jason D.,Rincón, Juan A.,De Frutos, Oscar,Mateos, Carlos,Kappe, C. Oliver
p. 1384 - 1388
(2019/02/14)
Anthracene-rhodium complexes with metal coordination at the central ring-a new class of catalysts for reductive amination
A new class of anthracene complexes with a metal coordinated at the central ring was applied in catalysis for the first time. As a result, a simple and efficient protocol for reductive amination that involves CO as a reducing agent has been developed. The rhodium complex [(cyclooctadiene)Rh(C10H4Me2(OMe)4)]+ (1 mol%) catalyses such reactions under mild conditions (40-130 °C) and produces a variety of amines in good yields (74-95%) without affecting the functional groups. The protocol is acceptable for all combinations of aldehydes (aromatic and aliphatic), ketones (aromatic and aliphatic) and amines (aromatic and aliphatic; primary and secondary).
Cu(II)-Catalyzed ortho-Selective Aminomethylation of Phenols
A Cu(II)-catalyzed ortho-selective functionalization of free phenols with trifluoroborates to afford Csp2-Csp3 coupling products under mild conditions has been developed. A variety of functional groups on the phenol and the potassium aminomethyltrifluoroborate substrates were found compatible, furnishing the corresponding products in moderate to excellent yields. A single-electron transfer radical coupling mechanism involving a six-membered transition state is proposed to rationalize the high levels of ortho-selectivity in the reaction. This protocol provides straightforward access to ortho-aminomethyl-substituted phenols, unnatural amino acids and other bioactive small molecules.