Cobalt‐Catalyzed Dehydrogenative Coupling of Alcohols/Aldehydes and Amines: An Important Role for Imine Hydration

Abstract

Ac obalt and iodide co-catalyzedo xidative amidation reaction between alcohols or aldehydes and amines has been developed. The reactions proceeded smoothly under mild conditions using tert-butyl hydroperoxide solution in water as the terminal oxidant, with broad functional group tolerance. Mechanistic studies indicated that the tBuO·/ tBuOO· radicalg enerated in situ is the active speciesr esponsible for hydrogen abstraction in this catalytic process, and not IO À /IO 2 À /IO 3 À ions. Investigation into the reaction mechanism also revealed the potentialt ransiency of ah emiaminal and the important role of its regenerationb yi mine hydration.

Visible Light‐Driven Efficient Synthesis of Amides from Alcohols using Cu−N−TiO2 Heterogeneous Photocatalyst

“…Simple NÀ TiO 2 gave a lower yield (20 %, entry 10), which indicates the copper loading on TiO2 is critical. Next, a screening of solvents was carried out and found DMF, DCE, ethanol, and BTF are ineffective, no product was observed (entries [11][12][13][14], so the solvent choice is critical and acetonitrile found to be superior. When we carried out the reaction with 3 W blue LED light, a similar yield was observed (entry 15) Finally, when carried out the reaction at dark even after 16 h no product formation was observed (entry 16), indicates the necessity of light and photocatalysis pathway of the reaction.…”

“…In 2007, Milstein and co‐workers 1 st reported environmentally benign direct amidation of alcohols and amines using the ruthenium PNN pincer complex as a catalyst [5] . Since then several groups have reported the direct synthesis of amides from alcohols mainly using, homogeneous Ru, [6] Rh, [7] Ir, [8] Fe, [9] Cu, [10], and other transition metal catalysts [11] . Supported Ag, [12] Au, [13] and heterogeneous Mn [14] catalyst also reported for amidation of alcohol.…”

“…[5] Since then several groups have reported the direct synthesis of amides from alcohols mainly using, homogeneous Ru, [6] Rh, [7] Ir, [8] Fe, [9] Cu, [10], and other transition metal catalysts. [11] Supported Ag, [12] Au, [13] and heterogeneous Mn [14] catalyst also reported for amidation of alcohol. These methods have the advantages of environmentally benign and atom efficiency from the traditional acid chloride or coupling reagents-based amide bond synthesis.…”

“On Water” Metal-Catalyst-Free Oxidative Coupling–Amidation of Amines To Access Imines and Amides

“…In the same pot, 2a was subjected to another 0.5 equiv of NaOCl affording amide 3a after a total reaction time of 24 h. This result suggests that amides could be obtained from the subsequent oxidation of imines delivered in the oxidative coupling step. Indeed, previous reports have demonstrated the oxidation of imines to amides through different operative pathways. − …”

Carbonyl Compounds′ Journey to Amide Bond Formation

“…Guo et al. developed a direct oxidative amidation of aldehydes with amine hydrochlorides by using a CoI 2 /TBHP system in MeCN at 70 °C under basic conditions, thereby providing the corresponding amides in good‐to‐excellent yields (Scheme ) . Primary and secondary amines that contained other reactive functional groups were efficiently converted under these reaction conditions.…”