Mild direct amination of benzoxazoles using interpenetrating Cobalt(II)-based metal-organic framework as an efficient heterogeneous catalyst

Metal–organic framework (MOF)-, covalent-organic framework (COF)-, and porous-organic polymers (POP)-catalyzed selective C–H bond activation and functionalization reactions

“…A Co-MOF containing unsaturated Co II sites with the molecular formula ([Co(tcpa)(Fbtx)(H 2 O) 2 ] 0.5H 2 O) n (tcpa = 3,4,5,6-tetrachlorophthalate; Fbtx = 1,4-bis(1,2,4-triazole-1-ylmethyl)-2,3,5,6-tetrafluorobenzene) was synthesized via the reaction between Co(OAc) 2 ·4H 2 O and mixed linkers of Fbtx and H 2 tcpa. 98 The resulting MOF showed good chemical stability in dilute acidic and basic aqueous solutions. The catalytic activity of Co-MOF was examined in the intermolecular C–H amination between benzoxazoles and secondary amines in acetonitrile medium and in the presence of tert -butyl hydroperoxide (TBHP) oxidant and acid acetic (Scheme 34).…”

Microwave-Enhanced On-Water Amination of 2-Mercaptobenzoxazoles To Prepare 2-Aminobenzoxazoles

“…To shed light on the mechanism, several mechanistic experiments were conducted (Scheme 4). We performed our reaction using 2-(methylthio)benzo[d]oxazole (11) as a starting material under the optimized condition. No product 7a was observed, and only starting material 11 was recovered.…”

“…Although this is a very efficient route, the process requires multiple preparation steps and uses toxic halogenated reagents, which often produce undesirable byproducts during the reaction. Recently, direct C–H amination of benzoxazole 5 into target amino compound 7 was introduced, utilizing a transition metal catalyst, such as Cu, Ag, Mn, and Co in just one step. − Although this reaction has high atom economy, toxic metals are used. Another important method is direct synthesis from 4 with either isocyanate or isocyanide as amine surrogates.…”

Recent Advances and Prospects in the Amination of Benzoxazoles

“…Cobalt(II) metal‐organic framework‐catalyzed amination of benzoxazole was disclosed by He and co‐workers [45] . The crystalline form of Co‐MOF {[Co(tcpa)(fbtx)(H 2 O) 2 ].0.5H 2 O} n , which is commercially unavailable, was found to be the best catalytic system under the reaction conditions.…”

“…Cobalt(II) metal-organic framework-catalyzed amination of benzoxazole was disclosed by He and co-workers. [45] The crystalline form of Co-MOF {[Co(tcpa)(fbtx)(H 2 O) 2 ].0.5H 2 O} n , which is commercially unavailable, was found to be the best catalytic system under the reaction conditions. The utmost catalytic activity was achieved with tert-butyl hydroperoxide (TBHP) and acetic acid as the oxidant and additive respectively and the reaction was conducted at 25 °C for 12 h. The effect of changing the substituents in the benzene ring of benzoxazole was examined, which offerred good to high yields in all cases.…”