Copper(II) catalyzed cross-dehydrogenative coupling of cyclic benzylic ethers with simple carbonyl compounds by Na2S2O8

Recent Developments in Transition Metal‐Catalyzed Cross‐Dehydrogenative Coupling Reactions of Ethers and Thioethers

“…The fact that some substrates provided high yields of product led the authors to apply their methodology to target‐oriented synthesis. Hence, from 6‐methoxysalicylaldehyde the tetrahydropyranated product, an intermediate in the preparation of the immunomodulatory drug, tucaresol and analogues, could be obtained in 62 % yield, which suggests that this could be an alternative route to the known methods which use resorcinol as starting material . No work‐up was required for product purification and this method could provide an alternative to the protection of the phenolic hydroxyl group as an acetal, bypassing some of the problems encountered with other methods of protection…”

“…The reaction between ketones and cyclic benzyl ethers was revisited by Liu, Lou and co‐workers, who used peroxydisulfate (S 2 O 8 ) 2− as oxidant, in an attempt to develop an inexpensive method using easy‐to‐handle reagents of low toxicity. This was in fact the first application of sodium persulfate in CDC reactions of ethers . Both linear and cyclic ketones could be utilized, and high to very high yields of products were obtained (Scheme ).…”

Peroxydisulfate as an Oxidant in the Site‐Selective Functionalization of sp3 C–H Bonds

“…In 2014, two reports from Liu, Lou, and co‐workers described CDC protocols for uniting cyclic benzylic ethers (Scheme a) or N ‐carbamoyl tetrahydroisoquinoline (Scheme b) with diverse nucleophiles including carbonyl compounds and electron‐rich arenes ,…”

Regioselective Synthesis of 2,3,4-Trisubstituted Pyrroles via Pd(II)-Catalyzed Three-Component Cascade Reactions of Amines, Alkyne Esters, and Alkenes

“…Therefore, we herein report, for the first time, an efficient, general, and straightforward method for the one-pot cascade synthesis of important 2,3,4-trisubstituted pyrroles by a three-component assembly from simple and readily available amines, alkyne esters and alkenes (Scheme c). The versatile protocol is also novel for the Pd­(II)-catalyzed sequential reactions, in which thiosulfate acts as both an radical generating reagent and an organic oxidant …”

“…As shown in Scheme b, when the Pd­(II)-catalytic system was treated with a representative radical inhibitor, TEMPO (2,2,6,6-tetramethylpiperidine- N -oxyl), no desired product was detected upon addition of TEMPO. The results revealed that, in addition to the organic oxidant, K 2 S 2 O 8 acted as the radical-generating reagent for the catalytic cycle.…”