Palladium on Carbon‐Catalyzed Benzylic Methoxylation for Synthesis of Mixed Acetals and Orthoesters. Issue 46 (31st July 2017)

• Record Type: Journal Article
• Authors: Yasukawa, Naoki; Kanie, Takafumi; Kuwata, Marina; Monguchi, Yasunari; Sajiki, Hironao; Sawama, Yoshinari
• Is Part Of: Chemistry. Volume 23:Issue 46(2017)
• Page Start: 10974
• Page End: 10977
• Publication Date: 2017-07-31
• Subjects: carbon -- green chemistry -- heterogeneous catalysis -- oxygen -- palladium; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201702278
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The palladium on carbon (Pd/C)‐catalyzed direct methoxylation of the benzylic positions of linear benzyl and cyclic ether substrates proceeded in the presence of i ‐Pr2 NEt under an oxygen atmosphere to give the corresponding mixed acetals. Cyclic acetal derivatives could also be converted into orthoesters. The present direct methoxylation via a carbon‐hydrogen (C−H) functionalization can be accomplished using the easily‐removed Pd/C and molecular oxygen as a green oxidant. The obtained mixed acetals were transformed into the corresponding ether products by chemoselective substitution of the methoxy group using a silyltriflate, 2, 4, 6‐collidine, and a nucleophile. The orthoester derivative could also be transformed into the cyclic ketal under similar reaction conditions. Abstract : The direct synthesis of mixed acetals and orthoesters from the corresponding benzylic ethers has been accomplished using a palladium on carbon (Pd/C) catalyst in MeOH under an oxygen atmosphere in the presence of i ‐Pr2 NEt. The present catalytic method using molecular oxygen as a clean oxidant and easily‐recovered Pd/C is valuable from the viewpoint of green sustainable chemistry.