Active Cobalt Catalyst for the Cleavage of Benzyl Ether

Abstract

An improved method for the deprotection of benzyl ethers using a catalytic amount of Co(2)(CO)(8) in the presence of Me(2)PhSiH and CO (1 atm) is described. The deprotection reaction is compatible with double bond or sulfur-containing substrates. The method also tolerates other functional groups, such as Ac, Piv, and Bz, and shows potential selectivity in perbenzylated monosaccharides.

Additional Nucleophile-Free FeCl₃-Catalyzed Green Deprotection of 2,4-Dimethoxyphenylmethyl-Protected Alcohols and Carboxylic Acids

“…4-MPM ethers are generally deprotected by the use of a stoichiometric amount of oxidants [2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) 2,3) and ceric ammonium nitrate (CAN) 4,5) ], Pd/C-catalyzed hydrogenation under atmospheric hydrogen gas 1) or the combination of a stoichiometric amount of nucleophiles and the catalytic or stoichiometric Lewis acids [6][7][8][9][10][11][12][13][14][15][16][17] [Chart 1, (a)-(d)]. However, the stoichiometric byproducts derived from 4-MPM protective groups (e.g., anisaldehydes, and toluene derivatives) and the acidic residues derived from reagents when using DDQ and CAN should be removed from the reaction mixture by the purification process using silica-gel column chromatography.…”

“…The 2,4-DMPM esters derived from branched aliphatic carboxylic acids were also effectively deprotected into the corresponding carboxylic acids in nearly quantitative yields (entries 13,14). The alkene, alkyne, ketone, tetrahydropyranyl (THP) ether and TBS ether were all tolerable under the deprotection conditions and only the deprotection of 2,4-DMPM could be achieved (entries [15][16][17][18][19]. The 2,4-DMPM-protected benzoic acid derivatives were also adaptable to the present deprotection (entries 20, 21).…”

A mild and efficient method for the selective cleavage of primary p-methoxybenzyl protecting group of saccharides by Co2(CO)8–Me2PhSiH–CO system

“…Previous work in our laboratory has identified Co 2 (CO) 8 -hydrosilane-CO system as an effective method for the selective cleavage of benzyl ether. 9, 10 Various substrates have been tested to show its broad applications and high functional groups tolerance. 10 Since PMB ether is similar to benzyl ether, we presume this mild method is also applicable for the selective cleavage of PMB ether.…”

“…9, 10 Various substrates have been tested to show its broad applications and high functional groups tolerance. 10 Since PMB ether is similar to benzyl ether, we presume this mild method is also applicable for the selective cleavage of PMB ether. Based on these considerations, a model reaction was established using 1a as the substrate to investigate the reaction conditions (Table 1).…”

“…[9][10][11][12] The reactivity of hydrosilane determines the reaction rate of the cleavage process. Therefore, five hydrosilanes were firstly screened in the presence of 2.0 equiv of Co 2 (CO) 8 in benzene under balloon pressure of CO at 50°C (Table 1, entries 1-6).…”