Mild and efficient deprotection of allyl ethers of phenols and hydroxycoumarins using a palladium on charcoal catalyst and ammonium formate

Development of the Applications of Palladium on Charcoal in Organic Synthesis

“…Ganguly's group described the Pd/C‐catalyzed hydrogenolysis of allyl phenyl ethers and allyl coumarinyl ethers via cleavage of C−O bond in combination with ammonium formate at room temperature [Eq. (57)] . A remarkable example of the regioselective synthesis of mono‐ O ‐alkylated homooxacalix[3]arenes via a protection–deprotection strategy was reported by Yamato et al.…”

Safe Removal of the Allyl Protecting Groups of Allyl Esters using a Recyclable, Low‐Leaching and Ligand‐Free Palladium Nanoparticle Catalyst

“…It is noteworthy,h owever, that the starting material 1a was recoveredi n6and 25 %y ields from these reactions,r espectively. Controle xperiments were performed in the absence of SAPd andi nt he presence of Au-mesh instead of SAPd (Table 1, entries 10 and 11), both of which gaveo nly at raceo f2a even when the reactionw as conducted for al onger time.E ntry 12 shows that the conventional reaction conditions using Pd/C [7] gave the desired product 2a in 82 %y ield. Thea mounts of Pd leached into the reaction mixture by SAPd and an Pd/Cw ere determined by inductively coupled plasma resonance spectroscopy,a nd the results of these experiments will be described later in this article.F igure 2s howsaproposed reaction mechanism for the removal of the allyl-protecting group of allyl ester using ac ombination of aP dc atalyst and formic acid.…”

Recent advances in 4-hydroxycoumarin chemistry. Part 1: Synthesis and reactions

“…Scheme 6. Ganguly et al (2006) has described an efficient procedure for synethesis of 4-hydroxycoumarin 1 via the cleavage of 4-allyl coumarinyl ether using a catalytic amount of palladium on activated charcoal in methanol, and in combination with ammonium formate (Scheme 7). Recently, it was reported that the molecular iodine catalyzed this reaction (Nawghare et al, 2014).…”