Allyl esters hydrogenolysis

Asymmetric hydrogenolysis of allylic esters with formic acid with satisfactory ee was observed[387], Geranyl methyl carbonate (594) was reduced to 570 with formic acid using l,8-bis(dimethylamino)naphthalene as a base and MOP-Phen as the best chiral ligand, achieving 85% ee. 

Tributyltin hydride is used for hydrogenolysis of allylic esters[369-372]. 

Hydrogenolysis of the diallyl alkylmalonate 757 with formic acid in boiling dioxane affords the monocarboxylic acid 758. Allyl ethyl malonates are converted into ethyl carboxylates[471]. The malonic allyl ester TV-allylimide 759 undergoes smooth deallylation in refluxing dioxane to give the simple imide 760(472]. The allyl cyanoacetate 761 undergoes smooth decarboxylation to give... 

The hydrogenolysis of the allyl ester 315 produced 316 regio- and stereoselectively. The free allyl alcohol in the same molecule was not attacked [136],... 

The susceptibility of the allylic ester group in tri-O-acetyl-D-glucal to hydrogenolysis in the presence of various catalysts has been carefully studied. Platinum catalysts (with ethyl acetate as the solvent) mainly caused direct additions (85%) to the double bond, whereas the incorporation of small proportions of dimethylamine promoted hydrogenolysis, so that 4,6-di-0-acetyl-l,5-anhydro-2,3-dideoxy-D-en/fJiro-hexitol was obtained in 95% yield. In the absence of added base, palladium catalysts would be expected to afford uncomplicated addition.38... 

In the presence of main group organometallic compounds, ketones are obtained. Carbonylation of allylic ester 382 with alkylzinc reagent afforded the ketone 383 in high yield [149]. Carbonylation of allyl chloride 384 in the presence of tin hydride afforded the -unsaturated aldehyde 385 via hydrogenolysis of acylpalladium intermediate [150]. 

Deprotection of allyl ester in 467 with HC02H/Et3N was highly chemoselec-tive. In the coexistence of a 2,4-enyne system in 467, at first 7r-allylpalladium carboxylate 468, formed from the allyl ester, attacked the triple bond to form the butenolide 469 without reacting with formate. Hydrogenolysis with formate took place only at the final step to afford 470 chemoselectively. Also, the alkenyloxirane group, which is allylic epoxide, stayed intact [175],... 

In connection with the finding that a combination of a Pd catalyst and ammonium formates is effective for hydrogenolysis of allyl esters to olefins, and of propargyl carbonates to allenes, the reactions with allyl ester of alkynyl acid and propargyl acetate under the reaction conditions shown in Scheme 4 were investigated. The results indicate that in both cases reduction of the triple bond takes preference over hydrogenolysis as sununa-rized in Scheme 5. 

A benzyl carbonate was prepared in 83% yield from the sodium alkoxide of glycerol and benzyl chloroformate (20°, 24 h). It was also prepared by a lipase-catalyzed ester exchange with allyl benzyl carbonate. It is cleaved by hydrogenolysis (H2/Pd-C, EtOH, 20°, 2 h, 2 atm, 76% yield) and electrolytic reduction (—2.7 V, R4N X, DMF, 70% yield). A benzyl carbonate was used to protect the hydroxyl group in lactic acid during a peptide synthesis." ... 

The same basic strategy was applied to the synthesis of the smaller fragment benzyl ester 28 as well (Scheme 4). In this case, aldehyde 22 prepared from (S)-2-hydroxypentanoic acid [9] was allylated with ent-10 and tin(IV) chloride, and the resulting alcohol 23 was converted to epimer 24 via Mitsunobu inversion prior to phenylselenenyl-induced tetrahydrofuran formation. Reductive cleavage of the phenylselanyl group, hydrogenolysis of the benzyl ether, oxidation, carboxylate benzylation, and desilylation then furnished ester 28. 

Refluxing with zinc in ethanol reduced a-bromocinnamic acid to cinnamic acid in 80% yield [997]. Allylic chlorines in y,y,y-trichlorocrotonic acid were partly or completely hydrogenolyzed by zinc and sodium amalgam [5/9]. Hydrogenolysis of allylic bromine in oc, -unsaturated esters with zinc in acetic acid gave predominantly, y-unsaturated esters in 65-97% yields [998]. 

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