Epoxide opening benzyl alcohol

Red-Al) or the Z-olefin 341 after benzylation. Stereoselective dihydroxylation and regiose-lective protection of the diol provides protected polyol 342 that is transformed in three steps to terminal epoxide 343. Removal of the p-methoxybenzyl group followed by acid-catalyzed epoxide opening yields exclusively tetrahydropyran 344 after protection of the primary alcohol and deacetylation. Inversion of the C2 stereocenter by an oxidation-reduction sequence and deprotection furnishes the C-mimic of a,a-trehalose 345. 

Benzyl alcohol or sodium benzoxide have been found to add readily to epoxides in the instances reported. Sodium benzoxide opens 5,6-anhydro-... 

Halohydrins Opening of 1,2-epoxide ring by halogen at room temperature to afford l-halo-2-alkanols is catalyzed by this heterocycle (14 examples, 80-99%). Thus, styrene oxide gives a-halomethyl benzyl alcohols. 

Acylation with 8 moves the imine to an enamine 9 and opening the lactone with the lithium alkoxide of benzyl alcohol gives the epoxide 10 ready for the key cyclisation. 

By attaching formyl groups [106] and reducing them to hydroxymethyl moieties, benzylic alcohol functions can be formed [108], which enhances the polymerization rates when used with epoxides in Brpnsted-acid-catalyzed ring-opening cationic polymerizations. As termed by Penczek and Kubisa, the polymerization follows a mechanism called the activated monomer mechanism (Scheme 11.29) [109-112],... 

A further route to P-mannopyranosides involves use of the 1,2-anhydride 33, made by the Danishefsky method from tri-O-benzyl-D-glucal. Epoxide ring opening with alcohols in the presence of zinc chloride gives P-glucosides which, by oxidation and reduction, lead to the P-mannosides including P-mannosyl disaccharides. Danishefsky has also adapted compound 33 for use as a precursor of a-glucosides. Treated with tributylstannylated alochols in the presence... 

A mixture of epoxides 483 obtained on oxidation of 482 with dimethyldioxirane, when exposed to ferric chloride provided, as the kinetically controlled product, the a-aldehyde 484, which without purification was reduced to the a-alcohol 485. The exclusive formation of 484 is believed to occur via the benzyl cation 486, generated by Lewis-acid opening of the oxirane ring, suffering a stereospecific kinetic 1,2-hydride shift The amino alcohol 487 obtained after sequential removal of O-benzyl and N-tosyl groups from 485, on treatment with triphenylphosphine and iodine in the presence of imidazole furnished the tetracyclic base 488, which was oxidised to the ketone 489. Trapping of the kinetically generated enolate of 489 as the silylether, followed by palladium diacetate oxidation yielded the enone 490. The derived... 

Several catalysts have been found for the ring opening of epoxides. For instance, cyclohexene oxide gave an excellent yield of the trans-fi-amino alcohol when treated with either aromatic or aliphatic amines in the presence of a scandium triflate catalyst.21 Aromatic epoxides react in a regiospeciflc reaction at the benzylic carbon when treated with aromatic amines and scandium triflate but at the least substituted carbon of the epoxide ring when aliphatic amines react. Electronic effects are more important in the reactions of the aromatic epoxides whereas steric factors control the reaction with aliphatic epoxides. 

InCh was found to catalyse the ring opening of substituted epoxides by alcohols giving /3-hydroxy ethers.25 Epoxides with a phenyl substituent reacted at the benzyl carbon in an, SN-1 -like. Sx2 reaction whereas those with an alkyl substituent reacted at the least substituted carbon by an S 2 mechanism. 

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