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Benzylidene acetals, cleavage

Benzylidene acetals have the useful property that one of the two C—O bonds can be selectively cleaved. The direction of cleavage is dependent on steric and electronic factors as well as on the nature of the cleavage reagent. [Pg.129]

Reductive cleavage of the acrolein acetal proceeds similarly to that of the benzylidene acetals. ... [Pg.206]

In this type of cleavage reaction, it appears that the axial benzoate is the preferred product. If water is excluded from the reaction, a bromo benzoate is obtained.The highly oxidizing medium of 2,2 -bipyridinium chlorochromate and MCPBA in CH2CI2 at rt for 36 h effects a similar conversion of benzylidene acetals to hydroxy benzoates in 25-72% yield. ... [Pg.220]

Y. Niu, N. Wang, X. Cao, and X. Ye, Efficient formation and cleavage of benzylidene acetals by sodium hydrogen sulfate supported on silica gel, Synlett, 13 (2007) 2116-2120. [Pg.94]

Application of hydrogenolysis of benzylidene acetals to 2-amino-2-deoxy sugar derivatives was found to be possible.217 The reductive cleavage of benzyl 4,6-0-benzylidene-2-(benzyloxycarbonyl)amino-2-deoxy-a-D-glucopyranoside (209) gave, in a yield of 50%, a mixture of the 4-O-benzyl (210) and the 6-O-benzyl (211) derivatives. If the re-gioselectivity of this reaction, although notably inferior, was in ac-... [Pg.127]

Regioselective Cleavage of O-Benzylidene Acetals to Benzyl Ethers... [Pg.53]

Reductive cleavage, using the NaCNBHj-HCl-THF system to produce 2 -pro-penylidene acetals, produced the same regioselectivity as that found in benzylidene acetals [27] (Scheme 11), and also for the p-methoxybenzylidene acetals (Scheme 12) [27]. These observations open the way to further strategies for protecting group manipulations. [Pg.61]

Hexodialdoses have also been obtained by a-glycol cleavage in suitably substituted alditols. The 3,5-benzylidene acetal (172) of... [Pg.255]

Mechanism of regioselective reductive cleavage of benzylidene acetals... [Pg.42]

Benzylidene acetals can be oxidatively cleaved by jV-bromosuccinimide (NBS) to give 6-bromo-4-benzoyl-hexopyranosides (see Chapter 3). This reaction has also been performed on 1,2-0-benzylidene derivatives and it appears that the cleavage reactions result in the formation of a derivative that has an axial benzoyl ester.33... [Pg.43]

See other pages where Benzylidene acetals, cleavage is mentioned: [Pg.356]    [Pg.120]    [Pg.49]    [Pg.80]    [Pg.613]    [Pg.771]    [Pg.790]    [Pg.136]    [Pg.289]    [Pg.82]    [Pg.92]    [Pg.132]    [Pg.289]    [Pg.53]    [Pg.150]    [Pg.299]    [Pg.262]    [Pg.263]    [Pg.209]    [Pg.225]    [Pg.226]    [Pg.45]    [Pg.49]    [Pg.223]    [Pg.42]    [Pg.56]    [Pg.82]    [Pg.229]    [Pg.60]    [Pg.248]    [Pg.274]    [Pg.166]   
See also in sourсe #XX -- [ Pg.55 ]



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0-benzylidene acetals reductive cleavage

Benzylidene acetals

Benzylidene acetals, regioselective cleavage

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