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Carbinols chemoselectivity

In 1997, Taguchi, Hanzawa and coworkers described the formation of cyclopropyl carbinols from alkenyl oxiranes through chemoselective hydrozirconation followed by intramolecular attack of the generated alkylzirconocene on the epoxide ring (Scheme 18) [27]. Both the reactivity and the selectivity patterns are worthy of note. The sequence was made possible owing to the chemoselective hydrozirconation of the alkene in the presence of oxirane. Despite the poor nu-... [Pg.118]

The reaction of MeTi(OPi )3 with a 1 1 molar ratio of the isomeric hexanal (37) and 2-ethylbutanal (38) affords a mixture of the carbinols (39) and (40) in a 92 8 molar ratio (equation 19). Another example of stereocontrol in the chemoselectivity of these reagents is represented by the cross reactions of the ketone pairs (41) and (42) (equation 20) or (42) and (45) (equation 21). It is worthy of note that the same 1 1 molar mixture of (42) and (45) reacts more or less statistically with MeLi, affording about 50% of both (44) and (46). ... [Pg.148]

According to low temperature C-NMR study on the affinity of MAD with oxygen containing functional groups, such as carbonyl compounds and ethers, coordination of amides to MAD is stronger than that of aldehydes, ester, and ketones, while coordination of ethers is rather weak [46). One of the most important synthetic utilities of MAD is that in the hydride reduction of two different ketones MAD can protect the less hindered ketone or more basic ketones by forming complexes with these ketones, that is, selective reduction of more hindered free ketones can realize. As shown in Scheme 6.38, for example, DIBAL reduction (1 equivalent) of a 1 1 mixture of acetophenone and tert-butylphenylketone provide two carbinols with low chemoselectivity. On the other hand, in the presence of... [Pg.262]

Aliphatic, benzyhc and allyhc alcohols were also rapidly oxidized without any overoxidation to carboxylic acids. Secondary carbinols were slowly oxidized. These reactions are highly chemoselective. The method was foimd to be highly selective... [Pg.35]


See other pages where Carbinols chemoselectivity is mentioned: [Pg.161]    [Pg.88]    [Pg.228]    [Pg.133]    [Pg.378]    [Pg.203]    [Pg.203]    [Pg.154]    [Pg.133]    [Pg.228]    [Pg.270]    [Pg.129]   
See also in sourсe #XX -- [ Pg.262 ]




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Chemoselective

Chemoselectivity

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