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Bases, ambident secondary

The addition of alcohols to nitrilium salts gives rise to formation of alkoxymethyleneiminium salts, which react with bases to yield imido esters (231 Scheme 33). - By deprotonation of carboxylic acid amides ambident anions are formed, which can be alkylated in the presence of silver ions to give imido esters, e.g. (232). " Secondary amides react with trifluoroacetic acid anhydride or trifluorosulfonic acid anhydride to give mixed anhydrides of imidic acids (233). ... [Pg.529]

Ambident Nucleophiles. Amides and related functional groups can be alkylated on oxygen or nitrogen and, as has been noted already, alkylation on carbonyl oxygen normally predominates. In the case of carbamates, 0-alkylation by Me0S02F can be faster, but W-alkylation predominates at equilibrium. It has been noted that methylation of secondary amides and thioamides occurs at the protonless heteroatom in the major tautomer. The ionic products of these reactions can be deprotonated to give synthetically useful products, e.g. imidates, but excess Me0S02F should be removed before treatment with base. ... [Pg.402]


See other pages where Bases, ambident secondary is mentioned: [Pg.59]    [Pg.618]    [Pg.320]    [Pg.59]    [Pg.618]    [Pg.59]    [Pg.420]    [Pg.618]    [Pg.322]    [Pg.322]    [Pg.253]    [Pg.322]   
See also in sourсe #XX -- [ Pg.239 ]




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