Ketones reactions with chloromethyleneiminium salts

The reaction of ketone derivatives (89) with chloromethyleneiminium salt (1) gives iminium salts (90) which yield, after hydrolysis, P-chloroacrolein derivatives (91 Scheme 7)." Numerous P-chloroacrolein derivatives have been prepared by this method and yields are generally moderate to good. p-Chloroacryl-onitrile derivatives (92) are also available in good yield from iminium salts (90 = H) by treatment... 

Conductivity measurements have revealed that DMF and carboxylic acid chlorides form salt-like adducts (22) in an equilibrium reaction (equation 12). Such adducts can be prepared either from DMF and acid halides (chlorides and bromides) or from chloromethyleneiminium salts and salts of carboxylic acids. Acyloxyiminium salts (23) can be prepared in the pure state by reacting acid amides with carboxylic acid chlorides in the presence of silver trifluoromethanesulfonate (equation 13). Salts of type (24 equation 14) are regarded as being intermediates in the synthesis of ketones from carboxylic acids and Grignard reagents in the presence of a-chloroenamines as well as in the preparation of acyl halides (F, Cl, Br, I) by action of a-haloenamines on carboxylic acids. ... 

Vilsmeier acylation of pyrroles, formylation with dimethylformamide/phosphoryl chloride in particnlar, is a generally applicable process. The actual electrophilic species is an Al,Al-diaIkyl-chloromethyleneiminium cation (the chloride is available commercially as a solid). " Here again, the presence of a large pyrrole-A-substituent perturbs the intrinsic a-selectivity, formylation of A-tritylpyrrole favonring the P-position by 2.8 1 and trifluoroacetylation of this pyrrole giving only the 3-ketone " the nse of bulky iV-silyl substituents allows P-acylation with the possibility of subsequent removal of the N-snbstituent." The final intermediate in a Vilsmeier reaction is an iminium salt requiring hydrolysis to prodnce the isolated product aldehyde. When a secondary lactam is used, hydrolysis does not take place and a cyclic imine is obtained." ... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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