Diethyl acetal enaminones, reactions with

In an intramolecular reaction with jV,jV-diethylformamide or AyV-dimethylacetamide diethyl acetal, enaminones are known to react at the nitrogen to form amidines42. The corresponding products from acetamide acetals can be converted to 2-aminoquinolines by condensation with DMF acetals or to 1,4-dihydroquinolines by cycloaddition with diethyl maleate (see Section II.A.5) (equation 26). 

Acetophenone and ring-substituted acetophenones condense with dimethylformamide diethyl acetal to give the enaminones 151, which yield 5-arylisoxazoles (152) by reaction with hydroxylamine O-sulphonic acid (equation 66)87. 

Monoprotected P-keto-aldehydes may be prepared by the a-dialkoxymethyl-ation of pre-formed enolates or enamines with trimethyl orthoformate and boron trifluoride diethyl etherate. Regiospecificity is maintained when the enolate is released from the silyl enol ether with methyl-lithium. P-Keto-acetals or P-diketones may also be formed by acylation of enol ethers with acid chlorides. High yields depended on the use of activated acid chlorides, such as a-halo- or a-cyano-acetyl chlorides. Enaminosilanes are acylated by a wide range of acid chlorides in the presence of potassium fluoride and a crown ether, giving very high yields of the enaminone [equation (46)]. Under the reaction conditions,... 

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