Amide acetals azavinylogs

An important synthesis for formamide acetals with bulky alkoxy groups or with -aryl substituents starts from the corresponding formamidinium salts or from bis(didkylamino)acetonitriles the reaction with alcoholic alkoxides furnishes the amide acetals (449 Scheme 83).7 -32.35 ju tjjg reaction of the azavinylogous formamidinium salt (450) with methanolic methoxide a mixture of -dimethylform-amide dimethyl acetal and its azavinylogous derivative is produced. 

Transamination of amide acetals is possible and of synthetic value if high boiling, strongly nucleophilic secondary amines are to be introduced. Ketene 0,iV-acetals add alcohols to yield amide acetals (468 equation 216). From tetrakis(dimethylamino)ethylene and methanol a mixture of amide acetals, e.g. (469) and (470 equation 217), is formed. Azavinylogous formamide acetals (471 equation 218) are accessible by the action of formide acetals on tris(formylamino)methane or form-amide. ... 

Amide acetals on treatment with hydrocyanic acid, acyl cyanides - or trimethylsilyl cyanide yield 2-aIkoxy-2-dialkyIaminocarbonitriles (482 Scheme 88). A similar cleavage has bem performed with azavinylogous amide acetals (483). ... 

In addition to the construction of the amidine structure iV-alkylation reactions can occur,ring opening in the case of heterocyclic amines and formylation of acidic methylene or methyl groups. 76i,793 jjjg reaction of formamide with excess /V,N-dialkylformamide acetals deviates from this reaction pattern, here azavinylogous formamide acetals (358 Scheme 62) are formed. A, A -Dialkyl-iV -formylformamidines (359) can be prepared either by action of A, N-dialkylformamide acetals on bis(trimethylsilyl)formamide or by treatment of azavinylogous amide acetds (358) with trimethyl-chlorosilane. ... 

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