Aza-enamines XI. Vinylogous Aza-enamines as Neutral d(3)-Nucleophiles: Aminomethylations of N,N-Dimethylhydrazones of alpha,beta-Unsaturated Aldehydes

作者：Grabowski Matthias T; Nowosinski Karol; Lentz Dieter; Brehme Rainer^*; Schalley Christoph A

来源：Synthesis, 2010, (20): 3556-3568.

DOI：10.1055/s-0030-1258194

• hydrazones
• electrophilic substitution
• nucleophilic addition
• amino aldehydes
• umpolung

N,N-Dimethylhydrazones of propenal- and 2-methylpropenal and their derivatives and homologues (vinylogous azaenamines) were allowed to react with N, N-dimethylformiminium chloride in moisture-free dimethylformamide to yield singly, doubly, and even triply aminomethylated products. They can be easily separated and characterized as crystalline hydrochlorides. The reaction takes place at the omega-position of the pi-system. This is a consequence of the conjugative interaction of the electron-donating aminohydrazone group with the double bond system in analogy to the enamines. The formation of dialkylhydrazones from unsaturated aldehydes thus causes the umpolung of the formerly electrophilic d(3)-building blocks into a nucleophile. Depending on the reaction conditions and confirmed by crystal structures and 2D NMR experiments, control can be exerted over the degree of substitution: Up to trisubstituted products were obtained for the 2-methylpropenal derivative. The hydrochlorides can be easily deprotonated to yield the free aminohydrazone bases. The back-conversion of the aminohydrazones into the corresponding amino aldehydes is possible under acidic conditions.

• 出版日期2010-10