Two- and three-component reactions leading to new enamines derived from 2,3-dicyanobut-2-enoates

Abstract

The three-component reactions of 1-azabicyclo[1.1.0]butanes 1, dicyanofumarates (E)-5, and MeOH or morpholine yielded azetidine enamines 8 and 9 with the cis-orientation of the ester groups at the C=C bond ((E)-configuration; Schemes 3 and 4). The structures of 8a and 9d were confirmed by X-ray crystallography. The formation of the products is explained via the nucleophilic addition of 1 onto (E)-5, leading to a zwitterion of type 7 (Scheme 2), which is subsequently trapped by MeOH or morpholine (10a), followed by elimination of HCN. Similarly, two-component reactions between secondary amines 10a - 10c and (E)-5 gave products 12 with an (E)-enamine structure and (Z)-oriented ester groups. On the other hand, two-component reactions involving primary amines 10d - 10f or NH 3 led to the formation of the corresponding (Z)-enamines, in which the (E)-orientation of ester groups was established. © 2009 Verlag Helvetica Chimica Acta AG.