Two‐ and Three‐Component Reactions Leading to New Enamines Derived from 2,3‐Dicyanobut‐2‐enoates

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 CC 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.