First Direct N-Cyclopropylation of Nitrogen-Containing Heterocycles

Significance

In this article the first general method for direct N-cyclopropylation of nitrogen-containing heterocycles is presented. Thus, N-cyclopropylated heterocycles which formerly could only be obtained by tedious multi-step procedures are now readily accessible by the simple use of tri­cyclopropylbismuth and copper acetate. The fact that tricyclopropylbismuth unlike other alkyl bismuth reagents is found to be non-pyrophoric makes the experimental handling of the reaction very convenient. With this extension of Barton’s method for the N-arylation of nitrogen-containing compounds at hand, N-cyclopropylated cyclic amides, carbamates and azoles even bearing sensitive functionalities, such as aldehyde and nitro groups, can be obtained in good to excellent yields.