Phosphine ligands stabilized Cu(I) catalysts for carbene insertion into the N–H bond

• Have been used phosphine stabilized Cu(I) complexes for carbene reactions.
• Carbene inserted into the N–H bond of anilines under mild experimental conditions.
• Wide scope of diazo and aniline derivatives.
• Studied electronic effects on yields of carbene inserted products.
• Wide range α-aryl amino esters were synthesized and characterized.

Phosphine ligands have been successfully used along with Cu(I) for several catalytic reactions, nevertheless these ligands were less explored relatively for carbene involved reactions owing to the formation of carbene-phosphine ylides. In this report we successfully used three different phosphine stabilized Cu(I) complexes (1–3) as catalysts for chemoselective carbene insertion into the N–H bond of different aromatic amines over the formation of olefin (carbene dimerized product). In order to understand the substrate scope, different α-diazo esters have been reacted with large number of amines and all the reactions produced reasonably good yields under normal experimental conditions (38 examples). All the carbene inserted products have been isolated by column chromatography and fully characterized using standard spectroscopic techniques without any ambiguities. Several control reactions have been conducted in order to understand the importance of the type of phosphine ligands used in the catalysts 1–3 and found that without these catalysts we observed less selectivity (more of olefin as the product over N–H inserted product) and low yield. From this present study, it can be noted that the rigid framework phosphine ligands would be the better choice for carbene chemistry. The results obtained from the current studies would inspire chemists to develop more novel Cu(I)-phosphine catalysts for carbene related reactions including asymmetric versions in the near future.

Cu(I)-phosphine complexes as catalysts for carbene insertion into the N–H bond of different anilines.Figure optionsDownload as PowerPoint slide