Hydroamination of 1,1-dimethylallene with primary aryl amines under mild conditions: An atom-economical route to N-(1,1-dimethyl-2-propenyl)-anilines

Abstract

The synthesis of alicyclic 3-iminophosphine ligands was extended to include a new framework incorporating a cyclopentenyl backbone with a di-tert-butyl phosphine functionality (3IP^tBu). The palladium complex [(3IP^tBu)Pd(allyl)]OTf displayed excellent catalytic activity in the 100% atom-efficient hydroamination of 3-methyl-1,2-butadiene (1,1-dimethylallene) with primary aryl amines (anilines), selectively producing the branched allylic amine products (kinetic products) in high conversion at ambient temperature for non-halogenated substrates. Hydroamination using halogenated anilines was successful at 70 °C, providing moderate yields, with the formation of little or no linear product (thermodynamic product). Additionally, a subsequent aromatic amino Claisen rearrangement of selected allylic amine products, employing catalytic triflic acid, proved to be an effective atom-economical method for the production of ortho-allylic anilines in a high yielding two-step, one-pot synthesis.