| Anilines are important building blocks in organic chemistry,pharmaceuticals,and materials science.Para-alkyl aniline is an important aniline derivative.In contrast to protected amino groups of aniline,tertiary anilines and N-pyrimidyl anilines,the amino group of unprotected anilines would readily undergo classic and transition-metal-catalyzed nucleophilic substitution,leading N-alkyl byproducts.Furthermore,the less sterically hindered amino group normally leads to the production of both ortho-and para-isomers.Thus,unprotected anilines have always been challenging substrates.These challenges led to the multiple-step routine for para-alkyl anilines through the synthesis and reduction of substituted nitrobenzene.However,the additional steps reduce the step-economy,and the harsh conditions limit both the functional group tolerance and the possibility for late-stage functionalization.Therefore,it is urgent to develop an efficient and mild para-selective alkylation reaction of aniline without protection at the nitrogen position.Based on the results of our investigation along these lines,we report herein the visible-light-mediated Ru(Ⅱ)catalyzed para-alkylation of anilines and the para-acylation of N,N-diethylaniline.The distinct Ru(Ⅱ)-aniline complex enabled the reaction to proceed with extremely high efficiency(2 hours)under mild conditions.Furthermore,the good functional group tolerance of the process allowed for late-stage functionalization and even AIEgen labelling of natural products and drugs.Mechanistic investigation reveals that the Ru(Ⅱ)-aniline complex both triggers the visible-light-mediated reduction of alkyl halides and directs the para-selectivity through the steric bulk of the p-cymene ligand. |
