Ruthenium-Catalyzed Oxidative Annulation by Cleavage of CH/NH Bonds
作者:Lutz Ackermann、Alexander V. Lygin、Nora Hofmann
DOI:10.1002/anie.201101943
日期:2011.7.4
Bond activation in action: Unprecedented ruthenium‐catalyzed oxidative annulations of alkynes through cleavage of CH bonds set the stage for an efficient 1(2H)‐isoquinolone synthesis with ample scope (see scheme; tAm=tert‐amyl). Mechanisticstudies provided strong evidence for a rate‐limiting CH bond metalation through carboxylate assistance.
Rhodium-Catalyzed Oxidative Cycloaddition of Benzamides and Alkynes via C−H/N−H Activation
作者:Todd K. Hyster、Tomislav Rovis
DOI:10.1021/ja103776u
日期:2010.8.4
The oxidative cycloaddition of benzamides and alkynes has been developed. The reaction utilizes Rh(III) catalysts in the presence of Cu(II) oxidants, and is proposed to proceed by N-H metalation of the amide followed by ortho C-H activation. The resultant rhodacycle undergoes alkyne insertion to form isoquinolones in good yield. The reaction is tolerant of extensive substitution on the amide, alkyne, and arene, including halides, silyl ethers, and unprotected aldehydes as substituents. Unsymmetrical alkynes proceed with excellent regioselectivity, and heteroaryl carboxamides are tolerated leading to intriguing scaffolds for medicinal chemistry. A series of competition experiments shed further light on the mechanism of the transformation and reasons for selectivity.