Tunable Arylative Cyclization of 1,6-Enynes Triggered by Rhodium(III)-Catalyzed C–H Activation
摘要:
Two tunable arylative cyclizations of cyclohexadienone-containing 1,6-enynes are reported via rhodium(III)-catalyzed C-H activation of O-substituted N-hydroxybenzamides. The use of different O substituents, i.e. O-Piv and O-Me, on the directing group allows the formation of either tetracyclic isoquinolones through an (c)-Michael addition process or hydrobenzofurans through a (N)Michael addition process. Mechanistic investigations of these two cascade reactions clearly indicated that the C-H bond cleavage process was involved in the turnover-limiting step. Furthermore, the cyclization products could be subjected to various transformations for elaborating the pharmaceutically and synthetically valuable potential. This is the first example of a rhodium(III)-catalyzed arylative cyclization reaction of 1,6-enynes, and the results extend the application realm of Cp*Rh-III-catalyzed C-H activation cascade reactions.
Enantioselective Kinetic Resolution/Desymmetrization of
<i>Para</i>
‐Quinols: A Case Study in Boronic‐Acid‐Directed Phosphoric Acid Catalysis
作者:Banruo Huang、Ying He、Mark D. Levin、Jaime A. S. Coelho、Robert G. Bergman、F. Dean Toste
DOI:10.1002/adsc.201900816
日期:2020.1.23
A chiral phosphoric acid‐catalyzed kineticresolution and desymmetrization of para‐quinols operating via oxa‐Michael addition was developed and subsequently subjected to mechanistic study. Good to excellent s‐factors/enantioselectivities were obtained over a broad range of substrates. Kinetic studies were performed, and DFT studies favor a hydrogen bonding activation mode. The mechanistic studies provide