Introverted Brønsted acid cavitands for selective conjugate addition reactions

ABSTRACT

Four new quinoxaline-spanned cavitands having a diester hydrogen phosphate group were successfully synthesised. These phosphorous derivatives were applied in Brønsted acid-assisted catalytic conjugate addition reactions. The results were ranked with the control of diphenyl hydrogen phosphate as well as among those four cavitands. The structure–activity relationship revealed that the catalyst centre surrounded by two trans-positioned quinoxalines significantly influences reaction profile and product distribution. This comparative study provides us an intellectual basis for future catalytic cavitand chemistry and artificial enzymatic catalysis.

KEYWORDS:

• Brønsted acids
• introverted functionality
• supramolecular catalysis
• cavitands
• artificial enzymes

Acknowledgments

JSPS Grant-in-Aid for Scientific Research (C), Grant Number 19K05426, which supported T.I. in this work, is gratefully acknowledged for funding. This work was supported by 2020 the Joint Research Center for Science and Technology of Ryukoku University. The authors thank Dr Toshiyuki Iwai and Dr Takatoshi Ito and Dr Seiji Watase at ORIST for gentle assistance with HRMS and crystallographic analysis. Prof. Dr Schramm, M. P. at CSULB are gratefully thanked for helpful discussions. Dedicated to Professor François Diederich who sadly passed away on the 23^rd of September 2020

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the JSPS [19K05426].