Enantioselective aza-Friedel-Crafts reaction of furan with α-ketimino esters induced by a conjugated double hydrogen bond network of chiral bis(phosphoric acid) catalysts

Manabu Hatano; Haruka Okamoto; Taro Kawakami; Kohei Toh; Hidefumi Nakatsuji; Akira Sakakura; Kazuaki Ishihara

doi:10.1039/c8sc02290a

Enantioselective aza-Friedel-Crafts reaction of furan with α-ketimino esters induced by a conjugated double hydrogen bond network of chiral bis(phosphoric acid) catalysts

Chem Sci. 2018 Jun 25;9(30):6361-6367. doi: 10.1039/c8sc02290a. eCollection 2018 Aug 14.

Authors

Manabu Hatano¹, Haruka Okamoto¹, Taro Kawakami¹, Kohei Toh¹, Hidefumi Nakatsuji¹, Akira Sakakura², Kazuaki Ishihara¹

Affiliations

¹ Graduate School of Engineering , Nagoya University , Furo-cho, Chikusa , Nagoya 464-8603 , Japan . Email: ishihara@cc.nagoya-u.ac.jp ; ; Tel: +81-52-789-3331.
² Graduate School of Natural Science and Technology , Okayama University , 3-1-1 Tsushimanaka, Kita-ku , Okayama 700-8530 , Japan . Email: sakakura@okayama-u.ac.jp ; ; Tel: +81-86-251-8215.

Abstract

Chiral C ₂- and C ₁-symmetric BINOL-derived bis(phosphoric acid) catalysts, which have OP([double bond, length as m-dash]O)(OH)₂/OP([double bond, length as m-dash]O)(OH)(OR) moieties at the 2,2'-positions, were developed and used for the enantioselective aza-Friedel-Crafts reaction of 2-methoxyfuran with α-ketimino esters for the first time. The intramolecular conjugated double hydrogen bond network is a key to increasing the Brønsted acidity and preventing deactivation of the catalysts. Highly functionalized α-amino acid derivatives with a chiral quaternary carbon center could be transformed into versatile optically active N- and O-heterocycles and an α-aryl-substituted serine.