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Squaramide‐Catalyzed Asymmetric aza‐Friedel–Crafts/N,O‐Acetalization Domino Reactions Between 2‐Naphthols and Pyrazolinone Ketimines
Author(s) -
Kaya Uğur,
Chauhan Pankaj,
Mahajan Suruchi,
Deckers Kristina,
Valkonen Arto,
Rissanen Kari,
Enders Dieter
Publication year - 2017
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201709224
Subject(s) - squaramide , stereocenter , friedel–crafts reaction , bifunctional , chemistry , catalysis , reactivity (psychology) , domino , medicinal chemistry , yield (engineering) , stereoselectivity , adduct , organic chemistry , organocatalysis , phenols , enantioselective synthesis , materials science , medicine , alternative medicine , pathology , metallurgy
N‐Boc ketimines derived from pyrazolin‐5‐ones were explored to develop an unprecedented domino aza‐Friedel–Crafts/N,O‐acetalization reaction with 2‐naphthols. The novel method requires a catalyst loading of only 0.5 mol % of a bifunctional squaramide catalyst, is scalable to gram amounts, and provides a new series of furanonaphthopyrazolidinone derivatives bearing two vicinal tetra‐substituted stereogenic centers in excellent yields (95–98 %) and stereoselectivity (>99:1 d.r. and 97–98 % ee ). A different reactivity was observed in the case of 1‐naphthols and other electron‐rich phenols, which led to the aza‐Friedel–Crafts adducts in 70–98 % yield and 47–98 % ee .