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Brønsted Acid Catalyzed, Conjugate Addition of β‐Dicarbonyls to In Situ Generated ortho ‐Quinone Methides—Enantioselective Synthesis of 4‐Aryl‐4 H ‐Chromenes
Author(s) -
ElSepelgy Osama,
Haseloff Stefan,
Alamsetti Santosh Kumar,
Schneider Christoph
Publication year - 2014
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.201403573
Subject(s) - enantioselective synthesis , brønsted–lowry acid–base theory , catalysis , phosphoric acid , quinone , chemistry , aryl , conjugate , in situ , organic chemistry , combinatorial chemistry , mathematical analysis , alkyl , mathematics
Abstract We describe herein a catalytic, enantioselective process for the synthesis of 4 H ‐chromenes which are important structural elements of many natural products and biologically active compounds. A sequence comprising a conjugate addition of β‐diketones to in situ generated ortho ‐quinone methides followed by a cyclodehydration reaction furnished 4‐aryl‐4 H ‐chromenes in generally excellent yields and high optical purity. A BINOL‐based chiral phosphoric acid was employed as a Brønsted acid catalyst which converted ortho ‐hydroxy benzhydryl alcohols into hydrogen‐bonded ortho ‐quinone methides and effected the carbon–carbon bond‐forming event with high enantioselectivity.