Laccase-Catalyzed Domino Reactions between Hydroquinones and Cyclic 1,3-Dicarbonyls for the Regioselective Synthesis of Substituted p-Benzoquinones

Publication Type

Journal contribution (peer reviewed)

Authors

Hajdok, S.; Conrad, J.; Beifuss, U.

Year of publication

2012

Published in

J. Org. Chem.

Band/Volume

77/1

DOI

10.1021/jo202082v

Page (from - to)

445 - 459

Highly substituted p-benzoquinones were obtained in yields ranging from 39% to 98% by laccase-catalyzed domino reactions between hydroquinones and cyclic 1,3-dicarbonyls using aerial oxygen as the oxidant.  In almost all reactions bis-adducts with two adjacent 1,3-dicarbonyl substituents on the quinone moiety were formed selectively. The transformations can be regarded as domino oxidation/1,4-addition/oxidation/1,4-addition/oxidation processes. With unsubstituted hydroquinone as the substrate 2,3-disubstituted p-benzoquinones were isolated. Bis-adducts were also formed exclusively upon reaction with monosubstituted hydroquinones. In almost all cases the 2,3,5-trisubstituted p-benzoquinones were obtained. When 2,3-disubstituted hydroquinones were employed as starting materials the 2,3,5,6-tetrasubstituted p-benzoquinones were isolated. The unambiguous structure elucidation of all products has been achieved by NMR spectroscopic methods including spin pattern anal. of the long-range coupled C=O carbons and ¹³C satellites anal. in ¹H NMR spectra.