A versatile catalyst system for enantioselective synthesis of 2-substituted 1,4-benzodioxanes?

Chemical Science Pub Date: 2019-03-13 DOI: 10.1039/C8SC05612A

Abstract

We report the synthesis of enantiomerically enriched 1,4-benzodioxanes containing alkyl, aryl, heteroaryl, and/or carbonyl substituents at the 2-position. The starting 1,4-benzodioxines were readily synthesized via ring closing metathesis using an efficient nitro-Grela catalyst at ppm levels. Excellent enantioselectivities of up to 99:1 er were obtained by using the versatile catalyst system [Ir(cod)Cl]2/BIDIME-dimer in the asymmetric hydrogenation of 2-substituted 1,4-benzodioxines. Furthermore, DFT calculations reveal that the selectivity of the process is controlled by the protonation step; and coordinating groups on the substrate may alter the interaction with the catalyst, resulting in a change in the facial selectivity.

Graphical abstract: A versatile catalyst system for enantioselective synthesis of 2-substituted 1,4-benzodioxanes
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