Issue 34, 2017

Dinuclear zinc complex catalyzed asymmetric methylation and alkynylation of aromatic aldehydes

Abstract

A general AzePhenol dinuclear zinc catalytic system has been successfully developed and introduced into the asymmetric addition of dimethylzinc and alkynylzinc to aromatic aldehydes. In this system, an azetidine derived chiral ligand has proven to be an effective enantioselective promoter. Under the optimal reaction conditions, a series of chiral 1-hydroxyethyl (up to 99% ee) and secondary propargylic alcohols (up to 96% ee) were generated with good yields and enantioselectivities. Additionally, this novel catalytic system showed good functional group compatibility. Remarkably, the substituent's electronic nature alone is not sufficient to allow for exclusive enantioselectivity, an additional substituent's location also had an effect. We proposed that the formation of a stable and structural rigid transition state by the chelation of ortho substituted benzaldehydes to the zinc atom was responsible for the observed higher enantioselectivity. The possible catalytic cycles of both transformations accounting for the stereoselectivity were described accordingly.

Graphical abstract: Dinuclear zinc complex catalyzed asymmetric methylation and alkynylation of aromatic aldehydes

Supplementary files

Article information

Article type
Paper
Submitted
12 Jul 2017
Accepted
07 Aug 2017
First published
07 Aug 2017

Org. Biomol. Chem., 2017,15, 7147-7156

Dinuclear zinc complex catalyzed asymmetric methylation and alkynylation of aromatic aldehydes

S. Liu, G. Li, X. Yang, D. Zhang and M. Wang, Org. Biomol. Chem., 2017, 15, 7147 DOI: 10.1039/C7OB01717K

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