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Issue 2, 2014
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Tandem diastereo- and enantioselective preparation of aryl and alkyl cyclopropyl carbinols with three adjacent stereocenters using perhydrobenzoxazines and diethylzinc

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Abstract

The enantio- and diastereoselective one-pot ethylation/cyclopropanation is efficiently promoted by a chiral perhydrobenzoxazine. The catalytic system tolerates a wide range of di- and trisubstituted α,β-unsaturated aldehydes and has been found to be highly diastereo- and enantioselective. Enals leading to intermediates lacking allylic strain or with either A1,2 or A1,3 strain afford the corresponding syn hydroxycyclopropanes very selectively. While α-methyl enals are successfully ethylated/cyclopropanated, the presence of bulky substituents at the alpha position of the enal constitutes a limitation to the substrate scope. The use of 1,1-diiodoethane allows the obtention of the corresponding enantioenriched cyclopropylcarbinol, which bears carbon-substituents at all three positions of the ring, with good enantiocontrol, although moderate diastereoselectivity. A procedure for the asymmetric one-pot arylation/cyclopropanation of enals is proposed, which involves the use of triarylboroxin, diethylzinc and diiodomethane.

Graphical abstract: Tandem diastereo- and enantioselective preparation of aryl and alkyl cyclopropyl carbinols with three adjacent stereocenters using perhydrobenzoxazines and diethylzinc

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Publication details

The article was received on 03 Sep 2013, accepted on 04 Nov 2013 and first published on 04 Nov 2013


Article type: Paper
DOI: 10.1039/C3OB41797B
Citation: Org. Biomol. Chem., 2014,12, 345-354
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    Tandem diastereo- and enantioselective preparation of aryl and alkyl cyclopropyl carbinols with three adjacent stereocenters using perhydrobenzoxazines and diethylzinc

    R. Infante, J. Nieto and C. Andrés, Org. Biomol. Chem., 2014, 12, 345
    DOI: 10.1039/C3OB41797B

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