Enantioselective cyclopropanation of conjugated cyanosulfones using carbohydrate-based crown ether catalysts

• Published in: Tetrahedron Vol. 76; no. 9; p. 130965
• Main Authors: Nemcsok, Tamás, Rapi, Zsolt, Bagi, Péter, Guan, Ying Hou, Orbán, István, Keglevich, György, Bakó, Péter
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 28-02-2020
• Subjects: Chiral crown ethers; Enantioselective cyclopropanation; Phase transfer catalysis; Phase transfer catalysis; Chiral crown ethers; Enantioselective cyclopropanation
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2020.130965

A few new d-galactose- and d-glucose-based monoaza-15-crown-5 type lariat ethers have been synthesized. These macrocycles and their derivatives proved to be efficient catalysts in the cyclopropanation of (E)-3-phenyl-2-(phenylsulfonyl)acrylonitrile performed with diethyl bromomalonate under mild phase transfer conditions. Among the catalysts tested, the macrocycle having methyl α-d-galactopyranoside unit generated the highest asymmetric induction (80% ee). In the reactions of the aryl-substituted phenylsulfonyl-acrylonitrile derivatives, the cyclopropanation of the meta- and para-substituted starting materials took place with high ee values (75–84% ee). The cyclopropane derivatives synthesized from analogous α,β-unsaturated cyanosulfones containing naphthyl, pyridyl, furyl and thienyl groups were obtained with enantioselectivities up to 85%, and in excellent yields.
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•New d-glucose- and d-galactose-based crown ethers have been synthesized.•A new catalyst induced enantioselectivity up to 85% in the MIRC reaction of α,β-unsaturated cyanosulfones.•The m- and p-substituted products were formed with 75–84% ee, while the o-substituted cyclopropanes with 0–12% ee.•The new chiral cyclopropanes may be important intermediates in asymmetric syntheses.