Synthesis 2014; 46(13): 1815-1822
DOI: 10.1055/s-0033-1341086
paper
© Georg Thieme Verlag Stuttgart · New York

Regioselectivity in the Ring Opening of Epoxides: A Metal-Free Cascade C–S/C–O Bond Formation Approach to 1,3-Oxathiolan-2-ylidenes through Heteroannulation of α-Enolic Dithioesters at Room Temperature

Gaurav Shukla
a   Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi-221005, India   Fax: +91(542)2368127   eMail: mssinghbhu@yahoo.co.in
,
Anugula Nagaraju
a   Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi-221005, India   Fax: +91(542)2368127   eMail: mssinghbhu@yahoo.co.in
,
Abhijeet Srivastava
a   Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi-221005, India   Fax: +91(542)2368127   eMail: mssinghbhu@yahoo.co.in
,
Girijesh Kumar Verma
a   Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi-221005, India   Fax: +91(542)2368127   eMail: mssinghbhu@yahoo.co.in
,
Keshav Raghuvanshi
b   Institute für Organische und Biomolekulare Chemie, Georg-August-Universität, Tammannstrasse 2, 37077 Göttingen, Germany
,
Maya Shankar Singh*
a   Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi-221005, India   Fax: +91(542)2368127   eMail: mssinghbhu@yahoo.co.in
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Publikationsverlauf

Received: 23. Januar 2014

Accepted after revision: 10. März 2014

Publikationsdatum:
17. April 2014 (online)


Abstract

An operationally simple and efficient approach to hitherto unreported and synthetically demanding 1,3-oxathiolan-2-ylidenes has been developed. The approach involves a cascade [2+3] heteroannulation of α-enolic dithioesters with epoxides promoted by non-nucleophilic moderate base Cs2CO3 at room temperature. Typical features of this strategy include metal-free mild reaction conditions, atom-economy, high yields, and efficacy of forming two consecutive C–S and C–O bonds, and one ring in a single stroke. MeSH is the only by-product, and the stereochemistry of the exocyclic α-oxoketene moiety of 1,3-oxathiolane was assigned to have Z-configuration.

Supporting Information