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Synlett 2011(7): 995-999  
DOI: 10.1055/s-0030-1259715
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Halogenation Reagents Initiating Ring Opening of Vinylidenecyclopropanes: Easy Access to Halogenated Tetrahydropyrans

Wei Yuan, Min Shi*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, P. R. of China
Fax: +86(21)64166128; e-Mail: mshi@mail.sioc.ac.cn;
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Publication History

Received 31 August 2010
Publication Date:
10 March 2011 (online)

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Abstract

A novel synthetic protocol that uses halogenation reagents (NBS, NIS and selectfluor) to initiate intramolecular ring-opening reactions of diarylvinylidenecyclopropanes (VDCPs) connected to alcohol-bearing chains has been developed. The approach provides a variety of halogenated tetrahydropyran derivatives in moderate to good yields under mild conditions. Plausible reaction mechanisms are proposed on the basis of previous literature and the substrate scope has been carefully examined.

Key words

vinylidenecyclopropanes - halogenation - hydroxyl group - ring opening - tetrahydropyrans

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The structure of 4a was determined on the basis of the C-H COSY, DEPT, and HMBC spectra.

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G eneral procedure for the intramolecular ring-opening reaction of diarylvinylidenecyclopropanes 2 with NBS. VDCP 2 (0.2 mmol), NBS (1.2 equiv), and NaHCO3 (1.0 equiv) were added into a tube under argon, then MeCN (2.0 mL, 0.1 M of 2 in MeCN) was added into the tube via syringe. The mixture was stirred for 3 h at r.t., then the solvent was removed in vacuo and the residue was purified by flash column chromatography on silica gel column (petroleum ether-EtOAc, 20:1) to give 4 in moderate to good yields.