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. 2009 Aug 22;65(34):6834-6839.
doi: 10.1016/j.tet.2009.06.083.

Synthesis of 2,6-disubstituted dihydropyrans via an efficient BiBr(3)-initiated three component, one-pot cascade

Robert J Hinkle  1 , Yajing Lian, Lee C Speight, Heather E Stevenson, Melissa M Sprachman, Lauren A Katkish, M Christa Mattern
Affiliations

Synthesis of 2,6-disubstituted dihydropyrans via an efficient BiBr(3)-initiated three component, one-pot cascade

Robert J Hinkle et al. Tetrahedron. .

Abstract

The rapid synthesis of cis-2,6-disubstituted dihydropyrans is achieved in a three-component, one-pot cascade reaction. BiBr(3)-ediated addition of ketene silyl acetals or silyl enol ethers to beta,gamma-unsaturated cis-4-trimethylsilyl-3-butenal provides a Mukaiyama aldol adduct containing a vinylsilane moiety tethered to a silyl ether. Addition of a second aldehyde initiates a domino sequence involving intermolecular addition followed by an intramolecular silyl-modified Sakurai (ISMS) reaction. Isolated yields of this one-pot reaction vary from 44 to 80% and all compounds were isolated as the cis-diastereomers (10 examples).

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Figures

Figure 1
Figure 1
Observed qualitative NOE enhancement.
Scheme 1
Scheme 1
Retrosynthetic analysis of 2,6-disubstituted DHPs
Scheme 2
Scheme 2
Reaction Sequence for the Three-Component, One-Pot Synthesis of Dihydropyrans.
See this image and copyright information in PMC

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    1. The LD50 of BiCl3 is listed as 3334 mg/kg (oral, rat) and 2250 mg/kg (oral, mouse) in the MSDS provided by Sigma-Aldrich Chemical Corp., St. Louis, MO.

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