The rapid synthesis of cis-2,6-disubstituted dihydropyrans is achieved in a three-component, one-pot cascade reaction. BiBr3-mediated 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). (C) 2009 Elsevier Ltd. All rights reserved.
Hinkle, R. J., Lian, Y., Speight, L. C., Stevenson, H. E., Sprachman, M. M., Katkish, L. A., & Mattern, M. C. (2009). Synthesis of 2, 6-disubstituted dihydropyrans via an efficient BiBr3-initiated three component, one-pot cascade. Tetrahedron, 65(34), 6834-6839.