ChemInform Abstract: A Reiterative Synthesis of trans-Fused Polypyrans via Tungsten Pentacarbonyl-Promoted Alkynol Endocyclization.
✍ Scribed by J. L. BOWMAN; F. E. MCDONALD
- Publisher
- John Wiley and Sons
- Year
- 2010
- Weight
- 35 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0931-7597
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✦ Synopsis
A Reiterative Synthesis of trans-Fused Polypyrans via Tungsten Pentacarbonyl-Promoted Alkynol Endocyclization.
-Endocyclization of 1-alkyn-5-ols such as (III) occurs in the presence of tungsten pentacarbonyl-THF complex to give cyclic six-membered tungsten oxacarbenes. They are easily converted to α-stannyl enol ethers by treatment with Bu 3 SnOTf and Et 3 N. These stannylated dihydropyrans undergo organocuprate-mediated alkylation to provide 6-(2-propynyl)-3,4-dihydro-2H-pyrans. Oxidation with MCPBA followed by reduction with Et 3 SiH generates another trans-fused 1-alkyn-5-ol (VI). Repetition of this process provides a reiterative synthesis of trans-fused polypyrans as building blocks for brevetoxins. -(BOWMAN, J.