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5-Bromo-2-pyrone: An easily prepared ambiphilic diene and a synthetic equivalent of 2-pyrone in mild, thermal, Diels-Alder cycloadditions

✍ Scribed by Kamyar Afarinkia; Gary H. Posner

Publisher: Elsevier Science
Year: 1992
Tongue: French
Weight: 267 KB
Volume: 33
Category: Article
ISSN: 0040-4039
DOI: 10.1016/s0040-4039(00)74757-5

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✦ Synopsis

Bmmo-2-pyrone, a solid prepared easily in one-flask according to a new route (eq. 1). has been found to undergo smooth and highly regiocontrolled 2+4cycloadditlons between 251OtYC with both electron-poor and electron-rich dienophiles; subsequent radical debrominations produced halogen-free bicyclic lactones, including a precursor to a vitamin D steroid, thus showing 5-bromo-2-pyrone to be a practical and effective synthetic equivalent of 2-pymne in thermal Diels-Alder cycloaddition.

Recently we discovered that 3-bromo-2-pyrone, chameleon-like, undergoes smooth and regiospecific 2 +

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3-bromo-2-pyrone: an easily prepared chameleon diene and a synthetic equivalent of 2-pyrone in thermal diels-alder cycloadditions

✍ Gary H. Posner; Todd D. Nelson; Chris M. Kinter; Kamyar Afarinkia 📂 Article 📅 1991 🏛 Elsevier Science 🌐 French ⚖ 292 KB

3-Bromo-2-pyrone, a stable solid prepared by a new route (eq. l), has been found to undergo smooth and regiospecific 2+4-cycloadditions between 78-90°C with both electron-n& and electron-deficient dienophtles; subsequent high-yield reductive debrominattons produced halogen-free cycloadducts thus sho