Intermolecular and Intramolecular Reactions of Resolved 2-Alkoxytetrahydrofuran-3-yl and 2-Alkoxytetrahydropyran-3-yl Radicals

✍ Scribed by Kalpana S Nimkar; Eugene A Mash

• Book ID: 104202860
• Publisher: Elsevier Science
• Year: 2000
• Tongue: French
• Weight: 142 KB
• Volume: 56
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(00)00547-0

✦ Synopsis

AbstractÐDiastereomeric trans-2-alkoxy-3-phenylselenenyltetrahydrofuranyl acetals and trans-2-alkoxy-3-phenyl-selenenyltetrahydropyranyl acetals were prepared from dihydrofuran, dihydropyran, phenylselenenyl bromide, and the alcohols (S)-methyl lactate, (S)-methyl hexahydromandelate, and (R)-pantolactone. The diastereomers were chromatographically separated and were subjected to intermolecular alkylation via generation and trapping of free radicals. Observed diastereoselectivity was higher for 2-alkoxytetrahydrofuran-3-yl radicals than for 2-alkoxytetrahydropyran-3-yl radicals, and highest for acetals involving (R)-pantolactone. Alcohol exchanges at the anomeric carbon were highly stereocontrolled, and permitted introduction of alkenes for intramolecular trapping of free radical intermediates.