Regioselectivity of the reactions of trialkylaluminum reagents with 2,3-epoxyalcohols: Application to the synthesis of α-chiral aldehydes

✍ Scribed by William R. Roush; Michael A. Adam; Steven M. Peseckis

• Book ID: 104217110
• Publisher: Elsevier Science
• Year: 1983
• Tongue: French
• Weight: 227 KB
• Volume: 24
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)81660-3

✦ Synopsis

Treatment of optically active 2,3-epoxyalcohols with trialkylaluminum reagents followed by periodate cleavage constitutes a convenient synthesis of a-chiral aldehyde derivatives, especially when the branching alkyl group is methyl. We recently required a convenient source of either 1,2-diol 2 or 1,3-diol 2 for use in a natural product synthesis. Indeed, treatment of (R,R)-epoxide 12 ([a];' + 21.4", c=1.40, CHC13, >95% ee) with Me2CuLi (1.2 equiv.) in Et20 at -20"C3 for 1 h afforded a mixture of 2 and 3 (ca. 1:6 by NMR analysis), whereas complimentary regioselectivity was realized when 1 was treated with Me3Al (3 equiv.) in CH2C12 (0' to 23°C over 10 h; ca. 5:l mixture of 2:z)y4 These mixtures were inseparable by conventional chromatographic techniques. Purification of 1,3-diol 3, however, was accomplished after treating these mixtures with NaI04 in aqueous THF, which transformed 1,2-diol2 to aldehyde 4. In this manner diol 35asb ([a];' + 16.5", c=1.18, CHC13) 'Aas obtained in 74-79% yield via the cuprate sequence.