Lewis acid-promoted selective rearrangement of trisubstituted epoxides to aldehydes or ketones

✍ Scribed by Keiji Maruoka; Noriaki Murase; Ronan Bureau; Takashi Ooi; Hisashi Yamamoto

• Publisher: Elsevier Science
• Year: 1994
• Tongue: French
• Weight: 613 KB
• Volume: 50
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(01)90389-8

✦ Synopsis

Rearrangement of trisubstituted epoxides has been effected under the influence of various Lewis acids. Among these, methylaluminum bis(4-bromo-2,6-di-t-butylphenoxide) (MABR) can be selectively rearranged from trisubstituted epoxides to aldehydes, while antimony pentafluoride is employable for selective rearrangement to ketones under mild conditions. The acid-catalyzed rearrangement of epoxides to carbonyl compounds is a well-known synthetic transformation and a number of reagents have been elaborated for this purpose.l-3 As illustrated in Scheme I, two types of rearrangement have, in principle, been conceivable for trisubstituted epoxide 1 depending on the two possible migration patterns following Lewis acid-promoted C-O bond cleavage. The rearrangement of 1 with hydrogen or alkyl (R3) shift gives ketone 2 or aldehyde 3, respectively. However, despite the Scheme I R' 0 /b-MLn Fe