Nitrone cycloaddition reactions to α,β-unsaturated carbonyl acceptors catalyzed by a pinhole Lewis acid catalyst. Dramatic rate acceleration and improvement of regioselectivity and diastereoselectivity

✍ Scribed by Shuji Kanemasa; Naohisa Ueno; Moto Shirahase

• Book ID: 104232287
• Publisher: Elsevier Science
• Year: 2002
• Tongue: French
• Weight: 97 KB
• Volume: 43
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)02246-8

✦ Synopsis

A catalytic amount of aluminum tris(2,6-diphenylphenoxide), designated as ATPH, catalyzes nitrone cycloaddition reactions between N-benzylideneaniline N-oxide and a,b-unsaturated carbonyl acceptors and induces a dramatic rate enhancement showing high to exclusive control of regioselectivity in favor of the formation of isoxazolidine-4-carboxaldehydes. Such high regioselectivities leading to electronically controlled cycloadducts provides a striking contrast to the selectivities generally observed for the uncatalyzed reactions in which regioselectivities result from a competition between steric and electronic factors. Thus, the use of a pinhole catalyst is effective for a selective activation of electrophiles in the catalyzed reactions using strongly coordinating bulky nucleophiles.