Inter- and intramolecular hetero diels-alder reactions, 41. Unusual stereocontrol in intramolecular hetero diels-alder reactions of 2-Aza-1,3-butadienes. A stereoselective sequential synthesis of annulated tetrahydropyridines

✍ Scribed by Tietze, Lutz F. ;Utecht, Jens

• Publisher: Wiley (John Wiley & Sons)
• Year: 1992
• Tongue: English
• Weight: 542 KB
• Volume: 125
• Category: Article
• ISSN: 0009-2940
• DOI: 10.1002/cber.19921251014

✦ Synopsis

Azabutadienes f Isoxazoles f Tetrahydropyridines 1 Diels-Alder reactions / Sequential transformations Condensation of aldehydes 1 ae with 5-amino-3-methylisoxazole (4) gives the corresponding imines 5a-e with a 2-aza-1,3-butadiene moiety, which cyclize selctively, e.g. 5a to form the trans-fused tetrahydropyridine 7a and 5c to yield the cisfused cycloadduct 8c. The astounding difference in the selec-tivity of these reactions is explained by electronic effects and suggests a change in the dominating interactions of the orbitals in the transition structure. The structure of ;la is elucidated by an X-ray analysis.