A Stepwise [4 + 3] Cycloaddition Reaction of the 1,3-Diphenyl-2-azaallyl Anion

Mayr, Herbert; Heigl, Ulrich W. und Baran, Janusz (1993): A Stepwise [4 + 3] Cycloaddition Reaction of the 1,3-Diphenyl-2-azaallyl Anion. In: Chemische Berichte, Bd. 126, Nr. 8: S. 1913-1916

Abstract

The 1,3-diphenyl-2-azaallyl anion (1) undergoes [3 + 2] cycloaddition reactions with the s-cis-fixed 1,3-dienes 8-11. In contrast, 1,1,2,2,3,3-hexamethyl-4,5-bis(methylene)cyclopentane (7) reacts with 1 to give the [4 + 3] cycloadduct 13 and the linear 1,4-addition product 14. This reaction is four orders of magnitude slower than the corresponding reaction of 1 with 1,2-bis(methylene)cyclopentane (8), which exclusively yields [3 + 2] cycloadducts. A change of mechanism - concerted cycloaddition of 8 and stepwise cycloaddition of 7 - is suggested, but not unequivocally proven. It is concluded that reactions of 1 with ordinary dienes cannot profit from concertedness by more than 5 kcal · mol-1.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Chemie und Pharmazie
• Themengebiete: 500 Naturwissenschaften und Mathematik > 540 Chemie
• Signatur: Chem. 26 h-126,5/8