1,3-Dipolar Cycloaddition of Nitrile Oxides to 8-Azaheptafulvenes
作者:Remo Gandolfi、Anna Gamba、Paolo Grünanger
DOI:10.3987/com-94-s50
日期:——
Azaheptafulvenes (2) reacted readily with nitrile oxides (1) to give, as a rule, only adducts derived from a reaction involving the C=N moiety of 2. The adducts consisted of a mixture of rapidly equilibrating ''spiro'' and ''condensed'' isomers, i.e. 6 reversible arrow 8, whose ratio was found to be dependent on substituents, temperature and solvent. The zwitterion (7) is an an appealing intermediate both for cycloaddition and isomerisation. Decomposition of the adducts to benzene, R(1)CN and R(2)NCO provided evidence in favor of the presence of the ''norcaradiene'' derivatives (14) (undetectable by nmr) in equilibrium with 6 and 8. Only products arising from the ''spiro'' isomer (6) were obtained in high yields in the catalytic hydrogenation of 6/8.
1,3-Dipolar Cycloaddition Reactions of 2,4,6-Cycloheptatrien-1-imines with Benzonitrile Oxides Leading to 1,2,4-Oxadiazaspiro[4.6]undeca-2,6,8,10-tetraenes
作者:Kazuaki Ito、Katsuhiro Saito
DOI:10.1246/bcsj.68.3539
日期:1995.12
1,3-Dipolarcycloaddition reactions of N-aryl-2,4,6-cycloheptatrien-1-imines with p-substituted benzonitrileoxides afforded [2+3]-type cycloadducts in considerable yields. A study of the substituent effect on the reaction rate revealed that the reactions proceeded through nucleophilic reactions of imines to nitrile oxides. Thermal isomerizations and addition reactions of the adducts showed that the