Synthesis of Functionally Substituted Bicyclo[4.2.1]nona-2,4-dienes and Bicyclo[4.2.1]nona-2,4,7-trienes by Cobalt(I)-catalyzed [6π + 2π] Cycloaddition of 2-Tropylcyclohexanone

Abstract

The [6π + 2π] cycloaddition of 2-tropylcyclohexanone to allenes and alkynes was accomplished for the first time using the three-component catalytic system Co­(acac)2(dppe)/Zn/ZnI2, thus giving previously unknown functionally substituted bicyclo[4.2.1]­nona-2,4-dienes and bicyclo[4.2.1]­nona-2,4,7-trienes in high yields (70–89%). The structures of the synthesized carbocycles were reliably proved using modern spectral methods and X-ray diffraction. The in vitro cytotoxic activity of the obtained bicyclo[4.2.1]­nona-2,4-dienes and bicyclo[4.2.1]­nona-2,4,7-trienes against the Jurkat, K562, and U937 tumor cell lines has been studied.

Synthesis of New Functionally Substituted 9-Azabicyclo[4.2.1]nona-2,4,7-trienes by Cobalt(I)-Catalyzed [6π + 2π]-Cycloaddition of N-Carbocholesteroxyazepine to Alkynes

“…Our experiments clearly demonstrated the Co(acac) 2 (dppe)/Zn/ZnI 2 three-component catalytic system [ 52 , 53 , 54 , 55 , 56 , 57 ] being not only tolerant but equally efficient for a large variety of the substituents (alkyl, phenyl, p- halophenyl, alcohol, nitrile, ester, sulfide, phthalimide, cycloalkane, naphthalene, and phenanthrene) in the starting alkynes.…”

“…With N -carbocholesteroxyazepine 2 in our hands, we investigated its cycloaddition to the terminal alkynes 3a–t . Thus, we found that the desired [6π + 2π]-cycloaddition process occurred, being catalyzed by the Co(acac) 2 (dppe)/Zn/ZnI 2 (dppe-1,2-bis(diphenylphosphino)ethane) system [ 52 , 53 , 54 , 55 , 56 , 57 ] under developed conditions (10 mol% Co(acac) 2 (dppe), 30 mol% Zn, and 20 mol% ZnI 2 , in DCE (1,2-dichloroethane) as solvent, for 20 h at 60 °C) to afford substituted 9-azabicyclo[4.2.1]nona-2,4,7-trienes 4a–t with 79–95% yields ( Scheme 5 ). The adducts were formed as two N-(CO)O-cholesteryl rotamers [ 33 , 34 , 39 , 40 , 41 ] in a 1:1 ratio, arising due to hindered rotation of the substituent around the CN bond.…”