Thermal rearrangements of 9,10-bis(trifluorovinyl)phenanthrene
摘要:
Results from a study of the thermal unimolecular rearrangement of 9,10-bis(trifluorovinyl)-phenanthrene are reported. Kinetic and product studies indicate that it is unexpectedly resistant to rearrangement, that its expected 6pi electrocyclic rearrangement plays but a minor role, and that the major rearrangement process was a virtually unprecedented thermal reaction for 1,3,5-trienes, that of conversion to a bicyclo[3.1.0]hex-2-ene system (7). Activation parameters are provided for the minor electrocyclic process (DELTAH(double dagger) = 29.9 kcal/mol; DELTAS(double dagger) = -19.6 eu) and for the conversion to 7 (DELTAH(double dagger) = 34.4 kcal/mol; DELTAS(double dagger) = -6.6 eu) as well as for the secondary conversions of 7 to 4-(difluoromethylidene)-3,3,5,5-tetrafluoro-1,2-(9,10-phenanthro)cyclopent-1-ene (8) (DELTAH(double dagger) = 31.3 kcal/mol; DELTAS(double dagger) = -12.7 eu) and to 1,2-(9,10-phenanthro)-3,5,5-trifluoro-4-(trifluoromethyl)-1,3-cyclopentadiene (9) (DLETAH(double dagger) = 31.4 kcal/mol; DELTAS(double dagger) = -13.4 eu). A rarely encountered fluorine steric effect deriving from the stringent steric demands of the reaction's boat-like transition state is invoked to explain the inhibition of 1's electrocyclic process, while equally rare thermal 1,2-fluorine atom shifts are proposed to explain the rearrangement of 7.
Aromatic nitro-compounds. Studies of the amination of 9-nitrophenanthrene and of the mononitrobiphenylenes
作者:J. W. Barton、A. R. Grinham、K. E. Whitaker
DOI:10.1039/j39710001384
日期:——
Nucleophilic aminations of 9-nitrophenanthrene and of 2-nitrobiphenylene have given 9-amino-10-nitrophenanthrene (I; R = NH2) and 2-amino-3-nitrobiphenylene (III; R = NH2) respectively; under the same conditions 1-nitrobiphenylene is unreactive. Some reactions of amines (I; R = NH2) and (III; R = NH2) are described.
Fluorine substituent effects on thermal isomerizations: a new thermal reaction of 1,3,5-hexatrienes
作者:William R. Dolbier、Keith Palmer、Henryk Koroniak、Hua Qi Zhang、Virgil L. Goedkin
DOI:10.1021/ja00003a059
日期:1991.1
Fluorine substituents have been observed to have a remarkable effect upon the rate and stereochemical outcome of the butadiene-cyclobutene thermal conrotatory 4π-electron electrocyclic interconversion. The substituenteffects observed in this system and in other pericyclic systems have enhanced one's understanding of the mechanisms of such reactions, such that only a small probable effect of fluorine