Trifluoromethyl group shows a stabilizing effect on the compounds which would be unstable if they had no trifluoromethyl group. This review is concerned with two faces of the chemistry of trifluoromethylated valence bond isomers of aromatic compounds : Diels-Alder and 1, 3-dipolar reactions planned for the conversion of hexakis (trifluoromethyl) benzvalene to the corresponding tetrahedrane and the synthesis of new valence bond isomers of heteroaromatic compounds. In the former, the tetrahedrane itself could not yet be isolated, but the formation of tetrakis (trifluoromethyl) cyclobutadiene and new valence isomers of oxepin was confirmed. In the latter, Dewar thiopene, Dewar pyrrole, Dewar pyridine, and diphosphabenzvalene with trifluoromethyl groups were synthesized and their reactions were discussed. The effect of trifluoromethyl group is not limited to the strained compound. Thus, tetrakis (trifluoromethyl) -1, 4-diphosphabenzene, the first example of diphosphabenzenes, was synthesized.
Recent achievements in the field of three-dimensional aromaticity (bicycloaromaticity and homoaromaticity) have been reviewed with emphasis on the syntheses of stabilized longicyclic (CH) n ions- bicyclo [3.2.2] nonatrienyl, bicyclo [4.2.1] nonatrienyl, bicyclo [3.3.2] decatrienyl, and bicyclo [4.3.2] undecatetraenyl ions-and the first trishomoaromatic anion-tricyclo [5.3.1.04, 8] undeca-2, 5, 9-trien-11-ide ion. It is now apparent that the predictive power of the three-dimensional aromaticity theory based on Goldstein-Hoffmann' s formulation of ribbon mode remains to be a stimulus guide to the syntheses of organic ions despite its limited experimental manifestation at the present time. (57 references)
Although the Ullmann condensation has played an important role in a larger number of chemical manufacturing industries, especially those of dyestuffs, drugs, and many other chemicals, the mechanistic studies have been scarcely reported in the literature. From the practical point of view, the information as to catalytic species will be expected to allow the setting up of the more effective synthetic conditions. We have studied the mechanism of the Ullmann codensation reaction in order to aquire more knowledge as the “true” catalytic species in this reaction. In this paper our results obtained by mechanistic and kinetic studies on the Ullmann condensation reaction between haloanthraquinones and amines are briefly reviewed. In the reaction of bromamic acid with anilines in the alkaline aqueous solution, the active catalyst was concluded to be the monomeric cupric species, having a cuprous character, on the basis of the kinetic results, the ESR observations, and the effects of the added anions and chelates. The addition of reducing agents, such as FeSO4, astonishingly enhanced the reaction rate. The reactivities of amines are showed to depend on both their basicities and polarizabilities. On the other hand, in the case of the reaction between haloanthraquinones and amines in non-aqueous solution the cuprous species was showed to be active as catalyst, while the cupric one was almostly inactive. In this reaction system the cupric species, formed in the course of the reaction, increased the reaction rate. The role of the cupric species in the reaction are discussed from the stand point of kinetics. The reaction mechaism of those reactions and the role of the copper species as catalyst are tentatively proposed and discussed.
The present review represents some of the recent developments in industrial syntheses of terpenoids. The main topics are [1, 3] -transpositions [allyl-, Carroll-, Claisen-, and Cope-rearrangement etc.] and applications of catalysts [oxo-reaction, methathesis, oxidative coupling reaction]. Specific industrial examples are given, and the advantages and disadvantages of these reactions are discussed. In the evaluation of a reaction the industrial point of view is emphasized.
The action of Zr in the catalyst was studied using electron-microprobe X-ray analizer, X-ray diffractometer and thermal balance. It was suggested that Cu ion-exchanged zirconium phosphate was formed on the surface of carrier and promoted the dispersion of catalytic compound.