Benzene derivatives interesting examples

Many interesting photochemical reactions are possible with pyran-2-one and its various alkyl and benzo derivatives. For example, irradiation of 2-oxo-2/7-l-benzopyran 4-carbonitrile 170 in the presence of excess 2,3-dimethylbut-3-ene in Ar-degassed benzene provided imino-substituted cyclopenta[c]annelated product 171 (Scheme 19)... 

From a biocatalytic point of view the most interesting question to be answered is what enables these enzymes to catalyze the monooxygenation of even relatively inert chemical substrates, such as benzene derivatives, imder mild conditions. To answer this question several examples of monooxygenases, with different cofactors used to perform the job, will be discussed. 

An interesting example of a program simulating a laboratory course in chemical S5mthesis is given by Smith ) and First, the student chooses a compound, say a benzene derivative, he wants to synthetize. This may be done in the following way ... 

In the reaction with nitrosobenzene, azoxybenzene and Ni(PhN02>2 are formed. The nickel complex is an interesting example of a" coordination compound of a nitro derivative with a zerovalent metal. The X-ray analysis of this compound has been undertaken 383, but the final structure has not yet been reported. The reaction with Bu NC can be carried out catalytical 1y. Thus a mixture of PhNO and Bu NC in benzene, in the presence of a catalytic amount of NiCBu NO at reflux, produces Bu NC0( SOX based on PhNO) along with PhN=C=NBu, PhN=NPh and [Pg.105]

In the context of this work we found it interesting to make the transition from ion spectroscopy in the gas phase to ion photochemistry in liquid solution. While the basic processes are still the same the different environment drastically modifies the results known from gas phase studies. The mobility of ions and electrons in solution is greatly different, the energy of the spectroscopie states is changed, and reactive interaction with the solvent or other added species becomes possible. A very first step in this direction of preparative ionic photochemistry was reported before from our laboratory treating the benzene molecule as an example. More results have now been obtained relating to the mechanism of ion fonnation and its yield, the nature of the intermediates, and the conditions favouring product yield. As a first case the conversion of benzene to phenol and biphenyl in aqueous solution was studied followed by the study of reactions of benzene derivatives in water and other solvents /3/. 

Tripodal benzene-derived ligands have also been used as siderophores (strong complexants for Fe " ) which are of significant biochemical and medical interest. The chemistry and biology of siderophores, which feature a number of interesting natural podands such as mycobactin, have recently been comprehensively reviewed. One early example is the tricatecholate mesitylene derivative 33 which... 

Caution may be required in oxidation reactions. Ceric salts, for example, can alter or destroy products. Ferric salts seem to be more active in 1 N hydrochloric acid solution (P. Schudel, personal communication), but the acidic conditions may affect products such as enol ethers. Temperatures also seem to be important in some cases. For example, a substituted cyclohexa-diene complex was unaffected by CuClj at —20°, but it was converted into the free conjugated diene (mainly) at 0° and into the unconjugated diene and substituted benzene derivative at +20° (A. J. Birch and C. Sell, unpublished). In other cases, e.g., arylmanganese derivatives, although interesting synthetic reactions occur, the metal is not so readily removed. This general area is clearly one for further research if useful application is to be made in organic synthesis. 

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