Toluene tricarbonyl chromium

Optically pure N-aryl carbazole 364 with a planar chirality was transformed into 365 presenting axial and planar chirality by a totally diastereoselective migration of the tricarbonyl chromium. Interestingly, the enantiomeric excess in 365 was high at the beginning of the transfer and decreased after 2 h in refluxing toluene. A slow racemization stemmed from a slippage of the tricarbonyl chromium from one phenyl of the carbazole to the other. 

It was found that the benzene, toluene, mesitylene, durene and hexamethylbenzene tricarbonyl chromium could best be separated and quantitatively determined in mixtures by use of temperature programming with the flame ionization detector. Figure 204 illustrates the separation achieved. It can be seen that the resolution is excellent, and that the retention times of the early components are far enough removed from the tail of the solvent peak that measurements from the original base line are possible in each case. Under isothermal conditions (135°C) using flame ionization, the benzene tricarbonyl--chromium and toluene tricarbonylchromium peaks eluted on the tail of the benzene peaks and the retention time of the hexamethylbenzene tricarbonylchromium was 32.6 minutes. This peak was also considerably broader and flatter when eluted isothermally. For this determination therefore, programmed temperature operation is the most efficient means of analysis not only is the resolution improved, but also the total time of analysis is reduced to 15 minutes. 

Photolysis of several arene chromium tricarbonyls (Ar Cr ( 0)3) (Ar = benzene, toluene, or xylene) and... 

Stereoselective chromium tricarbonyl migration was achieved in the sterically hindered A -aryl indole chromium complex 178b by refluxing in toluene (Equation 34) <20060L1097>. 

The formation of the inclusion compounds was selective. /3-CD formed 1 1 inclusion compounds with benzene, toluene, and o-xylene chromium tricarbonyl complexes, and not with w-xylene, />-xylene, guaiacol, methyl anthrani-late mesitylene, or hexamethylbenzene chromium tricarbonyl complexes. Whereas a-CD did not form inclusion complexes with any arene chromium complexes, 7-CD formed 1 1 inclusion complexes with all arene chromium... 

The use of 7r-arene-Cr(CO)3 complexes in organic synthesis continues to attract attention. Carbanion attack on 7r-anisole- and 7r-toluene-chromium tricarbonyl complexes gives, after oxidative work-up, meta-substituted aromatics as the major product [equation (24)]. With the anisole complex the me/a-substituted product... 

Predominant or exclusive formation ofmeta-substituted aromatics occurs by carbanion attack on (toluene)- or (anisoIe)chromium tricarbonyl (Semmelhack and Clark, 1977). The direct alkylation of (ethylbenzene)chromium tricarbonyl has been reported by Card rmd Trahanovsky (1973). 

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