The benzylic deprotonation of tricarbonyl(eta(6)-1-tertbutoxycarbonyl-2,3-dimethylbenzene)chromium occurs preferentially at the ortho position, whereas the meta position is still reactive but to a lesser extent. X-ray study of the title compound, [Cr(CO)(3)(C10H10O2)], obtained in a very good yield, confirms this result and shows a strong hydrogen bond between neighbouring carboxy groups, The acid group and the phenyl ring are coplanar and the torsion angle between the phenyl ring and the vinyl group is 61.2 degrees(4).
Double ortho meta regiocontrolled functionalisation of tricarbonyl-(η6-1-tert-butoxycarbonyl-2,3-dimethylbenzene) chromium; 17O NMR study of saponification-elimination mechanism
The title compound 1 promotes the attachment of an electrophilic group preferentially to the 2-methyl group while the 3-methyl group reacts slightly. A condensation mechanism of 1 with aldehyde involving a lactonisation step is confirmed by a labelling experiment.