Benzopinacol, rearrangement

Although zwitterions are mainly considered for their novel ion conductive matrix in this chapter, they are being used as not only as solvents and catalysts for organic reactions [42] but also as organogelators [43]. Zwitterions have been screened as solvent/catalysts for several classical acid-promoted organic reactions such as the Fischer esterification, alcohol dehydrodimerization, and the pinacol/ benzopinacole rearrangement. The zwitterion containing an equimolar trifluoro-methane sulfonic acid is liquid at room temperature. Because they can work as solvent/catalysts, as shown in the reactions discussed in this chapter, zwitterionic liquids should open the door to a whole new area of applications. 

Fig. 45. Catalytic activities of solid acids for reaction of liquids Alkylation of 1,3,5-tri-methylbenzene with cyclohexene (373 K) alkylation of phenol with 1-dodecene rearrangement of benzopinacol. (From Ref. 249.)...

The experiment should be done when there is good prospect for long hours of bright sunshine for several days. The benzopinacol is cleaved by alkali to benzhydrol and benzophenone and it is rearranged in acid to benzopin-acolone. 

Kaupp, G., Haak, M., Toda, F. Atomic force microscopy and solid-state rearrangement of benzopinacol. J. Phys. Org. Chem. 1995, 8, 545-551. 

When aromatic pinacols are reacted with an acid, products often arise from dehydration and rearrangement.5 This general conversion is known as the pinacol rearrangement. The pinacol rearrangement may be promoted by both Brdnsted and Lewis acids.6 In the procedure described here, superacidic triflic acid is reacted with an aryl pinacol and a dehydrative cyclization occurs to give the substituted phenanthrene product. Related to this conversion, the chemistry of benzopinacol in sulfuric acid and triflic acid is contrasted in Scheme 1. We have proposed that the superacidic triflic acid causes the formation of diprotonated intermediates which promote the dehydrative cyclization.4... 

Benzopinacolone has been prepared by rearrangement of benzopinacol. The rearrangement has been carried out by heating benzopinacol with benzoyl chloride,1 with acetyl chloride,2 with acetic acid at 180-200°,2 with dilute sulfuric acid at 180-200°,2 and with concentrated hydrochloric acid at 2000.2 The present procedure is based on the method described by Gomberg and Bachmann.3... 

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