Rearrangement aza-di-7r-methane

Armesto, Horspool and coworkers have extensively studied the related rearrangement of unsaturated imine derivatives, the so-called aza-di-7r-methane rearrangement. A particularly interesting example is seen by the rearrangement of 75 to 76 (Scheme l9). Adduct 76 furnished chrysanthemic acid following a simple series of steps, it has been... 

Further studies of the aza-di-7r-methane rearrangement have been reported. The ease with which jS,y-unsaturated oxime acetates... 

A study of the di-Ti-methane reactivity of the barrelene derivatives (73) in zeolites has been published. The reaction in a slurry affords a 77 23 mixture of (74) and (75) when the reaction is carried out in a zeolite the cyclooctatetraene product is suppressed and the two products are obtained in a ratio of 1 99. This enhancement of the di-Ti-methane reactivity occurs with Li" - and Na -exchanged zeolites.Liao and co-workers have reported new reactivity of some barrelenes. The reactions encountered are sensitive to substitution pattern. Thus, the irradiation of (76) with electron withdrawing groups follows the di-TT-methane route, to yield (77) and (78) predominantly. The less heavily substituted derivative (79) behaves differently, and irradiation affords (80) and (81) by the aza-di-7r-methane rearrangement, with (82) formed only in small amounts by the alternative di-Ti-methane path. Calculations have been used to examine the mechanism of the barrelene-semibullvalene isomerization. These results indicate that two biradical intermediates are involved in the T state. Other calculations on the di-Ti-methane rearrangement of barrelene substantiate the Zimmerman mechanism for the sensitized rearrangement. 

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