Zimmerman and Schuster

Typical examples of circumambulatory rearrangements of bicyclo[3.1. Ojhexenyl cations are shown in Schemes 19 and 20. Swatton and Hart reported the isomerization shown in Scheme 19 in 1967 and proposed that the observed deuterium scrambling could be accounted for on the basis of a cyclopropyl walk reaction153. This circumambulation is comparable to that proposed by Zimmerman and Schuster as part of the sequence of reactions involved in the type A photorearrangement of 2,5-cyclohexadienones. ... 

Benjamin B. Tregoe and John W. Zimmerman, Top Management Strat-egy What It Is and How to Make It Work (New York Simon and Schuster, 1980). 

As just described, Zimmerman has reported one instance of a dienone rearrangement which definitely does not fit Chapman s general picture. Schuster has provided two reports410,411 of cross-conjugated cyclohexadienones which eliminate radical species. With the trichloro-methyl-substituted ketone 34, both cleavage to the cresol and rearrangement to lumiproduct are quenched by dienes.411 Stern-Volmer quenching plots indicate that the rate at which the excited triplet reacts exceeds 10° sec"1 for both reactions.412... 

Interestingly, the so-called Zimmerman-Schuster oxyallyl zwitterion may be generated independently by a Favorskii-like route, and leads to the same reaction products as obtained photochemically In addition, the stereochemistry of the rearrangement of the zwitterion to the bicyclo[3.1.0]hex-3-en-2-one could be established, since it was found that with two different aryl groups, the endo aryl group in the zwitterion appeared endo in the bicyclic photoproduct and the exo group remained exo ... 

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