Consecutive rearrangements

With appropriate substrates, two or more consecutive rearrangements may take place. The carbon skeleton of the starting material may then suffer a major structural reorganization ... 

The direct reduction itself may be suppressed by adding the tributyltin hydride slowly over several hours, thus keeping its concentration as low as possible. In this case, however, consecutive rearrangements sometimes lead to different products.1,2 Stereochemistry may be a decisive factor for the outcome of the rearrangement.1-1 4 For example, in the bicyclo[3.2.0]hept-2-en-6-one series, the exo-derivative exo-1 underwent ring enlargement to a cycloheptanone 2, while the e c/o-diastereomer enclo-1 reacted at the C —C double bond to form a tricyclic isomer 3.1-2... 

F. E. Ziegler, Consecutive Rearrangements, in Comprehensive Organic Synthesis (B. M. Trost, I. Fleming, Eds.), Vol. 5,875, Pergamon Press, Oxford, 1991. 

The application of consecutive rearrangements to aliphatic systems has been exceptionally rewarding. A seminal contribution is provided by the work of Thomas, who has prepared p-sinesal (26 equation 7), a constituent of the essential oil of the Chinese orange, by the tandem Claisen-Cope rearrangement. ... 

The relation between 8 and the number of photons absorbed per unit time is introduced in Eq. (6) [50, 73]. With the condition that F = I/hco and dW/dt = fiiVph/dtjhoj (iVph = number of photons), one obtains by substitution of these expressions into Eq. (6) and consecutive rearrangement the relation depicted in Eq. (14),4 describing the dependence of <5 on the material parameter y(3) [50, 53, 55, 73, 129, 272-274], if both photons have the same frequency ... 

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