Thermal Rearrangement of Squaric Acid Bis Trimethylsilyl Ester

THERMAL REARRANGEMENT OF SQUARIC ACID BIS(TRIMETHYLSILYL) ESTER 

Type II dyotropic rearrangements involve double migration but no positional exchange. One such possibility is the squaric acid system in which thermally induced migration of the two ester functions toward the two carbonyl oxygen atoms is an orbital symmetry-allowed [ 7g -1-  

In order to test intramolecularity, crossover experiments were performed using 43 and the Dig-derivative 44 (59). Upon standing for less than 30 minutes at room temperature, a 1 1 molar mixture of 43 and 44 results in a statistical distribution of 43, 44, and 45, as demonstrated by mass spectroscopy. 

Compounds 46, 47, and 48 were also synthesized, since similar intermolecular silyl migrations should likewise induce complete equilibration of the relevant carbon atoms (59). However, the —NMR 

Similar processes involving phenyl groups and such nucleofugal moieties as fluorine, chlorine, and acetate have been reported by Brook (65). Closely related is the thermally induced quantitative exchange of acetate and methyl groups as shown in Eq. (15) (41). Initial mechanistic 

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Thermal Rearrangement of Squaric Acid Bis(trimethylsilyl) Ester... 

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