Trimethyl trimesate

Acetylenemonocarboxylic esters are more stable at ambient temperatures than the diesters but, nevertheless, the trimer, trimethyl trimesate (benzene-1,3,5-tricarboxylate) (19), has been isolated from reactions involving MP. Other products obtained from this acetylene in situations where water, or ammonia, can be produced are the geometric isomers 20 and 22,24 and the enamine 21, respectively.25 Methyl propiolate with water in benzene yields 20.28... 

J. Rebek, Jr., (1987) first developed a new synthesis of Kemp s acid and then extensively explored its application in model studies. The synthesis involves the straightforward hydrogenation (A. Steitz, 1968), esterification and methylation of inexpensive 1,3,5-benzenetricar-boxylic acid (trimesic acid 30/100 g). The methylation of the trimethyl ester with dimethyl sulfate, mediated by lithium diisopropylamide (V. J. Shiner, 1981), produced mainly the desired aff-cis-1,3,5-trimethyl isomer, which was saponified to give Kemp s acid. 

All the previously reported examples of photoaddition of acetylenes to benzene involve 1,2-cycloaddition and subsequent formation of cyclo-octatetraenes10 (but see ref. 43 for a discussion of the addition of perfluorobut-2-yne to benzene). The report of 1,3-cycloaddition of diphenylacetylene to the trimethyl ester of trimesic acid, is, therefore, of interest as this leads directly to the semibullvalene system.44 The reaction apparently requires 6 days, the yield of the product is low, and the adduct (28) is not isolable in the pure state. The triethyl ester and the acetylene also yield (29) via a stilbene-phenanthrene cyclization of the primary... 

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