Pyrimidine o-quinodimethane

A review of Diels-Alder reactions of fullerenes with acyclic and cyclic dienes has been presented. The addition of substituted pyrimidine o-quinodimethanes (75) to [60]fullerenes yields novel organofullerenes (76) bearing a pyrimidine nucleus covalently attached to the Ceo cage (Scheme 26). The Diels-Alder dimerization of cyclopenta[/]phenanthrene (77) with isobenzindene (78) yields the dimer (79) in 85% yield (Scheme 27). Further evidence has been supplied to support an early reorganization of the r-network in the dimerization of 2-methoxycarbonylbuta-1,3-diene. The Lewis acid-catalysed Diels-Alder reactions of acrylate derivatives of new carbohydrate-based chiral auxiliaries with cyclohexadiene show excellent endo. exo... 

Pyrimidine ort o-quinodimethanes can also be produced from 5,6-dihydrocyclobuta[,y pyrimidine precursors <1997TL4873, 2002MOL507, 2006LOC703>, and in the case of the 2,4-diphenyl example 905, trapping of the intermediate 906 with dimethyl acetylenedicarboxylate was accompanied by aromatization to give dimethyl 2,4-diphenylquinazoline-6,7-dicarboxylate 907 in 50% yield <2002MOL507>. 

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