Dienophiles propanal

Examples of the use of alkylidenecyclopropanes as dienophiles are very limited in the literature. Moreover, the few examples reported deal with rather sophisticated substrates such as 2,2-difluoromethylenecyclopropane, diarylmethylene-cyclopropanaphthalenes, bicyclopropylidene and (diacylmethylene)cyclo-propanes. 

As a specific example of the vinylallenes, 294 demonstrates that not only can common dienophiles such as maleic anhydride (MA) be added (to furnish adduct 295 with a rich functionality) [122], but also carbonyl compounds such as propanal to afford 296 when the reaction is carried out in the presence of a Lewis acid catalyst [27]. 

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