Stereoselective Cycloaddition of Dibenzoxazepinium Ylides to Acetylenes and Fullerene C₆₀. Conformational Behavior of 3-Aryldibenzo[b,f]pyrrolo[1,2-d][1,4]oxazepine Systems

Cycloaddition of dibenzoxazepinium ylides to acetylene carboxylates leads to cis-3-aryl-3,13b-dihydrodibenzo[b,f]pyrrolo[1,2-d][1,4]oxazepinecarboxylates, which smoothly dehydrogenate to the corresponding pyrrole derivatives. The o-bromophenyl-substituted pyrrole, in contrast to the pyrroline analogue, demonstrates atropoisomerism. Stereoselective cycloaddition of dibenzoxazepinium ylides to fullerene C₆₀ gives rise to fulleropyrrolidines with cis-configuration. Restricted Ph group rotation is found in the phenyl derivative. Only one of two possible atropoisomers is formed in the reaction of o-bromophenyl-substituted ylide with fullerene C₆₀. Details of cycloaddition and conformational behavior of cycloadducts were studied by DFT computations.