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The isolation of acridines from reaction of benzyne with the imines, N-benzylideneaniline and N-benzylidene-4-chlproaniline, and the amidines, N,N-dimethyl-N′-phenylformamidine and N-phenyliminomethylpyrrolidine, provides unambiguous evidence for the formation of transient benzazetidines by 2 + 2 cycloaddition.
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Fishwick et al. (1984) studied this question.
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