Arylhydrazines (ArNαHNβH2) are ambident nucleophiles. We describe here their reactivity with benzynes generated in situ by thermal cyclization of several multiynes. Products arising from attack of both the alpha- and beta-nitrogen atoms are observed. These competitive modes of reaction were explored by DFT calculations. Substituent effects on the site-selectivity for several substituted phenylhydrazines were explored. Interestingly, the hydrazo products from beta-attack (ArNHNHAr') can be oxidized, sometimes in situ by oxygen alone, to give structurally complex, unsymmetrical azoarenes (ArN=NAr'). Toluenesulfonohydrazide and benzohydrazide analogues were each demonstrated to undergo similar transformations, including oxidation to the corresponding benzyne-trapped azo compounds.
Bibliographical noteFunding Information:
This research was supported through the National Institutes of General Medical Sciences of the U.S. Department of Health and Human Services (R35 GM127097). Support for some of the instrumentation came from an NIH Shared Instrumentation Grant (S10OD011952, NMR) and an NIH Cancer Center Support Grant (CA-77598, MS). DFT calculations were performed with resources provided by the Minnesota Supercomputing Institute.
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