Benzynes produced thermally by the cycloisomerization of triyne-containing precursors [i.e., by the hexadehydro-Diels-Alder (HDDA) reaction] react with phenols at the carbon ortho to the hydroxyl in an enelike fashion. Following tautomerization of the intermediate cyclohexadienones, this produces biaryl derivatives. DFT calculations of model reactions support this mechanistic interpretation. Substituted, unsymmetrical phenols and bis-phenols react in a fashion that can be explained by engagement of the most readily available (non-hydrogen-bonded) hydroxyl in the phenol-ene process.
Bibliographical noteFunding Information:
This work was supported by the National Institute of General Medical Sciences of the National Institutes of Health (GM65597). We thank Mr. Sean Ross (University of Minnesota) for providing a portion of the characterization data for compounds S4 and 6. NMR data were obtained with instrumentation acquired, in part, through the NIH Shared Instrumentation Grant program (S10OD011952). D.N. received support from a Doctoral Dissertation Fellowship of the University of Minnesota Graduate School.
© 2016 American Chemical Society.