The magnesium-mediated addition of bromoform to conjugated electron-deficient alkenes
and imines, such as para-quinone methides (p-QMs) and aurone-derived azadienes, respectively, is reported here for the first time.
While p-QMs undergo exclusive and hitherto unreported 1,6-addition of bromoform to afford
benzylic tribromomethylated diarylmethanes, aurone-derived azadienes undergo both
1,2- and 1,4-additions to furnish α- and γ-tribromomethylamines. A mechanism involving
the intermediacy of the tribromomethyl radical has been proposed based on control
experiments and EPR studies. Representative synthetic transformations have also been
carried out.
Key words
magnesium-mediated addition - bromoform - conjugate addition -
p-quinone methides - azadienes - diarylmethanes