No abstract

This paper describes the synthesis and reactivity of a novel class of quinone boronic esters. These compounds are prepared utilizing a highly regioselective Dötz annulation of Fischer carbene complexes with alkynylboronates. All substrates studied to date provided a single regioisomeric arylboronic ester product; the origin of this selectivity is discussed in the context of steric and electronic effects. Additionally, these compounds have been found to undergo Pd-catalyzed coupling reactions with a range of aryl and allyl halides and provides a strategy for the selective and predictable preparation of highly substituted quinones and hydroquinones. Finally, the propensity of this technique to prepare highly functionalized aromatic compounds in an expeditious fashion is demonstrated in the total synthesis of dimeric carbazole (+/-)-bis-N-dimethylbismurrayaquinone-A 33.

Alkynylboronates participate in 1,3-dipolar cycloaddition reactions with nitrile oxides to provide isoxazoleboronic esters with excellent levels of regiocontrol; additionally, these potentially valuable synthetic intermediates have been shown to participate efficiently in Suzuki coupling reactions.

A novel and highly regioselective route to quinone boronic ester derivatives has been developed using a Fischer carbene mediated benzannulation process.