Synthesis of novel quinone boronic ester derivatives via a highly regioselective Cr-mediated benzannulation reaction and their application in Pd-catalyzed coupling processes

This paper describes the synthesis and reactivity of a novel class of quino ne boronic esters. These compounds are prepared utilizing a highly regiosel ective Dotz 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 o f steric and electronic effects. Additionally, these compounds have been fo und to undergo Pd-catalyzed coupling reactions with a range of aryl and all yl halides and provides a strategy for the selective and predictable prepar ation of highly substituted quinones and hydroquinones. Finally, the propen sity 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.