Regioselective Synthesis of <i>o</i>-Benzenediboronic Acids via Ir-Catalyzed <i>o</i>-C–H Borylation Directed by a Pyrazolylaniline-Modified Boronyl Group
Ir-catalyzed ortho-directed C–H borylation of pyrazolylaniline (PZA)-modified arylboronic acids with bis(pinacolate)diboron afforded o-benzenediboronic acids in which two boronyl groups are differentially modified by pinacol (PIN) and PZA. By using this borylation after nondirected Ir-catalyzed C–H borylation, o-benzenediboronic acids are conveniently synthesized from unfunctionalized arenes. The differentially
Accessing Polyoxygenated Dibenzofurans via the Union of Phenols and <i>o</i>-Benzoquinones: Rapid Syntheses of Metabolites Isolated from <i>Ribes takare</i>
作者:Meng Yao Zhang、Russell A. Barrow
DOI:10.1021/acs.orglett.7b00840
日期:2017.5.5
construction of polyoxygenated dibenzo[b,d]furan frameworks from the union of substituted phenols/naphthols and o-benzoquinones via a Michael-oxidation-oxa-Michael cascade is reported. The power of this transformation is demonstrated in the generation of a library of highlysubstituted dibenzofurans, featuring specifically substituted molecules containing broad ranges of functionality. The utility of this
to the success of the reaction is the activation of the B–Br bond of bromoboranes with a Lewis base such as 2-MeO-py. The activation ensures that bromoboranes will react with the active nickel(I) catalyst prior to aryl halides, which is different from the sequence of the general nickel-catalyzed reductive C(sp2)–C/Si cross-coupling, where the oxidativeaddition of an aryl halide proceeds first. Notably