Catalytic oxidative cross-dehydrogenative coupling between unactivated C(sp)-H and C(sp)-H bonds is achieved by the cobalt-catalyzed o-alkylation reaction of aromatic carboxamides containing (pyridin-2-yl)isopropyl amine (PIP-NH) as a N,N-bidentate directing group. Many different C(sp)-H bonds in alkanes, toluene derivatives and even in the α-position of ethers and thioethers can be used as coupling partners. This method has a broad substrate scope and the tolerance of various functional groups.
In this paper is described a synthesis of enantiomerically enriched, configurationally stable organozinc reagents by catalytic enantioselective carbozincation of a vinylboronic ester. This process furnishes enantiomerically enriched α-borylzinc intermediates that are shown to undergo stereospecific reactions, producing enantioenriched secondary boronic ester products. The properties of the intermediate α-borylzinc reagent are probed and the synthetic utility of the products is demonstrated by application to the synthesis of (−)-aphanorphine and (−)-enterolactone.
The first cobalt-catalyzed direct methylation of a C(sp(2) )-H bond using dicumyl peroxide (DCP) as both the methylating reagent and hydrogen acceptor has been established. The reaction proceeded without the use of any additives, and was proven to be applicable to various amides bearing a 2-pyridinylisopropyl (PIP) directing group, providing an efficient access to o-methyl aryl amides with high functional-group tolerance. Preliminary mechanistic studies suggest a radical process would be involved in the catalytic process.
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