A Pd-catalyzed, site-selective p-hydroxyphenyloxylation of benzylic α-C(sp)-H bonds with 1,4-benzoquinone using thioamide as a directing group is reported. 1,4-Benzoquinone is employed as the p-hydroxyphenyloxy source without extra oxidants. This method exclusively gives site selectivity at α-C(sp)-H bonds rather than the usual β-C(sp)-H bonds through C-H activation mode. The reactions proceed with high functional group tolerance in yields of 42-93%.
A novel organocatalytic [3+2] annulation/oxidative aromatization reaction of enals with 2-halophenols or β-naphthols is reported. This process enables chemo- and regioselective access to 2-arylbenzofuran-3-carbaldehydes without the use of transition metals or strong oxidants. Preliminary mechanistic studies reveal that an unprecedented, organocatalytic, direct α-arylation pathway is involved.
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