RESUMO
We have developed an electrochemically driven strategy for the stereoselective synthesis of protected syn-1,2-diols from vinylarenes with N,N-dimethylformamide (DMF). The newly developed system obviates the need for transition metal catalysts or external oxidizing agents, thus providing an operationally simple and efficient route to an array of protected syn-1,2-diols in a single step. This reaction proceeds via an electrooxidation of olefin, followed by a nucleophilic attack of DMF. Subsequent oxidation and nucleophilic capture of the generated carbocation with a trifluoroacetate ion is proposed, which gives rise predominantly to a syn-diastereoselectivity upon the second nucleophilic attack of DMF.
RESUMO
Reported is a tandem palladium-catalyzed Heck/regioselective C(sp3 )-H activation reaction for the divergent synthesis of spiro- and fused-cyclopropanated indolines from N-methallylated 2-bromoarylamides. The regioselectivity of the C-H bond activation in the σ-alkylPdII intermediate is controlled by the solvent used. DFT calculations suggest that the polarity of solvent molecules could influence the transition-state energy, leading to a bifurcation of the C-H bond activation in the σ-alkylPdII intermediate.
RESUMO
Recent advances in transition metal-catalyzed C-H bond functionalization have profoundly impacted synthetic strategy. Since organic substrates typically contain several chemically distinct C-H bonds, controlling the regioselectivity of C-H bond functionalization is imperative to harness its full potential. Moreover, the ability to alter reaction pathways to selectively functionalize different C-H bonds in a substrate represents a greater opportunity and challenge. The choice of catalysts, ligands, solvents, and even more subtle variations of the reaction conditions have been shown to allow the formation of regioisomeric C-H functionalization products starting from the same precursors. This review describes recent advances in transition metal-catalyzed divergent C-H bond functionalization that highlight its potential in organic synthesis.
