Rhodium(III)‐Catalyzed Regioselective C−H Allylation and Prenylation of Indoles at C4‐Position

Abstract

Herein, Rh(III)-catalyzed C4-selective CÀ H allylation and prenylation of indoles by using a weak carbonyl coordination directing group have been reported. By employing 5-methylene-1,3-dioxan-2-ones, 4-vinyl-1,3-dioxolan-2-ones and 2-methyl-2,3-butadiene as scalable cross-coupling partners, these divergent synthesis protocols proceed smoothly under redox-neutral reaction conditions, delivering various allylated and prenylated indoles in moderate to satisfied yields. This transformation exhibits high functional-groups compatibility and broad substrate scope. Scale-up experiment and mechanistic studies were also accomplished.

A divergent construction of fused and bridged carbo-/heterocyclic scaffoldsviacascade reactions of aryl azomethine imines with vinyl cyclic carbonates

“…After having established a general synthetic approach for the preparation of indene-fused pyrazoles 3 , we were interested in expanding the scope of vinyl cyclic carbonate from 2 to 5-methylene-1,3-dioxan-2-one ( 4 ). 9 As 4 has different structural characteristics compared with 2 , we were curious whether aryl azomethine imines ( 1 ) would be able to couple with 4 to give an alkylation intermediate. If so, we were eager to know whether this intermediate could take part in another version of intramolecular [3 + 2] cycloaddition.…”

Rhodium(iii)-catalyzed regioselective C(sp2)–H activation of indoles at the C4-position with iodonium ylides

“…Compared to diazo compounds, iodine ylides are thermodynamically stable, safe, inexpensive and readily available. Therefore, based on our continuous studies on C–H functionalization of indoles and previous work, 15 we now report rhodium( iii )-catalyzed regioselective C(sp 2 )–H activation of indoles at the C4-position with iodonium ylides, which gave important coupling products bearing axial chiral centers (Scheme 1d). This transformation features mild and redox neutral reaction conditions, high yields, and good tolerance of functional groups.…”

Transition-Metal-Catalyzed Directing-Group-Assisted C4-H Carbon–Carbon Bond Formation of Indole

“…Recently, a regioselective C4-allylation and prenylation of indoles have been accomplished utilizing pivaloyl DG under Rh(III)-catalysis (Scheme 13). 33 5-Methylene-1,3-dioxan-2-one and vinyl ethylene carbonate were employed to afford branched or linear allyl derivatives, while substituted allenes served as a prenylation source. The chemoselective allylation at C4-site was achieved by altering the additive and solvent at moderate temperature.…”