Sulfur-Directed C7-Selective Alkenylation of Indoles under Rhodium Catalysis.

Regioselective direct functionalization of an indole benzenoid fragment has been a significant challenge because of its inherently lower reactivity. In this report, we introduce a Rh-catalyzed C7-selective alkenylation of indole derivatives using a new sulfur directing group N-SCy. A notable feature of this system is that the directing group is readily installed to the indoles and easily removed after the catalysis under mild conditions.

Thioether-Directed C4-Selective C-H Acylmethylation of Indoles Using α-Carbonyl Sulfoxonium Ylides.

Site-selective direct functionalization of an indole benzenoid core has been a great challenge due to its inherently poor reactivity. We herein demonstrate an iridium-catalyzed C4-selective acylmethylation of indoles using α-carbonyl sulfoxonium ylides as carbene precursors. This method exhibits high efficiency and broad functional group compatibility. The directing group was easily removed or converted to other functionalities after the catalysis. The potential synthetic utility of the coupling products was highlighted by constructing medium-sized polycyclic indoles.

Iridium-Catalyzed Direct C4- and C7-Selective Alkynylation of Indoles Using Sulfur-Directing Groups.

Indoles and their analogues have been one of the most ubiquitous heterocycles during the past century, and extensive studies have been conducted to establish practical synthetic methods for their derivatives. In particular, selective functionalization of the poorly reactive benzenoid core over the pyrrole ring has been a great challenge. Reported herein is an iridium-catalyzed direct alkynylation of the indole C4- and C7-positions with the assistance of sulfur directing groups. This transformation shows a wide range of functional-group tolerance with exceptional site selectivity. The directing group can be either easily removed or transformed after catalysis. The synthetic utility of the alkyne fragment is demonstrated by the derivatization into the core structure of natural indole alkaloids.

Thioether-Directed Selective C4 C-H Alkenylation of Indoles under Rhodium Catalysis.

A thioether-directed Rh(III)-catalyzed C4 selective C-H alkenylation of indoles via the formation of 5-membered metallacycle intermediates is reported. This protocol allows a wide functional group compatibility and broad substrate scope. The directing group can be readily removed or transformed into other functional groups after the C-H functionalization event. The catalytic method is also applicable to related heterocyclic systems involving benzo[ b]thiophene and benzo[ b]furan scaffolds.

Gold(I)-catalyzed hydroindolylation of allenyl ethers.

The gold(i)-catalyzed reaction/rearrangement of allenyl ethers has been investigated in the presence of indoles. Either hydroindolylation or alkylation of an indole with the pendant group of allenyl ether has been observed. The reaction outcome seems to be decided mainly by the nature of the pendant group of the allenyl ether. Control experiments are indicative of an inner sphere mechanism for the hydroindolylation reaction.

A simple method for the preparation of ultra-small palladium nanoparticles and their utilization for the hydrogenation of terminal alkyne groups to alkanes.

A simple and convenient method for the preparation of ultra-small palladium nanoparticles (Pd-NPs) by a modified digestive ripening method is described. These nanoparticles catalyse the hydrogenation of the terminal alkyne groups to alkanes selectively, and show no effect on other labile protecting and internal alkyne or internal/external alkene groups present in the molecule.

Gold(I)-catalysed [1,3] O→C rearrangement of allenyl ethers.

A simple and rapid access to the α-substituted acryl aldehydes has been provided by developing a gold-catalysed [1,3] rearrangement of the allenyl ethers importantly with a record turnover frequency of 4600 h(-1) (at 0.05 mol% of the catalyst concentration) in homogeneous gold(I) catalysis.