General Approach To Construct Azepino[2,3-:4,5-']diindoles, Azocino[2,3-:4,5-']diindoles, and Azonino[2,3-:4,5-']diindoles via Rh(II)-Catalyzed Reactions of 3-Diazoindolin-2-imines with 3-(Bromoalkyl)indoles.

Rh(II)-catalyzed reactions of 3-diazoindolin-2-imines with 3-(2-bromoethyl)indoles, 3-(3-bromopropyl)indoles, and 3-(4-bromobutyl)indoles, followed by treatment with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in a one-pot operation furnished azepino[2,3-:4,5-']diindoles, azocino[2,3-:4,5-']diindoles, and azonino[2,3-:4,5-']diindoles, respectively.

A copper-catalyzed reaction of 3-diazoindolin-2-imines with 2-(phenylamino)ethanols: convenient access to spiro[indoline-3,2'-oxazolidin]-2-imines.

3-Diazoindolin-2-imines reacted with chiral 2-(phenylamino)ethanols under copper catalysis to furnish chiral spiro[indoline-3,2'-oxazolidin]-2-imines in good yields with excellent diastereoselectivity. The reaction undergoes a copper-catalyzed cascade process involving the formation of copper carbene, C-N coupling, and C-O coupling.

BF-Promoted Divergent Reactions between Tryptophols and Propargylic Alcohols.

Trifluoroboron-promoted cascade reactions between tryptophols and propagylic alcohols furnished three types of skeletons, including carbazoles, cyclopenta[b]furo[2,3-b]indoles, and allenyl furo[2,3-b]indoles, with excellent selectivity based on the substrate structure. Tryptophols without a substituent on the 2-position of the indole ring reacted with 1,1,3-triphenylprop-2-yn-1-ol and 9-(phenylethynyl)-9H-fluoren-9-ol to give carbazoles and cyclopenta[b]furo[2,3-b]indoles, respectively, while the reaction of 2-substituted tryptophols afforded allenylfuro[2,3-b]indoles.

From 1-Sulfonyl-4-aryl-1,2,3-triazoles to 1-Allenyl-5-aryl-1,2,3-triazoles.

An efficient and highly regioselective synthesis of 1-allenyl-5-aryl-1,2,3-triazoles from 1-sulfonyl-4-aryl-1,2,3-triazoles is disclosed. 1-Sulfonyl-4-aryl-1,2,3-triazoles reacted with propargylic alcohols in the presence of trifluoroboron etherate to furnish 1-allenyl-5-aryl-1,2,3-triazoles. When secondary alcohols were used as substrate, the outcome of the reaction was 1-alkyl-5-aryl-1,2,3-triazoles.

α-Amidino Rhodium Carbenes: Key Intermediates for the Preparation of (E)-2-Aminomethylene-3-oxoindoles and Pyranoindoles.

Rhodium-catalyzed reactions of 3-diazoindolin-2-imines with aromatic aldehydes and α,β-unsaturated aldehydes respectively furnished (E)-2-aminomethylene-3-oxoindoles and pyranoindoles in moderate to excellent yields with nice functional group tolerance. The reaction proceeds in a cascade involving α-amidino rhodium carbene as the key intermediate.

Preparation of 3-aryl-2-aminoindoles, 3-allyl-3-amino-2-iminoindolines, and tetrahydro-[1,4]diazepino[2,3-b]indoles from 3-diazoindolin-2-imines.

The rhodium-catalyzed reactions of 3-diazoindolin-2-imines with N,N-dialkylanilines, N-allyl-N-alkylanilines, and N-propargyl-N-alkylanilines and 3-diazoindolin-2-imines furnished 3-aryl-2-aminoindoles, 3-allyl-3-amino-2-iminoindolines, and tetrahydro-[1,4]diazepino[2,3-b]indoles, respectively. 3-Diazoindolin-2-imines acted as precursors of α-imino rhodium carbenes in these transformations.

Preparation of 3-diazoindolin-2-imines via cascade reaction between indoles and sulfonylazides and their extensions to 2,3-diaminoindoles and imidazo[4,5-b]indoles.

3-Diazoindolin-2-imines were constructed from indoles and sulfonylazides via an electronically matched 1,3-dipolar cycloaddition and a subsequent dehydroaromatization/ring-opening cascade. The reaction between 3-substituted indoles and sulfonyl azides provided 2-aminoindoles, while 2-substituted indoles furnished 3-aminoindoles. Moreover, 2,3-diaminoindoles could be prepared from the resulting 3-diazoindolin-2-imines and secondary amines via a rhodium-catalyzed amination.

Preparation of triazoloindoles via tandem copper catalysis and their utility as α-imino rhodium carbene precursors.

3-Sulfonyl[1,2,3]triazolo[4,5-b]indoles were efficiently prepared via a tandem catalysis process involving intramolecular ligand stabilized CuAAC and Cu-catalyzed C-N coupling. The obtained 3-sulfonyl[1,2,3]triazolo[4,5-b]indoles could be utilized as α-imino rhodium carbene precursors for the construction of a range of valuable indole molecules including pyrrolo[2,3-b]indoles, spirocyclopropyl iminoindoles, 2,3-dihydropyrrolo[2,3-b]indoles, 3,3'-biindoles, and 2,3'-biindoles.