Rhodium(II)‐Catalyzed Intramolecular Annulation of 1‐Sulfonyl‐1,2,3‐Triazoles with Pyrrole and Indole Rings: Facile Synthesis of N‐Bridgehead Azepine Skeletons

Tandem 1,2-sulfur migration and (aza)-Diels-Alder reaction of β-thio-α-diazoimines: rhodium catalyzed synthesis of (fused)-polyhydropyridines, and cyclohexenes

Rhodium catalyzed synthesis of substituted tetrahydropyridines was accomplished from readily accessible thio-tethered N-sulfonyl-1,2,3-triazoles. The reaction involves tandem rhodium catalyzed 1,2-sulfur migration in β-thio-α-diazoimines, generated from thio-tethered N-sulfonyl-1,2,3-triazoles, to thio-substituted 1-azadiene and subsequent self aza-Diels-Alder reaction. Interestingly, the methodology was effectively extended to the synthesis of fused tetrahydropyridines, dihydropyridines and cyclohexenes through the in situ trapping of the intermediate, 1-azadiene, with various dienophiles such as enol ether, enamine, ketene S,S-acetal, alkyne, alkene and diene. Furthermore, the direct conversion of propargyl sulfides to (fused)-tetrahydropyridines was also achieved through the successful integration of copper and rhodium catalysts in one-pot.

Stereodivergent Intramolecular C(sp(3))-H Functionalization of Azavinyl Carbenes: Synthesis of Saturated Heterocycles and Fused N-Heterotricycles

A general approach for the formation of five-membered saturated heterocycles by intramolecular C(sp(3))-H functionalization is reported. Using N-sulfonyltriazoles as Rh(II) azavinyl carbene equivalents, a wide variety of stereodefined cis-2,3-disubstituted tetrahydrofurans were obtained with good to excellent diastereoselectivity from readily available acyclic precursors. The reaction is shown to be amenable to gram scale, and judicious choice of reaction conditions allowed for stereodivergence, providing selective access to the trans diastereomer in good yield. The resulting products were shown to be valuable intermediates for the direct preparation of fused N-heterotricycles in one step by intramolecular C-H amination or Pictet-Spengler cyclization.

Rhodium(ii)-catalyzed intramolecular formal [4 + 3] cycloadditions of dienyltriazoles: rapid access to fused 2,5-dihydroazepines

Rh(ii)-catalyzed intramolecular formal [4 + 3] cycloadditions of dienyltriazoles have been developed, which enable the efficient synthesis of various fused 2,5-dihydroazepines.

Intramolecular annulation of aromatic rings with N-sulfonyl 1,2,3-triazoles: divergent synthesis of 3-methylene-2,3-dihydrobenzofurans and 3-methylene-2,3-dihydroindoles

The controllable synthesis of 3-methylene-2,3-dihydrobenzofurans 2 and 3-methylene-2,3-dihydroindoles 5 has been developed via cycloisomerization of N/O-tethered aryltriazoles.

A Rh-catalyzed 1,2-sulfur migration/aza-Diels–Alder cascade initiated by aza-vinyl carbenoids from sulfur-tethered N-sulfonyl-1,2,3-triazoles

A novel Rh(ii) catalyzed intramolecular 1,2-sulfur migration/intermolecular aza-Diels–Alder cascade of sulfur-tethered N-sulfonyl-1,2,3-triazoles has been developed, efficiently affording sulfur-containing tetrahydropyridine derivatives.

Divergent synthesis of indole-fused polycycles via Rh(ii)-catalyzed intramolecular [3 + 2] cycloaddition and C–H functionalization of indolyltriazoles

Intramolecular formal [3 + 2] cycloaddition and C–H functionalization of N-sulfonyl triazoles with indoles have been developed to synthesize potential indole-fused polycycles.

Cu-catalyzed transannulation reaction of pyridotriazoles: general access to fused polycyclic indolizines

An efficient intramolecular transannulation reaction of pyridotriazoles using internal alkynes en route to various fused polycyclic indolizines has been developed. For the first time it is shown that in addition to the well-established Rh- or Cu-catalyzed carbene mechanism, the transannulation reaction could also follow a Lewis acid-mediated electrophilic pathway.

Rh(ii)-catalyzed cycloadditions of 1-tosyl 1,2,3-triazoles with 2H-azirines: switchable reactivity of Rh-azavinylcarbene as [2C]- or aza-[3C]-synthon

The Rh(ii)-catalyzed formal [3+2] and [3+3] cycloadditions of 1-tosyl 1,2,3-triazoles with 2H-azirines have been developed, which enable the efficient synthesis of polysubstituted 3-amino-pyrroles and 1,2-dihydropyrazines, respectively.

Pyrrole: a resourceful small molecule in key medicinal hetero-aromatics

Pyrrole is widely known as a biologically active scaffold which possesses a diverse nature of activities.

One-pot synthesis of 2,3-disubstituted dihydrobenzofurans and benzofurans via rhodium-catalyzed intramolecular C–H insertion reaction

Intramolecular sp³ C–H insertion of α-imino carbenoid. One pot synthesis of benzofuran derivatives.

Metal-free [3+2] cycloaddition of azides with Tf2CCH2 for the regioselective preparation of elusive 4-(trifluoromethylsulfonyl)-1,2,3-triazoles

1,2-Dipole Tf₂CCH₂ is generated in situ from 2-(2-fluoro-pyridin-1-ium-1-yl)-1,1-bis[(trifluoromethyl)-sulfonyl]ethan-1-ide and immediately reacted at room temperature with azides to afford previously unknown 4-trifluoromethanesulfonyl 1,2,3-triazoles in a highly regio- and chemoselective fashion.

An efficient approach to 1,2,3-trisubstituted indole via rhodium catalyzed carbene Csp3–H bond insertion

A method for convenient synthesis of N-alkyl-2-aryl-indole-3-carbaldehyde via carbene C–H bond insertion.

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

3-Aryl-2-aminoindoles, 3-allyl-3-amino-2-iminoindolines, and tetrahydro-[1,4] diazepino[2,3-b]indoles were prepared from 3-diazoindolin-2-imines.

Rhodium-catalyzed synthesis of multi-substituted furans from N-sulfonyl-1,2,3-triazoles bearing a tethered carbonyl group

The efficient synthesis of highly functionalized furan derivatives from 1-sulfonyl-1,2,3-triazoles with a pendent carbonyl group is reported. The process involves an intramolecular trapping of α-imino carbene and subsequent aromatization.

Rhodium-catalyzed NH insertion of pyridyl carbenes derived from pyridotriazoles: a general and efficient approach to 2-picolylamines and imidazo[1,5-a]pyridines

A general and efficient NH insertion reaction of rhodium pyridyl carbenes derived from pyridotriazoles was developed. Various NH-containing compounds, including amides, anilines, enamines, and aliphatic amines, smoothly underwent the NH insertion reaction to afford 2-picolylamine derivatives. The developed transformation was further utilized in a facile one-pot synthesis of imidazo[1,5-a]pyridines.

Multicomponent [5 + 2] cycloaddition reaction for the synthesis of 1,4-diazepines: isolation and reactivity of azomethine ylides

Air-stable azomethine ylides with an unusual pattern of charge distribution were efficiently prepared via the rhodium-catalyzed reaction between pyridines and 1-sulfonyl-1,2,3-triazoles. This reaction allowed for the first example of the catalytic multicomponent [5 + 2] cycloaddition reactions, thus resulting in the formation of biologically active 1,4-diazepine compounds.

Expedient synthesis of fused azepine derivatives using a sequential rhodium(II)-catalyzed cyclopropanation/1-aza-Cope rearrangement of dienyltriazoles

A general method for the formation of fused dihydroazepine derivatives from 1-sulfonyl-1,2,3-triazoles bearing a tethered diene is reported. The process involves an intramolecular cyclopropanation of an α-imino rhodium(II) carbenoid, leading to a transient 1-imino-2-vinylcyclopropane intermediate which rapidly undergoes a 1-aza-Cope rearrangement to generate fused dihydroazepine derivatives in moderate to excellent yields. The reaction proceeds with similar efficiency on gram scale. The use of catalyst-free conditions leads to the formation of a novel [4.4.0] bicyclic heterocycle.

One-step synthesis of nitrogen-containing medium-sized rings via α-imino diazo intermediates

Eight- and 9-membered dioxazocines and dioxazonines are readily synthesized starting from N-sulfonyl-1,2,3-triazoles in a single-step procedure. A perfect regioselectivity and generally good yields (up to 92%) are obtained under dirhodium catalysis using 1,3-dioxolane and 1,3-dioxane as solvents and reagents.