Synthesis of Tetrahydrocarbazol-4-ones via Rh(III)-Catalyzed C–H Activation/Annulation of Arylhydrazines with Iodonium Ylides

Abstract

The rhodium­(III)-catalyzed C–H activation followed by intramolecular annulation reactions between arylhydrazines and iodonium ylides under suitable conditions has been described. Tetrahydrocarbazol-4-ones are readily achieved with moderate to excellent yields. The synthetic protocol features a wide range of substrates with high functional group tolerance. The gram-scale reaction and derivatization of the product demonstrate the synthetic practicality and utilization of this method.

Nitrene C−H Bond Insertion Approach to Carbazolones and Indolones, and a Reactivity Departure for 7‐Membered Analogues**

“…[29] In relation to this work, Rh and Ru catalysts have recently been investigated and most of these address general syntheses of carbazolones (Scheme 1). [30][31][32][33][34][35][36][37] Of these, three provide access to compounds without an N-substituent. [35][36][37] Further, only two approaches seem amenable to the synthesis of N-methylindolone [34] and indolone.…”

Iodonium ylides: an emerging and alternative carbene precursor for C–H functionalizations

“…19,20 As illustrated in Scheme 8, sequential C-H activation and coordination of iodonium ylides followed by extrusion of aryl iodide generated the Rh carbenoid intermediate (29). Subsequent migratory insertion followed by proto-demetallation yielded the alkenylation product (31). Eventually, intermediate 31 underwent intramolecular nucleophilic addition/ cyclization by the subsequent loss of Corey-Chaykovsky reagent (sulfoxonium methylide) to deliver the desired product (19).…”

“…and synthetic transformations of the desired product demonstrated the synthetic practicality and utilization of this method (Scheme 22). 31 The authors also conveyed a possible reaction mechanism for the reaction, which is depicted in Scheme 23. Initially, the precatalyst [Cp*RhCl 2 ] 2 forms an active catalyst [Cp*Rh(OAc) 2 ] (86) with treatment with the additive AgOAc.…”

“…Additionally, the gram-scale reaction and synthetic transformations of the desired product demonstrated the synthetic practicality and utilization of this method (Scheme 22). 31…”

Regio- and diastereoselective synthesis of diverse spirocyclic indenes by cyclization with indene-dienes as two carbon building blocks

“…Recently, an ortho-hydroxyphenyl-substituted para-quinone methide ( p-QM) derivative has emerged as a suitable and promising synthetic reactant in the cyclization to construct spirocyclic compounds, and shows powerful nucleophilic-electrophilic reactivities. [21][22][23][24][25] Many elegant methodologies have been disclosed for the cyclization using p-QM derivatives as four-atom and two-atom units to produce polycyclic compounds, including (4 + n) [26][27][28][29][30][31][32][33][34] and (2 + n) 22,[35][36][37] cyclization and 1,6-addition reactions to generate important molecules. [38][39][40][41][42] On the basis of these outstanding investigations, it has been proved that a p-QM derivative is a sterling four-atom building block in the cyclization to access oxygenheterocycles which are core heterocyclic motifs in a wide range of natural products, pharmaceuticals and bioactive compounds.…”