Intermolecular [5+2] Annulation between 1‐Indanones and Internal Alkynes by Rhodium‐Catalyzed C–C Activation

Abstract

Herein, we report a[ 5 + +2] cycloaddition between readily accessible 1-indanones and internal alkynes through Rh-catalyzed activation of less strained CÀCb onds.T he reaction is enabled by as trongly s-donating NHC ligand and ac arefully modified temporary directing group.Awide range of functional groups is tolerated, and the method provides straightforwarda ccess to diverse benzocycloheptenones that are hard to access otherwise.D FT studies of the reaction mechanism imply the migration insertion as the turnoverlimiting step and suggest beneficial p-p interactions in the transition states. Scheme 1. [5+ +2] reactions for constructingseven-membered carbocycles.

Annulations involving 1-indanones to access fused- and spiro frameworks

“…In 2021, the same author synthesized similar type of ring expansion products employing internal alkynes as the reaction partner. 32 In fact, alkynes have better affinity with transition metals compared to alkenes due to smaller HOMO/LUMO gap, thereby facilitating the 2π-insertion process. The intermolecular [5+2] cycloaddition reaction between indanones 1 and internal alkynes 4 proceeded via the Rh-catalyzed C–C activation resulting richly decorated benzocycloheptenones 5 in moderate to good yields.…”

Facile Generation of Fused Seven-Membered Polycyclic Systems via Ring Expansion and Application to the Total Synthesis of Sesquiterpenoids

“…[29][30][31][32] Very recently, Dong and co-workers reported a straightforward and distinct approach for accessing benzene-fused scaffolds between 1-indanones and ethylene gas or internal alkynes via intermolecular reactions (Scheme 1b). 33,34 Although these strategies have undoubtedly made a significant progress, the requirement of expensive noble metal rhodium, high temperature, high-pressure ethylene gas, and the limited scope of substrates, have severely hindered the application of these methodologies to the construction of highly complex and multi-functionalized structures.…”

Rapid syntheses of N-fused heterocycles via acyl-transfer in heteroaryl ketones

“…For unstrained ketones [27][28][29][30][31][32] , the most common strategy involves using directing groups to form of a stable chelate (Fig. 1c) [33][34][35][36][37][38][39][40] . Although effective, the use of directing groups complicates the overall synthesis and limits the scope of the accessible products.…”