Merging base-promoted C–C bond cleavage and iron-catalyzed skeletal rearrangement involving C–C/C–H bond activation: synthesis of highly functionalized carbazoles

Abstract

An efficient and atom-economical methodology for the synthesis of multi-substituted carbazoles starting from α-aryl ketones and ynones under mild reaction conditions has been developed. This process goes through Cs2CO3 promoted C-C σ-bond activation of α-aryl ketones followed by highly selective C-H bond activations and C-C bond fragmentations in a one-pot operation.

Ynones in Reflex‐Michael Addition, CuAAC, and Cycloaddition, as Well as their Use as Nucleophilic Enols, Electrophilic Ketones, and Allenic Precursors

“…Several applications of in situ generated allenic intermediates 35.1 from addition of functional active methylenes have been developed in this decade. As shown in Scheme , the Li group made a lot of innovations, which mainly based on a nucleophilic addition 35.2 /ring‐opening 35.3 mechanism (Scheme ).…”

“…In 2018, the Li group[18a] achieved the synthesis of carbazoles 36.4 via reactions of α‐aryl ketones with ynones (Eq. 36‐1).…”

“…37‐1). [18b] On the other hand, combined with ZnI 2 and K 2 S 2 O 8 , a further cycloaddition 37.6 could be achieved via C–H functionalization toward indoles (Eq. 37‐2).…”

“…37‐2). [18b] During the one‐pot process, an iminium ion intermediate 37.2 might be generated. Then, the attack of OH group afforded spiro intermediate 37.3, which underwent the cyclization, ring‐opening 37.4 and oxidation 37.5 to give final products (Scheme ).…”

“…In 2018, the Li group[18c] explored the annulation of indene‐1,3‐dione with ynones for the preparation of seven‐membered rings 38.5 (Eq. 38‐1).…”