Copper‐Catalyzed Radical Silylarylation of Ynones with Silanes: En Route to Silyl‐Functionalized Indenones

Abstract

A copper‐catalyzed radical silylarylation of ynones with commercially available silanes using DCP (dicumyl peroxide) as an efficient oxidant has been developed. This approach represents an efficient route to silyl‐functionalized indenone derivatives in moderate to good yield. The resulting silyl‐functionalized structures hold potential for further post‐modification to construct complex target molecules. This protocol is distinguished by its excellent selectivity, gram scale‐up ability and broad scope as well as readily available starting materials.magnified image

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

“…As a brief summary, similar annulations of ynones with alkanes,[3c] BrCF 2 CO 2 Et,[3b], [3c] R 3 SiH,[8a] HPO(OMe) 2 ,[10b] ArSH,[12h] RSO 2 H,[12c] and AgSCF 3 [12e] were presented in Scheme . The addition afforded radical intermediate 3.1 , then subsequent cyclization and dehydrogenation gave indenone derivatives 3.2 .…”

“…The addition afforded radical intermediate 3.1 , then subsequent cyclization and dehydrogenation gave indenone derivatives 3.2 . Both metal‐catalyzed[3b], [3c], [8a], [10b] and metal‐free methodologies[3a], [12c], [12e], [12h] have been developed in this decade. An oxidation or photoreaction condition was usually required (Scheme ).…”

“…In the presence of CuCl and DCP (dicumyl peroxide, as oxidant), radical annulations of ynones with R 3 SiH[8a] afforded silyl‐functionalized indenones 12.2 (Eq. 12‐1).…”

Synthesis of Indenones via Palladium‐Catalyzed Ligand‐Free Carbonylation

“…[12] However, most of starting substrates of intramolecular cyclization were not readily commercially available and therefore suffered from multiple-step syntheses or narrow substrate scopes. Up to now, researches of efficient methods for preparation of indenones mainly have focused on two-component annulation, including transition-metal-mediated cyclization, [3,[5][6][7][8][9] radical cyclization, [11] Friedel-Crafts-type cyclization [4] and so on. Among them, the preferred strategies are Rh [9] or Pd [7] catalyzed annulation of alkynes with orthofunctionalized arenes (Scheme 1, a), which are usually time-requiring multiple functional transformation and thus less efficiency in a synthetic sequence.…”

“…Indenones, widely existing in natural products and synthetically bioactive molecules, [1] have attracted considerable synthetic interests and a number of methods have been developed including intramolecular cyclization, [2] two-component annulation [3][4][5][6][7][8][9][10][11] and a few examples of three-component annulation. [12] However, most of starting substrates of intramolecular cyclization were not readily commercially available and therefore suffered from multiple-step syntheses or narrow substrate scopes.…”