Copper(I)-catalyzed Stereoselective Silylative Dearomatization of Indoles and Pyrroles Using Silylboronates

Abstract

Silylative dearomatizations of indole-2-carboxylates were accomplished using a copper(I) catalyst and silylboronates. This reaction presumably proceeds through regioselective addition of silylcopper(I) species to indole substrates followed by highly diastereoselective protonation of the resulting copper(I) enolate intermediates to afford the corresponding dearomative silylation products. The first silylative dearomatization of pyrroles using the developed catalytic system is also described.

Development of a New Methodology for Dearomative Borylation of Coumarins and Chromenes and Its Applications to Synthesize Boron-Containing Retinoids

“…On the basis of the literature, a mechanism was also proposed for this copper(I)-catalyzed dearomative borylation of oxacycles (Scheme 6) [33][34][35][36][37]…”

“…Proposed Mechanism of Dearomative Borylation of OxacyclesOn the basis of the literature, a mechanism was also proposed for this copper(I)catalyzed dearomative borylation of oxacycles (Scheme[33][34][35][36][37]. In the first step, Cu(I)Cl would react with base (NaO t Bu) and ligand (L) to generate the active catalyst A, which subsequently would transfer B 2 pin 2 onto the Cu(I) center to form intermediate B.…”

Recent advances in the dearomative functionalisation of heteroarenes

“…19 Scheme 15 C-3 silylation of indoles using copper catalysis. 20 Scheme 16 Enantioselective transient C-3 borylation of pyrroles allows the formation of 5-functionalised dihydropyrrole derivatives. 21 Scheme 13 Enantioselective silylation of C-3 substituted indoles through NHC-copper catalysis.…”

“…In the first example shown ( Scheme 15 ) addition at C-3 was enabled by the same mechanistic principles as discussed earlier. 20 Thus, by placing an electron-withdrawing group at C-2 the natural polarity profile of the pyrrole/indole nucleus was reversed and nucleophilic attack of the silyl species at C-3 was achieved in excellent yield and with good overall selectivity for the trans products 49.…”

KOtBu-Catalyzed 1,2-Silaboration of N-Heteroarenes to Access 2-Silylheterocycles: A Cooperative Model for the Regioselectivity

“…Transformative functionalization of prevalent heteroarenes is an attractive strategy to access valuable synthons with the original heterocyclic skeletons having high synthetic and medicinal utility. − Among various functionalities being able to be installed into the heteroaromatics, a silyl group offers special benefits in that it can serve either as a versatile intermediate for further oxidative conversions or as a robust final-stage motif in pharmaceutical, material, and polymer science. − In this context, a number of site-selective silylation transformations of heteroarenes were developed by employing readily available silyl sources such as hydrosilanes, − silylboranes, − or silyl cations. , In this line, transition-metal-catalyzed C–H silylation offers an attractive route to silylated compounds.…”