Regio- and stereoselective synthesis of tetra- and triarylethenes by N-methylimidodiacetyl boron-directed palladium-catalysed three-component coupling

Abstract

The flexible synthesis of tetra-and triarylethenes bearing different aryl groups has been a long-standing challenge in organic synthesis. Here we report a palladium-catalysed syndiarylation of arylethynyl N-methyliminodiacetyl (MIDA) boronates. The products, triarylalkenyl N-methyliminodiacetyl boronates, allow a step-economic and modular synthesis of tetra-or triarylethenes via a subsequent stereospecific Suzuki-Miyaura coupling reaction or base-promoted protodeborylation, respectively. Use of the sp 3-B(MIDA) masked aryl alkyne is the key factor for success by offering an exceptionally good regioselectivity for the boronretentive coupling. The unusual regioselectivity is believed to arise from the stabilization due to the strong electron donation from the C−Pd σ bond to the p-orbital of boron in the transition state of migratory insertion. A broad range of differently substituted tetra-and triarylethenes are constructed in good yields and geometrical control. Synthetic manipulation of the C-B bond also enables the facile construction of several other types of tetra-substituted alkenes.

Regiocontrolled Allylic Functionalization of Internal Alkene via Selenium-pi-Acid Catalysis Guided by Boron Substitution

“…16 In this context, Previous studies have showcased that in certain cases, the MIDA boron moiety is by no means a bystander, but could confer interesting reactivity to the substrates. 17 For instance, independent work from Yudin 18 and us 19 uncovered an intriguing directing effect of MIDA boron in metal-catalyzed functionalized of alkenes and alkynes, respectively. This effect is attributed to a neighboring stereoelectronic stabilizing donation of electron density to boron, thanks to the hemilabile nature of the MIDA B-N dative bond.…”

Monoarylation of Diphenyldithienylethene by Ligand-Free Palladium Catalyzed C-H Activation

“…Normally, this approach gave low yields with many accompanying isomer products. Recently, there have been two efficient methodologies to construct multiarylated ethenes with high yields based either on palladium-catalyzed syn-direct diarylation of arylethynyl N-methyliminodiacetyl boronates (Lin et al, 2019) or palladium-catalyzed consequential multi-Suzuki reaction of di-, tri-and tetraboronated ethenes (Zhang et al, 2020).…”

Suzuki-Miyaura Coupling Enabled by Aryl to Vinyl 1,4-Palladium Migration

“…Therefore, Suzuki-Miyaura coupling enabled by controllable palladium migration, further expanding this important transformation and affording new chemical accessibility, is highly desirable. As a continuing effort on developing reactions via palladium migration , herein we present the first Suzuki-Miyaura coupling enabled by aryl to vinyl 1,4-palladium migration ( Figure 1B), which offered an efficient way to synthesize stereodefined, multisubstituted olefins (Gao et al, 2010;Wang, 2012;Wencel-Delord et al, 2012;Zhang et al, 2016a;Li et al, 2017;Li and Duan, 2018;Lin et al, 2019) and 1,3-dienes (Besset et al, 2011; Boultadakis-Arapinis et al, 2014; De Paolis et al, 2012; Hu et al, 2015;Liang et al, 2017;Liu et al, 2019; Siau ciulis et al, 2019). Notably, multi-aryl substituted olefins and 1,3-dienes may display interesting electronic and photonic properties owing to their p-extended systems and have been widely applied in many diverse fields, such as chemical or biological sensors, stimuli response material, and fluorescent materials ( Figure 1C) (Kong et al, 2018;Yang et al, 2014;He et al, 2019).…”