Stereoselective Cross-Coupling Reaction of 2,4-Diaryl-1,1-diboryl-1,3-butadienes: Stereocontrolled Approach to 1,3,4,6-Tetraarylated 1,3,5-Hexatrienes

Abstract

The boryl group cis to the C(3)=C(4) group in 2,4-aryl-1,1-bis(pinacolatoboryl)-1,3-butadienes undergoes Pd-catalyzed cross-coupling reaction with aryl iodides stereoselectively at room temperature, giving rise to the corresponding boronates as a single diastereomer. Subsequent coupling of the boronates with alkenyl iodides allows us to synthesize 1,3,4,6-tetraarylated 1,3,5-hexatrienes stereoselectively.

Synthesis of Multisubstituted Olefins through Regio‐ and Stereoselective Addition of Interelement Compounds Having B–Si, B–B, and Cl–S Bonds to Alkynes, and Subsequent Cross‐Couplings

“…The observed chemoselectivity is consistent with that reported by Shimizu and Hiyama:74 C–C bond formation at the cis position of the alkyl groups was observed in the reaction of 1,1‐diboryl‐1‐alkene with aryl iodides. The C–C bond at the cis position of the SiMe 2 Ph group formed with discrimination between the two geminal boryl groups in 3 .…”

“…Since functional materials, natural products, and bioactive pharmaceuticals have all been synthesized with 1,1‐diborylated olefins,72–76 compound 3 was successively subjected to Suzuki–Miyaura coupling with equimolar iodobenzene ( 4a ) to ascertain whether the arylation is chemoselective. Various palladium catalysts and ligands were screened and the results are listed in Table .…”

Stereoselective Synthesis of Trisubstituted Alkenes via Cobalt-Catalyzed Double Dehydrogenative Borylations of 1-Alkenes

“…While many methods are available for the synthesis of monoborylalkenes, there are limited approaches to 1,1-diborylalkenes. ,, Traditional routes to the latter involve the use of reactive lithium reagents, which may pose a challenge in reactions with sensitive functional groups. − Recently, several catalytic methods have been developed for the synthesis of 1,1-diborylalkenes using alkynes as the starting materials (Scheme a). In 2015, Sawamura and Ohmiya reported the preparation of 1,1-diborylalkenes by LiO t Bu-catalyzed reactions of propiolates, propiolamides, and 2-ethynylazoles with B 2 pin 2 .…”

Polyborylated reagents for modern organic synthesis

“…Aryl and alkenyl-substituted diborylethenes also react stereoselectively with aryl and alkenyl iodides, providing stereocontrolled route to polyfunctional 1,3,5-hexatrienes. 30 ) Thus, 2,4-diaryl-1,1-diboryl-1,3-butadienes couple with aryl iodides in the presence of a Pd catalyst at the boryl group cis to the C(3)=C(4) group and the corresponding mono-coupled products are obtained as a single stereoisomer as illustrated in Scheme 17 . Subsequent coupling reaction of the boronates with ( E )-alkenyl iodides gives 1,3,4,6-tetraaryl-1 E ,3 E ,5 E -hexatrienes that exhibit aggregation-induced emission upon photo-excitation and thus may find application to light-emitting materials.…”