Selective Dehydrogenative Mono- or Diborylation of Styrenes by Supported Copper Catalysts

Abstract

The selective dehydrogenative borylation of alkenes is an attractive method for synthesizing useful borylalkenes. However, very few catalytic systems have been reported that fulfill this objective. All the reported examples are homogeneous catalysts with special ligands requiring the usage of bases. This study describes the heterogeneously catalyzed dehydrogenative borylation by supported copper hydroxide catalysts (Cu­(OH) x /support). In the presence of Cu­(OH) x /support and suitable ketones, the dehydrogenative borylation of styrenes with bis­(pinacolato)­diboron efficiently proceeded to selectively afford the corresponding β-monoboryl- or β,β-diborylstyrenes. The observed catalysis was truly heterogeneous, and the catalysts could be reused several times, though their catalytic performance gradually declined.

H2‐Acceptorless Dehydrogenative Boration and Transfer Boration of Alkenes Enabled by Zirconium Catalyst

“…Recently, an iron‐catalyzed dehydrogenative boration was reported, in which 2 equivalents of norbornene were required . Thus, in order to avoid the hydroboration reactivity of borane, diborane was introduced, but still in some cases ketone or alcohol was required as the HBpin scavenger (generated from B 2 pin 2 )– (Scheme b). Consequently, a mild, efficient, and direct catalytic H 2 ‐acceptorless dehydrogenative boration of alkenes with borane remains underdeveloped.…”

α,β-Enone Borylation by Bis(Pinacolato)Diboron Catalyzed by Cu3(BTC)2 Using Cesium Carbonate as a Base

“…In another precedent, the dehydrogenative borylation of styrene with B 2 pin 2 was reported by copper hydroxide supported over CeO 2 or Al 2 O 3 . The product selectivity was determined by the appropriate choice of a suitable ketone and support [52]. Recently, the borylation of alkyl bromides and chlorides using B 2 pin 2 was reported with Cu/Pd alloy nanoparticles supported over graphene under photocatalytic conditions [53].…”

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

“…Encouraged by the above success in preparing trisubstituted olefins, we envision that the coupling reaction with arylethenyl boron reagents would lead to the generation of stereodefined multisubstituted 1,3-dienes. A number of arylethenyl boron reagents are commercially available, and several stereoselective synthetic methods were developed, which laid a firm base for this strategy (Yoshii et al, 2019). The optimized conditions used in the above coupling with arylboronate esters were also suitable for the arylethenyl boron esters.…”