Nucleophilicity parameters for designing transition metal-free C–C bond forming reactions of organoboron compounds

Enantiospecific sp2–sp3 coupling of secondary and tertiary boronic esters

“…The boronate moiety is also a strong donating group 49 In conclusion, we have discovered a general method for coupling electron rich aromatic and heteroaromatic compounds with enantioenriched secondary and tertiary boronic esters for the first time. The reaction involves initial formation of a boronate complex followed by activation of the electron rich aromatic moiety by an electrophile (NBS), which triggers a stereospecific 1,2-migration and subsequent elimination/rearomatisation.…”

Stereoselective Direct Chlorination of Alkenyl MIDA Boronates: Divergent Synthesis of E and Z α‐Chloroalkenyl Boronates

“…[13] To realize such ap rocess,h owever,t he following potential challenges must be addressed. [15] 2) Unselective alkene halogenation may result in the formation of different regioisomers and stereoisomers,a nd thus render the reaction unproductive.H erein, we report on our realization of astereodivergent synthesis of [14] With respect to this challenge,w en ote that the attenuated nucleophilicity of the C À B(MIDA) bond can be expected to make this process less likely for both electronic and steric reasons.…”

State‐of‐the‐Art in Metal‐Catalyzed Cross‐Coupling Reactions of Organoboron Compounds with Organic Electrophiles

“…Under the optimized conditions with a catalytic amount of Pd(OAc) 2 and JohnPhos 21 (Scheme 2.4), various aryl bromides, chlorides, and triflates were reacted with triolborates at room temperature. These triolborate salts have also been reacted with different cross-coupling partners for the syntheses of tetra-ortho-substituted biaryls, heteroaromatics, and polyarenes [29]. Lastly, Buchwald and coworkers have recently synthesized various 2-pyridyl triisopropoxyborate salts and utilized them in cross-coupling reactions.…”

“…According to various cross-coupling reactions published by the group [28] and a nucleophilicity study conducted by the Mayr group[29], these triolborates are extremely nucleophilic, allowing various Suzuki-Miyaura crosscoupling reactions to be conducted in milder conditions without the need for a base. On the basis of the kinetic study from the Mayr group, the nucleophilicity of 2-furanyl triolborate 44 is comparable to that of silyl enol ether 45 Scheme 2.7 Adjusting the nucleophilicity of the organoboron reagents.…”