Enantioselective Copper-Catalyzed sp²/sp³ Diborylation of 1-Chloro-1-Trifluoromethylalkenes

Abstract

Fluorine-containing organoboron compounds have emerged as novel building blocks in chemical synthesis; among them, fluorinated sp2/sp3 diborylated compounds are particularly appealing, since they might undergo chemoselective and diversified transformations of different C–B bonds with fluorinated functionality, thus bringing versatility and complexity to the eventual products. However, expedient, synthetic strategies for the construction of such fluorinated diborylative compounds are very sparse. Herein, we disclose enantioselective Cu-catalyzed sp2/sp3 diborylations of 1-chloro-1-trifluoromethylalkenes, leading to diborylated compounds bearing a gem-difluoroalkenyl moiety; most intriguingly, the new formed C–B bonds include one stereoselective and optically pure Csp3–B bond. Further transformations on the eventual products demonstrated the values of our presented strategy.

Synthesis of Z-gem-Cl,CF3-Substituted Alkenes by Stereoselective Cross-Metathesis and the Role of Disubstituted Mo Alkylidenes

“…There is also the possibility of catalytic regio- and enantioselective boryl substitution (Scheme b) . The conversion of 3e to tetrasubstituted allylic boronate 5 is representative (63% yield, 91:9 er (enantiomeric ratio)) …”

“…29 The conversion of 3e to tetrasubstituted allylic boronate 5 is representative (63% yield, 91:9 er (enantiomeric ratio)). 30 2.5. Spectroscopic Detection of Cl,CF 3 -Disubstituted Mo Alkylidenes.…”

Recent Advances in Catalytic Asymmetric Synthesis of Chiral 1,2-Bis(boronic) Esters

“…Recently, Song and coworkers [33] developed a method for the enantioselective Cu-catalyzed diborylation of alkenes, producing fluorine-containing chiral 1,2-bis(boronic) esters. This process produces molecules that contains both fluorine and boron, offering more options for complex and diversified structural modifications.…”

Transition-metal-catalyzed asymmetric defluorinative reactions

“…Afterwards, a copper-catalyzed defluorinative diborylation reaction for the efficient construction of two different types of C–B bonds, especially with one optically pure C(sp 3 )–B bond, was successfully developed by Song et al (Scheme 8A). 29 When a chlorine atom or a triflate substituent was pre-installed at the β-position of trifluoromethylalkenes, sp 2 /sp 3 diborylation occurred smoothly, leading to the production of chiral allylic boronates bearing both boron and fluorine substituents together with a gem -difluoroalkenyl functionality. Various unactivated aliphatic and (hetero)aromatic-substituted 1-chloro-1-trifluoromethylalkenes were compatible with this transformation and gave satisfactory to excellent reaction outcomes (Scheme 8B).…”