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

A highly selective cobalt-catalyzed single and double dehydrogenative borylations (DHBs) of terminal alkenes have been developed for the synthesis of <i>trans</i>-monoborylalkenes and diborylalkenes, respectively. While the cobalt-catalyzed double DHBs of aryl 1-alkenes with 2 equiv of bis­(pinacolato)­diboron (B₂pin₂) in the presence of 1 equiv of CsF in DMF produce 1,1-diborylalkenes selectively, the double DHBs with alkyl 1-alkenes generate <i>cis-</i>1,2-diborylalkenes in a selective manner. The 1,1-diborylalkene products are further applied to stepwise and stereospecific cross-couplings with aryl halides to create trisubstituted alkenes, including triaryl alkenes

Cobalt-Catalyzed Borylation of Aryl Halides and Pseudohalides

We report the first Co-catalyzed borylation of aryl halides and pseudohalides with bis­(pinacolato)­diboron (B₂pin₂). The synthesis of two new Co­(II) complexes of oxazolinylferrocenylphosphine ligands is described. Upon activation with LiMe, the Co complex catalyzes the borylation reactions of aryl bromides, iodides, sulfonates, arenediazonium salts, and even aryl chlorides under mild conditions, providing the borylated products in excellent to moderate yields and with high functional group tolerance