Pavel B. Dzhevakov et al.
UPDATES
lation of the crude products was performed. The de- transferred to a preheated oil bath (1108C). After 12 h, re-
action mixture was cooled, dissolved in CH Cl -H O mixture
veloped protocols meet the demands of “green”
chemistry. Calculated E-factors are low: 1.91 and 3.88,
respectively. for Miyaura borylation and one-pot, two-
step homocoupling.
In conclusion, we have shown for the first time that
aryl bromides and chlorides can be coupled with
bis(pinacolato)diboron giving good to excellent yields
of pinacol arylboronates under solvent-free condi-
tions. Aryl halides can be homocoupled in a one-pot,
2
2
2
(1:1), the organic phase separated, the solvent evaporated
under vacuum and the product isolated by flash chromatog-
raphy on silica gel by elution with hexane:ethyl acetate=
7
:1.
Acknowledgements
two-step process under similar conditions giving sym- The reported study was partially supported by RFBR, re-
metrical biaryls in high yields.
search project No. 13-03-1224013 ofi m.
The optimal source of palladium for a solvent-free
Miyaura borylation is Pd(dba) , while Pd(OAc) per-
2
2
forms better in the one-pot, two-step homocoupling.
Reactions of aryl bromides are catalyzed more effi-
ciently using DPEphos ligands. For aryl chlorides,
XPhos is the ligand of choice.
References
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Experimental Section
General Procedure for Solvent-Free Miyaura
Borylation
A screwcap vial equipped with magnetic stir bar was
charged with 1 mmol of aryl halide, 1.2 mmol of B Pin ,
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2
2
2
separated, the solvent evaporated under vacuum and the
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0
3
.03 mmol of palladium acetate, 0.06 mmol of ligand and
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Adv. Synth. Catal. 2016, 358, 977 – 983