We report a regiodivergent and stereoselective hydroboration of 1,3-diynes with pinacolborane (HBpin) in the presence of cobalt catalysts generated in situ from bench-stable Co(acac) 2 and bisphosphine ligands. These cobalt catalysts were activated by the reactions with HBpin. A range of unsymmetrical and symmetrical 1,3-diynes reacted smoothly with HBpin in the presence of Co(acac) 2 /xantphos to selectively afford enynylboronate products with boron addition to the internal carbon of the 1,3-diyne unit. However, these 1,3-diynes reacted in the presence of Co(acac) 2 /dppf to form enynylboronate products with boron addition to the external carbon of the 1,3-diyne unit. These hydroboration reactions show good functional group compatibility and can be readily scaled up to gram-scales without using a drybox. Deuterium-labeling experiments suggest a cis-addition of HBpin to the less-hindered triple bond of 1,3-diynes. Furthermore, the comparison of the regioselectivity between cobalt-catalyzed hydrosilylation and hydroboration reactions of the same 1,3-diyne substrate suggests that Co(acac) 2 /xantphos-catalyzed regioselective 1,3-diyne hydroboration proceeds through a cobalt-hydride intermediate while Co(acac) 2 /dppf-catalyzed 1,3-diyne hydroboration proceed through a cobalt boryl intermediate.
A regio- and stereoselective
hydrosilylation of 1,3-diynes has
been developed relying on catalysts generated from bench-stable Co(acac)2 and dppp ligand. A variety of symmetrical and unsymmetrical
1,3-diynes undergo this transformation, yielding the corresponding
silyl-functionalized 1,3-enynes in high yields with excellent regioselectivity.
Gram-scale reactions and further transformations of the silyl-containing
1,3-enyne products highlight the synthetic utilities of this Co-catalyzed
hydrosilylation of 1,3-diynes.
The first transition metal-catalyzed stereoconvergent Markovnikov 1,2-hydrosilylation of (E/Z)-dienes was effectively achieved with excellent E-selectivities using a cobalt catalyst.
A wide range of functionalized 1,3-enynes undergo hydroboration with pinacolborane to produce enantiomerically enriched allenylboronates in the presence of a chiral copper catalyst.
An asymmetric copper‐catalyzed alkylation of quinoline N‐oxides with chiral Cu–alkyl species, generated by migratory insertion of a vinylarene into a chiral Cu−H complex, is reported. A variety of quinoline N‐oxides and vinylarenes underwent this Cu‐catalyzed enantioselective alkylation reaction, affording the corresponding chiral alkylated N‐heteroarenes in high yield with high‐to‐excellent enantioselectivity. This enantioselective protocol represents the first general and practical approach to access a wide range of chiral alkylated quinolines.
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