An efficient method for the enantioselective construction of tertiary C-O bond via asymmetric allylic substitution of racemic vinylethylene carbonates with water and alcohols has been developed. Under the cooperative catalysis system of an in situ generated chiral palladium complex and boron reagent in mild conditions, the process allowed rapid access to valuable tertiary alcohols and ethers in high yields with complete regioselectivities and high enantioselectivities. This protocol represented the first example of direct enantioselective formation of a tertiary C-O bond with water as an oxygen donor. The synthetic utilities of the process have been demonstrated by the elaboration of the products into key intermediates of biologically relevant agents, and chiral tertiary cyclic ethers could also be provided through the sequential reactions of the allylic etherification and ring-closing metathesis.
An efficient method for the construction of furanobenzodihydropyran skeletons has been developed through Pd-catalyzed asymmetric decarboxylative cycloaddition of vinylethylene carbonates with 3-cyanochromones. By using a palladium complex generated in situ from [Pd2(dba)3]·CHCl3 and phosphoramidite L3 as a catalyst under mild reaction conditions, the process afforded furanobenzodihydropyrans bearing vicinal quaternary stereocenters in high yields with good to high enantio- and diastereoselectivities.
Pd-catalyzed regio- and enantioselective allylic etherification
of vinylethylene carbonates (VECs) with diols has been developed.
By using cooperative catalysts of the chiral palladium complex and
triethylborane in mild conditions, the process gave monoetherified
and bisetherified polyglycol derivatives with tetrasubstituted stereocenters
in high yields with complete regioselectivities and high levels of
enantio- and diastereoselectivities.
A useful method for the enantioselective preparation of isoxazoline N-oxides via Pd-catalyzed asymmetric allylic cycloaddition of nitro-containing allylic carbonates has been developed. By using palladium complex in situ generated from Pd 2 (dba) 3 •CHCl 3 and phosphoramidite L2 as a catalyst under mild conditions, the transformation afforded vinylated isoxazoline N-oxides in high yields with acceptably high enantioselectivities.
Herein, a practical and efficient approach to tetrahydrofurans with three-stereocenters has been developed through Pd-catalyzed asymmetric allylic cycloaddition of vinylethylene carbonates (VECs) with 2-nitroacrylates under mild conditions. By using this...
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