Palladium-Catalyzed Asymmetric Allylic C-H Functionalization Reactions

Palladium catalyzed allylic C-H functionalization is one of the most important tools that directly uses cheap alkenes as allylating reagents for the formation of carbon-carbon and carbon-heteroatom bonds in organic chemistry.Both stereo-and regioselectivities can be partially controlled by the variation of either chiral ligand or the substrates,providing an efficient entry to biologically active structures and key intermediates for the synthesis of natural products.The research theme of this thesis focuses on challenging issues in the control of selectivity in palladium-catalyzed asymmetric allylic C-H alkylations with different carbon nucleophiles.First,a palladium-catalyzed asymmetric allylic C-H alkylation reaction of 1.4-dienes with 5H-thiazol-4-ones has been established.This protocol features mild reaction conditions,the high yields,and excellent enantioselectivities for either linear or branched product.The regioselectivity depends on the structure of the 5H-Thiazol-4-ones.Moreover,this protocol can be applied to the synthesis of highly enantioenriched thiols,thioethers and 5-alkylated thiazolidinones derivatives.Second,a highly regio-and enantioselective allylic C-H alkylation reaction of allyl ethers with 2-acylimidazoles was developed by chiral phosphoramidite-palladium catalysis.This protocol can be applied to the synthesis of chiral ?-hydroxy-?,?-unsaturated carbonyl derivatives in moderate to high yields and with high levels of enantioselectivity,providing a highly efficient concise asymmetric synthesis of chiral tachykinin receptor antagonists,which shows the importance for application in biopharmaceutical synthesis.At last,we have developed asymmetric allylic C-H alkylation of 1,4-pentadienes with glycine Schiff bases by chiral palladium-phosphoramidite catalysis.The reaction features mild reaction conditions and tolerates broad substrates scope,providing chiral?-disubstituted ?-amino acid derivatives in moderate to high yields and with high levels of regio-,Z/E-,diastereo-and enantioselectivities.Meanwhile,this protocol can be applied to asymmetric synthesis of potential intermediate toward the natural product indazolidine 223V.