Design and synthesis of a tridentate ligand inspired by the phenomenon of self-assembly catalysis and its application in the asymmetric alkynylation of N-(diphenylphosphinoyl) imines

Catalytic Asymmetric Addition of Alkyl and Aryl Alkynes to N-(Diphenylphosphinoyl)imines

“…Among the imine substrates studied in the asymmetric alkyne additions to generate propargyl amines, the use of N -(diphenylphosphinoyl)­imines is particularly interesting because the N -diphenylphosphinoyl activating/protecting group can be easily removed under very mild conditions after the reaction. − For example, when a methanol solution of an optically active N -(diphenylphosphinoyl) propargyl amine was treated with aqueous HCl at room temperature for 2 h, the resulting propargyl amine was obtained in 92% yield with retention of the enantiomeric purity . Several reports have appeared for the catalytic asymmetric alkyne addition to the N -(di­phenyl­phos­phinoyl)­imines, high enantioselectivity has been observed for certain substrates, but there are still limitations in these methods. , For example, no highly enantioselective reaction of N -(diphenylphosphinoyl)­imines with simple alkyl alkynes was reported, although good results have been obtained for the additions of alkynes with aryl, TMSOCH 2 , TMS, or 2-propenyl groups. , As shown in Scheme , although the 1,1′-bi-2-naphthol (BINOL) compound ( R )- 1 showed high enantioselectivity for the reaction of aryl alkynes with N -(diphenylphosphinoyl)­imines, it gave only 14% ee and 22% yield for the reaction of 1-hexyne with N -(diphenyl­phosphinoyl)­benzaldimine ( 2 ) …”