Iridium-Catalyzed [2+2+2] Cycloaddition of α,ω-Diynes with Isocyanates
作者:Gen Onodera、Mari Suto、Ryo Takeuchi
DOI:10.1021/jo202083z
日期:2012.1.20
This regioselectivity could be explained by the reaction of iridacyclopentadiene with a nitrogen–carbon double bond. The regioselectivity of the reaction of malonate-derived diyne was controlled by a steric effect, while that of the reaction of ester-tethered diyne was controlled by an electronic effect. [Ir(cod)Cl]2/chiral diphosphine catalyst could be used for the enantioselective synthesis of C–N
Enantioenriched N-aryl-2-pyridones with axially chiral C-N bonds were prepared by a cationic rhodium(I)-BINAP or tol-BINAP-catalyzed enantioselective [2+2+2] cycloaddition of alkynes with ortho-substituted phenyl isocyanates.
cationic Rh(I)-catalyzed [2+2+2] cycloaddition reactions between diynes and isocyanates relying on the chiral anion strategy have been devised. In the presence of [Rh(cod)Cl]2, 1,4-bis(diphenylphosphino)butane, and the silver phosphate salt Ag(S)-TRIP as the unique source of chirality, axially chiral pyridones were isolated with ees up to 82%. This approach is novel in the field of chiral anion-mediated
The first enantioselective metal-catalyzed [2 + 2 + 2] cycloaddition involving a double asymmetric induction has been devised. It relies on the use of an in situ generated chiral cationic rhodium(I) catalyst with a matched chiral ligand/chiral counterion pair. Careful optimization of the catalytic system, as well as of the reaction conditions, led to atroposelective [2 + 2 + 2] pyridone cycloadducts with high ees up to 96%. This strategy outperformed those previously described involving a chiral ligand only or a chiral counterion only.