Chiral formamide ligand

In 2007 Kocovsky and Malkov reported an alternative organocatalytic approach, taking advantage of trichlorosilane in combination with a chiral formamide ligand (now referred to as Sigamide) for chloroamine formation (Scheme 7.6) and subse quent conversion to highly enantioenriched aziridines (not shown) [21]. 

Recently QU1NAP was used as the chiral ligand to alkylate the allyl acetate 18. The enantioselectivity is enhanced by the addition of the crown ether 15-crown-5, but the enantiomeric excess is still moderate (up to 47 % ee)S9. The diphenyl phosphinoaryloxazoline ligand 20 exhibits best enantioselectivities for these substrates and demonstrates its broad versatility for the enantiose-lective alkylation of allyl acetates. Almost complete chirality transfer is achieved77 (for a detailed discussion see the section entitled meso-Tt-Allylpalladium Complexes). Dimethyl-formamide and tetrahydrofuran serve equally well as solvents, but with the latter solubility problems may arise. Higher temperature enhances reactivity at the expense ot selectivity (at 80 °C 65% ee). 

Bearing this idea in mind, the authors synthesized a class of chiral diaminophosphine oxide ligands and tested them in the Ni-catalyzed intramolecular asymmetric hydrocarbamoylation reactions of formamides 38 with AlMCa as the other metal catalyst (Scheme 8.18). The combination of [Ni(cod)2] and (i ,i )-L3 gave the optimal catalytic activity. Substrates with various substitution patterns were converted smoothly to their corresponding pyrrolidinones 39 in up to 98% yield and 95% ee under very mild conditions. 

The new complex (166), generated from the corresponding diaminophosphine oxide and Mc3 Al, has been employed as a chiral ligand for the Ni(0)-catalysed C-H activation of A-homoallyl formamide (163), which provides pyrrolidones (165) via intramolecular hydrocarbamoylation (164) in <94%... 

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