Synthesis of amines
Palladium-catalyzed reductive cross-coupling reaction of various protected allylic amine derivatives with alkylzinc reagents yields anti-Markovnikov products. Preliminary mechanistic studies suggest that a reversible β-hydride elimination/hydride insertion process furnishes the primary Pd-alkyl intermediate, which then undergoes transmetalation followed by reductive elimination.
R. J. DeLuca, M. S. Sigman, J. Am. Chem. Soc., 2011, 133, 11454-11457.
Carbamates and sulfonamides serve as directing groups in Ni-catalyzed asymmetric Suzuki reactions for cross-coupling of unactivated alkyl electrophiles. Racemic secondary bromides and chlorides undergo C-C bond formation in a stereoconvergent process in good ee at room temperature in the presence of a commercially available Ni complex and chiral ligand.
A. Wilsily, F. Tramutola, N. A. Owston, G. C. Fu, J. Am. Chem. Soc., 2012, 134, 5794-5797.
In stereoconvergent, arylamine-directed alkyl-alkyl Suzuki cross-coupling reactions, structure-enantioselectivity studies are consistent with the nitrogen, not the aromatic ring, serving as the primary site of coordination of the arylamine to the catalyst.
Z. Lu, A. Wilsily, G. C. Fu, J. Am. Chem. Soc., 2011, 133, 8154-8157.
N-heterocyclic carbene (NHC) ligands efficiently promote a palladium-catalyzed stereospecific and regioselective cross-coupling of enantiopure 2-arylaziridines with arylboronic acids under mild conditions without β-hydride elimination to construct a tertiary stereogenic center.
Y. Takeda, Y. Ikeda, A. Kuroda, S. Tanaka, S. Minataka, J. Am. Chem. Soc., 2014, 136, 8544-8547.
A cross-coupling reaction between N-sulfonyl aziridines and organozinc reagents is possible under mild and functional-group-tolerant conditions in the presence of inexpensive and air-stable Ni(II) source and dimethyl fumarate as ligand to yield β-substituted amines. The stereoselectivity of the reaction is consistent with a stereoconvergent mechanism wherein the sulfonamide directs C-C bond formation.
C.-Y. Huang, A. G. Doyle, J. Am. Chem. Soc., 2012, 134, 9541-9544.
A Ni-catalyzed Negishi cross-coupling with 1,1-disubstituted styrenyl aziridines delivers valuable β-substituted phenethylamines via a challenging reductive elimination that affords a quaternary carbon. An electron-deficient olefin ligand is crucial for achieving high rates and chemoselectivity for C-C bond formation over β-H elimination.
C.-Y. Huang, A. G. Doyle, J. Am. Chem. Soc., 2015, 137, 5638-5641.
Transition metal carbenes can directly be generated from readily available and stable 1-sulfonyl-1,2,3-triazoles in the presence of chiral Rh(II) carboxylates and can be used in a highly efficient enantioselective C-H insertion of azavinyl carbenes into unactivated alkanes to access various β-chiral sulfonamides.
S. Chuprakov, J. A. Malik, M. Zibinsky, V. V. Fokin, J. Am. Chem. Soc., 2011, 133, 10352-10355.