Amides are synthesized directly from alcohols and amines in high yields using an in situ generated catalyst from easily available ruthenium complexes such as the (p-cymene, an N-heterocyclic carbene (NHC) ligand, and a nitrogen containing L-type ligand such as acetonitrile. The phosphine-free catalyst systems showed improved or comparable activity compared to previous phosphine-based catalytic systems. The in situ generated catalyst from [RuA C H T U N G T R E N N U N G (benzene)Cl 2 ] 2 , an NHC ligand, and acetonitrile showed excellent activity toward reactions with cyclic secondary amines such as piperidine and morpholine.

The catalytic asymmetric reduction of ketimines has been explored extensively for the synthesis of chiral amines, with reductants ranging from Hantzsch esters, silanes, and formic acid to H2 gas. Alternatively, the amination of alcohols by the use of borrowing hydrogen methodology has proven a highly atom economical and green method for the production of amines without an external reductant, as the alcohol substrate serves as the H2 donor. A catalytic enantioselective variant of this process for the synthesis of chiral amines, however, was not known. We have examined various transition-metal complexes supported by chiral ligands known for asymmetric hydrogenation reactions, in combination with chiral Brønsted acids, which proved essential for the formation of the imine intermediate and the transfer-hydrogenation step. Our studies led to an asymmetric amination of alcohols to provide access to a wide range of chiral amines with good to excellent enantioselectivity.

Well-defined N-heterocyclic carbene based ruthenium complexes were developed as highly active catalysts for direct amide synthesis from alcohols and amines. A catalytic amount of a base such as KOtBu was essential to initiate the catalytic cycle. Activity of the Ru complexes was comparable with the reported in situ Ru catalysts. These catalysts provided mechanistic insight suggesting a Ru hydride species as an active catalytic intermediate. The generation of the Ru hydride was critical for the amidation of free aldehydes.

This chapter offers a general review of the evolvement of methods for the stereoselective synthesis of Z-alkenes, with a focus on the development of catalytic systems towards this goal in recent years.

Z 4 Density (calculated) 1.540 Mg/m 3 Absorption coefficient 0.987 mm -1 F(000) 960 Crystal size 0.30 x 0.20 x 0.20 mm 3 Theta range for data collection 2.61 to 30.50°. Index ranges -22<=h<=22, -12<=k<=11, -20<=l<=20 Reflections collected 25614 Independent reflections 6127 [R(int) = 0.0274] Completeness to theta = 30.50°99.1 % Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.8271 and 0.7561 Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 6127 / 0 / 245 C(10)-N(2) 1.397(2) C(10)-C(11) 1.486(3) C(12)-C(13) 1.362(3) C(12)-N(2) 1.380(2) C(13)-C(14) 1.404(4) C(14)-C(15) 1.367(3) C(15)-C(16) 1.406(3) C(16)-N(1) 1.350(2) C(16)-N(2) 1.368(2) C(17)-N(1) 1.460(2) C(17)-C(18) 1.511(3) C(18)-C(19) 1.385(3) C(18)-C(23) 1.387(3) C(19)-C(20) 1.389(3) C(20)-C(21) 1.377(5) C(21)-C(22) 1.375(4) C(22)-C(23) 1.392(3) C(9)-Rh(1)-C(1) 91.20(8) C(9)-Rh(1)-C(2) 92.28(8) C(5)-C(6)-Rh(1) 70.94(13) C(7)-C(6)-Rh(1) 110.86(15) C(6)-C(7)-C(8) 112.14(19) C(1)-C(8)-C(7) 112.5(2) C(10)-C(9)-N(1) 104.62(15) C(10)-C(9)-Rh(1) 133.43(14) N(1)-C(9)-Rh(1) 121.95(13) C(9)-C(10)-N(2) 108.38(16) C(9)-C(10)-C(11) 131.16(17) N(2)-C(10)-C(11) 120.36(16) C(13)-C(12)-N(2) 119.2(2) C(12)-C(13)-C(14) 120.4(2) C(15)-C(14)-C(13) 120.95(19)c = 11.9178(4) Å = 90°. Volume 2226.22(13) Å 3 Z 4 Density (calculated) 1.602 Mg/m 3 Absorption coefficient 0.926 mm -1 F(000) 1088 Crystal size 0.26 x 0.24 x 0.14 mm 3 Theta range for data collection 2.15 to 26.00°. Index ranges -14<=h<=14, -20<=k<=20, -14<=l<=14 Reflections collected 23557 Independent reflections 4382 [R(int) = 0.0562] Completeness to theta = 26.00°100.0 % Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.8813 and 0.7948