New methods for the preparation of NHC-metal complexes have been developed. It was shown that a nitrile group in Reissert analogous compounds can act as a good leaving group in thermal elimination, resulting in carbene formation. Moreover potassium carbonate was introduced as a highly efficient and mild reagent for the generation of N-heterocyclic carbene complexes in good to excellent yields, even in water, as the most environmentally friendly medium.

Novel water-soluble ligands were prepared in high yields by condensation of various amino acids with tris(hydroxymethyl)phosphane. Rhodium complexes of these ligands, formed in situ, were tested in two-phase hydroformylation of propylene. Selectivity observed with these ligand systems is easily controlled by altering the pH of the reaction mixture.

A chiral C-2-symmetric diamine was prepared from (S)-3-phenyl-3,4-dihydroisoquinoline by the virtue of asymmetric transformation. Rhodium and iridium complexes of chiral N-heterocyclic carbenes with restricted flexibility derived from 3,3'-substituted partially reduced biisoquinoline were obtained by transmetalation from the corresponding silver(I) complexes. Unexpected double-bond formation in the carbene ligand has occurred during a transmetalation step. The structures of these complexes were verified by X-ray diffraction. Metal complexes of these N-heterocyclic carbenes were applied to the asymmetric hydrogenation of methyl 2-acetamidoacrylate. Good enantioselectivities of up to 67% ee were achieved.

New C-2-symmetric atropisorneric diazepinium salts were prepared utilizing Vilsmeier-Haack activation of corresponding formamide precursors by phosgene solution in toluene. The structures of these substances were verified by X-ray diffraction.

New and reliable procedures for the preparation of both enantiomers of 2,2'-bipiperidine have been developed. Chiral imidazolinium salts derived from 2,2'-bipiperidine and partially reduced biisoquinoline were prepared in high yields. Rhodium and iridium complexes of new chiral N-heterocyclic carbenes were obtained by transmetalation from corresponding silver(I) complexes. The structures of these complexes were verified by X-ray diffraction. The novel carbenes seem to range between the very electron-rich bis(amido)carbenes and the imidazole-derived carbenes with regard to the electronic ligand properties (IR evidence). Rhodium and iridium complexes were applied to a variety of catalytic asymmetric reactions. Modest enantioselectivities of up to 28% ee were observed.

The fully protected derivatives of the diamino acids lysine and ornithine (n = 1, 2) can be oxidized selectively in the side chain using a Mn(OAc)(2)/peracetic acid/NaOAc system. The epsilon or gamma carbon, respectively, is converted to the aldehyde oxidation state, protected as the cyclic N,N-acetal. (C) 2004 Elsevier Ltd. All rights reserved.