Synthesis of chiral boranes asymmetric insertion of carbenes into B-H bonds catalyzed by the rhodium(I) diene complex.

Molecules with chiral boron atoms have been scarcely studied due to limited synthetic access. Herein, we report a new method for their synthesis asymmetric insertion of arydiazoacetates into the B-H bonds of prochiral carbene-boranes NHC-BHR. The reaction is catalyzed by the rhodium(I) complex with the chiral diene ligand Bu-TFB, which can be conveniently prepared by diastereoselective coordination of the racemic diene with (-Salox)Rh(CO).

Planar-chiral arene ruthenium complexes: synthesis, separation of enantiomers, and application for catalytic C-H activation.

Heating -butyl-tetraline with [(-cymene)RuCl] produces the racemic complex [(arene)RuCl], which can be separated into enantiomers by chromatography of its diastereomeric adducts with chiral phosphine ligand. The resolved chiral complex catalyzes C-H activation of -methoxy-benzamides and their annulation with -vinyl-pivaloyl amide giving dihydroisoquinolones in 50-80% yields and with 40-80% enantiomeric excess.

Simplified Version of the Eschweiler-Clarke Reaction.

The traditional Eschweiler-Clarke reaction is a three-component process involving formaldehyde, amine, and formic acid. In this work, we showed that the reductive potential of formaldehyde was sufficient to provide methylation of secondary amines in the absence of acidic additives. Various acid-sensitive moieties remain intact under developed conditions.

Planar Chiral Rhodium Complex Based on the Tetrahydrofluorenyl Core for Enantioselective Catalysis.

A simple four-step route to a chiral tetrahydrofluorenyl rhodium catalyst from naturally occurring (-)-α-pinene was developed. Our approach does not use multistep and time-consuming procedures such as chiral HPLC or diastereomeric resolution. The key to success lies in the face-selective coordination of rhodium to the sterically hindered tetrahydrofluorenyl ligand, giving only one diastereomeric complex.

Rhodium complexes with planar-chiral cyclopentadienyl ligands: synthesis from -butylacetylene and catalytic performance in C-H activation of arylhydroxamates.

The rhodium complex [(CHBuCHBu)RhCl] with an asymmetric cyclopentadienyl ligand was prepared in 95% yield by the reaction of [(cod)RhCl] with -butylacetylene in the presence of AlCl. A similar reaction in the presence of InBr gave the cationic fulvene complex [(CHBu = CHBu)Rh(cod)]InBr (70%), which can add alcohols ROH and produce more bulky catalysts [(CHBuCH(OR)Bu)RhCl]. The enantiomers of these planar-chiral complexes were separated by thin-layer chromatography in the presence of L-phenylglycinol.

Sodium Hypophosphite as a Bulk and Environmentally Friendly Reducing Agent in the Reductive Amination.

NaHPO was found to promote reductive amination. Being nontoxic, stable, environmentally benign, and available in bulk amounts, this reducing agent showed a powerful potential to compete with classical reductants applied in the target process. An factor of 1 was achieved for the substrate scope.

Redox Condensations of -Nitrobenzaldehydes with Amines under Mild Conditions: Total Synthesis of the Vasicinone Family.

A total synthesis of the vasicinone family of natural products from bulk chemicals was developed. Reductive condensation of nitrobenzaldehydes with amines utilizing iron pentacarbonyl as a reducing agent followed by subsequent oxidation leads to a great variety of polycyclic nitrogen-containing heterocycles under mild conditions. Enantiomerically pure vasicinone, rutaecarpine, isaindigotone, and luotonin were synthesized from readily available starting materials like hydroxyproline, nitrobenzaldehyde, pyrrolidine, and piperidine in two to four operational steps without chromatography.