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An Ir-catalyzed enantioselective hydrogenation of 2-alkyl-pyridines has been developed using ligand MeO-BoQPhos. High levels of enantioselectivities up to 93:7 er were obtained. The resulting enantioenriched piperidines can be readily converted into biologically interesting molecules such as the fused tricyclic structures 5, 6, and 7 in 99:1 er, providing a novel, concise synthetic route to this family of chiral piperidine-containing compounds.

Novel bidentate phosphine ligands BABIPhos featuring a biaryl bis-dihydrobenzooxaphosphole core are presented. Their synthesis was achieved via Pd-catalyzed reductive homocoupling of dihydrobenzooxaphosphole aryl triflates. An efficient route toward various analogues was also established, giving access to phosphines with different electronic and steric properties. The newly obtained ligands demonstrated high efficiency and selectivity in Rh-catalyzed asymmetric hydrogenation of di- and trisubstituted enamides. This new class of ligands is complementary to previously described bidentate benzooxaphosphole ligands BIBOP.

An efficient enantioselective synthesis of the chiral polycyclic cholesteryl ester transfer protein (CETP) inhibitor 1 has been developed. The synthesis was rendered practical for large scale via the development of a modified Hantzsch-type reaction to prepare the sterically hindered pyridine ring, enantioselective hydrogenation of hindered ketone 6 utilizing novel BIBOP-amino-pyridine derived Ru complex, efficient ICl promoted lactone formation, and a BF3 mediated hydrogenation process for diastereoselective lactol reduction. This efficient route was successfully scaled to produce multikilogram quantities of challenging CETP drug candidate 1.

The first uncatalyzed hydrophosphinations of propargylic amines and alcohols with phosphine- borane complexes are described. The reactions proceed at ambient temperature or below without the use of protecting groups or the need to handle pyrophoric secondary phosphines, furnishing air-stable phosphineborane-amines and alcohols in good yields. Utilization of chiral propargylic substrates and unsymmetrical secondary phosphineboranes leads to diastereomeric P-chiral products that can be separated by fractional crystallization or chromatography. Initial applications of these new P-X species to asymmetric catalysis are detailed.

A series of novel, efficient, air-stable, and tunable chiral bisdihydrobenzooxaphosphole ligands (BIBOPs) were developed for rhodium-catalyzed hydrogenations of various functionalized olefins such as alpha-arylenamides, alpha-(acylamino)acrylic acid derivatives, beta-(acylamino)acrylates, and dimethyl itaconate with excellent enantioselectivities (up to 99% ee) and reactivities (up to 2000 TON).

Reaction of 4-bromo-NH-1,2,3-triazoles 2 with alkyl halides in the presence of K(2)CO(3) in DMF produced the corresponding 2-substituted 4-bromo-1,2,3-triazoles 5 in a regioselective process. Subsequent Suzuki cross-coupling reaction of these bromides provided an efficient synthesis of 2,4,5-trisubstituted triazoles 3. In addition, reduction of the bromotriazoles by hydrogenation furnished an efficient synthesis of 2,4-disubstituted triazoles 8.

[reaction: see text] Diisobutylaluminum hydride (DIBAL-H) and triisobutylaluminum have been found to be outstanding reductants for secondary phosphine oxides (SPOs). All classes of SPOs can be readily reduced, including diaryl, arylalkyl, and dialkyl members. Many SPOs can now be reduced at cryogenic temperatures, and conditions for preservation of reducible functional groups have been found. Even the most electron-rich and sterically hindered phosphine oxides can be reduced in a few hours at 50-70 degrees C. This new reduction has distinct advantages over existing technologies.

Reaction of 4,5-dibromo-1,2,3-triazole with electron-deficient aromatic halides in the presence of potassium carbonate in DMF produces the corresponding 2-aryl-4,5-dibromotriazoles with high regioselectivity. Subsequent debromination of these triazoles by hydrogenation furnishes 2-aryltriazoles in excellent yields. Overall, this two-step process provides an efficient access to 2-aryl-1,2,3-triazoles.

(S)-3,3′-F2-BINOL has been synthesized for the first time and demonstrated as a highly active organocatalyst for asymmetric methallylation of ketones. Up to 98:2 enantioselectivity and 99% yield were obtained with 5 mol % catalyst loading. The catalyst (S)-3,3′-F2-BINOL could be easily recovered and reused.

Hydrophosphination of secondary propargylic alcohols generates phosphine-containing allylic alcohols that undergo facile [2,3]-sigmatropic rearrangements with chlorophosphines, furnishing highly enantioenriched, crystalline diphosphine monoxides. The configuration at the newly formed stereocenter is opposite to that expected based on prior studies, and an ab initio computational evaluation of the possible transition states was performed to help explain the stereochemical course of the reaction.

A highly convergent large scale synthesis of a 15-membered macrocyclic hepatitis C virus (HCV) protease inhibitor BI 201302 was achieved, in which the key features are the practical macrocyclization by Ru-catalyzed ring-closing metathesis (0.1 mol % Grela catalyst, 0.1–0.2 M concentration) and the efficient sulfone-mediated SNAr reaction.

The palladium catalyzed alkoxycarbonylation and aminocarbonylation of vinyl tosylates are described. A variety of ketone and aldehyde derived vinyl tosylates may be carbonylated in the presence of primary, secondary, and tertiary alcohols, or primary and secondary amines, to provide the corresponding esters and amides in good yields. The alkoxycarbonylation was applied to a short synthesis of isoguvacine.

The first report of monitoring the kinetics of racemization in solution by online vibrational circular dichroism (VCD), chemometrics, and density functional theory (DFT) calculations is presented. The activation energy for the racemization of an imidazoline based on the experimental VCD was determined, and the detailed mechanism of the process utilizing DFT calculations was elucidated. This study demonstrates the utility of VCD for the determination of reaction mechanisms in asymmetric transformations.

A series of structurally novel, operationally convenient, and efficient chiral 2-phosphino-2,3-dihydrobenzo[d][1,3]oxaphosphole ligands was developed. Applications of ligands 3a and 3b in rhodium-catalyzed asymmetric hydrogenation of alpha-(acylamino)acrylates and beta-(acylamino)acrylates provided excellent enantioselectivities (up to99% ee) and reactivities (up to 10,000 TON).

Phosphine boranes have been found to hydrophosphinate internal, unactivated alkynes at room temperature under basic conditions without the need for catalysts or radical initiators. The use of air-sensitive secondary phosphines is avoided in this facile process. Broad scope in both the phosphine borane and alkyne partners leads to excellent diversity in the phosphine products. Asymmetric hydrogenation of these species then provides one of the shortest possible routes to chiral monodentate phosphines. Hydrophosphination of allenyl phosphine oxides under similar conditions followed by hydrogenation of the exomethylene moiety yields a wide variety of bis-phosphine derivatives.

Asymmetric hydrogenation of unsaturated urea esters with the BIPI Ligands has been examined. Optimization of the P−N ligand structure has led to the development of chiral rhodium catalysts capable of producing the targets with >99% ee. The critical phosphine borane SNAr reaction needed for ligand synthesis has been optimized to give the adducts in high yield at ambient temperature with no racemization. An extremely concise, economical, and scalable sequence to these important new ligands for catalysis of asymmetric hydrogenation has been developed.