Phannarath Phansavath

General asymmetric hydrogenation of 2-alkyl- and 2-aryl-substituted quinoxaline derivatives catalyzed by iridium-difluorphos: Unusual halide effect and synthetic application

A general asymmetric hydrogenation of a wide range of 2-alkyl- and 2-aryl-substituted quinoxaline derivatives catalyzed by an iridium-difluorphos complex has been developed. Under mild reaction conditions, the corresponding biologically relevant 2-substituted-1,2,3,4-tetrahydroquinoxaline units were obtained in high yields and good to excellent enantioselectivities up to 95%. With a catalyst ratio of S/C = 1000 and on a gram scale, the catalytic activity of the Ir-difluorphos complex was maintained showing its potential value. Finally, we demonstrated the application of our process in the synthesis of compound (S)-9, which is an inhibitor of cholesteryl ester transfer protein (CETP).

Ruthenium-SYNPHOS-catalyzed asymmetric hydrogenations: an entry to highly stereoselective synthesis of the C15-C30 subunit of dolabelide A.

An efficient construction of the C15-C30 segment of the cytotoxic macrolide dolabelide A is described. The synthesis relies on ruthenium-SYNPHOS-mediated asymmetric hydrogenation reactions of beta-keto esters to generate the C19, C21, and C27 hydroxyl-bearing stereocenters with very high levels of enantio- and diastereoselectivity.

Synthetic strategy toward the C44-C65 fragment of mirabalin.

A convergent and flexible stereoselective synthesis of one isomer of the C44-C65 fragment of mirabalin is described. The key steps include organocatalytic aldolization, ruthenium-catalyzed asymmetric hydrogenation, amide formation, Marshall stereoselective allenylation, and the Nozaki-Hiyama-Kishi reaction.

Heck Coupling Using a Vinyliodo-MIDA Boronate: An Efficient and Modular Access to Polyene Frameworks

A simple Heck coupling between an alkenyl iodo-boronate and a variety of terminal olefins is disclosed. This method gives access to a wide range of dienic moieties including valuable bis-functionalized dienes. The synthetic potential of the coupling reaction is demonstrated by a short and modular preparation of several tetraenic compounds.

The [4+2], [2+2] strategy for the construction of the AB taxane ring system

Abstract The construction of the AB taxane ring system through a [4+2] reaction and Co(I)-[2+2] cyclization is presented. For the first time, CpCo(CO) 2 catalyzes the ring closure of strained polyunsaturated triynic compound into eight-membered ring.

Asymmetric Transfer Hydrogenation of (Hetero)arylketones with Tethered Rh(III)–N-(p-Tolylsulfonyl)-1,2-diphenylethylene-1,2-diamine Complexes: Scope and Limitations

A series of new tethered Rh(III)/Cp* complexes containing the N-(p-tolylsulfonyl)-1,2-diphenylethylene-1,2-diamine ligand have been prepared, characterized, and evaluated in the asymmetric transfer hydrogenation (ATH) of a wide range of (hetero)aryl ketones. The reaction was performed under mild conditions with the formic acid/triethylamine (5:2) system as the hydrogen source and provided enantiomerically enriched alcohols with good yields and high to excellent enantioselectivities. Although the nature of the substituents on the phenyl tethering ring did not alter the stereochemical outcome of the reaction, complexes bearing electron-donating groups exhibited a higher catalytic activity than those having electron-withdrawing groups. A scale-up of the ATH of 4-chromanone to the gram scale quantitatively delivered the reduced product with excellent enantioselectivity, demonstrating the potential usefulness of these new complexes.

Asymmetric transfer hydrogenation of α-amino β-keto ester hydrochlorides through dynamic kinetic resolution

The development of Ru-catalyzed asymmetric transfer hydrogenation of α-amino β-keto ester hydrochlorides is described. The reaction proceeds through dynamic kinetic resolution to afford anti β-hydroxy α-amino esters with good diastereomeric ratios and high enantioselectivities.

Transition‐Metal‐Catalyzed Asymmetric Hydrogenation and Transfer Hydrogenation: Sustainable Chemistry to Access Bioactive Molecules

Over the last few decades, the development of new and highly efficient synthetic methods to obtain chiral compounds has become an increasingly important and challenging research area in modern synthetic organic chemistry. In this account, we review recent work from our laboratory toward the synthesis of valuable chiral building blocks through transition-metal-catalyzed asymmetric hydrogenation and transfer hydrogenation of C=O, C=N and C=C bonds. Application to the synthesis of biologically relevant products is also described.

Guidelines to design organic electrolytes for lithium-ion batteries: environmental impact, physicochemical and electrochemical properties

Electrolytes for lithium-ion batteries (LiBs) have been put aside for too long because a few new solvents have been designed to match electrolyte specifications. Conversely, significant attention has been paid to synthesize new electrode materials and especially positive electrodes. Particularly, most of the studies dedicated to the investigation of electrolytes for LiBs have been focused on mixing different molecules. Currently, the development of high-voltage materials for LiBs stimulates the synthesis of new solvents and new salts that are more stable against oxidation. Despite the challenges, only a few teams are active in this field in developing a rational approach combining physicochemistry, electrochemistry and modelling from the molecular to the macromolecular levels. After assembling a critical collection of physicochemical and electrochemical data from the literature, this study highlights the main trends between the chemical structure of the organic dipolar aprotic solvents and their physicochemical and electrochemical properties to provide a guide for chemists to design new electrolytes for LiBs. This guide also includes indicators to take into account the environmental impact of solvent production by including a life cycle assessment of eight different solvents.

Synthetic Studies toward the C14–C29 Fragment of Mirabalin

A convergent synthesis of one isomer of the C14-C29 fragment of mirabalin is disclosed. The key steps include a Marshall allenylation, a Mukaiyama aldol reaction and a Crimmins aldolization, which allow the control of 10 out of 25 stereogenic centers present in the molecule.