CsOH-promoted epoxide ring-opening with phosphines: mild and efficient synthesis of monohydroxyphosphines

Siloxane-containing phosphine (oxide) ligands for enhanced catalytic activity of cobalt complexes for hydrosilylation reactions

A series of siloxane-containing phosphine (oxide) ligands have been designed and synthesized. These phosphine (oxide) ligands contain silicon atoms, which can impart better solubility in the relevant media, thereby improving certain catalytic performances. The hydrosilylation of olefins catalyzed by these metal phosphine (oxide) complexes has been conducted under mild reaction conditions.

Diastereoselective Synthesis of P-Stereogenic Secondary Phosphine Oxides (SPOs) Bearing a Chiral Substituent by Ring Opening of (+)-Limonene Oxide with Primary Phosphido Nucleophiles

Kinetic separation of the commercially available cis/trans-(+)-limonene oxide mixture by ring opening with primary phosphido nucleophiles LiPHR (R = ferrocenyl, Ph, Cy, t-Bu, Mes* (Mes* = 2,4,6-(t-Bu)₃C₆H₂)), followed by treatment with aqueous NH₄Cl and H₂O₂, gave unreacted cis-(+)-limonene oxide and diastereoenriched mixtures of the secondary phosphine oxides (SPOs) PHR(trans-(+)-Lim-OH)(O), which could be separated by chromatography and/or recrystallization. This one-pot synthesis uses a cheap chiral material and commercially available primary phosphines to control the configuration of the new P-stereogenic SPOs, which are potentially useful as ligands for metal complexes in asymmetric catalysis.

Catalytic Asymmetric Synthesis of P-Stereogenic Phosphines: Beyond Precious Metals

Metal-catalyzed asymmetric synthesis of P-stereogenic phosphines is a potentially useful approach to a class of chiral ligands with valuable applications in asymmetric catalysis. We introduced this idea with chiral platinum and palladium catalysts, exploiting rapid pyramidal inversion in diastereomeric metal–phosphido complexes (ML*(PRR′)) to control phosphorus stereochemistry. This Account summarizes our attempts to develop related synthetic methods using earth-abundant metals, especially copper, in which weaker metal–ligand bonds and faster substitution processes were expected to result in more active catalysts. Indeed, precious metals were not required. Without any transition metals at all, we exploited related P-epimerization processes to prepare enantiomerically pure phosphiranes and secondary phosphine oxides (SPOs) from commercially available chiral epoxides.

1 Introduction

2 Copper-Catalyzed Phosphine Alkylation

3 Copper-Catalyzed Tandem Phosphine Alkylation/Arylation

4 Nickel-Catalyzed Phosphine Alkylation

5 Proton-Mediated P-Epimerization in Synthesis of Chiral Phosphiranes

6 Diastereoselective Synthesis of P-Stereogenic Secondary Phosphine Oxides (SPOs) from (+)-Limonene Oxide

7 Conclusions

Studies on asymmetric total synthesis of (-)-β-hydrastine via a chiral epoxide ring-opening cascade cyclization strategy

Herein, facile and enantioselective approaches to synthesize the core phthalide tetrahydroisoquinoline scaffold of (-)-β-hydrastine via both a CF3COOH-catalyzed (86% ee) and KHMDS-catalyzed (78% ee) epoxide ring-opening/transesterification cascade cyclization from chiral epoxide under very mild conditions are described. The key elements include a highly enantioselective epoxidation using the Shi ketone catalyst and an intramolecular CF3COOH-catalyzed cascade cyclization in one pot, and a late-stage C-3' epimerization under MeOK/MeOH conditions as the key steps to achieve the first total synthesis of (-)-β-hydrastine (up to 81% ee).

Conversion of azides into diazo compounds in water

Diazo compounds are in widespread use in synthetic organic chemistry but have untapped potential in chemical biology. We report on the design and optimization of a phosphinoester that mediates the efficient conversion of azides into diazo compounds in phosphate buffer at neutral pH and room temperature. High yields are maintained in the presence of common nucleophilic or electrophilic functional groups, and reaction progress can be monitored by colorimetry. As azido groups are easy to install and maintain in biopolymers or their ligands, this new mode of azide reactivity could have substantial utility in chemical biology.

Synthesis of New Enantiomerically Enriched β-Hydroxy-γ-amino Phosphines by Selective Transformation of Naturally Occurring Amino Acids

Ring opening of amino epoxides derived from naturally occurring amino acids with lithium diphenylphosphido borane is reported as an efficient approach to a new family of enantiomerically enriched multifunctional phosphines.

A Novel and Highly Efficient Synthetic Route to Unsymmetrical Organoselenides Using Cesium Bases

A new and convenient one-pot method for the preparation of unsymmetrical selenides has been developed. In the presence of cesium hydroxide, molecular sieves, and DMF, benzeneselenol undergoes direct alkylation with various alkyl halides for the synthesis of alkyl phenyl selenides in moderate to excellent yields. Another method to prepare unsymmetrical organoselenides was also completed by coupling terminal alkynes with benzeneselenyl bromide. As an application, the synthesis of a selenopeptide was also accomplished. Furthermore, this methodology was extended to the synthesis of an organoselenide on solid support.