Hammond Postulate Mirroring Enables Enantiomeric Enrichment of Phosphorus Compounds via Two Thermodynamically Interconnected Sequential Stereoselective Processes

Deoxyfluorination of 1°, 2°, and 3° Alcohols by Nonbasic O-H Activation and Lewis Acid-Catalyzed Fluoride Shuttling

A method for deoxyfluorination of aliphatic primary, secondary, and tertiary alcohols is reported, employing a nontrigonal phosphorus triamide for base-free alcohol activation in conjunction with an organic soluble fluoride donor and a triarylborane fluoride shuttling catalyst. Mechanistic experiments are consistent with a reaction that proceeds by the collapse of an oxyphosphonium fluoroborate ion pair with fluoride transfer. The substrate scope complements existing deoxyfluorination methods and enables the preparation of homochiral secondary and tertiary alkylfluorides by stereoinversion of the substrate alcohol.

Unexpected rapid P-stereomutation of phosphine oxides catalysed by chlorophosphonium salts

P-Stereomutation of phosphine oxides is extremely slow. We show that it is catalysed by chlorophosphonium salts (CPS) which can directly be formed in the system in situ. The racemization of phosphine oxides at ambient conditions catalysed by 1 mol% of CPS takes 1-2 hours and can be arrested by additon of a primary alcohol. The process probably proceeds via the development of oxodiphosphonium P-O-P species.

Copper-Catalyzed Dynamic Kinetic Resolution of Secondary Phosphine Oxides

Copper-catalyzed dynamic kinetic resolution of secondary phosphine oxides has been successfully developed, providing a general method for the gram-scale enantioselective synthesis of P-stereogenic cyclic phosphine oxides with high yields and high enantioselectivities. The products could be easily reduced to the corresponding useful P(III)-stereogenic cyclic phosphines. A mechanism of the dynamic kinetic resolution involving the unusual rapid racemization of SPOs has been proposed.

The stereoselective conversion of epimerized alkoxyl phosphine-borane to P,C, axial-stereogenic tertiary phosphine via cleavage of P-O bond

The P-O bond of epimerized alkoxyl phosphine-borane was cleaved by naphthalene-lithium, to form two diastereomers of P-anions in a ratio of 86 : 14, which was then converted to secondary phosphine-borane via acidification, and to tertiary phosphines with alkyl halides with enhanced 96 : 4 dr. The isolated tertiary phosphine containing hydroxyl (in >99 : 1 dr) was converted to multi-stereogenic tertiary phosphines via O-alkylation with alkylene dihalides.

Preparation of Enantiomerically Enriched P-Stereogenic Dialkyl-Arylphosphine Oxides via Coordination Mediated Optical Resolution

Optical resolution of several dialkyl-arylphosphine oxides was elaborated using the Ca2+ salt of (−)-O,O’-dibenzoyl-(2R,3R)-tartaric acid as the resolving agent. The conditions of crystallization and purification of the enantiomerically enriched phosphine oxides were optimized. Ethyl-phenyl-propylphosphine oxide and butyl-methyl-phenylphosphine oxide were prepared with an enantiomeric excess higher than 93%, whereas, three other dialkyl-arylphosphine oxides were obtained with an enantiomeric excess of 37–85%. It was also found that the sterically demanding alkyl chains hinder the formation of stable diastereomeric complexes, which consequently led to less efficient resolution procedures.

The construction of three C–P bonds of P-stereogenic tertiary phosphines containing (l)-menthyl

A wide range of R_P or S_P-(l)-menthyl-containing SPOs were prepared via the reaction of 1,1′-bi(2-naphthol) derived phosphonite with a metallic reagent with excellent yield and dr.

Synthesis of glycosyl chlorides using catalytic Appel conditions

The stereoselective synthesis of glycosyl chlorides using catalytic Appel conditions is described. Good yields of α-glycosyl chlorides were obtained using a range of glycosyl hemiacetals, oxalyl chloride and 5 mol% Ph₃PO. For 2-deoxysugars treatment of the corresponding hemiacetals with oxalyl chloride without phosphine oxide catalyst also gave good yields of glycosyl chloride. The method is operationaly simple and the 5 mol% phosphine oxide by-product can be removed easily. Alternatively a one-pot, multi-catalyst glycosylation can be carried out to transform the glycosyl hemiacetal directly to a glycoside.

Functional Phosphine Derivatives Having Stationary and Flexible Chiralities: Their Preparation and Chirality Controlling

Various functional secondary and tertiary phosphines, or their derivatives, containing stationary chiral phosphorus and flexible chiral axis were prepared, which could be further modified to afford diversely chelating ligands. The flexible axial chirality was fixed by stereogenic phosphorus via a cyclic linkage of chemical bonds or coordination with a metallic ion.

Direct Aryloxylation/Alkyloxylation of Dialkyl Phosphonates for the Synthesis of Mixed Phosphonates

A strategy for the direct functionalization strategy of inertial dialkyl phosphonates with hydroxy compounds to afford diverse mixed phosphonates with good yields and functional-group tolerance has been developed. Mechanistic investigations involving both NMR studies and DFT studies suggest that an unprecedented highly reactive P^V species (phosphoryl pyridin-1-ium salt), a key intermediate for this new synthetic transformation, is generated in situ from dialkyl phosphonate in the presence of Tf₂ O/pyridine.

Long sought synthesis of quaternary phosphonium salts from phosphine oxides: inverse reactivity approach

Reaction of Grignard reagents with chlorophosphonium salts provides a conceptually new synthesis of quaternary phosphonium salts from phosphine oxides by using inverse reactivity at phosphorus.

Applications and stereoselective syntheses of P-chirogenic phosphorus compounds

This review reports the best stereoselective or asymmetric syntheses, the most efficient P*-building blocks and functionalisation of P-chirogenic compounds, in the light of chiral phosphorus compound applications.

Ruthenium complexes of P-stereogenic phosphines with a heterocyclic substituent

Optically pure P-stereogenic monophosphorus ligands containing a heterocyclic substituent have been prepared. They have been coordinated to Ru-η⁶-arene moieties in which the ligands act as mono- or bidentate. The complexes catalyse asymmetric transfer hydrogenation reactions with up to 70% ee.

Chemoselective reduction of the phosphoryl bond of O-alkyl phosphinates and related compounds: an apparently impossible transformation

A method is reported for the phosphoryl bond cleavage of O-alkyl phosphinates, phosphinothioates and certain phosphonamidates to furnish the corresponding P(iii) borane adducts.