Li-Biao Han

Copper-Catalyzed Aerobic Oxidative Coupling of Terminal Alkynes with H-Phosphonates Leading to Alkynylphosphonates

Copper catalyzed the aerobic oxidative coupling of terminal alkynes with H-phosphonates to afford alkynylphosphonates in high yields.

Facile regio- and stereoselective hydrometalation of alkynes with a combination of carboxylic acids and group 10 transition metal complexes: selective hydrogenation of alkynes with formic acid.

A facile, highly stereo- and regioselective hydrometalation of alkynes generating alkenylmetal complex is disclosed for the first time from a reaction of alkyne, carboxylic acid, and a zerovalent group 10 transition metal complex M(PEt(3))(4) (M = Ni, Pd, Pt). A mechanistic study showed that the hydrometalation does not proceed via the reaction of alkyne with a hydridometal generated by the protonation of a carboxylic acid with Pt(PEt(3))(4), but proceeds via a reaction of an alkyne coordinate metal complex with the acid. This finding clarifies the long proposed reaction mechanism that operates via the generation of an alkenylpalladium intermediate and subsequent transformation of this complex in a variety of reactions catalyzed by a combination of Brϕnsted acid and Pd(0) complex. This finding also leads to the disclosure of an unprecedented reduction of alkynes with formic acid that can selectively produce cis-, trans-alkenes and alkanes by slightly tuning the conditions.

Stereospecific nucleophilic substitution of optically pure H-phosphinates: a general way for the preparation of chiral P-stereogenic phosphine oxides.

Contrary to the generally held view, it is found that the rapid epimerization of (-)-menthyl (RP)-phenylphosphinate under basic conditions is not due to the so far believed inherent stereolability of its corresponding anion but due to a reaction of the hydrogen phosphinate ester with a metal alkoxide. This finding successfully leads to a discovery that, by adding an H-phosphinate to organolithiums or Grignard reagents at a low temperature, the nucleophilic substitution of the alkoxy group of the H-phosphinate with organolithiums or Grignard reagents proceeds stereospecifically with inversion of configurations at phosphorus to give a wide range of P-stereogenic secondary phosphine oxides and tertiary phosphine oxides, by quenching the reaction mixture with water and alkyl halides, respectively. This finding establishes a general protocol for the preparation of optically active secondary phosphine oxides and tertiary phosphine oxides from the easily accessible optically pure H-phosphinates. Mechanistic studies show that the substitution reactions of H-phosphinates with organolithiums and Grignard reagents proceed via two competing reaction paths, that is, a two-step reaction path involving first a deprotonation of H-phosphinates followed by a substitution of the corresponding anion with inversion of configuration at phosphorus and a direct substitution of RM with H-phosphinates generating the SPO directly.

C–P Bond-Forming Reactions via C–O/P–H Cross-Coupling Catalyzed by Nickel

The first Ni-catalyzed C-O/P-H cross-coupling producing organophosphorus compounds is disclosed. This method features wide generality in regard to both C-O and P-H compounds: for C-O compounds, the readily available alcohol derivatives of aryl, alkenyl, benzyl, and allyl are applicable, and for P-H compounds, both >P(V)(O)H compounds (secondary phosphine oxide, H-phosphinate, and H-phosphonate) and hydrogen phosphines (>P(III)H) can be used as the substrates. Thus, a variety of valuable C(sp(2))-P and C(sp(3))-P compounds can be readily obtained in good to excellent yields by this new strategy.

Stereospecific Coupling of H-Phosphinates and Secondary Phosphine Oxides with Amines and Alcohols: A General Method for the Preparation of Optically Active Organophosphorus Acid Derivatives†

The reaction of H-phosphinates and secondary phosphine oxides with amines and alcohols proceeds highly stereospecifically to give the corresponding coupling products with inversion of configuration at the phosphorus center under the Atherton-Todd reaction conditions. This finding leads to the establishment of a general and efficient method for the synthesis of a variety of optically active organophosphorus acid derivatives from the easily available chiral H-phosphinates and secondary phosphine oxides.

Phosphinic Acid Induced Reversal of Regioselectivity in Pd-Catalyzed Hydrophosphinylation of Alkynes with Ph2P(O)H

One drop is enough to switch from hydropalladation to phosphinylpalladation. If one drop of diphenylphosphinic acid is added for the hydrophosphinylation of alkynes with diphenylphosphane oxide, there is a reversal in regioselectivity (as shown below).

Copper-Catalyzed Aerobic Oxidative Amination of sp3C–H Bonds: Efficient Synthesis of 2-Hetarylquinazolin-4(3H)-ones

An efficient synthesis of 2-hetarylquinazolin-4(3H)-ones via copper-catalyzed direct aerobic oxidative amination of sp(3)C-H bonds has been developed. This tandem oxidation-amination-cyclization transformation represents a straightforward protocol to prepare 2-hetaryl-substituted quinazolinones from easily available 2-aminobenzamides and (2-azaaryl)methanes.

Palladium-Catalyzed Dehydrogenative Cis Double Phosphorylation of Alkynes with H-Phosphonate Leading to (Z)-Bisphosphoryl-1-alkenes

Dehydrogenative cis double phosphorylation of terminal alkynes with H-phosphonate took place efficiently in the presence of a divalent palladium catalyst to afford (Z)-bisphosphoryl-1-alkenes selectively.

Efficient Pd-Catalyzed Dehydrogenative Coupling of P(O)H with RSH: A Precise Construction of P(O)–S Bonds

A Pd-catalyzed dehydrogenative phosphorylation of thiols is developed. A variety of thiols dehydrogenatively couple readily with all three kinds of P(O)-H compounds, i.e., H-phosphonates, H-phosphinates, and secondary phosphine oxides, providing a general access to the valuable phosphorothioates including the P-chiral compounds. A plausible mechanism is proposed.

Stereospecific Halogenation of P(O)-H Bonds with Copper(II) Chloride Affording Optically Active Z1Z2P(O)Cl

A general and efficient method for the preparation of optically active Z1Z2P(O)Cl from the easily prepared optically active H-phosphinates and H-phosphine oxides was reported. H-Phosphinates and H-phosphine oxides react stereospecifically with CuCl2 to produce the corresponding optically active Z1Z2P(O)Cl with retention of configuration at the phosphorus center. Optically active Z1Z2P(O)Cl reacts easily with a variety of nucleophiles to produce other chiral organophosphorus acid derivatives with inversion of configuration at phosphorus.