Xiaoxia Lu

Synthesis, photophysics and binding studies of Pt(II) alkynyl terpyridine complexes with crown ether pendant. Potential luminescent sensors for metal ions

Two crown ether-containing platinum(II) alkynyl terpyridine complexes, [Pt(tpy)(CC-benzo-15-crown-5)]OTf (1) and [Pt(tpy)(CC-N-phenylaza-15-crown-5)]OTf (2) (tpy = 2,2′:6′,2″-terpyridine), have been synthesized and characterized. UV-vis spectrophotometric, emission and 1H NMR titration methods were employed to investigate their ion-binding properties. Complex 1 was found to show luminescence enhancement upon binding of Mg2+ and Ca2+ ions to its crown cavity.

Palladium-Catalyzed Cascade Oxidation/sp2 C–H Acylation of Azoarenes with Aryl Methanes

A Pd-catalyzed cascade oxidation/sp(2) C-H bond acylation of azoarenes was developed in which readily available aryl methanes were used as the in situ generated acyl sources. This reaction provides a convenient access to ortho-acyl azoarenes under mild conditions.

Chiral Lewis Base Catalyzed Highly Enantioselective Reduction of N‐Alkyl β‐Enamino Esters with Trichlorosilane and Water

First, test the water! In the presence of a chiral Lewis base catalyst 2, the supposedly moisture-unfriendly reduction system with trichlorosilane was found to be highly efficient and enantioselective when using water as an additive. For the first time, this method enables the reduction of a broad range of N-alkyl beta-enamino esters 1 to give N-alkyl beta-amino esters 3 in good to high yields and with excellent enantioselectivities (see scheme).

Palladium(II)-catalyzed enantioselective arylation of α-imino esters.

A protocol for Pd(II)-catalyzed asymmetric arylation of N-aryl imino esters has been developed. The method affords a practical and direct access to chiral arylglycine derivatives in good yields and with high enantioselectivities.

Synthesis, structure, and ion-binding studies of cobalt(II) complexes with aza-crown substituted salicylaldimine Schiff base ligand

A series of cobalt(II) complexes with azacrown ether-containing salicylaldimine Schiff base ligand Co(L1), Co(L2) 2 and Co(L3) 2 has been successfully synthesized. The cation-binding properties of the complexes have been studied and the stability constants with alkali and alkaline earth metal cations determined. Synthesis of the complexes with monoaza-12-crown-4, Co(L1) and Co(L2) 2 , allows for a direct comparison of the cation binding properties between the mono- and bis-Schiff base systems as well as with the complex containing the monoaza-15-crown-5 pendant, i.e. Co(L3) 2 , which has a different crown size. The X-ray crystal structure of Co(L3) 2 has also been determined.

Synthesis and biological activities of novel nonpeptide angiotensin II receptor antagonists based on benzimidazole derivatives bearing a heterocyclic ring

A series of benzimidazole derivatives bearing a heterocyclic ring imidazole (1), 5-chloroimidazole (2), 1,2,4-triazol (3), and imidazoline (4) were synthesized and evaluated for angiotensin II antagonistic activities. The synthetic compounds 1-4 were biologically evaluated in vitro using an AT(1) receptor binding assay, where compounds 1 and 3 provided weak binding affinity, compound 2 showed moderate binding affinity, and compound 4 showed good binding affinity. Moreover, compound 4 was found to be almost equipotent with telmisartan in vivo biological evaluation study.

Pd(II)-Catalyzed Pyridine N-Oxides Directed Arylation of Unactivated Csp3–H Bonds

A novel Pd(II)-catalyzed pyridine N-oxide directed remote arylation of unactivated Csp(3)-H bonds in aliphatic amides with aryl iodides has been developed. This protocol allows installing various aryl groups at the β- or γ-Csp(3) atom of alkyl carboxylic acid amides. The key palladabicyclic intermediate of this transformation has been identified by HR-MS and (1)H NMR method.

Ruthenium(II)-catalyzed regioselective reductive coupling of α-imino esters with dienes.

A method for the highly regioselective reductive coupling reaction of N-aryl-α-imino esters with dienes is described. The method utilizes the RuHCl(CO)(PPh3)3/iPrOH catalytic system under an Ar atmosphere and provides α-branched allylic α-amino acid derivatives. Application of this transformation to the concise synthesis of a natural plant growth regulator is demonstrated.

Pd-catalyzed tandem cyclization of ethyl glyoxalate and amines: rapid assembly of highly substituted cyclic dehydro-α-amino acid derivatives.

A novel cascade cyclization of ethyl glyoxalate and amines proceeds in the presence of Pd(TFA)(2) (5 mol %) to give the cyclic dehydro-α-amino acid derivatives. This method provides a fast and simple access to highly substituted dihydro-pyrrol-2-ones in good yields.

Co(II)-Catalyzed Regioselective Cross-Dehydrogenative Coupling of Aryl C–H Bonds with Carboxylic Acids

A cobalt(II)-catalyzed regioselective aryl C-H bond oxygenation between arenes and aryl or aliphatic carboxylic acids under bidendate-chelation assistance is developed. This method provides an efficient approach to acyoxy-substituted arenes with a broad range of functional group tolerance. Furthermore, this reaction system could be further applied to the preparation of polyfunctional naphthylenes.