Yong-Qiang Zhang

Organocatalytic Asymmetric Direct C sp 3H Functionalization of Ethers: A Highly Efficient Approach to Chiral Spiroethers

and pharmaceuticals, is an important endeavor in organic synthesis. Tremendous efforts have been made during the past few years toward developing methods for the synthesis of spiroethers, although of the methods developed, many involve multiple steps and only a few are enantioselective. Therefore, the development of methods that are highly efficient, catalytic, and enantioselective is still required. The direct and selective functionalization of inactive Csp3 H bonds is not only a significant and actively studied subject in fundamental organic chemistry, it is also becoming a practical method for organic synthesis because of its atomand step economy. Among the reported transformations, intramolecular redox processes for the direct functionalization of Csp3 H bonds that are a to heteroatoms are important for the synthesis of structurally diverse amine and ether derivatives. Furthermore, since the pioneering work of Kim and co-workers, there have many good results reported in the area of intramolecular redox processes for the direct enantioselective Csp3 H functionalization at positions a to nitrogen atoms. However, examples of the corresponding enantioselective reaction of ethers are scarce. In 2005, Sames and co-workers. reported that Sc(OTf)3 or BF3·Et2O could initiate a direct functionalization of Csp3 H bonds of cyclic ethers 1 to give racemic spiroethers 2’ (Scheme 1). This

Au(I)-catalyzed rearrangement reaction of propargylic aziridine: synthesis of trisubstituted and cycloalkene-fused pyrroles.

A rearrangement reaction of propargylic aziridine, catalyzed by PPh(3)AuCl/AgOTf, forming trisubstituted and cycloalkene-fused pyrroles is described which involves an unusual tandem cyclization/ring-opening/Wagner-Meerwein process. The unique structures of the products demonstrated its potential applications for synthesizing structurally diverse alkaloids.

Regiodivergent annulation of alkynyl indoles to construct spiro-pseudoindoxyl and tetrahydro-β-carbolines.

Regiodivergent annulations of 3-phenoxy alkynyl indoles have been developed and tuned by protective groups through gold catalysis. With electron-donating protective groups, the substrate followed a C3-selective annulation and gave structurally interesting tetrahydro-β-carboline derivatives possessing potential bioactivity. Using electron-withdrawing protective groups, the substrate underwent a C2-selective annulation and afforded the structurally useful spiro-pseudoindoxyl found in natural indole alkaloids. Notably, an interesting and unusual 1, 2-migration of the phenoxy group was found in the C3-selective process.

Total Synthesis of (±)-Maistemonine, (±)-Stemonamide, and (±)-Isomaistemonine

A full account of the total synthesis of (±)-maistemonine, (±)-stemonamide, and (±)-isomaistemonine is presented. Two approaches have been developed to construct the basic pyrrolo[1,2-a]azepine core of the Stemona alkaloids, featuring a tandem semipinacol/Schmidt rearrangement of a secondary azide and a highly stereoselectively desymmetrizing intramolecular Schmidt reaction, respectively. To build the common spiro-γ-butyrolactone, a new protocol was carried out by utilizing an intramolecular ketone-ester condensation as the key transformation. The vicinal butyrolactone moiety of (±)-maistemonine was stereoselectively introduced via a one-pot procedure involving the epimerization at C-3 and carbonyl allylation/lactonization. Moreover, (±)-stemonamide was divergently synthesized from a common intermediate, and (±)-isomaistemonine was obtained via the epimerization of (±)-maistemonine at C-12.

Palladium-Catalyzed Cascade Process To Construct 1,2,5-Trisubstituted Pyrroles

A novel palladium-catalyzed cascade allylic amination/intramolecular hydroamination/isomerization process of protected enynol 1 and primary amine 2 has been explored, which constructs the important 1,2,5-trisubstituted pyrroles. This transformation offers an alternative synthetic methodology capable of generating substituted pyrroles in a straightforward way.

Tandem reactions of cis-2-acyl-1-alkynyl-1-aryl cyclopropanes tuned by gold(I) and silver(I) catalysts: efficient synthesis of pyran-fused indene cores and 2,4,6-trisubstituted phenols

Tandem reactions of cis-2-acyl-1-alkynyl-1-aryl cyclopropanes tuned by gold(i) and silver(i) catalysts are described, which afford selectively the key pyran-fused indene cores and the 2,4,6-trisubstituted phenols in good yields, respectively.

Gold-catalyzed reaction of enynols by a dimerization–fragmentation process: an expeditious assembly of enyne molecular architecture

Intermolecular condensation reaction of 1,3,5-triarylenynols catalyzed by gold as Lewis acid was reported for the first time; the products with unique structures have potential applications in materials chemistry, and tandem reaction product has been used to detect mercury ions as an organic molecular probe.