Palladium-Catalyzed Annulation Reaction of Bay-Iodobiphenyls with Maleimides to Access 9,10-Phenanthrenedicarboximides.

A palladium-catalyzed annulation reaction of bay-iodobiphenyls with maleimides was developed. This approach allows for the efficient synthesis of a variety of 9,10-phenanthrenedicarboximides, particularly polyalkoxy-substituted 9,10-phenanthrenedicarboximides with potential liquid-crystalline properties. Research findings indicate that the resulting product, -hexyl-2,3,6,7-tetrakis(hexyloxy)-9,10-phenanthrenedicarboximide, exhibits promising, good liquid-crystalline properties.

Palladium-Catalyzed Annulative π-Extension of Bay-Iodinated Triphenylenes to Access Polycyclic Aromatic Compounds.

A palladium-catalyzed annulative π-extension reaction of bay-iodinated triphenylenes with aryl iodides/-chloroaromatic carboxylic acids was developed. This approach enabled the synthesis of diverse polycyclic aromatic compounds, including dibenzo[,]tetracenes, azadibenzo[,]tetracenes, and tribenzo[,,]coronenes. Initial studies indicate that the resulting product, 2,3,8,9,14,15-hexakis(decyloxy)tribenzo[,,]coronene, exhibits good liquid-crystalline properties.

Asymmetric Total Synthesis of Hasubanan Alkaloids: Periglaucines A-C, N,O-Dimethyloxostephine and Oxostephabenine.

We report herein the asymmetric total synthesis of periglaucines A-C, N,O-dimethyloxostephine and oxostephabenine. The key strategies used include: 1) a Rh -catalyzed regio- and diastereoselective Hayashi-Miyaura reaction to connect two necessary fragments; 2) an intramolecular photoenolization/Diels-Alder (PEDA) reaction to construct the highly functionalized tricyclic core skeleton bearing a quaternary center; 3) a bio-inspired intramolecular Michael addition and transannular acetalization to generate the aza[4.4.

Palladium-catalyzed annulative π-extension of -halobiphenyls with -chloropyridinecarboxylic acids to access azatriphenylenes.

A palladium-catalyzed bay-region annulative π-extension reaction of -halobiphenyls with -chloropyridinecarboxylic acids was developed. The reaction was carried out with a 1 : 1 ratio of substrates. A variety of azatriphenylene derivatives could be synthesized by this approach.

Recent advances in the total synthesis of gracilamine.

Gracilamine belongs to the Amaryllidaceae alkaloid group and has a unique five-ring skeleton. Its scarcity in plants limits biological studies on it. A number of synthetic chemists have carried out the total synthesis of gracilamine in the past few years.

Total Synthesis of (-)-Xestosaprol N and O.

The first total synthesis of (-)-xestosaprol N and O is described. This synthetic work features a convergent strategy: (1) a Pd-catalyzed arylation followed by cyclization to build a naphthalene fragment (ring C, D); (2) utilization of (-)-quinic acid to construct the chiral hydroxyl group at C-2; (3) a substrate controlled intramolecular Heck reaction to construct a quaternary carbon center (ring B); (4) introduction of a hypotaurine moiety at a late stage to furnish the E ring.

Ti(Oi-Pr)-promoted photoenolization Diels-Alder reaction to construct polycyclic rings and its synthetic applications.

Stereoselective construction of polycyclic rings with all-carbon quaternary centers, and vicinal all-carbon quaternary stereocenters, remains a significant challenge in organic synthesis. These structures can be found in a wide range of polycyclic natural products and drug molecules. Here we report a Ti(Oi-Pr)-promoted photoenolization/Diels-Alder (PEDA) reaction to construct hydroanthracenol and related polycyclic rings bearing all-carbon quaternary centers.

Total synthesis of gracilamine.

The total synthesis of gracilamine, a pentacyclic Amaryllidaceae alkaloid, was achieved from simple building blocks. The synthesis features a mild photo-Nazarov reaction, intramolecular 1,4-addition, and an intramolecular Mannich reaction. This approach not only confirms the C6 stereochemistry of natural gracilamine, and also provides a novel solution to prepare its derivatives and structurally related natural products.

The photo-Nazarov reaction: scope and application.

The reaction conditions and scope of the photo-Nazarov reaction of aryl vinyl ketones were investigated. In contrast to the conventional acid-catalyzed methods, this photolytic electrocyclization proceeds in the neutral or basic conditions. Irradiating substrates bearing various aromatic rings, acid-sensitive groups, cyclohexenyl, cycloheptenyl, and unsaturated pyran with UV-light (254 nm) smoothly yielded hexahydrofluorenones and related structures.

A photo-induced C-O bond formation methodology to construct tetrahydroxanthones.

A metal-free, photo-induced C-O bond formation methodology was developed to construct tetrahydroxanthones. This mild and efficient methodology was based on intramolecular oxygen trapping of the reactive species produced by photolytic activation of a C-Cl bond. We believe this method could be used in the synthesis of related xanthone-type natural products.

Biomimetic synthesis of equisetin and (+)-fusarisetin A.

(+)-Fusarisetin A belongs to a group of acyl tetramic acid natural products that show potential anticancer activity. Equisetin, a biogenetically related acyl tetramic acid, contains the basic skeleton of (+)-fusarisetin A. We proposed that equisetin and (+)-fusarisetin A share a biosynthetic pathway that starts with naturally occurring (S)-serine and an unsaturated fatty acid.

Fluoradenes via palladium-catalyzed intramolecular arylation.

A novel approach towards 7b-aryl-indeno[1,2,3-jk]fluorene based on a nitrogen-containing core is reported. The acid-promoted Friedel-Crafts reaction of 9-(2-bromophenyl)-9-fluorenol with carbazole, triphenylamine or triindole afforded 9-(2-bromophenyl)fluorenyl-carbazole, -triphenylamine and -triindole derivatives, which were subsequently converted to 7b-aryl-fluoradenes via palladium-catalyzed intramolecular C-H direct arylation as a key step.