Haibing Guo

Organocatalytic 1,3-dipolar cycloaddition reactions of ketones and azides with water as a solvent

We reported an enamine catalyzed strategy to fully promote a 1,3-dipolar cycloaddition to access a vast pool of substituted 1,2,3-triazoles with water as the only solvent.

De Novo Asymmetric Synthesis of Anthrax Tetrasaccharide and Related Tetrasaccharide

A de novo asymmetric approach to the natural product anthrax tetrasaccharide 1 and an analogue 2 with an anomeric hexyl azide group has been developed from acetylfuran. The construction of the tetrasaccharide was achieved by a traditional [3 + 1] glycosylation strategy. An iterative diastereoselective palladium-catalyzed glycosylation, Luche reduction, diastereoselective dihydroxylation, and regioselective acylation were employed for the assembly of the L-rhamno-trisaccharide building block. The anthrose building block also required a palladium-catalyzed azide allylation and a triflate inversion to set the gluco-stereochemistry in addition to Luche reduction and dihydroxylation.

De Novo Asymmetric Synthesis of 8a-epi-Swainsonine

An enantioselective and diastereocontrolled approach to 8a-epi-d-swainsonine has been developed from achiral furfural. The key step to this synthesis was a one-pot procedure for the hydrogenolytic removal of two protecting groups and two intramolecular reductive amination reactions. The absolute stereochemistry was introduced by asymmetric Noyori reduction of furfuryl ketone. This route relies on diastereoselective palladium-catalyzed glycosylation to install the anomeric bond, and Luche reduction, diastereoselective dihydroxylation to set up the manno-stereochemistry of the indolizidine precursor.

Formal total synthesis of RK-397 via an asymmetric hydration and iterative allylation strategy.

A formal total synthesis of the oxopentaene macrolide antibiotic RK-397 has been achieved. Nine stereocenters were established by a combination of allylation and our asymmetric hydration reactions and a 1,5 anti-selective aldol reaction. The synthesis proceeded in 19 steps from simple achiral conjugated dienoates.

An enantioselective cascade reaction between α,β-unsaturated aldehydes and malonic half-thioesters: a rapid access to chiral δ-lactones.

We disclose a novel efficient enantioselective organocatalytic cascade reaction for the preparation of δ-lactones in good to excellent yields (69-93%) and with high to excellent enantioselectivities (88-96% ee).

A highly enantioselective Michael reaction between α,β-unsaturated ketones and malonic acid half-thioesters

We disclose herein an efficient enantioselective organocatalytic Michael reaction between α,β-unsaturated ketones and malonic acid half thioesters (MAHTs). The reactions are catalyzed by a primary amine to generate Michael addition products in good to excellent yields (62–87%) with high to excellent enantioselectivities (80–98%).

An extremely stable and highly active periodic mesoporous Lewis acid catalyst in water-medium Mukaiyama-aldol reaction

A periodic mesoporous Lewis acid catalyst ((OTf)2Sc-SO3-Ph-PMO) was synthesized through chelating scandium triflate (Sc(OTf)3) with sodium benzenesulfonate-functionalized periodic mesoporous silica (PhSO3Na-Ph-PMO). Compared with homogeneous catalyst Sc(OTf)3 and mesoporous SBA-15-supported scandium triflate catalyst ((OTf)2Sc-SO3-Ph-SBA-15), it exhibited superior catalytic activity and selectivity in water-medium Mukaiyama-aldol reaction. Hydrophobicity tests and substrate adsorption experiments demonstrated that its unique catalytic performance was related to the combined advantage of mesoporosity and hydrophobic microenvironment, which effectively stabilized and concentrated the substances as well as decreased intrinsic mass transfer resistance. Noted that the periodically arranged Lewis acids in the mesoporous silica framework inhibited the active sites leaching, leading to its high catalytic recyclability with almost unchanged catalytic efficiency for more than 10 times in water media.

Silylated organometals: a family of recyclable homogeneous catalysts

A general strategy has been developed to synthesize a family of silylated organometals (M-PPh2-TS and DPEN-Ru-PPh2-Ts, M = Pd2+, Rh+, Pt2+, Ir+, or Ru2+, PPh2-Ts = PPh2CH2CH2Si(OEt)3), DPEN = (1R,2R)-1,2-diphenylethylenediamine). They can act as homogeneous catalysts with high efficiencies in various organic reactions using THF, CH2Cl2 or toluene as the reaction medium. After reaction, they could be thoroughly settled down by adding pentane and then used repeatedly owing to the complete catalyst recovery and good preservation of the catalyst structure. This is particularly important due to the increasing concerns regarding the cost, toxicity and limited availability of these nonrenewable transition metals.

Cu-catalyzed aerobic oxidative C–CN bond cleavage of benzyl cyanide for the synthesis of primary amides

An efficient method via copper-catalyzed aerobic oxidative amidation of benzyl cyanide for primary amides is successfully developed. Using readily available NH4Cl as a nitrogen source and Cu/O2 as a catalytic oxidation system offers new opportunities for C–CN bond cleavage and primary amide bond formation.

De Novo Asymmetric Synthesis and Biological Analysis of the Daumone Pheromones in Caenorhabditis elegans and in the Soybean Cyst Nematode Heterodera glycines

The de novo asymmetric total syntheses of daumone 1, daumone 3 along with 5 new analogs are described. The key steps of our approach are: the diastereoselective palladium catalyzed glycosylation reaction; the Noyori reduction of 2-acetylfuran and an ynone, which introduce the absolute stereochemistry of the sugar and aglycon portion of daumone; and an Achmatowicz rearrangement, an epoxidation and a ring opening installing the remaining asymmetry of daumone. The synthetic daumones 1 and 3 as well as related analogs were evaluated for dauer activity in C. elegans and for effects on hatching of the related nematode H. glycines. This data provides additional structure activity relationships (SAR) that further inform the study of nematode signaling.