Xiaolong Wan

Pd(OAc)(2) catalyzed olefination of highly electron-deficient perfluoroarenes.

An efficient, Pd(OAc)(2) catalyzed method for direct olefination of highly electron-deficient perfluoroarenes was developed. The reaction scope includes a series of activated and nonactivated alkenes in moderate to high yields with moderate to high regio- and stereoselectivities.

Highly Enantioselective Bromocyclization of Tryptamines and Its Application in the Synthesis of (−)‐Chimonanthine

A shorter path: A highly enantioselective bromocyclization of tryptamine has been developed using an anionic chiral phase-transfer catalyst. This method provides a direct approach for preparing chiral 3-bromopyrroloindoline from tryptamine, which enables a four-step enantioselective synthesis of (-)-chimonanthine. PG=protecting group.

Cobalt-catalyzed enantioselective hydroboration of 1,1-disubstituted aryl alkenes.

We report the synthesis of cobalt complexes of novel iminopyridine-oxazoline (IPO) ligands and their application to the asymmetric hydroboration of 1,1-disubstituted aryl alkenes. The new catalysts afforded α-alkyl-β-pinacolatoboranes with exclusive regioselectivity in high yields with up to 99.5% ee. Furthermore, we have applied this method to an efficient synthesis of naproxen.

Highly Asymmetric Bromocyclization of Tryptophol: Unexpected Accelerating Effect of DABCO-Derived Bromine Complex

Highly asymmetric bromocyclization of tryptophol by using chiral anionic phase-transfer catalyst and DABCO-derived brominating reagent is described. Optimization of the reaction conditions revealed that the reaction rate was accelerated together with improvement of enantioselectivity by addition of catalytic DABCO-derived brominating reagent. From tryptophol, 3-bromofuroindoline could be directly obtained in excellent enantioselectivities by employing this novel methodology.

Enantioselective Synthesis of Cyclopropanes That Contain Fluorinated Tertiary Stereogenic Carbon Centers: A Chiral α-Fluoro Carbanion Strategy†

Chiral transfer: the fluorinated sulfoximine (see scheme; Ts=p-toluenesulfonyl) was synthesized and used as the first chiral fluoromethylenation reagent for the synthesis of cyclopropanes that contain fluorinated tertiary stereogenic carbon centers in good yields, good diastereoselectivity, and excellent enantioselectivity.

Novel hybrids of optically active ring-opened 3-n-butylphthalide derivative and isosorbide as potential anti-ischemic stroke agents.

In search of novel anti-ischemic stroke agents with higher potency than a known drug 3-n-butylphthalide (NBP), a series of hybrids ((S)- and (R)-5a-f) from optically active ring-opened NBP derivative and isosorbide were synthesized for evaluating their anti-ischemic stroke activity. Compound (S)-5e displayed the strongest activity in inhibiting the adenosine diphosphate (ADP) and arachidonic acid (AA)-induced platelet aggregation in vitro, with 10.0- and 8.4-fold more effectiveness than (S)-NBP, respectively. Furthermore, (S)-5e was stable in artificial gastrointestinal fluids and could penetrate the blood-brain barrier (BBB) with an appreciate lipid/water partition coefficient relative to (S)-NBP. More importantly, oral treatment with (S)-5e protected from acute thrombosis and inhibited the ischemia/reperfusion-related brain injury in animals. Our findings suggest that (S)-5e may be promising for further evaluation for the intervention of ischemic stroke.

Total Synthesis of (-)-Conolutinine.

The first enantioselective synthesis of (-)-conolutinine was achieved in 10 steps. The synthesis featured a catalytic asymmetric bromocyclization of tryptamine to forge the tricycle intermediate. Hydration of an alkene catalyzed by Co(acac)2 was also employed as a key step to diastereoselectively introduce the tertiary alcohol moiety. The absolute configuration of (-)-conolutinine was established to be (2S,5aS,8aS,13aR) based on this asymmetric total synthesis.

Enantioselective Construction of Trifluoromethoxylated Stereogenic Centers by a Nickel‐Catalyzed Asymmetric Suzuki–Miyaura Coupling of Secondary Benzyl Bromides

Trifluoromethoxy-substituted stereogenic centers can be constructed with high enantioselectivity by a nickel-catalyzed Suzuki-Miyaura coupling of readily available α-bromobenzyl trifluoromethyl ethers with a variety of aryl pinacol boronates. The coupling proceeds under mild reaction conditions, and a variety of common functional groups, such as fluoride, chloride, bromide, ester, enolizable ketone, nitro, cyano, amino, and vinyl moieties, were well tolerated. Furthermore, the reaction can be easily scaled up to gram quantities without a decrease in enantioselectivity.

Enantioselective Bromo-oxycyclization of Silanol

Relying on the nucleophilicity of silanol for building up silicon-incorporated scaffold with an enantiopure tetrasubstituted carbon center remains elusive. In this report, asymmetric bromo-oxycyclization of olefinic silanol by using chiral anionic phase-transfer catalyst is described. This protocol provided a facile entry to a wide arrangement of enantiopure benzoxasilole in moderate to excellent enantioselectivities depending on the unique reactivity of bromine/N-benzyl-DABCO complex.

Copper‐Catalyzed Highly Stereoselective Trifluoromethylation and Difluoroalkylation of Secondary Propargyl Sulfonates

It is challenging to stereoselectively introduce a trifluoromethyl group (CF3 ) into organic molecules. To date, only limited strategies involving direct asymmetric trifluoromethylation have been reported. Herein, we describe a new strategy for direct asymmetric trifluoromethylation through the copper-catalyzed stereospecific trifluoromethylation of optically active secondary propargyl sulfonates. The reaction enables propargylic trifluoromethylation with high regioselectivity and stereoselectivity. The reaction could also be extended to stereospecific propargylic difluoroalkylation. Transformations of the resulting enantiomerically enriched fluoroalkylated alkynes led to a variety of chiral fluoroalkylated compounds, thus providing a useful protocol for applications in the synthesis of fluorinated complexes.