HYPERBRANCHED CONJUGATIVE MACROMOLECULES CONSTRUCTED FROM TRIPLE-BOND BUILDING BLOCKS

Polycyclotrimerization and polycoupling of acetylenic monomers respectively furnish hyperbranched polyarylenes and polyynes with high molecular weights(up to 1×10~6)in high yields(up to 99.9%).The polymers possess low intrinsic viscosities and high thermal stabilities,losing little of their weights when heated to＞400℃.Upon pyrolysis at＞800℃,the polymers graphitize with high char yields(up to 86%).Hyperbranched polyarylenes efficiently emit deep-blue to blue-green lights with fluorescence quantum yields up to 98% and strongly attenuate intense laser pulses with optical power-limiting performances superior to that of C_(60),a well-known optical lirniter.Poly(alkenephenylenes),poly(aroylarylenes)and polyynes are readily cross-linkable by UV irradiation,serving as excellent photoresist materials for the generation of patterns with nanometer resolution.Thin films of hyperbranched polyynes exhibit very high refractive indexes(n up to 1.86).The internal and terminal acetylene moieties of the polyynes readily form complexes with cobalt carbonyls,which can be transformed into soft ferromagnetic ceramics with high magnetic susceptibilities(M_s up to ca.118 emu/g)and near-zero magnetic losses.     

Oxazaborolidinium ion-catalyzed cyclopropanation of α-substituted acroleins: enantioselective synthesis of cyclopropanes bearing two chiral quaternary centers

A catalytic synthetic route to highly functionalized chiral cyclopropane derivatives was developed by Michael-initiated cyclopropanation of α-substituted acroleins with aryl- and alkyl diazoacetates. In the presence of chiral (S)-oxazaborolidinium cation 1b as a catalyst, the reaction proceeded in high yield (up to 93%) with high to excellent diastereoselectivity (up to 98% de) and enantioselectivity (up to 95% ee).     

Rhodium-catalyzed Michael addition of arylboronic acids to 3-alkylenyloxindoles: asymmetric synthesis of functionalized oxindoles

The rhodium-catalyzed diastereo- and enantioselective Michael addition of arylboronic acids to 3-alkylenyloxindoles has been developed with (R)-binap as a ligand. A wide variety of the desired functionalized oxindoles are smoothly obtained in high yields (up to 99%) with high enantioselectivities (up to 92% ee) and good diastereoselectivities (up to 82:18).     

Asymmetric hydrogenation of quinolines with high substrate/catalyst ratio

The chiral diphosphinite ligand derived from (R)-1,1'-spirobiindane-7,7'-diol has been found to be highly effective in the Ir-catalyzed asymmetric hydrogenation of quinolines with high substrate/catalyst ratio (up to 5000) and high enantioselectivity (up to 94% ee).     

SYNTHESIS OF HYPERBRANCHED CONJUGATIVE POLY（ARYLENEETHYNYLENE）S BY ALKYNE POLYCYCLOTRIMERIZATION

A series of new hyperbranched poly(aryleneethynylene)s are synthesized by the copolycyclotrimerizations oftetraynes(Ⅰand Ⅱ)with aliphatic monoynes(A-C)catalyzed by tantalum-,niobium-,and cobalt-based catalysts.All thereactions proceed smoothly and soluble polymers of high molecular weights(M_w up to 3.8×10~4)are obtained in high yields(up to 97%).     

Chiral squaramide-catalyzed highly diastereo- and enantioselective direct Michael addition of nitroalkanes to nitroalkenes

An efficient highly diastereo- and enantioselective direct Michael addition of nitroalkanes to nitroalkenes catalyzed by chiral squaramide catalyst has been developed. This organocatalytic reaction with a low catalyst loading (2 mol%) proceeded well to afford synthetically useful 1,3-dinitro compounds in high yields with high diastereoselectivities (up to 95 : 5 dr) and excellent enantioselectivities (up to 97% ee).     

Synthesis of 7,7’-Disubstituted BINAP and Their Application in Asymmetric Catalytic Reaction

The design of new chiral ligands plays a very important role in the development of transition metal catalyzed asymmetric synthesis. Many chiral diphosphine ligands have been prepared and applied in asymmetric catalytic reactions with excellent enantioselectivities. Among the chiral diphosphine ligands reported, BINAP was found to have been the widest application in the transition metal catalyzed reaction. Recently we have developed a novel oxovanadium (Ⅳ) complex catalyst for the oxidative …     

Organocatalytic functionalization of carboxylic acids: isothiourea-catalyzed asymmetric intra- and intermolecular Michael addition--lactonizations

Tetramisole promotes the catalytic asymmetric intramolecular Michael addition-lactonization of a variety of enone acids, giving carbo- and heterocyclic products with high diastereo- and enantiocontrol (up to 99:1 dr, up to 99% ee) that are readily derivatized to afford functionalized indene and dihydrobenzofuran carboxylates. Chiral isothioureas also promote the catalytic asymmetric intermolecular Michael addition-lactonization of arylacetic acids and α-keto-β,γ-unsaturated esters, giving anti-dihydropyranones with high diastereo- and enantiocontrol (up to 98:2 dr, up to 99% ee).     

Asymmetric substitutions of O-Boc-protected Morita-Baylis-Hillman adducts with pyrrole and indole derivatives

An efficient asymmetric substitution process of O-Boc-protected Morita-Baylis-Hillman adducts with various pyrrole and indole derivatives has been developed in the presence of (DHQD)(2)PYR in THF, affording the corresponding products in good to high yields (up to 99% yield) and moderate to high ee values (up to 92 and 96% ee) under mild conditions.     

New P,N-ferrocenyl ligands for rhodium-catalyzed hydroboration and palladium-catalyzed allylic alkylation

A set of nine new chiral P,N-ferrocenyl ligands for metal-catalyzed enantioselective reactions has been prepared. The rhodium-catalyzed hydroboration of styrene with catechol borane proceeded with high regioselectivity (up to 97:3) or with high enantioselectivity (up to 92% ee) depending on the catalyst. Good results were also obtained in the palladium-catalyzed asymmetric alkylation of 1,3-diphenylallylic systems (up to 94% ee).     

Efficient and stereoselective synthesis of beta-trifluoromethyl alpha,beta-unsaturated esters via iron(III) porphyrin-catalyzed olefination of ketones

beta-Trifluoromethyl alpha,beta-unsaturated esters were efficiently prepared by reactions of fluorine-containing ketones with diazo compounds via metalloporphyrin-catalyzed olefination in the presence of triphenylphosphine. The commercially available Fe(III)(TPP)Cl (TPP: tetraphenylporphyrin) is effective for catalyzing the olefination of a variety of trifluoromethyl ketones with different diazoacetate esters under mild conditions. The reactions proceeded with high yields (up to 95% isolated yield) and high stereoselectivity (up to 99% (E)-selectivity).     

Organocatalytic asymmetric cascade Michael/hemiketalization/retro-aldol reaction of 3-acetyl-oxindole with β,γ-unsaturated ketoesters catalyzed by bifunctional amino-squaramides

An unprecedented organocatalytic asymmetric Michael/Hemiketalization/retro-aldol cascade sequence catalyzed by bifunctional amino-squaramides is described. The corresponding adducts were generally obtained in high yields (up to 97%) with moderate diastereo- (up to 79:21 dr) and good enantioselectivities (up to 90% ee).     

Michael additions in water of ketones to nitroolefins catalyzed by readily tunable and bifunctional pyrrolidine-thiourea organocatalysts

An operationally trivial and environmentally benign procedure for direct Michael addition has been developed. The reaction of various ketones with nitroolefins can be performed in water to afford the corresponding nitro compounds in high yields in the presence of a pyrrolidine-thiourea organocatalyst at 35 °C. The reaction exhibits a high stereoselectivity, with high enantioselectivities (up to 99%) as well as diastereoselectivities (up to 99:1) being achieved under the optimal conditions.     

Enantioselective aldol reactions of α,β-unsaturated ketones with trifluoroacetophenone catalyzed by a chiral primary amine

Chiral primary amine catalyzed direct asymmetric aldol reactions of ketones with trifluoroacetophenone, afforded trifluoromethylated β-hydroxycarbonyl aldol products bearing a quaternary carbon stereogenic center in high yields (up to 93% yield) and with high to excellent enantioselectivities of up to 99% ee.     

Highly enantioselective alkynylation of aldehydes catalyzed by a new oxazolidine-titanium complex

The readily available and inexpensive new chiral oxazolidine in combination with Ti(O(i)Pr)(4) was found to catalyze the reaction of an alkynylzinc reagent with various types of aldehydes to generate chiral propargylic alcohols with high enantioselectivities (up to 95%) and excellent yields (up to 98%).     

Synthesis of geminal bisphosphonates via organocatalyzed enantioselective Michael additions of cyclic ketones and 4-piperidones

A Michael addition reaction of cyclic ketones and piperidones to a vinyl phosphonate is described. The reaction, catalyzed by chiral diamines, produced geminal γ-oxobisphosphonates in high yields (up to 92%) and very high ees (up to >99%). Disubstituted ketones gave drs of up to 8?:?92. The synthesis and characterization of several new compounds with potential biological activity is described.     

Calixarene-based chiral primary amine thiourea promoted highly enantioselective asymmetric Michael reactions of α,α-disubstituted aldehydes with maleimides

Calix[4]arene based chiral bifunctional thiourea-primary amines have been shown to act as effective catalysts for the Michael addition of aldehydes to maleimides for the first time. The corresponding adducts were generally obtained preferentially in (R)- or (S)-forms with high yields (up to 99%) and with high to excellent enantioselectivities (up to 98% ee).     

Enantioselective pinacol coupling reaction of aromatic aldehydes catalyzed by chiral vanadium complexes

The asymmetric pinacol coupling of aromatic aldehydes by chiral salan–vanadium complexes as effective catalysts is reported. Chiral 1,2-diols were obtained with high diastereoselectivities (up to 90/10) and moderate to high enantioselectivities (up to 82% ee). The possible mechanism of the pinacol coupling reaction is also discussed.     

Syntheses of chiral β- and γ-amino ethers, morpholines, and their homologues via nucleophilic ring-opening of chiral activated aziridines and azetidines

Lewis acid catalyzed quaternary ammonium salt mediated highly regioselective ring-opening of chiral activated aziridines and azetidines with alcohols to nonracemic β- and γ-amino ethers has been developed. The reaction mainly proceeds via an S(N)2 pathway, and the partial racemization of the starting substrate was effectively controlled by using quaternary ammonium salts. β- and γ-amino ethers are obtained with high enantio- and diastereospecificity (ee up to >99%, de up to 99%). The methodology was further extended to synthesize morpholines and their homologues with high enantiospecificity (ee up to 90%) when halo alcohols were employed as the nucleophiles.     

Upper rim-functionalized calix[4]arene-based l-proline as organocatalyst for direct asymmetric aldol reactions in water and organic media

The synthesis of upper rim-functionalized calix[4]arene-based l-proline was described, and its catalytic efficiency as organocatalyst for the enantioselective aldol reaction in water was investigated. The results showed that the nature of the hydrophobic cavity of calixarene is critical for catalytic activity in water. The products of the reaction between various ketones and aldehydes with anti-configuration were obtained in high yields (up to 94%) with high diastereo- (up to 95:5 dr) and enantioselectivities (up to 80% ee).