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ABSTRACT: Highly diastereoselective asymmetric synthesis of chiral aziridine-2-carboxylic esters is reported for 20 examples with good yields (51-87%) and excellent diastereoselectivities (>99 : 1 dr for most cases). The modified N-phosphonyl imines have proven to be superior to previous imine auxiliaries for the aza Darzens reaction by using a secondary isopropyl group to replace the primary benzyl group for N,N-diamino protection. In the meanwhile, a special operation by slowly adding the pre-cooled imine solution at -78 °C into the preformed β-bromo lithium enolate mixture at this temperature in the presence of 4 Å molecular sieves was found to be crucial in terms of yields and diastereoselectivity. The present method can provide an easy and general access to β-hydroxy α-amino acids and other important amino building blocks.
Organic & Biomolecular Chemistry 04/2013; · 3.70 Impact Factor
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ABSTRACT: The asymmetric catalytic aza-Morita-Baylis-Hillman (aza-MBH) reaction of isatin-derived ketimines with MVK has been established by using chiral amino and phosphino catalysts. The reaction resulted in biomedically important 3-substituted 3-amino-2-oxindoles in good yields (>80% for most cases) and with excellent enantioselectivity (90-99% ee). Twenty-eight cases assembled with chiral quaternary stereogenic centers have been examined under convenient systems.
Organic & Biomolecular Chemistry 03/2013; 11(12):1921-4. · 3.70 Impact Factor
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ABSTRACT: Highly selective four-component domino multicyclizations for the synthesis of new fused acridines and azaheterocyclic skeletons have been established by mixing common reactants in isobutyric acid under microwave irradiation. The reactions proceeded at fast rates and were conducted to completion within 20-30 min. Up to seven new chemical bonds, four rings, and four stereocenters were assembled in a convenient one-pot operation. The resulting hexacyclic and pentacyclic fused acridines and their stereochemistry have been fully characterized and determined by X-ray structural analysis.
Organic Letters 03/2013; · 5.86 Impact Factor
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ABSTRACT: A new chiral (Rs)-2-phenyl-2-propyl sulfinamide has been designed and synthesized; its derived aldimines and ketimines have been applied for asymmetric addition reaction with allylmagnesium bromide. The reaction was conveniently performed at room temperature to give a series of homoallylic amines in high yields (up to quant) and diasteroselectivity (up to >99 % de). The pure products were obtained by relying on Group-Assisted Purification (GAP) chemistry to avoid traditional purification methods of column chromatography and recrystallization. The conversion of disulfide to (Rs)-thiosulfinate was also confirmed to be of the GAP chemistry in which washing crude product can generate pure enantiomer. The absolute stereochemistry has been determined by X-ray analysis.
The Journal of Organic Chemistry 03/2013; · 4.45 Impact Factor
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ABSTRACT: 1.0 % Mol of K3PO4•3H2O was found to catalyze aminohalogenation reaction of nitrostyrenes with N,N-dibromo-tert-butylcarbamate (t-Boc-NBr2) in dichloroethane system. Good to excellent yields and complete regioselectivity have been achieved by taking advantage of the GAP work-up without using traditional purification techniques such as column chromatography and recrystallization. New mechanism was proposed involving radical and ionic catalytic cycles and an intramolecular migration.
The Journal of Organic Chemistry 01/2013; · 4.45 Impact Factor
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ABSTRACT: A novel multicomponent strategy for the efficient synthesis of tricyclic pyrrolo[1,2-a]quinolines has been described. The bond-forming efficiency, accessibility and generality of this synthesis make it highly attractive to assemble tri-heterocyclic scaffolds.
Chemical Communications 11/2012; · 6.17 Impact Factor
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ABSTRACT: An intramolecular Pauson-Khand type cycloaddition reaction of ene-vinylidenecyclopropanes with carbon monoxide has been established by using [Rh(COD)Cl](2) as the catalyst. The reaction was found to be highly efficient in solvents of 1,2-dichloroethane and 1,1,2,2-tetrachloroethane to give excellent yields of 90-99%. The reaction provides easy access to a series of fused 6,5-ring structures containing spiro-cyclopropane units that are useful for drug design and development. A mechanism of this cycloaddition process has been proposed accounting for structures of resulting products that were unambiguously assigned by X-ray diffractional analysis.
Organic Letters 10/2012; · 5.86 Impact Factor
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ABSTRACT: Efficient three-component domino strategies for the synthesis of multifunctionalized tetracyclic indeno[1,2-b]indole derivatives with different substituted patterns have been established successfully. The first pathway involves a novel sequential methyl migration, aromatization, and esterification, while a second reaction in HOAc leads to compounds 6 with high syn diastereoselectivity. Both reactions showed attractive features including mild conditions, convenient one-pot operation, short reaction times of 15-32 min, and excellent regio- and/or stereoselectivity.
Organic Letters 10/2012; 14(20):5210-3. · 5.86 Impact Factor
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ABSTRACT: New three-component domino reaction providing divergent approaches to multifunctionalized fused pyrroles with different substituted patterns have been established (40 examples). The direct C(sp(3))-N bond formation was achieved through intermolecular allylic amination in a one-pot operation, and N-arylation of amines was realized by varying N-amino acid enaminones. The reaction is easy to perform simply by mixing three common reactants in acetic acid under microwave heating. The reaction proceeds at fast rates and can be finished within 30 min, which makes workup convenient to give good chemical yields.
The Journal of Organic Chemistry 08/2012; 77(17):7497-505. · 4.45 Impact Factor
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ABSTRACT: AIMS: To design and synthesize novel N-(1-phenyl-2,3-dihydroxypropyl)arachidonylamides and evaluate their analgesic and anti-inflammatory potential. MAIN METHODS: The murine macrophage cell line RAW 264.7 has been widely used as a model for inflammatory responses in vitro. Our model consists of cultured monolayers of RAW 264.7 cells in which media concentrations of 15-deoxy-Δ(13,14)-PGJ(2) (PGJ) are measured by ELISA following LPS (10ng/ml) stimulation and treatment with 0.1, 0.3, 1.0, 3.0 and 10μM concentrations of the compounds. KEY FINDINGS: Our data indicate that several of our compounds have the capacity to increase production of PGJ and may also increase the occurrence of programmed cell death (apoptosis). SIGNIFICANCE: Thus these agents are potential candidates for the therapy of conditions characterized by ongoing (chronic) inflammation and its associated pain.
Life sciences 07/2012; · 2.56 Impact Factor
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ABSTRACT: New three-component domino reactions have been discovered. The reactions are easy to perform (see scheme; MW=microwave irradiation) and proceed with fast rates, which makes work-up convenient. Most of the multiple stereocenters and the geometry are controlled well. The stereochemistry has been unequivocally determined by X-ray structural analysis.
Chemistry 07/2012; 18(32):9823-6. · 5.93 Impact Factor
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ABSTRACT: The combination of benzamide and NCS was found to be an efficient nitrogen/halogen source for aminohalogenation of β-nitrostyrenes.
The reaction was convenient to carry out by using 4-dimethylaminopyridine as the catalyst, resulting in vicinal dichlorinated
haloamino nitroalkanes with opposite regiochemistry to that generated from other electron-deficient olefins observed previously.
The reaction proceeded smoothly at room temperature with good yields and excellent regioselectivities. A mechanism involving
a chloronium intermediate was proposed to explain the resulting regiochemistry. The current system explored a new type of
nitrogen sources for aminohalogenation of functionalized olefins.
Kwywordsaminohalogenation-benzamide-β-nitrostyrenes-DMAP-haloamides
Science China-Chemistry 04/2012; 53(9):1946-1952. · 1.02 Impact Factor
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ABSTRACT: Aminohalogenation reaction of β-nitrostyrenes with N-halosuccinimides (N-chloro and N-bromosuccinimides) has been successfully conducted by using nickel acetate as a catalyst in the presence of potassium carbonate
and succinimide as co-additives. The reaction was easily performed at room temperature under nitrogen gas protection to give
dihalorinaed haloamino products in good to excellent yields (60%–98%). The structure has been confirmed by X-ray crystal structure
analysis.
Science China-Chemistry 04/2012; 53(1):140-146. · 1.02 Impact Factor
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ABSTRACT: Asymmetric Mannich-type reaction of hydrazones with difluoroenoxysilanes using chiral zinc(II)-imidazoline-phosphine complexes as catalysts have been established, giving the corresponding adducts in good to excellent enantioselectivity and chemical yields under mild conditions.
Organic & Biomolecular Chemistry 04/2012; 10(13):2509-13. · 3.70 Impact Factor
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Organic & Biomolecular Chemistry 03/2012; · 3.70 Impact Factor
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ABSTRACT: Efficient domino approaches for the synthesis of multifunctionalized tricyclic fused pyrroles and dibenzo[b,e][1,4]diazepin-1-ones have been established. The reaction pathways were controlled by varying enaminones with different substituted patterns to give a series of new fused pyrroles and dibenzo[b,e][1,4]diazepin-1-ones selectively. The complete anti diastereoselectivity was achieved for the first reaction.
Organic Letters 02/2012; 14(3):700-3. · 5.86 Impact Factor
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ABSTRACT: A novel multi-component reaction for the synthesis of polyfunctionalized indoles and bis-indoles has been established. The reaction pathways were controlled by varying enamines with different substitution patterns to give polyfunctionalized indoles and bis-indoles selectively. The reaction proceeds at a fast speed within 15-30 min with water as the major byproduct, which makes work-up convenient.
Chemical Communications 01/2012; 48(6):808-10. · 6.17 Impact Factor
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ABSTRACT: Microwave-assisted three-component reaction has been established for the regioselective synthesis of benzo[f]azulen-1-ones. The reaction was performed in aqueous media under microwave irradiation by using readily available and inexpensive starting materials. A total of 38 examples were examined to show a broad substrate scope and good overall yields (70-89%). The present new synthesis shows attractive green chemistry characteristics, such as the use of water as reaction media, concise one-pot conditions, short reaction periods (7-24 min), easy work-up/purification and reduced waste production without the use of any strong acids or metal promoters.
Tetrahedron 06/2011; 67(25):4485-4493. · 3.03 Impact Factor
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ABSTRACT: An efficient methodology for the synthesis of highly functionalized pyridine derivatives starting from readily available common reactants has been developed under microwave irradiation and solvent-free conditions. The new domino reaction enables successful assembly of five new σ bonds including two C-N bonds in a one-pot operation. A new mechanism has been proposed, which involves a novel reaction and sequence consisting of deprotonation-imine formation-anionic carbonyl addition.
Organic & Biomolecular Chemistry 06/2011; 9(11):4025-8. · 3.70 Impact Factor
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ABSTRACT: A new multicomponent domino reaction for rapid and regioselective synthesis of highly functionalized benzo[h]pyrazolo[3,4-b]quinolines has been established. The reaction can be conducted by using readily available and inexpensive substrates under microwave irradiation within short periods of 10-26 min. Good to excellent chemical yields (61-91%) and complete regioselectivity have been achieved for 22 examples. Tedious work-up procedure can be avoided due to the direct precipitation of products from the reaction solution. The resulting benzoquinolines have been readily converted into quinoxaline-fused benzo[h]isoxazolo[5,4-b]quinoline analogues by treating with benzene-1,2-diamine under microwave irradiation. The structural assignment has been ambiguously confirmed by X-ray analysis. A new mechanism has been proposed for this new multicomponent domino process.
Organic & Biomolecular Chemistry 03/2011; 9(10):3834-8. · 3.70 Impact Factor
