Synthesis of New Chiral C_2-Symmetrical Bis(oxazoline) Compounds

New chiral C_2-symmetrical bis(oxazoline) compounds bearing one isobutyl-, secbutyl-, benzyl- or isopropyl-substituent at the 4-position have been prepared and characterized.

Convenient Synthesis of Bis(oxazoline) Dicarboxylate Derivatives.

The synthesis of bis(oxazoline) dicarboxylate derivatives was investigated. Diethyl-aminosulfur trifluoride (DAST) was used as a convenient cyclization reagent in the synthesis of bis(oxazoline) dicarboxylate derivatives, which can not be obtained by the general method using MsCl and Et3N as dehydrating cyclization reagent.

Simple and Mild Syntheses of Optically Active 2-(N,N-Dialkylamino)oxazolines

Chloroamidinium salts and a-amino alcohols derived from commercially available tetraalkyl ureas and α-amino acids, respectively, can be used for the syntheses of optically active 2-（N,N-dialkylamino）oxazolines in moderate to excellent yields without any catalyst. It is a simple and mild method for the syntheses of optically active oxazolines

Syntheses and Configuration Inversion of Substituted Oxazolines

The present paper covers the simply and highly stereoselective syntheses of (α-S, 4S)-2-dichloromethyl-4, 5-dihydro-α-(4-nitrophenyl)-4-oxazolemethanol (4a), (α-S, 4S)-2-methyl-4, 5-dihydro-α-(4-nitrophenyl)-4-oxazolemethanol (4b), and (α-R, 4R)-2-dichloromethyl-4, 5-dihydro-α-[(4-methylsulfonyl)phenyl]-4-oxazolemethanol(4c) with good yields(80%—90%). A configuration inversion product, (1R, 2S)-2-dichloroacetamido-1-(4-nitrophenyl)-1, 3-propanediol (8), was obtained during our attempting to convert compound 4a into (4S, 5R)-2-(dichloromethyl)-4, 5-dihydro-5-(4-nitrophenyl)-4-oxazolemethanol(7).

Crystal Structure and Conformation of [1-(β-D-lyxofuranosyl)uracil]- 2'-spiro-5"-[4"-(S)-(diethoxyphosphinyl)-2"-oxazoline]

The title compound, C15H22N3O9P?H2O, Mr=455.36, crystallizes in orthorhombic, space group P212121, with a =9.193(2), b =14.681(3), c =15.201(3), V =2501(1)3, Z =4, Dx=1.474g/cm3, l(MoKa)=0.71073, m=0.1894mm-1, T=2991K, F(000)=960, R=0.061 and Rw=0.068 for 1899 observed reflections with I≥3s(I). The analysis results indicate that the title compound is of lyxo-configuration and the configuration at C4 is S. In the crystal state the molecule has anti conformation about glycosidic bond with the torsion angle 151.7? the sugar ring is puckered with C3-endo-C2-exo, and the conformation of the C4C5 bond is -sc.

Computational Insights into the Excited State Intramolecular Proton Transfer Reactions in Ortho-hydroxylated Oxazolines

Excited-state intramolecular proton transfer(ESIPT) reactions of three ortho-hydroxylated oxazolines, 2-(4,4-dimethyl-4,5-dihydro-oxazol-2-yl)-phenol(DDOP), 4-(4,4-dimethyl-4,5-dihydro-oxazol-2-yl)-[1,1?-biphenyl]-3-ol(DDOP-C_(6)H_(5)) and 4-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)-3-hydroxy-benzonitrile(DDOP-CN), have been systematically explored by density functional theory(DFT) and time-dependent density functional theory(TDDFT) methods. Two stable configurations(enol and keto forms) are found in the ground states(S_(0)) for all the compounds while the enol form only exists in the first excited states(S_(1)) for the compound modified with electron donating group(-C_(6)H_(5)). In addition, the calculated absorption and emission spectra of the compounds are in good agreements with the experiments. Infrared vibrational spectra at the hydrogen bond groups demonstrate that the intramolecular hydrogen bond O(1)-H(2)···N(3) in DDOP-C_(6)H_(5) is strengthened in the S_(1) states, while the frontier molecular orbitals further reveal that the ESIPT reactions are more likely to occur in the S_(1) states for all the compounds. Besides, the proton transfer potential energy curves show that the enol forms can barely convert into keto forms in the S_(0) states because of the high energy barriers. Meanwhile, intramolecular proton transfer of all the compounds could occur in S_(1) states. The ESIPT reactions of the ortho-hydroxylated oxazolines are barrierless processes for unsubstituted DDOP and electron withdrawing substituted DDOP-CN, while the electron donating substituted DDOP-C_(6)H_(5) has a small barrier, so the electron donating is unfavorable to the ESIPT reactions of ortho-hydroxylated oxazolines.

Access to multi-functionalized oxazolines via silver-catalyzed heteroannulation of enamides with sulfoxonium ylides

Disclosed herein is an efficient Ag-catalyzed 4+1 heteroannulation reaction of enamides withα-carbonyl sulfoxonium ylides.The diastereoselective transformation provides a practical access to a diverse range of multi-functionalized oxazoline derivatives.The synthetic utility of the resultant tetrasubstituted oxazolines is further demonstrated by a series of useful manipulations into valuable building blocks of pharmaceutical relevance.

Synthesis and characterization of diblock copolymer of butadiene and 2-ethyl-2-oxazoline

By mechanism transformation (anionic cationic) polymerization, diblock copolymer of butadiene and 2 ethyl 2 oxazoline (PBd b PEOx) was synthesized in two steps. The first step is the polymerization of butadiene block capped with ethylene oxide and its tosylation; the second step is the cationic ring opening polymerization of 2 ethyl 2 oxazoline. The products were characterized by various methods, such as IR, 1HNMR, DMA, TEM and SAXS. The results show that the obtained copolymers possess high molecular weight and narrow molecular weight distribution, and that the content of 1,4 structure was controllable.

Modification of diphenylamine-linked bis(oxazoline) ligands: Tuning of electronic effect and rigidity of ligand skeleton

The electronic effect of diphenylamine-linked bis(oxazoline) ligands was tuned through introduction of electron-withdrawing bromo and nitro substituents onto the 4 and 4′ position. The variation of the NH bond acidity was determined by the different chemical shifts of NH. The catalytic activity and enantioselectivity of the modified ligands were tested in the asymmetric Friedel-Crafts alkylation of indole with β-nitrostyrene. The effect of ligand skeleton rigidity was also investigated through the synthesis of iminodibenzyl-linked bis(oxazoline) ligands and evaluation of their catalytic activity in Friedel-Crafts alkylation.

A Convenient Synthesis of 2-Oxazolines and 2-Benoxazoles with PPh3-DDQ as the Dehydrating Reagent

2-Oxazolines and 2-benoxazoles were synthesized in high yields from acylamino alcohols and acylaminophenols, respectively, with triphenylphosphine-2,3-dichloro-5,6-dicyanobenzoquinone （PPh3-DDQ） as the dehydrating and activating reagent. The synthesis was accomplished under neutral conditions.

Synthesis of 2-Oxazolines from Ethyl α-Cyanocinnamate Derivatives with Acetamide and N-Bromosuccinimide

An efficient method for the one-pot synthesis of 2-oxazolines from ethyl a-cyanocinnamate derivatives with acetamide and N-bromosuccinimide（NBS） in the presence of K3PO4 was developed. The reaction was performed smoothly and cleanly to give 2-oxazolines in good to excellent yields（up to 95%） in acetone at room temperature. Thirteen examples were investigated and the results indicated that a large range of a-cyanocinnamate derivatives could be suitable for this method. Based on the outcomes of experiment, a possible consecutive nucleophilic addition- cyclization pathway was proposed.

Asymmetric Diels-Alder Reaction Catalyzed by Novel Chiral Dibenzo[a,c]cycloheptadiene Bis(oxazoline) Metal Complexes

A series of novel chiral C 2 symmetric bis(oxazoline) ligands have been synthesized. The copper and magnesium complexes, prepared in situ from copper(II) triflate or magnesium triflate with the new enantiopure oxazoline ligands, were evaluated as chiral catalysts in the enantioselective Diels Alder reaction of cyclopentadiene with N crotenoyl oxazolidin 2 one. Primary results showed that diastereoselectivity up to 94% and enantioselectivity up to 68% ee for endo products were observed respectively with these ligands.

Visible-light-promoted radical alkylation/cyclization of allylic amide with N-hydroxyphthalimide ester: Synthesis of oxazolines

An efficient photocatalytic alkylation/cyclization of allylic amide with N-hydroxyphthalimide ester has been developed. The transformation is taken advantage of alkyl radicals to attack allylic amide with the assist of inexpensive rose bengal as photocatalyst to prepare a series of alkyl substituted oxazolines in moderate to excellent yields. High regioselectivity, operational safety, mild conditions and excellent substrate generality give this protocol broad application prospects.

New Chiral Substituted 8-Quinolinyl-oxazolines as Ligands for Copper(I)-catalyzed Asymmetric Cyclopropanation

New chiral substituted 8-quinolinyl-oxazoline ligands have been synthesized and applied in the copper(I)-catalyzed asymmetric cyclopropanation of styrene with alkyl diazoacetates. The steric effect in the ligands plays a significant role in the enantiocontrol in asymmetric cyclopropanation, while the electronic effect is less important.

Synthesis and structure of the first propeller-shaped helical coordination polymer { [ Ag( S , S) -bis( oxazoline) ] (OTf)}_∞

A mixture of (S, S)-bis(oxazoline) ligand (1) with silver trifluoromethane sulfonate afforded a helical coordination polymer (2). Its structure was determined by X-ray angle-crystal diffraction.

Synthesis of (+) or (-)-2-(8′-Diphenylphosphino-1′-naphthyl)oxazoline Ligands and Their Application in Pd-Catalyzed Allylic Alkylation Reaction

We synthesized optically active 2-(8′-diphenylphosphino-1′-naphthyl)oxazoline ligands by palladium-catalyzed coupling reactions of (trimethylsilyl)diphenylphosphine with 2-(8′-bromo-1′-naphthyl)oxazolines, which, in turn, were prepared from 8-bromo-1-naphthoyl chloride by the reaction with natural optical active amino alcohols. Pd-Catalyzed allylic alkylation reaction induced by these chiral ligands gave the allylic substituted products in high yields and moderate ee values.

2-氨基-2-脱氧糖糖苷合成概述

综述了 2 -氨基 - 2 -脱氧糖糖苷的合成 ,简述了其反应机理、条件及区域选择性和立体选择性 ,以及近年来的研究进展。