Synthesis of β-Lactams from Acids and Imines Using Thiocarbonyldiimidazole

Thiocarbonyldiimidazole has been found to be an efficient acid activator for the synthesis of β-lactams by ketene-imine cycloaddition at room temperature. The experimental procedure is simple and results in excellent yields of the products. All products were characterized by spectral data and elemental analyses.     

A New and Efficient Synthesis of Wedelolactone Derivatives

A new and facile method based on an intermolecular cycloaddition was described for the synthesis of wedelolactone derivatives.     

Synthesis of New Thiazine and Thiosemicarbazone Derivatives from D-Xylose

Thioureas have strong antifungal activities1 and their antimicrobial and insecticidal properties have been documented for more than fifty years2. Recently thiourea derivatives have been reported to possess antitubercular, antithyroid and anticancer3 prope…     

Synthesis of 1,1‐Dimethyl‐4‐indanol Derivatives

The synthesis of 1,1‐dimethyl‐4‐indanols (3a,b) has been achieved by intramolecular Friedel–Crafts cyclization of 2‐(3‐methyl‐2‐butenyl)phenols (5a,b) or 1‐methoxy‐2‐(3‐methyl‐2‐butenyl)benzenes (6a,b) followed by demethylation, respectively.It was found that the solvent was critical for the formation of different products in the intramolecular Friedel–Crafts reactions of 6. The unexpected product 4‐methoxy‐1,1,6,6‐tetramethyl‐as‐hydrindacene (11) was obtained from the Friedel–Crafts reactions of 6a, and its structure was confirmed by X‐ray diffraction analysis. The key intermediates 5a,b were prepared by ortho‐alkenylation of phenols with 1‐bromo‐3‐methyl‐2‐butene, and the reaction temperature exerted an obvious impact on the yield of 2‐(3‐methyl‐2‐butenyl)phenol (5a).     

A Practical Synthesis of ω-Aminoalkanoic Acid Derivatives from Cycloalkanones

A practical synthetic route to N-Boc protected or Boc-amino acid coupled ω-aminoalkanoic acids is reported and exemplified by the preparation of 8-(t-butoxycarbonylamino)caprylic acid 2 and (N-t-butoxycarbonylphenylalanyl)-8-aminocaprylic acid 3. The sequence does not involve column chromatography, hydrogenation, azide or bromine related rearrangements, and therefore is amenable to scale-up. Homologues of the ω-aminoalkanoic acid derivatives may also be prepared by using different cycloalkanones.     

Intrinsic Kinetics of Dimethyl Ether Synthesis from Syngas

The intrinsic kinetics of dimethyl ether (DME) synthesis from syngas over a methanol synthesis catalyst mixed with methanol dehydration catalyst has been investigated in a tubular integral reactor at 3-7MPa and 220-260℃. The three reactions including methanol synthesis from CO and H2, CO2 and H2, and methanol dehydration were chosen as the independent reactions. The L-H kinetic model was presented for dimethyl ether synthesis and the parameters of the model were obtained by using simplex method combined with genetic algorithm. The model is reliable according to statistical analysis and residual error analysis. The synergy effect of the reactions over the bifunctional catalyst was compared with the effect for methanol synthesis catalyst under the same conditions based on the model. The effects of syngas containing N2 on the reactions were also simulated.     

A Simple Synthesis of γ-Cyclohomocitral

A simple and efficient synthesis for γ-cyclohomocitral (10), a key and versatile intermediate for the synthesis of some furanosesquiterpenes, is described. The formal total synthesis of (±) Pallenscensone (2) was accomplished.     

Synthesis of Isoquinoline Derivatives from β-Hydroxyarylethanamides

A simple and efficient protocol for the construction of medicinally important substituted isoquinolines through intramolecular cyclization of β-hydroxyarylethanamides using acetic anhydride and phosphorous pentoxide in dioxane has been described. The chemo- and regioselectivities due to the influence of different catalysts were investigated and optimized for good to excellent yields. All the synthesized compounds have been characterized by NMR and mass spectral analyses.     

A Novel Synthesis of Isoxazole Derivatives

Thenitronesareveryimportantinorganicsynthesis.TheyhavebeenwidelyutilizedasintermediatesfromwhichcomPlexheterocyclicornaturalcompoundsanddrugs"'weresynthesisedsuchasisoxazoline3andoxazine4.However,theconversionofnitronetoisoxazolebythermaldecompositionhasnotbeenreported.Inthispaper,wedevelopanewsyntheticmethodofisoxazolesfromheterocyclicnitronesasfollows:wi.-"'rtXfa.H;b.3,4-O-CH2-o-;c.4-CH3O,d.4-Cl;e.2-Brf.2-Cl,g.3,4-coCH3;h.3-ro2;i.4-so2;j.4-CH3Experiment8lAdriedroundbottomflaskundernit…     

Synthesis of Antipyrine Derivatives Derived from Dimedone

Coupling of dimedone with the diazonium salt of 4-aminoantipyrine afforded 2,3-dimethyl-4-[2-（5,5-dimethyl- 2,6-dioxocyclohex-2-ylidend）-hydrazino]-5-oxo-1-phenylpyrazoline （3）. Reaction of 3 with excess phenylhydrazine gave the mixed trishydrazone derivative 4. Treatment of 3 with hydroxylamine produced the bisoxime 5 which upon dehydrative cyclization with acetic anhydride gave the corrsponding tetrahydrobenzo[d][1,2,3]triazole derivative 7. A one-pot synthesis of 7 was done by reacting 3 with hydroxylamine hydrochloride in pyridine, followed by heatment with acetic anhydride.     

Simple and Convenient Synthesis of 21‐Thioalkylether Derivatives of Methyl 16‐Prednisolone Carboxylates

The antedrug approach for corticosteroids has been described as a fundamentally sound approach for the development of safer anti‐inflammatory and anti‐asthmatic therapy. However, the derivatization of prednisolone and its congeners have been considered to be major pitfalls, because their syntheses are complicated by the presence of numerous carboxylate esters and hydroxyl functions in the steroid nucleus. A simple and direct synthesis of 21‐thioalkylether derivatives of methyl 16‐prednisolonecarboxylates is described. The 21‐mesylate of the methyl 16‐prednisolonecarboxylate and 9‐fluoro‐17‐dehydro methyl 16‐prednisolonecarboxylate were reacted with Na‐thioalkoxides to furnish the desired thioethers in good yields. A previously published method for the methanolysis of 16‐cyanoprednisolone to methylcarboxylate has been reexamined, and the conditions are explained clearly. The reaction conditions for all these reactions were critical.     

Catalytic Asymmetric γ-Lactam Synthesis from Enolisable Anhydrides and Imines

An anion-binding approach to the problem of preparing enantioenriched γ-lactams from enolisable anhydrides and imines is reported. A simple bisurea catalyst promotes the cycloaddition between α-aryl succinic anhydrides and either PMP- or benzhydryl-protected aldimines to provide γ-lactams with two contiguous stereocentres (one quaternary) with complete diastereocontrol and high to excellent enantioselectivity for the first time. A DFT study has provided insight into the catalyst mode of action and the origins of the observed stereocontrol.     

Alkali Metal–Promoted Facile Synthesis of Secondary Amines from Imines and Carbodiimides

We present here an efficient method for the hydroboration of aldimines (-C=N-) with pinacolborane (HBpin) using an alkali metal catalyst, potassium benzyl. The reaction was accomplished with unprecedented catalytic efficiency under mild and solvent-free conditions to afford the high yield of the corresponding N-boryl amines up to 97%. Various functionalities on aldimines were incorporated for hydroboration. The corresponding boryl amines were subjected to further hydrolysis to yield the corresponding secondary amines with good yields up to 89%. This protocol for the reaction demonstrates an atom-economic and green method with diverse imines that bears excellent functional group tolerance. Chemoselective reduction of imines was also attained, with good yields of 74–89%. We also propose the most plausible mechanism involving the formation of metal hydride as the active pre-catalyst.     

Synthesis of 1,3-Dioxolane Derivatives from β-Chlorolactic Acid and Ketones

2-Ethyl-2-methyl-5-methylene-1,3-dioxolan-4-one and 5-methylene-2,2-pentamethylene-1,3-dioxolan-4-one were synthesized by reaction of -chlorolactic acid with methyl ethyl ketone and cyclohexanone, respectively, followed by dehydrochlorination of intermediate 5-chloromethyl derivatives.     

A New and Efficient Synthesis of 2H-3, 1-Benzoxazine Compounds

2H-3, 1-Benzoxazine heterocyclic compounds are a series of potent nonsteroidal pro- gesterone receptor agonists1-3 and have many other applications such as carbonaceous electrode, plant growth regulating and anti-stress activities4-6, etc.. Comparing to other benzoxazine series, such as 1, 4-benzoxazine, 2H-1, 3-benzoxazine, etc., little attentions have been paid for this series of compounds. There is only one method for the preparation of 2H-3, 1-benzoxazine, e.g. cyclocondensation of o-amin…     

A Simple Synthesis of dl—Shikonin

A new facile route for the synthesis of dl-shikomin is presented.Reformatsky reaction assisted cross-coupling of 1,4,5,8-tertramethoxynaphthalene-2-carbaldehyde and ethyl-bromoacetate was empolyed for introduction of the side chain of dl-shikonin.     

Synthesis and Characterization of Novel 4-Methyl-3-isoxazolidinone Derivatives

IntroductionSulfonylureas, as inhibitors of acetohydroxyacidsynthase(AHAS), are a class of herbicides that areused for crop protection. They are used for lowconcen-tration ranges(10—100 g of active ingredient/ha) andare advanced herbicides used in agricu…