An Efficient and Practical Procedure for Synthesis of Diacetals

Pentaerythritol diacetals are useful in many fields. They can be applied as plasticizers and vulcanizers of various polymeric materials, as raw materials for production of valuable resins and lacquers, as physiologically active substances and as defoamers for washing solution containing anionic surfactants. [ 1 ～ 4] Synthsis of diacetals from 2,2bis(hydroxymethyl)-1, 3-propanediol with aldehydes and ketones in refluxing toluene using ZrO2/S2O2- 8 solid superacid as catalyst in 85% ～ 99% yields has been described. The catalysts are easily regenerated by washing with ethanol followed by drying at 120 ℃ for 4 h and could be reused 5 times for the synthesis pentaerythritol diacetal 3e without significant loss of activity. This method possesses the advantages of the operational simplicity, short reaction time, use of inexpensive materials, non-corrosion, non-polluting, high yields and reusable catalysts.     

An Efficient Procedure for the Preparation of 1-Nitroanthraquinone

A novel and efficient method is developed for the selective mono nitration of anthraquinone (1). A mixture of fuming nitric acid, sulfuric acid and phosphoric acid in carbon tetrachloride is introduced as a new nitrating system for the high yield preparation of 1-nitroanthraquinone.     

Synthesis of (−)-α-CIS-Bergamotene. An Efficient Prenylation Procedure

The introduction of the “isoprene unit” is an important key step in terpene synthesis and to this end, several basic routes employing organometallics have been utilised.     

An Efficient Procedure for Cleavage of T-Butyl Protected Cysteine in Solid Phase Peptide Synthesis

In the Fmoc-strategy of solid phase peptide synthesis, 1M trimethylsilyl bromide-thioanisole/trifluoroacetic acid in the presence of 1,2-ethanedithiol as scavenger was found to be an efficient deprotecting procedure for a full cleavage and side chains deprotection of the peptide resin involving t-butyl protected cysteine. In addition, selective deprotection of the peptide resin containing protected cysteine was also described based on this method.     

一种高效简易的聚(4-乙烯基三溴化吡啶)催化乙醇合成乙酸盐的方法(英文)

Poly(4-vinylpyridinium tribromide) is an efficient catalyst for the conversion of various alcohols to their corresponding acetate derivatives with acetic anhydride.This method has some advantages such as mild reaction conditions,good to excellent yields,and ease of work-up.     

Microwave-Promoted Facile and Rapid Synthesis Procedure for the Efficient Synthesis of 5,5-Disubstituted Hydantoins

A fast, general, environmentally friendly, and facile method for preparation of 5, 5-disubstituted hydantoins from the reaction between ketone (or aldehyde) derivatives with KCN and ammonium carbonate under microwave irradiation is presented. The microwaves remarkably accelerated this reaction, the reaction times decreased dramatically, the reaction conditions were milder, and the yields were also greater. Also a comparative study of microwave versus classical conditions has been done. All the products were characterized by infrared, NMR, and CHN analysis, and their melting points are identical to those of the known compounds reported in the literature. This method might be useful in the future for the preparation of similar derivatives.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resources: Full experimental and spectral details.]     

A General Procedure for the Efficient Synthesis of (Alkylamino)naphthoquinones

Alkylamino derivatives of naphthazarine, juglone, and naphthoquinone have been synthesized via their corresponding bromo-analogues, in high yields, especially in the case of naphthazarins.     

An Improved Procedure for the Synthesis of Prostaglandin Analogues

Hydrozirconation-iodination of a terminal acetylene followed by lithium-iodide exchange and finally dilithio cyanocuprate mediated conjugate addition to an appropriate cyclopentenone is reported as an efficient method for the synthesis of prostaglandin analogues.     

An Improved Procedure for the Synthesis of Ethyl Glycidate

Ethylglycidate (1), is a useful intermediate which can be used in several reactions involving epoxide ring opening with the introduction of an ester function and in co-polymer chemistry (1,2). Emmons and Pagano (3) described the preparation of I by epoxidation of ethyl acrylate with peroxytrifluoroacetic acid in 54% yield.     

Synthesis of Acetophenone Azine

Conditions for preparing acetophenone azine via the oxidative dimerization of acetophenone imine anion are investigated.     

An Efficient Method for the Synthesis of Laquinimod

Laquinimod, 5‐chloro‐1,2‐dihydro‐N‐ethyl‐4‐hydroxy‐1‐methyl‐2‐oxo‐N‐ phenyl‐3‐quinoline carboxamide, is an oral drug in clinical trials for the treatment of multiple sclerosis. An efficient synthetic method for laquinimod from 2‐amino‐6‐chlorobenzoic acid via four steps was established. The overall yield of laquinimod is up to 82% as compared with 70% reported in literature. It has also been demonstrated that green reagent dimethyl carbonate is not suitable for the N‐methylation of 5‐chloroisatoic anhydride owing to the ring‐cleavage reaction induced by the generated methanol. The ring‐cleavage by‐products were isolated and characterized by ¹H‐NMR and ¹³C‐NMR. In addition, in the study of laquinimod derivatives, we found that 5‐chloro‐1,2‐dihydro‐N‐ethyl‐4‐hydroxy‐1‐methyl‐2‐oxo‐N‐phenyl‐3‐quinoline carboxamide (laquinimod) was obtained in much higher yield than 7‐chloro‐1,2‐dihydro‐N‐ethyl‐4‐hydroxy‐1‐methyl‐2‐oxo‐N‐phenyl‐3‐quinoline carboxamide under the same reaction conditions, and it is possibly attributed to a neighboring group effect.     

An Efficient and Practical Procedure for Synthesis of 1,1‐Diacetates from Aldehydes Catalyzed by Zirconium Sulfate Tetrahydrate–Silica Gel

Abstract

A facile and efficient procedure for synthesis of 1,1‐diacetates from aldehydes with acetic anhydride was described using zirconium sulfate tetrahydrate–silica gel as catalyst in excellent yields under mild reaction conditions.     

超声波作用下溴仿与镁的反应--产生二溴卡宾的新方法

超声波辐射可有效地促进溴仿和镁产生二溴卡宾的反应.当n(溴仿)/n(镁)/n(烯烃)=2/1/1时,以无水乙醚反应可在15～25min内以较高的产率反应生成偕二溴环丙烷衍生物.该方法具有反应速度快、产率高等优点,是一种产生二溴卡宾的新的实用方法.探讨了溴仿与镁的单电子转移(SET)和自由基链循环的反应机理.     

One-pot Three-component Condensation Reactions in Water. An Efficient and Improved Procedure for the Synthesis of Furan Annulated Heterocycles

Summary. The environment-friendly one-pot three-component condensation reactions of 4-hydroxycoumarin or 4-hydroxy-6-methylpyrone, p-substituted benzaldehyde, and alkyl or aryl isocyanides to afford furocoumarines or furopyranones in water in good yields after about one hour at 75°C are reported.     

One-pot Three-component Condensation Reactions in Water. An Efficient and Improved Procedure for the Synthesis of Furan Annulated Heterocycles

The environment-friendly one-pot three-component condensation reactions of 4-hydroxycoumarin or 4-hydroxy-6-methylpyrone, p-substituted benzaldehyde, and alkyl or aryl isocyanides to afford furocoumarines or furopyranones in water in good yields after about one hour at 75°C are reported.     

An Improved General Procedure for the Synthesis of Aryloxysulfonyl Azides

In 1975, we have described the first synthesis of the aryloxysulfonyl azides (aryl azidosulfates),¹ the interest of which is confirmed to be varied, especially about the elaboration of molecules such that sulfamates² (Ar-O-SO₂-NH₂), not easily accessible by other methods and endowed with very important biological properties.^3–5 Their cycloaddition on bicyclic olefinic systems gives a new family of N-substituted aziridines, the N-aryloxy-3-aza-tricyclo[3,2,1,0^{2,4 exo}]octanes.⁶ They react with trivalent phosphorus compounds to afford some very interesting phosphine-imides.⁷     

An Improved and Convenient Procedure for the Synthesis of Ozagrel

Ozagrel 1 is a 1-alkylimidazole derivative that acts as a selective inhibitor ofthromboxane A2 (TXA2) with an IC50 of 11mol/L. The beneficial effects of TXA2inhibition by ozagrel include improved motor coordination after experimental stroke, andantihypert…     

尿素催化的高效绿色Knoevenagel缩合反应

An efficient and green procedure for the urea catalyzed Knoevenagel condensation was developed. In the presence of a catalytic ammount of urea, stoichiometric aldehyde and active methylene compound reacted under sol-vent-free conditions at 100℃ for 5-60 min to give nearly quantitative yield of product.     

An Efficient Catalyst for the Direct Synthesis of N-Phenylpyrrolidine

N-Phenylpyrrolidine is an important N-heterocycle compound used in the fields of medicine, the material chemistry and the synthesis of fine chemicals1-3. There are a lot of methods to produce N-phenylpyrrolidine4-6. However, One of the most promising rout…     

An Efficient Method for the Synthesis of 1-Arylalkynes

1-Arylalkynes are prepared from propiophenones in good yield via the sequence a) 2 equiv PCl₅/Δ b) DBN or Δ and c) Mg metal.