Mechanism of cyclic acetal formation

The mechanism of formation of 1,3-dioxolanes is considered in the light of Baldwin's rule for ring-closure.     

Fluorination of hydroxyesters with N,N-diethyl-1,1,2,3,3,3-hexafluoro propylamine

The reaction of 1,1,2,3,3,3-hexafluoropropyldiethylamine (PPDA) with hydroxy esters having PhC(H)(OH)-groups gave their corresponding secondary fluorides. Fluorination of (R)-(-)-mandelic acid ethylester ([α]²⁹_D −106.46) gave ethyl (S)-(+)-2-fluoro-2-phenyl acetate ([α]²⁹_D +6.57). The value of the enantiomeric excess (% ee) was 74.1. The reaction mechanism of the fluorination by PPDA is suggested to be the S_N2 type.     

Selective monofluorination of diols using DFMBA

Selective monofluorination of 1,2- and 1,3-diols was achieved by reaction with DFMBA. The method is applicable for the synthesis of optically-active fluorohydrin derivatives.     

Selective cyclodehydration of diols on zeolites

1,4-Butanediol, 2,5-hexanediol and 1,5-pentanediol were selectively converted to tetrahydrofuran and tetrahydropyran in the presence of LaHY, CaHY and H-ZSM-6 zeolites. The advantage of these zeolites is in their high stability and faster regeneration.     

Reactions of monoesters of ethylene glycol with N,N-diethyl-1,1,2,3,3,3-hexafluoropropylamine

By reaction with 1,1,2,3,3,3-hexafluoropropyldiethylamine (PPDA), various monoesters of ethylene glycol gave a mixture of corresponding monofluorides and 2,3,3,3-tetrafluoropropionate esters. The antimicrobial properties of these fluorine compounds for a spent coolant were examined.     

Selective synthesis of 4-alkylidene-beta-lactams and N,N'-diarylamidines from azides and aryloxyacetyl chlorides via a ketenimine-participating one-pot cascade process

A one-pot cascade approach to 4-alkylidene-beta-lactams and N, N'-diarylamidines from aryl azides and aryloxyacetyl chlorides has been developed. The chemical outcome of the reaction can be controlled selectively by an appropriate choice of the stoichiometric ratio of different substrates and reagents. The products should find use in pharmaceutical discovery, especially in the development of new antimicrobial agents against multidrug-resistant pathogens.     

Cu(II) complexes of N,N-diethyl-2-picolinamine N-oxide

Cu(II) complexes have been prepared with N,N-diethyl-2-picolinamine N-oxide (DEA) employing the perchlorate, tetrafluoroborate, nitrate, chloride and bromide salts. A single unique solid was isolated for each Cu(II) salt with the following stoichiometries: Cu(DEA)₂X₂(XClO₄ and BF₄) and Cu(DEA)X₂(XNO₃, Cl and Br). Characterization has been accomplished primarily by IR, electronic and ESR spectral measurements of the solid state complexes. Significant, though not as great as with lighter ligands of the same series, changes occurred when spectral measurements of acetonitrile or nitromethane solutions were attempted. DEA was found to bind to Cu(II) exclusively as a bidentate ligand via the N-oxide oxygen and the amine nitrogen.     

Living cationic polymerization of vinyl ether with a cyclic acetal group

The living cationic polymerization of 5‐ethyl‐2‐methyl‐5‐(vinyloxymethyl)‐1,3‐dioxane ( 1 ), a vinyl ether with a cyclic acetal unit, was investigated with various initiating systems in toluene or methylene chloride at 0 to ?30 °C. With initiating systems such as hydrogen chloride (HCl)/zinc chloride (ZnCl₂), isobutyl vinyl ether–acetic acid adduct [CH₃CH(OiBu)OCOCH₃]/tin tetrabromide (SnBr₄)/di‐tert‐butylpyridine (DTBP), and CH₃CH(OiBu)OCOCH₃/ethylaluminum sesquichloride (Et_1.5AlCl_1.5)/ethyl acetate (CH₃COOEt), the number‐average molecular weights (M_n's) of the obtained poly( 1 )s increased in direct proportion to the monomer conversion and produced polymers with relatively narrow molecular weight distributions [MWDs; weight‐average molecular weight/number‐average molecular weight (M_w/M_n) = 1.2–1.3]. To investigate the living nature of the polymerization with CH₃CH(OiBu)OCOCH₃/SnBr₄/DTBP, a second monomer feed was added to the almost polymerized reaction mixture. The added monomer was completely consumed, and the M_n values of the polymers showed a direct increase against the conversion of the added monomer, indicating the formation of a long‐lived propagating species. The glass transition temperature and thermal decomposition temperature of poly( 1 ) (e.g., M_n = 13,600, M_w/M_n = 1.30) were 29 and 308 °C, respectively. The cyclic acetal group in the pendants of the polymer of 1 could be converted to the corresponding two hydroxy groups in a 65% yield by an acid‐catalyzed hydrolysis reaction. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4855–4866, 2007     

Convenient preparation of cyclic acetals,using diols,TMS-source,and a catalytic amount of TMSOTf

With use of diol, alkoxysilane, and a catalytic amount of trimethylsilyl trifluoromethanesulfonate (TMSOTf), carbonyl compounds are converted to acetals in good yields under mild conditions. This procedure, which was carried out without synthesizing the silylated diols, is a more convenient adaptation of Noyori's method. This acetalization applies to not only simple but also conjugated carbonyl compounds. Moreover, various TMS compounds, including solid supported compounds, are effective for this method instead of alkoxylsilane.     

Copolymerization of cyclic ketene N,O-acetals with phenylisothiocyanate via zwitterionic intermediates

The reaction of 3-methyl-2-methylene-1,3-oxazolidine ( 1a ) and phenylisothiocyanate (PhNCS) gives 3-methyl-2-(phenylthiocarbamoyl)methylene-1,3-oxazolidine ( 3 ) whereas that of 2-isopropylidene-3-methyl-1,3-oxazolidine ( 1b ) and PhNCS gives 1:1 alternating copolymers. It is assumed that the reaction of 1b and PhNCS forms a zwitterionic intermediate ( 2b ), followed by the successive combination of 2b to give 1:1 alternating copolymers 4 and/or 5 . Consequently, it was demonstrated that the copolymerization of 1b and PhNCS proceeds via a zwitterionic mechanism with complete ring-opening to afford the 1:1 alternating copolymer 5 .     

Dimerization of the cyclic ethylene acetal of crotonaldehyde

Summary Dimerization of the cyclic acetal of crotonaldehyde takes place in accordance with the scheme studied previously, leading to the formation of a 1,4-dioxepan ring.     

Photoaddition reactions of fluoroolefins with diols and cyclic ethers

Fluoroalkylation of aliphatic diols, tetrahydrofuran and 1,3-dioxolanes with perfluoroolefins under photochemical initiation was studied. The aim of the study was the preparation of fluoroalkylated diols as intermediates for special fluorinated monomers. Fluoroalkylation was only partly successful in the case of 1,4-butanediol and quite successful with tetrahydrofuran and 2,2-dimethyl-1,3-dioxolane. The fluoroalkyl diols obtained were converted to monomethacrylates that are amphiphilic monomers.     

N,N′-亚乙基二(2-羟基-4-甲氧基二苯酮缩亚胺)Schiff碱的合成及抑菌活性

本文将 2 羟基 4 甲氧基二苯酮与乙二胺缩合成Ｓｃｈｉｆｆ碱 ,发现该Ｓｃｈｉｆｆ碱对紫外光的ＵＶ -Ａ、ＵＶ-Ｂ区都有较强吸收 ,对多种细菌有抑制作用。1　实验部分1 1　合成称取 2 羟基 4 甲氧基二苯酮 6 848ｇ( 30ｍｍｏｌ)于圆底烧瓶内 ,加 30ｍｌ 95 %乙醇 ,水浴加热至 5 0℃ ,磁力搅拌溶解 ,滴加 0 90 0ｇ( 1 5ｍｍｏｌ)乙二胺溶液 ,磁力搅拌 ,5 0～ 60℃回流反应 4ｈ ,析出黄色固体 ,冷却 ,过滤 ,用热的 95 %乙醇 ( 30～40℃ )溶液洗三次 ,再用乙醚洗一次 ,抽干。 40℃真空干燥 5ｈ ,得黄色粉末 ,产率 94%。1 2　表征Ｓｃｈｉ…     

Selective mono protection of diols, diamines, and amino alcohols using cesium bases

Efficient synthetic methods were developed for the synthesis of mono xanthates, as well as mono dithiocarbamates of diamines and amino alcohols. This protocol utilizes the three component coupling of diols, diamines, and amino alcohols using alkyl bromides and carbon disulfide in the presence of a cesium base and tetrabutylammonium iodide (TBAI).     

Selective five- and six-membered cyclic amine syntheses via capture of episulfonium ions

Amide nitrogens open episulfonium ions to form pyrrolidines or piperidines selectively, depending on the nitrogen substituent, in either reversible or irreversible reactions.