Protected ester,nitrile, carbinol and carbinyl amine cyclopropanone hydrates

Methyl diazoacetate reacted with the ketene acetal I in the presence of dirhodium tetraacetate yielding the metastable cyclopropanone ketal ester II, which was converted to the primary and tertiary cyclopropyl carbinols III and IV by treatment with lithium aluminum hydride and methyl lithium, respectively. Diazoacetonitrile yielded a stable crystalline cyclopropanone ketal nitrile X following reaction with the ketene acetal I.     

Self-assembly of an unpolar enantiomerically pure helicate-type metalla-cryptand

Chiral tetraketone ligands are obtained by Claisen-type condensation of 4-bromoacetophenone with the acetone ketal of L-tartraic acid diethylester and lead with gallium(III) or iron(III) ions in self-assembly processes to dinuclear helicate-type cryptands which are able to bind lithium cations.     

Allylsilane and diallylsilane reactions with functionalized ethylene ketals or benzodioxoles

The bis-allylation of ethylene ketal and catechol ketal derivatives of 2,5-hexanedione occurred with a great stereoselectivity. The tetraallylation of bis-catechol ketal derivatives of 2,5-hexanedione and 2-methyl-1,3-cyclohexanedione or the diallylation of 4-phenylbutan-2-one derivatives arise in good yields and these compounds were suitable substrates for ring-closing metathesis leading to 4,4-dialkylcyclopentenes. Condensation of 1,8-bistrimethylsilyl-2,6-octadiene (Bistro) with 4-phenylbutan-2-one catechol ketal derivatives or 2-methylcyclohexan-1,3-dione mono catechol ketal afforded in good yields cyclic and tricyclic products 12 or 23, respectively.     

Acetalation and Ketalation Catalyzed by SO42-/TiO2-MoO3

The catalytic activities of SO42-/TiO2-MoO3 in synthesizing cyclohexanone ethylene ketal,cyclohexanone 1,2-propanediol ketal, 2-propyl-1,3-dioxolane, 4-methyl-2-isopropyl-1,3-dioxolane,2-isopropyl-1,3-dioxolane, 4-methyl-2-isopropyl-1,3-dioxolane, butanone ethy-lene ketal and butanone 1,2-propanediol ketal were reported. It has been demonstrated that SO42-/TiO2-MoO3 is an excellent catalyst. Various factors concerned in this reaction have been investigated. The optimum conditions have been found, that is, the molar ratio of aldehyde/ketone to alcohol was 1:1.5 or 1:1.3,the mass ratio of the catalyst used to the reactants was 0.25～1.5%, and the reaction time was 45～60 min. Under this conditions, the yield of cyclohexanone ethylene ketal is 82.7%, cyclohexanone 1,2-propanediol ketal is 83.4%, the yield of 2-propyl-1,3-dioxolane is 68.1%,4-methyl-2-isopropyl-1,3-dioxolane is 87.5%, the yield of 2-isopropyl-1,3-dioxolane is 70.7%,4-methyl-2-isopropyl-1,3-dioxolane is 82.5%, the yield of butanone ethylene ketal is 74.1%, and butanone 1,2-propanediol ketal is 94.9%.Some equation and experiment results concerned of the synthetic acetals or ketals were listed as follows.     

Opening of a 1,3-dioxolane by nucleophilic attack at a ketal methylene

A novel type of opening of an ethylene ketal has been observed in the reaction of 1 with alane RA1Me₂. The reaction is explained in terms of a nucleophilic attack on the ketal methylene synchronous with participation by one of the ketal oxygens in the opening of the epoxide function located across the 7-membered ring of 1.     

Isolation,tentative identification,and synthesis studies of the volatile components of the hairpencil secretion of the monarch butterfly

The major volatile components of the hairpencil secretion of the male monarch butterfly have been identified as benzyl caproate and either 1, 5, 5, 9-tetramethyl-10-oxabicyclo[4.4.0]-3- decen-2-one(1), or 2, 2, 6, 8-tetramethyl-7-oxabicyclo[4.4.0]-4-decen-3-one(2). One sequence designed to synthesize 1 yielded two isomeric products of structure 1 whose spectra are very similar to each other but distinctly different from those of the natural product; this sequence also yielded a tricyclic ketal (9). A second sequence gave two epimeric spiro compounds (12) and a third sequence gave a [4.3.0] ring system (14).     

Practical synthesis of functionalized terminal alkynes, 3,3,3-triethoxypropyne and ketal protected prop-2-ynones

Practical and economical synthesis of synthetically valuable 3,3,3-triethoxypropyne, ketal protected phenyl and methyl substituents prop-2-ynones is described. Bromination and subsequent 18-crown-6 catalyzed elimination of triethylorthoacrylate and ketal protected terminal alkenes with methyl and phenyl substituent which are inturn readily available from triethylorthopropionate, 3-chlorobutan-2-one and propiophenone afforded multigram quantities (>10?g) of corresponding functionalized terminal alkynes. Exploration of the synthetic utility of these alkynes is also demonstrated by the acetylenic substitution of the phenylalaninol derived 1,2-cyclic sulfamidate to deliver chiral alkynylated amines.     

Branched Multifunctional Polyether Polyketals: Variation of Ketal Group Structure Enables Unprecedented Control over Polymer Degradation in Solution and within Cells

Multifunctional biocompatible and biodegradable nanomaterials incorporating specific degradable linkages that respond to various stimuli and with defined degradation profiles are critical to the advancement of targeted nanomedicine. Herein we report, for the first time, a new class of multifunctional dendritic polyether polyketals containing different ketal linkages in their backbone that exhibit unprecedented control over degradation in solution and within the cells. High-molecular-weight and highly compact poly(ketal hydroxyethers) (PKHEs) were synthesized from newly designed α-epoxy-ω-hydroxyl-functionalized AB(2)-type ketal monomers carrying structurally different ketal groups (both cyclic and acyclic) with good control over polymer properties by anionic ring-opening multibranching polymerization. Polymer functionalization with multiple azide and amine groups was achieved without degradation of the ketal group. The polymer degradation was controlled primarily by the differences in the structure and torsional strain of the substituted ketal groups in the main chain, while for polymers with linear (acyclic) ketal groups, the hydrophobicity of the polymer may play an additional role. This was supported by the log?P values of the monomers and the hydrophobicity of the polymers determined by fluorescence spectroscopy using pyrene as the probe. A range of hydrolysis half-lives of the polymers at mild acidic pH values was achieved, from a few minutes to a few hundred days, directly correlating with the differences in ketal group structures. Confocal microscopy analyses demonstrated similar degradation profiles for PKHEs within live cells, as seen in solution and the delivery of fluorescent marker to the cytosol. The cell viability measured by MTS assay and blood compatibility determined by complement activation, platelet activation, and coagulation assays demonstrate that PKHEs and their degradation products are highly biocompatible. Taken together, these data demonstrate the utility this new class of biodegradable polymer as a highly promising candidate in the development of multifunctional nanomedicine.     

Eine stereospezifische Synthese von syn-Bishomochinon über p-Benzochinon-bis(äthylen)ketal

The bis(ethylene)ketal of p-benzoquinone ( 6 ) has been prepared from the bis(ethylene)ketal of cyclohexane-1,4-dione ( 3 ) by bromination with bromine in ether followed by dehydrobromination with potassium t-butoxide. Two intermediate dibromides ( 4 and 5 ) were isolated and their constitutions as well as their configurations determined from spectroscopic properties. Partial hydrolysis of 6 furnished the mono(ethylene)ketal of p-benzoquinone ( 9 ), which was converted stereospecifically to syn-bishomoquinone ( 2 ) by the double addition of sodium dimethylsulfoxonium-methylide. The intermediate mono(ethylene)ketals of syn-bishomoquinone ( 11 ) as well as of the mono(methylene) addition product ( 10 ) were also isolated.     

Biomimetic total syntheses of (-)-TAN1251A, (+)-TAN1251B, (+)-TAN1251C, and (+)-TAN1251D

[reaction: see text] The muscarinic antagonists (-)-TAN1251A (1), (+)-TAN1251B (2), (+)-TAN1251C (3), and (+)-TAN1251D (4) have been synthesized biomimetically by enamine formation from an amino aldehyde to give TAN1251C ketal 18. Oxidation and reduction lead to TAN1251A (1), which has been hydroxylated to give TAN1251B (2). Stereospecific reduction of TAN1251C ketal 18 leads to TAN1251D (4).     

Use of the ketel claisen rearrangement for the synthesis of cyclic sesquiterpenes containing quaternary centers. A formal synthesis of cuparene

We have shown that the ketal based Claisen rearrangement can be useful for generating vicinal quaternary and tertiary-quaternary centers by suitable substitution on the reacting 2-cyclohexenols and cycloalkanone ketal. A rapid and efficient method for preparing hindered cycloalkanone ketals in very pure form is presented, as well as a useful modification for synthesizing the required 2-cyclohexenols from alkyl anisoles with a minimum number of undesired side products.     

17α-羟基-16β-甲基-5,9(11)-孕甾二烯-3,20-二缩酮的D环高碳化

报导了17α-羟基-16β-甲基-4,9(11)孕甾二烯-3,20-二缩酮(1)用70%醋酸进行的水解反应. 结果得相应的3,20-二酮化合物(2). 当用98%醋酸处理(1)不能获得(2). 而是重排成17α-羟基-16β, 17β-二甲基-D-高孕甾二烯二酮(3). 当化合物(1)和(2)与含有CaCl2的70%醋酸反应获得16β, 17β-二甲-D-高-4,9(11), 15-孕甾三烯-3,17-二酮, 其得率取决于CaCl2的浓度和反应时间.     

A highly stereoselective approach to the synthesis of functionalized pyran derivatives by Lewis acid assisted ketal reduction and allylation

Reduction of bicyclic ketal 1 gave functionalized pyran derivatives 7a or 7b in a highly stereoselective manner, depending upon the reduction conditions utilized. For example, treatment of ketal 1 with TiCl4/Et3SiH produced exclusively diol 7b with the 2,5-syn relationship in good yield. Alternatively, reduction of ketal 1 by DIBALH gave 2,5-anti-diol 7a stereoselectively. Alane reductions of ketal 1 were highly stereoselective also; however, the syn/anti selectivity observed was strongly dependent on the ratio of reagents employed for in situ generation of the alane. Lewis acid catalyzed allylation of ketal 1 gave pyran 10 in a stereospecific alkylation reaction.     

A pH-responsive fluorescent probe and photosensitiser based on a self-quenched phthalocyanine dimer

A self-quenched zinc(ii) phthalocyanine dimer linked with an acid-sensitive ketal unit has been prepared, which can be activated in an acidic environment (pH = 5.0-6.5) as a result of the cleavage of the ketal linker and separation of the phthalocyanine units, resulting in enhanced fluorescence emission and singlet oxygen production.     

缩醛/缩酮的合成研究进展

醛/酮与醇或原甲酸酯进行亲核加成反应生成的产物缩醛/缩酮,是一类重要的有机化合物。在有机合成中,该反应也广泛用于醛/酮羰基的保护或者乙二醇的保护,因此,缩醛/缩酮的合成研究引起广泛的关注。本文根据反应体系的不同,从酸催化、电催化和光催化三个方面对近年来缩醛/缩酮的合成研究进展进行详细综述。期望该综述作为学生基础有机化学课程的课后拓展阅读内容,能加深学生对基础反应的理解,培养学生的科研创新思维。     

Synthesis of the C1-C21 Fragment of the Serine/Threonine Phosphatase Inhibitor Tautomycin

Compound 40 containing the C-1-C-21 region of tautomycin has been synthesized. The two halves (4 and 5) of this spirocyclic section were each constructed using Matteson's chloromethylene insertion reaction. Cr/Ni-mediated coupling of compounds 4 and 5 resulted in a structure containing the C-1-C-21 section of tautomycin. Oxidation of the resultant allylic alcohol to the ketone and removal of the alpha,beta unsaturation yielded compound 39. Treatment with DDQ removed both PMB protecting groups and allowed the spirocyclic ketal to form producing compound 40, ready for further extension to the natural product tautomycin.     

Oxoferryl porphyrin/hydrogen peroxide system whose behavior is equivalent to hydroperoxoferric porphyrin

The reaction between H(2)O(2) and a pyridine-coordinated ferric porphyrin encapsulated by a cyclodextrin dimer yielded a hydroperoxoferric porphyrin intermediate, PFe(III)-OOH, which rapidly decomposed to oxoferryl porphyrin (PFe(IV)═O). Upon reaction with H(2)O(2), PFe(IV)═O reverted to PFe(III)-OOH, which was converted to carbon monoxide-coordinated ferrous porphyrin under a CO atmosphere. PFe(IV)═O in the presence of excess H(2)O(2) behaves as PFe(III)-OOH.     

钨硅酸的制备及其在催化合成缩酮(醛)中的应用

本文探讨了钨硅酸的制备方法,以合成环己酮1,2-内二醇缩酮为例验证钨硅酸的催化活性,并探讨了合成其它缩酮（醛）的适宜条件,得到的收率分别为：环己酮1,2-丙二醇缩酮85．5％、环己酮乙二醇缩酮89．6％、丁酮乙二醇缩酮79．5％、丁醛乙二醇缩醛89．1％、丁醛1,2丙二醇缩醛81．5％。     

Reinvestigation of the stevens rearrangement of 1-benzyl-1,3,4-trimethyl-1,2,5,6-tetrahydropyridinium salts. II. Synthesis of 2-aryl-3-isopropenyl-1,3-dimethylpyrrolidines

cis-2-Aryl-3-isopropenyl-1,3-dimethylpyrrolidines Ha and IIb have been synthesized by an unambiguous way, thus confirming the structure of the methylene derivatives obtained as by-products in the Stevens rearrangement of 1-benzyl-1,3,4-trimethyl-1,2,5,6-tetrahydropyridinium salts Ia and Ib. The synthesis is based on the acid-induced intramolecular cyclization between an iminium salt and the α-position of a ketal group. Thus, condensation between amino ketal XXI, prepared via Gabriel synthesis from 5-chloro-3-methyl-2-pentanone, and the appropriate aldehyde afforded imines XXI. Their treatment with dry hydrogen chloride followed by acid hydrolysis and methylation gave 3-acetylpyrrolidines IV, which were transformed into the isopropenyl derivatives II by reaction with methyl-lithium and further dehydration.     

Selective Ketalization of Steroidal 3,11,17-Trione using Chlorotrimethylsilane as Catalyst

Selective ketalization of 13β-ethyl-gona-4-ene-3,11,17-trione (1) using chlorotrimethylsilane as catalyst afforded 13β-ethyl-gona-5-ene-3,11,17-trione-3-ethylene ketal (2) in fairly high yield. The corresponding 3,17-diethylene ketal (3) was obtained in 70% yield when p-toluenesulfonic acid was used as catalyst.