Catalyst-Free Decarboxylation of Carboxylic Acids and Deoxygenation of Alcohols by Electro-Induced Radical Formation

Electro-induced reduction of redox active esters and N-phthalimidoyl oxalates derived from naturally abundant carboxylic acids and alcohols provides a sustainable and inexpensive approach to radical formation via undivided electrochemical cells. The resulting radicals are trapped by an electron-poor olefin or hydrogen atom source to furnish the Giese reaction or reductive decarboxylation products, respectively. A broad range of carboxylic acid (1°, 2°, and 3°) and alcohol (2° and 3°) derivatives are applicable in this catalyst-free reaction, which tolerated a diverse range of functional groups. This method features simple operation, is a sustainable platform, and has broad application.     

Synthesis,thermal and structural characterization of alumina-based pillared α-Ti(IV)hydrogenphosphate

The intercalating properties of α-titanium hydrogenphosphate with general formula Ti(IV)(HPO₄)₂·H₂O (denoted as α-TiP in the following) have been evaluated by preparing two precursors, synthesized by intercalation of hydroalcoholic solutions of n-hexylamine and n-octylamine into the layers of α-TiP. The obtained precursors, slightly hydrolyzed, have interlayer distances two, three or four times larger then the starting material. Afterward, several alumina-pillared α-TiP derivatives were prepared by intercalation of an aluminum Keggin-type ion of general formula [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺, denoted as Al₁₃, into the layers of the precursors. No evidence of the presence of the previously intercalated amines was revealed by studying the thermal behavior of the so-prepared Al-intercalated materials that were subsequently calcined in air at 600 °C, thus providing thermally stable pillared alumina-based materials. BET surface areas on α-TiP-Al₂O₃ materials are not noticeable high (from 15 to 55 m² g^?1). However, the highest value is four times than that of α-TiP calcined at the same temperature (layered-TiP₂O₇). Finally, preliminary catalytic tests were performed on 1-butene isomerization at 450 °C for 80 min, and the results confirmed that Brönsted acid sites of the PO₃–OH groups of the starting materials not involved in the intercalation are responsible for the results obtained. It was also possible to preliminarily conclude that the strength of the acid sites is from medium to weak.     

3-(Dimethylamino)-2,2-dimethyl-2H-azirin als Aib-Äquivalent: Synthese von Aib-Oligopeptiden

3-(Dimethylamino)-2,2-dimethyl-2H-azirine as an Aib Equivalent; Synthesis of Aib Oligopeptides 3-(Dimethylamino)-2,2-dimethyl-2H-azirine ( 1 ) reacts with carboxylic acids at 0–25° to give 2-acylamino-N,N,2-trimethylpropionamides ( = 2-acylamino-N,N-dimethylisobutyramide, acyl-Aib-NMe₂) in excellent yields (Scheme 2 and 3). Examples of α-amino-, α-hydroxy-, and α-mercapto-carboxylic acids are given. On treatment with HCl in toluene, the terminal dimethylamide group is selectively converted to the corresponding carboxylic acid (→acyl-Aib) via an amide cleavage (Scheme 4 and 5); 1,3-oxazol-5(4H)-ones are intermediates of this amide hydrolysis. This reaction sequence has been used for the extension of peptide chains (Scheme 6). The synthesis of Aib-oligopeptides using this methodology is described (Scheme 8).     

3-(Dimethylamino)-2,2-dimethyl-2H-azirin als α-Aminoisobuttersäure(Aib)-Äquivalent: Cyclische Depsipeptide durch direkte Amid-Cyclisierung

3-(Dimethylamino)-2,2-dimethyl-2H,-azirine as an α-Aminoisobutyric-Acid (Aib) Equivalent: Cyclic Depsipeptides via Direct Amid Cyclization In MeCN at room temperature, 3-(dimethylamino)-2,2-dimethyl-2H-azirine ( 1 ) and α-hydroxycarboxylic acids react to give diamides of type 8 (Scheme 3). Selective cleavage of the terminal N,N-dimethylcarboxamide group in MeCN/H₂O leads to the corresponding carboxylic acids 13 (Scheme 4). In toluene/Ph SH , phenyl thioesters of type 11 are formed (see also Scheme 5). Starting with diamides 8 , the formation of morpholin-2,5- diones 10 has been achieved either by direct amide cyclization via intermediate 1,3-oxazol-5(4H)-ones 9 or via base-catalyzed cyclization of the phenyl thioesters 11 (Scheme 3). Reaction of carboxylic acids with 1 , followed by selective amide hydrolysis, has been used for the construction of peptides from α-hydroxy carboxylic acids and repetitive α-aminoisobutyric-acid (Aib) units (Scheme 4). Cyclization of 14a, 17a , and 20a with HCI in toluene at 100° gave the 9-, 12-, and 15-membered cyclic depsipeptides 15, 18 , and 21 , respectively.     

Total Synthesis of (±)-Clovene. On the Stereoelectronic Requirements of the α-Alkynone Cyclisation

The synthesis of the sequiterpenoid tricyclic hydrocarbon (±)-cleovene ( 1 ) by application of the α-alkynone cyclisation is described. The starting bicyclic carboxylic acid 2 was obtained from ethyl 3-methyl-2-oxocyclohexane-1-carboxylate by modified known methods (24%) and converted to the α-alkynone 3 (86%). The thermolysis of 3 in the gas phase at 620° selectively produced the tricyclo[6.3.1.0^1,5] dodecenone 4 (80%) which was converted to 1 (37%) by conventional procedures. The selectivity of the α-alkynone cyclisation is discussed in terms of the stereoelectronic requirements (coplanarity factor) of the carbene insertion. In order to throw further light on the importance of this factor, the (1-adamantyl) alkynone 16 was synthesised from adamantane-1-carboxylic acid (78%) and subjected to thermolysis at 620°. Since this led to the tetracyclo[6.3.1.1.1^3,10.0^3,7]tridecenones 17 and 18 (together 72%), we conclude that the planar carbene insertion transition state, while preferred, is not a stringent requirement.     

Crystal structure and packing analysis of the liquid crystal dimer alpha,omega-bis(4-cyanobiphenyl-4-yloxy)octane

The crystal structure of the liquid crystal dimer α,ω-bis(4-cyanobiphenyl-4'-yloxy)octane has been determined from diffraction data obtained with synchrotron radiation. The structure is triclinic, with the space group P-1 with Z = 2 and the unit cell parameters are a= 7.135(5) Å, b= 12.811(5) Å, c= 15.639(5) Å, α= 75.800(5)°, β= 84.690(5)°, γ= 77.930(5)°. The flexible spacer linking the mesogenic groups is in the all-trans-conformation. Although the molecule has a potential centre of symmetry, it occupies a general position in the cell; this unusual behaviour has been investigated with the aid of a theoretical evaluation of the packing energy.     

Synthesis of 2-Aminocarboxylic Acids on the Basis of Metalated Lithium Acylates

2-Aminocarboxylic acids have been synthesized through the reaction of lithium acylate α-carbanions with alkyl nitrites to form α-hydroxyiminoacylates, followed by reduction of the latter with tin chloride. The reactions of lithium acylate α-carbanions, generated by the metalation of carboxylic acids with lithium diisopropylamide at 35–40°С in THF under argon, with alkyl nitrites at 45–50°С give 2-hydroxyiminocarboxylic acids in 55–97% yields. The reduction of 2-hydroxyiminocarboxylic acids with tin(II) chloride in conc. HCl at 20–25°С leads to 2-aminocarboxylic acid hydrochlorides in 52–94% yields.     

Target‐Specific Capture of Environmentally Relevant Gaseous Aldehydes and Carboxylic Acids with Functional Nanoparticles

Aldehyde and carboxylic acid volatile organic compounds (VOCs) present significant environmental concern due to their prevalence in the atmosphere. We developed biodegradable functional nanoparticles comprised of poly(d,l ‐lactic acid)‐poly(ethylene glycol)‐poly(ethyleneimine) (PDLLA‐PEG‐PEI) block co‐polymers that capture these VOCs by chemical reaction. Polymeric nanoparticles (NPs) preparation involved nanoprecipitation and surface functionalization with branched PEI. The PDLLA‐PEG‐PEI NPs were characterized by using TGA, IR, ¹H NMR, elemental analysis, and TEM. The materials feature 1°, 2°, and 3° amines on their surface, capable of capturing aldehydes and carboxylic acids from gaseous mixtures. Aldehydes were captured by a condensation reaction forming imines, whereas carboxylic acids were captured by acid/base reaction. These materials reacted selectively with target contaminants obviating off‐target binding when challenged by other VOCs with orthogonal reactivity. The NPs outperformed conventional activated carbon sorbents.     

Dielectric relaxations in poly(vinylidene fluoride)

Molecular motions in poly(vinylidene fluoride) were studied by the dielectric technique. Three distinct absorption peaks (α_c, α_a, and β) were observed in the frequency range from 0.1 cps to 300 kcps and in the temperature range from ?66 to 100°C. The molecular mechanisms for these absorptions and their temperature dependence are discussed, and results are compared with x-ray diffraction and the NMR measurements. It is concluded that the α_c absorption located at 97°C (1 kcps) is related to molecular motion in the crystalline region. The α_a absorption located at ?27°C (1 kcps) can be interpreted as due to the micro-Brownian motion of the amorphous main chains. The β absorption located at ?47°C (1 kcps) is attributed to local oscillation of the frozen main chains.     

A Novel Hatching Enzyme from Starfish Asterias amurensis: Purification, Characterization, and Cleavage Specificity

Hatching enzyme (HE) is of importance to degrade egg membrane to let the larvae be free. HE was purified and characterized from starfish blastula. The specific activity and the purification ratio of the purified HE with 110.9 kDa of molecular weight were 449.62 U/mg and 7.42-fold, respectively. Its optimal pH and temperature for activity were pH?8.0 and 30 °C, respectively. This enzyme was relatively stable in the range of pH?4.0–6.0 and 30–40 °C. This enzyme was inhibited by ethylene diamine tetraacetic acid (EDTA) and ethylene glycol tetraacetic acid, and also done moderately by Leupeptin, tosyl-lysine chloromethyl ketone, tosyl-phenylalanine chloromethyl ketone, and phenyl-methanesulfonyl fluoride. Zn²⁺ ion activated HE activity strongly and recovered the EDTA-pretreated activity more than did Ca²⁺, Mg²⁺, and Cu²⁺. Based on the results above, the starfish HE was classified as a zinc metallo- and trypsin-like serine protease. The values of Km, Vmax, and Kcat of the starfish HE on dimethyl casein were 0.31 mg/ml, 0.17 U/ml, and 122.70 s^?1, respectively, whereas 1.09 mg/ml, 0.12 U/ml, and 771.98 s^?1 on type I collagen. Therefore, the starfish HE could be a potential cosmeceutical because of its strong cleavage specificity on type I collagen.     

Generation and Reactivity of C(1)-Ammonium Enolates by Using Isothiourea Catalysis

C(1)-Ammonium enolates are powerful, catalytically generated synthetic intermediates applied in the enantioselective α-functionalisation of carboxylic acid derivatives. This minireview describes the recent developments in the generation and application of C(1)-ammonium enolates from various precursors (carboxylic acids, anhydrides, acyl imidazoles, aryl esters, α-diazoketones, alkyl halides) using isothiourea Lewis base organocatalysts. Their synthetic utility in intra- and intermolecular enantioselective C−C and C−X bond forming processes on reaction with various electrophiles will be showcased utilising two distinct catalyst turnover approaches.     

Synthesis of optically pure α-halo-α′-sulphinyl-ketones

When optically pure sulphinyl carbanions are reacted at ?75°C with α-chloro or α-bromo carboxylic acid esters addition on the carboxyl group occurs and corresponding α-halo-α′-sulphinyl-ketones are obtained in optically pure form.     

N‐[Tris(hydroxymethyl)methyl]glycine (tricine)

The title compound, C₆H₁₃NO₅, adopts a zwitterionic form where the carboxylic acid H atom is transferred to the amino group. The methyl–glycine backbone is planar. The tris(hydroxy­methyl)­methyl group is rotated as a rigid group around the amino–methyl bond by 22 (1)° and the carboxylic acid plane is rotated by 19.76 (12)° from the plane of the main skeleton. Apart from their H atoms, the three hydroxy­methyl groups adopt a propeller‐like conformation around the amino–methyl bond, close to C₃ symmetry.     

混配配合物[Cu(2-mpac)(SCN)(H2O)•H2O]n的合成、结构与磁性研究

在水溶液中以Cu(NO3)2•3H2O, 2-mpac和KSCN反应得到了一个通过硫氰酸根桥连的混配配合物[Cu(2-mpac)(SCN)(H2O)•H2O]n (1) (2-mpac: 5-methylpyrazine-2-carboxylic acid), 利用元素分析, 红外光谱, 单晶X射线衍射, X射线粉末衍射以及热重分析对配合物1进行了表征. 晶体学数据: 三斜晶系, P-1空间群, a＝0.5567(2) nm, b＝1.0339(3) nm, c＝1.0532(3) nm, α＝64.030(2)°, β＝77.620(3)°, γ＝85.945(3)°, V＝0.5321(3) nm3, Z＝2, S＝1.061, 最终偏离因子[I＞2σ(I)] R1＝0.0444, wR2＝0.0905, 对于全部数据R1＝0.0647, wR2＝0.0988. 变温磁化率研究表明配合物1中的Cu(II)离子之间存在弱的反铁磁相互作用.     

Synthesis of novel α-acyloxycarboxamides containing vinylbis(silanes) through three-component Passerini reactions

A three-component efficient procedure is described for the synthesis of novel α-acyloxycarboxamides containing bis(trimethylsilyl)ethenyl group from 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde, aromatic carboxylic acids and isocyanides, via the Passerini reaction. This reaction proceeds smoothly and cleanly under mild conditions in H₂O and [bmim]BF₄ at room temperature and led to products in good yields. The silylated aldehyde was obtained via Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyllithium in THF at 0 °C.     

Thermische Lactonisierung von Estern γ-Brom-α, β-ungesättigter Carbonsäuren zu Δα-Butenoliden. Direkte γ-Bromierung von α, β-ungesättigten Säuren

By heating with iron powder at 120–150° some γ-bromo-α, β-unsaturated carboxylic methyl esters, and, less smothly, the corresponding acids, were lactonized to Δ^7alpha;-butenolides with elimination of methyl bromide. The following conversions have thus been made: methyl γ-bromocrotonate ( 1c ) and the corresponding acid ( 1d ) to Δ^α-butenolide ( 8a ), methyl γ-bromotiglate ( 3c ) and the corresponding acid ( 3d ) to α-methyl-Δ^α-butenolide ( 8b ), a mixture of methyl trans- and cis-γ-bromosenecioate ( 7c and 7e ) and a mixture of the corresponding acids ( 7d and 7f ) to β-methyl-Δ^α-butenolide ( 8c ). The procedure did not work with methyl trans-γ-bromo-Δ^α-pentenoate ( 5c ) nor with its acid ( 5d ). Most of the γ-bromo-α, β-unsaturated carboxylic esters ( 1c, 7c, 7e and 5c ) are available by direct N-bromosuccinimide bromination of the α, β-unsaturated esters 1a, 7a and 5a ; methyl γ-bromotiglate ( 3c ) is obtained from both methyl tiglate ( 3a ) and methyl angelate ( 4a ), but has to be separated from a structural isomer. The γ-bromo-α, β-unsaturated esters are shown by NMR. to have the indicated configurations which are independent of the configuration of the α, β-unsaturated esters used; the bromination always leads to the more stable configuration, usually the one with the bromine-carrying carbon anti to the carboxylic ester group; an exception is methyl γ-bromo-senecioate, for which the two isomers (cis, 7e , and trans, 7d ) have about the same stability. The N-bromosuccinimide bromination of the α,β-unsaturated carboxylic acids 1b , 3b , 4b , 5b and 7b is shown to give results entirely analogous to those with the corresponding esters. In this way γ-bromocrotonic acid ( 1 d ), γ-bromotiglic acid ( 3 d ), trans- and cis-γ-bromosenecioic acid ( 7d and 7f ) as well as trans-γ-bromo-Δ^α-pentenoic acid ( 5d ) have been prepared. Iron powder seems to catalyze the lactonization by facilitating both the elimination of methyl bromide (or, less smoothly, hydrogen bromide) and the rotation about the double bond. α-Methyl-Δ^α-butenolide ( 8b ) was converted to 1-benzyl-( 9a ), 1-cyclohexyl-( 9b ), and 1-(4′-picoly1)-3-methyl-Δ^α-pyrrolin-2-one ( 9 c ) by heating at 180° with benzylamine, cyclohexylamine, and 4-picolylamine. The butenolide 8b showed cytostatic and even cytocidal activity; in preliminary tests, no carcinogenicity was observed. Both 8b and 9c exhibited little toxicity.     

CRYSTAL AND MOLECULAR STRUCTURE OF A DIPHENYL SULFOXIDE COMPLEX WITH CERIUM NITRATE, Ce(N0_3)_3[(C_6H_5)_2SO]_4

<正> The title complex crystallises in the triclinic, space group PT with two formula units in a unit cell of dimensions a=11.182(4), b=14.357(5), c=17.362(6) A and α= 84.08(3)°, β=72.79(3)°, r= 69.27(2)°, Dx=1.51 g.cm-3, V=2489.6(15) A3. The final index for 6319 observed reflections is 0.0274. The Ce3+ ion is coordinated by ten oxygen atoms with Ce-O distances varying from 2.469 to 2.706 A. The three nitrate groups are all bidentate ligands.     

The rearrangement of some 2-substituted-4-bromo-2,5-dinitro-6-hydroxy-3,6-dimethylcyclohex-3-en-1-ones

In chloroform at 20°, or in tetrachloroethylene at 120°, the title compounds (1) rearrange to give the α-diketone(2), the structure of which was determined by X-ray crystal structure analysis; a possible rearrangement mechanism is outlined.     

Direct lactonization of α-amino γ,δ-unsaturated carboxylic acid esters via olefin activation: stereo- and regioselective production of homoserine lactone scaffolds having contiguous stereocenters

Triflic acid-mediated stereoselective direct lactonization of a variety of α-amino γ,δ-unsaturated carboxylic acid esters and the construction of new γ-butyrolactone structural motifs are reported. Several α-amino γ,δ-unsaturated carboxylic acid esters underwent stereo- and regioselective 1,5-cyclization and afforded a variety of highly substituted homoserine lactone scaffolds having contiguous stereocenters. The direct lactonization of the chiral α-amino γ,δ-unsaturated carboxylic acid esters with triflic acid led to the enantioselective synthesis of the novel homoserine lactones. A plausible mechanism for the direct lactonization of α-amino γ,δ-unsaturated carboxylic acid esters is presented. The stereochemistry of major isomers 3f, 7a, 7b, and 7d was unambiguously established from the X-ray structure analysis.     

Synthesis and structure of Mu-4, the new layered aluminophosphate [(C2H5)2NH2]4[Al8P10O40H2]·[H2O]2.5

The title compound (named Mu-4) is a new layered aluminophosphate with a unusual A1/P ratio for this kind of materials. Mu-4 was obtained from a quasi non-aqueous mixture involving mainly diethylformamide (DEF) as solvent, in addition to limited amounts of water. DEF is decomposed during the synthesis and the resulting protonated diethylamine is occluded in the as-synthesized material. The crystal structure was determined by single crystal X-ray diffraction. The symmetry is triclinic, a=8.632(4) Å, b=9.267(7) Å, c= 17.461(10) Å, α=86.66(5)°, β=82.20(4)° and γ=89.28(5)°, space group P-1. The structure consists of anionic double sheets essentially built from double 4-ring (D4R) units. The inorganic layers are in strong interaction with water and the protonated amine which is located in the interlayer spacing. Another type of diethylamine protrudes into the 8-membered rings (8-MR) present in the layers. The characterization of this new aluminophosphate by ¹³C, ²⁷Al and ³¹P solid state NMR spectroscopy is also reported.