Synthesis and properties of new chiral dopants containing a δ-lactone ring for practical ferroelectric liquid crystal mixtures

A series of new optically active δ-lactones were synthesized as chiral dopants for ferroelectric liquid crystals (FLCs). The response time of an FLC mixture containing 4 mol% (S)-2,2-dimethyl-5-[2-fluoro-4-(5-n-octylpyrimidin-2-yl)-phenoxy[methyl-δ-valerolactone was 25 μs at 25°C. (0-90 per cent change in light transmission, 10 V μm^-1). The synthesis and properties of these materials as practical chiral dopants are reported.     

Reactivity of a cyclic α-bromoiminium bromide towards nucleophiles

Piperidine-pyrrolidine ring contraction of 1-piperideinium bromide ( 1 ) was observed by reaction with aqueous bases, sodium methoxide, phenylhydrazine, (S)-1-phenylethylamine and sodium borohydride, whereas diazomethane addition mainly gave pyrrolo[3,4-b]pyridine derivative 8. Some stereochemical features of these reactions have been investigated. 1 gave back bromine under suitable conditions.     

Synthetic Studies towards Pseurotin A. Part 3. Synthesis of a related highly functionalized γ-lactone

A new general concept for the total synthesis of pseurotin A ( 1 ), a secondary metabolite of Pseudeurotium ovalis STOLK , which possesses a highly substituted 1-oxa-7-azaspiro[4.4]nonane skeleton, is presented. A key intermediate of the planned reaction sequence is the functionalized γ-lactone 8 . The corresponding protected compound 52 was prepared using (S)-O,O-isopropylideneglyceraldehyde ( 13 ) and the bromoacetal 14 as starting material. γ-Lactone 52 was obtained in enantiomerically pure state in ten steps. It possesses the desired configuration.     

The chemistry of coumarin derivatives,part 2. Reaction of 4-hydroxycoumarin with α,β-unsaturated aldehydes

4-Hydroxycoumarin (= 4-hydroxy-2H-1-benzopyran-2-one) reacts with enals to give 1,2- or 1,4-addition products, depending on the nature and relative location of the substituents on the olefinic double bond (Scheme 2). The resulting adducts further react intra- or intermolecularly, affording dimeric coumarins or pyranocoumarins in the case of 1,2-addition and acetalic pyranocoumarins in the case of 1,4-addition. With enals bearing alkyl groups at C(β), 2H-pyrano[3,2-c]coumarins are the only products formed, and the reaction represents an easy and straightforward entry into this class of recently described biologically active natural products.     

Quantum chemical study of several monocyclic complex β‐lactam C‐3, C‐4, and N‐derivatives,and β‐ring model molecules

A quantum chemical study of several complex monocyclic 4‐benzoyl‐4‐phenyl‐β‐lactam derivatives was carried out using cyclobutane, azetidine, 2‐azetidinone, 1‐methyl‐2‐azetidinone, and 3‐methyl‐2‐azetidinone as model compounds. The optimum geometry was obtained for the different conformations. The planarity of the ring was discussed in terms of the influence of the substituents on the amide resonance. To better analyze the amide resonance and the activity of the β‐lactam ring, a vibrational study was also carried out. To examine the influence of solvent polarity on the carbonyl bands, the Fourier transform–infrared (FT‐IR) spectra of the β‐lactam monocyclic derivatives were recorded in CCl₄, C₆H₆, and CHCl₃ solutions. The normal vibrations of the β‐lactam ring in the model compounds were characterized and used in the analysis of the β‐ring of more complex derivatives. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Synthesis,structural and conformational study of N-β(or γ)-acyloxyalkylnortropinones

A series of N-β(γ)-acyloxyalkylnortropinones have been synthesized and studied by ¹H and ¹³C nmr spectroscopy, and the crystal structure of N-[γ-(p-chlorophenylcarbonyloxy)propyl]nortropinone 4 has been determined by X-ray diffraction. The compounds studied display in deuteriochloroform solution the same preferred conformation. The pyrrolidine and piperidone rings adopt a flattened N-8 envelope and distorted chair conformation, puckered at N-8 and flattened at C-3 respectively, with the N-substituent in axial position with respect to the piperidone ring. These results are in close agreement with that found for compound 4 in the crystalline state.     

Synthesis and characterization of novel α- or β-tetra[6,7-dihexyloxy-3-(4-oxyphenyl)coumarin]-substituted metal-free and metallo phthalocyanines

The synthesis of novel phthalonitriles substituted at 3- or 4-position with 6,7-dihexyloxy-3-(4-oxyphenyl)coumarin were performed. The metal-free and metallo phthalocyanines (MPcs) (M = Zn, Co, Cu) were prepared by cyclotetramerization of 6,7-dihexyloxy-3-[p-(2′,3′-dicyanophenoxy)phenyl]coumarin or 6,7-dihexyloxy-3-[p-(3′,4′-dicyanophenoxy)phenyl]coumarin. The newly prepared compounds, phthalonitriles and Pcs, have been characterized by elemental analysis, ¹H NMR, ¹³C NMR, MALDI-TOF, IR, UV–Vis and fluorescence spectral data. The electronic spectra exhibit bands of coumarin identity along with characteristic Q and B bands of the Pc core. The IR-spectra of all Pcs showed three characteristic intense bands at 1709–1700 cm⁻¹ for lactone carbonyl, two bands at 1489–1604 cm⁻¹ for conjugated olefinic system.     

Synthesis,structural and conformational study of 4-α-(or β)-p-chlorobenzoyloxy-1-azaadamantane hydrochloride

4-α-(or β)-p-Chlorobenzoyloxy-1-azaadamantane hydrochloride have been synthesized and studied by ¹H and ¹³C nmr spectroscopy, and the crystal structure of the α-epimer has been determined by X-ray diffraction. Each ring of the adamantane cage system is a nearly perfect chair, the substituted cyclohexane and piperidine rings, in endo and exo position respectively, having the biggest deviation. From the ¹H and ¹³C nmr data, several stereoelectronic effects have been deduced.     

δ and σ vs. π conflicting aromatic pentagonal ring of tungsten with a planar pentacoordinate carbon at the ring center

Density functional theory calculations have predicted a planar dicationic nanocluster CW consisting of a five‐membered tungsten ring and a planar pentacoordinate carbon atom located at the ring center. Although the regular‐pentagonal tungsten ring has strong aromaticity as a whole in terms of a magnetic criterion, detailed analyses have suggested that it is conflicting d‐orbital aromaticity in which δ‐ and σ‐aromaticity coexist with relatively weak π‐antiaromaticity. The system is unique in that δ‐aromaticity is involved in conflicting aromaticity, as well as being found in a conjugated ring consisting of more than three metal atoms. Although the planar pentagonal cluster ion is not the global minimum on the potential energy surface of CW, molecular dynamics simulations suggest that the planar species is fairly stable under mild conditions. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Thioetherphenolate group 4 metal complexes in the ring opening polymerization of rac‐β‐Butyrolactone

Group 4 complexes 1 – 3 [ 1 = (t‐BuOS)₂Ti(O‐i‐Pr)₂; 2 = (t‐BuOS)₂Zr(O‐t‐Bu)₂; 3 = (t‐BuOS)₂Hf(O‐t‐Bu)₂] supported by two phenolate bidentate ligands (t‐BuOS‐H = 4,6‐di‐tert‐butyl‐2‐phenylsulfanylphenol) promote the well‐controlled ring opening polymerization of rac‐β‐butyrolactone. In presence of isopropanol, low dispersities and molecular weights proportional to the equivalents of isopropanol are achieved. Moreover, the zirconium complex is effective in the copolymerization of rac‐β‐butyrolactone with rac‐lactide. The 13 C nuclear magnetic resonance analysis revealed that the obtained copolymers have a tapered diblock microstructure consisting of an initial block composed of lactide sequences and a terminal block composed of butyrolactone sequences. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3132–3139     

Synthesis of new derivatives of β-carboline-hydantoin

Reaction of tetrahydro-β-carboline-3-carboxylic acids 4a-c with alkyl and phenyl isocyanates in acetone provide the corresponding 2,5-disubstituted 1,3-dioxo-6H-1,2,3,5,11,11a-hexahydroimidazo[1,5-b]-β-carbolines 2a-r .     

Diastereoselective michael addition of nitrogen and sulfur-nucleophiles to α,β-unsaturated δ-thiolactams

5,6-Dihydropyridine-2-thiones 2 are synthesized from 5,6-dihydropyridin-2-ones 1 and Lawesson reagent. Stereoselective Michael-like addition of amines, methylhydrazine or functionalized thiols affords trans piperidine-2-thiones 5 with the corresponding heterosubstituent in position 4 as major products. The configuration of the adducts 5 was determined by nmr-techniques.     

Synthesis of 2-(ω-aminoalkyl)imidazolin-4-ones by ring chain transformation of lactam derivatives with α-aminoamides

Reaction of N-methylamides of biogenic (S)-α-amino acids 3 with lactam acetals 1 or lactim ethers 2 gives three types of products, i.e. N-methyl-α-lactamiminoamides 5 by condensation, 2-(ω-aminoalkyl)imidazolin-5-ones 7 or 2-(ω-lactamimmoalkyl)imidazolin-4-ones 8 by ring chain transformation. All products represent novel optically active derivatives of biogenic α-aminoacids.     

Antiplatelet α-Methylidene-γ-butyrolactones: Synthesis and evaluation of quinoline,flavone, and xanthone derivatives

As a continuation of our previous studies on the synthesis and antiplatelet activity of coumarin derivatives of α-methylidene-γ-butyrolactones, certain quinoline, flavone, and xanthone derivatives were synthesized and evaluated for antiplatelet activity against thrombin (Thr)-, arachidonic acid (AA)-, collagen (Col)-, and platelet-activating factor (PAF)-induced aggregation in washed rabbit platelets. These compounds were synthesized from quinolin-8-ol, flavon-7-ol, and xanthon-3-ol, respectively, via alkylation and Reformatsky-type condensation (Schemes 1–3). By the comparison with comparison with coumarin α-methylidene-γ-butyrolactone 3a , flavone and xanthone derivatives, 3b and 3c , respectively, are more selective in which only AA- and collagen-induced aggregation are strongly inhibited. Most of the quinoline derivatives ( 9a–e ) exhibited broad-spectrum antiplatelet activities.     

γ,δ‐ and δ,ε‐Unsaturated Aldehydes from γ‐ and δ‐Lactones in One Step. Preliminary Communication

A one‐step transformation of γ‐ and δ‐(spiro)lactones into γ,δ‐ and δ,ε‐unsaturated aldehydes with an excess of formic acid in the vapor phase over a supported manganese catalyst is described for the first time. The scope and limitations of this new reaction are shown with different lactones as substrate, and a mechanistic rationale is proposed.