Synthesis of α-chloropolyfluoroalkyl ethers and acetals based on them

α-Chloropolyfluoroalkyl ethers were synthesized by the reaction of polyfluorinated alcohols H(CF₂CF₂) _n CH₂OH (n=1?3) with aliphatic aldehydes (ethanal, propanal, butanal) and hydrogen chloride. Yield of α-chloroethers decreases from 71 to 61% as the number of carbon atoms in the starting reactants increases. α-Chloropolyfluoroalkyl ethers react with polyfluorinated alcohols (n = 1?3) to form acetals in yield of up to 40–61%, and with methanol and ethanol, up to 98%.     

Orbital phase control of the conformations of α- and β-substituted enamines and vinyl ethers

The conformational stabilities of the α- and β-substituted enamines and vinyl ethers were predicted by orbital phase theory and confirmed by ab initio molecular orbital calculations. Cyclic interaction significantly occurs among the nonbonding orbital n _Y for the lone pair on the hetero atom Y (N in the enamines or O in the ethers), the π and π* orbitals of the CC bond, and the σ_C-H or σ*_C-X orbitals on the substituent CH₂X. The cyclic -n _Y-π-σ_C-H-π*- interaction is favored by the orbital phase continuity in the α-substituted molecules, while the cyclic -n _Y-π-σ*_C-X-π*- interaction is favored in the β-substituted molecules. The most stable conformation was then predicted to be synperiplanar or (pseudo)equatorial in the α-substituted molecules and anticlinical or (pseudo)axial in the β-substituted molecules. Received: 8 May 1998 / Accepted: 30 July 1998 / Published online: 16 November 1998     

Synthesis of symmetrical α-alkyl- and α-arylalkylbenzyl and diarylmethyl ethers by HCl-catalyzed intermolecular dehydration

α-Alkyl-, α-arylalkyl-, and α-aryl-substituted benzyl alcohols were converted into the corresponding symmetrical dibenzyl ethers in the presence of a catalytic amount of 10% aqueous HCl both in methylene chloride and under solvent-free conditions. Analogous reactions in dioxane and on heating afforded mainly the corresponding arylalkenes, whereas symmetrical dibenzyl ethers were formed as minor products.     

Synthesis of β-trifluoroacetyl-substituted vinyl sulfones and vinyl sulfides

Oxidation of -(trifluoroacetyl)vinyl sulfides afforded a series of the corresponding sulfones. The reactions of sulfones with various alkyl- and arylthiols were studied. These reactions provide the basis for a new procedure for the synthesis of -(trifluoroacetyl)vinyl sulfides.     

Synthesis and recognition properties of α-d-glucose-based fluorescent crown ethers incorporating an acridine unit

Two new chiral glucopyranoside-based crown ethers incorporating acridine fluorescent signalling units, 15-membered ligand 1 and 21-membered ligand 2 were synthesized. Their complexation properties toward alkali and alkali earth metal ions, and their enantioselectivity towards chiral ammonium salts were studied by absorption and fluorescence spectroscopic experiments. Macrocycle 1 formed 1:1 complexes with all the metal ions selected and the stability constants were low (lg K < 2.3). The cavity-size of 2 allowed only the complexaton of organic ammonium ions. Crown 2 showed chiral discrimination in case of all the four ammonium salts used as model guest compounds; the highest enantioselectivity (K(R)/K(S) ~3) was observed for the enantiomers of phenylethyl ammonium perchlorate. Ligand 2 forms much more stable complexes with metal ions; the highest stability constant was obtained for the Ca²⁺ complex (lg K = 6.15). The coordination of metal ions by ligand 2 was accompanied by marked fluorescence enhancement, whereas the binding of ammonium ions by the same species resulted in significant fluorescence quenching.     

Synthesis of new α-hydroxyphosphonates and α-acetoxyphosphonates

A series of new α-hydroxyphosphonate (5–14) have been synthesized in high yields by reaction of β-chloro-α,β-unsaturated aldehydes (1–4) and trialkyl phosphite in the presence of chlorotrimethylsilane at room temperature under solvent-free conditions. In addition, compounds (5–14) were reacted with acetic anhydride in DBU to give the new α-acetoxyphosphonate derivatives (15–23). All these phosphonates (5–23) were obtained as mixtures of two (E and Z) isomers and fully characterized by multinuclear (¹H, ¹³C, and ³¹P) NMR, IR spectroscopy and HRMS.     

Synthesis of substituted α,β-unsaturated δ-lactones from vinyl tellurides

A new approach for the synthesis of α,β-unsaturated δ-lactones, a unit present in many natural products with interesting biological activities is described. The approach was based on the use of a vinyl telluride, and it is complementary to the methods using ring-closing metathesis. The sequence was performed in good overall yield with retention of the Z-double bond geometry.     

γ-Rays-induced synthesis of hydrogels of vinyl ethers with stimuli-sensitive behavior

γ-Radiation method was applied to synthesize novel water-soluble and water-swelling polymers. Vinyl ether of ethylene glycol (VEEG), vinyl butyl (VBE) and vinyl isobutyl (VIBE) ethers were used as monomers. The synthesis of VEEG–VBE and VEEG–VIBE copolymers was carried out in a wide range of feed composition and absorbed dose. It was found that the hydrophobic–hydrophilic balance of the copolymers could be delicately varied by the copolymer composition as well as by the chemical structure of the alkyl substitute in the hydrophobic moiety. The copolymers exhibit thermo-sensitive behavior in water solutions. The value of transition temperature is considerably decreased at a higher concentration of the hydrophobic component in the copolymer composition.     

Additions of free dimethylgermylene to vinyl ketones and α-diketones

Derivatives of 1-oxa-2-germacyclopent-4-ene are obtained from germylenes with a number of cyclic or acyclic vinyl ketones, and 1,3-dioxa-2-germacyclopent-4-enes with different non-enolizable α-diketones. Structure-mechanism relationships are discussed.     

Synthesis and properties of Alkyl α-D-Galactopyranoside

Alkyl α-D-galactopyranosides are sugar-based nonionic surfactants, and it is necessary to research their structure–property relationships since it is not quite clear that the change of the alkyl chain length has effects on a series of physicochemical properties. Here, alkyl α-D-galactopyranosides were prepared by galactose and alcohols through three steps including acetylation, coupling with alcohols in the presence of a catalyst stannic chloride, and deprotection. Furthermore, their water solubility and other properties were investigated. Alkyl α-D-galactopyranosides (4a ～ 4e, n = 6 ～ 10) were water soluble, and their dissolution process in water was an endothermic process. Nonyl α-D-galactopyranoside (4d) showed excellent foaming ability and foam stability. Octyl α-D-galactopyranoside (4c) had the strongest emulsifying ability for toluene and nonyl α-D-galactopyranoside (4d) had the strongest emulsifying ability for rapeseed oil. The critical micelle concentration (CMC) values and surface tension at the CMC were decreasing with increasing alkyl chain length. Their standard free energy of adsorption (ΔG_ads) was more negative than their standard free energy of micellization (ΔG_mic). The moisture-absorption abilities were weakening with increasing alkyl chain length. Alkyl α-D-galactopyranosides (4a ～4f) were thermally stable below 280°C. Alkyl α-D-galactopyranosides (4c ～4f) had the optical texture of the thermotropic liquid crystal smectic A phase.     

Triarylaminium salt facilitated Friedel–Crafts reaction of indoles with enamides and vinyl ethers

Commercially available stable radical cation triarylaminium salt can be used as an efficient initiator for Friedel–Crafts reaction of indoles with enamides to regioselectively construct complex indole derivatives and for double Friedel–Crafts reaction of indoles with vinyl ethers to offer 3,3′-Bis(indolyl)alkane derivatives. The ready availability of the starting materials and the usefulness of the products make this strategy attractive.     

Synthesis of novel disulfide-bridged dilactam crown ethers

The novel macrocyclic dilactams with redox-switched disulfide linkage were synthesized.These compounds were obtained from 2,2'-dithiodibenzoyl chloride in the macrocyclization step by fast addition method in moderate yields.