Synthesis and study of substituted coumarins. A facile preparation of D,L-o-tyrosine

A general procedure for the preparation of aminocoumarins and aminohydroxycoumarins under mild conditions is described. Amino- and acetamidoaminocoumarins were prepared by reduction of the corresponding nitro derivatives with sodium borohydride in the presence of 10% palladium on charcoal. Acid hydrolysis of the acetamidoaminocoumarins with (a) concentrated hydrochloric acid in ethanol, or (b) with 1N hydrochloric acid under reflux, gave diaminocoumarins and aminohydroxycoumarins, respectively. Condensation of the ethyl ester of glycine with salicylaldehyde gave 3-salicylideneaminocoumarin (XIII), the Schiff base of 3-aminocoumarin (XII). Acid hydrolysis of XIII under the above mentioned conditions, (a) and (b), gave XII and 3-hydroxycoumarin (XVI), respectively. Hydrogenation of compound XIII in dioxane or in dimethylformamide with 10% palladium on charcoal gave 3-salicylaminocoumarin (XVII), while hydrogenation of XII, XIII or XVII in acetic acid with traces of water and palladium black gave the amino acid o-tyrosine.     

A facile preparation of vinyl sulfides

Vinyl sulfides are formed in high yield by the alkylation of trimethylsiloxy mercaptides.     

A facile preparation of imidazolinium chlorides

A process for the preparation of symmetric and unsymmetric imidazolinium chlorides that involves reaction of a formamidine with dichloroethane and a base (a) is described. This method makes it possible to obtain numerous imidazolinium chlorides under solvent-free reaction conditions and in excellent yields with purification by simple filtration. Alternatively, symmetric imidazolinium chlorides can be prepared directly in moderate yields from substituted anilines by utilizing half of the formamidine intermediate as sacrificial base (b).     

A facile preparation of 2,6-diarylpyrazines

2,6-Diarylpyrazines were prepared in good yields by a novel method of condensing methoxycarbonylhydrazine with N,N-bis(arylcarbonylmethyl)-p-toluenesulfonamides, unsymmetrical derivatives of which were synthesized by a new (or different) procedure. The structures of these 2,6-diarylpyrazines were established by spectral data and X-ray diffraction analysis. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:341–345, 1998     

A facile preparation of backbone-substituted, functionalized and chiral imidazolinium salts

A versatile and modular method for the preparation of various backbone-substituted, functionalized and chiral imidazolinium salts from the reaction of formamidines with alkene oxides has been described, providing a more straightforward access to substituted imidazolinium salts than the previously reported methods.     

A facile one-step preparation of chlorofluoromethylene olefins

The “insitu” reaction of triphenylphosphine, fluorotrichloromethane, zinc dust, and an aldehyde or ketone in dimethylformamide at 60°C provides a facile one-step synthesis of chlorofluoromethylene olefins. A study of representative examples of carbonyl compounds demonstrates that this approach gives yields of olefinic products comparable to other more elaborate or expensive synthetic routes. It should prove to be synthetically useful for the preparation of chlorofluoromethylene olefins from aldehydes and reactive ketones.     

A facile preparation of differentiated 1,2-divinylcycloalkanols

A method is described which permits one-step conversion of 2-chlorocycloalkanones to differentiated 1,2-divinylcycloalkanols, 2-vinylcycloalkanones, or 2-vinylcycloalkanols.     

A facile preparation of selenohydantoins using isoselenocyanate

Reactions of isoselenocyanate with methyl aminoacetate hydrochlorides in the presence of triethylamine afforded selenohydantoins, 2‐selenoxoimidazolidin‐4‐ones, in high yields.     

A facile preparation of trisubstituted amino-furan and -thiophene derivatives

β-Alkylation of amino-furan and -thiophene heterocycles is described through metal-, acid- and base-free carbon-carbon bond formation. The ability of both heterocycles to undergo selective β-alkylation is compared by mean of experimental and theoretical data. The presence of chiral amine substituents induced the diastereoselective generation of the newly formed additional stereocenter.     

Regular copolyamides. I. A facile method for the preparation of diamine-oxamides

α,ω-Diamine-oxamides with 2–12 CH₂ groups between the two amino groups were obtained by the reaction of the diamines and diethyl or dimethyl oxalate. Diethyl oxalate is added slowly to a substantial excess of diamine in the proper solvent over a period of time under controlled temperature conditions. All variables are very important for each individual diamine in order to obtain optimal conversions to the diamine-oxamides under the most favorable conditions. Diamine-oxamides were obtained in approximately 80% yield with only small amounts (5–10%) of the corresponding polyoxamides as the side product. Diamine-oxamides from diamines with less than six methylene groups are water-soluble. All diamine-oxamides show an alternation of their melting points and are useful intermediates for the preparation of regular copolyoxamides.     

A facile preparation of various N-heterocycles using amides and olefins

We herein report a one pot approach for the synthesis of various nitrogen containing heterocycles including: oxazolines, thiazolines, and dihydro dioxazines via the addition of amides to olefins in the presence of N-iodosuccinimide (NIS) and propionitrile at high temperatures. Thus, the reaction of aryl/heteroaryl amides, thioamides, N-hydroxybenzamide, and phenylurea with various olefins in the presence of NIS and propionitrile at 45 °C afforded the N-heterocycles in good to moderate yields. Reaction of the electron deficient tri-O-acetyl-d-glucal and tri-O-acetyl-d-galactal with benzamide and thiophene-2-carboxamide afforded the N-glycooxazolines in good yields. The newly made heterocycles were tested against various enzymes. Only 3,6-diphenyl-dihydro-1,4,2-dioxazine (1c) was found to moderately inhibit hexokinase II (hHK2).     

A facile and versatile preparation of bilindiones and biladienones from tetraarylporphyrins

Bilindiones and biladienones carrying aryl groups at the meso positions were prepared using coupled oxidation reactions of iron tetraarylporphyrins in 20-63% yield.     

Bisorthoesters as polymer intermediates. II. A facile method for the preparation of polybenzimidazoles

Aromatic bisorthoesters were found to be good polymer intermediates and could be condensed with aromatic tetramines under mild conditions, in DMSO at 100°C in a relatively short reaction time to give polybenzimidazoles. The hexapropyl orthoesters of terephthalic and isophthalic acid were the preferred aromatic orthoesters because they were relatively easily purified by vacuum distillation to polymer grade intermediates, since they are liquids. Higher orthoesters distill even under good vacuum near or above the decomposition temperature of the orthoester group. Hexaethyl orthooxalate was also used and is a very useful and stable derivative of oxalic acid, which can be used for condensation reactions. These three orthoesters were used for condensations with 3,3′,4,4′-tetraaminobiphenyl, 1,2,3,4-tetraaminobenzene, 3,3′,4,4′-tetraaminobiphenyl ether, and 3,3′,4,4′-tetraaminobenzophenone. All polybenzimidazoles were obtained in high to quantitative yields and with varying molecular weights (η_inh = 0.1?0.8 dl/g), which in some cases were in the fiber forming range.     

A facile and general method for the preparation of diaryltellurium dicarboxylates

Diaryltellurium dicarboxylates can be prepared by treatment of the corresponding dichlorides with carboxylic acids in the presence of silver oxide. The conversion of the dichlorides to the carboxylates can also be achieved through a more practical method employing a carboxylate anionic exchange resin. IR and PMR data are given.     

A facile and convenient method for the preparation of macrocyclic diamides

A number of macrocyclic diamides have been synthesized from the reaction of a diacid dicarboxylic dichloride with primary diamino compound in the presence of magnesium oxide-silica gel at room temperature in good yields. Using urea and thiourea as well as diamines to produce the corresponding macrocycles in the range of 52–56% yields are also included in this paper. One of the major advantages of this method is simple regeneration of inorganic solid and its reuse through several cycles without a decrease in activity.     

A facile preparation and visible light-induced photocatalysis of indium sulfide superstructure

β-In₂S₃ superstructure comprised of nanoflakes with the sizes of 200–450 nm has been synthesized by a facile reflux method with the assistance of the sodium dodecylsulfate at low temperature (80 °C). XRD, SEM, TEM, HRTEM, and UV–vis spectra were used to characterize the In₂S₃ superstructure. Prepared In₂S₃ superstructures exhibited high photocatalytic activities in the degradation of rhodamine B under visible light irradiation (λ > 420 nm), in which 97.5% RhB was photodegraded after 60 min.     

A facile one-pot preparation of potassium hydroxyaryl- and (hydroxyalkyl)aryltrifluoroborates

Potassium hydroxyaryl- and (hydroxyalkyl)aryltrifluoroborates have been prepared in a simple one-pot process from the corresponding hydroxy-substituted aryl halides in 51-98% yields through an in situ protection of the free hydroxyl group with t-BuLi. Also, we successfully performed a microwave-promoted Suzuki-Miyaura cross-coupling reaction of these substrates with aryl- and alkenyl bromides in the presence of 0.5 mol % of Pd(OAc)2 catalyst without ligands.     

A phosphorimidate rearrangement for the facile and selective preparation of allylic amines

Allylic phosphorimidates, readily prepared from the combination of an allylic alcohol, an azide, and a chlorophosphite, undergo [3,3]-rearrangement under thermal conditions to provide single isomers of allylic phosphoramidates. This new rearrangement is tolerant of a range of substitution patterns on the reactants. Treatment of the products of the rearrangement with ethanethiolate followed by acid produces a protected allylic amine. This strategy thus provides an attractive and versatile procedure for the preparation of key synthetic intermediates, allylic amines.