Amino Acids as a Chiral Pool: Synthesis of (S)‐and (R)‐2‐N‐Carbomethoxy‐5‐aminoindane from (S)‐ and (R)‐Phenylalanines

Enantioselective syntheses of (R)‐and (S)‐2‐N‐carbomethoxy‐5‐aminoindanes from (R)‐ and (S)‐phenylalanines, respectively, are described. A Friedel–Crafts reaction employing N‐carbomethoxy phenylalanine leads to chiral 2‐N‐carbomethoxy‐1‐indanone, which is diastereoselectively reduced to 1‐hydroxy‐2‐N‐carbomethoxyindane. After protection of the hydroxyl group, a regioselective nitration gives a 6‐nitroindane intermediate, which upon hydrogenation affords (R)‐or (S)‐2‐N‐carbomethoxy‐5‐aminoindane.     

Sulfur‐Containing Chiral Bis(oxazolines) Tested in Copper‐Catalyzed Asymmetric Cyclopropanation

The novel C₂‐symmetric sulfur‐containing chiral bis(oxazoline) compound has been synthesized and characterized by X‐ray crystallography. Highly enantioselective and diastereoselective cyclopropanation reactions have been performed using the copper‐bis(oxazoline) catalyst.     

Efficient Synthesis of 2‐(N‐Substituted)‐2‐imidazolines and 2‐(N‐Substituted)‐1,4,5,6‐tetrahydropyrimidines

A general method for the preparation of 2‐(N‐Substituted)‐2‐imidazolines and 2‐(N‐Substituted)‐1,4,5,6‐tetrahydropyrimidines is described. These heterocycles can be synthesized from their respective anilines with 2‐chloro‐2‐imidazoline or 2‐chloro‐1,4,5,6‐tetrahydropyrimidine, generated in situ from imidazolidin‐2‐one and tetrahydropyrimidin‐2(1H)‐one activated by dimethyl chlorophosphate, in good to excellent yields.     

Organic Reactions in Ionic Liquids: Ionic Liquid Promoted Knoevenagel Condensation of Aromatic Aldehydes with (2‐Thio)Barbituric Acid

Abstract

The Knoevenagel condensation of aromatic aldehydes with (2‐thio)barbituric acid proceeded efficiently in reusable ionic liquids, EAN, BmimBF₄, and BmimPF₆ at room temperature in the absence of any catalyst with high yields.     

Cyclization of N,N′‐Bis(Salicylidene)Diamines with Carbon Suboxide

Abstract

The reaction between N,N′‐bis(salicylidene)diamines and carbon suboxide afforded dicoumarinoyl diamides in only one step and in yields that strictly depend on the methylene linkers between the salicylic moieties.     

Synthesis and Fluorescence of N,N,N‐Trimethyl‐2‐[methyl(7‐nitrobenzo[c][l,2,5]oxadiazol‐4‐yl) amino]ethanaminium Iodide,a pH‐Insensitive Reporter of Organic Cation Transport

A synthesis of the title compound, its characterization, and the pH dependence of its fluorescence properties are described. This compound serves as a pH‐insensitive real‐time reporter of organic cation transport in biological systems.     

Axially Dissymmetric Chiral (R)-N,N′-Bis(2-hydroxy-3,5-di-tert-butyl-arylmethyl)-1,1′-binaphthalene-2,2′-diamine as Chiral Ligands in the Reaction of Diethylzinc to Aldehydes

ＩｎｔｒｏｄｕｃｔｉｏｎＡｘｉａｌｌｙｄｉｓｓｙｍｍｅｔｒｉｃ 1,1′ ｂｉｎａｐｈｔｈｙｌａｎｄ 1,1′ ｂｉ ｐｈｅｎｙｌｌｉｇａｎｄｓｂｅａｒｉｎｇｔｗｏｉｄｅｎｔｉｃａｌｇｒｏｕｐｓｉｎｔｈｅ 2 ,2′ ｐｏｓｉｔｉｏｎｈａｖｅｐｒｏｖｅｄｔｏｂｅｒｅｍａｒｋａｂｌｙｕｓｅｆｕｌｉｎｅｎａｎｔｉｏｓｅ ｌｅｃｔｉｖｅｃａｔａｌｙｓｉｓ ,ｗｉｔｈｏｐｔｉｃａｌｙｉｅｌｄｓｃｌｏｓｅｔｏ 10 0 %ｅｎａｎ ｔｉｏｍｅｒｉｃｅｘｃｅｓｓ (ｅｅ)ｏｂｔａｉｎｅｄｉｎｓｅｖｅｒａｌｐｒｅｐａｒａｔｉｖｅｌｙｉｍ ｐ…     

Ce(SO4)2‐Mediated Nitration of N,N‐Dialkylanilines with NaNO2 in Water

Ce(SO₄)₂‐mediated nitration of N,N‐dialkylanilines with NaNO₂ using water as the solvent has been achieved in good to excellent yields. The nitrating reaction proceeded smoothly at ambient temperature.     

Efficient Synthesis of Primary Amides from Carboxylic Acids Using N,N′-Carbonyldiimidazole and Ammonium Acetate in Ionic Liquid

A novel and efficient method for the conversion of carboxylic acids to primary amides using N,N′-carbonyldiimidazole in combination with ammonium acetate/triethyl amine system in [BMIM]BF₄ is developed.      

Facile Synthesis and Unusual Methanesulfonylation Reaction of (2R,3R)‐1,4‐Dimethoxy‐1,1,4,4‐tetrasubstituted‐2,3‐butanediols

A facile method for the synthesis of (2R,3R)‐1,4‐dimethoxy‐1,1,4,4‐tetrasubstituted‐2,3‐butanediols involving oxidative cleavage of benzylidene acetal as a key step is described. These sterically hindered diols unusually formed cyclic sulfites as the major product under methanesulfonylation reaction conditions.     

One‐Pot Resolution of trans‐2‐Iodo‐cyclohexanol with O,O′‐Dibenzoyl‐(2R,3R)‐tartaric Acid in Solid Phase

A one‐pot, solid‐state resolution of racemic‐trans‐2‐iodo‐cyclohexanol by O,O′‐dibenzoyl‐(2R,3R)‐tartaric acid was performed. By mixing the solid racemate with half an equivalent resolving agent, the (1R,2R)‐isomer of the alcohol remains uncomplexed and can be sublimated at lower temperature. By increasing the temperature, the complex decomposes and the (1S,2S)‐isomer can be gained as a second fraction of the sublimation and the resolving agent remains back.     

Brønsted Acidic Ionic Liquid: An Efficient and Reusable Catalyst for the Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones

A novel ionic liquid, 3‐carboxymethyl‐1‐methylimidazolium bisulfate (CMImHSO₄), was synthesized and used as a recyclable catalyst for the Biginelli reaction under solvent‐free conditions. High yields of various substituted 3,4‐dihydropyrimidin‐2(1H)‐ones (or thiones) were obtained. The ionic liquid can be recovered and recycled easily without loss of activity.     

A Novel and Facile Method to Synthesize (R)‐ and (S)‐2‐methylpiperazine

Abstract

A concise and efficient synthesis of (R)‐ and (S)‐2‐methylpiperazine in only five steps from (D)‐ and (L)‐alanine is described. The key step is reaction of benzylamine with a bifunctional molecule to build a six‐membered ring.     

Synthesis of (R)‐Japonilure and (4R,9Z)‐9‐Octadecen‐4‐olide,Pheromones of the Japanese Beetle and Currant Stem Girdler

Asymmetric total synthesis of the sex pheromones of Japanese beetle and currant stem girdler, (R)‐japonilure (1) and (4R,9Z)‐9‐octadecen‐4‐olide (2), has been achieved.     

Spectroscopy and stereochemistry of the optically active copper(II), cobalt(II) and nickel(II) complexes with Schiff bases N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(3-methylbenzylideneiminato) and N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(5-methylbenzylideneiminato)

Schiff bases obtained from N,N′-(1R,2R)-1,2-cyclohexanediamine and 2-hydroxy-3-methylbenzaldehyde, 2-hydroxy-5-methylbenzaldehyde, have been used as ligands for copper(II), cobalt(II) and nickel(II). The complexes were characterized with UV–Vis, circular dichroism (CD), infrared, diamagnetic and paramagnetic ¹H NMR spectroscopy. CD spectra revealed exciton coupled π→π* transitions. Assignments of LMCT and d–d transitions in CD spectra of Ni(II), Co(II) and Cu(II) complexes is proposed. CD data are characteristic for central ion tetrahedral distortion from the planarity and λ conformation of the cyclohexane ring. ¹H NMR of Ni(II) complexes exhibited significant coordination shifts of CHN and ring protons which are in the closest proximity to Ni(II). The ¹H NMR paramagnetic spectra of Co(II) complexes revealed the most upfield shifted resonance at −60 ppm assigned to CHN and −28 ppm to hydrogen atom at C(5′) of the phenyl ring. Results of spectral analyses suggest central ions in a distorted square-planar geometry with N₂O₂ chromofore group.     

Raman study of a liquid crystalline gel consisting of photochromic 4‐methyl‐N‐(4‐n‐heptyloxysalicylidene)aniline and a gelling agent (R,R′)‐1,2‐bis(dodecanoylamino)cyclohexane

A liquid crystalline physical gel has been prepared from the mixture of a nematic liquid crystal and a low molecular mass gelling agent containing a hydrogen‐bonding moiety. The newly synthesized liquid crystalline compound exhibited photochromism in the crystalline solid phase. Although photochromism was not observed in the nematic gel state of the mixture, the lifetime of photochromism in the solid phase became longer, compared with that of a single liquid crystalline compound. Some Raman bands of the mixture showed a marked change in both intensity and frequency through the phase transitions. These bands have been assigned to the vibrational modes related to the core part of molecule.     

Acid‐Promoted Thioacetalization in Water using 2‐(1,3‐Dithian‐2‐ylidene)malonic Acid as an Odorless and Efficient Thioacetalization Reagent

Thioacetalization using 2‐(1,3‐dithian‐2‐ylidene)malonic acid 1 as a nonthiolic, odorless 1,3‐propanedithiol equivalent promoted by p‐dodecylbenzenesulfonic acid in water has been achieved. A range of selected carbonyl compounds 2 was converted into the corresponding dithioacetals 3 in high yields. Moreover, the thioacetalization showed high chemoselectivity between aldehydes and ketones.     

Novel Synthesis and Characterization of 1,3‐Bis(2‐dihydrothiazolyl)thiaalkoxy‐p‐tert‐butylcalix[4]arenes

A novel series of 1,3‐bis(2‐dihydrothiazolyl)thiaalkoxy‐p‐tert‐butylcalix[4]arenes generated by the reaction between 4,5‐dihydrothiazole‐2‐thiol and the different dibromide calix[4]aryl groups have been synthesized and structurally characterized by IR, ¹H NMR, ¹³C NMR, and MS. From their analytical data, it was found that compounds 8, 9, and 10 had cone conformations, whereas compound 11 existed as a mixture conformation. To verify the structure of the synthetic compounds, a single‐crystal X‐ray structure of compound 8 was obtained.