Synthesis of carboxy-2,2-dimethylchromans and chromenes

The condensation of hydroxybenzoic acids, viz., 2,5-dihydroxy-, 3,5-dihydroxy-, 3,4,5-trihydroxy- and 2,4,6-trihydroxybenzoic acid with 2-methyl-but-1,3-diene (isoprene) in presence of orthophosphoric acid giving corresponding carboxy-2,2-dimethylchromans is described. 2,2-Dimethylchromans have been dehydrogenated withDDQ to give corresponding carboxy-2,2-dimethylchromenes.     

Synthesis of 6-carboxy-2,2-dimethylchromans and chromenes

The condensation of hydroxybenzoic acids and their methyl esters with isoprene in the presence of orthophosphoric acid gives corresponding 2,2-dimethylchromans, which can be dehydrogenated with DDQ or NBS to give the corresponding 6-carboxy-2,2-dimethylchromenes. The synthesis of β-tubaic acid, a natural compound, has also been achieved.     

Synthesis of 2,2-dimethylchromans by the hydrogenation of 2,2-dimethyl-2H-chromenes

Summary 2,2-Dimethylchromans19–36 have been synthesized by the hydrogenation of 2,2-dimethyl-2H-chromenes1–18 in acetic acid solution in the presence of 10% Pd-C catalyst.Dedicated to Prof. Dr. W. Fleischhacker on the occasion of his 60th birthday     

Nuclear isoprenylation of polyhydroxyacetophenones : Acid catalysed condensation with isoprene

A novel method of nuclear isoprenylation leading to the exclusive formation of 2,2-dimethylchromans has been achieved by the direct condensation of polyhydroxyacetophenones with isoprene in presence of phosphoric acid. Acetylchromans, thus obtained, are dehydrogenated with DDQ to given corresponding 2,2-dimethylchromenes. Using this method, synthesis of number of naturally occurring chromenes, viz. ripariochromene A (6), eupatoriochromene (10), encecalin (11), isoevodionol (16), evodionol (17) and methylevodionol (18) has been affected.     

HPW and supported HPW catalyzed condensation of aromatic aldehydes with aniline: Synthesis of DATPM derivatives

The mesoporous Si-MCM-41 was synthesized by hydrothermal method and various wt.% (20 and 30 wt.%) of HPW were loaded on Si-MCM-41 by wet impregnation method. The synthesized Si-MCM-41 and HPW-loaded catalysts were characterized by XRD, BET surface area, FT-IR, TEM and TGA–DTG techniques. The catalytic activity of the catalyst was tested over the condensation reaction of aniline with various aromatic aldehydes at refluxing temperature under liquid-phase condition, which yields highly commercial product namely diamino triphenyl methanes (DATPMs). The effects of various parameters like catalyst, mole ratio, solvents and substituent effect on the formation of DATPMs were optimized. The catalytic activity of the catalysts showed the following order: H₃PW₁₂O₄₀·nH₂O > H₃PMo₁₂O₄₀·nH₂O > H₄SiW₁₂O₄₀·nH₂O > 20 wt.% HPW/MCM-41 > 30 wt.% HPW/MCM-41 > HM (12) > Hβ (8) > HY (4) > HZSM-5 (15) > Al-MCM-41 (25). The results showed that mole ratio of 4:1 (aniline:aldehyde) gave higher yield than the other mole ratios. Acetonitrile and ethyl acetate shows better activity especially in the supported materials than toluene was used as a solvent. The product thus obtained was analyzed by ¹H NMR, FT-IR techniques.     

二氧化锡纳米粒子催化四组分Hantzsch缩合合成多氢喹啉衍生物(英文)

Tin dioxide (SnO2 ) nanoparticles efficiently catalyzed unsymmetrical four-component Hantzsch condensations of various aldehydes, dimedone, ethyl acetoacetate, and ammonium acetate to form polyhydroquinoline derivatives in excellent yields. This novel method offers several advantages over the traditional method of synthesizing these compounds, including safety, mild conditions, short reaction times, high yields, and an easy workup.     

Acid catalyzed aldol condensation in the gas phase

The gas phase reaction of acetaldehyde with a Brønsted acid in a chemical ionization source yields protonated crotonaldehyde, as shown by its collisional activation mass spectrum. This is thus analogous to the well known aldol condensation in solution, in which the initial aldol adduct loses water to yield crotonaldehyde. The possibility of a common mechanism for the gas phase and solution reactions is discussed.     

Atom transfer radical polymerization and copolymerization of isoprene catalyzed by copper bromide/2,2'-bipyridine

ATRP, as one of the most successful controlled/‘‘living' radical polymerization techniques, has been applied to a large variety of monomers including styrenes,(meth)acrylates,(meth)acrylamides,acrylonitrile, and vinyl acetate. However, ATRP of isoprene still remains a challenge due to poor solubility of copper catalysts in isoprene and low chain propagation rate constant of the monomer. In this work,Cu Br/2,2'-bipyridine was found to effectively mediate ATRP of isoprene at 100 °C, 130 °C, and 150 °C with ethyl 2-bromopropionate as an initiator. The polymerizations proceeded smoothly and reached 48.1%,53.3%, and 71.0% conversions, respectively, in 72 h, producing polyisoprenes with molecular weights close to theoretical values and relatively narrow distributions. A block copolymer of polystyrene-bpolyisoprene was prepared using Cu Br/2,2'-bipyridine as a catalyst and polystyrene as a macroinitiator.The ~1H NMR and ~(13)C NMR analysis of polyisoprene indicated that the polymer had 88.8% 1,4-addition structure and 63.9% of the polymer backbone units were in trans-configuration.     

Benzaldehyde lyase catalyzed enantioselective self and cross condensation reactions of acetaldehyde derivatives

Flexible protected 1,3,4-trihydroxy-2-butanone is synthesized in high enantiomeric excesses by using asymmetric homo- and cross- acyloin coupling of aliphatic aldehydes catalyzed by benzaldehyde lyase.     

Acid catalyzed Knoevenagel condensation of thiobarbituric acid and aldehyde at room temperature

Abstract

Knoevenagel reactions have been performed by the action of various unsymmetrical thiobarbituric acids containing activated methylene carbon and electron deficient center of aromatic aldehydes using small amount of acetic acid as initiator in ethanolic medium. The present protocol proceeded smoothly on room temperature stirring using ethyl alcohol as solvent with the help of initiator. The work-up procedure is very simple and products have been purified by simple recrystallization. Thus rendering the methodology is good and all synthesized molecules were characterized by ¹H, ¹³C NMR, and MS spectra.     

P-TSA catalyzed facile and efficient synthesis of polyhydroquinoline derivatives through hantzsch multi-component condensation

A facile and efficient synthetic route to polyhydroquinolines has been developed via four-component condensation reactions of aldehydes, dimedone, ethyl acetoacetate and ammonium acetate in the presence of p-toluenesulfonic acid (p-TSA) catalyst in ethanol at ambient temperature through Hantzsch reaction. Simple work-up procedure, environmentally friendly, inexpensive and non-toxic catalyst, shorter reaction times along with excellent product yields are the significant features of this practical method.     

Synthesis of chiral benzacridone derivatives by three-component condensation

A three-component condensation of (2-bornylidene)acetaldehyde and 2-naphthylamine with various, in particular, dissymmetrical, cyclic β-diketones afforded derivatives of 12-(2-bornylidene)methyl-8,9,10,12-tetrahydro-7H-benzo[a]acridin-11-one containing in the structure three and more asymmetrical carbon atoms. Steric factors govern the prevailing formation of (12R)-isomers of benzacridones (R/SH ≈ 7: 5) and the orientation of the substituents of the cyclohexenone fragment. These factors ensure also the regiospecificity of the reaction leading exclusively to the formation of 8,9-disubstituted benzacridones at the use of 4,5-disubstituted cyclohexane-1,3-diones.     

Synthesis of cis-1,4-bifunctional derivatives of an isoprene δ-sultone

Conclusions The stereospecific transformation of a,-unsaturated -sultone into derivatives of (Z)-4-hydroxy-2-methylbut-2-ene-1-sulfonic acid has been carried out.For the preliminary report see [1].Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1354–1358, June, 1981.     

Synthesis of 2,2′-bipyrimidine derivatives

A new total synthesis of 2,2′ -bipyrimidine derivatives by the direct condensation of 2-amidinopyrimidinebenzenesulfonate with dicarbonyl compounds is described. The following 2,2′-bipyrimidines have been prepared: 5-ethyl-4,6-dihydroxy-2,2′-bipyrimidine; 5-ethyl-4,6-dichloro-2,2 -bipyrimidine; 4,6-dihydroxy-2,2′ -bipyrimidine; 5-ethyl-4,6-dimethoxy-2,2′ -bipyrimidine.     

5－磺基水杨酸催化两相法合成某些二茂衍生物

首次利用5－磺基水杨酸作为催化剂合成了9种二茂钛衍生物,经元素分析,UV－vis,IR及^1HNMR等对配合物结构进行了表征,并利用电子吸收光谱对取代水杨酸参与反应的机理进行了探讨,同时发现,5－磺基水杨酸水溶液也可用于二氯二茂钛的分离,并且非常有效。     

Synthesis of methyl-substituted 1,7-phenanthroline derivatives by condensation of 2-methylquinolin-5-amine with aromatic aldehydes and cyclic 1,3-diketones

Previously unknown 7-aryl(hetaryl)-3-methyl-7,10,11,12-tetrahydro-9H-benzo[b][1,7]phenanthrolin-8-ones and their 10,10-dimethyl-substituted analogs were synthesized by three-component condensation of 2-methylquinolin-5-amine with aromatic aldehydes and cyclic β-diketones (cyclohexane-1,3-dione and dimedone) in butyl alcohol.