Liquid‐phase synthesis of mixture‐based bicyclic β‐lactam libraries

Five sets of 27‐membered combinatorial libraries of alicyclic β‐lactams were prepared via liquid‐phase Ugi 4‐center 3‐component reactions (U‐4C‐3CR) utilizing 3 different cis β‐amino acids, 3 different isonitriles and 5×3 sets of aldehydes. Through combinations of the building blocks of one of these libraries, all of the possible sublibraries were also generated. A few azetidinone derivatives were synthesized individually by parallel synthesis.     

Substituted pyridopyrimidinones, 1: Convenient PTC alkylation and halogenation of 2‐hydroxy‐4H‐pyrido[1,2‐a]pyrimidin‐4‐one

Alkylation of 2‐hydroxy‐4H‐pyrido[1,2‐a]pyrimidin‐4‐one ( 1 ) was investigated under solid–liquid phase transfer catalysis conditions (PTC), using tetrabutylammonium bromide and potassium carbonate. The reaction with alkyl halides led to the formation of various 2‐alkoxy products, in fair yields. Reaction of compound 1 with epichlorohydrin and chloroacetonitrile, under the same PTC conditions, afforded novel O1,O3‐disubstituted glycerol and oxazolopyridopyrimidone betaine derivatives, respectively. Some 3‐halo‐, 3,3‐dihalo, and/or 2,3‐dihalopyrido[1,2‐a]pyrimidines were also prepared using different halogenating agents at different reaction conditions. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:19–27, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20245     

Synthesis of 5‐methyl‐4‐oxo‐2‐(coumarin‐3‐yl)‐N‐aryl‐3,4‐dihydrothieno[2,3‐d]‐pyrimidine‐6‐carboxamides

Possible approaches to synthesis of 5‐methyl‐4‐oxo‐2‐(coumarin‐3‐yl)‐N‐aryl‐3,4‐dihydrothieno[2,3‐d]pyrimidine‐6‐carboxamides 4 have been discussed. It is shown that the preferable approach is cyclization of 2‐iminocoumarin‐3‐carboxamides 1 , utilizing 5‐amino‐3‐methyl‐N²‐arylthiophene‐2,4‐dicarboxamides 2 as binucleophilic reagents. The proposed procedure allowed us to easily obtain 4 in two stages, using common reagents. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:341–346, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20303     

Synthesis and characterization of a thermotropic liquid‐crystalline poly[2,5‐bis(4′‐alkoxycarbonylphenyl) styrene]

We report the synthesis and characterization of a series of novel mesogen‐jacketed liquid‐crystalline polymers, poly[2,5‐bis(4′‐alkoxycarbonylphenyl)styrene]s ( 1‐m , where m is the number of carbon atoms in the alkyl tails), along with the corresponding monomers, 2,5‐bis(4′‐alkoxycarbonylphenyl)styrenes ( 2‐m ), and their precursors, 2,5‐bis(4′‐alkoxycarbonylphenyl)toluenes ( 3‐m ). The influence of the tail length on the thermotropic properties of the two types of low‐molecular‐mass compounds and macromolecules was investigated with a combination of differential scanning calorimetry, polarized optical microscopy, and wide‐angle X‐ray diffraction techniques. Except for compound 3‐3 , which exhibited a monotropic nematic phase, all members of the low‐molar‐mass molecules developed no mesophase during both heating and cooling processes. The glass‐transition temperatures of the polymers decreased as the tail lengths increased. The 5% weight loss temperatures of all the polymers under a nitrogen atmosphere were above 360 °C, indicating quite high thermal stability. Although polymers 1‐1 and 1‐2 were non‐liquid‐crystalline, columnar nematic phases were observed for the remaining homopolymers with longer alkyl tails. The mesophases of 1‐3 to 1‐9 that developed at high temperatures remained upon cooling to room temperature, whereas those of 1‐10 to 1‐12 disappeared during the cooling process. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 830–847, 2007.     

One‐pot synthesis of novel substituted pyrrolo[2,3‐d]pyrimidines using dry media

A convenient solvent‐free one‐pot synthesis of 1,3,5,7‐tetraaryl‐1,3,4,7‐tetrahydro‐2‐thio‐xopyrrolo[2,3‐d]pyrimidin‐4‐one derivatives using supported reagents under microwave irradiation is described. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:617–621, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20355     

Cp2ZrCl2‐catalyzed synthesis of 2‐substituted quinozolin‐4(3H)‐ones

Zirconocene dichloride (Cp₂ZrCl₂) in the presence of DMF was found to be a highly efficient catalyst for the synthesis of structurally diverse 2‐substituted quinozolin‐4(3H)‐ones by reaction of anthranilimide with a wide range of aryl aldehydes. Copyright © 2013 John Wiley & Sons, Ltd.     

Microwave‐assisted synthesis of novel 4‐N,N‐dimethylamino‐ and 4‐cycloamino‐ substituted 1,2,4‐triazole‐3‐thiones

4‐N,N‐Dimethylamino‐ and 4‐cycloamino‐5‐phenyl‐1,2,4‐triazole‐3‐thiones 1–13 have been synthesized from benzhydrazides and substituted methyl dithiocarbazates under various conditions including short microwave irradiations. The last method seemed faster than the classical refluxing one. The influence of base and solvent types on the reaction direction has been also examined. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:188–195, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20594     

Original recyclization of S‐phenacyl derivatives of 4‐acylamino‐2‐mercapto‐1,3‐oxazoles and their analogues

Readily accessible acylamino(chloro)acetophenones, if treated with sodium rhodanide and α‐halogenocarbonyl compounds, provide 4‐acylamino‐5‐aryl‐2‐mercapto‐1,3‐oxazole derivatives which undergo recyclization on heating in polyphosphoric acid to give substituted 1,3‐thiazol‐2(3H)‐ones or 1,3‐thiazolidin‐2,4‐diones containing 2‐alkyl(aryl)‐5‐aryl‐1,3‐oxazol‐4‐yl residues at the N³ atom. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:432–437, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20317     

Temperature dependence of the phase separation in ethyl cyanoethyl cellulose/poly(acrylic acid)/4′‐n‐pentyl‐4‐cyano‐biphenyl composite films

A novel polymer‐dispersed liquid‐crystal film consisting of micrometer‐scale liquid‐crystal droplets in ultraviolet‐cured polymer composite matrices with cholesteric order was prepared and the influence of cure temperature on the phase separation was studied. The existence and pitch of the ethyl cyanoethyl cellulose cholesteric liquid‐crystalline phase were influenced by the existence of low molecular weight liquid crystals. The macromolecular cholesteric phase disappeared when the 4′‐n‐pentyl‐4‐cyano‐biphenyl concentration was over 40 wt %, and 4′‐n‐pentyl‐4‐cyano‐biphenyl domains were dispersed in the isotropic matrix of the polymer composite. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1334–1341, 2002     

Microwave induced synthesis of the thiazolidine‐2,4‐dione motif and the efficient solvent free‐solid phase parallel syntheses of 5‐benzylidene‐thiazolidine‐2,4‐dione and 5‐benzylidene‐2‐thioxo‐thiazolidine‐4‐one compounds

Novel microwave induced method for the synthesis of thiazolidine‐2,4‐dione motif under solvent phase conditions is developed. Further we report an efficient, microwave assisted method for the parallel syntheses of biologically important 5‐benzylidene‐thiazolidine‐2,4‐dione and 5‐benzylidene‐2‐thioxothiazolidine‐4‐one compounds under solid‐phase and solvent‐free conditions. A comparative study between the developed microwave methods and the conventional methods is described. We have also illustrated the possible mechanism behind to address the reason why piperidine, acetic acid and silica gel enhanced the Knoevenagel condensation reaction.     

Microwave‐Assisted One‐Pot Synthesis of Substituted 3‐Bromoimidazo[1,2‐a]pyridines and Imidazoheterocycles

Herein, an efficient, one‐pot microwave‐assisted synthesis of a diverse set of 3‐bromoimidazo[1,2‐a]pyridines is being reported with good yields (40–85%). The method involves electrophilic aromatic bromination using bromodimethylsulfonium ion generated in situ via oxidation of HBr salt by DMSO. This methodology was also applied to the synthesis of related imidazoheterocycles. Copyright © 2014 HeteroCorporation     

Synthesis of polyallene‐based graft copolymer via 6‐methyl‐1,2‐heptadien‐4‐ol and styrene

A series of well‐defined graft copolymers with a polyallene‐based backbone and polystyrene side chains were synthesized by the combination of living coordination polymerization of 6‐methyl‐1,2‐heptadien‐4‐ol and atom transfer radical polymerization (ATRP) of styrene. Poly(alcohol) with polyallene repeating units were prepared via 6‐methyl‐1,2‐heptadien‐4‐ol by living coordination polymerization initiated by [(η³‐allyl)NiOCOCF₃]₂ firstly, followed by transforming the pendant hydroxyl groups into halogen‐containing ATRP initiation groups. Grafting‐from route was employed in the following step for the synthesis of the well‐defined graft copolymer: polystyrene was grafted to the backbone via ATRP of styrene. The cleaved polystyrene side chains show a narrow molecular weight distribution (M_w/M_n = 1.06). This kind of graft copolymer is the first example of graft copolymer via allene derivative and styrenic monomer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5509–5517, 2007     

Efficient synthesis of 1‐substituted‐4‐phenyl‐1, 4‐dihydro‐5H‐tetrazole‐5‐thione and (1‐phenyl‐1H‐tetrazol‐5‐yl)thioacetyl derivatives

A new and convenient synthesis of a variety of N‐ and S‐substituted tetrazoles has been developed via azide and Mannich reaction methods. Compounds were characterized by elemental analysis, MALDI MS, and ¹H NMR data. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:637–643, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20353     

Synthesis of 4‐(5‐aryl‐1,3,4‐oxadiazol‐2‐yl)phenyl‐hydrazine derivatives from 3‐(4‐hydrazinocarbonyl‐phenyl)sydnones

The synthesis of potential fluorescent active 4‐(5‐aryl‐1,3,4‐oxadiazol‐2‐yl)phenylhydrazine derivatives was accomplished in three steps. The key step was the dehydration cyclization of 1,2‐diacylhydrazines to form the 1,3,4‐oxadiazole ring by use of acetic anhydride/perchloric acid mixture as the dehydrating agent. The sydnone moiety served as the masked hydrazines, which could be demasked by HCl for further application. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:438–442, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20318     

Magnetic field effects on the polymerization of 6‐N,N‐dioctylamino‐1,3,5‐triazine‐2,4‐dithiol

Electrochemical polymerization of monosodium salt ( 1b ) of 6‐N,N‐dioctylamino‐1,3,5‐triazine‐2,4‐dithiol on stainless steels was investigated in zero (0T), perpendicular (5T⊥), and parallel (5T//) magnetic fields which are arranged perpendicular and parallel to the direction of electrolytic current. 5T⊥ magnetic field enhances the formation rate of poly(6‐N,N‐dioctylamino‐1,3,5‐triazine‐2,4‐disulfide) 2 films but suppresses the crystallinity of 2 . However, 5T// magnetic field enhances the formation rate and the crystallinity. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:60–64, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20257     

Synthesis,characterization, and cross‐linking of a library of statistical copolymers based on 2‐“soy alkyl”‐2‐oxazoline and 2‐ethyl‐2‐oxazoline

The synthesis of statistical copolymers consisting of 2‐ethyl‐2‐oxazoline (EtOx) and 2‐“soy alkyl”‐2‐oxazoline (SoyOx) via a microwave‐assisted cationic ring‐opening polymerization procedure is described. The majority of the resulting copolymers revealed polydispersity indices below 1.30. The reactivity ratios (r_EtOx 1.4 ± 0.3; r_SoyOx = 1.7 ± 0.3) revealed a clustered monomer distribution throughout the polymer chains. The thermal and surface properties of the pEtOx‐stat‐SoyOx copolymers were analyzed before and after UV‐curing demonstrating the decreased chain mobility after cross‐linking. In addition, the cross‐linked materials showed shape‐persistent swelling upon absorption of water from the air, whereby as little as 5 mol % SoyOx was found to provide efficient cross‐linking. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5371,–5379, 2007     

Microwave‐induced Stereoselectivity in Synthesis of trans‐4‐Aryl‐3‐methyl‐6‐oxo‐4,5,6,7‐tetrahydro‐2H‐pyrazolo[3,4‐b]pyridine‐5‐carbonitriles

A facile synthesis of trans isomers of 4‐aryl‐3‐methyl‐6‐oxo‐4,5,6,7‐tetrahydro ‐ 2H ‐ pyrazolo[3,4‐b]pyridine‐5‐carbonitriles via three‐component condensation reaction of an aldehyde, 3‐amino‐5‐methylpyrazole and ethyl cyanoacetate in acetonitrile has been developed under microwave irradiation. This one‐pot reaction proceeds without any catalyst in short times and gives the product in high selectivities and high yields.     

Synthesis of Precursors of 4‐Phosphino‐1H‐pyrrole‐3‐carbaldehyde Derivatives

In this work, possible approaches to the synthesis of 1,2,5‐substituted 4‐phosphoryl‐3‐formylpyrroles have been considered. As a result, two methods for the synthesis of 4‐(diphenylphosphoryl)‐1‐(4‐ethoxyphenyl)‐2,5‐dimethyl‐1H‐pyrrole‐3‐carbal‐dehyde were proposed; the highest yields gives formylation of 3‐(diphenylphosphorothioyl)‐1‐(4‐ethoxyphenyl)‐2,5‐dimethyl‐1H‐pyrrole. The formyl fragment was successfully converted into a Schiff base with phenethylamine, and the phosphoryl group has been reduced to phosphine with silicochloroform, which suggests a promising approach to the synthesis of chiral bidentate phosphine ligands. © 2013 Wiley Periodicals, Inc. Heteroatom Chem 24:146–151, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21069     

A ‘one pot’ synthesis of 2‐aryl‐4H‐1‐benzopyran‐4‐ones under coupled microwave phase transfer catalysis (PTC) and ultrasonic irradiation PTC

A ‘one pot’ synthesis of 2‐aryl‐4H‐1‐benzopyran‐4‐ones (3a‐3f) is being reported. A mixture of o‐hydroxyacetophenone, aroyl chloride, powdered n‐tetrabutylammonium hydrogensulphate (n‐TBAHSO₄) and potassium hydroxide (KOH) were either irradiated by microwaves or sonicated in an ultrasonic cleaning bath to afford flavones directly. On the contrary, conventional liquid‐liquid Phase Transfer Catalysis (PTC) using benzene as organic phase and aqueous KOH as the second phase afforded first β‐diketones in accordance with Baker‐Venkataraman synthesis which upon cyclization by p‐toluenesulphonic acid (p‐TSA) gave desired flavones in the next step. PTC coupled with microwaves or ultrasound show enhanced yields, the clean reaction conditions require less time, and have easier workup protocol. All synthesized compounds were characterized by their Proton Magnetic Resonance (PMR), IR, FAB Mass and elemental analyses.