N,N,N,N-Tetramethyl-1,3-propanediamine as the catalyst of choice for the Baylis-Hillman reaction of cycloalkenone: rate acceleration by stabilizing the zwitterionic intermediate via the ion-dipole interaction

N,N,N^′,N^′-Tetramethyl-1,3-propanediamine (TMPDA) can be used as an efficient catalyst for the Baylis-Hillman reaction of cycloalkenones. The increased reaction rate was thought be derived from the stabilizing effect of the zwitterionic intermediate via the ion-dipole interaction.     

Acyclic tertiary diamines and 1,4,7,10-tetraazacyclododecane with fluorine-containing β-diketones: Leading to low melting ionic adducts

N,N,N′,N′-Tetramethylmethanediamine (1a), N,N,N′,N′-tetramethylethanediamine (1b), N,N,N′,N′-tetramethyl-1,3-propanediamine (1c), and N,N,N′,N′-tetramethyl-1,6-hexanediamine (1d) were reacted at 25 °C with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (2a), 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedione (2b), 2-thenoyltrifluoroacetone (2c), and 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione (2d) to form the ionic adducts 3-18. 1,4,7,10-Tetraazacyclododecane (1e) reacted at 25 °C with β-diketones (2a-d) and 1,1,1-trifluoro-2,4-pentanedione (2e) to give ionic solids 19-23 in good yields. Some of the products are liquid at 25 °C and are thermally stable over long liquid ranges as determined by thermal gravimetric analyses. Single-crystal X-ray structure determinations show that compounds 9 and 21 crystallize in the monoclinic space groups P2(1)/c and P2(1)/n, respectively. All the new compounds were characterized by ¹H, ¹⁹F and ¹³C NMR, electrospray MS and/or elemental analyses.     

Synthesis of a solvent-sensitive highly fluorescent derivative of perfluorocyclopentene

A solvent-sensitive highly fluorescent compound, N-[2-(1′,3′,4′,4′,5′,5′-hexafluorocyclopentenyl)]-4-(5-methoxy-thiazolyl)pyridine (1D) was synthesized as an unexpected product of the reaction of 4-bromo-5-methoxy-2-(4-pyridyl)thiazole (1B) with perfluorocyclopentene in the presence of n-BuLi. Primary mechanism of this reaction was proposed, and the photophysical properties of 1D in different solvents were studied.     

N,N′,N″-Tri-Boc-guanidine (TBG): a common starting material for both N-alkyl guanidines and amidinoureas

In this Letter, we describe the unexpected reaction pattern of N,N′N″-tri-Boc-guanidine (TBG) with amines at room temperature and under reflux conditions affording N-substituted guanidines and amidinoureas, potentially important compounds with extensive applications in medicinal chemistry. This investigation shows that TBG is an excellent, readily available common starting material for the synthesis of various N-alkyl guanidines as well as N-alkyl-N′-substituted amidinoureas by simply manipulating the reaction conditions.     

Catalytic photocarboxylation of 1,1-diphenylethylene with N,N,N′,N′-tetramethylbenzidine and carbon dioxide

Photocarboxylation of 1,1-diphenylethylene with N,N,N′,N′-tetramethylbenzidine (TMB) in MeCN under bubbling of CO₂ proceeded with high catalytic efficiency, giving 3,3-diphenylacrylic acid (DPA) and 3-hydroxy-3,3-diphenylpropionic acid (20). The turnover number (TON=(DPA+20)/TMB) reached 17. Similarly, 1-phenyl-1-cyclohexene yielded cis-2-acetamido-2-phenylcyclohexanecarboxylic acid with TON 5.9. As compared with related N,N-dimethylaniline derivatives, TMB is more resistant to photodecomposition, has the much larger absorbance in the S₀→S₁ transition, and has the lower quenching efficiency by CO₂. Probably these factors are partly responsible for the high TON observed for TMB.     

Rapid synthesis of optically active poly(amide-imide)s by direct polycondensation of aromatic dicarboxylic acid with aromatic diamines

4,4^′-(Hexafluoroisopropylidene)-N,N^′-bis(phthaloyl-l-leucine-p-amidobenzoic acid) (2) was prepared from the reaction of 4,4^′-(hexafluoroisopropylidene)-N,N^′-bis(phthaloyl-l-leucine) diacid chloride with p-aminobenzoic acid. The direct polycondensation reaction of monomer (2) with p-phenylenediamine (2a), 4,4^′-diaminodiphenylsulfone (2b), 2,4-diaminotoluene (2c), 2,6-diaminopyridine (2d), m-phenylene diamine (2e), benzidine (2f), 4,4^′-diaminodiphenylether (2g) and 4,4^′-diaminodiphenyl methane (2h) was carried out in a medium consisting of triphenyl phosphite, N-methyl-2-pyrolidone, pyridine, and calcium chloride. The homogeneous mixture was heated at 220 °C for 1 min under nitrogen. The resulting poly(amide-imide)s (PAIs) having inherent viscosities 0.27-0.78 dl/g were obtained in high yield and are optically active and thermally stable. All of the above polymers were fully characterized by IR spectroscopy, elemental analyses and specific rotation. Some structural characterization and physical properties of this new optically active PAIs are reported.     

Flow-injection spectrophotometry of vanadium by catalysis of the bromate oxidation of N,N'-bis(2-hydroxyl-3-sulfopropyl)-tolidine

A highly sensitive flow-injection method is proposed for the catalytic determination of vanadium(V) at sub-nanogram per milliliter levels using a new indicator reaction. The method is based on the catalytic effect of vanadium(V) on the bromate oxidation of N,N′-bis(2-hydroxyl-3-sulfopropyl)-tolidine. 1,2-Dihydroxybenzene-3,5-disulfonate was used as an activator in the vanadium(V)-catalyzed reaction and significantly enhanced the sensitivity of the method. Vanadium(V) in the range 0.01-3.0 ng ml⁻¹ was easily determined with sampling rate of about 30 h⁻¹. Vanadium(IV) could be also determined. The limit of detection (S/N=3) was 0.008 ng ml⁻¹ and the relative standard deviations were 1.4 and 1.6% for ten determinations of 0.2 ng ml⁻¹ vanadium(IV) and vanadium(V), respectively. Interferences from metal ions could be suppressed by the addition of ethylenediamine-N,N,N′,N′-tetrakis(methylenephosphonic acid) as a masking agent. The proposed method was successfully applied to the determination of vanadium in water samples.     

A concise synthesis of asymmetrical N,N′-disubstituted guanidines

We present a new and concise method for the preparation of asymmetrical N,N′-disubstituted guanidines starting from thiourea via the reaction of N-Boc-protected N′-alkyl/aryl substituted thioureas with an amine in the presence of mercury(II) chloride and triethylamine.     

Synthesis and characterization of a tetraruthenium butterfly cluster containing a quadruply-bridging ligand derived from an N,N′-dipyrid-2-ylurea

The tetraruthenium cluster complex [Ru₄(μ₄-κ⁴-dmpu)(CO)₁₀], H₂dmpu = N,N′-bis(6-methylpyrid-2-yl)urea, has been prepared by treating [Ru₃(CO)₁₂] with H₂dmpu in toluene at reflux temperature. An X-ray diffraction study has determined that this cluster has a butterfly metallic skeleton hold up by a doubly-deprotonated N,N′-bis(6-methylpyrid-2-yl)urea ligand (dmpu). This ligand has the pyridine N atoms attached to the wing-tip Ru atoms and the amido N atoms spanning Ru-Ru wing-edges, in such a way that the cluster has C₂ symmetry. The donor atoms of doubly-deprotonated N,N′-dipyrid-2-ylureas seem to be appropriately arranged to hold butterfly tetranuclear clusters.     

Chiral N,N′-dioxide-iron(II) complexes catalyzed enantioselective oxa-Michael addition of α,β-unsaturated aldehydes

The enantioselective oxa-Michael addition reaction of 1-(4-methoxyphenyl) ethanone oxime to various α,β-unsaturated aldehydes was accomplished by using chiral N,N′-dioxide-FeSO₄·7H₂O (1:1) complex. Aromatic acid was employed as additive to increase the yield of the reaction. The corresponding adducts were obtained in moderate yields with up to 76% ee under mild conditions.     

Synthesis of new fluorescent 2-(2′,2″-bithienyl)-1,3-benzothiazoles

Bithienyl-1,3-benzothiazole derivatives were synthesised by reacting various 5-formyl-5′-alkoxy- or 5-formyl-5′-N,N-dialkylamino-2,2′-bithiophenes with ortho-aminobenzenethiol in good to excellent yields. Evaluation of the fluorescence properties of these compounds was carried out. They show strong fluorescence in the 450-600 nm region, as well as high quantum yields and large Stokes’ shifts.     

Free-radical crosslinking copolymerization of acrylamide and N,N-methylenebis acrylamide by used Ce(IV)/polyethylene glycol and Ce(IV)/diethylmalonate redox initiator systems

Acrylamide and N,N^′-methylenebis (acrylamide) (AAm-Bis) copolymerization has been investigated in water at a total monomer concentration of the 0.5 M. Conversion of monomer was measured as a function of the reaction time up to the onset of macrogelation. Experimental results indicate that the critical conversion at the gel point shows a minimum at 6 mol.% Bis when the monomer concentration was kept constant at 0.5 M and it was found that polymer formed with different Bis% are not dissolved in water, acetic acid, toluene or chloroform.     

A convenient, large-scale synthesis of 4′-carboxamido N-Boc-2′,6′-dimethyl-l-phenylalanines

A large-scale synthesis of a series of 4′-carboxamido N-Boc-2′,6′-dimethyl-l-phenylalanines is described. This method features mild reaction conditions and high chemical yields from commercially available N-Boc-2′,6′-dimethyl-l-tyrosine methyl ester.     

Influence of N,N,N′,N′-tetraalkyl terephthalamide on isothermal crystallization kinetics and morphology evolution of polypropylene

The influence of N,N,N′,N′-tetraalkyl terephthalamide (TATA) on the isothermal crystallization kinetics of polypropylene (PP) was studied using differential scanning calorimetry (DSC). It was found that TATA shows a heterogeneous nucleation effect and leads to the formation of β-PP. TATA can not only shorten the crystallization time but also heighten the crystallization temperature of PP. The crystallization rate constant of PP containing TATA is larger than that of pure PP. The evolution of crystalline morphology of PP was investigated on a polarized optical microscopy (POM) equipped with a hot stage and the results showed that the introduction of TATA into PP can quicken the crystallization of PP, which is consistent with DSC results. TATA also leads to a substantial decrease in the spherulite size of PP and the boundaries of spherulites are hardly distinguished.     

Chemical and electrochemical procedures for the synthesis of diisopropyltetrahydroquinoxalinedione derivatives

Diisopropyltetrahydroquinoxalinedione derivatives are synthesized from the reaction of various catechols with N,N′-diisopropylethylenediamine. Both chemical and electrochemical methods give the same products. While the chemical synthesis is faster, the electrochemical synthesis provides higher yields.     

DFT study of the reaction sites of N,N′-substituted p-phenylenediamine antioxidants

The geometry of N,N′-diphenyl-p-phenylenediamine (DPPD), N-phenyl-N′-(1′-methylbenzyl)-p-phenylenediamine (SPPD), N-phenyl-N′-(1,3-dimethyl-butyl)-p-phenylenediamine (6PPD), N-phenyl-N′-isopropyl-p-phenylenediamine (IPPD), and N-(1-methyl-1-phenylethyl)-N′-phenyl-p-phenylenediamine (CPPD) as well as of their dehydrogenation products has been optimized at B3LYP/6-31G^∗ level of theory. Our results support the idea of formation of stable ketimine Ph-NC structures (instead of quinonediimine structures) during consecutive dehydrogenation of SPPD, 6PPD, and IPPD antioxidants despite the formation of tertiary carbon-centered radicals in the first dehydrogenation step is energetically preferred for SPPD only.     

Synthesis of fluorinated imines and carbodiimides from azides via aza-Wittig reaction

The Staudinger reaction of fluoroalkylazides were studied. A series of N-fluoroalkylimines were synthesized via aza-Wittig reaction of N-fluoroalkyliminophosphoranes. The N,N′-difluoroalkylated carbodiimide was also synthesized via the reaction of N-fluoroalkyliminophosphoranes with carbon dioxide or carbon disulfide.     

Dibutylphosphate (DBP) mediated synthesis of cyclic N,N′-disubstituted urea derivatives from amino esters: a comparative study

The N,N′-disubstituted urea derivatives such as amino acid hydantoins and dihydrouracil derivatives were prepared starting from natural and unnatural amino acid esters using dibutylphosphate (DBP). During the attempted synthesis of N-heterocycles with larger than six-membered rings containing the N,N′-disubstituted urea functionalities, three unexpected products namely squamolone, N-methyl pyrrolidine-2-one, and diketopiperazine were isolated.     

Oxidative hydrolysis of a cyclic 1,N-propano-2′-deoxyguanosine, an adduct of 2′-deoxyguanosine with acetaldehyde or crotonaldehyde

The SO₄⁻-oxidation of cyclic 1,N²-propano-2′-deoxyguanosine, chemo- and regioselectively produced in the reaction of 2′-deoxyguanosine with excessive acetaldehyde or crotonaldehyde, resulted in the smooth formation of (4-hydroxy-5-hydroxymethyltetrahydrofuran-2-ylimino)-(4-hydroxy-6-methyltetrahydropyrimidin-2-ylideneamino)acetic acid, 3-(4-hydroxy-5-hydroxymethyltetrahydrofuran-2-yl)-6-methyl-3H-1,3,4,5,8a-pentaazacyclopenta[b]naphthalen-9-one, and 2′-deoxyguanosine even under neutral conditions. The formation of the guanine-ring opened product during the reaction is very interesting and appears to closely relate to the mechanisms for the point-mutations of DNA by these mutagenic and carcinogenic aldehydes.     

Synthesis of 8-R-9c-alkyl-1-aryl-2-benzyl-1-hydroxy-1,2,9b,9c-tetrahydro-5-oxa-2-aza-cyclopenta[2,3]cyclopropa[1,2-a]naphthalene-3,4-diones and reaction thereof with acetic anhydride

The reaction of zinc enolates synthesized from 1-aryl-2,2-dibromoalkanones and zinc with 6-R-2-oxochromene-3-carboxylic acid N-benzylamide affords 8-R-9c-alkyl-1-aryl-2-benzyl-1-hydroxy-1,2,9b,9c-tetrahydro-5-oxa-2-aza-cyclopenta[2,3]cyclopropa[1,2-a]naphthalene-3,4-diones. Acylation of these compounds is accompanied by an unexpected rearrangement producing a sole geometrical isomer of 4′-alkyl-5′-aryl-1′-benzyl-3,4,2′,3′-tetrahydro-2,2′-dioxospiro[chroman-3,3′-pyrrol]-4-yl acetates.