Bulky Diamine Research Articles

Intrinsically Microporous Polyimides Derived from 2,2'-Dibromo-4,4',5,5'-bipohenyltetracarboxylic Dianhydride for Gas Separation Membranes.

This work aims to expand the structure-property relationships of bromo-containing polyimides and the influence of bromine atoms on the gas separation properties of such materials. A series of intrinsically microporous polyimides were synthesized from 2,2'-dibromo-4,4',5,5'-bipohenyltetracarboxylic dianhydride (Br-BPDA) and five bulky diamines, (7,7'-(mesitylmethylene)bis(8-methyldibenzo[b,e][1,4]dioxin-2-amine) (MMBMA), 7,7'-(Mesitylmethylene)bis(1,8-dimethyldibenzo[b,e][1,4] dioxin-2-amine) (MMBDA), 4,10-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-2,8-diamine (TBDA1), 4,10-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-3,9-diamine (TBDA2), and (9R,10R)-9,10-dihydro-9,10-[1,2]benzenoanthracene-2,6-diamine (DAT). The Br-BPDA-derived polyimides exhibited excellent solubility, high thermal stability, and good mechanical properties, with their tensile strength and modulus being 59.2-109.3 MPa and 1.8-2.2 GPa, respectively. The fractional free volumes (FFVs) and surface areas (SBET) of the Br-BPDA-derived polyimides were in the range of 0.169-0.216 and 211-342 m2 g-1, following the order of MMBDA > MMBMA > TBDA2 > DAT > TBDA1, wherein the Br-BPDA-MMBDA exhibited the highest SBET and FFV and thus highest CO2 permeability of 724.5 Barrer. Moreover, Br-BPDA-DAT displayed the best gas separation performance, with CO2, H2, O2, N2, and CH4 permeabilities of 349.8, 384.4, 69.8, 16.3, and 19.7 Barrer, and H2/N2 selectivity of 21.4. This can be ascribed to the ultra-micropores (<0.7 nm) caused by the high rigidity of Br-BPDA-DAT. In addition, all the bromo-containing polymers of intrinsic microporosity membranes exhibited excellent resistance to physical ageing.

Synthesis and magnetic characterization of a dinuclear complex of low-coordinate iron(II)

Low-coordinate ions possess exciting magnetic, optical, and reactive properties that may afford novel material physics. Hence, it is important to test both synthetic methods for realizing extended solids of such ions as well as the properties of smaller molecular fragments of envisioned future materials. Herein, we report the synthesis and characterization of a new dinuclear Fe species, [{(Me3Si2)2N}Fe{μ-p-{HN(SiMe3)}(C6Me4){N(SiMe3)}}2Fe{N(SiMe3)2}] (1), formed through a transamination reaction between [Fe{N(SiMe3)2}2]2 and the bulky diamine p-{HN(SiMe3)}2(C6Me4) (L). The Fe centers of this dimer assume a pseudo-trigonal-planar, three-coordinate conformation in 1, bridged by two aromatic diamines. Single-crystal X-ray diffraction, IR spectroscopy, and Mössbauer spectroscopy enable the assignment of both Fe centers as the 2+ oxidation state. Magnetic studies show that 1 displays a weak antiferromagnetic exchange interaction (J = −2.33 cm−1) and moderate zero-field splitting (D = 7.51 cm−1). Importantly, these studies demonstrate the viability of using transamination to bridge high-spin low-coordinate metal ions and hence the technique may, in the future, produce new extended structures.

Investigation of the Deprotonative Generation and Borylation of Diamine-Ligated α-Lithiated Carbamates and Benzoates by in Situ IR spectroscopy.

Diamine-mediated α-deprotonation of O-alkyl carbamates or benzoates with alkyllithium reagents, trapping of the carbanion with organoboron compounds, and 1,2-metalate rearrangement of the resulting boronate complex are the primary steps by which organoboron compounds can be stereoselectively homologated. Although the final step can be easily monitored by 11B NMR spectroscopy, the first two steps, which are typically carried out at cryogenic temperatures, are less well understood owing to the requirement for specialized analytical techniques. Investigation of these steps by in situ IR spectroscopy has provided invaluable data for optimizing the homologation reactions of organoboron compounds. Although the deprotonation of benzoates in noncoordinating solvents is faster than that in ethereal solvents, the deprotonation of carbamates shows the opposite trend, a difference that has its origin in the propensity of carbamates to form inactive parasitic complexes with the diamine-ligated alkyllithium reagent. Borylation of bulky diamine-ligated lithiated species in toluene is extremely slow, owing to the requirement for initial complexation of the oxygen atoms of the diol ligand on boron with the lithium ion prior to boron-lithium exchange. However, ethereal solvent, or very small amounts of THF, facilitate precomplexation through initial displacement of the bulky diamines coordinated to the lithium ion. Comparison of the carbonyl stretching frequencies of boronates derived from pinacol boronic esters with those derived from trialkylboranes suggests that the displaced lithium ion is residing on the pinacol oxygen atoms and the benzoate/carbamate carbonyl group, respectively, explaining, at least in part, the faster 1,2-metalate rearrangements of boronates derived from the trialkylboranes.

Bulky Diamine Ligand Promotes Cross‐Coupling of Difluoroalkyl Bromides by Iron Catalysis

AbstractAlthough iron‐catalyzed cross‐coupling of Grignard reagents with alkyl halides has been well established, the adoption of the reaction for fluoroalkylations has not been reported because traditional catalytic systems often lead to defluorination reactions. Described herein is the investigation of an iron‐catalyzed cross‐coupling between arylmagnesium bromides and difluoroalkyl bromides with modified N,N,N′,N′‐tetramethyl‐ethane‐1,2‐diamine (TMEDA) as a ligand. The use of this bulky diamine, in which a butylene is substituted at one carbon atom of the ethylene backbone in TMEDA, enables the iron‐catalyzed difluoroalkylation under mild reaction conditions with a wide range of difluoroalkyl bromides, including vulnerable bromodifluoromethane, thus providing a general and cost‐efficient route for applications in medicinal chemistry.

Bulky Diamine Ligand Promotes Cross-Coupling of Difluoroalkyl Bromides by Iron Catalysis.

Although iron-catalyzed cross-coupling of Grignard reagents with alkyl halides has been well established, the adoption of the reaction for fluoroalkylations has not been reported because traditional catalytic systems often lead to defluorination reactions. Described herein is the investigation of an iron-catalyzed cross-coupling between arylmagnesium bromides and difluoroalkyl bromides with modified N,N,N',N'-tetramethyl-ethane-1,2-diamine (TMEDA) as a ligand. The use of this bulky diamine, in which a butylene is substituted at one carbon atom of the ethylene backbone in TMEDA, enables the iron-catalyzed difluoroalkylation under mild reaction conditions with a wide range of difluoroalkyl bromides, including vulnerable bromodifluoromethane, thus providing a general and cost-efficient route for applications in medicinal chemistry.

Synthesis of Piperidines via Intramolecular Hydride Transfer from α‐Amino sp3 Carbon Atoms to Ethenetricarboxylate‐Derived Fragments and Further Cyclization

AbstractThe cyclization of amides derived from ethenetricarboxylic acid bearing tert‐amino groups has been examined. The amides were efficiently converted to piperidine derivatives (2‐piperidones) upon heating in a polar solvent (e. g., DMSO or DMF) via intramolecular hydride transfer and subsequent ring closure. The reaction was less efficient in the presence of a Lewis acid. The reactivity varies depending on the alkyl substituents of tert‐amino groups, probably due to steric effects. The hydride transfer/cyclization mechanism was investigated by DFT calculations. The reaction of the carboxylic acid and relatively bulky diamines such as diisopropyl‐substituted diamine in the presence of amide condensation reagents at 60 °C gave the piperidine derivatives in a one‐pot reaction. The reaction of the diisopropylamine substituted piperidine product with primary amines gave secondary amine‐substituted piperidines.

Studies on the Synthesis of Specifically Fluorinated 4‐Amino‐ pyridine Derivatives by Regioselective Nucleophilic Aromatic Substitution and Catalytic Hydrodefluorination

AbstractThe reactions of pentafluoropyridine and 2,4,6‐trifluoropyridine with a series of primary and secondary amines were studied. Whereas the nucleophilic aromatic substitution of pentafluoropyridine occurs with high regioselectivity in all cases, providing the expected 4‐aminopyridine derivatives in excellent yields, the regioselectivity of 2,4,6‐trifluoropyridine is dependent on the steric hindrance of the attacking nucleophile. Small nucleophiles such as morpholine attack the 4‐position of the pyridine ring with high preference, but more bulky diamines attack the 2‐ and 4‐positions leading to the formation of three regioisomeric products. (R,R)‐1,2‐Diaminocyclohexane as moderately bulky diamine reacted with 2,4,6‐trifluoropyridine to afford the desired bis(4‐aminopyridinyl)cyclohexane derivative in 30% yield. For hydrodefluorination two methods were examined. A two‐step procedure employing hydrazine and subsequently copper(II) sulfate removed just one fluorine substituent, but is not sufficiently high yielding for the reduction of more complex substrates. With the system titanocene difluoride as pre‐catalyst and diphenylsilane as reducing agent we were able to selectively remove fluorine substituents at positions C‐2 and C‐4 of a variety of 4‐aminopyridine derivatives. This protocol allows the synthesis of compounds such as the divalent chiral 4‐(dimethylamino)pyridine (DMAP) analogue (R,R)‐trans‐N,N′‐dimethyl‐N,N′‐bis(pyridin‐4‐yl)cyclohexane‐1,2‐diamine with fair overall yield.magnified image

Effects of amine ligand bulk and hydrogen bonding on the rate of reaction of platinum(II) diamine complexes with key nucleotide and amino acid residues

NMR spectroscopy has been used to observe the effects of the amine ligand on the rate of reaction of platinum diamine and triamine complexes with DNA and protein residues. Whereas [Pt(dien)Cl]Cl and [Pt(dien)(D2O)]2+ have been known to react faster with thioether residues such as N-AcMet than with 5′-GMP, we found that [Pt(Me4en)(D2O)2]2+ appeared to react faster with 5′-GMP. To quantitatively assess the factors influencing the rates of reaction, rate constants at pH 4 were determined for the reactions of [Pt(en)(D2O)2]2+ [en=ethylenediamine] and [Pt(Me4en)(D2O)2]2+ with N-AcMet, N-AcHis, 5′-GMP, and Guo (guanosine). In general the less bulky complex ([Pt(en)(D2O)2]2+) reacts more quickly than does the bulkier [Pt(Me4en)(D2O)2]2+, as expected. Both complexes reacted faster with 5′-GMP; however, analysis of the rate constants suggests that the [Pt(en)(D2O)2]2+ complex favors reaction with 5′-GMP due to hydrogen bonding with the 5′-phosphate, whereas [Pt(Me4en)(D2O)2]2+ disfavors reaction with N-AcMet due to steric clashes. Bulk had relatively little effect on the rate constant with N-AcHis, suggesting that peptides or proteins that coordinate via His residues would not have their reactivity affected by bulky diamine ligands.

Design of gas separation membranes derived of rigid aromatic polyimides. 1. Polymers from diamines containing di- tert-butyl side groups

A series of polyimides has been obtained from the experimental diamine 1,4-bis(4-aminophenoxy)2,5-di- tert-butylbenzene (TBAPB) and three commercial dianhydrides, i.e. pyromellitic dianhydride (PMDA), 3,3′,4,4′-byphenyltetracarboxylic dyanhidride (BPDA) and 4,4′-hexafluoroisopropyliden diphthalic anhydride (6FDA), following classical polyimidation methods. Analogous polyimides with diamines 2,2-bis(4-aminophenyl)hexafluoropropane (6FpDA) and 1,4-bis(4-aminophenoxy)benzene (APB) have been also prepared for comparative purposes. All polyimides showed high thermal stability, with decomposition temperatures above 490 °C, and glass transition temperatures higher than 270 °C. The rigid, rod-like structure of PMDA, combined with bulky diamines TBAPB and 6FpDA, yielded polyimides with high fractional free volume (FFV), close to that of 6FDA–6FpDA. The high FFV of PMDA–TBAPB contrasts with its structure that has fairly large degree of short range order as evidenced by X-ray diffraction. The gas permeation properties were greatly dependent on the dianhydride moiety and, as a rule, they compared well with those of polyimides used for gas separation. The polymers from PMDA, PMDA–TBAPB and PMDA–6FpDA, showed the best gas productivity values. By means of molecular modelling calculations, it has been observed that monomer TBAPB preferably adopts a contorted, rotation-restricted conformation, what can explain the special characteristics observed in the reported polyimides.

Structure-Property Relationships of Soluble Poly(ester-urea)s containing Naphthyl Groups

The preparation of new types of polyureas with good thermal properties and improved solubility was investigated. Two new bulky diamines as new monomers for the preparation of polyurea were synthesized via two steps. First, a nucleophilic reaction of 1-naphthol and 2-naphthol with 3,5-dinitrobenzoyl chloride and then the reduction of the nitro groups by hydrazine hydrate/Pd-C to produce the corresponding diamines (1NA and 2NA). The poly(ester-urea)s were synthesized through the polyaddition reaction of the diamines with various commercially available diisocyanates. The polymers were characterized using IR and 1H NMR spectroscopy, elemental analysis, viscometry, thermal analysis, gel permeation chromatography (GPC), and X-ray diffraction. The copolymers were amorphous and readily soluble in a wide range of organic solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethyl sulfoxide, N, N-dimethylformamide, and m-cresol. Thermal analysis showed a glass transition temperature between 146 and 178 °C. Their decomposition temperatures were more than 180 °C, and their 10% weight losses were in the range 281—315 ° C in air. The weight average molecular weights ( Mw) of the polymers were about 32 200—40 500 g/mol.

Effect of amine ligand bulk on the interaction of methionine with platinum(II) diamine complexes.

Molecular mechanics and dynamics calculations have been used in conjunction with experimental data to study the effects of amine ligand bulk on the formation of both guanine and methionine complexes with platinum diamine compounds. The AMBER force field has been supplemented with previous modifications [Yao; et al. Inorg. Chem. 1994, 33, 6061-6077. Cerasino; et al. Inorg. Chem. 1997, 36, 6070-6079] and has been further modified to include parameters for platinum bound to the sulfur atom of methionine. Molecular mechanics calculations with this modified AMBER force field have suggested that a platinum complex with two sulfur-bound methionine ligands and a bulky diamine ligand (N,N,N',N'-tetramethylethylenediamine, Me(4)en) would have severe interligand clashes; such interligand clashes are less pronounced in bis(9-ethylguanine) complexes. Consistent with these observations, NMR studies with [Pt(Me(4)en)(D(2)O)(2)](2+) have indicated that guanine 5'-monophosphate reacts in a 2:1 guanine:platinum ratio while both methionine and N-acetylmethionine react with only a 1:1 stoichiometry. Methionine forms a chelate via the sulfur and nitrogen atoms whereas N-acetylmethionine forms a chelate via the sulfur and oxygen atoms. The oxygen of the latter chelate can be displaced by the addition of guanosine 5'-monophosphate, although complete displacement of the N-acetylmethionine was not observed.

Synthesis and Characterization of Some Mixed Ligand-Selenito and Tellurito Chromium(III) Complexes

New mixed ligand Cr(III) complexes were prepared where diamine or oxalato ligands are coordinated together with either tellurito, selenito, or hydrogenselenito ions to form nine octahedral complexes. The complexes were characterized by chemical analyses, IR and UV-visible spectra, magnetic, and conductivity measurements. The tellurito and selenito ligands act as monodentate ligands, coupled with the bidentate diamine ligands. On the other hand, they act as bidentate chelate ligands when coordinated together with the oxalate ligand. However, hydrogenselenite ion act as a monodentate ligand coupled with the oxalate ligand. IR spectra indicated that the inorganic ligands are coordinated to the Cr(III) ion through their oxygen atoms. One of the bulky diamine molecules, 1,2-pn or 1,3-pn, was freed from the coordination sphere of Cr(III) on the addition of the bulky inorganic anions and was replaced by two water molecules.

Cationic 16-electron half-sandwich ruthenium complexes containing asymmetric diamines: understanding the stability and reactivity of coordinatively unsaturated two-legged piano stool complexes

The cationic 16e complexes [RuCp*(η 2(N,N)-Me 2NCH 2CH 2N(CH 2CHMe 2) 2)] + ( 1) and [RuCp*(η 2(N,N)-Me 2NCH 2CH 2 NCH 2CH 2OCH 2C H 2] + ( 2) as well as the 18e complex [RuCp*(η 6-C 6H 5-N(Me)NCH 2CH 2NMe 2)] + ( 3) have been synthesized as the BAr′ 4 (Ar′=3,5-C 6H 3(CF 3) 2) salts in one-pot reactions starting from [RuCp*(Cl)] 4. For 1, the X-ray crystal structure has also been determined showing the absence of any agostic interactions between ruthenium and the C–H bonds of the diamine ligand, and only minor deviations from the planar geometry despite the bulky diamine ligand. Based on EH model calculations, the extraordinary kinetic inertness of the planar 16e [Cp*Ru(NN)] + structure is traced to a high HOMO–LUMO gap deriving from through-bond coupling through the intervening σ skeleton of the chelating diamine (NN) ligand (in contrast to the P analogs) and further to the high π donor strength of Cp* (relative to parent Cp). Possible ligand rearrangements to increase the chemical reactivity are analyzed.

Axial chirality induction in flexible biphenols by hydrogen bonding and steric interactions

Chiral induction in biphenols was studied as a model for intermolecular information transmission. Upon complexation with chiral trans-1,2-cyclohexanediamines (C 6H 10(NHR) 2, R = H, CH 3, CH 2CH 2Bu t ), axial chirality was induced in biphenols in toluene, CHCl 3 and THF. The induced chirality varies as the alkyl groups on the amino groups vary from H, CH 3 to CH 2CH 2Bu t . The bulky diamine (R = CH 2CH 2Bu t ) induced the opposite chirality to that induced by the less bulky diamine (R = CH 3, H.

Synthesis and characterization of new polyamides and polyimides derived from (E)‐9‐[β‐(2,4‐diaminophenyl)vinyl]anthracene

AbstractA new anthracene‐containing diamine, (E)‐9‐[β‐(2,4‐diaminophenyl)vinyl]anthracene, was prepared and used for the synthesis of a series of polyamides and polyimides by low temperature solution polycondensation. The polymers were highly amorphous, soluble in aprotic solvents and gave films with good optical quality on spin‐casting. The polymers showed 10% weight loss at a temperature of 415–460°C under nitrogen. The polymers exhibited an intense luminescence in the region of 450–500 nm due the emission from the excited state of the diamine moiety. It was shown that charge‐transfer (CT) interactions in polyimides were negligibly small in both the ground and the excited state, probably due to the bulky diamine fragment together with the rigid polymer backbone.

Synthesis and Crystal Structure of Organocobalt(III) Complexes with Secondary Alkyls or Bulky Schiff Base Equatorial Ligands

Alkylcobalt(III) Schiff base B(12) model complexes with secondary alkyls or a bulky diamine in the equatorial position were synthesized and characterized. Structures have been first determined by X-ray diffraction analysis for i-C(4)H(9)Co(salen)(gamma-pic) (I), n-C(3)H(7)Co(salen)(gamma-pic) (II) and C(2)H(5)Co(SB) (III), where salen = N,N'-ethylenebis(salicylideneamine) dianion; SB = 1,1,2,2-tetramethyl-N,N'-ethylenebis(salicylideneamine) dianion, gamma-pic = gamma-picoline. Crystal data for I (CoC(26)N(3)O(2)H(30)): space group P2(1)/c with a = 6.661(5) Å, b = 18.612(2) Å, c = 19.533(3) Å, beta = 98.93(1) degrees, V = 2392.10 Å(3), D(calcd) = 1.320 g.cm(-3), Z = 4, and R = 0.048 for 4469 measured reflections. Crystal data for II (CoC(25)N(3)O(2)H(28)): space group P2(1)/c, a = 9.609(6) Å, b = 19.169(8) Å, c = 12.995(9) Å, beta = 106.9(7) degrees, V = 2290.4 Å(3), D(calcd) = 1.332 g.cm(-1), Z = 4, and R = 0.048 for 4358 measured reflections. Crystal data for III (CoC(22)N(2)O(2)H(27)): space group P2(1)/c, a = 8.318(3) Å, b = 21.579(2) Å, c = 11.572(2) Å, beta = 93.35(1) degrees, V = 2073.7 Å(3), D(calcd) = 1.314 g.cm(-1), Z = 4, and R = 0.060 for 3954 measured reflections. The crystal structure data reveal that complexes I and II display six-coordinate octahedral geometry; their Co-C, Co-N bond lengths, as well as the Co-C-C angles, are very close to those in 5'-deoxyadenosylcobalamin. Complex III is one of the very few compounds having five-coordinate square pyramidal geometry and observed instability of the Co-C bond.

Macro‐cyclic aramids (2n‐AZA[2n]paracyclophane‐2n‐ones):new intermediates for the synthesis of p‐aramids

AbstractAn easy route to a new class of n‐azapara[2n] cyclophane‐n‐ones, N‐substituted p‐oriented cyclic aromatic amide (cycloaramid) oligomers, is described. The bulky diamine, N, N′‐di‐sec‐butyl‐p‐phenylenediamine is condensed with terephthaloyl dichloride at elevated temperature in o‐dichlorobenzene to provide a high yield of N, N′‐di‐sec‐butyl‐p‐phenyleneterephthalamide cyclic oligomers (from dimer to tridecamer). The cyclization is favored by the cis conformation of the N‐substituted amide bonds present in the growing chain. Ring opening polymerization of these new cycloaramids to high molecular weight linear polymers can be effected in the melt phase with highly nucleophilic catalysts, such as 1,3‐dialkylimidazole‐2‐thiones especially when an acid cocatalyst is employed. The N‐substituted polymers yield crystalline films and fibers with an axial repeat length which can only be explained by an unexpected trans conformation of the amide bonds. The facile synthesis of other macrocyclic amides by the steric control of macrocyclization by N‐substitution of the amide bond is also described.

Macrocyclic aramides (2n-aza[2n]paracyclophane-2n-ones): new intermediates for the synthesis of p-aramids

An easy route to a new class of 2n-aza[2 n ]paracyclophane-2n-ones,N-substituted para-oriented cyclic aromatic amide (cycloaramid) oligomers, is described. The bulky diamine N,N'-di-sec-butyl-p-phenylenediamine is condensed with terephthaloyl chloride at elevated temperature in o-dichlorobenzene to provide a high yield of N,N'-di-sec-butyl-p-phenyleneterephalamide cyclic oligomers (from dimer to tridecamer). Ring opening polymerization of these new cycloaramides to high molecular weight linear polymers can be effected in the melt phase with highly nucleophilic catalysts.

Unusual stereoselection in the reaction of dianions derived from 1-phenylsulphonylalkan-2-ols with electrophilic reagents

The stereochemistry in the reaction of dianions of 1-phenylsulphonylalkan-2-ols (1) with electrophilic reagents such as alkyl halides and aldehydes is discussed. The reaction takes place regioselectively at the α-position to the sulphonyl group to form a new chiral centre. In tetrahydrofuran the sterically more crowded erythro-isomer is obtained as the major product in a good diastereoisomeric ratio (50–100% d.e.). Additives such as HMPA and bulky diamines greatly influence the stereoselectivity of the reaction. The co-ordination of tetrahydrofuran molecules with a metal cation is considered to play an important role in the reaction.