ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
In this review, an overview of synthetic and structural aspects of 1-azabuta-1,3-diene complexes ... more In this review, an overview of synthetic and structural aspects of 1-azabuta-1,3-diene complexes of iron is given and the reactivity of these complexes is discussed with regard to inorganic, organometallic, organic and stereochemical aspects of their chemistry. Their application in the synthesis of organic and organometallic target compounds, or as transfer reagents of the tricarbonlyiron(0) moiety is demonstrated.
Reaction of (1-azabuta-1,3-diene)tricarbonyliron(0) complexes with sodium borohydride under micro... more Reaction of (1-azabuta-1,3-diene)tricarbonyliron(0) complexes with sodium borohydride under microwave irradiation leads to formation of saturated secondary amines. When sodium borodeuteride is used for the reaction the products are 1,2,3-trideutero secondary amines. When this reaction is performed under thermal conditions the complexes are inert to reduction by sodium borohydride.
The interfacial and nonaqueous solution properties of model engine oil antisludge dispersants hav... more The interfacial and nonaqueous solution properties of model engine oil antisludge dispersants have been characterized. Straight chain C8-C18 mono, bis, and tris succinimides were synthesized with polar headgroups of different dimensions and varying nitrogen content. These molecules were found to be poorly soluble in water, as confirmed by log P calculations (P is the partition function between octan-1-ol and water.) Vapor pressure osmometry measurements carried out in acetone and toluene revealed that the mono succinimides show evidence of association into clusters of about three molecules with no noticeable chain length dependence, whereas the bis and tris compounds are essentially unassociated in these solvents. Surface pressure vs area curves from a Langmuir trough exhibit a characteristic plateau at low surface coverage, especially for short chain lengths and mono-substituted succinimides. This feature we attribute to a more compact packing of the headgroups under pressure. For the same lateral pressure the area occupied increases in the order: mono, bis, and tris, correlating well with the number of succinimide moieties in the headgroup. Ellipsometry performed on these molecules deposited on silicon wafers showed that the molecules generally formed excellent close-packed Langmuir-Blodgett films. The succinimides are extremely effective at binding to polar substrates, which is consistent with their practical use. For example, solutions of the various compounds deposited on TLC plates generally showed little movement, and there was the maximum amount of separation in those cases where the solvent had a natural affinity for the headgroup or tail.
ABSTRACT Reaction of (ergosterol acetate)tricarbonyliron(0) (1) with lithium aluminiumhydride lea... more ABSTRACT Reaction of (ergosterol acetate)tricarbonyliron(0) (1) with lithium aluminiumhydride leads to the selective reduction of the 5,6 double bond. The A/B ring junction of the reduction product has been shown to be trans on the basis of 13C NMR. This information has been used to confirm that the initial addition of hydride to the coordinated ergosterol acetate occurs on the α-face at C-5.
ABSTRACT Reaction of (2-ethyl-1,4-diphenyl-1-azabuta-1,3-diene)tricarbonyliron(0) 4 and (2-ethyl-... more ABSTRACT Reaction of (2-ethyl-1,4-diphenyl-1-azabuta-1,3-diene)tricarbonyliron(0) 4 and (2-ethyl-1-benzyl-4-phenyl-1-azabuta-1,3-diene)tricarbonyliron(0) 7 with lithium diethylamide leads to selective formation of the corresponding endo (1-methyl-2-amino buta-1,3-diene)tricarbonyliron(0) complexes 5 and 8, respectively. In each case there is no evidence for the exo complexes 6 and 9.
ABSTRACT Treatment of (2-methyl-1-azabuta-1,3-diene)tricarbonyliron(0) complexes with lithium die... more ABSTRACT Treatment of (2-methyl-1-azabuta-1,3-diene)tricarbonyliron(0) complexes with lithium diethylamide followed by a methyl iodide, benzyl bromide or allyl bromide quench leads to the formation of tertiary (enamine)tricarbonyliron(0) complexes in good yield. The crystal structures of two complexes, (2-(N-methyl-N-(4-methoxyphenyl)amino)-4-phenylbuta-1,3-diene)tricarbonyliron(0) (19) and (2-(N-allyl-N-isopropylamino)-4-phenylbuta-1,3-diene)tricarbonyliron(0) (24) are reported.
ABSTRACT Mild H2O2 oxidation of a small series of 2-cycloalkyl-3-hydroxynaphthoquinones catalyzed... more ABSTRACT Mild H2O2 oxidation of a small series of 2-cycloalkyl-3-hydroxynaphthoquinones catalyzed by 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphineiron(III) chloride in methanol−dichloromethane leads in each case to the isolation of a dehydro-dimer identified as a 3-cycloalkyl-3-(2-cycloalkylnaphthoquinon-3-yl)oxy-2-oxo-2,3-dihydronaphtho-1,4-quinone and in some cases to a 2-cycloalkyl-2,3-dihydroxy-1-oxoindan-3-carboxylate. The mechanism of formation of the former is rationalized in terms of nucleophilic attack of unreacted hydroxynaphthoquinone anion upon an epoxide primary oxidation product, while that of the latter is proposed to involve nucleophilic attack of solvent methanol on the same epoxide followed by rearrangement.
The ability of certain Fe and Mn metalloporphyrins to catalyse the H 2 O 2 epoxidation of cyclooc... more The ability of certain Fe and Mn metalloporphyrins to catalyse the H 2 O 2 epoxidation of cyclooctene is analysed. The 'efficiency' of epoxidation is dissected into contributions due to inherent catalyst epoxidation ability, catalyst H 2 O 2 dismutation ability, and catalyst stability towards the oxidant. It is shown that catalyst stability is a major factor contributing to apparent catalyst ability. The preparation of a sol-gel encapsulated metalloporphyrin is reported and it is shown to exhibit reduced rate of epoxidation, but a much enhanced stability.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2007
13 C NMR and Langmuir trough measurements have been used to monitor physico-chemical changes taki... more 13 C NMR and Langmuir trough measurements have been used to monitor physico-chemical changes taking place during the carbonation of a calcium hydroxide in hexadecane suspension in the presence of calixarene and stearic acid as stabilizers. The initial reaction, before carbonation, is characterized by neutralization of the outer surface of the suspended calcium hydroxide particles by the surfactant species present. However, it is observed that after approximately 30% carbonation, particles close to the final size (ca. 6 nm diameter) are formed; these are then converted into calcium carbonate nano-particles without significant further change in size. It is therefore proposed that a fragmentation process is responsible for the rapid reduction in particle size. Inferences are made regarding the composition of the carbonate 'core' and the surfactant surface on the basis of the 13 C NMR results.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2003
A new mixed calixarate/stearate calcium carbonate overbased detergent has been prepared and chara... more A new mixed calixarate/stearate calcium carbonate overbased detergent has been prepared and characterised by 1 H NMR, 13 C NMR, IR, Raman and UV-Vis spectroscopic methods. In addition, Langmuir trough and dynamic light scattering experiments have been carried out. These are interpreted in terms of a calcium stearate-and calcium calixarate-stabilised CaCO 3 particle of ca. 6 nm diameter; there is evidence for a reservoir of excess surfactant inverse micelles.
The role played by surfactant molecular architecture in determining its effectiveness as a disper... more The role played by surfactant molecular architecture in determining its effectiveness as a dispersant for carbonaceous solid substrates in hydrocarbon solvents is investigated using simple analytic theory and adsorption experiments carried out with model and commercial succinimides on activated carbon. We show by both of these approaches that the length and backbone structure of the hydrophobic tail are significant factors in determining the efficiency of the adsorption process and therefore probably the dispersancy mechanism itself. All of the succinimides are shown to be 'high affinity' adsorbates.
Fe(CO),R'CH=CR2COR3 Compounds A major theme of contemporary chemistry is the development of new s... more Fe(CO),R'CH=CR2COR3 Compounds A major theme of contemporary chemistry is the development of new synthetic routes using organometallic compounds.' Recent work in this department has involved the investigation of the synthetic utility of compounds, 1, comprising an a$unsaturated carbonyl compound attached to the iron tricar-bony1 moiety.'
Alkaline anion-exchange radiation-grafted membranes for possible electrochemical application in f... more Alkaline anion-exchange radiation-grafted membranes for possible electrochemical application in fuel cells.
A rapid and easy route to formamides by microwave assisted N-formylation of primary and secondary... more A rapid and easy route to formamides by microwave assisted N-formylation of primary and secondary amines is described. Using an insoluble polymer or an inorganic solid-supported reagent as a formylating agent, microwave irradiation furnished the corresponding formamides in high yields, with reduced reaction time and solvent volume over the conventional approach.
ABSTRACT A number of quantum chemical and density functional methods have been used to study the ... more ABSTRACT A number of quantum chemical and density functional methods have been used to study the chemo- and regioselectivity of the uncatalysed and Lewis acid mediated cycloaddition of the nitrone PhCHN(Me)O with the CC or the CN bond of (E)-cinnamonitrile. In agreement with experimental evidence, Lewis acid coordination to the nitrile strongly promotes reaction at the CN bond over reaction at the alkene moiety. The main factors responsible for this inversion of the chemoselectivity were identified as the following: (i) the Lewis acid strongly stabilises the product of CN addition and the transition state leading to it, thus favouring this reaction both kinetically and thermodynamically. Addition across the CC bond, in contrast, only receives weak kinetic activation; (ii) the cycloaddition to the CC or CN bonds involves different molecular orbitals at the cinnamonitrile, and the Lewis acid influences the orbital involved in CN addition to a larger extent; (iii) the Lewis acid has a stronger effect on the electron distribution of the CN bond. As an overall result, the Lewis acid not only promotes the cycloaddition, but also alters the order of functional group reactivity and brings about a complete change in chemoselectivity.Graphical abstract
Camphor‐derived α‐dicarbonyl compounds and 3‐oxo‐camphorsulfonylimine have been synthesized from ... more Camphor‐derived α‐dicarbonyl compounds and 3‐oxo‐camphorsulfonylimine have been synthesized from the corresponding ketones or sulfonylimine by microwave‐assisted oxidation with selenium dioxide. Compared to the classical reaction conditions, good yields were obtained in much shorter reaction times. Additionally, the selenium precipitation is more quantitative, and its removal from the reaction mixture is easier.
Vinylbenzyl chloride was grafted onto PVDF and FEP polymer films using the radiation-grafting met... more Vinylbenzyl chloride was grafted onto PVDF and FEP polymer films using the radiation-grafting methodology. Subsequent reaction with trimethylamine and ion-exchange with potassium hydroxide yields alkaline anion-exchange membranes that are capable of conducting hydroxide ions; such membranes may be suitable for use in low temperature direct methanol fuel cells for portable devices. The PVDF based materials underwent an undesirable degradation and were found to be less suitable for this class of membrane. FEPbased materials exhibited superior structural stability, conductivities up to 0.02 S cm-1 at room temperature, and good retention of ionexchange capacities when treated in water at 60°C.
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
In this review, an overview of synthetic and structural aspects of 1-azabuta-1,3-diene complexes ... more In this review, an overview of synthetic and structural aspects of 1-azabuta-1,3-diene complexes of iron is given and the reactivity of these complexes is discussed with regard to inorganic, organometallic, organic and stereochemical aspects of their chemistry. Their application in the synthesis of organic and organometallic target compounds, or as transfer reagents of the tricarbonlyiron(0) moiety is demonstrated.
Reaction of (1-azabuta-1,3-diene)tricarbonyliron(0) complexes with sodium borohydride under micro... more Reaction of (1-azabuta-1,3-diene)tricarbonyliron(0) complexes with sodium borohydride under microwave irradiation leads to formation of saturated secondary amines. When sodium borodeuteride is used for the reaction the products are 1,2,3-trideutero secondary amines. When this reaction is performed under thermal conditions the complexes are inert to reduction by sodium borohydride.
The interfacial and nonaqueous solution properties of model engine oil antisludge dispersants hav... more The interfacial and nonaqueous solution properties of model engine oil antisludge dispersants have been characterized. Straight chain C8-C18 mono, bis, and tris succinimides were synthesized with polar headgroups of different dimensions and varying nitrogen content. These molecules were found to be poorly soluble in water, as confirmed by log P calculations (P is the partition function between octan-1-ol and water.) Vapor pressure osmometry measurements carried out in acetone and toluene revealed that the mono succinimides show evidence of association into clusters of about three molecules with no noticeable chain length dependence, whereas the bis and tris compounds are essentially unassociated in these solvents. Surface pressure vs area curves from a Langmuir trough exhibit a characteristic plateau at low surface coverage, especially for short chain lengths and mono-substituted succinimides. This feature we attribute to a more compact packing of the headgroups under pressure. For the same lateral pressure the area occupied increases in the order: mono, bis, and tris, correlating well with the number of succinimide moieties in the headgroup. Ellipsometry performed on these molecules deposited on silicon wafers showed that the molecules generally formed excellent close-packed Langmuir-Blodgett films. The succinimides are extremely effective at binding to polar substrates, which is consistent with their practical use. For example, solutions of the various compounds deposited on TLC plates generally showed little movement, and there was the maximum amount of separation in those cases where the solvent had a natural affinity for the headgroup or tail.
ABSTRACT Reaction of (ergosterol acetate)tricarbonyliron(0) (1) with lithium aluminiumhydride lea... more ABSTRACT Reaction of (ergosterol acetate)tricarbonyliron(0) (1) with lithium aluminiumhydride leads to the selective reduction of the 5,6 double bond. The A/B ring junction of the reduction product has been shown to be trans on the basis of 13C NMR. This information has been used to confirm that the initial addition of hydride to the coordinated ergosterol acetate occurs on the α-face at C-5.
ABSTRACT Reaction of (2-ethyl-1,4-diphenyl-1-azabuta-1,3-diene)tricarbonyliron(0) 4 and (2-ethyl-... more ABSTRACT Reaction of (2-ethyl-1,4-diphenyl-1-azabuta-1,3-diene)tricarbonyliron(0) 4 and (2-ethyl-1-benzyl-4-phenyl-1-azabuta-1,3-diene)tricarbonyliron(0) 7 with lithium diethylamide leads to selective formation of the corresponding endo (1-methyl-2-amino buta-1,3-diene)tricarbonyliron(0) complexes 5 and 8, respectively. In each case there is no evidence for the exo complexes 6 and 9.
ABSTRACT Treatment of (2-methyl-1-azabuta-1,3-diene)tricarbonyliron(0) complexes with lithium die... more ABSTRACT Treatment of (2-methyl-1-azabuta-1,3-diene)tricarbonyliron(0) complexes with lithium diethylamide followed by a methyl iodide, benzyl bromide or allyl bromide quench leads to the formation of tertiary (enamine)tricarbonyliron(0) complexes in good yield. The crystal structures of two complexes, (2-(N-methyl-N-(4-methoxyphenyl)amino)-4-phenylbuta-1,3-diene)tricarbonyliron(0) (19) and (2-(N-allyl-N-isopropylamino)-4-phenylbuta-1,3-diene)tricarbonyliron(0) (24) are reported.
ABSTRACT Mild H2O2 oxidation of a small series of 2-cycloalkyl-3-hydroxynaphthoquinones catalyzed... more ABSTRACT Mild H2O2 oxidation of a small series of 2-cycloalkyl-3-hydroxynaphthoquinones catalyzed by 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphineiron(III) chloride in methanol−dichloromethane leads in each case to the isolation of a dehydro-dimer identified as a 3-cycloalkyl-3-(2-cycloalkylnaphthoquinon-3-yl)oxy-2-oxo-2,3-dihydronaphtho-1,4-quinone and in some cases to a 2-cycloalkyl-2,3-dihydroxy-1-oxoindan-3-carboxylate. The mechanism of formation of the former is rationalized in terms of nucleophilic attack of unreacted hydroxynaphthoquinone anion upon an epoxide primary oxidation product, while that of the latter is proposed to involve nucleophilic attack of solvent methanol on the same epoxide followed by rearrangement.
The ability of certain Fe and Mn metalloporphyrins to catalyse the H 2 O 2 epoxidation of cyclooc... more The ability of certain Fe and Mn metalloporphyrins to catalyse the H 2 O 2 epoxidation of cyclooctene is analysed. The 'efficiency' of epoxidation is dissected into contributions due to inherent catalyst epoxidation ability, catalyst H 2 O 2 dismutation ability, and catalyst stability towards the oxidant. It is shown that catalyst stability is a major factor contributing to apparent catalyst ability. The preparation of a sol-gel encapsulated metalloporphyrin is reported and it is shown to exhibit reduced rate of epoxidation, but a much enhanced stability.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2007
13 C NMR and Langmuir trough measurements have been used to monitor physico-chemical changes taki... more 13 C NMR and Langmuir trough measurements have been used to monitor physico-chemical changes taking place during the carbonation of a calcium hydroxide in hexadecane suspension in the presence of calixarene and stearic acid as stabilizers. The initial reaction, before carbonation, is characterized by neutralization of the outer surface of the suspended calcium hydroxide particles by the surfactant species present. However, it is observed that after approximately 30% carbonation, particles close to the final size (ca. 6 nm diameter) are formed; these are then converted into calcium carbonate nano-particles without significant further change in size. It is therefore proposed that a fragmentation process is responsible for the rapid reduction in particle size. Inferences are made regarding the composition of the carbonate 'core' and the surfactant surface on the basis of the 13 C NMR results.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2003
A new mixed calixarate/stearate calcium carbonate overbased detergent has been prepared and chara... more A new mixed calixarate/stearate calcium carbonate overbased detergent has been prepared and characterised by 1 H NMR, 13 C NMR, IR, Raman and UV-Vis spectroscopic methods. In addition, Langmuir trough and dynamic light scattering experiments have been carried out. These are interpreted in terms of a calcium stearate-and calcium calixarate-stabilised CaCO 3 particle of ca. 6 nm diameter; there is evidence for a reservoir of excess surfactant inverse micelles.
The role played by surfactant molecular architecture in determining its effectiveness as a disper... more The role played by surfactant molecular architecture in determining its effectiveness as a dispersant for carbonaceous solid substrates in hydrocarbon solvents is investigated using simple analytic theory and adsorption experiments carried out with model and commercial succinimides on activated carbon. We show by both of these approaches that the length and backbone structure of the hydrophobic tail are significant factors in determining the efficiency of the adsorption process and therefore probably the dispersancy mechanism itself. All of the succinimides are shown to be 'high affinity' adsorbates.
Fe(CO),R'CH=CR2COR3 Compounds A major theme of contemporary chemistry is the development of new s... more Fe(CO),R'CH=CR2COR3 Compounds A major theme of contemporary chemistry is the development of new synthetic routes using organometallic compounds.' Recent work in this department has involved the investigation of the synthetic utility of compounds, 1, comprising an a$unsaturated carbonyl compound attached to the iron tricar-bony1 moiety.'
Alkaline anion-exchange radiation-grafted membranes for possible electrochemical application in f... more Alkaline anion-exchange radiation-grafted membranes for possible electrochemical application in fuel cells.
A rapid and easy route to formamides by microwave assisted N-formylation of primary and secondary... more A rapid and easy route to formamides by microwave assisted N-formylation of primary and secondary amines is described. Using an insoluble polymer or an inorganic solid-supported reagent as a formylating agent, microwave irradiation furnished the corresponding formamides in high yields, with reduced reaction time and solvent volume over the conventional approach.
ABSTRACT A number of quantum chemical and density functional methods have been used to study the ... more ABSTRACT A number of quantum chemical and density functional methods have been used to study the chemo- and regioselectivity of the uncatalysed and Lewis acid mediated cycloaddition of the nitrone PhCHN(Me)O with the CC or the CN bond of (E)-cinnamonitrile. In agreement with experimental evidence, Lewis acid coordination to the nitrile strongly promotes reaction at the CN bond over reaction at the alkene moiety. The main factors responsible for this inversion of the chemoselectivity were identified as the following: (i) the Lewis acid strongly stabilises the product of CN addition and the transition state leading to it, thus favouring this reaction both kinetically and thermodynamically. Addition across the CC bond, in contrast, only receives weak kinetic activation; (ii) the cycloaddition to the CC or CN bonds involves different molecular orbitals at the cinnamonitrile, and the Lewis acid influences the orbital involved in CN addition to a larger extent; (iii) the Lewis acid has a stronger effect on the electron distribution of the CN bond. As an overall result, the Lewis acid not only promotes the cycloaddition, but also alters the order of functional group reactivity and brings about a complete change in chemoselectivity.Graphical abstract
Camphor‐derived α‐dicarbonyl compounds and 3‐oxo‐camphorsulfonylimine have been synthesized from ... more Camphor‐derived α‐dicarbonyl compounds and 3‐oxo‐camphorsulfonylimine have been synthesized from the corresponding ketones or sulfonylimine by microwave‐assisted oxidation with selenium dioxide. Compared to the classical reaction conditions, good yields were obtained in much shorter reaction times. Additionally, the selenium precipitation is more quantitative, and its removal from the reaction mixture is easier.
Vinylbenzyl chloride was grafted onto PVDF and FEP polymer films using the radiation-grafting met... more Vinylbenzyl chloride was grafted onto PVDF and FEP polymer films using the radiation-grafting methodology. Subsequent reaction with trimethylamine and ion-exchange with potassium hydroxide yields alkaline anion-exchange membranes that are capable of conducting hydroxide ions; such membranes may be suitable for use in low temperature direct methanol fuel cells for portable devices. The PVDF based materials underwent an undesirable degradation and were found to be less suitable for this class of membrane. FEPbased materials exhibited superior structural stability, conductivities up to 0.02 S cm-1 at room temperature, and good retention of ionexchange capacities when treated in water at 60°C.
Uploads
Papers by Timothy Danks