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Photoinduced Acetylation of Anilines under Aqueous and Catalyst-Free Conditions
A green and efficient visible-light induced functionalization of anilines under mild conditions has been reported. Utilizing nontoxic, cost-effective, and water-soluble diacetyl as photosensitizer and acetylating reagent, and water as the solvent, a variety of anilines were converted into the corresponding aryl ketones, iodides, and bromides. With advantages of environmentally friendly conditions, simple operation, broad substrate scope, and functional group tolerance, this reaction represents a valuable method in organic synthesis.
Yang, Yu-Ming,Yan, Wei,Hu, Han-Wei,Luo, Yimin,Tang, Zhen-Yu,Luo, Zhuangzhu
p. 12344 - 12353
(2021/09/02)

Nickel-Catalyzed Reversible Functional Group Metathesis between Aryl Nitriles and Aryl Thioethers
We describe a new functional group metathesis between aryl nitriles and aryl thioethers. The catalytic system nickel/dcype is essential to achieve this fully reversible transformation in good to excellent yields. Furthermore, the cyanide- and thiol-free reaction shows high functional group tolerance and great efficiency for the late-stage derivatization of commercial molecules. Finally, synthetic applications demonstrate its versatility and utility in multistep synthesis.
Delcaillau, Tristan,Boehm, Philip,Morandi, Bill
supporting information
p. 3723 - 3728
(2021/04/07)

Synthesis method of aromatic benzyl ketone
The invention discloses a synthesis method of aromatic benzyl ketone, which comprises the following step: by using oxygen and/or air as an oxidant, oxidizing an aromatic benzyl compound shown in a formula (I) under the action of a catalytic system to obtain aromatic benzyl ketone shown in a formula (II). The catalytic system is formed by combining ferric ions, nitrate radicals and N-hydroxyimide derivatives and does not contain heavy metal ions harmful to human bodies, wherein the molar ratio of the ferric ions to the nitrate radicals is 1: (0.5-5), and the molar ratio of the ferric ions to the N-hydroxyimide derivatives is (0.01-0.1): (0.03-0.2). The method disclosed by the invention is wide in substrate applicability and high in atom utilization rate, avoids the use of harmful heavy metals such as copper and cobalt, and has the characteristics of high efficiency, economy and environmental protection. The formulas are as follows: Ar-CH2-R (I) and Ar-CO-R (II).
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Paragraph 0056-0061

(2020/09/12)

Selective Synthesis of Secondary and Tertiary Amines by Reductive N-Alkylation of Nitriles and N-Alkylation of Amines and Ammonium Formate Catalyzed by Ruthenium Complex
A new ruthenium catalytic system for the syntheses of secondary and tertiary amines via reductive N-alkylation of nitriles and N-alkylation of primary amines is proposed. Isomeric complexes 8 catalyze transfer hydrogenation and N-alkylation of nitriles in ethanol to give secondary amines. Unsymmetrical secondary amines can be produced by N-alkylation of primary amines with alcohols via the borrowing hydrogen methodology. Aliphatic amines were obtained with excellent yields, while only moderate conversions were observed for anilines. Based on kinetic and mechanistic studies, it is suggested that the rate determining step is the hydrogenation of intermediate imine to amine. Finally, ammonium formate was applied as the amination reagent for alcohols in the presence of ruthenium catalyst 8. Secondary amines were obtained from primary alcohols within 24 hours at 100 °C, and tertiary amines can be produced after prolonged heating. Secondary alcohols can only be converted to secondary amines with moderate yield. Based on mechanistic studies, the process is suggested to proceed through an ammonium alkoxy carbonate intermediate, where carbonate acts as an efficient leaving group.
Alshakova, Iryna D.,Nikonov, Georgii I.
p. 5370 - 5378
(2019/06/14)

Pd(II)-Catalyzed Denitrogenative and Desulfinative Addition of Arylsulfonyl Hydrazides with Nitriles
A Pd(II)-catalyzed denitrogenative and desulfinative addition of arylsulfonyl hydrazides with nitriles has been successfully achieved under mild conditions. This transformation is a new method for the addition reaction to nitriles with arylsulfonyl hydrazides as arylating agent, thus providing an alternative synthesis of aryl ketones. The reported addition reaction is tolerant to many common functional groups, and works well in the presence of electron-donating and electron-withdrawing substituents. Notably, the reported denitrogenative and desulfinative addition was also appropriate for alkyl nitriles, making this newly developed transformation attractive.
Meng, Mengting,Yang, Liangfeng,Cheng, Kai,Qi, Chenze
p. 3275 - 3284
(2018/03/25)

Preparation method of aromatic ketone
The invention discloses a preparation method of aromatic ketone. Under the effects of a palladium catalyst and a nitrogen-containing ligand, nitrile compounds and arylsulfonylhydrazide take desulfurization addition reaction in an organic solvent; after the reaction is completed, post treatment is performed to obtain aromatic ketone. The reaction is applicable to aromatic nitrile compounds, and isalso applicable to aliphatic nitrile compounds; the reaction realizes the wide substrate applicability and functional group tolerance; the potential application value is realized in the aspect of aryl-carbonyl building.
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Paragraph 0056; 0057; 0058; 0060

(2018/09/11)

Catalyst-free, efficient and one pot protocol for synthesis of nitriles from aldehydes using glycerol as green solvent
We described herein the novel, efficient and one-pot catalyst free protocol for the synthesis of nitriles from aldehydes by using hydroxyl amine hydrochlorides in glycerol as a green solvent. This protocol was efficiently used for transformation of aromatic aldehydes bearing electron-withdrawing and electron-donating groups into a aryl nitriles in good to excellent yields. The methodology offers a very simple, efficient and environmentally benign procedure.
Ingale, Ajit P.,Patil, Shripad M.,Shinde, Sandeep V.
p. 4845 - 4848
(2017/11/30)

Rhodium-Catalyzed Transnitrilation of Aryl Boronic Acids with Dimethylmalononitrile
An efficient transnitrilation of aryl boronic acids with dimethylmalononitrile (DMMN) is described. This rhodium-catalyzed electrophilic cyanation presents a novel approach to prepare aryl nitriles by using a carbon-bound cyanating reagent which undergoes cross-coupling with the aryl boronic acid. The reaction expands the degree of functional-group compatibility exhibited by the transnitrilation of aryl Grignard and aryllithium reagents. A variety of aryl boronic acid derivatives and dialkylmalononitriles were amenable to the transnitrilation.
Malapit, Christian A.,Reeves, Jonathan T.,Busacca, Carl A.,Howell, Amy R.,Senanayake, Chris H.
supporting information
p. 326 - 330
(2016/01/25)

Aryl Nitriles from Alkynes Using tert -Butyl Nitrite: Metal-Free Approach to C≡C Bond Cleavage
Alkyne C≡C bond breaking, outside of alkyne metathesis, remains an underdeveloped area in reaction discovery. Recently, nitrogenation has been reported to allow nitrile formation from alkynes. A new protocol for the metal-free C≡C bond cleavage of terminal alkynes to produce nitriles is reported. This method provides an opportunity to synthesize a vast range of nitriles containing aryl, heteroaryl, and natural product derivatives (38 examples). In addition, the potential of tBuONO to act as a powerful nitrogenating agent for terminal aryl alkynes is demonstrated. (Figure Presented).
Dutta, Uttam,Lupton, David W.,Maiti, Debabrata
supporting information
p. 860 - 863
(2016/03/01)

One-pot one-step deracemization of amines using ω-transaminases
In this study, we developed a one-pot one-step deracemization method for the production of various enantiomerically pure amines using two opposite enantioselective ω-TAs. Using this method, various aromatic amines were successfully converted to their (R)-forms (>99%) with good conversion.
Shin, Giyoung,Mathew, Sam,Shon, Minsu,Kim, Byung-Gee,Yun, Hyungdon
p. 8629 - 8631
(2013/09/23)

A chemoselective, one-pot transformation of aldehydes to nitriles
This paper describes a procedure for direct conversion of aldehydes to nitriles using O-(diphenylphosphinyl)hydroxylamine (DPPH). Aldehydes are smoothly transformed to their corresponding nitriles by heating with DPPH in toluene. The reaction can be accomplished in the presence of alcohol, ketone, ester, or amine functionality.
Laulhe, Sebastien,Gori, Sadakatali S.,Nantz, Michael H.
p. 9334 - 9337,4
(2012/12/12)

A chemoselective, one-pot transformation of aldehydes to nitriles
This paper describes a procedure for direct conversion of aldehydes to nitriles using O-(diphenylphosphinyl)hydroxylamine (DPPH). Aldehydes are smoothly transformed to their corresponding nitriles by heating with DPPH in toluene. The reaction can be accomplished in the presence of alcohol, ketone, ester, or amine functionality.
Laulhé, Sébastien,Gori, Sadakatali S.,Nantz, Michael H.
p. 9334 - 9337
(2013/01/15)

An expedient Pd/DBU mediated cyanation of aryl/heteroaryl bromides with K4[Fe(CN)6]
A practical Pd(PPh3)4/DBU catalytic system for the synthesis of pharmaceutically relevant aminopyridine nitrile intermediates, as well as a variety of other aryl nitriles using non-toxic K4[Fe(CN) 6] has been developed. The key features of our new protocol for cyanation lie in that the reaction can be carried out with readily available Pd(PPh3)4 under mild and green conditions, even without the assistance of other ligands. The Royal Society of Chemistry 2012.
Zhang, Dengyou,Sun, Haifeng,Zhang, Lei,Zhou, Yu,Li, Chunpu,Jiang, Hualiang,Chen, Kaixian,Liu, Hong
supporting information; experimental part
p. 2909 - 2911
(2012/03/27)

Microwave-enhanced synthesis of aryl nitriles using dimeric orthopalladated complex of tribenzylamine and K4[Fe(CN)6]
The activity of palladacycle [Pd{C6H4(CH 2N(CH2Ph)2)} (μ-Br)]2 complex was investigated in the synthesis of benzonitriles under both conventional and microwave irradiation conditions and their results were compared together. This complex is an efficient, stable, and non-sensitive to air and moisture catalyst for the cyanation reaction. The substituted benzonitriles were produced of various aryl halides in excellent yields and short reaction times using a catalytic amount of [Pd{C6H4(CH2N(CH 2Ph)2)} (μ-Br)]2 complex and K 4[Fe(CN)6] in DMF at 130 °C. In comparison to conventional heating conditions, the reactions under microwave irradiation gave higher yields in shorter reaction times.
Hajipour, Abdol Reza,Rafiee, Fatemeh,Ruoho, Arnold E.
experimental part
p. 526 - 529
(2012/02/01)

Microwave-assisted one-step synthesis of acetophenones via palladium-catalyzed regioselective arylation of vinyloxytrimethylsilane
The regiochemistry of the palladium-mediated arylation (Heck arylation) of enol ethers is sensitive to the structure of the enol ether, the arylating agent and the catalytic system. In this study, an effective and practical method was successfully developed for the synthesis of acetophenones with high regioselectivity under palladium-catalyzed conditions. A variety of acetophenones was readily prepared from aryl iodides in good to excellent yields under microwave irradiation in a single step. The key feature of our new protocol is the use of vinyloxytrimethylsilane as a highly regioselective acylation reagent. Copyright
Qian, Wangke,Zhang, Lei,Sun, Haifeng,Jiang, Hualiang,Liu, Hong
supporting information
p. 3231 - 3236
(2013/01/15)

Rational catalysis design on the basis of mechanistic understanding: Highly efficient Pd-catalyzed cyanation of aryl bromides with NaCN in recyclable solvents
Rational catalysis design on the basis of a detailed mechanistic understanding has been used to successfully develop the first efficient general Pd-catalyzed aromatic cyanation reaction under the highly sought after practicable conditions: (i) MCN (M = Na or K) as a cyanide source; (ii) low-boiling recyclable solvents; and (iii) minimal quantities of inexpensive, nontoxic promoters. The developed catalytic reaction converts aromatic bromides to the corresponding nitriles in 88-99% isolated yield with NaCN and 0.5-1.0 mol % of a t-Bu3P-monoligated Pd catalyst in MeCN-THF within 2 h at 70 °C. The process exhibits high functional group tolerance.
Ushkov, Alexander V.,Grushin, Vladimir V.
experimental part
p. 10999 - 11005
(2011/09/16)

An efficient palladium catalytic system for microwave assisted cyanation of aryl halides
Application of a new catalytic system for cyanation reaction of various aryl halides using K4[Fe(CN)6] as cyanating source was examined. The reactions were performed under microwave irradiation and results showed that application of this catalytic system and DMF at 130 °C minimized the reaction times from hours to minutes in good to excellent yields.
Hajipour, Abdol R.,Karami, Kazem,Tavakoli, Ghazal,Pirisedigh, Azade
experimental part
p. 819 - 824
(2011/03/21)

Candida tenuis xylose reductase catalysed reduction of acetophenones: The effect of ring-substituents on catalytic efficiency
The catalytic efficiencies of Candida tenuis xylose reductase catalysed reductions of mono-substituted acetophenones are in reasonable correlation with the σ-Hammett coefficients of the substituted phenyl groups. Variations of the substrate transformation rates are hence mainly caused by mesomeric and inductive effects of the substituents, while differences in substrate binding have a secondary relevance. Some substrate 1H NMR chemical shifts and carbonyl IR absorption bands are in reasonable accordance with the catalytic activities and allow the estimation of the transformation rates with good accuracy. The resulting substituted (S)-1-phenyl ethanols are generated in very high enantiomeric excess.
Vogl, Michael,Kratzer, Regina,Nidetzky, Bernd,Brecker, Lothar
experimental part
p. 5863 - 5870
(2011/09/30)

Competition between azido cleavage and triplet nitrene formation in azidomethylacetophenones
Photolysis of p- and m-azidomethylacetophenone (1a, 1b) in argon-saturated solutions yields predominantly imine 2a, 2b, whereas irradiation of 1a, 1b in oxygen-saturated solutions results in heterocycles 3a, 3b, aldehydes 4a, 4b and nitriles 5a, 5b. Density functional theory calculations place the energy of the first and second excited state of the triplet ketones (T1K and T 2K) in 1a, 1b in close proximity to each other. The triplet transition state for cleaving the CN bond in 1a, 1b to form azido and benzyl radicals 1aB, 1bB is located only 3 kcal mol-1 (1 kcal = 4.184 kJ) above T1K, indicating that azido cleavage is feasible. The calculations place the energy of the triplet azido group (TA) in 1a, 1b ～25 kcal mol-1 below T1K; thus, this process is also easily accessible via energy transfer. Further, the transition state barrier for TA to expel N2 and form triplet nitrenes is less than 1 kcal mol-1 above TA in 1a, 1b. Laser flash photolysis of 1a, 1b reveals the formation of the triplet excited ketones of 1a, 1b, which decay to form benzyl radicals 1aB, 1bB and triplet alkylnitrenes. The triplet ketones and the benzyl radicals are quenched with molecular oxygen at rates close to diffusion, whereas the triplet nitrenes react more slowly with oxygen (～5 × 105 M-1s-1). We conclude that the triplet alkylnitrenes intercept the benzyl radicals to form 2 in argon-saturated solution, whereas the benzyl radicals are trapped to form 4 in oxygen-saturated solution; thus, the triplet nitrenes react with oxygen to form 3. CSIRO 2010.
Ranaweera, Ranaweera A. A. Upul,Zhao, Yu,Muthukrishnan, Sivaramakrishnan,Keller, Christopher,Gudmundsdottir, Anna D.
p. 1645 - 1655
(2011/09/14)

Palladium-catalyzed cyanation reaction of aryl halides using K 4[Fe(CN)6] as non-toxic source of cyanide undermicrowave irradiation
An efficient method for preparation of aryl nitriles - using [Pd{C 6H2(CH2CH2 NH2)-(OMe) 2,3,4} (μ-Br)]2 complex as an efficient catalyst and K4[Fe(CN)6] as a green cyanide source - from aryl bromides, aryl iodides and aryl chlorides under microwave irradiation has been reported. This complex has been demonstrated to be an active and efficient catalyst for this reaction.Using a catalytic amount of this synthesized palladium complex in DMF at 130 ° led to production of the cyanoarenes in excellent yields in short reaction times. Copyright
Hajipour, Abdol R.,Karami, Kazem,Pirisedigh, Azadeh
experimental part
p. 454 - 457
(2010/09/06)

Hydrogen-bond-directed catalysis: Faster, regioselective and cleaner heck arylation of electron-rich olefins in alcohols
A general method for the regioselective Heck reaction of electronrich olefins is presented. Fast, highly regioselective Pd-catalysed α-arylation of electron-rich olefins, vinyl ethers (1a-d), hydroxyl vinyl ethers (1e,f), enamides (1g,h) and a substituted vinyl ether (1i) has been accomplished with a diverse range of aryl bromides (2a-r), for the first time, in cheap, green and easily available alcohols with no need for any halide scavengers or salt additives. The reaction proceeds with high efficiency, leading exclusively to the a-products, in 2-propanol and particularly in ethylene glycol. In the latter, the arylation can be catalysed at a palladium loading of 0.1 mol% and finish in as short a time as 0.5 h. The remarkable performance of the alcohol solvents in promoting a regiocontrol is attributed to their hydrogen-bond- donating capability, which is believed to facilitate the dissociation of halide anions from PdII, and hence, the generation of a key ionic Pd II-olefin intermediate responsible for the a product. This belief is further strengthened by the study of a benchmark arylation reaction in 21 different solvents. The study revealed that exclusive α-regioselective arylation takes place in almost all of the protic solvents, and there is a rough correlation between the α-arylation rates and the solvent parameter ETN. The method is simpler, cleaner and more general than those established thus far.
Hyder, Zeynab,Ruan, Jiwu,Xiao, Jianliang
experimental part
p. 5555 - 5566
(2009/06/17)

Open air palladium catalyzed cyanation-the use of PMHS to protect from oxygen
PMHS (polymethylhydrosiloxane) used in catalytic amounts has a remarkable ability to prevent catalyst poisoning by oxygen contamination during palladium catalyzed cyanation reactions. The procedure is applicable to a wide range of substrates and is so effective that it allows the reactions to be run fully open to the atmosphere.
Martin, Michael T.,Liu, Bing,Cooley Jr., Bobby E.,Eaddy, John F.
p. 2555 - 2557
(2007/10/03)

Palladium-catalyzed, copper(I)-mediated coupling of boronic acids and benzylthiocyanate. A cyanide-free cyanation of boronic acids
(Equation Presented) A new method for the synthesis of nitriles is described. As a complement to the classic cyanation of aryl halides using cyanide sources and a transition metal catalyst, the palladium-catalyzed cross-coupling of thiocyanates with boronic acids in the presence of copper(I) thiophene-2-carboxylate (CuTC) affords nitriles in good to excellent yields.
Zhang, Zhihui,Liebeskind, Lanny S.
p. 4331 - 4333
(2007/10/03)

Cyanation of aromatic halides
A practical, ligand-free cyanation of aryl bromides employs Pd catalyst in combination with a non-toxic cyanide source, Mn[Fe(CN)6] (M=K or Na; n is 3 or 4), or a hydrate thereof, and a base. The reactions are performed in a polar aprotic solvents and provide the corresponding aryl nitrile in 83-96% yield, typically in less than 5 h.
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Page/Page column 6-8

(2008/06/13)

Ionic liquid-promoted, highly regioselective Heck arylation of electron-rich olefins by aryl halides
Palladium-catalyzed regioselective Heck arylation of the electron-rich olefins, vinyl ethers 1a-d, enamides 1e-g, and allyltrimethylsilane 1h, has been accomplished in imidazolium ionic liquids with a wide range of aryl bromides and iodides instead of the commonly used, but commercially unavailable and expensive, aryl triflates. The reaction proceeded with high efficiency and remarkable regioselectivity without the need for costly or toxic halide scavengers, leading exclusively to substitution by aryl groups of diverse electronic and steric properties at the olefinic carbon α to the heteroatom of 1a-g and β to the heteroatom of 1h. In contrast, the arylation reaction in molecular solvents led to mixtures of regioisomers under similar conditions. Several lines of evidence point to the unique regiocontrol stemming from the ionic environment provided by the ionic liquid that alters the reaction pathway. The chemistry provides a simple, effective method for preparing branched, arylated olefins and contributes to the extension of Heck reaction to a wider range of substrates.
Mo, Jun,Xu, Lijin,Xiao, Jianliang
p. 751 - 760
(2007/10/03)

Application of polymer-supported triphenyl phosphine in the palladium-catalyzed cyanation reaction under microwave conditions
A variety of aryl nitriles were prepared in excellent yields from the palladium acetate catalyzed coupling of aryl halides with Zn(CN)2 using polymer-supported triphenyl phosphine as the ligand and dimethylformamide as solvent under microwave irradiation conditions.
Srivastava, Rajiv R.,Collibee, Scott E.
p. 8895 - 8897
(2007/10/03)

Convenient Processes for the Synthesis of Aromatic Ketones from Aryl Bromides and Carboxylic Anhydrides Using a Cobalt Catalysis
The cross-coupling of various para- and meta-substituted aromatic bromides, mostly bearing sensitive moieties, with several carboxylic acid anhydrides is reported. This reaction can be carried out in two steps, by forming an aromatic organozinc reagent via cobalt catalysis in the first step, or even more interestingly in a single step, also by using a cobalt-based catalyst. The aromatic ketones are obtained by these new, mild, and convenient methods in 30-79% yields versus starting aryl bromide. Results are also disclosed that suggest the role played by cobalt species in the coupling of organozinc reagents with electrophiles could be similar to those of more commonplace transition metal complexes.
Kazmierski, Igor,Bastienne, Mylene,Gosmini, Corinne,Paris, Jean-Marc,Perichon, Jacques
p. 936 - 942
(2007/10/03)

The Room-Temperature Palladium-Catalyzed Cyanation of Aryl Bromides and Iodides with Tri-t-butylphosphine as Ligand
The palladium-catalyzed cyanation of aryl bromides and iodides to the corresponding nitriles occurs at room temperature when tri-t-butylphosphine is used as ligand, Zn(CN)2 as the cyanide source and Zn dust as a co-catalyst in DMF as solvent. A variety of aromatic halides, including electron-withdrawing and electron-donating, can be efficiently cyanated under these conditions. The reactions are completed in less than 1 hour and products are produced in good to excellent yield.
Ramnauth, Jailall,Bhardwaj, Namrta,Renton, Paul,Rakhit, Suman,Maddaford, Shawn P.
p. 2237 - 2239
(2007/10/03)

A convenient method for the preparation of aromatic ketones from acyl chlorides and arylzinc bromides using a cobalt catalysis
Aromatic ketones are synthesized efficiently via cobalt catalyzed cross-coupling reaction between arylzinc bromides and acid chlorides. Arylzinc bromides prepared chemically via a cobalt catalysis undergo coupling without additional catalyst unlike their electrochemical analogs.
Fillon, Hyacinthe,Gosmini, Corinne,Périchon, Jacques
p. 8199 - 8202
(2007/10/03)

Synthesis of 3-substituted benzamides and 5-substituted isoquinolin-1(2H)-ones and preliminary evaluation as inhibitors of poly(ADP-ribose)polymerase (PARP)
Inhibitors of poly(ADP-ribose)polymerase (PARP) inhibit repair of damaged DNA and thus potentiate radiotherapy and chemotherapy of cancer. 3-Substituted benzamides and 5-substituted isoquinolin-1-ones have been synthesised and evaluated for inhibition of PARP. Reduction of 3-(bromoacetyl)benzamide, followed by treatment with base, gave RS-3-oxiranylbenzamide. Reduction of 3-(hydroxyacetyl)benzonitrile with bakers' yeast gave the R-diol which was converted to R-3-(1,2-dihydroxyethyl)benzamide. Similar reduction of 3-(acetoxyacetyl)benzonitrile led towards the S-diol which was converted to its cyclic acetonide. E-2-(2,6-Dicyanophenyl)-N,N-dimethylethenamine was formed by condensation of 2,6-dicyanotoluene with dimethylformamide dimethyl acetal (DMFDMA); cyclisation under acidic conditions afforded 5-cyanoisoquinolin-1-one. Heck coupling of 5-iodoisoquinolin-1-one with propenoic acid formed E-3-(1-oxoisoquinolin-5-yl)propenoic acid. 3-Oxiranylbenzamide, 5-bromoisoquinolin-1-one and 5-iodoisoquinolin-1-one were among the most potent inhibitors of PARP activity in a preliminary screen in vitro. Copyright (C) 1998 Elsevier Science Ltd.
Watson, Corrine Y.,Whish, William J. D.,Threadgill, Michael D.
p. 721 - 734
(2007/10/03)

α-Regioselectivity in Palladium-Catalyzed Arylation of Acyclic Enol Ethers
Regioselective α-arylation of acyclic enol ethers by aryl trifluoromethanesulfonates, aryl bromide, aryl iodides, and aroyl chlorides is described.The outcome of the reaction proved to be dependent from the relationship between ligand and counterion in the oxidative complex.
Cabri, Walter,Candiani, Ilaria,Bedeschi, Angelo,Penco, Sergio,Santi, Roberto
p. 1481 - 1486
(2007/10/02)

The Photochemistry of Carbon-Nitrogen Multiple Bonds in Aqueous Solution. 1. Aromatic Oximes, Oxime Ethers, and Nitriles
The photochemistry of typical C=N and CN compounds was investigated in aqueous solution from pH 2 to 12.It was found that both aromatic aldoximes and ketoximes readily undergo photohydrolysis via their lowest singlet states, with Φ values generally in the 0.01 - 0.15 range.Both the neutral oxime and oximate anion undergo photohydrolysis, with the former reaction being acid-catalyzed.For both forms of the oxime, evidence was obtained for oxazirane intermediates.For the neutral form, there is also a less efficient hydrolysis mechanism, which is important at pH 8 - 10 and involves the uncatalyzed addition of water to the C=N bond.A similar uncatalyzed hydrolysis mechanism is found for the oxime ethers at all pH's.The unsubstituted oxime ethers photohydrolyze only by the pH independent route with a photoefficiency (Φ = 0.01-0,025) that is practically identical with that of the parent oximes in the Ph 8 - 10 range.Attempts were made to photohydrolyze analogously substituted benzonitriles under the same conditions, since fluorescence quenching in acid solution had shown that their lowest singlet states exhibit greatly enhanced basicity.Surprisingly all attempts to photohydrolyze the nitriles were unsuccessful.
Haley, M. F.,Yates, K.
p. 1817 - 1824
(2007/10/02)

Deactivation of Triplet Phenyl Alkyl Ketones by Conjugatively Electron-Withdrawing Substituents
Para-cyano, -carbomethoxy, and -acyl substituents decrease the triplet reactivity of valerophenone (γ-hydrogen abstraction), whereas comparable meta substituents increase reactivity.Spectroscopic results are presented which indicate that para-(-R) substituents lower ?,?* triplet energies so much more than n,?* energies that the lowest triplets become largely ?,?* in nature.Meta-(-R) substituents do not stabilize ?,?* triplets enough to invert triplet levels.Both substitution patterns support a largely 1,4-biradical structure for the lowest ?,?* triplet of acylbenzenes.Ortho substituents show the usual steric anomalies: ortho cyano enhances valerophenone triplet reactivity by stabilizing the n,?* triplet; ortho carbomethoxy deactivates valerophenone by stabilizing the ?,?* triplet but not the n,?.*
Wagner, Peter J.,Siebert, Elizabeth J.
p. 7329 - 7335
(2007/10/02)