Arnold reaction

The hydrazinoyl-substituted imidazothiadiazole 188 under Vilsmeier-Haack-Arnold reaction conditions gives the tricyclic thiadiazoloimidazopyridazinone 189 <2006SC1837> (Equation 20). 

TL5981>. The proposed mechanism involves the oxidation of the amine to an imine, tautomerization to an enamine, and a sequence of nucleophilic attacks on the pyridazine rings followed by oxidation steps. The oxidant of choice is (bispyridine)silver permanganate <1982TL1847>, which is easily prepared, mild in action, and is soluble in organic media. If R1 = H in the product 77, electrophilic substitution (e.g., bromination, nitration, Mannich, and Vilsmeier-Haack-Arnold reactions) occurs at this position. 

The Vilsmeier (or Vilsmeier-Haack or Vilsmeier-Haack-Arnold) reaction is primarily a mild method for formylating a wide variety of substrates.1 It has limited application to higher acylation and involves the reaction of a Vilsmeier reagent derived from a tertiary amide and an acid chloride (or occasionally a bromide). The most commonly employed amide is jV,N-dimethylformamide (DMF) and the acid chloride is generally phos-phoryl chloride, though phosgene and thionyl chloride are also employed. 

Selinene is another sesquiterpene found in woods. Its behaviour in the Vilsmeier-Haack-Arnold reaction is, like that of the acylation of cedrene using titanic chloride as a catalyst, another interesting and surprising piece of sesquiterpenoid carbocation chemistry. 

The Vilsmeier-Haack-Arnold reaction involves the addition of an imminium ion to an olefin as shown in Figure 6.34. The imminium ion... 

Chlorovinyl aldehydes 16 result from a-methylene ketones by the action of DMF/POCI3 (the Vilsmeier-Haack-Arnold reaction) ... 

Arnold reaction. frans-But-2-enyl mesitoate and ii-butylmagnesium bromide prepared from n-butyl bromide and ca. 5% excess Mg in ether stirred and refluxed 12 hrs. trans-oct-2-ene (containing 10% 3-methylhept-l-ene). Y 59%. —No c/s-isomer could be found. This method allows some fairly selective syntheses of hitherto difficultly accessible frans-trialkylethylenes. F. e. s. G. M. G. Higgins, B. Saville, and M. B. Evans, Soc. 1965, 702. 

Viggiano A A, Arnold S T and Morris R A 1998 Reactions of mass selected cluster ions in a thermal bath gas Int. Rev. Phys. Chem. 17 147-84... 

Greene C H and Toennies J P 1964 Chemicai Reactions in Shock Waves (London Arnold)... 

The Chemistry of Heterocyclic Compounds has been published since 1950 under the initial editorship of Arnold Weissberger, and later, until his death in 1984, under the joint editorship of Arnold Weissberger and Edward C. Taylor. In 1997, Peter Wipf joined Prof. Taylor as editor. This series attempts to make the extraordinarily complex and diverse held of heterocyclic chemistry as organized and readily accessible as possible. Each volume has traditionally dealt with syntheses, reactions, properties, structure, physical chemistry, and utility of compounds belonging to a specihc ring system or class (e.g., pyridines, thiophenes, pyrimidines, three-membered ring systems). This series has become the basic reference collection for information on heterocyclic compounds. 

Arnold AW, Hausermann P, Bach S, Bircher AJ Recurrent flexural exanthema (SDRIFE or baboon syndrome) after administration of two different iodinated radiocontrast media. Dermatology 2007 214 89-93. Laroche D Immediate reactions to contrast media mediator release and value of diagnostic testing. Toxicology 2005 209 193-194. 

The procedure described is essentially that of Arnold, Parham, and Dobson2 based on the reaction reported by Vorlander and Pritzsche. This acid has also been prepared from ethyl tri-... 

K Bailey. The Retardation of Chemical Reactions. London Edward Arnold, 1937. 

Lindroos, S. Arnold, A. Leskela, M. 2000. Growth of CuS thin films by the successive ionic layer adsorption and reaction method. Appl. Surf. Sci. 158 75-80. 

Arnold, B.R. Bucher, G. Netto-Ferreira, J.C. Platz, M.S. Scaiano, J.C. Biradicals, Radicals in Excited States, Carbenes and Related Species. In Landolt-Bomstein, Radical Reaction Rates in Liquids, W. Marlienssen, Ed. SpringenBerlin, 1998 Vol. New Series II/18E2, Chapter 14, pp 141-349. 

Examples of autocatalytic reactions include the decomposition of C2H4I2 either in the gas phase or in solution in CC14 (Arnold and Kistiakowsky, 1933), hydrolysis of an ester, and some microbial fermentation reactions, The first of these may be used to illustrate some observed and mechanistic features. 

Feringa, B. L. Naasz, R. Imbos, R. Arnold, L. A. Copper-catalyzed Enantioselective Conjugate Addition Reactions of Organozinc Reagents. In Modem Organocopper Chemistry Krause, N. Ed. Wiley-VCH GmbH Weinheim, 2002 Chapter 7, pp 224—258. 

The regiochemistry of nucleophilic addition to alkene radical cations is a function of the nucleophile and of the reaction conditions. Thus, water adds to the methoxyethene radical cation predominantly at the unsubstituted carbon (Scheme 3) to give the ff-hydroxy-a-methoxyethyl radical. This kinetic adduct is rearranged to the thermodynamic regioisomer under conditions of reversible addition [33]. The addition of alcohols, like that of water, is complicated by the reversible nature of the addition, unless the product dis-tonic radical cation is rapidly deprotonated. This feature of the addition of protic nucleophiles has been studied and discussed by Arnold [5] and Newcomb [84,86] and their coworkers. 

A relatively short but interesting paper by Arnold et al.55 suggests different calibrations for different segments of a bioreaction. Using the cultivation of S. fradiae and monitoring the oils and tylosin, the reaction was followed for 150 h. It was determined that the extensive matrix changes over the entire reaction time would make calibration difficult. The process was broken into (1) 0 to 50 h, (2) 50 to 100 h, and (3) 100+ h. 

As mentioned earlier, an electrode reaction implies some orientation effect because a substrate molecule must be fairly close to the electrode surface. The following pairs of cis and trans isomers were reported to exhibit identical reduction potentials l,2-dimethyl-l,2-diphenylethylenes (Weinberg and Wienberg 1968) l,2-bis(4-cyanophenyl)-l,2-bis(4-methoxyphenyl) ethylenes (Leigh and Arnold 1981) and l,2-bis(4-acetylphenyl)-l,2-diphenylethylenes (Wolf et al. 1996). 

Additionally, we should mention the photoinitiated reaction between diphenylbutadiene cation-radical and AN (Mattes and Farid 1980 Scheme 7.29). De Lijser and Arnold (1998) have given a theoretical explanation to this reaction. 

Buth JM, Arnold WA, McNeill K (2007) Unexpected products and reaction mechanisms of the aqueous chlorination of cimetidine. Environ Sci Technol 41(17) 6228-6233... 

Jones JK, Idanpaan-HeikkUa, JE. Adverse Reactions, Postmarketing Surveillance and Pharmacoepidemiology. In Burley DM, Qarke JM, Lasagna L, Edward Arnold, eds. Pharmaceutical Medicine. A Division of Hodder Stoughton Publishers, 1993 145-80. 

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