Dicarbonyl compounds Iodine

Keywords Indoles, 1,3-dicarbonyl compounds, iodine, solvent-free, room temperature, ctni-densation, 3-alkenylated indoles, bis(indolyl)carbonyl compounds... 

A mixture of 1,4-dioxane and water is often used as the solvent for the conversion of aldehydes and ketones by H2Se03 to a-dicarbonyl compounds in one step (Eq. 8.117).331 Dehydrogenation of carbonyl compounds with selenium dioxide generates the a, (i-unsaturated carbonyl compounds in aqueous acetic acid.332 Using water as the reaction medium, ketones can be transformed into a-iodo ketones upon treatment with sodium iodide, hydrogen peroxide, and an acid.333 Interestingly, a-iodo ketones can be also obtained from secondary alcohol through a metal-free tandem oxidation-iodination approach. 

The purpose of present review is to summarize the application of different classes of iodine(III) compounds in carbon-carbon bond forming reactions. The first two sections of the review (Sects. 2 and 3) discuss the oxidative transformations induced by [bis(acyloxy)iodo] arenes, while Sects. 4 through 9 summarize the reactions of iodonium salts and ylides. A number of previous reviews and books on the chemistry of polyvalent iodine discuss the C-C bond forming reactions [1 -10]. Most notable is the 1990 review by Moriarty and Vaid devoted to carbon-carbon bond formation via hypervalent iodine oxidation [1]. In particular, this review covers earlier literature on cationic carbocyclizations, allyla-tion of aromatic compounds, coupling of /1-dicarbonyl compounds, and some other reactions of hypervalent iodine reagents. In the present review the emphasis is placed on the post 1990s literature. 

A novel hypervalent iodine-induced direct intramolecular cyclization of a-(aryl)alkyl-jS-dicarbonyl compounds 33 has been recently reported (Scheme 15) [30]. Both meta- and para-substituted phenol ether derivatives containing acyclic or cyclic 1,3-dicarbonyl moieties at the side chain undergo this reaction in a facile manner affording spirobenzannulated compounds 34 that are of biological importance. 

A hypervalent iodine-induced intramolecular cyclization of the a-(aryl)alkyl-P-dicarbonyl compound 482 furnishes the spirobenzannulated chroman 483 in good yield (Equation 197) <2001JOC59>. 

Acetyl hypoiodite (iodine acetate), CH3COOI, is prepared by treatment of silver acetate in acetic acid with iodine at room temperature [779, 780], The reagent cleaves vicinal diols to dicarbonyl compounds [779] and degrades tertiary alcohols to ketones [780], Acetyl hypoiodite is also an intermediate in the reaction of alkenes with the so-called Simonini complex, an addition product of iodine with 2 mol of silver acetate [781, 782, 783],... 

Substitutwns. Iodine assists the Sn2 substitution of allylic alcohols to form sulfonamides and carbamates. Allylic alcohols are sufficiently electrophilic toward 1,3-dicarbonyl compounds in the presence of iodine. ... 

Dimerization of fi-dicarbonyl compounds. The dicarbanions of 3-dicarbonyl / compounds are dimerized by treatment with iodine (or bromine) when catalyzed by cuprous chloride or cobaltous chloride. ... 

Hypervalent iodine reagents in combination with a source of appropriate nucleophiles are commonly used to prepare products with new C—S and C—Se bonds. Moriarty and coworkers have developed convenient procedures for the thiocyanation of organic substrates using the combination of PhICh with Pb(SCN)2 [592-594], Various enol silyl ethers 524, ketene silyl acetals 526 and 528 and p-dicarbonyl compounds 530 can be effectively thiocyanated with this combination of reagents to produce the respective thiocyanato... 

Iodosylbenzoic acid (85) is also a convenient recyclable hypervalent iodine oxidant for the synthesis of a-iodo ketones by oxidative iodination of ketones [88], Various ketones and p-dicarbonyl compounds can be iodinated by this reagent system under mild conditions to afford the respective a-iodo substituted carbonyl compounds in excellent yields. The final products of iodination are conveniently separated from by-products by simple treatment with anionic exchange resin Amberlite IRA 900 HCOs" and are isolated with good purity after evaporation of the solvent. The reduced form of the hypervalent iodine oxidant, 3-iodobenzoic acid (59), can be recovered in 91-95% yield from the Amberlite resin by treatment with aqueous hydrochloric acid followed by extraction with ethyl acetate [88]. 

The a-protons of p-dicarbonyl compounds are highly acidic (pKg about 13). Sodium hydride is a strong base, lodobutane is a good electrophile, since iodide is a good leaving group and its electronegativity polarises the carbon-iodine bond. 

The formation of dicarbonyl compounds by this reagent is a variation of the Kornblum oxidation and presumably involves acid-catalyzed iodination of the carbonyl compound (1) to give an a-iodo ketone (2) which undergoes displacement by DMSO to... 

Bandyopadhyay D, Mukheqee S et al (2010) An effective microwave-induced iodine-catalysed method for the synthesis of quinoxalines via condensation of 1,2-diamine with 1,2-dicarbonyl compounds. Molecules 15 4207-4212... 

Joshi et al. [67] developed an efficient and simple one-pot synthesis of some new symmetrical, unsymmetrical, and iV-substituted Hantzsch 1,4-DHPs 48 and 49 using molecular iodine as catalyst by the reaction of aldehydes, 1,3-dicarbonyl compound, and ammonium acetate/aromatic amine in EtOH. This new method has the advantage of good to excellent product yields and shorter reaction times at ambient temperature (Scheme 10.32). 

Banik et al. [107] developed a microwave-induced iodine-catalyzed simple, rapid, and convenient method for the synthesis of different types of quinoxaline derivatives 71 via condensation of t,2-diamines with t,2-dicarbonyl compounds (Scheme 10.53). The model reaction between o-phenylenediamine and phenylg-lyoxal monohydrate in the presence of iodine as a catalyst using microwave irradiation has been performed in different solvent systems and the best results were obtained when EtOH/H O (1 1) was used as a solvent. 

A mixture of indole derivative (1 1 mmol), 1,3-dicarbonyl compound (2 1 mmol) and molecular iodine (10 mol%) was stirred at room temperature in a round-bottom flask for 2-3 h. After completion of the reaction (as monitored by TLC) a saturated aqueous solution of Na2S203 (2x5 mL) was added, and the mixture was extracted with EtOAc (3x5 mL). The combined organic phases were dried over anhydrous sodium sulfate, filtered, and evaporated under reduced pressure to obtain the crude product of 3-alkenylated indole (3)/3-alkylated indole (4) which was then purified using column chromatography. Each of the products (3 and 4) was characterized on the basis of spectral and elemental analyses. 

Singh, N., and Singh, K. N. (2012). Iodine-catalyzed highly efficient synthesis of 3-alkylated/3-alkenylated indoles from 1,3-dicarbonyl compounds. Synlett, 23, 2116-2120. 

Method 2. To a solution of amine (1 1 mmol) and 1,4-dicarbonyl compound (2 1.2 mmol) in THF (5 mL) was added iodine (0.1 mmol). The mixture was then stirred at room temperature for specified period of 0.5-20 h for varying entries to complete the reaction as monitored by TLC. The cmde mixture was extracted with dichloromethane (20 mL), and was washed successively with 5% Na2S203 solution (2 mL), saturatedNaHCOs solution (2 mL), and brine (2 mL). The organic layer was then dried with sodium sulfate and concentrated to afford pyrrole 3 in sufficiently pure form (>90%). In case of one of the reactants being Uquid, the experiment was conducted without using solvent however, addition of a small amount of ordinary THF or dichloromethane was required for a very thick slurry reaction mixture to ensure a better outcome of the reaction. After completion of the reaction, the crude product was extract with dichloromethane, washed, dried, and the subjected to column chromatography for purification (15-93% yield). 

Arisawa, M., Ramesh, N.G., Nakajima, M., Tohma, H., and Kita, Y, Hypervalent iodine(lll)-induced intramolecular cychzation of a-(aryl)alkyl-P-dicarbonyl compounds a convenient synthesis of benzarmulated and spirobenzannulated compounds, /. Org. Chem., 66, 59, 2001. Eberson, L., Reaction between organic and metal ion species, in Electron Transfer Reactions in Organic Chemistry, Reactivity and Structure, Vol. 25, Hafner, K., Lehn, J.-M., Rees, C.W., von Rague-Schleyer, R, Trost, B.M., and Zahradnik, R, Eds., Springer-Verlag, Berhn, 1987, chap. 7. Bockman, T.M., ShuMa, D., and Kochi, J.K., Photoinduced electron transfer from enol silyl ethers to quinone. Part 1. Pronounced effects of solvent polarity and added salt on the formation of a-enones, J. Chem. Soc., Perkin Trans. 2, 1623, 1996. 

The hypervalent iodine-induced direct intramolecular cyclization of a-(aryl)alkyl-p-dicarbonyl derivatives 305 affords biologically important spirobenzannulated compounds 306 (Scheme 3.125) [366]. 

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