Ketones diacetoxyiodo benzene

Carbonyl compounds can be functionalized in the a-position under various conditions. Treatment of ketones with (diacetoxyiodo)benzene 3, iodosoben-zene 5, or 2-iodoxybenzoic acid (IBX) 7 under basic conditions provides effi-... 

In contrast to (diacetoxyiodo)benzene, [bis(trifluoroacetoxy)iodo]benzene, (BTI) reacts in aqueous solvents with both terminal and non-terminal alkynes affording eventually a-hydroxyketones and 1,2-diketones, respectively. The primary reaction of terminal alkynes leads to the formation of alkynyl phenyliodonium salts, which are not isolable under the experimental conditions but have been prepared by other routes (Section 9.1.3) these are hydrolysed in situ to a-hydroxymethyl ketones, through the intermediacy of their O-tri fluoroacetates, which sometimes may be isolated as by-products. 

The most commonly used synthesis of [l,2,3]triazolo[l,5-fl]pyridines remains that from the hydrazones of 2-p) idyl-carboxaldehydes or -ketones by oxidation. Some hydrazones give triazolop) dines when boiled in methanol in the presence of air, but all other reported cases require an added oxidant. The use of the most common oxidants illustrates the versatility of the synthesis. Nickel peroxide, potassium ferrocyanide and bicarbonate, air and a copper-II salt, manganese dioxide or (diacetoxyiodo)benzene have been used (02AHC1). An alternative route from tosylhydrazones of 2-pyridyl-carboxaldehydes or ketones by treatment with base, usually morpholine, has been used for high yields of sensitive materials (02AHC1). 

In contrast with X, -iodanes (Section 3.2), hypervalent iodine(III) reagents are not effective oxidants of alcohols in the absence of catalysts. Kita and coworkers were the first to find that, in the presence of bromide salts, iodosylbenzene or (diacetoxyiodo)benzene can be used as an efficient reagent for selective oxidation of alcohols [136,137]. The iodosylbenzene-KBr system is applicable to the oxidation of various primary and secondary alcohols, even in the presence of sensitive functional groups such as ether, ester, sulfonamide and azido groups. Primary alcohols under these conditions afford carboxylic acids (Scheme 3.50), while the oxidation of various secondary alcohols under similar conditions affords the appropriate ketones in almost quantitative yield [136]. 

Aryl-substituted aldehydes 352 can be cleaved to chain-shortened carbonyl compounds 353 and formaldehyde by iodosylbenzene in the presence of acids or Lewis acids (Scheme 3.140). Formaldehyde is further oxidized to CO and CO2 under the reaction conditions [457]. Oxidative decarboxylation of 2-aryl-substituted carboxylic acids 354 into corresponding aldehydes, ketones (e.g., 355) and nitriles at room temperature can be achieved by treatment with (diacetoxyiodo)benzene and a catalytic amount of sodium azide in acetonitrile (Scheme 3.141) [458]. 

Cyclic phenylselenated products are obtained when this reaction is applied to alkenes containing hydroxy, benzamido, enolizable ketones and carboxylic acids as remote functional groups. For example, the alkenol derivative 542 reacts with diphenyl diselenide and (diacetoxyiodo)benzene in acetonitrile to furnish C-glycoside 543 in moderate yield (Scheme 3.215) [603]. 

In 2005 Ochiai and coworkers reported the first iodobenzene-catalyzed reaction, a catalytic variant of a-acetoxylation of ketones based on the in situ generation of (diacetoxyiodo)benzene from iodobenzene using m-chloroperoxybenzoic acid (mCPBA) as a terminal oxidant [3]. In a typical example, the oxidation of a ketone with mCPBA (2 equiv) in acetic acid in the presence of a catalytic amount of iodobenzene (0.1 equiv), BF3 -OEt2 (3 equiv) and water (5 equiv) at room temperature under argon affords the respective a-acetoxy-ketone 1 in a moderate yield (Scheme 4.1). 4-Iodotoluene and 4-chloroiodobenzene can also serve as catalysts in the a-acetoxylation of ketones under these reaction conditions however, the use of iodobenzene results in the highest yields [3]. The use of at least 10 mol% iodobenzene in this reaction is necessary. When smaller amounts are used, the reaction slows and Baeyer-Villiger oxidation products resulting from a direct reaction of mCPBA and the ketone are observed [3],... 

The reactivity pattern of recyclable hypervalent iodine reagents 65-67,69-71,73,74 and 76 is similar to the common iodobenzene-based reagents [34], For example, the recyclable (diacetoxyiodo)arenes 65,69,73 and 76 can be used instead of (diacetoxyiodo)benzene in the KBr or TEMPO-catalyzed oxidations of alcohols [74-78], while [hydroxy(tosyloxy)iodo]arenes 67, 71 and 74 are excellent reagents for tosyloxylation of ketones (Scheme 5.28) [76]. 

Charette and coworkers have developed tetraarylphosphonium (TAP)-supported (diacetoxyiodo)benzene 109 (Figure 5.5), which can be used as a recyclable reagent or a catalyst for the a-acetoxylation of ketones [101]. Similarly to the imidazolium-supported [bis(acyloxy)iodo]arene 99, the reduced form of the TAP-supported reagent 109 can be recovered from the reaction mixture by simple filtration after treatment with ether. 

A series of unsaturated compounds 49, including a,p-unsaturated ketones, cinnamates, cinnamides and styrenes, have been aminobrominated to give products 50 with good yields and excellent diastereoselectivities under mechanical milling conditions, using TSNH2 and A-bromosuccinimide (NBS) as the nitrogen and bromine sources, promoted by (diacetoxyiodo)benzene (Scheme 6.19) [64],... 

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