Diacetoxy iodobenzene

Partially or fully reduced thiadiazoles can be oxidized to yield 1,3,4-thiadiazoles. The 2,5-disubstituted 3-acyl-l,3,4-thiadiazole 157 can be deacylated by numerous methods <2004H(63)2243>. The oxidative deacylation of compound 157 to thiadiazole 158 can be achieved using oxidants such as KMn04, cerium(iv) ammonium nitrate (CAN), and (diacetoxy)iodobenzene (Equation 58). Better yields and cleaner products are obtained using CAN as oxidant. 

Bis(acyloxy)iodo]arenes 1 can serve as precursors to alkyl radicals 2 via decarboxylative radical decomposition initiated by irradiation with a mercury lamp (Hg-hv) or heating (Scheme 1) [3]. Generated under these conditions alkyl radicals 2 can be effectively trapped with the appropriate organic substrates affording products with a new C-C bond. The starting [bis(acyloxy)iodo]arenes 1 can be prepared in situ from the readily available [bis(trifluoroacetoxy)iodo]ben-zene or (diacetoxy)iodobenzene and a carboxylic acid. 

In a convenient experimental procedure, nitrogen heterocycles 3 are alkylated by a mixture of a carboxylic acid 4 and [bis(trifluoroacetoxy)iodo]benzene in boiling benzene or under irradiation in dichloromethane at room temperature (Scheme 2) [11, 12]. A similar procedure has been used for the stereoselective synthesis of C-nucleosides and their analogs via photolysis of the gulonic acid derivatives, (diacetoxy)iodobenzene, and the appropriate heteroaromatic bases [13]. 

Palladium-catalysed directed C-H oxidation with (diacetoxy)iodobenzene of a series of meta -substituted aryl pyridine and aryl amide derivatives resulted in the formation of the corresponding acetoxy compounds. The reactions generally proceed with high levels of regioselectivity for functionalization of the less sterically hindered ortho-C-H bond.144 The mechanism shown in Scheme 4 has been proposed for the oxidation of 2,6-dimethylphenol with (diacetoxyiodo)benzene for the formation of 3,5,3, 5 -tetramethyl-biphenyl-4,4 -diol, via C-C coupling.145... 

The one-pot three-component reaction of polyethylene glycol-supported acrylate 623 with aldehydes 621 and hydrazines 622 in the presence of chloramine-T followed by methanolysis afforded pyrazolines 624 in good yields and high purities (Scheme 77) <2003SL1467>. 1,3-Dipolar cycloaddition of resin-supported acrylic acid 625 with the nitrilimines generated in situ by oxidation of the aldehyde phenylhydrazones with (diacetoxy)iodobenzene under microwave irradiation gave 626, which was converted into l-phenyl-3-substituted-2-pyrazolinyl-5-carboxylates 627 (Scheme 78) <2004SC3521>. 

Thioacetal 418 can easily be prepared on a large scale from D-lyxose via intermediate 416, which is oxidized into 417 by the diacetoxy-iodobenzene/l2 system [156]. Treatment of 417 with thiophenol and BF3 -OEt2 affords 418 after methanolysis of the formate group. 

Some polyfunctional isoxazolines of generic structure 44 were obtained in 78-91% yields by treatment of aryl aldoximes 42 with Baylis-Hillman adducts 43 in the presence of diacetoxy iodobenzene (DIB). The reaction is completely diastereoselective and involves the formation of nitrile oxides from aldoximes followed by 1,3-DC with the activated alkenes. Under the same conditions, ketoximes afforded only deoximation products <04TL7347>. 

A new oxidation reagent for the synthesis of diazoalkanes from hydrazones is /,/-diacetoxy-iodobenzene (phenyliodosoacetate) it was used by Smith s group (Bedford et al., 1981) for the formation of 5-(diazomethyl)-l,4-diphenyl-l,2,3-triazole from the hydrazone of l,4-diphenyl-l,2,3-triazole-5-carbaldehyde in cyclohexylamine and CH2CI2 at -40°C (2-31). 

Using 0.2 equiv. of palladium(II) acetate and (diacetoxy)iodobenzene as cooxidant, Gaunt et al. achieved an oxidative cyclization of A(-alkylbiphenyl-2-amines including C-H activation at the 2 -position to give A(-alkylcarbazoles [195]. The potential of this method was demonstrated by the synthesis of an M-glycosylcarbazole. 

The iodoniumylides 17 were obtained from diverse diones 16 and (diacetoxy)iodobenzene. 

The ylide was prepared by reaction of ethyl (nonafluorobutyl-sulfonyl)acetate with diacetoxy iodobenzene. Subsequent reaction with alkenes in presence of Cu(OTf)2 afforded the y-lactones. 

Aminobiphenyls 6, (a) N-substituted with acyl or sulfonyl groups [201] and (b) N-substituted with alkyl or benzyl groups [202], undergo oxidative cycUzation to carbazoles 7, in (a) with O2 catalyzed by Pd(II) or Cu(II), in (b) with (diacetoxy)iodobenzene catalyzed by Pd(II) ... 

SCHEME 2 One-pot synthesis of 2,3,4-trisubstituted pyrroles using DIB. DIB, (diacetoxy)iodobenzene. 

SCHEME 28 Synthesis of indoloquinolinones. DIB, (diacetoxy)iodobenzene DCE, dichloroethane DMF, dimethylformainide. 

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