Hydroxyl iodo benzene

With a-hydroxy ketones and their related tosyloxy derivatives. The imidazo [2,T ]thiazole 364 was prepared by acetic acid-catalyzed cyclocondensation of 2-hydroxy-l,2-diphenyl-ethanone with thiophenyl-substituted 2-aminothiazole 363 (Equation 163) <2002MI110>. Under MW irradiation and in the presence of montmorillonite K-10 clay, a mixture of a-tosyloxyketones 365 and 2-imidazolidinethione led to the substituted 5,6-dihydro-imidazo[2,l- ]thiazoles 366 (Equation 164) <1998J(P1)4093>. When using a-tosyloxyacetophenone, prepared by reaction of acetophenone with [hydroxyl(tosyloxy)iodo]benzene (HTIB), 5-aminopyrazole 367 could be converted to imidazo[l,2- ]pyrazole 368 in basic medium (Equation 165) <2005JHC209>. 

Oxidative C-H amination has been an area of intensive research since the publication of CHEC-II(1996). This methodology has been applied to the synthesis of a variety of 1,2-thiazine 1,1-dioxides. In the simple cases, substrates containing an aromatic C-H can be cyclized in the presence of hypervalent iodine. For instance, the reaction of A-methoxy(2-arylethane)sulfonamide 202 with [hydroxyl(tosyloxy)iodo]benzene rapidly affords benzenesulfon-amide 203 in excellent yield (Equation 30) <20030BC1342> see also <2000JOC926> and <2000JOC8391>. 

Hydroxylated 1,4-benzoquinones and 1,4-naphthoquinones gave similarly the corresponding dipoles [164]. The amino analogs reacted in the same way to afford first isolable iodonium salts and then the imino dipoles (Scheme 54) [165]. It is noted that the open-chain methyl 2-aminocrotonate gave with [hydroxy(tosyloxy)iodo]benzene only the iodonium salt, i.e. -MeC(NH2) = C(COOMe)I+Ph TsO- [166]. 

Oxidation Using [Hydroxyl(tosyloxy)iodo]benzene (HTIB)... 

A similar hydroxylation of aromatic, heteroaromatic and aliphatic ketones can also be performed using [bis(trifluoroacetoxy)iodo]benzene imder acidic conditions (Scheme 3.57) [183]. A plausible mechanism for this hydroxylation involves initial electrophilic addition of PhI(OCOCF3)2 to the enolized ketone and subsequent nucleophilic substitution in the iodonium intermediate. 

The proposed catalytic cycle for this reaction includes initial formation of [hydroxyl(tosyloxy)iodo]benzene 37 by oxidation of iodobenzene in the presence of toluenesulfonic acid followed by its conversion into the bromoiodane 38 via ligand exchange and then the bromination of arene to form the aryl bromide (Scheme 4.19). The reduced by-product, iodobenzene, is again transformed into the hypervalent iodine reagent by oxidation with mCPBA [46]. 

A one-pot procedure for the a-tosyloxylation of ketones by the reaction of ketones with mCPBA and TsOH H2O in the presence of catalytic amounts of NH4I and benzene in a mixture of MeCN and trifluo-roethanol (8 2) has been reported (Scheme 4.67) [110]. This method has some advantages, such as mild reaction conditions with a simple procedure and it is suitable for preparing not only a-tosyloxy ketones but also other a-sulfonyloxy ketones. It has been suggested that [hydroxyl(tosyloxy)iodo]benzene, generated by the reaction of iodide anion with mCPBA, benzene and TsOH, serves as the active species in this reaction [110]. 

The oxidation of a ( )-flavanone with Tl(ni) nitrate, Pb tetracetate, phenyliodonium diacetate (PIDA), or [hydroxyl(tosyloxy)iodo]benzene in trimethyl orthofonnate affords the corresponding ( )-2,3-dihydrobenzo[h]furan derivative as a major product. The structures, including the relative stereochemistry, and a plausible mechanism of formation are reported. The preferred formation of a flavone from the ( )-flavanone by PIDA is explained by quantum-chemical calculations on the intermediate formed by the addition of this reagent to the enol ether derivative of the ( )-flavanone." Formation of mixed anhydrides by rapid oxidation of aldehydes, activated by pivalic acid, Bu OCl in presence of pyridine and MeCN is catalysed by TEMPO (2,2,6,6-tetramethylpiperidin-l-oxyl). The anhydrides can be converted in situ to esters, secondary, tertiary or Weinreb amides in high yield. Oxidation of the aldehyde to 2-propyl esters is also possible using only catalytic amounts of pivalic acid." ... 

Substituents that are otherwise accessible only with difficulty, such as fluoro, iodo, cyano, and hydroxyl, may be introduced onto a benzene ring. 

Selective replacement of primary hydroxyl groups in carbohydrates by iodine atoms has been achieved by using the Rydon reagent, namely, methyltriphenoxyphosphonium iodide.368 Treatment of methyl 3,4-O-isopropylidene-jS-D-galactopyranoside with the phosphonium salt in benzene for 48 hours at room temperature yielded 60% of the 6-deoxy-6-iodo derivative,369 and reaction of thymidine, uridine, and 2,2 -anhydrouridine in N,N-dimethylformamide afforded 5 -deoxy-5 -iodo derivatives in yields of 63, 65, and 31%, respectively.370... 

DMF, 1 atm. H2, 3 h) , and 1 1 ( H2, Pd/CaCOa, benzene r.t., 1 h) (Figure 4.44). Alternatively, for allylic alcohol derivatives steric blocking of the hydroxy group can be used to slow the reduction of the double bond. Thus with 152, the olefinic bond was reduced in competition with the aryl iodo substituent ( H2,10% Pd/C, Et20 or EtOH, 11-13 equiv. EtaN) even at short reaction times, but in 153 it was reduced only to the extent of 3% or less in reactions of 3 h duration, regardless of the substitution at the phenolic hydroxyl ". ... 

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