Koser’s reagent

The best known member among the various classes of these iodanes is undoubtedly [hydroxy(tosyloxy)iodo]benzene (HTIB), sometimes called Koser s reagent. It is prepared readily from (diacetoxyiodo)benzene and p-toluenesul-fonic acid monohydrate in acetonitrile. The same method using p-nitroben-zenesulfonic acid or 10-camphorsulfonic acid leads to the corresponding sul-fonyloxy analogs [41,42]. Of special interest are some iodanes of this type coming from a chiral ether. Their preparation was effected by direct oxidation with sodium perborate and the isolated diacetoxy derivatives were separately treated with p-toluenesulfonic acid in acetonitrile (Scheme 8) [43]. 

Flavanones - Isoflavones. Although Koser s reagent (1) is known to effect a-tosyloxylation of ketones,1 the reaction with flavanones (2) results in an oxidative 1,2-aryl shift to provide isoflavones (3) in 74-80% yield.2 This conversion has been effected previously with thallium salts. 

A catalytic amount of acid is sufficient, on the other hand, for the halogenation of activated aromatics such as polyalkylbenzenes by all the three NXSs. NIS iodinates mesitylene in presence of the very mild acid hydroxy(tosyloxy)iodobenzene (Koser s reagent, HTIB)7 2. NBS performs much better in the presence of / -toluenesulfonic acid and NCS shows the highest yields when trifluoromethanesulfonic acid is used as catalyst743. This difference in reactivity leads to a novel method for preparation of a mixed halogenated mesitylene (equation 100). 

Hydroxy(tosyloxy)iodo]benzene, Koser s Reagent... 

Sin arly the a-mesyloxy esters are available by reaction with Koser s reagent. " Neither of these studies addressed the question of stereoselectivity. 

Phenyliodo bis(trifluoroacetate) Phenyliodine(lll) bis(trifluoroacetate) [ H y d roxy(to Isy loxy) iodo] benzene Koser s reagent lodosobenzene... 

The first preparation of [hydroxy(tosyloxy)iodo]benzene (HTIB) from (diacetoxyiodo)benzene and p-toluenesulfonic acid monohydrate was reported in 1970 by Neilands and Karele [196]. A decade later, Koser and coworkers discovered that HTIB is an efficient reagent for the oxytosylation of unsaturated organic substrates and for the synthesis of various iodonium salts [197-201] consequently, in modern synthetic literature HllB is often referred for as Koser s reagent . 

Of particular use is the reaction of [hydroxy(tosyloxy)iodo]benzene (HUB, also known as Koser s reagent) with ketones leading to a-tosyloxyketones [185-187], This is a highly chemoselective reaction different functional groups, aromatic rings and carbon-carbon double bonds are well tolerated under the reaction conditions [188], Scheme 3.59 shows a representative example of synthetic application of HUB for the functionalization of the azabicyclic alkaloid anatoxin-a, which is one of the most potent nicotinic antagonists. Specifically, the reaction of A-Boc anatoxin-a 140 with HTIB is the method of choice for the preparation of the synthetically versatile a-tosyloxy ketone 141 (Scheme 3.59) [189],... 

Hydroxy(tosyloxy)iodobenzene [phenyl(hydroxyl)to yloxyiodine, hydroxy(4-methylbenzene ulfonato-O)phenyliodine, Koser s reagent] [27126-76-7] M 392.2, m 134-136°, 135-138 , 134-136 , 136-138.5 . 

Consider the following transformation of acetophenone with hydroxy(tosyloxy)iodo-benzene (HTIB), also known as Koser s reagent ... 

Poly [4-(hydroxy)(tosyloxy)iodo]styrene, a polymeric version of Koser s reagent, has been reported to effect halotosyloxylation of alkynes with iodine or NBS or NCS, as shown below. The advantage of the polymeric reagent is that it can be readily separated from the product, regenerated, and reused. 

Related Reagents. Copper(II) Methanesulfonate Copper(II) Nitrobenzenesulfonate Thallium(III) Toluenesulfonate. Indirect a-Sulfonyloxylation has been achieved using Koser s reagent and related derivatives p-Nitrobenzenesulfonyl Peroxide other related reagents. ... 

Alternate Names HTIB Koser s reagent phenyllodine(III) (hydroxyl)tosylate. 

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