[2712-78-9] · C10H5F6IO4 · Phenyliodine(III) Bis(trifluoroacetate) · (MW 430.05)
(cyclopropyl groups undergo ring opening,2 alkynes are cleaved,3 phenols are oxidized to quinones4-8 and in some cases oxidative intramolecular coupling occurs,9-13 ketones yield a-hydroxy ketones,14 certain b-diketones undergo cyclization,15 Pummerer-type reaction occurs,16 and deprotective dethioacetalization is an important use17)
Alternate Names: bis(trifluoroacetoxyiodo)benzene; iodobenzene bis(trifluoroacetate); PIFA; BTI.
Physical Data: mp 121-125 °C.
Solubility: sol CH2Cl2, CCl4, CF3CH2OH, (CF3)2CHOH.
Form Supplied in: white solid; commercially available.
Preparative Method: can be synthesized by reaction of (Diacetoxyiodo)benzene with Trifluoroacetic Acid.18
Handling, Storage, and Precautions: moisture sensitive; irritant.
1,3-Dehydroadamantane underwent ring-opening with 1,3-addition of CF3CO2- upon reaction with PhI(OCOCF3)2 (BTI) (eq 1).2 Alkynes are cleaved upon treatment with three equivalents of BTI.3 Dibenzyl ether is cleaved to benzaldehyde and benzyl trifluoroacetate (eq 2). Benzylalkyl (or trityl and benzhydryl) ethers react analogously.19
Hydroquinones and catechol derivatives are oxidized to o- or p-benzoquinones (eq 3).4-7 In the presence of water, a quinone is formed, while in the presence of methanol the quinone monoacetal is formed (eq 4).8
Intramolecular oxidative cyclization is also an important reaction pathway, as in the case of N-acetyltyramines (eq 5),9 and it has been applied in the syntheses of several natural products. For example, phenolic oxidative coupling with BTI was a key step in the synthesis of 6a-epipretazettine (eq 6).10
A similar intramolecular spirodienone formation was observed in a naphthoquinone system (eq 7).11 An extension of this type of oxidative coupling formed the key step in the synthesis of the marine alkaloid discorhabdin C (eq 8).12 Intramolecular cyclization has also been used as a key step in a synthetic approach to the natural product aranorosin (eq 9).13
Table 1 illustrates the oxidative cyclization and gives a useful comparison of yields as a function of reagent, solvent, and temperature. All hypervalent iodine oxidations were carried out in acetonitrile or acetonitrile-pyridine (yields in parentheses) at 0 °C.13
BTI and trifluoroacetic acid in MeCN/H2O react with aromatic, heteroaromatic, and aliphatic ketones to afford a-hydroxy ketones in moderate to good yields (eq 10).14 b-Dicarbonyl compounds with a-aralkyl systems can undergo cyclization (eq 11).15
N-[(2-Methylthio)acetyl]-N-phenylaniline upon reaction with BTI undergoes Pummerer-type cyclization to yield 3-methylthio-N-phenylindol-2(3H)-one. This process appears to be a general method of cyclization for appropriate methylthio derivatives (eqs 12-15).16
BTI is the reagent of choice for dethioacetalization (eq 16).17 Functional groups, R, such as esters, nitriles, secondary amides, alcohols, halides, alkenes and alkynes, thioesters, and amines are unaffected in this process.
Robert M. Moriarty & Jerome W. Kosmeder II
University of Illinois at Chicago, IL, USA