Hypervalent iodine

Keywords Benziodoxoles Hypervalency Hypervalent Hypervalent boron Hypervalent bromine Hypervalent heterocycles Hypervalent iodine Hypervalent silicon Hypervalent sulfur Iodine heterocycles... 

CF,C02)2lPh, H2O, CH3CN, 85-99% yield. In the presence of ethylene glycol the dithiane can be converted to a dioxolane (91% yield) or in the presence of methanol to the dimethyl acetal. The reaction conditions are not compatible with primary amides. Thioesters are not affected. A phenylthio ester is stable to these conditions, but amides are not. The hypervalent iodine derivative l-(t-butylperoxy)-l,2-benziodoxol-3(l/f)-one similarly cleaves thioketals."... 

Chemical transformations of heterocycles induced by hypervalent iodine reagents 97T1179. 

Synthesis of heterocyclic compounds using hypervalent iodine reagents 98AHC(69)1. 

Recently, the ring enlargement of 4-hydroxy-2-cyclobutenones 5 was promoted by PhI(OAc)2, a popular and accessible hypervalent iodine reagent (99JOC8995). Thus, when 5a-c (R = Me, Bu, Ph) were treated with a slight excess of PhlfOAcja in dichloromethane at room temperature, the 5-acetoxy-3,4-diethoxyfuranones 13... 

A similar approach was carried out reacting an enohzable ketone with amides in the presence of the hypervalent iodine(III) reagent (hydroxy(tosyl-oxy)iodobenzene, HDNIB) [48]. The reaction was carried out imder solvent-... 

Scheme 18 Solvent-free synthesis of oxazoles mediated by hypervalent iodine(III) sulfonates...

Haloalkynes (R—C=C—X) react with ArSnBu3 and Cul to give R—C= C—Ar. Acetylene reacts with two equivalents of iodobenzene, in the presence of a palladium catalyst and Cul, to give 1,2-diphenylethyne. 1-Trialkylsilyl alkynes react with 1-haloalkynes, in the presence of a CuCl catalyst, to give diynes and with aryl triflates to give 1-aryl alkynes. Alkynes couple with alkyl halides in the presence of Sml2/Sm. Alkynes react with hypervalent iodine compounds " and with reactive alkanes such as adamantane in the presence of AIBN. ... 

Under certain conditions, amides can add directly to alkenes to form N-alkylated amides. 3-Pentenamide was cyclized to 5-methyl-2-pyrrolidinone by treatment with trifluorosulfonic acid. Acylbydrazine derivatives also cyclized in the presence of hypervalent iodine reagents to give lactams. When a carbamate was treated with Bu3SnH, and AIBN, addition to an alkene led to a bicyclic lactam. 

The Dess-Martin reagent can be shock sensitive under some conditions and explode > 200°C. Other hypervalent iodine oxidizing reagents are known, including PhI(OAc)2/TEMPO and PhI(OAc)2 supported on alumina with microwave irradiation. 

The hypervalent iodine oxidation of (pyridylalkyl)trimethylsilanes to the corresponding alcohols and esters has been reported <96H(43)1151>. Oxidation of 2-(phenylethynyl)p5nidine with HjOj/AcOH followed by ROH/NajCOj provides 6-alkoxy-2-phenacylpyridines 42 via an intermediate iV-oxide <96H(43)1179>. 

Finally, phthalocyanine iron catalysts were also used for the oxidation of alcohols to yield corresponding carbonyl compounds with nonbenign hypervalent iodine oxidants [147]. 

Oxidation by the Dess-Martin Reagent. Another reagent that has become important for laboratory synthesis is known as the Dess-Martin reagent,28 which is a hypervalent iodine(V) compound.29 The reagent is used in inert solvents such as chloroform or acetonitrile and gives rapid oxidation of primary and secondary alcohols. The by-product, o-iodosobenzoic acid, can be extracted with base and recycled. 

In recent years, a variety of hypervalent iodine reagents have been available. The versatility of these hypervalent organoiodine reagents in organic synthesis has been well recognized. Diaryliodonium salts constitute an important reagent class for the transfer of aryl groups. These iodonium ion salts have been used effectively in C-arylation of a variety of nucleopohiles.112 The arylation of the anion of nitroalkanes with diaryliodonium salts was already reported in 1963.113... 

Varvoglis A (2003) Preparation of Hypervalent Iodine Compounds. 224 69-98 Verkade JG (2003) P(RNCH2CH2)3N Very Strong Non-ionic Bases Useful in Organic Synthesis. 223 1-44... 

Scott was able to leverage the same type of methodology in an impressive display in which /V-methyltryptamine was dimerized directly to afford chimonanthine (7) (Scheme 9.2b) [9c]. Deprotonation of the indole 1H proton with methyl Grignard followed by treatment with FeCl3 accomplished the singleelectron oxidation and dimerization of the indole moiety. The racemic and meso stereoisomeric products were obtained as a mixture in 19 % and 7 % yields, respectively. Takayama later found hypervalent iodine to be a superior oxidant, affording yields of 17 % and 30 %, respectively [9j]. In both cases, however, as in the case of Hendrickson s example, stereocontrol could not be achieved. 

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