Azidations. using hypervalent iodine reagents

In addition, this type of aromatic ring activation by the SET oxidation strategy using hypervalent iodine reagents was utilized for the total synthesis of a sulfur-containing pyrroloiminoquinone alkaloid, ( )-makaluvamine F [119-121]. The reaction for the construction of the a-amino dihydrobenzothiophene part involved the efficient cyclization of the benzyl thioether. Hypervalent iodine reagent was iteratively utihzed for the successive oxidative transformation, that is, the azidation at the a-position of the sulfur group of the dihydrobenzothiophene via a Pummerer-like mechanism (Scheme 24). 

Recent progress on the use of hypervalent iodine reagents for the construction of carbon-het-eroatom (N, O, P, S, Se, Te, X) bonds is reviewed. Reactions of aryl-A3-iodanes with organic substrates are considered first and are loosely organized by functional group, separate sections being devoted to carbon-azide and carbon-fluorine bond formation. Arylations and alkenyla-tions of nucleophilic species with diaryliodonium and alkenyl(aryl)iodonium salts, and a variety of transformations of alkynyl(aryl)iodonium salts with heteroatom nucleophiles are then detailed. Finally, the use of sulfonyliminoiodanes as aziridination and amidation reagents, and reactions of iodonium enolates formally derived from monoketones are summarized. 

DIB and some other hypervalent iodine reagents have been used in combination with sodium or trimethylsilyl azide to bring about interesting transformations in various types of reactants, involving either unstable iodine (III) species or the generation of free radicals. For the sake of a uniform presentation, all relevant results are discussed here together. 

A simple method for the preparation of a-azido ketones and esters 500 in good yields by direct azidation of carbonyl derivatives 499 at the a-carbon using 4,4 -bis-(dichloroiodo)biphenyl and sodium azide has been reported (Scheme 3.198) [575]. The hypervalent iodine reagent, 4,4 -bis-(dichloroiodo)biphenyl, can be easily recycled from the reaction mixture. 

Chen DJ, Chen ZC (2000) Hypervalent iodine in synthesis. Part 54 one-step conversion of aryl aldehydes to aroyl azides using a combined reagent of (diacetoxyiodo)benzene with sodium azide. Tetrahedron Lett 41(38) 7361-7363... 

Tohma H, Egi M, Ohtsubo M, Watanabe H, Takizawa S, Kita Y (1998) A novel and direct a-azidation of cyclic sulfides using a hypervalent iodine(lll) reagent. Chem Commun 173-174... 

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