Benziodazoles

Acetoxybenziodazole 150 (as a solvate with acetic acid) has the expected distorted T-shaped geometry at the iodine atom with an N—I—O bond angle of 162.1°. Bond lengths to the iodine center [I—N (2.101 A), I—O (2.34 A), and I—C (2.106 A)] are aU within the range of typical single covalent bonds in organic derivatives of polyvalent iodine and are in good 

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Normally, iodanes with one or two azido groups attached to iodine(III) are very labile. Two cyclic iodanes, however, l-azido-l,2-benziodazol-3(lH)-one and its 2-acetoxy derivative, are stable. They are prepared from the corresponding 1-acetoxybenziodazoles by reaction with trimethylsilyl azide (Scheme 25) [76,77]. 

This category includes several heterocyclic iodanes coming mainly from benziodazoles or benziodoxoles or a combination of both. Among them, 1-hydroxy-l,2-benziodazole and its derivatives are of considerable interest. It is noted that the first iodane of this type, prepared in 1965 by peracetic acid oxidation of o-iodobenzamide, is not N- (as originally proposed) but O-acetyl (Scheme 26) [77]. 

This benziodazole reacts not only with Me3SiN3, as already mentioned, but also with p-toluenesulfonic acid hydrate or methanesulfonic acid in acetic anhy-... 

Structure of benziodazoles (4) was determined by diffraction studies to be tricoordinate about the iodine atom <75J0C2129,79JOCl447>. 

Quideau and coworkers presented DFT calculations of spiroheterocylic iodine(III) intermediates to validate their participation in the PhI(OAc)2-mediated spiroketalization of phenolic alcohols [206]. Molecular orbital computational studies of (arylsulfonylimino)iodoarenes (ArINS02Ar ) [185], benziodazol-3-ones [207] and a series of or//to-substituted chiral organoiodine(III) compounds [208] have been reported in the literature. Results of these calculations were found to be in good agreement with X-ray structural data for these compounds. 

The first preparation of a benziodazole heterocyclic system was reported by Wolf and Steinberg in 1965 [236]. The authors of this paper isolated the product of peracetic oxidation of 2-iodobenzatnide (163) and, based on the IR spectroscopy, incorrectly assigned the structure of 77-acetyl-l-hydroxy-3-(l//)-l,2-benziodazole-3-one 165 to this product. Structure 165 was also adopted in several other studies [259,328,329]. More recently, the product of peracetic oxidation of 163 (Scheme 2.54) was investigated by a single-crystal X-ray analysis, which revealed its actual structure of acetoxybenziodazole 164, which is different from the previously adopted 165 [266],... 

The synthesis and structural studies of several N-functionalized benziodazoles derived from natural amino acids have been reported [265]. Acetoxybenziodazoles 170 and 171 were prepared by the peracetic oxidation... 

The oxidation of iV-(2-iodobenzoyl) amino acids 176 with dimethyldioxirane affords chiral and optically purehypervalent iodine macrocycles 178-181 as the final isolated products [241]. It is assumed that the initial products in this reaction are the monomeric amino acid derived benziodazoles 177, subsequent self-assembly of which affords the final products 178-181 (Scheme 2.57). This self-assembly is directed by secondary bonding between hypervalent iodine and oxygen atoms of the amino acid fragment [241]. 

PhI(OAc)2. As a result of the central oxygens, the electron-rich cavity of macrocycle 180 is suitable for complexation of metal cations. Specifically, ESI-MS data indicate that macrocycles 178-181 can selectively form complexes with sodium cations in the presence of K+, Li+, Ag+, or Pb + [241], The self-assembly of monomeric benziodazoles 177 into macrocyclic molecules 178-181 was studied using molecular orbital calculations [331]. The driving force for the self-assembly is the formation of secondary bonding interactions between molecules and a rearrangement of primary and secondary bonding around iodine to place the least electronegative substituent in the equatorial position for each iodine in the trimer. 

Reactions of chiral A, -iodanes, amino acid-derived benziodazole oxides 58 [76], (5)-proline based reagents 59 [77], and iodylarenes 60 bearing ester motives [78] with non-symmetric sulfides to give asymmetric sulfoxide formation further recognized the importance of such transformations. 

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