Iodine-nitrogen ylides

REACTIVITY OF IODINE-NITROGEN YLIDES 10.3.1 Aziridination of alkanes and dienes... 

Phenyliodonium Zwitterions Preparation. Reactivity of Iodine-Carbon Ylides. Reactivity of Iodine-Nitrogen Ylides. Reactivity of 1,4-dipoles. 

DCCI reacts with hydrazone derivatives or with the thiourea 83 to give nitrogen ylides such as 84 and hence by protonation 3-aminotriazolopyridines (88CC506, 93JCS(P1)705). A solution of iodine in pyridine reacts with propional... 

Further examples of the functionalization of sulfur compounds with iodine(III)-nitrogen ylides include copper-catalyzed imidations of phenyl benzyl sulfide with [(sulfonylimino)iodo]benzenes possessing imidazole and pyridine rings in the sulfonyl moiety [34], and uncatalyzed tosylimidations of diaminothiocarboxylate inner salts 26 (Scheme 14) with Phi = NTs to give 27 [35]. 

Members of this family of zwitterions are iodine-oxygen or iodine-nitrogen 1,4-dipoles. Some of their reactions bear analogy to those of iodine-carbon ylides, whereas in some others there are differences. 

Ylide can be viewed as a special carbanion in which the negative charge on carbon is stabilized by an adjacent positively charged heteroatom. The most common ylides are phospho-nium ylides, sulfur ylides (sulfonium and sulfoxonium ylides) and certain nitrogen-based ylides (ammonium, azomethine, pyridinium and nitrile ylides). In addition to synthetically important phosphorus, sulfur and nitrogen, ylides of tin (Sn) and iodine (I) have been developed in recent years. 

The aza analogues of 417, iodine-nitrogen zwitterions 419, have been prepared by the reaction of 2-amino-1,4-naphthoquinone (418) with [hydroxy(tosyloxy)iodo]arenes (Scheme 2.122) [205,562,563]. Ylides 419 show interesting reactivity upon heating, aryl migration from iodine to nitrogen occurs, giving product 420,... 

For alkynyl transfer, no direct evidence has been presented to determine whether organometallic nucleophiles interact with the electrophilic iodine centre or the jS-carbon although, in the case of transfer to the nitrogen nucleophile of a coordinated cyano ligand, the S-interaction mechanism is clearly implicated in the formation of 68 (Scheme 38, related to the mechanism in Scheme 14). This example indicates, for the synthesis of alkynylmetal species, the attractiveness of RC=C(Ph)I reagents where the R group cannot participate in such reactivity, e.g. R = SiMcs, Ph. Alternatively, this type of reaction, where the metal centre may act as a nucleophile at the -carbon, is worthy of exploration as a mode of organometallic synthesis as also is electrophilic attack at the K-carbon of ylides (illustrated by the mechanism in Scheme 14). 

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