Iodonium ylides complexes

A similar reaction of ylide 200 can also be carried out under thermal conditions or in the presence of catalytic amounts of Cu(acac)2 [143]. The carbenoid reactions of iodonium ylides can also be effectively catalyzed by rhodium(II) complexes [144, 145]. The product composition in the rhodium(II) catalyzed reactions of iodonium ylides was found to be identical to that of the corresponding diazo compounds, which indicates that the mechanism of both processes is similar and involves metallocarbenes as key intermediates as it has been unequivocally established for the diazo decomposition [144]. 

The tandem ylide generation/[2,3]-sigmatropic rearrangement can also be performed with sulfur and iodonium ylides and in these cases the reaction can proceed in intermolecular fashion.For example, up to 78% ee has been obtained in the reaction of allyl-2-methylphenyl sulfide (9.129) with aryl diazoacetates such as (9.130) in the presence of the copper catalyst generated with bis-oxazoline (9.07), while the reaction of aUyl iodide (9.132) with ethyl diazoacetate yields product (9.133) with 69% ee using this complex. ... 

Bis(methoxycarbonyl)(phenyliodinio)methanide (778), the most common iodonium ylide derived from malonate methyl ester, has found synthetic applications in the C—H insertion reactions [1044-1048] and the cyclopropanation of alkenes [1049-1055], including enantioselective cyclopropanations in the presence of chiral rhodium complexes [1056-1058], Representative examples of these reactions are shown in Scheme 3.306 and include the BFs-catalyzed bis(carbonyl)alkylation of 2-alkylthiophenes 777 [1045] and the optimized procedure for rhodium-catalyzed cyclopropanation of styrene 779 [1052]. 

Metallocarbene precursors other than diazocarbonyls have been examined sporadically for the generation of oxonium ylides, though not in the context of complex target synthesis. Among these, iodonium ylides and oxidative activation of allqnies in the presence of gold catalysts have shown significant promise. 

The rhodium complex also catalyzed the cyclopropanation of iodonium ylides 159 that was prepared from malonic esters (Scheme 1.75) [120]. The treatment of a malonic ester with phenyhodonium diacetate gave corresponding iodonium ylides, which underwent smooth cyclopropanation with various alkenes. It was shown that these two steps... 

Interest in the synthesis and reactivity of the six-membered, potentially aromatic, phosphinine ring system has also continued, but at a much lower level than in recent years. New synthetic work includes the application of the pyrylium salt route to phosphinine synthesis, this time starting from pyrylium salts bearing chiral substituents to give the related chiral phosphinines," and the development of new routes to the 2-phosphanaphthalene (137)" ° and the phosphinine-2-aldehyde (138). Also reported is an approach to the synthesis of l,2-dihydro-l,4,2-benzo-diazaphosphinines," cationic gold(I) complexes of 2,4,6-tri-t-butyl-l,3,5-triphosphabenzene," and the synthesis of some X -phosphinines from phosphonium-iodonium ylides." " ... 

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