Dicarbonyl compounds Iodosylbenzene

Iodonium ylides of type 6 cannot be isolated, unless the carbanion center is substantially stabilized (83MI1, 92MI1, 97MI1, 02MI1). For example, although iodonium enolates 22 can be prepared by base-catalyzed condensations of DAIB or iodosylbenzene with /J-dicarbonyl compounds, they are not similarly available from unactivated ketones and esters. Indeed, cyclic and acyclic mono-ketones are converted to a-hydroxy dimethylketals 23 with DAIB (or 13) in KOH/MeOH (86ACR244, 99QR273). Other... 

Closely related reactions are the self-coupling of P-dicarbonyl compounds upon treatment either with iodosylbenzene in the presence of boron trifluoride-diethyl ether in neutral solvents,234 or with iodobenzene diacetate in acetic acid. 235... 

The reaction of 1,3-dicarbonyl compounds with iodosylbenzene, hydroxy(tosyloxy)iodobenzene or hydroxy(mesyloxy)iodobenzene, gave similar results to those obtained with monocarbonyl compounds. However, only the 2-functionalised derivatives were obtained.234,249,266 Excellent results were observed in the case of substrates containing a perfluoroalkyl chain. Treatment of the fluoro dicarbonyl compounds (158) with HTIB afforded the a-tosyloxy compounds (159) which were isolated as their dihydrate. 

Treatment of (3-dicarbonyl compounds 461 with iodosylbenzene/TMSN3 in chloroform at reflux affords azides 462 in moderate to good yield (Scheme 3.183) [551]. Under similar conditions, 2-(trimethylsiloxy)furan (463) gives azidofuranone 464 as the main product [552]. 

---