Cyclic Diacylcarbene Generated from Iodonium Ylides and Diazodiketones

Abstract

The preparative method of iodonium ylides, Ph–\overset⊕I–\overset\ominusC(COR)(COR′), is improved by condensation of active methylene compounds, H2C(COR)(COR′), with iodosobenzene in the presence of acetic anhydride. Thermal and Cu-catalyzed decomposition of iodonium ylides can be differentiated and both are explained in terms of diacylcarbene intermediate with different multiplicity. For the sake of comparison diazodimedone and related compounds are also decomposed by Cu-catalysis as well as by photochemical reaction. Carbene is also found to be a highly probable intermediate. Throughout these investigations the spin multiplicity of the carbene is discussed on the basis of product distributions. Notably in the presence of homogeneous Cu-catalyst in ethanol, diazodimedone gives an insertion product to O–H bond, 2-ethoxy-3-hydroxy-5,5-dimethyl-2-cyclohexenone (XVII), whereas the iodonium ylides do not give such a compound. The formation of XVII is explained by assuming a ketocarbene-Cu-chelate complex.

Carbene Complexes of Nonmetals

“…Ylides derived from aryl iodides done (42, 10%) and its ethyl ether (43, 32%). [29] The latter products arise by hydrogen transfer from the solvent. Reduction prevailed in the thermolysis of ylide 44 in ethanol (Ǟ 45, 40%), but the ester 46 (17%) was also formed.…”

“…Reduction prevailed in the thermolysis of ylide 44 in ethanol (Ǟ 45, 40%), but the ester 46 (17%) was also formed. [29] The Wolff rearrangement, 44 Ǟ 46, points to intervention of a carbonylcarbene.…”

A relationship between the catalytic carbonylation of (N-arenesulfonyl)imides and iodonium ylides

“…[(N-arenesulfonyl)imino]phenyliodinanes and phenyliodonium methylides of general formulas ArSO 2 N=IPh and E 1 E 2 C=IPh (E represents electron-withdrawing groups like RC(O), RSO 2 , R F SO 2 ), respectively, have been mentioned as nitrogen and carbon analogues of iodosylbenzene (PhIO) and have been postulated as sources of arylsulfonylnitrene (16) and diacylcarbene species (17). Considerations regarding the structural properties of iodonium ylides (18) and available crystallographic data for them (19) have turned our attention toward the structural similarities of 2a and iodonium ylides and have made the latter promising candidates as substrates for two-step oxidative carbonylations.…”

Chiral Dirhodium Catalysts: A New Era for Asymmetric Catalysis

“…Often, their decomposition occurs at temperatures well below those required for diazo decomposition. The main potential for phenyliodonium ylids is not only for their photochemical, [111,112] thermal [113], and transition metal-catalysed decompositions [113,114] and higher reactivity versus diazo compounds, but also because of the possibility to carry out carbene transfer in a one-pot procedure in which the phenyliodonium ylide is generated. Also, the decomposition in situ in the presence of a transition metal catalyst and accordingly, carbene or carbenoid intermediates are usually assumed to be involved in these reactions [51,109,[115][116][117][118][119].…”