163. P. Müller, C. Boléa,
     “The Enantioselectivity and the Stereochemical Course of Copper-Catalyzed Intramolecular CH Insertions of Phenyliodonium Ylides”
     Helv. Chim. Acta 2002, 85, 483-494.

The Cu-catalyzed intramolecular CH insertion of phenyliodonium ylide 1b was investigated at 0° in the presence of several chiral ligands. Enantioselectivities varied in the range 38-72%, and were higher than those resulting from reaction of the diazo compound 1c at 65°. The intramolecular insertion of the enantiomerically pure methyl diazoacetate (R)-20 and of the corresponding phenyliodonium ylide (R)-21 proceeded to (R)-23 with retention of configuration with [Cu(hfa)₂] (hfa=hexafluoroacetylacetone=1,1,1,5,5,5-hexafluoropentane-2,4-dione) and [Rh₂(OAc)₄]. These results are consistent with a carbenoid mechanism for the Cu-catalyzed insertion with phenyliodonium ylides. However, the insertion of the perfluorosulfonated phenyliodonium ylide (R)-29 afforded with [Cu(hfa)₂] as well as with [Rh₂(OAc)₄] the cyclopentanone derivative 30 as a cis/trans mixture with only 56-67% enantiomeric excess.

DOI : 10.1002/1522-2675(200202)85:2<483::AID-HLCA483>3.0.CO;2-Q 

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