157. [CpRu]-Catalyzed Carbene Insertions into Epoxides: 1,4-Dioxene Synthesis through S_N1-Like Chemistry with Retention of Configuration
     Thierry Achard, Cecilia Tortoreto, Amalia I. Poblador-Bahamonde, Laure Guénée, Thomas Bürgi, Jérôme Lacour
     Angew. Chem. Int. Ed. 2014, 53, 6140-6144
     [ This article was highlighted as a SynStory in Synform, 2014/10 (DOI: 10.1055/s-0034-1379040) ]

Rather than lead to the usual deoxygenation pathway, metal carbenes derived from α-diazo-β-ketoesters undergo three-atom insertions into epoxides using a combination of 1,10-phenanthroline and [CpRu(CH₃CN)₃][BAr_F] as the catalyst. Original 1,4-dioxene motifs are obtained as single regio- and stereoisomers. A perfect syn stereochemistry (retention, e.r. up to 97:3) is observed for the ring opening, which behaves as an S_N1-like transformation.

DOI : 10.1002/anie.201402994 

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