Chemoselectivity and stereoselectivity of cyclisation of α-diazocarbonyls leading to oxygen and sulfur heterocycles catalysed by chiral rhodium copper catalysts
Good levels of enantioselectivity have been achieved in intramiolecular C-H insertion reactions of α-diazocarbonyl compounds leading to six-membered oxygen heterocycles (chromanones) through the use of chiral rhodium(II) carboxylates as catalysts.Competition between C-H insertion and sigmatropic rearrangement, the latter leading to five-membered oxygen heterocycles (furanones), was observed with precursors containing a proximal O-allyl side chain.Whereas rhodium carboxylates produced C-H insertion products predominantly, a copper catalyst produced sigmatropic rearrangement products exclusively.A precursor with S-allyl side chain exhibited cyclisation via sigmatropic rearrangement with both copper and rhodium catalyst.
Ye, Tao,Garcia, Concepcion Fernandez,McKervey, M. Anthony
p. 1373 - 1380
(2007/10/02)
Asymmetric Synthesis of Substituted Chromanones via C-H Insertion Reactions of α-Diazoketones Catalysed by Homochiral Rhodium(II) Carboxylates
High levels of regio-, stereo- and enantio-selectivity are achieved in the asymmetric synthesis of six-membered oxygen heterocycles via intramolecular C-H insertion reactions of α-diazoketones catalysed by chiral rhodium(II) carboxylates.
McKervey, M. Anthony,Ye, Tao
p. 823 - 824
(2007/10/02)
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