M. I. Flores-Conde, M. Vázquez, Leonor Reyes
Jul 25, 2013
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Journal
Organometallics
Abstract
The synthesis of novel and highly substituted (2Z,3Z)-3-ethoxy-1-(aryl/cyclohexenyl)-4-aryl-2-(phenylimino)but-3-en-1-one derivatives 24a–k and 27a–e by an unexpected and previously unreported [3 + 2] cycloaddition/rearrangement and ring-opening cascade process of the Fischer carbene complexes (CO)5M═C(C≡C–Ar)OCH2CH3 1a–c (M = Cr) and 1d–f (M = W) and (CO)5M═C(C≡C-cyclohexenyl)OCH2CH3 23a (M = Cr) and 23b (M = W) with C,N-diaryl nitrones (7a–f) is described. It is likely that the unstable 2,3-dihydroisoxazole carbene complexes produced in the [3 + 2] cycloaddition undergo a rapid and new rearrangement, followed by a stereoselective electrocyclic ring-opening process at a low temperature, to give only the (Z,Z) diastereoisomers 24a–k and 27a–e as the isolated products. The stereochemical assignment of the products was supported by NOE measurements and by single-crystal X-ray diffraction.