Unprecedented Synthesis of 3-Alkenyl-3-ethoxy-2-iminoketones via 1,3-Dipolar Cycloadditions of Nitrones with Alkynyl Fischer Carbene Complexes

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• 作者：Mar铆a In茅s Flores-Conde ; Miguel Angel V谩zquez ; Leonor Reyes ; Joaqu铆n Tamariz ; Francisco Delgado
• 刊名：Organometallics
• 出版年：2013
• 出版时间：August 12, 2013
• 年：2013
• 卷：32
• 期：15
• 页码：4244-4254
• 全文大小：506K
• 年卷期：v.32,no.15(August 12, 2013)
• ISSN：1520-6041

文摘

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鈥?b>k and 27a鈥?b>e by an unexpected and previously unreported [3 + 2] cycloaddition/rearrangement and ring-opening cascade process of the Fischer carbene complexes (CO)₅M鈺怌(C鈮鈥揂r)OCH₂CH₃ 1a鈥?b>c (M = Cr) and 1d鈥?b>f (M = W) and (CO)₅M鈺怌(C鈮-cyclohexenyl)OCH₂CH₃ 23a (M = Cr) and 23b (M = W) with C,N-diaryl nitrones (7a鈥?b>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鈥?b>k and 27a鈥?b>e as the isolated products. The stereochemical assignment of the products was supported by NOE measurements and by single-crystal X-ray diffraction.