A pericyclic process in which an alkene bearing an allylic hydrogen (the ene) reacts with an electron-deficient multiple bond (the enophile) to form a new σ bond and to transpose the double bond defines the ene reaction. In the concerted limit a six-electron cyclic transition state transfers the allylic hydrogen to the enophile while the new C–C (or C–X) bond forms. The nitroso ene reaction is a regioselective and stereoselective allylic nitrogen functionalization in which a nitroso compound is the enophile [1]. When both the ene and the enophile are tethered in one molecule, the intramolecular variant (including the Conia-ene reaction of an enol or enol equivalent with an alkyne) produces a carbocycle [2]. Gold(I)-catalyzed Conia-ene reactions proceed by metal activation of the alkyne [2]. Enantioselective variants impose facial control while retaining the same C–C-forming cyclization topology [3]. The concept is distinct from the Diels–Alder reaction (a [4+2] cycloaddition without hydrogen transfer) and from stepwise allylic substitutions that do not follow the pericyclic ene topology [1].
- ene reaction
- pericyclic reaction
- allylic hydrogen transfer
- Conia-ene
Chemical Synthesis and Reactions • Organic Chemistry • Chemistry • Physical Sciences
References
- Waldemar Adam; Oliver Krebs; The Nitroso Ene Reaction: A Regioselective and Stereoselective Allylic Nitrogen Functionalization of Mechanistic Delight and Synthetic Potential. Chem. Rev. 2003, 103, 4131-4146, 10.1021/cr030004x.
- Joshua J. Kennedy-Smith; Steven T. Staben; F. Dean Toste; Gold(I)-Catalyzed Conia-Ene Reaction of β-Ketoesters with Alkynes. J. Am. Chem. Soc. 2004, 126, 4526-4527, 10.1021/ja049487s.
- Britton K. Corkey; F. Dean Toste; Catalytic Enantioselective Conia-Ene Reaction. J. Am. Chem. Soc. 2005, 127, 17168-17169, 10.1021/ja055059q.