Alder-Ene Reaction Ene Reaction

The Four-electron System Including An Alkene π-bond And An Allylic C-H σ-bond Can Participate In A Pericyclic Reaction In Which The Double Bond Shifts And New C-H And C-C σ-bonds Are Formed. This Allylic System Reacts Similarly To A Diene In A Diels-Alder Reaction, While In This Case The Other Partner Is Called An Enophile, Analogous To The Dienophile In The Diels-Alder. The Alder-Ene Reaction Requires Higher Temperatures Because Of The Higher Activation Energy And Stereoelectronic Requirement Of Breaking The Allylic C-H σ-bond.

The Enophile Can Also Be An Aldehyde, Ketone Or Imine, In Which Case β-hydroxy- Or β-aminoolefins Are Obtained. These Compounds May Be Unstable Under The Reaction Conditions, So That At Elevated Temperature (>400°C) The Reverse Reaction Takes Place - The Retro-Ene Reaction.

While Mechanistically Different, The Ene Reaction Can Produce A Result Similar To The Prins Reaction.

Mechanism Of The Alder-Ene Reaction

Also Like The Diels-Alder, Some Ene Reactions Can Be Catalyzed By Lewis Acids. Lewis-Acid Catalyzed Ene Reactions Are Not Necessarily Concerted

Recent Literature

Formaldehyde Encapsulated In Zeolite: A Long-Lived, Highly Activated One-Carbon Electrophile To Carbonyl-Ene Reactions
T. Okachi, M. Onaka, J. Am. Chem. Soc.2004126, 2306-2307.

Ytterbium(III) Triflate/TMSCl: Efficient Catalyst For Imino Ene Reaction
M. Yamanaka, A. Nishida, M. Nakagawa, Org. Lett.20002, 159-161.

Asymmetric Carbonyl-Ene Reaction Catalyzed By Chiral N,N′-Dioxide-Nickel(II) Complex: Remarkably Broad Substrate Scope
K. Zheng, J. Shi, X. Liu, X. Feng, J. Am. Chem. Soc.2008130, 15770-15771.

Highly Enantioselective Carbonyl-ene Reactions Catalyzed By A Hindered Silyl-Salen-Cobalt Complex
G. E. Hutson, A. H. Dave, V. H. Rawal, Org. Lett.20079, 3869-3872.

Highly Enantioselective And Anti-Diastereoselective Catalytic Intermolecular Glyoxylate-Ene Reactions: Effect Of The Geometrical Isomers Of Alkenes
X. Zhang, M. Wang, R. Ding, Y.-H. Xu, T.-P. Loh, Org. Lett.201517, 2736-2739.

Steric Acceleration Of An Uncatalysed Ene Reaction At Room Temperature
N. Choony, P. G. Sammes, G. Smith, R. Ward, Chem. Commun.2001, 2062-2063.

Iron(III) Chloride Catalysis Of The Acetal-Ene Reaction
A. Ladépêche, E. Tam, J.-E. Ancel, L. Ghosez, Synthesis2004, 1375-1380.

Direct Synthesis Of β-Alkyl N-Aryl Aza Baylis-Hillman Adducts Via Nitroso-Ene Reaction
S. Murru, A. A. Gallo, R. S. Srivastava, J. Org. Chem.201277, 7119-7123.

Regioselective Ene-Type Allylic Chlorination Of Electron-Rich Alkenes By Activated DMSO
V. P. Demertzidou, S. Pappa, V. Sarli, A. L. Zografos, J. Org. Chem.201782, 8710-8715.

Ene Reaction Of Arynes With Alkynes
T. T. Jayanth, M. Jeganmohan, M.-J. Cheng, S.-Y. Chu, C.-H. Cheng, J. Am. Chem. Soc.2006128, 2232-2233.

2-Methylenetetrahydropyrans: Efficient Partners In The Carbonyl Ene Reaction
G. Liang, D. T. Sharu, T. Lam, N. I. Totah, Org. Lett.201315, 5974-5977.

Confined Acid-Catalyzed Asymmetric Carbonyl-Ene Cyclization
L. Liu, M. Leutzsch, Y. Zheng, M. W. Alachraf, W. Thiel, B. List, J. Am. Chem. Soc.2015137, 13268-13271.