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6150506 
Book/Book Chapter 
2.03 Prins Reactions and Carbonyl, Imine, and Thiocarbonyl Ene Reactions 
Snider, BB 
2014 
Elsevier 
Amsterdam 
Comprehensive Organic Synthesis II (Second Edition) 
148-191 
Aldehydes and ketones react with alkenes either thermally or in the presence of Brønsted or Lewis acids to afford either Prins or ene products. This chapter covers advances in this area since the publication of the first edition of COS in 1991. Intermolecular ene reactions of formaldehyde, chloral, fluoral, glyoxylate esters, aliphatic and aromatic aldehydes, ketones, and electron-deficient ketones such as pyruvate esters are broadly useful. Thermal and Lewis acid-catalyzed intramolecular type I ene reactions leading to 2-alkenylcyclopentanols and cyclohexanols and type II ene reactions leading to 3-methylenecyclohexanols and cycloheptanols provide a general route to these ring systems. Intramolecular Prins reactions are useful for the preparation of functionalized cycloalkanols. Alkoxonium cations undergo oxonium ene reactions and Prins cyclizations that provide a general route to substituted tetrahydropyrans. The ene reactions of imines and thiocarbonyl compounds are also covered. Major advances that have been made since the first edition was published include asymmetric intermolecular ene reactions of electron-deficient aldehydes and ketones, Prins cyclizations, and Prins-pinacol reactions. 
Asymmetric reactions; Carbonyl ene reaction; Glyoxylate esters; Homoallylic alcohols; Intramolecular reactions; Lewis acid catalysis; Oxonium ene reaction; Prins addition; Prins cyclization; Prins-pinacol reaction 
Knochel, Paul