The Prins Reaction is the acid-catalyzed of addition aldehydes to alkenes, and gives different products depending on the reaction conditions. It can be thought of conceptually as the addition of the elements of the gem-diol carbonyl hydrate of the aldehyde across the double bond.
An excess of aldehyde and temperatures < 70 °C lead to the formation of acetals. When one equivalent of aldehyde is used and temperatures are > 70 °C diols or allylic alcohols may be isolated.
Although the mechanism is different, a Prins allylic alcohol product is equivalent to the result of an Ene Reaction.
Mechanism of the Prins Reaction
Lewis Acidic Chloroaluminate Ionic Liquids: Novel Reaction Media for the Synthesis of 4-Chloropyrans
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Preparation of trans-2-Substituted-4-halopiperidines and cis-2-Substituted-4-halotetrahydropyrans via AlCl3-Catalyzed Prins Reaction
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An efficient method allows the construction of 2,6-cis-4,5-dibromo-tetrasubstituted tetrahydropyran rings with well-controlled stereochemistry in good yields.
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5- and 6-Exocyclic Products, cis-2,3,5-Trisubstituted Tetrahydrofurans, and cis-2,3,6-Trisubstituted Tetrahydropyrans via Prins-Type Cyclization
S. N. Chavre, H. Choo, J. K. Lee, A. N. Pae, Y. Kim, Y. S. Cho, J. Org. Chem., 2008, 73, 7467-7471.
Brřnsted Acid-Mediated Stereoselective Cascade Construction of Functionalized Tetrahydropyrans from 2-(Arylmethylene)cyclopropylcarbinols and Aldehydes
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