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DOI: 10.1055/s-0036-1588367
Catalytic Prins Reaction Effected by Molecular Iodine in the Presence of Bis(trifluoromethanesulfonyl)imide Salts
Publikationsverlauf
Received: 03. November 2016
Accepted: 07. November 2016
Publikationsdatum:
09. Dezember 2016 (online)


Dedicated to Prof. Dieter Enders on the occasion of his 70th birthday
Abstract
The Prins reaction is an efficient method for the direct generation of 1,3-dioxanes from alkenes and aldehydes. As first published in 2008, this process can be effected by stoichiometric amounts of molecular iodine. We herein report a catalytic protocol allowing the use of iodine at low loading (0.5–5 mol%), smoothly effecting the condensation of styrenes with aliphatic aldehydes to rac-1,3-dioxanes. Moreover, this mild catalytic system effects the isomerization of the 1,3-dioxane products to the thermodynamically favored one. As a result, substituted rac-1,3-dioxanes were prepared in high yields (up to 92%), and with high diastereoselectivities (d.r. up to 82:18). For the application of iodine in catalytic amounts, the addition of pyridinium bis(trifluoromethanesulfonyl)imide (TFSI) salts in a 1:1 ratio to iodine is the key to success.
Key words
Prins reaction - catalysis - 1,3-dioxanes - molecular iodine - bis(trifluoromethanesulfonyl)imide saltsSupporting Information
- Supporting information for this article is available online at http://dx.doi.org/10.1055/s-0036-1588367. Included are: the synthesis of the pyridinium salts 5–7·NTf2; catalytic condensation of 1 with 2 to give 3 on a preparative scale; NMR spectra of pyridinium salts, 1,3-dioxanes 3, mixture of iodine/7·NTf2, the reaction progress between 1a and 2a′; X-ray data of 5·NTf2 and 3haA;19 and UV/Vis spectra of iodine/TFSI salts.
- Supporting Information