(5, 6‐Dihydro‐1, 4‐dithiin‐2‐yl)methanol as a Versatile Allyl‐Cation Equivalent in (3+2) Cycloaddition Reactions. Issue 42 (6th October 2016)

• Record Type: Journal Article
• Authors: Hullaert, Jan; Winne, Johan M.
• Is Part Of: Angewandte Chemie international edition. Volume 55:Issue 42(2016)
• Page Start: 13254
• Page End: 13258
• Publication Date: 2016-10-06
• Subjects: allyl cations -- cycloaddition -- cyclopentanoids -- fused-ring systems -- thionium ions; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201606411
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: The title heterocyclic alcohol readily generates a sulfur‐substituted allylic cation upon simple treatment with a protic acid, thus facilitating a synthetically useful stepwise (3+2) cycloaddition reaction pathway with a range of conjugated‐olefin‐type substrates. The introduction of an allyl fragment in this way provided rapid access to a variety of cyclopentanoid scaffolds. The cyclic nature of the cation precursor alcohol was shown to be instrumental for efficient cycloaddition reactions to take place, thus indicating an attractive strategy for controlling the reactivity of heteroatom‐substituted allyl cations. The formal cycloaddition reaction is highly regio‐ and stereoselective and was also used for a short total synthesis of the natural product cuparene in racemic form through a cycloaddition–hydrodesulfurization sequence. Abstract : Locked and loaded : Ethanedithiol was used as a temporary tether to control the reactivity of the allyl cation. A thionium‐stabilized carbocation was thus generated from allyl alcohol under acidic conditions and directly used in a stepwise (3+2) cycloaddition with a range of alkene substrates to give a variety of cyclopentanoid products (see scheme). A short total synthesis of the natural product cuparene in racemic form is also described.