DBU-mediated Ireland–Claisen rearrangement of allyl alk-3-enoates: an efficient synthesis of 2-ethylidene-γ,δ-unsaturated carboxylic acids

• Published in: Tetrahedron Vol. 63; no. 39; pp. 9605 - 9613
• Main Authors: Li, Yunxia, Goeke, Andreas, Wang, Ruiyao, Wang, Quanrui, Fráter, Georg
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 24.09.2007; Elsevier
• Subjects: 2-Ethylidene-γ,δ-unsaturated carboxylic acids; Chemistry; Chemistry, Organic; DBU; Ireland–Claisen rearrangement; Physical Sciences; Science & Technology; Ireland–Claisen rearrangement; DBU; 2-Ethylidene-γ,δ-unsaturated carboxylic acids; ORGANIC-SYNTHESIS; ROUTE; STEREOCHEMICAL CONTROL; COPE; ESTERS
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2007.07.031

Ireland–Claisen rearrangement, triggered by silyl enolization of allylic but-3-enoates 2, has been developed using DBU as the base in the presence of an excess amount of TMSCl under reflux in acetonitrile for a couple of hours. The procedure allows the synthesis of a range of 2-ethylidene-γ,δ-unsaturated carboxylic acids 5 in moderate to high yields. It is further revealed that the rearrangement proceeds equally well with allylic ( E)-hexa-3,5-dienoates 10 derived from sorbic acid under similar conditions to provide 2-allyl substituted hexa-2,4-dienoic acids 13. [Display omitted] Ireland–Claisen rearrangement, triggered by silyl enolization of allylic but-3-enoates 2, was achieved using DBU as the base in the presence of an excess amount of TMSCl to provide 2-ethylidene-γ,δ-unsaturated carboxylic acids 5 in good yields.