A Brønsted Acid Mediated Cascade Enone Synthesis from Aldehydes Containing a Tethered Propargylsilane

• Published in: Journal of organic chemistry Vol. 73; no. 4; pp. 1631 - 1634
• Main Authors: Ramalho, Rui, Jervis, Peter J, Kariuki, Benson M, Humphries, Alexander C, Cox, Liam R
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 15.02.2008; Amer Chemical Soc
• Subjects: Acids - chemistry; Aldehydes - chemistry; Chemistry; Chemistry, Organic; Exact sciences and technology; Heterocyclic compounds; Kinetics and mechanisms; Miscellaneous; Organic chemistry; Physical Sciences; Preparations and properties; Reactivity and mechanisms; Science & Technology; ASYMMETRIC-SYNTHESIS; INTRAMOLECULAR GLYCOSIDATION; ALLENYLSILANES; ALLYLATION; ALLYLSILANES; TEMPORARY SILICON CONNECTION; HIGHLY STEREOSELECTIVE-SYNTHESIS; IMINIUM IONS; STEREOCONTROLLED SYNTHESIS; CYCLIZATION; Water; Intramolecular reaction; Acetylenic compound; Alcohol; Organic silane; Methanesulfonic acid; Aldehyde; Dehydration; Allylic compound; Brönsted acid; Cyclization; Carbocation; Reaction mechanism; Chemical synthesis; Allenic compound; Enone; Oxygen silicon heterocycle; Room temperature; Successive reaction
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo702351s

MeSO3H effects the intramolecular allenylation of a series of aldehydes 1 to provide allenyl alcohol product 3 as a single diastereoisomer. Cyclization proceeds rapidly at −78 °C. However, when the reaction is performed at room temperature, aldehyde 1 provides enone product 7 instead. A mechanism for the formation of this product is proposed in which the initially formed allenyl alcohol 3 undergoes dehydration to provide an allyl carbocation, which is trapped with water, thereby installing the enone.