Intramolecular Oxonium Ylide Formation–[2,3] Sigmatropic Rearrangement of Diazocarbonyl-Substituted Cyclic Unsaturated Acetals: A Formal Synthesis of Hyperolactone C

• Published in: Journal of organic chemistry Vol. 79; no. 20; pp. 9728 - 9734
• Main Authors: Hodgson, David M, Man, Stanislav, Powell, Kimberley J, Perko, Ziga, Zeng, Minxiang, Moreno-Clavijo, Elena, Thompson, Amber L, Moore, Michael D
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 17.10.2014; Amer Chemical Soc
• Subjects: Acetals - chemistry; Chemistry; Chemistry, Organic; Furans - chemical synthesis; Furans - chemistry; Molecular Structure; Onium Compounds - chemistry; Physical Sciences; Rhodium - chemistry; Science & Technology; Spiro Compounds - chemistry; Stereoisomerism; BIOLOGICAL EVALUATION; ALDEHYDES; GENERATION; CATALYZED DECARBONYLATION
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo501893r

Rh­(II)-catalyzed oxonium ylide formation–[2,3] sigmatropic rearrangement of α-diazo-β-ketoesters possessing γ-cyclic unsaturated acetal substitution, followed by acid-catalyzed elimination–lactonization, provides a concise approach to 1,7-dioxaspiro­[4.4]­non-2-ene-4,6-diones. The process creates adjacent quaternary stereocenters with full control of the relative stereochemistry. An unsymmetrical monomethylated cyclic unsaturated acetal leads to hyperolactone C, where ylide formation–rearrangement proceeds with high selectivity between subtly nonequivalent acetal oxygen atoms.