Epoxides ring-opening cascade

Steps Including cascade RedAI-H mediated epoxide ring opening... 

In 1983, Cane et al. postulated that polyether biosynthesis takes place as a two step process. The first of these steps was proposed to be the enzymatically polyepoxidation of an acyclic hydroxypolyene precursor, and the second comprised a cascade of intramolecular epoxide ring openings with formation of the polyether frame work. [1] For monensin A... 

As a further extension of push-pull dipole cycloaddition chemistry, the Rh (I I)-catalyzed cycHzation/cycloaddition cascade was applied toward the hexacyclic framework of the kopsifoline alkaloids. The kopsifolines 14 are structurally intriguing compounds, related to and possibly derived from an aspidosperma-type alkaloid precursor 12. A possible biogenetic pathway to the kopsifolines from 12 could involve an intramolecular epoxide-ring opening followed by loss of H2O as shown in Scheme 4. The interesting biological activity of these compounds, combined with their... 

Boningari, T., Ohnos, A., Reddy, B. M., Sommer, J., and Pale, P. 2010. Zeo-click chemistry Copper(I)-zeofite-catalyzed cascade reaction one-pot epoxide ring-opening and cycloaddition. Eur. J. Org. Chem. 2010(33) 6338-6347. 

Negative photoresist chemistry. A. Cross-linking of a prolyisoprene rubber by a photoreactive bisazide. B. A radical induced polymerization and cross-linking of an acrylate monomer. C. A single component resist. Electron beam irradiation produces anions that launch a cascade of epoxide ring-opening reactions to cross-link the poljrmer. 

Based on enantioselective epoxidation and subsequent ring opening and closing, the so-called Achmatowicz reaction was developed. This is an organocatalytic one-pot cascade for the annulation of a,(J-unsaturated aldehydes, hydrogen peroxide, p-carbonyl compounds and NBS, which furnish optically active 3-pyrones. Other chiral heterocycles were also assembled by organocatalytic cascade reactions using diaiylprolinol silyl ethers as catalysts. ... 

More recently, Wu, Seller and co-workers reported a cascade procedure for the synthesis of 2,3-dihydrobenzodioxepinone from 2-bromophenols and epoxides. The reactions undergo nucleophilic ring-opening of epoxides and subsequent palladium-catalyzed intramolecular alkoxylcarbonylation. Moderate to good yields of the versatile desired products were obtained in a regio-selective manner (major product >90%) under mild conditions (Scheme 4.6). 

Alkenyl epoxides have been analogously used in the synthesis of bicyclic compounds [69]. Addition of a thiyl radical to a suitably protected epoxyketone enolate generated the oxiranyl carbinyl radical which initiated a cascade of uni-molecular steps (i.e. ring-opening, 1,5-radical translocation, 5-exo cyclization, and ejection of the PhS radical) to produce the final enol product in good yield and high diastereoselectivity (equation (31)). The PhS radical-induced fragmentation of alkenyl epoxy silanes has been found to afford a-trimethylsilyl aldehydes [70]. 

Recent progress in the synthesis of oxepanes and medium ring ethers. Tetrahedron, 68, 6999-7018. (d) Vilotijevic, L, Jamison, T. F. (2009). Epoxide-opening cascades in the synthesis of polycyclic polyether natural products. Angewaudte Cheruie lutematioual Edition, 48, 5250-5281. (e) Snyder, N. L., Haines, H. M., Peczuh, M. W. (2006). Recent developments in the synthesis of oxepines. Tetrahedron, 62, 9301-9320. (f) For medium-ring thiacycles Rosowsky, A. 1972. In Weissberger, A., Taylor, E. C. (Eds.) Heterocyclic Compounds. Wiley, New York. Vol. 26. 

The purpose of this chapter is to describe the use of epoxides as biosynthetic precursors for cyclic ethers. The advances that allow for predictable chemical synthesis based on epoxide opening, including the development of models for regiocontrol in intramolecular ring-opening reactions and stereoselective synthesis, will be described. Numerons examples of epoxide cascade reactions in natural product synthesis will conclude the chapter. 

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