Synthesis of epoxides
The asymmetric addition of chiral sulfonium ylides to aldehydes is promoted by 2,5-dimethylthiolanes with a locked conformation. This user-friendly organocatalytic process proved to be efficient with 20-10% of sulfide in 1 or 2 days of reaction.
M. Davoust, J.-F. Briere, P.-A. Jaffres, P. Metzner, J. Org. Chem., 2005, 70, 4166-4169.
The first Corey-Chaykovsky epoxidation and cyclopropanation using trimethyl sulfonium iodide/trimethyl sulfoxonium iodide and KOH as base in the recyclable ionic liquid, (bmim)PF6 are described.
S. Chandrasekhar, Ch. Narasihmulu, V. Jagadeshwar, K. Venkatram Reddy, Tetrahedron Lett., 2003, 44, 3629-3630.
The generation of highly unstable chloromethylmagnesium chloride in a continuous flow reactor and a subsequent reaction with aldehydes and ketones provides chlorohydrins and epoxides in good yields within a total residence time of only 2.6 s. The outcome of the reaction can be tuned by simply using either a basic or an acidic quench.
T. von Keutz, D. Cantillo, C. O. Kappe, Org. Lett., 2020, 22, 7537-7541.
Rhodium(II) acetate catalyzed reactions of phenyl- and styryldiazoacetates with aldehydes, ketones, or imines enable stereospecific epoxidation and aziridination via carbonyl ylide intermediates.
M. P. Doyle, W. Hu, D. J. Timmons, Org. Lett., 2001, 3, 933-935.
A chiral titanium complex formed in situ from Ti(OiPr)4 and chiral 1,16-dihydroxytetraphenylene with rigid conformation enables highly diastereo- and enantioselective Darzens reactions between aldehydes and diazo-N,N-dimethylacetamide to provide cis-glycidic amides in good yields with excellent enantiomeric purities.
G.-L. Chai, J.-W. Han, H. N. C. Wong, Synthesis, 2017, 49, 181-187.
A camphor-derived amide-stabilized ylide reacts with aldehydes at -50°C in ethanol to give glycidic amides in one step with up to 99% ee and complete diastereoselectivity. Further transformations of epoxyamides were investigated.
V. K. Aggarwal, G. Hynd, W. Picoul, J.-L. Vasse, J. Am. Chem. Soc., 2002, 124, 9964-9965.
A highly stereoselective synthesis of aromatic α,β-unsaturated amides was achieved by treatment of aromatic α,β-epoxyamides with samarium diiodide. α,β-epoxyamides are easily prepared by the reaction of enolates derived from α-chloroamides with carbonyl compounds at -78°C.
J. M. Concellón, E. Bardales, J. Org. Chem., 2003, 5, 9492-9295.