Regio- and Enantioselective Catalytic Monoepoxidation of Conjugated Dienes: Synthesis of Chiral Allylic cis-Epoxides

• Published in: Organic letters Vol. 17; no. 4; pp. 1058 - 1061
• Main Authors: Jat, Jawahar L, De, Saroj Ranjan, Kumar, Ganesh, Adebesin, Adeniyi Michael, Gandham, Shyam K, Falck, John R
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 20.02.2015; Amer Chemical Soc
• Subjects: Alkadienes - chemical synthesis; Alkadienes - chemistry; Biological Products - chemistry; Catalysis; Chemistry; Chemistry, Organic; Combinatorial Chemistry Techniques; Epoxy Compounds - chemical synthesis; Epoxy Compounds - chemistry; Hydrogen Peroxide - chemistry; Letter; Molecular Structure; Physical Sciences; Science & Technology; Stereoisomerism; DIHYDROXYLATION; EPOXY ALCOHOLS; AQUEOUS HYDROGEN-PEROXIDE; COMPLEXES; ASYMMETRIC EPOXIDATION; SHARPLESS EPOXIDATION; HYDROPEROXIDE; OLEFINS; FATTY-ACIDS; ARACHIDONIC-ACID
• ISSN: 1523-7060; 1523-7052; 1523-7052
• DOI: 10.1021/acs.orglett.5b00281

Ti­(IV)-salan 4 catalyzes the diastereo- and enantioselective monoepoxidation of conjugated dienes using 30% H2O2 at rt or below even in the presence of other olefins and adjacent stereocenters. Its enantiomer, ent-4, provides access to the opposite diastereomer or enantiomer. The resultant chiral allylic epoxides, and the triols derived from them, are versatile synthetic intermediates as well as substructures present in many bioactive natural products. The epoxidation is highly specific for Z-olefins. For 1-acyl­(silyl)­oxypenta-2,4-dienes, epoxidation of the distal olefin is generally favored in contrast to the adjacent regioselectivity characteristic of Sharpless, peracid, and other directed epoxidations of hydroxylated dienes.