Design and Synthesis of Chiral Ketones for Catalytic Asymmetric Epoxidation of Unfunctionalized Olefins

Abstract

A series of C 2 symmetric chiral ketones were designed and synthesized for catalytic asymmetric epoxidation of unfunctionalized olefins. Among those ketones screened, (R)-7, (R)-9, and (R)-10 were found to be highly efficient catalysts for epoxidation of trans-stilbenes with enantioselectivities in the range of 84−95%. Convincing evidence was provided for a spiro transition state of dioxirane epoxidation. Through the 18O-labeling experiment, chiral dioxiranes were found to be the intermediates in chiral ketone catalyzed epoxidation reactions.

Green Organocatalytic Oxidative Methods using Activated Ketones

“…TheS hi oxidation allows the epoxidation of various alkenes by utilizing easy-to-prepare fructose derivative 9 as the organocatalyst and Oxone (KHSO 5 )a st he oxidant(Scheme 8). [14][15][16][17][18][19][20][21][22][23][24] Other significant contributions in the same area (dioxirane chemistry) include the work of Yang [25][26][27] and Denmark, [28][29][30][31] who propose the use of other activated ketones such as 10 and 11 as catalysts (Scheme 9).…”

Direct Synthesis of ESBO Derivatives‐18O Labelled with Dioxirane

“…Before proceeding with the polyepoxidation of the triglyceride, in order to assess the amount of labelled of 18 O-DDO ( 1a ), it appears necessary to explore its efficacy in the labelled reaction, as both 16 O and 18 O oxygen atoms of the dioxirane can be transferred to substrate [23]. …”

“…Further a possible alternative to obtain labelled epoxides consists of using DDO ( 1a ) 18 O labelled, generated in situ , from acetone and potassium monoperoxysulfate (KHSO 5 ) K + -O-SO 2 - 18 O 18 OH (caroate) 18 O-labelled—as reported in Scheme 2 [23]. …”

Asymmetric Epoxidation in Stereoselective Synthesis

“…40 When 10 mol% of ketone 55 was used, high enantioselectivity (up to 95% ee) was achieved for the asymmetric epoxidation of trans-olefin 56 (Scheme 35.14). 41 Ketone 54 has been applied by scientists at Tanabe Seiyaku Company (Osaka, Japan) in the large-scale preparation of chiral epoxide 59 58 with ketone catalyst 54 and Oxone provided epoxide 59 in 87% yield and 79% ee. The epoxide was further purified by recrystallization to afford pure 59 in 64% yield and >99% ee.…”