Epoxidation studies of 2-styrylchromones using jacobsen's catalyst and hydrogen peroxide and iodosylbenzene as oxidants

Abstract

The epoxidation of 2‐styrylchromones 2a‐h using Jacobsen's Mn(III)[salen] complex 1 as catalyst is reported for the first time. Several studies were performed using both hydrogen peroxide and iodosylbenzene as oxidants, in order to obtain the α,β‐epoxy‐2‐styrylchromones 3a‐h regioselectively. Due to the low reactivity of the substrates and the highly unstable character of the formed epoxides, reactions should be interrupted at lower conversions to obtain acceptable yields, especially when hydrogen peroxide is used.

Dimethyldioxirane Oxidation of Exocyclic (E,E)-Cinnamylideneketones

“…From the 2D-COSY experiments, all the proton resonances of the α,β:γ,δ-diepoxide system were assigned, H-3 (doublet at δ H 3.24-3.70), H-2 (double doublet at δ H 2.97-3.18), and H-3 (doublet at δ H 3.90-4.69). The coupling constant values J H2 -H3 ∼1.7-2.1 Hz are consistent with a trans configuration of the γ,δ-epoxide, [9,14] whereas those of J H3 -H2 are dependent on the size of the cyclanone ring and on the stereochemistry of the diastereomers (4a-c, J 3.8-4.9 Hz for A and J 5.6-6.0 Hz for B; 4d-f, J 4.4-6.0 Hz for A and J 6.1-6.6 Hz for B; 4g-i, J 5.0-6.3 Hz for A and J 6.8-7.2 Hz for B). The aromatic region of the 1 H NMR spectra of α,β:γ,δ-diepoxides 4a-i presents several multiplets, which were assigned with the aid of all 2D NMR spectra.…”

Chemistry of Polyvalent Iodine

“…The oxidation reactions of iodosylarenes can be effectively catalyzed by metal salts and complexes . Iodosylbenzene is widely used as the most efficient terminal oxidantsource of oxygen in biomimetic oxidations catalyzed by metalloporphyrins and other transition metal derivatives. − Recent examples of transition metal-catalyzed oxidations employing iodosylbenzene include the hydroxylation of hydrocarbons, − the transition metal-mediated epoxidation of alkenes, ,− oxidation of alcohols , or silyl ethers to carbonyl compounds, δ-sultone formation through Rh-catalyzed C−H insertion, and oxidation of organic sulfides ,, to sulfoxides.…”

“…6 Iodosylbenzene is widely used as the most efficient terminal oxidantssource of oxygen in biomimetic oxidations catalyzed by metalloporphyrins and other transition metal derivatives. [141][142][143][144][145] Recent examples of transition metal-catalyzed oxidations employing iodosylbenzene include the hydroxylation of hydrocarbons, [146][147][148][149][150][151] the transition metal-mediated epoxidation of alkenes, 138,[152][153][154][155][156][157][158][159][160][161][162][163][164][165][166][167][168][169] oxidation of alcohols 170,171 or silyl ethers 172 to carbonyl compounds, δ-sultone formation through Rh-catalyzed C-H insertion, 173 and oxidation of organic sulfides 163,174,175 to sulfoxides.…”

“…[867][868][869][870][871][872][873] Koser and co-workers have found that the treatment of electron-rich aromatic substrates, such as anthracene, pyrene, 2-alkylthiophenes, and 1,4dimethoxybenzene with phenyliodonium bis(carbonyl)methylides in the presence of BF 3 •Et 2 O leads to bis(carbonyl)alkylation of the aromatic nucleus. 867 156). This reaction proceeds through initial carbene formation, followed by a ring-contraction, leading to an intermediate R,R′-dioxoketene, 874 which reacts with amines 476 to afford the final amides 477.…”

An Overview of 2‐Styrylchromones: Natural Occurrence, Synthesis, Reactivity and Biological Properties

“…Although the best results were accomplished with iodosylbenzene as oxidant, poor yields are generally obtained, due to the low reactivity of 2-SCs and the unstable character of the epoxides formed. [111] Scheme 27. Epoxidation of 2-SCs with hydrogen peroxide and iodosylbenzene in the presence of the Jacobsen catalyst (107).…”