Epoxidation of homoisoflavones Lévai, Albert
Journal of heterocyclic chemistry,
March/April 2003, Letnik:
40, Številka:
2
Journal Article
Recenzirano
A comparative study of the epoxidation of homoisoflavones (3‐benzyl‐4‐chromones) 1–4 has been performed by various oxidizing agents, víz. Epoxidation with isolated dimethyldioxirane (Method A), with ...alkaline hydrogen peroxide (Method B), and with sodium hypochlorite (Method C) to obtain the epoxides 4–8. Compounds 2 and 3 have also been oxidized with a combination of dimethyldioxirane and Jacobsen's Mn(III)salen catalysts (R,R)‐11 and (S,S)‐11 to afford 3‐benzoyl‐4‐chromones 9 and 10. Structures of all new compounds have been elucidated by microanalyses, ir and nmr spectroscopic measurements.
Kinetic resolutions of a series of racemic 4-hydroxychromans by the
Candida cylindracea lipase catalysed acetylation are described. Correlation between structure (conformation) and enantioselectivity ...is discussed.
Kinetic resolution of (±)
1–5, using CCL lipase for acetylation with vinylacetate in n-hexane, was carried out.
Stereoselective synthesis of trans‐2,3,3a,4‐tetrahydro‐3‐aryl‐2‐phenyl1benzopyrano4,3‐cpyrazoles 13–18 and their 1benzothiopyrano analogues 19–24 has been performed by the reaction of ...3‐arylidenechromanones 1–6 and 3‐arylidene‐1‐thiochromanones 7–12 with phenylhydrazine in hot pyridine. The structure and stereochemistry of the compounds prepared have been elucidated by ir, lH and 13C nmr measurements.
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.
1‐Acetyl‐ and 1‐propionyl‐2‐pyrazolines 11‐27 have been synthesized by the reaction of (3‐coumarinyl)chalcones 1‐10 with hydrazine in hot acetic acid or propionic acid. While ...5‐aryl‐3‐(3‐coumarinyl)‐1‐phenyl‐2‐pyrazolines 28‐35 have been prepared by the reaction of (3‐coumarinyl)chalcones 1,3,5‐10 with phenylhydrazine in hot pyridine. Structures of all new compounds have been elucidated by microanalyses, 1H and 13C nmr spectroscopies.
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