Isoflavone epoxide

The fragrance industry has made use of small molecule epoxy furans. The rose flavone epoxide 78 and rose isoflavone epoxide 79 are components of a perfume that is mild and gives refreshing feels <1996JPP8092588>. Perfumes containing these components can be used in the manufacture of cosmetics, air fresheners, and other products. 

Adam et al. also successfully applied Wynberg s condition to the asymmetric epoxidation of isoflavones [22], Using the chiral PTC 18 and cumyl hydroperoxide (CHP) as an oxidant, the isoflavone epoxide was obtained almost quantitatively and with excellent enantio selectivity (up to 98% ee) even at a low catalyst loading (1 mol%) (Scheme 5.16). 

SCHEME 49. Weitz-Scheffer epoxidation of isoflavones 101 by various hydroperoxides and the chiral PTCs 103h-k... 

The oxidative rearrangement of chalcones is a valuable route to isoflavones which has been thoroughly investigated. Initially, the conversion was achieved in two distinct steps. Epoxidation of a 2 -benzyloxychalcone, carried out by conventional techniques, is followed by treatment with a Lewis acid, such as boron trifluoride etherate, which brings about the rearrangement. 

The N-benzylcinchonidinium catalyst 70 was successfully employed by Barrett et al. in the synthesis of (—)-preussomerin G [112]. As a key step the epoxide 72 was obtained from the quinone acetal 71 in 81% yield and with 95% ee in the presence of 10 mol% of the ammonium salt 70 (Scheme 10.15). Adam et al. recently reported the highly enantioselective epoxidation of isoflavones [113]. The best results, i.e. ee up to 98% with essentially quantitative yields, were achieved when... 

Iron(III)sulfate, 223-224 Isatin, 331 Isatoic acid, 331 Isoatlantolactone, 263, 264 Isobutenyl acetate, 153 Isobutyronitrile, 110 Isocyanates, 14-15 Isoflavones, 410 Isopavine, 217 Isopenams, 325 Isophorone, 197, 198 Isopinocampheylborane, 224 Isoprene epoxide, 4 Isopropenyl phenyl sulfone, 316 Isopropenyltriphenylphosphonium bromide, 225... 

Scheme 3 presents substrates which carry both electron-donating and electron-withdrawing substituents. These systems, in comparison with the previous set of substrates, were considerably less reactive so that longer reaction times and excess oxidant were necessary for complete epoxidations. In the rosette are displayed the oxidation of p-oxo enol phosphates [13] 13, dihydrofuranone [17] 14, p-alkoxycyc-lohexenones [17] 15, alkoxymethylenecyclohexanones [17] 16, benzalphthalide [12a] 17, aurones [18] 18, flavones [19] 19, and isoflavones [18] 20. Many of these epoxides, which have become available for the first time, constitute valuable building blocks for natural product chemistry. 

Flavones and isoflavones (3-aryl-chromones) are quantitatively converted into 2,3-epoxides by exposure to dimethyl dioxirane flavone oxides are quantitatively converted by acid into 3-hydroxy-flavones, which are naturally occurring. ... 

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