An effective method for the synthesis of highly functionalized isoxazoles from readily available starting ethyl α-nitrocinnamates has been developed. Ethyl α-nitrocinnamates react smoothly with α-nitro carbonyl compounds to produce isoxazoles in good yields. Michael addition of pyridinium ylides to ethyl α-nitrocinnamates can also produce these isox-
Metal Salt Mediated Radical Reactions of 2-Substituted-1,4-naphthoquinones.-Silver-catalyzed reaction of hydroxymethyl-substituted naphthoquinones (I) with -oxocarboxylic acids (II) provides access towards naphtho-fused furan derivatives (III). In a similar manner, aminomethyl-substituted naphthoquinones (IV) afford naphtho-fused pyrroles (V). Interestingly, manganese-mediated reaction of naphthoquinones (IV) with -keto ester (VI) gives the same naphtho-fused pyrroles (V) instead of the expected naphtho-fused pyridine derivatives. -(LIN, Z.-Y.; CHEN, Y.-L.; LEE, C.-S.; CHUANG*, C.-P.; Eur.
Free radical reactions have become increasingly important in organic synthesis in the last two decades. 1 Compounds containing the quinone group represent an important class of biologically active molecules that are widespread in nature. 2,3 Electrophilic radicals produced from the manganese(III) acetate oxidation of β-dicarbonyl compounds undergo efficient addition to a C-C double bond. 1d,e,4,5 These reactions can be performed intermo-10.
Two methods for the preparation of perhydroindan 7 are described. One involves an intramolecular free radical cyclization in a key step and proceeds in 13 step and 9% yield from anisole (9). The other involves an intramole" conjugate addition mediated by pyrrolidjne (28 -7) and proceeds in five step and 30% overall yield from vinylogous ester 29. Two unsuccessful attempts to convert 7 into mane sesquiterpenoids 1-6 are described. The synthesis of axanes 4-6 was achieved using a potassium tert-butoxide catalyzed cyclization of a dienoic keto ester as a key step (47 + 48 -49). Conversion of a,,%unsaturated ester 49 to vinyl isocyanate 57 was accomplished using a Curtius rearrangement and reduction of 57 with lithium triethylborohydride completed the synthesis of axamide-4 (4).The addition of t-BuLi to a low-temperature THF solution of o-bromocarbamates 2 leads to ortho-lithiated intermediates 3, in which internal trapping by the electrophile on the side chain then takes place. This novel Parham-type anionic cyclization procedure affords the variously substituted phthalides 5 in high yields and can also be used for the preparation of lactones 8, which are useful for the synthesis of aristocularine alkaloids.
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