129056-84-4Relevant academic research and scientific papers
Addition of silyloxydienes to 2-substituted 1,4-benzoquinones and 1,4-naphthoquinones
Brimble, Margaret A.,Elliott, Richard J.R.
, p. 7715 - 7730 (2007/10/03)
Addition of 1-trimethylsilyloxybuta-1,3-diene 2 to the quinones 4,5,6,17,18,19,20 bearing formyl, acetyl, methoxycarbonyl or carboxamide substituents at C-2, afforded the Diels-Alder adducts 11,12,13,25,26,27,28 whereas addition of 2-trimethylsilyloxyfuran 3 afforded the fragmentation products 29,30,31,35,36,37,38. Quinones 7,21 bearing a carboxyl group at C-2 afforded 1,4-naphthoquinone and 9,10-anthracenedione with 2 and no adducts were isolated from reaction with 3. Benzoquinone-sulfide 8 afforded Diels-Alder adduct 14 and fragmentation product 32 with 2 and 3 respectively whereby reaction occurred on the less substituted double bend. No adducts were isolated upon treatment of naphthoquinone-sulfide 22 with either 2 or 3. The Diels-Alder adducts of benzoquinone-sulfoxide 9 and naphthoquinone-sulfoxide 23 with 2 underwent facile aromatisation to 1,4-naphthoquinone and 9,10-anthracenedione with 2. Addition of 3 to 9 afforded fragmentation product 33 whereas analogous reaction with 23 was unsuccessful. Addition of dienes 2,3 to benzoquinone-sulfone 10 afforded fragmentation products 16,34 respectively, whereas naphthoquinone-sulfone 24 afforded 9,10-anthracenedione with 2 and no products with 3.
Synthesis of 5-epi-7-Deoxykalafungin and 5-epi-7-O-Methylkalafungin
Brimble, Margaret A.,Stuart, Susan J.
, p. 881 - 885 (2007/10/02)
The syntheses of 5-epi-7-deoxykalafungin (12a) and 5-epi-7-o-methylkalafungin (12b), compounds closely related to the pyranonaphthoquinone antibiotic kalafungin (1), have been completed making use of the transformation of the one tricyclic ring system into another.The uncatalysed 1,4-addition of 2-trimethylsilyloxyfuran (4) to the 2-acetyl-1,4-naphthoquinones (8) gave the furonaphthofurans (9) which underwent facile oxidative rearrangement, in 72-76percent yield using cerium(IV) ammonium nitrate, to the furonaphthopyrans (11) which contain the same ring system as the natural product kalafungin (1).Reduction of the hemiacetals (11) to the cyclic ethers (12) was effected using triethylsilane in trifluoracetic acid.The analogous rearrangement of the furobenzofuran (5a) to the furobenzopyran (6) proceeded in only 27percent yield.Further insight into the mechanism of the intial 1,4-addition reaction was gained by isolation of the intermediate (13) in the reaction of 2-trimethylsilyloxyfuran (4) with the naphthoquinone (8a).
