- Efficient construction of benzohydrindenones from aryltrienones via domino Nazarov electrocyclization - Electrophilic aromatic substitution
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1,4-Dien-3-ones substituted with pendant arylethyl side chains attached at C-1 were readily prepared from substituted dihydrocinnamaldehydes. Treatment with TiCl4 at low temperature effected domino Nazarov electrocyclization - arene trapping within 5 min to give racemic benzohydrindenones in near-quantitative yield and with complete diastereoselectivity.
- Browder, Cindy C.,Marmsaeter, Fredrik P.,West
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p. 375 - 385
(2007/10/03)
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- Highly efficient trapping of the Nazarov intermediate with substituted arenes.
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1,4-Dien-3-ones bearing pendant arylethyl side chains were readily prepared from substituted dihydrocinnamaldehydes. When treated with TiCl(4) at low temperature, these compounds underwent domino cyclization to give benzohydrindenones in near-quantitative yield and with complete diastereoselectivity. Reaction: see text.
- Browder,Marmsaeter,West
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p. 3033 - 3035
(2007/10/03)
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- New aspects in the synthesis of mono- and dialkylfurans
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3-substituted furan systems can be obtained by alkylation of 3-lithium furans with various electrophiles in the presence of hexamethylphosphoric acid triamide in good yields. The 2- or 5-position of 3-methyl furan is blocked with high regio selectivity by silylation. After metalation and alkylation of the remaining free α-position and subsequent desilylation the 2,3- and 2,4-disubstituted furans are obtained. These methods are used to synthesize the naturally occuring compounds ursinanolide (2) and longifolin (4).
- Bock, Inge,Bornowski, Hans,Ranft, Andreas,Theis, Heinz
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p. 1199 - 1210
(2007/10/02)
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- A CONVENIENT SYNTHESIS OF PERILLENAL
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A convenient synthesis of chemically and stereoisomerically pure trans-perillenal is described.The compound has been prepared according to a simple procedure from methyl (2E)-5-(3-furyl)-2-methylpent-2-enoate obtained by alkylation of copper dienolate of tiglic or angelic acid with 3-(bromomethyl)furan.
- Bernasconi, Silvana,Colombo, Maristella,Jommi, Giancarlo,Sisti, Massimo
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- Photooxidation with Simultaneous Reduction of Hydroperoxides with Tetrabutylammonium Borohydride. Synthesis of Perillenal from Myrcene
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The synthetic routes to 2-methyl-5-(3-furyl)-2-pentenal, perillenal (1), starting from 2-methyl-6-methylene-2,7-octadiene, myrcene (2), are described.Myrcene (2) was either photooxidized to a mixture of the allylic alcohols 3 and 4 or converted to the aldehyde 11 by oxidation with selenium dioxide followed by chromium trioxide dipyridine in acetic acid.The alcohols 3 and 4 and the aldehyde 11 were cyclized with singlet oxygen to the endoperoxides 5, 6, and 12, respectively.The endoperoxides were converted to the furans 7, 8, and 1 by treatment with Fe(II).The secondary allylic furan 8 was converted to perillenal (1) by a one-step reaction involving an allylic rearrangement and an oxidation with pyridinium chlorochromate in the presence of p-toluenesulfonic acid in dichloromethane.A method for photooxidation and simultaneous reduction of hydroperoxides with tetrabutylammonium borohydride is presented.
- Baeckstroem, P.,Okecha, S.,Silva, N. de,Wijekoon, D.,Norin, T.
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