- A versatile synthetic methodology for the synthesis of tryptophols
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Tryptophols have been obtained in high yields by the reduction of 3-substituted-dioxindoles (obtained by the aldol condensation reaction of ketones with isatins or by a modified Knovenagel malonate condensation) using a borane tetrahydrofuran complex. The reported methodology offers distinct advantages over existing methods for the synthesis of these compounds, including consistently greater yields, diastereoselective syntheses and the possibility for the synthesis of a wide range of structurally different tryptophols. The reduction reaction was found to proceed via an intermediate 1,3-diol-oxindole, which was obtained diastereoselectively and, which was subsequently reduced to the corresponding tryptophol.
- Garden, Simon J,Da Silva, Rosangela B,Pinto, Angelo C
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p. 8399 - 8412
(2007/10/03)
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- INDOLE SYNTHESES UTILIZING o-METHYLPHENYL ISOCYANIDES.
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New indole synthesis starting with o-methylphenyl isocyanides such as o-tolyl, 2,4-xylyl, and 2,6-xylyl isocyanide is described. Treatment of o-tolyl isocyanide with LDA in diglyme at minus 78 degree C generated selectively o-(lithiomethyl)phenyl isocyanide in an almost quantitative yield, which on warming up to room temperature was cyclized to indole after aqueous workup. Similarly, 2,4-xylyl and 2,6-xylyl and 2,6-xylyl isocyanides were cyclized to 5-methylindole and 7-methylindole quantitatively. The o-(lithiomethyl)phenyl isocyanides reacted with electrophiles such as alkyl halides and alkylene oxides to give o-alkylphenyl isocyanides, which were cyclized via the lithiation at the orthobenzylic carbon to afford 3-substituted indoles.
- Ito,Kobayashi,Seko,Saegusa
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