Lithiation at C4 of the indole nucleus is readily directed by several functional groups. The 4-substituted indoles thus obtained are transformed into suitable substrates for metathesis reactions. Ring-closing metathesis effected on these compounds lead to skeletons related to several indole alkaloids.
Methodology for the Efficient Synthesis of 3,4-Differentially Substituted Indoles. Fluoride Ion-induced Elimination-Addition Reaction of 1-Triisopropylsilylgramine Methiodides
作者:M Iwao
DOI:10.1016/00404-0399(50)1197p-
日期:1995.8.14
1-Triisopropylsilylgramine methiodide reacted smoothly with a variety of nucleophiles in the presence of tetrabutylammmonium fluoride to give 3-substituted indoles. The 3,4-disubstituted indoles were efficiently synthesized by sequential use of 4-selective lithiation of 1-triisopropylsilylgramine and this new substitution reaction.
Directed Lithiation of 1-Triisopropylsilylgramine. A Short Access to 3,4-Disubstituted Indoles
作者:Masatomo Iwao
DOI:10.3987/com-92-6185
日期:——
1-Triisopropylsilylgramine was lithiated regioselectively at C-4 by treatment with t-BuLi in ether at 0-degrees-C for 1 h. The lithiated species was trapped with a variety of electrophiles to furnish 4-functionalized gramine derivatives in good yields. Replacement of the triisopropylsilyl protecting group by a methyl group resulted in C-2 selective lithiation under the similar reaction conditions.
Rapid Route to 3,4-Substituted Indoles via a Directed Ortho Metalation−Retro-Mannich Sequence
作者:Brian Chauder、Andrew Larkin、Victor Snieckus
DOI:10.1021/ol017310m
日期:2002.3.1
[GRAPHICS]In the presence of NXS (X = Br, I, Cl), gramine derivatives 1, derived by combined directed ortho metalation (DoM)-cross-coupling sequences, rapidly undergo retro-Mannich fragmentation (2) to afford 3-halo indoles 3 in 37-88% yields. A conceptually new methodology to diverse 3,4-substituted indoles (10, 11, 13) is thereby introduced.