543. Experiments on the synthesis of Bz-substituted indoles and tryptophans. Part II. Attempted syntheses of Bz-nitro-indoles and -tryptophans. the synthesis of 5-ethoxytryptophan and of 4 : 5- and 6 : 7-benzotryptophan

Abstract

705 is regarded as Part I of this series. t In a personal communication Dr. Hughes informs us that he and his colleagues are in agreement with this conclusion.

The Fischer Indole Synthesis.

“…In several cases arylhydrazones under conditions which normally cause indolization merely undergo geometrical isomerization between the syn and anti forms (CLVI) and (CLVII) (2,119,203,211). Such geometrical isomers of the original arylhydrazones can also be isolated as by-products in successful indolizations (164, 211), and both geometrical isomers of arylhydrazones can be normally indolized under the appropriate conditions (119).…”

One-pot, three-component Fischer indolisation–N-alkylation for rapid synthesis of 1,2,3-trisubstituted indoles

“…of hydroxide) and we suspect that the modest yield of 4n can be attributed to partial decarboxylation: indole 2-carboxylic acids are susceptible to acidic, basic, thermal and microwave-promoted decarboxylation (all evident conditions in this reaction sequence), [44][45][46] and 1 H NMR analysis of the crude reaction mixture revealed the presence of decarboxylated indole. The reaction sequence was unsuccessful with nitrophenylhydrazine (electron poor hydrazones are often unwilling substrates in Fischer indolisation), 47,48 with enolisable ester-based alkylating agents, or with unactivated secondary alkylating agents (see products 4x-z respectively). Given that hindered, secondary electrophiles are documented as challenging substrates for indole alkylation, 37 it is encouraging that a secondary benzyl halide was tolerated in this study, to give indole 4v, albeit in Table 3 Scope of one-pot Fischer indolisation-N-alkylation.…”

Fluorescence Properties of Benz[f]indole, a Wavelength and Quenching Selective Tryptophan Analog

“…Synthesis. Benzindole synthesis was first attempted more than a century ago by Fischer synthesis with acetone 2-naphthylhydrazone and was later improved. , Among the three isomeric benzindoles, benz[ e ]-, benz[ f ]- and benz[ g ]-indoles, the linear benz[ f ]indole is the most difficult to synthesize, because the Fischer indole synthesis methods are not effective in this case. When incorporated in place of indole in tryptophan, the linear benz[ f ]indole moiety offers the best mimic of the side-chain conformation and planar ring system of tryptophan.…”