A novel, practical, and efficient three-step process
for the preparation
of 4,5-dichloroindole 5, an important starting material
for a wide range of fine chemicals and pharmaceuticals has been developed.
The process comprises nitration of commercially available 2,3-dichlorobenzaldehyde 1, a telescopic process for the Henry reaction, and subsequently
reductive cyclization of resulting o,β-dinitrostyrene
intermediate 4 into 4,5-dichloroindole using iron powder
in methanol and acetic acid by the Nenitzescu reaction. The large-scale
applicability of this novel and improved process has been successfully
demonstrated on a multikilogram scale by carrying multiple batches
to produce 5 in 67–70% yields and 96–98%
purity without column chromatography. The reactions are facile, safe,
and easy to scale up.
An efficient route for the synthesis of a wide range of new O‐, N‐, and S‐containing spiro heterocycles via reactions of readily available malononitrile (III) with active methylene or bidentate compounds is presented.
2-aryl indoles and some fused indole derivatives were synthesized from the condensation of 2-(4-Hydrazino-phenyl)-ethanesulfonic acid methylamide hydrochloride with different types of aryl ketones. The target molecules were afforded via hydrazone intermediate formed in situ under one-pot tandem microwave protocol or conventional method using isolated hydrazone intermediate on acid catalyzed cyclization. The antibacterial activity of the synthesized compounds in vitro were screened against two Gram-positive and two Gram-negative bacteria Staphylococcus epidermidis, Bacillus subtilis, Pseudomonas aeruginosa and Proteus vulgaris respectively.
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