Eine einfache Methode zur Herstellung von Benzoxazolen

Abstract

A Facile Method for the Synthesis of Benzoxazoles The preparation of benzoxazoles by a facile one‐pot reaction is reported. The reaction of carboxylic acids with 2‐chloro‐N‐methyl‐Δ1‐pyrrolinium chloride in an excess of N‐methyl‐2‐pyrrolidone afforded carboxylic acid chlorides which were converted subsequently to their 2‐hydroxyanilides by addition of 2‐aminophenols. Cyclization of the 2‐hydroxy‐anilides at elevated temperatures furnished the benzoxazoles in high yield and purity.

Benzobisoxazole Cruciforms: Heterocyclic Fluorophores with Spatially Separated Frontier Molecular Orbitals

“…Cruciforms 1 – 9 were prepared using a variation of our previously reported two-step protocol (Scheme ). Starting with 2,5-diamino-3,6-dibromobenzene-1,4-diol ( 10 ), dehydrative condensation with carboxylic acids 11 – 13 produced sparingly soluble intermediates 14 – 16 , in which the electronic character of the substituents along the horizontal axis was either neutral ( 14 , phenyl), electron-rich ( 16 , 4-(dimethylamino)­phenyl), or electron-poor ( 15 , pyridyl). Each of the three (crude) intermediates was subjected to microwave-assisted Sonogashira couplings with three different terminal alkynes, phenylacetylene ( 17 ), 4-ethynyl- N , N -dimethylaniline ( 18 ), and 4-ethynylpyridine ( 19 ), to give nine final cruciforms 1 – 9 .…”

Thiophene‐containing compounds with antimicrobial activity

“…Symmetrically azole‐substituted thiophene 285 (Figure 33) is one of the metabolites separated from the ethyl acetate extract of the culture of a Streptomyces strain (G278), which is a marine‐derived actinomycetes isolated from echinoderm Holothuria edulis . [ 259 ] This compound, whose chemical synthesis has been previously reported, [ 260,261 ] was discovered for the first time in a natural source. The selective inhibition of E. faecalis , albeit at a high MIC value (256 μg/ml), was the only information on its antimicrobial activity that was provided in the article.…”

“…[257] Thiophenes 279 and 280 (Figure 33) have been previously isolated from the ethyl acetate-soluble portion of a methanol extract of F. foetida roots, [258] while thiophenes 281-283 and the dihydrothiophene 284 (Figure 33 Symmetrically azole-substituted thiophene 285 (Figure 33) is one of the metabolites separated from the ethyl acetate extract of the culture of a Streptomyces strain (G278), which is a marine-derived actinomycetes isolated from echinoderm Holothuria edulis. [259] This compound, whose chemical synthesis has been previously reported, [260,261] was discovered for the first time in a natural source.…”

Novel Fluorescent Quater‐ and Quinquifurans: Syntheses and Photophysical Properties.

“…Quinquifuran 2 (Scheme 2). We had been successful in using Seha's method [16] for synthesis of a 2-(2-hydroxyphenyl)benzoxaxole from 2-amino-4-t-butylphenol 9 i n one step [11], but we obtained from 5-bromo-2-furoic acid 9 mostly amide 10 . This with boric acid in DBC gave 11.…”