Unsymmetrically substituted furoxans, XIII. Phenylfuroxancarbaldehydes and related compounds

Abstract

The synthesis and structure of the two isomeric phenylfuroxancarbaldehydes ?a and 7b, of the phenylfurazancarbaldehyde 6 and of the corresponding alcohols 3a. 3b and 5 are reported. Thermal equilibration of the furoxan derivatives and their oxidation to the corresponding carboxylic acids 8a and 8b are also discussed.

Synthesis of oxadiazole-2-oxide analogues as potential antischistosomal agents

“…Gasco and co-workers have studied furoxan and related analogues for many years and have published pioneering work towards their syntheses 15–22. The key step typically involves treatment of the requisite cinnamyl alcohol 10 with sodium nitrate and acetic acid at room temperature to form the corresponding 4-phenyl-3-furoxanmethanol derivative 11 .…”

“…Of note, the sodium nitrate mediate cyclization often gave a mixture of two products 11a and 11b , always favoring the desired regioisomer 11a . The structural assignments were based on known differences in 1 H and 13 C NMR resonances of the methylene group in the 3-position which results from shielding by the N-oxide moiety 15,19. The chromatographic separation of these isomers was typically complex and thus the mixture was carried through and subsequently oxidized using MnO 2 to give the corresponding aldehydes 12 in yields ranging from 12–80%.…”

“…(Scheme 3) As mentioned previously, cyclization of 10 to 11 gives a mixture of isomers, with the minor being 3-phenyl-4-cyano-furoxan 11b (see Scheme 2). However, Gasco showed that heating 11a in refluxing toluene leads to partial isomerization to 11b ,15 allowing access to ample material of the minor isomer to be collected. Carrying through the remaining steps as shown in scheme 2 gave 3-phenyl-4-cyano-furoxan 44 .…”

An expedient synthesis of new 2-(furoxan-3-yl)thiazolidin-4-one derivatives

“…The ethyl cinnamates were subjected to DIBAL-H reduction to yield cinnamyl alcohols 2a-c. Further, the cinnamyl alcohols were treated with aq. NaNO2 in the presence of glacial acetic acid to obtain furoxan methanol derivatives 3a-c. 37 Oxidation of the alcohol functionality of the furoxanmethanols using MnO2 yielded furoxan aldehydes 4a-c in excellent yields. 37 Finally, a one-pot three component reaction of furoxan aldehydes 4a-c with substituted anilines 6a-n and mercaptoacetic acid 5 was achieved by simple heating in toluene at 50 o C to obtain the required furoxan-3-thiazolidinones 7a-n, 8a-n, 9a-n in good yields.…”

Synthesis and Biological Evaluation of 1,2,5-OxadiazoleN-Oxide Derivatives as Potential Hypoxic Cytotoxins and DNA-Binders

“…Chemistry Initially, our strategy to prepare the desired system, bis(1,2,5-oxadiazole N-oxide), consisted in the linking of two previously prepared 1,2,5-oxadiazole N-oxide heterocy-cles [27][28][29] through an adequate bifunctional residue. In this way, compound 4 (Chart 2) was converted into the diphenylbis(oxadiazole) 7 by direct reaction with piperazine.…”