Pyrazole derivatives R 0180Synthesis and Antibacterial Activity of 1,3-Diaryl-4-cyanopyrazoles. -Compounds (IVc) and (IVd) exhibit high antibacterial activity comparable to that of commercial antibiotics, linezolid and ciprofloxacin. -(PRAKASH*, O.; PUNDEER, R.; RANJAN, P.; PANNU, K.; DHINGRA, Y.; ANEJA, K. R.; Indian J.
Oxidation of 2,5-dihydroxyacetophenone with iodobenzene diacetate (IBD) in different alcohols leads to regioselective alkoxylation, thereby providing a new and convenient route for the synthesis of 6-alkoxy-2,5-dihydroxyacetophenones.In connection with our ongoing studies on the use of organoiodine(III) reagents in organic synthesis, 1,2 we have earlier reported that hypervalent iodine oxidation of mdihydric phenolic compounds bearing electron-withdrawing ketonic moieties such as COCH 2 R leads to a novel route for the synthesis of o-iodo ethers (Scheme 1). 3 The reaction, providing a unique application of organohypervalent iodine reagents, occurs via rearrangement of iodonium ylides leaving the enolizable ketone moiety intact. In continuation of these encouraging studies, we have now examined the oxidation of 2,5-dihydroxyacetophenone (1) with iodobenzene diacetate [IBD or PhI(OAc) 2 ] in different alcohols.
Scheme 1The aim was to ascertain the influence of the change of position of the phenolic hydroxy group 1 on the course of this reaction and hopefully to develop a new and facile approach for the synthesis of 6-alkoxy-2,5-dihydroxyacetophenones 2 which have potential use in synthesis. Thus, 1 was treated with IBD (1.1 equiv) in methanol at room temperature. The usual work-up, followed by column chromatographic separation of the crude product afforded 2,5-dihydroxy-6-methoxyacetophenone (2a) in 48% yield. To test the scope of this method, 1 was subjected to oxidation with IBD in several alcohols, namely, ethanol, propan-1-ol, propan-2-ol, butan-1-ol, 2-methoxyethanol and 2-ethoxyethanol. The reaction, indeed, gave the corresponding 6-alkoxy derivatives 2a-g in moderate yields (Scheme 2).
Scheme 2
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