Shenoy G, Kim P, Goodwin M, Nguyen QA, Barry CE, Dowd CS. Synthesis and Spectroscopic Differentiation of 2- and 4-Alkoxythio-tetronic Acids.
HETEROCYCLES 2004;
63:519-527. [PMID:
16733529 PMCID:
PMC1471896 DOI:
10.3987/com-03-9947]
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Abstract
O-Alkylation of thiotetronic acids gives a mixture of 2- and 4-position enol ether products. Comparison of the physical data revealed that UV spectroscopy was the most reliable method of distinguishing between these related ethers. We have determined that 4-position ethers have a distinct absorption between 235-240 nm, while 2-position ethers have two absorbance peaks, one between 205-220 nm and the other between 305-310 nm. This report describes the synthesis and unambiguous characterization of 2- and 4-methoxy-3,5-dimethylthiotetronic acids. The UV absorption properties of several other pairs of thiotetronic acid ethers confirm that these differences are general features that provide a simple method for distinguishing between 2- and 4-substituted isomers.
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