| Abstract
| - Deprotonation and lithium−bromine exchange in 5- or3-bromothiophene-2-carboxylic acids with t-BuLi form thecorresponding dianion, which reacts highly regioselectivelyin the presence of 0.25 equiv of tetramethyl-1,2-ethylenediamine with 3,6-bis(dimethylamino) chalcogenoxanthonesto give S- and Se-containing rhodamines. Quenching studieswith D2O indicate that an extra equivalent of t-BuLi is notnecessary in these reactions. Deprotonation is faster thanmetal-halogen exchange with the bromothiophene-2-carboxylic acids using t-BuLi.
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