Thiophen Derivatives of Analytical Interest

Thiophen Derivatives of Analytical Interest.—2-Thenoyltrifluoroacetone has maintained its position as a chelating agent in analytical chemistry. Papers describing its use in the extraction or determination of thorium, copper, europium, thallium, niobium, and molybdenum have appeared. The effect of copper(n) on the formation of monothenoyltri-fluoroacetonatoiron(iii) has been studied. The stability constants of some bivalent metal chelates of di-(2-thenoyl)methane have been determined. 3-Thianaphthenoyltrifluoroacetone has been proposed as a reagent for the spectrophotometric determination of iron(iii) and cerium(iv). The stabilities of metal chelates formed from derivatives of thiophen-2-aldehyde and of rare-earth carboxylates of thiophen-2-carboxylate have been studied. 

The separation of thiophen from benzene by solvent extraction has been studied. In connection with gas-chromatographic studies of donor-acceptor complexes, the association between aromatic heterocyclic derivatives, including thiophens, and dibutyl tetrachlorophthalate has been 

3 Thienothiophens, their Benzo-deriyatives, and Analogous Compounds 

Synthesis.—Rearrangement of 2- and 3-(propargylthio)thiophen leads to 2-methylthieno[2,3-6]thiophen (183) and 2-methylthieno[3,2-Z ]thiophen (184). A number of mono- and di-methylthieno[2,3-6]thiophens and thieno[3,2-6]thiophens, such as (284)—(286), were prepared by condensation 

Thieno[2,3- ][l]benzothiophens (293), including the parent compound, were prepared from substituted 2-benzo[Z ]thiophenthiols, obtained from the corresponding lithium derivative followed by condensation with chloroacetaldehyde diethylacetal, chloroacetone, or 3-chlorobutan-2-one, and finally cyclization with hot polyphosphoric acid. For the synthesis of thieno[3,2-6][l]benzothiophens (294), the necessary thiol was 

---