New macrocyclic bistriazolophanes with thioindigo chromophore

Bi(4-methoxycarbonyl-3-oxothiolan-2-ylidene) derivatives are prepared by oxidative dimerization of 4-oxotetrahydrothiophene-3-carboxylates with either TPAP-NMO or K3[Fe(CN)6]. The products are obtained as mixtures of four diastereoisomers due to (E)- or (Z)-configuration of the C-C double bond and relative syn- or anti-configuration of two stereocenters. The red compounds contain the prototype of the thioindigo chromophore. Their double bond configuration can be switched from (E) to (Z) by visible light. Two propargyl-functionalized thiolane monomers were clicked together by para-bis(azidoalkyl)benzene derivatives with [Cu(μ-OH)(tmeda)]2Cl2 as the catalyst, thus, the subsequent oxidative dimerization yielded macrocyclic triazolophane products with the bi(thiolan-2-ylidene) unit only in relative syn-configuration.