Synthesis of unsymmetrically substituted TTF derivatives via the "phosphonate way". Some investigations on the scope of the method.

The scope and limitations of the synthesis of unsymmetrically substituted T TF derivatives via the "phosphonate way" was investigated using as precurso rs 1.3-dithiol-2-yl-phosphonates and 1.3-dithiol-2-yliden iminium salts wit h various substituents on the dithiole cycles. Except for the un- or monosubstituted phosphonates. the one-pot procedure p roves to be general and affords in all cases a significant improvement in t he overall yields in TTF derivatives. The study has shown also that the formation of the intermediate adducts occ urs in high yield, but their transformation into TTF derivatives, in presen ce of anhydrous acetic acid is strongly sensitive to the nature of the vari ous substituents. particularly on the iminium part (C) 1999 Elsevier Scienc e Ltd. All rights reserved.