Cycloaddition of 3-thioxo-1,2-dithioles onto acetylenedicarbaldehyde and its mono-diethylacetal: Ready access to intermediates in the tetrathiafulvalene (TTF) series

Article abstract of DOI:10.1016/0040-4039(93)88074-S

The 4,5-diformyl-1,3-dithiol-2-ylidene ethanals and ethanones 4 are prepared by a three-step sequence from acetylenedicarbaldehyde mono-diEt-acetal and 3-thioxo-1,4-dithioles. Their X-ray diffraction structure, ¹H nmr and IR properties, reveal a δ-cis conformation in the solid state and in solution, due to strong S...O 1,5-internal bonding interactions.