4.5- dicyano-l,3-dithiol-2-one

For larger amounts we recommend the gas-phase pyrolysis of 4,5-dicyano-l,3-dithiol-2-one (8) [Eq. (3)], which is readily available from sodium cyanide, carbon disulfide, and phosgene [16]. Both the starting materials and most of the pyrolysis products are extremely toxic, and the price to be paid for large-scale production is hence high. 

A second route to TTF derivatives involves desulphurization of l,3-dithiole-2-thiones (or, better, deselenization of 2-selones see below) with phosphines or phosphites. For the preparation of tetracyano-TTF (54 R = CN), the use of triphenyl phosphite is recommended alternatively, 4,5-dicyano-l,3-dithiole-2-one is reported to be deoxygenated in high yield by trimethyl phosphite. ... 

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