Heterocumulenes Ketens, Thioketens, etc

The additions of active-hydrogen compounds to the thioketen are believed to proceed via ene-thiols  

Evidently the thioketen is a powerful enophile, so that even propadiene will participate in an ene reaction with it. Since both these reagents are linear, some modification of the usual six-centre cyclic transition state is required, possibly along similar lines to those suggested by Dolbier to rationalize 

The patents by the same author disclose applications for previously reported Diels-Alder adducts obtained from the thioketen and cycloalkadienes, which are useful as anti-arthritic agents, and applications for azine- and carbodi-imide-thioketen adducts for imparting water repellancy to textiles. Further details of patented routes to the precursor from which the thioketen is synthesized (its dimer) have also appeared.  

Sulphur trioxide converts bis(trifluoromethyl)keten at 0 °C into hexa-fluoroisobutenylidene sulphate which exists in equilibrium with 

Bis(trifluoromethyl)keten reacts very readily in non-polar solvents with secondary alkylphosphines and with dialkyl phosphites by P-acylation, reactions which provide easily accessible routes to hexafluoroisobutyryl-phosphines and phosphates. 

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