[MissPhosgene]

yeah, that is true. However, what I want to know is why Hg(OAC)2 and LiClO4 were also put in the pot.

[AWK]

Authors suggest
PHSCl * Hg(C₂H₃O₂)₂ = PhSOCOCH₃ since starting from  pure (though unstable) PhSOCOCH₃ they got a better yield 70 % with cyclohexene (instead of 50 %  in this method).
Reaction without CH₃CN gave acetate instead of acetimidate.
see also
N. S. Zefirov, N. K. Sadovaja, A. M. Maggerramov, !. V. Bodrikov, and V. R. Kartashov,. Tetrahedron, 31, 2948 (1975)

Use of LiClO4 is disccussed in
Snezana Dalipi, George H. Schmid,. J. Org. Chem., 1982, 47 (25), pp 5027–5029

Edit: formatting corrected.

[MissPhosgene]

Thanks! That's awesome. 

[pacifyer]

I think Hg+ as electrophile adds to the double bond as the first step... 

[MissPhosgene]

Pacifyer I think that's a good possibility. There are a few ways to get a mechanism that looks reasonable.