Sauron - 28-6-2007 at 03:52
I have been planning the replication of this Org.Syn. prep for some time and today the project took a major step forward. I received delivery of three
key starting materials
1 Kg N-chlorosuccinimide
500 ml (560 g) 1,2-ethanedithiol
2 Kg Chloroacetic acid
The chloroacetic acid needs to be converted to its acid chloride, which I could not import because of shipping restrictions.
The ethanedithiol and chloroacetyl chloride are condensed to 2-oxo-1,4-dithiane. This is then chlorinated at the 3-position with the NCS. The chloro
compound is then treated with potassium isopropyl xanthate , and the intermediate is cyclized with sulfuric acid. The reaction scheme is shown below.
Finally the compound is dimerized to the charge transfer complex BEDT-TTF using trimethyl or triethyl phosphite. I purchased PBr3 to make the trialkyl
phosphite last year.
The chlorination of chloroacetic acid can be done with (you guessed it) TCT, or, perhaps more advantageously with benzoyl chloride (H.C.Brown method.)
Ethanedithiol stinks to high heaven and induces severe headache so I will handle it in the glove box and perform the first step in there. Afterwards
the glove box will be purged into a caustic scrubber.
[Edited on 28-6-2007 by Sauron]
not_important - 28-6-2007 at 06:31
You are ambitious, messing with ethanedithiol. Whould a scrubber using alkali and peroxide be better, oxidising the thiol groups to sulfonates?
Riffing on a now defunct thread, one use I had for ketene was bromo-acetyl bromide using ketene and bromine, as a way around shipping regulations and
local ordinances that prevented getting the chloro version.
Sauron - 28-6-2007 at 13:41
The regulators are down on chloroacetyl chloride and bromoacetyl bromide because of their application to make lachrymators (the phenacyl halides) via
Friedel-Crafts. They are nasty unplesant beasts in their own right, of course.
That's a little circular as the main use I can think of for bromoacetyl bromide other than above is making ketene the non-pyrolytic way, with Zn.
I was told only one company has import permit for chloroacetyl chloride here and when push came to shove they said shipping required a refrigerated
container. That killed it.
IIRC the more interesting use for ketene (other than the rather mundane making of symmetrical anhydrides) is prep of substituted acetoacetic esters.
Synthetically this opens a whole lot of doors.