Author Topic: Thiocyanation of 2C-H -Rhodium  (Read 7945 times)

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Thiocyanation of 2C-H -Rhodium
« on: April 24, 2000, 11:58:00 PM »

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Author  Topic:   Thiocyanation of 2C-H 
Administrator   posted 10-30-1999 04:36 PM          
Assholium wrote the following while we were talking about 2C-B many moons ago:
"Monobrominate, you say. What about thiocyanate? - just add in soln 1.2 eqv of KSCN and then dropping bromine. This will be very fun product."

What does he mean?

KSCN + Br2 => KBr + BrSCN
BrSCN + 2C-H => 2C-SCN + HBr

Or something to that effect? Drone?

Member   posted 10-31-1999 09:51 AM          
No, it doesn't work like that. But close.
2 SCN(-) + Br2 --[in situ]--> (SCN)2 + 2Br(-)

The (SCN)2 reacts with the aromatic nucleus:

ArH + (SCN)2 -----> ArSCN + HSCN

Since the pseudohalogenide (SCN)2 tends to polymerise, it is usually produced in situ, by reaction of ammonium or alkali thiocyanates and Br2 or Cl2. It can be used to introduce the SCN moiety into aromatic rings at or below RT.

This reaction can be done with phenols, phenol ethers, aromatic amines, condensed aromatics (like anthracene), some heterocycles and compounds with an acidic CH bond. Substituents like -NO2, -X, -COOH, -COOR may be present, as long as a free position o or p towards the donor substituent exists. The SCN enters in p preferentially, when it is already occupied, o substitution takes place.
Suitable solvents include glacial acetic acid, formic acid, MeOH or MeOAc saturated with NaBr or NaCl. Thiophenols are accessible by basic melt hydrolysis.

General procedure:
0.1 mol of the aromatic substance and 0.22 mol thiocyanate are cooled in 75ml glac. acetic acid to 10-20°C. 0.1mol Br2 in 25ml AcOH are added dropwise with good stirring, keeping the temp below 20°C. Let stand for 3hrs. at RT, pour into an excess of ice water, neutralise while cooling in an ice bath, extract or filter the precipitated product and purify by crystallisation from aq. alcohol. Yields typically 60-90%.

Administrator   posted 10-31-1999 10:25 AM          
Hey, that's pretty slick! I wonder why it isn't mentioned in Pihkal...
Administrator   posted 10-31-1999 10:30 AM          
And I also wonder why this thiocyanation method isn't mentioned in March's Advanced Organic Chemistry...
Member   posted 10-31-1999 11:39 AM          
Yup, when I saw your post the first thing I did was grabbing March. I knew it was in one of my books, but most, including March, don't mentioned it. Finally found it in an old East German book.
Regarding the pharmacology and toxicity, a certain Russian bee whose name shall remain a secret to protect the researcher has tried an ethoxylated analogue (2-EtO,5-MeO, 2 carbon homologue I think, but don't remember for sure). He said it was long acting, but not a recreational substance. Not child-like joy, but more adult-like seriousness. Don't remember his words exactly. Amount ingested was in the tens of mg (20? 30? don't quote me on that, it's more than a year ago), so potency seems to be retained. Regarding toxicity, thiocyanate is a natural metabolic product of the human body, found in urine, so it shouldn't be too dangerous to use.

Member   posted 11-01-1999 06:18 PM          
Since our Russian bee isn't around anymore, I'll post some more. I guess it's ok. None of this was done by me, it's all his work and words:
" ...But I still had some 2-EtO-5-MeO-PEA in my hands. After long thinking I decided - why not make some thio analogue from this useless shit? Just by adding 1.2 equiv. of NaSCN to the usual Shulgin bromination! So some red-brown tar was obtained. This shit don't want to deposit from acetic acid like 2C-B, and only tar deposited. After acid-base treatment a few grams of yellow crystalline solid with a mp of 170-175°C as the hydrochloride was obtained. Thoughts about distillation were discarded. I knew that thiocyanates don't survive distillation without regrouping into isothio-"mustard oils" (possibly interesting compounds, too, but not for present investigation). And ingestion of 30mg shows very fun feelings. Intense eyes-closed visuals, visual distortion and so on. But there was no 2C-B at all, not 2C-B fun kid's excitement, but adult's neutralness and seriosity. ..."

Administrator   posted 11-02-1999 09:58 AM          
Ok, thanks. But we all know that the tweetios are inferior to the 2C-X counterparts, so it still seems kinda interesting.
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