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12th February 2012 @ 22:35
START: 13/02/12
FINISH: 16/02/12

Background
Preparation for the imidobis(sulfuryl chloride) component for use in the synthesis of racemic 1,1'-Binaphthyl-2,2'-bis(sulfuryl)imide.[1]

Scheme%20KAB15-1.png
Table%20KAB15-1.png

Hazard and Risk Assessment
HRA KAB15-1.pdf


Following Experiments
Synthesis of 1,1'-Binaphthyl-2,2'-bis(sulfuryl)imide·1/2Et2O (KAB16-1)

Procedure
All glassware was oven dried prior to the start of the procedure.

14/02/12 - A condensing tube was attached to a 3-necked flask before the system was flushed with argon gas. Sulfamic acid (3.0 g) was added to the flask before the dropwise addition of thionyl chloride (6.2 mL) then chlorosulfonic (2.0 mL). The clear, colourless solution gradually turned brown on addition of the chlorosulfonic acid. The reaction mixture was slowly warmed to 76 °C and reached temperature at 12:00, then left to reflux under argon for 24 hours.
Before the addition of HSO3Cl
Reflux setup
Reaction mixture (<10 min)


15/02/12 - The reaction mixture was allowed to cool to rt at 12:00. Distillation of the product was attempted directly out of the reaction vessel, following attachment of oven dried distillation apparatus. Maximum vacuum of the pump was measured at 0.630 mmHg.
Distillation setup

The distillation included set-up of a secondary cold-trap (liq. N2 then acetone/dry ice). The vacuum was turned on and the reaction mixture gradually warmed to 35 °C, upon which it immediately started bumping. What was assumed to be excess thionyl chloride rapidly condensed in the secondary trap. The temperature of the head-space above the reaction mixture was 29 °C.
The reaction mixture was gradually heated to 70 °C. And the internal temperature remained at 29 °C. No further condensation was observed at this stage. A cold-finger (dry ice) was attached at the joint between the claisen head and the condensation tube. Gentle heating of the claisen with a heat gun resulted in little to no condensation. The inside surface of the reaction flask, where oil was previously deposited was covered with small colourless crystals.
The set-point temperature of the oil bath was increased to 100 °C. No condensation occurred. Some oil was visible in the tube connecting the condensing tube to the secondary trap. On closer inspection, the silicon tubing appeared to have corroded somewhat and "glued" shut, effectively cutting off any vacuum - which may be why no condensation occurred. It is uncertain at what stage the tube was compromised. Under inert gas, the collapsed section was removed and the tube reattached.
Collapsed tube
Same collapsed tube the following day.

It was thought that the attached cold-finger may have caused condensation of product at that cold spot, cutting off any vacuum. The cold finger was removed, revealing a yellow-green, frozen oil, which rapidly melted and spread along the condensing tube. Aiding of the distillation was further attempted by gently heating the claisen with a heat gun.
The set point of the reaction mixture was increased to 140 °C. At this point, the internal temperature of the reaction flask increased to slightly more than 40 °C. The white crystals that were thought to be product began to melt. Condensation was observed in the claisen.
At this point, the silicon tube, connecting the distillation set-up to the secondary trap, failed in several spots. Moisture from the air was sucked into the dry environment, which reacted with the gas present in the closed system turning it cloudy. The reaction was aborted and the tubing was removed, the vacuum turned off and the set-up flushed with nitrogen.
Second compromised tube.
Reaction mixture reacting with air

The set up was left under argon gas overnight. 1H-NMR of the reaction vessel contents is scheduled for tomorrow.
KAB15-1


16/02/12 - Recorded 1H-NMR suggested the contents of the flask was not the expected product. KAB15-1 was taken no further. The flask was quenched and the product disposed of.


Considerations for future attempts
Distillation setup

- Shorter condensing tube (non-water), fitted with dry ice trap.
- Another cold trap before the point of connection for the vacuum/nitrogen line.

References
[1] A. Berkessel, P. Christ, N. Leconte, J. M. Neudorfl, M. Schafer, Eur. J. Org. Chem. 2010, 5165. DOI: 10.1002/ejoc.201000810.

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NOTES 13/02/12
- Glassware in the oven (105 °C) from 09:00.

NOTES 14/02/12
- Reflux @ temperature for 24 hours from 12:00.
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Linked Posts
Attached Files
Table KAB15-1.png
HRA KAB15-1.pdf
Scheme KAB15-1.png
Before the addition of HSO3Cl
Reaction mixture (<10 min)
Reflux setup
Flushing distillation apparatus with argon
Distillation setup
Collapsed tube
Same collapsed tube the following day.
Second compromised tube.
Reaction mixture reacting with air
KAB15-1
Distillation setup
Comments
Re: Preparation of Imidobis(sulfuryl chloride) (KAB15-1) by Matthew Todd
12th February 2012 @ 23:00
Safety clearance: Process discussed with Kat 10 a.m. 13/2/12. Discussed procedures to minimize hazards associated with water-sensitive and corrosive reagents, method to purify product with distillation and method for quenching reaction upon completion. Postdoc Murray Robertson to supervise hazardous procedures.