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15th March 2012 @ 05:09
This experiment, identical to JRC 7-1, is being repeated in dry conditions. The reaction is based upon the work of Deshmukh et al. (2006), and is summarised below.


Reaction start time: ~ 2pm 15/03/2012
1M Titanium tetrachloride in toluene (1.00 mL, 0.99 mmol, 1 equiv.) was cooled in an ice/sodium chloride bath and JRC 4-2 (0.20 mL, 0.99 mmol, 1 equiv.) in dried DCM (5 mL) was added dropwise. This mixture was left for 20 min before triethylamine (0.30 mL, 2.17 mmol, 2.2 equiv.) was added dropwise. As for JRC 7-1, when the first drop was added the mixture immediately turned a dark violet colour, and white gas was evolved. Further evolution of thick white gas occured as further triethylamine was added. When 1 mL (0.71 mmol) of triethylamine was left to be added no further fuming took place (perhaps all of the protons had been removed at this point?). Reaction mixture caked high up on the walls indicates a fairly exothermic reaction even when conducted carefully at -10°C.

After 2 hr the mixture was poured into a 10% aqueous sodium chloride mixture (10 mL) and made basic with triethylamine (~pH 10). This mixture was left overnight. TLC at this point (+19.5 hr) showed several, probably 2, new products formed in the reaction (with corresponds to literature indications of an aromatic product, and 2 stereoisomers of a non-aromatic product formed.).

TLC +19.5 hr, 10% ethyl acetate/hexane, visualised with UV/potassium permanganate
JRC 7-2 930am 16th.JPG

The precipitate was removed via filtration and the solid washed with DCM (20 mL). This mixture was then extracted with further DCM (20 mL) and the organic layer was washed with water (3 x 10 mL) and brine (3 x 10 mL). In an attempt to overcome the signifiant levels of emulsion present, an aqueous solution of 0.18 M potassium sodium tartrate (6 x 5 mL) was added with each water and brine extraction, though it made seemingly little impression on the levels of emulsion. The combined organic layers were dried over anhydrous magnesium sulfate and the solvent removed in vacuo to yield 0.163 g of crude product (which, as a side note, doesn't seem to smell half as bad as the starting material).

1H-NMR indicated that the desired product was present in mainly keto form, though some enol form was observed.

Crude product was purified over a flash silica column (5% ethyl acetate/hexane).

Fraction 1 (0.004 g)
Fraction 2 (0 g)
Ethyl acetate wash (0.012 g)
Methanol wash (0.010 g)

The remaining fractions were combined and solvent removed to yield 0.015 g material.

Risk Assessment: As for JRC 7-1

Linked Posts:
Synthesis of 2-Ethoxycarbonylthiolan-3-one using titanium (IV) chloride (JRC 7-1)

M. N. Deshmukh, K. K. Gangakhedkar, U. S. Kumar, Synthetic Communications 1996, 26, 1657-1661.
Attached Files
JRC 7-2 930am 16th.JPG