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5th March 2012 @ 06:54
This procedure is intended aas an improvement upon JRC 5-1 and JRC 5-2, using titanium (IV) chloride and triethylamine in place of sodium ethoxide (or methoxide). This procedure is adpapted from that which is described by Deshmukh et al. (2006), and it is summarised below.

2101.png

Reaction start time: 5pm (5/3/2012)
A solution of 1M TiCl4 in toluene (1.148 mL, 1.148 mmol, 0.85 equiv.) was stirred under a nitrogenous atmosphere and to this, JRC 4-2 (0.344 mL, 1.36 mmol, 1 equiv.) in dried DCM (5 mL) was added dropwise. After 15 stirring at this temperature, triethylamine (0.188 mL, 2.992 mmol, 2.2 equiv.) was added dropwise. Solution became a dark violet colour with intense fuming upon addition. Reaction was then left for 1.5 hr. TLC at this point showed very little starting material remaining.

TLC (+1.5 hr): 10% ethyl acetate/hexane (visualised with UV/vanillin):
JRC 7-1.JPG


Reaction was quenched after 2 hr with 10% sodium chloride in water (15 mL). The violet organic layer separated easily from the aqueous layer. The entire mixture went orange and afforded an orange/cream precipitate upon basification (~pH 9-10) with triethylamine.

The following morning the precipitates were filtered off and washed with DCM (30 mL). The filtrate was washed with additional DCM (30mL), which produced white fumes upon addition to the reaction mixture. The combined organic layers were dried with MgSO4 before the solvent was removed in vacuo to yield a brown oil (0.337g). 1H-NMR revealed starting material along with triethylamine.

Risk Assessment (paper copy signed):
JRC 7-1.pdf


Linked Posts:
Upscaled synthesis of ethyl β-(carbethoxymethylthio)propionate (JRC 4-2)
Synthesis of 2-Ethoxycarbonylthiolan-3-one (JRC 5-1)
Synthesis of 2-Ethoxycarbonylthiolan-3-one (JRC 5-2)

References:
Deshmukh, M. N.; Gangakhedkar, K. K.; Kumar, U. S., Regioselective Titanium Tetrachloride Mediated Five Membered Hetero-Cyclisations. Synthetic Communications 1996, 26 (9), 1657-1661.
Linked Posts
Attached Files
JRC 7-1.pdf
JRC7-1summary.png
JRC 7-1.JPG
JRC7-2scheme.png