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5th October 2012 @ 12:39
Sc: 1-10
Synthesis of SC3-3 and SC3-4 from SC2-1.


Refer to risk/hazard assessment prepared for SC3-1 and SC3-2.

3rd October 2012

Aim: to repeat SC3-1 and SC3-2.

This experiment is a repeat of SC3-1 and SC3-2. These original products were obtained on 3/9/12 as crude yellow oils. Chromatographic separation yielded the cyclised products expected, plus additional products, as was evident in significant co-spotting observed on TLCs of the fractions. Suspected contamination of the laboratory hexane supply used for the column purification warrants repetition of the reactions. The procedure is described below.

SC2-1 (0.0996 g, 0.34 mmol) was reacted with acetyl chloride (0.05 mL, 0.61 mmol) in the presence of 2,6-lutidine (0.05 mL, 0.48 mmol) in acetonitrile (0.03 M, 13 mL), under argon gas and with stirring for 25 hr, to give SC3-3.
SC2-1 (0.0975 g, 0.33 mmol) was again reacted under the same conditions, with the addition of freshly prepared Yb(OTf)3 (0.0115 g/mL, 1.0 mL, 0.018 mmol) to give SC3-4.

Both reactions changed in hue from colourless to a transparent yellow over the first two hours. Unlike the previous experiment, there were small particles visible in the SC3-4 reaction mixture after 25 hr. This is thought to be Yb(OTf)3. Since the same concentration of Yb(OTf)3 was used in SC3-2 and SC3-4, it is possible that the freshness of the Yb(OTf)3 had an effect on how readily it dissolved in the reaction mixture.

TLC analysis confirmed that both reactions had gone to completion, however, residual lutidine was present, as was the case for SC3-1 and SC3-2.

4th October 2012

Products were extracted in ethyl acetate (10mL) and sodium hydrogen carbonate (10mL). The aqueous layer was twice more extracted in ethyl acetate (i.e. 2 x 10mL). Organic fractions were combined and the solvent was removed using rotary evaporation. Crude products were dark yellow/orange oils.