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29th August 2012 @ 02:32
Mnr: 41-50
Attempts To Cyclise KAB22-1 without AcCl
MNR48-1 - Yb(OTf)3 and lutidine
MNR48-2 - Yb(Cl)3 and lutidine

MNR48-1%20scheme.png
MNR48-1-2.PNG

Hazard Assessment
HIRAC MNR41_47_48.pdf


Procedure
To a solution of KAB22-1 (1eq) in HPLC grade acetonitrile (0.03 M) under argon at ambient temperature, was added was added base (1.4 eqs) and catalyst (0.4 eqs). The reaction was then stirred at room temperature (19 °C) for 22 hours.

Work Up


The mixture was washed saturated sodium bicarbonate solution (10 mL) and the aqueous layer was extracted with ethyl acetate (3 × 15 mL). The organic fractions were combined, dried over MgSO4, filtered and concentrated under reduced pressure to yield a yellow oil.

TLC of the crude mixtures showed mainly starting material and lutidine
SANY0239.JPG
SANY0240.JPG


TLCs in 50% EtoAc/Hex.

Column

MNR48-1 was ran through a column using 40% EtOAc/Hex.

The lower runnig spot was isolated in fractions 8-18. on concentration it was clear that there was something wrong as the RBF contained over 1 g of oil/solvent. I turned out that the hexane used was contaminated with kerosene/octane or some other high boiling point organic fraction. Unsure where this came from but other people in the group experienced the same with the previous 24 hours. Bottle identified, returned to stores and taken out of use.

The issolated fraction were taken up in clean hexane and filtered through a plug of silica washing with hexane then EtOAc.

by TLC Fraction 4-7 showed product.

upon drying both flasks contained next to nothing, NMR confirmed this with no distinguishable peaks found. This confirms that the spot was due to lutidine from the reaction which has been lost on the hi-vac.

Conclusions


KAB22-1 can not be cyclised using Yb(OTf)3 or Yb(Cl)3
Attached Files
MNR48-1 scheme.png
MNR48-1-2.PNG
SANY0239.JPG
SANY0240.JPG