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28th February 2012 @ 04:14
Starting material recovered (90%) cleaner than original.

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Reduction of the un-substituted near-neighbour PMY 14-4 to avoid the deacetylation seen in PMY 36-2.

PMY39-1.png

Reaction Start Time: 14.50 28/02/12
PMY 14-4 (100 mg, 0.25 mmol, 1 equiv.) was stirred in acetonitrile (10 mL, slurry). Material did not dissolve on heating to reflux. MeOH (approx. 5 mL) was added. Dissolved on heating to reflux, precipiated on cooling to room temperature (not completely). Sodium borohydride (approx 50 mg, 1.3 mmol, 5 equiv.) was added, slight exotherm and bubbling observed. After 10 minutes bubbling had ceased, reaction heated briefly to reflux. On cooling, the reaction remained as a solution. TLC 1.5 hours, shows no reaction. Further sodium borohydride (approx 50 mg) was added and the reaction heated to 60 °C. After 20 hours, TLC shows no reaction, yellow colour remains. Water (10 mL) and EtOAc (20 mL) added. The layers separated. The organic layer was washed with water (2 × 10 mL), brine and dried (MgSO4) then concentrated under reduced pressure to a yellow powder (90 mg). 1H NMR shows very clean SM, cleaner than original PMY 14-4. Material to be used for biological testing.

TLC (50% EtOAc/hexane) visualised with UV and vanillin:
TLC 20 hours


NMR:
1H NMR


See also:
Reduction of 4-fluoro near-neighbour Michael-acceptor (PMY 36-2)
Synthesis of 4-Fluoro substituted near neighbour (PMY 14-4)

Risk and Hazard Assessment:
See: Reduction of 4-fluoro near-neighbour Micheal-acceptor (PMY 36-1) and Reduction of pyrrole-3-carbaldehyde using sodium borohydride (PMY 18-1)
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Attached Files
Scheme
TLC 20 hours
1H NMR