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Dehydration of 3,4-dihydro-5H-Benzo[cd]pyren-5-ol; 6H-Benzo[cd]pyrene

SyntheticPage 542
DOI: 10.1039/SP542
Submitted Mar 15, 2012, published May 31, 2012
Anish Mistry (a.mistry@warwick.ac.uk)
A contribution from Fox Group, Warwick University


			Reaction Scheme: <img src="/images/empty.gif" alt="" />Dehydration of <span id="csm1338478969479" class="csm-chemical-name" title="3,4-dihydro-5H-Benzo[cd]pyren-5-ol">3,4-dihydro-5H-Benzo[cd]pyren-5-ol</span><img src="/images/empty.gif" alt="" />

Chemicals Used

3,4-dihydro-5H-Benzo[cd]pyren-5-ol (prepared)
Amberlyst 15 (Sigma-Aldrich)
Chloroform

Procedure

3,4-dihydro-5H-Benzo[cd]pyren-5-ol (0.1 g, 0.39 mmol) was dissolved in chloroform (30 ml) and Aberlyst 15 (0.1 g) added under a dinitrogen atmosphere. The reaction was heated to 30oC and left overnight under the inert atmosphere. The solution was then filtered to seperate the Amberlyst and washed with chloroform. The combined solvents were removed under vacuum using a Rotary evaporator. The crude product was column chromatographed under a dinitrogen atmosphere eluting with 1:1 chloroform:petroleum ether 40-60oC. A white solid was obtained using this method (50 mg, 54%).

Author's Comments

  • Degradation of product occurs on the column. The use of a dinitrogen atmosphere slows this down. Firstly the eluent and column were purged using dinitrogen gas, after the crude mixture was loaded on the purged column a continous flow of dinitrogen gas was used for flash chromatography via a nitrogen line.
  • The chloroform was washed with sodium bicarbonate before column chromatography.
  • The white product on exposure to air became yellow then orange in colour.

Data

δH(400MHz, CDCl3) ppm: 5.00 (2H, s, -CH2), 7.46 - 7.55 (4H, m, aryl), 7.72 - 7.84 (6H, m, aryl).

Supplementary Information

Proton NMR shows the symmetric dihydrogen species as the major product, the small peaks which can be observed in the spectrum (around 2, 3.5 ppm and aromatic region) are presumably other isomers of the compound.
1H NMR spectrum of Olympicene - Click to view
1H NMR (Jan11-2012.dx)

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Get structure file (.cdx, .sk2, .mol)

Keywords: aromatics/arenes, dehydration

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