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Regioselective Diels-Alder Reaction of 5-hydroxy-1,4-naphthoquinone with Isoprene at Room Temperature; Tetrahydroanthraquinone

SyntheticPage 800
DOI: 10.1039/SP800
Submitted Oct 13, 2015, published Oct 19, 2015
Jevica Salim (jev340@gmail.com), Andrew J. Smaligo (andrew.smaligo@gmail.com), Steven M. Kennedy (steven.kennedy@millersville.edu)
A contribution from Kennedy Group, Millersville University


			Reaction Scheme: <img src="/images/empty.gif" alt="" />Regioselective Diels-Alder Reaction of <span id="csm1445271606955" class="csm-chemical-name" title="5-hydroxy-1,4-naphthoquinone">5-hydroxy-1,4-naphthoquinone</span> with <span id="csm1445271629230" class="csm-chemical-name" title="Isoprene">Isoprene</span> at Room Temperature<img src="/images/empty.gif" alt="" />

Chemicals Used

5-hydroxy-1,4-naphthoquinone (Alfa Aesar)
Isoprene (Sigma-Aldrich)
Boron triacetate  
Dichloromethane (Alfa Aesar)

Procedure

To a stirred solution of 5-hydroxy-1,4-naphthoquinone (2.09 g, 12 mmol) in dichloromethane (160 mL) was added boron triacetate (2.481 g, 13.2 mmol) at room temperature. The reaction mixture was sealed and allowed to stir for approximately fifteen minutes. Isoprene (3.60 mL, 36 mmol) was then added to the flask via syringe. Upon completion (indicated by TLC), the reaction was quenched by addition of saturated aqueous sodium bicarbonate (160 mL). The aqueous layer was extracted with dichloromethane (4 x 100 mL), and the combined organic fractions were washed with water (3 x 100 mL), brine (100 mL), dried over anhydrous magnesium sulfate, and passed through a celite filter. Removal of the solvent by rotary evaporation yielded the product (5-hydroxy-2-methyl-1,4,4a,9a-tetrahydroanthracene-9,10-dione) as a dark-yellow solid (2.48 g, 86%).

Author's Comments

The dienophile solution turns a blood-red color upon addition boron triacetate, and changes to a dark-brown color upon addition of isoprene. The color changes described may be instantaneous or delayed.  

A small amount of the undesired regioisomer is formed by this reaction. The regioselectivity of this reaction determined by 1H NMR spectrum analysis was 8:1 (see supplementary information). This reaction has been performed from 1 mmol to 12 mmol scale. Each reaction resulted in high yield and good regioselectivity.

Data

1H NMR (400 MHz, CDCl3): 1.72 (s, 3H), 2.15 (d, 1H), 2.32 (d, 1H), 2.42 (d, 1H), 2.56 (d, 1H), 3.27-3.32 (q, 1H), 3.38-3.42 (q, 1H), 5.42 (m, 1H),  12.05 (s, 1H).

 

13C NMR (100 MHz, CDCl3): 23.46, 25.48, 28.38, 46.02, 46.59,  118.22, 123.91, 136.92, 161.73, 197.24, 205.66.

 

  Melting Point: 110.2-112.1 °C

Lead Reference

Hsu, D.; Huang, J. J Org. Chem. 2012, 77, 2659-2666.

Other References

Fringuelli, F.; Pizzo, F.; Taticchi, A.; Halls, T. D. J.; Wenkert, E. J. Org. Chem. 1982, 47, 5056-5065.

Supplementary Information

e.g. Actual NMR spectra (as images or jdx files for interactive spectra), photographs of apparatus, TLC’s or crystals or videos. Please contact the ChemSpider team (ChemSpider-at-rsc.org) for help with this.
1H-NMR_Cycloadduct.png
1H-NMR_periOH.PNG
13C-NMR_Cycloadduct.png
Cycloadduct.JPG

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Keywords: addition, aromatics/arenes, cycloaddition, Lewis-Acid mediated, regioselective

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  • Guest Steven Merwin KennedyMay 24 2016 6:30PMAdditional Reference

    Diels-Alder cycloaddition of juglone derivatives: elucidation of factors influencing regiochemical control Robert K. Boeckman Jr., Terence M. Dolak, Kenneth O. Culos J. Am. Chem. Soc., 1978, 100 (22), pp 7098–7100 DOI: 10.1021/ja00490a070

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