Organic Process Research & Development 2003, 7, 339−340
Safety and EnVironmental Reports
Functional Group Transformations of Diols, Cyclic Ethers, and Lactones Using
Aqueous Hydrobromic Acid and Phase Transfer Catalyst under Microwave
Irradiation
Goverdhan L. Kad,* Irvinder Kaur, Monica Bhandari, Jasvinder Singh, and Jasamrit Kaur
Department of Chemistry, Panjab UniVersity, Chandigarh 160 014, India
Table 1. a
Abstract:
Synthesis of bromoalkanols has been achieved from diols,
ethers, and lactones using aq HBr (48%) and tetrabutylam-
monium iodide/bromide as phase transfer catalyst under
microwave irradiation. This environmentally benign route
provides enhanced yields of products and does away with the
use of benzene as compared to existing conventional methods.
Discussion
Bromoalkanols and bromocarboxylic acids are important
intermediates in the synthesis of insect pheromones and other
naturally occurring products, as they provide two reactive
sites for further reaction. After suitable protection of
alcoholic/acidic groups, these compounds can be important
precursors for the formation of C-C bonds1-3 and conversion
to Wittig4 or to a Grignard reagent.5
Various methods have been reported in the literature to
achieve this goal; however, they require reaction of diols
with aqueous hydrogen bromide using a continuous extrac-
tion apparatus employing nonpolar solvents such as cyclo-
hexane5 (72 h) or toluene6 (16 h). Kang et al.7 have prepared
bromoalkanols by refluxing a mixture of diols with 48% aq
HBr in benzene in 40-90% yield; dibromide (13%) and
unreacted diol (2%) were also present.
Now, microwave energy has been used in a wide variety
of reactions,8-12 owing to their high heating efficiencies with
remarkable rate enhancement and dramatic reduction in
* To whom correspondence should be addressed. Telephone: +91-172-
(1) Vig, O. P.; Sharma, M. L.; Sabharwal, A.; Vohra, N. Indian J. Chem. 1986,
25B, 1042.
(2) Vig, O. P.; Sharma, M. L.; Vohra, N. Indian J. Chem. 1986, 25B, 1052.
(3) Vig, O. P.; Sharma, M. L.; Nanda, R.; Puri, S. K. Indian J. Chem. 1985,
24B, 247.
(4) Martinez, A. G.; Ruiz, M. O. Synthesis 1983, 663.
(5) Babler, J. H.; Invergo, B. J. J. Org. Chem. 1979, 44, 3723.
a Analysis was carried out using 1H NMR and IR spectral data.
(6) Mori, K. Tetrahedron 1974, 30, 3807.
(7) Kang, S. K.; Kim, W. S.; Moon, B. H. Synthesis 1985, 1161.
(8) Loupy, A.; Petit, A.; Hamelin, J.; Texier-Boullet, F.; Jacquault, P.; Mathe,
D. Synthesis 1998, 1213.
(9) Bortulussi, M.; Bloch, R.; Loupy, A. J. Chem. Res., Synop. 1998, 34.
reaction times. In continuation to our work on chemoselective
studies in organic synthesis using microwave irradiation,13-15
we report a simple and ecofriendly method for the formation
(10) Trehan, I. R.; Brar, J. S.; Arora, A. K.; Kad, G. L. J. Chem. Educ. 1997,
74, 324.
of bromoalkanols and bromoacids. On treatment with 48%
(11) Sabitha, G.; Subba Reddy, B. V.; Satheesh Babu, R.; Yadav, J. S. Chem.
aqueous hydrogen bromide and tetrabutylammonium iodide/
Lett. 1998, 773.
(12) Varma, R. S.; Saini, R. K. Tetrahedron Lett. 1997, 38, 4337.
bromide (PTC), diols and ethers provided bromoalcohols in
10.1021/op025606h CCC: $25.00 © 2003 American Chemical Society
Published on Web 04/03/2003
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