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Indium Triflate Catalyzed Rearrangement of Aryl-Substituted Cyclopropyl Carbinols to 1,4-Disubstituted 1,3-Butadienes

Brindaban C. Ranu *, Subhash Banerjee

*Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India, Email: ocbcriacs.res.in

B. C. Ranu, S. Banerjee, Eur. J. Org. Chem., 2006, 3012-3015.

DOI: 10.1002/ejoc.200600037


Abstract

Aryl-substituted cyclopropyl carbinol derivatives undergo a facile stereoselective rearrangement catalyzed by In(OTf)3 in dichloromethane under sonication to produce the substituted conjugated all-trans-butadienes.

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Details

The paper discusses the indium triflate (In(OTf)3) catalyzed rearrangement of aryl-substituted cyclopropyl carbinols to 1,4-disubstituted 1,3-butadienes. This reaction is performed in dichloromethane under sonication, offering a stereoselective synthesis of conjugated all-trans-butadienes. The procedure is simple, involving sonication of cyclopropyl carbinols with 10 mol-% of In(OTf)3, followed by extraction and purification. The reaction is efficient, yielding high-purity products in 25-45 minutes. The method is advantageous due to its operational simplicity, mild conditions, and high yields (80-95%). The study highlights the importance of indium reagents in organic synthesis, particularly for carbon-carbon bond formation and rearrangements. The reaction mechanism likely involves the polarization of the C–O bond by the Lewis acid, facilitating the cleavage of the cyclopropyl moiety and formation of the benzylic carbonium ion, leading to the diene. This method is free from the limitations of other diene synthesis methods, such as stability and toxicity of catalysts, and offers high stereoselectivity and operational simplicity. The research was supported by CSIR, New Delhi, and the findings contribute to the development of efficient synthetic protocols in organic chemistry.


Key Words

Carbinols, Homogeneous catalysis, Indium, Rearrangement, Sonication, 1,3-Dienes


ID: J24-Y2006-2060