Chebolu, Rajesh ; Kommi, Damodara N. ; Kumar, Dinesh ; Bollineni, Narendra ; Chakraborti, Asit K. (2012) Hydrogen-bond-driven electrophilic activation for selectivity control: scope and limitations of fluorous alcohol-promoted selective formation of 1,2-disubstituted benzimidazoles and mechanistic insight for rationale of selectivity Journal of Organic Chemistry, 77 (22). pp. 10158-10167. ISSN 0022-3263
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Official URL: http://pubs.acs.org/doi/abs/10.1021/jo301793z
Related URL: http://dx.doi.org/10.1021/jo301793z
Abstract
Hydrogen-bond-driven electrophilic activation for selectivity control during competitive formation of 1,2-disubstituted and 2-substituted benzimidazoles from o-phenylenediamine and aldehydes is reported. The fluorous alcohols trifluoroethanol and hexafluoro-2-propanol efficiently promote the cyclocondensation of o-phenylenediamine with aldehydes to afford selectively the 1,2-disubstituted benzimidazoles at rt in short times. A mechanistic insight is invoked by NMR, mass spectrometry, and chemical studies to rationalize the selectivity. The ability of the fluorous alcohols in promoting the reaction and controlling the selectivity can be envisaged from their better hydrogen bond donor (HBD) abilities compared to that of the other organic solvents as well as of water. Due to the better HBD values, the fluorous alcohols efficiently promote the initial bisimine formation by electrophilic activation of the aldehyde carbonyl. Subsequently the hydrogen-bond-mediated activation of the in situ-formed bisimine triggers the rearrangement via 1,3-hydride shift to form the 1,2-disubstituted benzimidazoles.
Item Type: | Article |
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Source: | Copyright of this article belongs to American Chemical Society. |
ID Code: | 100275 |
Deposited On: | 20 Jan 2017 09:09 |
Last Modified: | 20 Jan 2017 09:09 |
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