Reasons Why Aldehydes Do Not Generally Participate in Cucurbit[n]uril Forming Reactions
| Authors | |
|---|---|
| Year of publication | 2010 |
| Type | Article in Periodical |
| Magazine / Source | Journal of Organic Chemistry |
| MU Faculty or unit | |
| Citation | |
| Web | http://pubs.acs.org/doi/abs/10.1021/jo100186q |
| Field | Organic chemistry |
| Keywords | cucurbiturils; macrocycles |
| Description | The reaction of substituted glycolurils or a glycoluril dimer with a dialdehyde (o_phthalaldehyde) delivers S_shaped dimers and an S-shaped tetramer selectively. A combination of X_ray crystallography, PM3 calculations, and product resubmission experiments establish that the S_shaped isomers are thermodynamically more stable than the C_shaped diastereomers which we attribute to the conformational preferences of the newly formed benzo bicyclo[3.3.2]decane ring system. The preferential formation of S_shaped subunits is one reason why o_phthalaldehyde and possibly other aldehydes do not usually participate in CB[n] forming reactions. We also present evidence that points toward an equilibrium between glycoluril monomer + phthalaldehyde and S_shaped dimer + water that responds to concentration over the 1_50 mM range. This result suggests a second reason, insufficient reactivity (e.g., low equilibrium constant), why o-phthalaldehyde and possibly other aldehydes do not participate in CB[n] forming reactions. Delineation of the reasons why some aldehydes fail in these reactions is the first step toward devising methods to overcome these limitations. |
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