| Autor: |
Barber JS; Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States., Styduhar ED; Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States., Pham HV; Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States., McMahon TC; Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States., Houk KN; Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States., Garg NK; Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States. |
| Abstrakt: |
We report the first 1,3-dipolar cycloadditions of 1,2-cyclohexadiene, a rarely exploited strained allene. 1,2-Cyclohexadiene is generated in situ under mild conditions and trapped with nitrones to give isoxazolidine products in synthetically useful yields. The reactions occur regioselectively and exhibit a notable endo preference, thus resulting in the controlled formation of two new bonds and two stereogenic centers. DFT calculations of stepwise and concerted reaction pathways are used to rationalize the observed selectivities. Moreover, the strategic manipulation of nitrone cycloadducts demonstrates the utility of this methodology for the assembly of compounds bearing multiple heterocyclic units. These studies showcase the exploitation of a traditionally avoided reactive intermediate in chemical synthesis. |
