Krenske Elizabeth H, Houk K N, Lohse Andrew G, Antoline Jennifer E, Hsung Richard P
Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA.
Chem Sci. 2010 Sep 1;1(3):387-392. doi: 10.1039/C0SC00280A.
Chiral oxazolidinones were previously thought to control cycloaddition stereoselectivity by steric crowding of one face of the substrate. We have discovered that in 4+3 cycloaddition reactions of oxallyls, the stereoinduction is caused instead by stabilising CH-π interactions that lead to reaction at the more crowded face of the oxazolidinone. Density functional theory calculations on the 4+3 cycloadditions of oxazolidinone-substituted oxyallyls with furans establish unexpected transition state conformations and a new explanation of selectivity.
手性恶唑烷酮以前被认为是通过底物一个面的空间拥挤来控制环加成立体选择性。我们发现，在草酰烯丙基的4+3环加成反应中，立体诱导是由稳定的CH-π相互作用引起的，这种相互作用导致在恶唑烷酮更拥挤的面上发生反应。对恶唑烷酮取代的氧代烯丙基与呋喃的4+3环加成反应进行的密度泛函理论计算确定了意想不到的过渡态构象，并对选择性给出了新的解释。
