Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States.
Org Lett. 2011 May 6;13(9):2180-3. doi: 10.1021/ol200390j. Epub 2011 Mar 29.
Intramolecular photocycloaddition (>290 nm) between a 1,3-enyne and a 2-pyridone is far more selective than the intermolecular version; a three-atom linkage both controls regiochemistry and separates the [2 + 2] and [4 + 4] pathways. All four head-to-head, head-to-tail, tail-to-head, and tail-to-tail tetherings have been investigated. Linkage via the ene of the enyne leads to [2 + 2] products regardless of alkene geometry, whereas linkage through the yne results in [4 + 4] cycloadducts. The bridged 1,2,5-cyclooctatriene products of [4 + 4] cycloaddition are unstable and undergo a subsequent [2 + 2] dimerization reaction.
分子内 1,3-炔与 2-吡啶酮之间的光环加成（>290nm）比分子间的版本选择性高得多；三原子键合不仅控制区域化学，而且分离[2+2]和[4+4]途径。已经研究了所有四种头对头、头对尾、尾对头和尾对尾键合。通过炔的烯进行键合导致[2+2]产物，无论烯烃的几何形状如何，而通过炔进行键合则导致[4+4]环加成产物。[4+4]环加成的桥连 1,2,5-环辛三烯产物不稳定，并经历随后的[2+2]二聚反应。
