CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Lingling Road, Shanghai 200032, People's Republic of China.
J Am Chem Soc. 2014 Nov 5;136(44):15607-14. doi: 10.1021/ja5072702. Epub 2014 Oct 22.
Two tunable arylative cyclizations of cyclohexadienone-containing 1,6-enynes are reported via rhodium(III)-catalyzed C-H activation of O-substituted N-hydroxybenzamides. The use of different O substituents, i.e. O-Piv and O-Me, on the directing group allows the formation of either tetracyclic isoquinolones through an Ⓝ-Michael addition process or hydrobenzofurans through a Ⓒ-Michael addition process. Mechanistic investigations of these two cascade reactions clearly indicated that the C-H bond cleavage process was involved in the turnover-limiting step. Furthermore, the cyclization products could be subjected to various transformations for elaborating the pharmaceutically and synthetically valuable potential. This is the first example of a rhodium(III)-catalyzed arylative cyclization reaction of 1,6-enynes, and the results extend the application realm of Cp*Rh(III)-catalyzed C-H activation cascade reactions.
报道了通过铑(III)催化的 O-取代 N-羟基苯甲酰胺的 C-H 活化，实现了含环己二烯酮的 1,6-烯炔的两种可调变芳基环化反应。在导向基团上使用不同的 O 取代基，即 O-Piv 和 O-Me，可以通过 Ⓝ-Michael 加成过程形成四环异喹啉酮，或通过 Ⓒ-Michael 加成过程形成氢化苯并呋喃。对这两个级联反应的机理研究清楚地表明，C-H 键的断裂过程涉及周转限制步骤。此外，这些环化产物可以进行各种转化，以发挥其具有药物和合成价值的潜力。这是首例铑(III)催化的 1,6-烯炔芳基环化反应的例子，其结果扩展了 Cp*Rh(III)催化的 C-H 活化级联反应的应用领域。
