Laboratory of Asymmetric Catalysis and Synthesis, EPFL SB ISIC LCSA, BCH 4305, 1015 Lausanne (Switzerland) http://isic.epfl.ch/lcsa.
Angew Chem Int Ed Engl. 2014 Dec 22;53(52):14575-9. doi: 10.1002/anie.201409450. Epub 2014 Nov 3.
Enol esters are versatile synthetic building blocks which can be elaborated by a wide variety of transformations. The classical synthesis by O-selective enolate acylation often hampers control of the E/Z selectivity with highly substituted substrates. A rhodium(III)/copper(II)-mediated process is reported to provide tetrasubstituted enol esters in a trans-selective fashion. Overall, the reaction consists of a heteroaryl acyloxylation of alkynes. The process is initiated by a rhodium(III)-catalyzed C2-selective activation of electron-rich heteroarenes, such as benzofuran, furan, and thiophene. Upon addition across an alkyne, a transmetalation to copper(II) enables reductive CO bond formation. The transformation allows the three-component couplings of heteroarenes, alkynes, and carboxylic acids. Application of the method in the functionalization of bioactive furocoumarin natural products is also described.
烯醇酯是多功能的合成砌块，可以通过多种转化进行修饰。通过 O-选择性烯醇化物酰化的经典合成方法常常难以控制具有高取代基底物的 E/Z 选择性。据报道，铑(III)/铜(II)介导的过程以反式选择性方式提供四取代的烯醇酯。总的来说，该反应由炔烃的杂芳基酰氧基化组成。该过程由铑(III)催化的富电子杂芳烃（如苯并呋喃、呋喃和噻吩）的 C2 选择性活化引发。在与炔烃加成后，向铜(II)进行转金属化可实现还原的 CO 键形成。该转化允许杂芳烃、炔烃和羧酸的三组分偶联。该方法在生物活性呋喃香豆素天然产物的功能化中的应用也有所描述。
