Stereoselective Access to Conjugated and Cross-Conjugated Dienoates by Rh- and Ru-Catalyzed Isomerizations of Vinylcyclopropanes

Two complementary catalytic protocols for the isomerization of stereoisomeric mixtures of vinylcyclopropanes are described. A commercially available cationic rhodium complex provides access to conjugated dienoates in high yield with excellent stereocontrol. The combination of a bisphosphine ligand and a ruthenium precatalyst affords cross-conjugated dienoates via a formal 1,3-ring opening. The products are obtained with moderate to high stereoselectivity. The ability of each type of dienoate to engage in [4 + 2] cycloaddition reactions has been demonstrated.本研究报道了两种用于乙烯基环丙烷（vinylcyclopropanes）立体异构体混合物异构化的互补催化方案。采用市售阳离子铑配合物，可高产率获得兼具优异立体控制效果的共轭二烯酸酯（conjugated dienoates）。将双膦配体（bisphosphine ligand）与钌预催化剂（ruthenium precatalyst）联用，可通过形式上的1,3-开环路径合成交叉共轭二烯酸酯（cross-conjugated dienoates）。所得产物均具有中等至较高的立体选择性。现已证实，两类二烯酸酯均可参与[4+2]环加成（[4 + 2] cycloaddition reactions）反应。