Tin-Lewis Acidity and Reactivity: Pd/Cu- Cocatalyzed Site-Selective Migita–Kosugi–Stille Coupling of Arylstannanes

Migita–Kosugi–Stille coupling (MKSC) of arylstannanes has proven to be one of the most reliable methods that can be used for constructing various carbon frameworks of organic compounds, being otherwise difficult to be obtained. Cocatalysis of a copper salt is well established in MKSC; however, electronic and structural factors affecting the transmetalation between arylstannanes and a copper salt have scarcely been explored. Herein, we disclose that arylstannanes with high tin-Lewis acidity, high nucleophilicity, or a directing group are apt to undergo transmetalation with a copper salt. The tendency in the transmetalation has been applied to Pd/Cu-cocatalyzed site-selective MKSC by use of perfluoroaryl- and heteroaryl-stannanes, where the transmetalation-active SnBu3 moieties can exclusively be coupled with aryl halides, leaving other SnBu3 moieties intact. Furthermore, tin-Lewis acidity of various arylstannanes, one of the major factors determining the transmetalation activity, can be quantitatively estimated by correlating experimental data (119Sn NMR chemical shifts) with various computed values (fluoride ion affinity, LUMO energy level, global electrophilicity index).