Dearomative Addition of Carboranyl Anions to Isoquinolinium Salts and Subsequent Reduction to Access Carborane‐Functionalized Dihydroisoquinolines

A dearomative addition of readily available carboranyllithium reagents to isoquinolinium salts gave a series of carborane cage C‐substituted 1,2‐dihydroisoquinolines in 43−85% yields. Subsequent hydrogenation enabled the facile synthesis of corresponding carboranyl 1,2,3,4‐tetrahydroisoquinolines in 65−95% yields. The addition‐reduction pathway is applicable to a wide range of substituted isoquinolinium salts and o‐carborane or m‐carborane.