Dearomative Addition of Carboranyl Anions to Isoquinolinium Salts and Subsequent Reduction to Access Carborane‐Functionalized 1,2‐Dihydroisoquinolines and 1,2,3,4‐Tetrahydroisoquinolines

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. The dearomative addition of carboranyl anions to isoquinolinium salts and subsequent reduction are developed affording carborane‐functionalized 1,2‐dihydroisoquinolines in 43–85 % yields and 1,2,3,4‐tetrahydroisoquinolines in 65–95 % yields respectively. The addition‐reduction (AR) pathway is suitable for various substituted isoquinolinium salts and o‐carborane or m‐carborane, and provides a novel method to access carborane‐functionalized hydroisoquinolines comprising a higher proportion of sp3 carbons.