Regiochemistry of Twofold Additions to [6,6] Bonds in C 60 : Influence of the Addend‐Independent Cage Distortion in 1,2‐Monoadducts

Three series of regioisomeric bisadducts of C 60 , namely, C 62 (anisyl) 4 and the mixed systems C 62 (anisyl) 2 ‐(COOEt) 2 , and C 61 (COOEt) 2 (NCOOEt), were synthesized starting from the 1,2‐monoadducts C 61 (COOEt) 2 ( 1 ), C 61 ‐(anisyl) 2 ( 2 ), and C 60 (NCOOEt) ( 4 ) by using the Bingel and Bamford‐Stevens reactions, and nitrene additions. In the case of C 61 (COOEt) 2 (NCOOEt) the complete series of nine possible regioisomers were isolated for the first time. For steric reasons the cis‐1 isomers of C 62 (anisyl) 4 and C 62 (anisyl) 2 (COOEt) 2 were not formed. The transannular [6,6] bonds in the cis‐1 isomer 42 of C 61 (COOEt) 2 (NCOOEt) are closed. The properties and regioselectivities of formation of these bisadducts and their monoadduct precursors were compared with those of the series C 62 ‐(COOEt) 4 and C 60 (NCOOEt) 2 , which we synthesized previously. In the additions to 1, 2 , and 4 the preferred positions of attack are e and trans‐3 for sterically demanding addends (e.g., combinations of C(anisyl) 2 and C(COOEt) 2 ) and cis‐1 , e , and trans‐3 for sterically less demanding addends (e.g., combinations of N(COOEt) and C(COOEt) 2 ). A detailed analysis of the MO structures, the experimental and calculated geometries of monoadduct precursors, and the stabilities of reaction products leads to the conclusion that the addend‐independent cage distortion itself is responsible for the observed regioselectivities of bisadduct formations.