Concave 1,10‐Phenanthrolines as Tailored Ligands for Copper(I)‐Catalyzed Diastereoselective Cyclopropanations
Alkenyloxy-substituted aryl bridgeheads have been connected to 2,9-dichloro-1,10-phenanthroline (11) either by Suzuki coupling or by nucleophilic aromatic substitution. The resulting di- or tetraalkenes 12 or 17 have been cyclized by ring-closing metathesis to give concave 1,10-phenanthrolines 14 and 19, differing from other concave 1,10-phenanthrolines 1 in their geometries. The influence of the shapes of these ligands and those of the related concave 1,10-phenanthrolines 1a–f and 2 on the stereochemistry of the copper(I)-catalyzed cyclopropanation of indene (3) and styrene (4) has been investigated, identifying factors that favour the formation of thermodynamically less stable syn-cyclopropanes 6 and 7. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)