Concave Reagents 32: syn- and anti-Selective Cyclopropanation of Alkenes with Diazoacetates Catalyzed by Copper (i) Complexes of Concave 1,10-Phenanthrolines
31 December 1999 (online)
Two classes of concave 1,10-phenanthroline ligands 1 and 2 have been used in the copper(i) catalyzed cyclopropanation of several acyclic and cyclic alkenes 3 with three diazoacetates 4-6. The bimacrocyclic 2,9-diaryl-1,10-phenanthrolines 1 favor the anti-(trans- or exo-) cyclopropanation with anti/syn-selectivities of up to >99 : 1 (8g). In contrast, with the 1,10-phenanthroline bridged calixarenes 2 as ligands a rarely observed syn-selective cyclopropanation was achieved. Methyl diazoacetate (6) showed the best syn-selectivities with anti/syn-ratios of up to 14 : 86 (9g).
copper(i) complexes - homogenous catalysis - molecular recognition - macrocycles - calixarenes