Concave Reagents 32: <i>syn</i>- and <i>anti</i>-Selective Cyclopropanation of Alkenes with Diazoacetates Catalyzed by Copper (i) Complexes of Concave 1,10-Phenanthrolines
作者:Frank Löffler、Martin Hagen、Ulrich Lüning
DOI:10.1055/s-1999-3171
日期:1999.11
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 calix[6]arenes 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).
introducing a tolyl or phenyl ligand at the apical position, respectively, via the S(E)Ar mechanism, and they were found to be efficient catalysts for cis-selective asymmetric cyclopropanation. The scope of the cyclopropanation was wide, and the reactions of not only conjugated mono-, di-, and trisubstituted olefins but also nonconjugated terminal olefins proceeded with high enantio- and cis-selectivity