Mash: New Ketals For Directed Cyclopropanation Zn-Cu, CH2l2 Et2O, reflux Substrate Diastereo ratio 13 Ketalization of starting enones proceed in good yields(48-87%) n=2 hp时ge ketal products are 15:1 No mention of stereochemical rationale ash, E; Torok, D J. Org. Chem. 1989, 54, 250 Chiral enol ethers Et2Zn, CH2l2 Et2O, rt Substrates are derived from the appropriate ketals by treatment with FBu3Al n=1 temperatures, Znlz generally slowed the reaction and had variable effects on de 2. K2CO3, MeOH 60% Sugimura, T; Yoshikawa, M; Futugawa, T: Tai, A Tetrahedron 1990, 46, 5955 09B-093/299812:31PMO O Ph Ph O O n n Ph Ph Zn-Cu, CH2I2 Et2O, reflux n = 1 n = 2 n = 3 O O Ph Ph 66 90 77 62 Diastereomer ratio 13:1 19:1 15:1 16:1 Substrate yield • Ketalization of starting enones proceed in good yields (48 - 87%) • Most cyclopropane ketal products are highly crystalline • No mention of stereochemical rationale Mash, E.; Torok, D. J. Org. Chem. 1989, 54, 250 Mash: New Ketals For Directed Cyclopropanation O OH O OH OR OR n n Et2Zn, CH2I2 Et2O, rt n = 0 n = 1 n = 2 n = 3 81 86 77 58 80 57 >99 >99 >99 >99 O >99 i-Pr OH >99 i-Pr Susbstrate Yield d.e. OH 1. PCC 2. K2CO3, MeOH 60% Sugimura, T.; Yoshikawa, M.; Futugawa, T.; Tai, A. Tetrahedron 1990, 46, 5955 Chiral Enol Ethers • Substrates are derived from the appropriate ketals by treatment with i-Bu3Al. • Diastereoselectivity improved with higher temperatures; ZnI2 generally slowed the reaction and had variable effects on d.e. 09B-09 3/29/98 12:31 PM