N. Finne Cationic Cyclizations in the Laboratory Chem 206 Biomimetic Polyene Cyclizations -78℃C,57% Johnson, et aL. JACS 1987. 109 2517 R=CH=CH2 77% 'Pr E.J. Corey, et al. Tetrahedron Lett. 1994, 35, 9149 Cyclization to Form Simpler Bicyclics Johnson, et al. JACS 1987, 109, 5852. R=OAC, R'=CH=CH2 80%, 1 min. i Post cyclization transformation: Johnson Me Johnson, et aL. JACS 1984. 106 1138 Introduction of chiral auxiliaries for C=O groups 2A-09-Synth Appl 12/8/00 8: 48 AMO O Me SiEt3 Me Me CH2 Me O H Me Me HO CH2 Me O H Me Me HO Me Me Me R O OH H2C Me Me Me R O O Me Me R' Me HO CO2iPr PrO2iC CH2 Me RO AcO Me Me R' Me Me Me Me Me Me Me Me HO Cyclization to Form Simpler Bicyclics N. Finney Cationic Cyclizations in the Laboratory Chem 206 Johnson, et al. JACS 1984, 106, 1138. TiCl4 Me Me Me Me Me Me Me Me R = OH, R' = H 20%, 24 hr. R = OAc, R' = CH=CH2 80%, 1 min. TiCl4 –78 °C + –78 °C Johnson, et al. JACS 1987, 109, 2517. Biomimetic Polyene Cyclizations R = H ca. 30% R = CH=CH2 77% 96 : 4 O SiPhMe2 Johnson, et al. JACS 1987, 109, 5852. MeAlCl2 –78 °C, 57% E. J. Corey, et al. Tetrahedron Lett. 1994, 35, 9149. SiEt3 Introduction of chiral auxiliaries for C=O groups Me Me Post cyclization transformation: Johnson O Me O Me O3 Base Me O Me Me Me O3 Base Me O A B B B C D D C 32A-09-Synth Appl 12/8/00 8:48 AM