C.A. Morales Olefin Addition Rxns in Polyether Synthesis-2 Chem 206 A biomimetic model for syn-oxidative polycyclization: But for secondary alcohols -Pr PCC HOAC PCC HOAC 9%combined, 11: 1(trans cis Conformational model for syn-oxidative cyclization HR 38%,99:1 RE OH O OH Rz Does this explain the lower degree of trans-cross-ring" selectivity observed for(Er-olefins? HOAC R 19%combined, 3.7: 1( trans cis reductive RE OH trans-substituted 24%.17:1 tetrahydrofuran High syn-stereospecificity for tertiary alcohols McDonald. F E. JACS. 1994. 116.7921Me OH Me Me Me Me PCC HOAc Me OH Me Me Me Me PCC HOAc O O H Me Me Me O O O H Me Me Me O OH O O H Me H Me Me Me Me OH O O H Me H Me Me Me Me OH O O H Me H Me Me Me Me OH O O H Me H Me Me Me Me O RS RL H RZ RE OH O Cr H RZ RE RL RS H H O O OH i-Pr OH Me Me Me PCC HOAc O Cr RL RS H H O O OH H RE RZ O Cr RL RS H H O OH H RE RZ O O H i-Pr Me O Me C. A. Morales Olefin Addition Rxns in Polyether Synthesis-2 Chem 206 A biomimetic model for syn-oxidative polycyclization: McDonald, F. E. JACS, 1994, 116, 7921. 9% combined, 11:1 (trans:cis) 38%, 9.9:1 19% combined, 3.7:1 (trans:cis) 24%, 17:1 High syn-stereospecificity for tertiary alcohols But for secondary alcohols... ...simple oxidation occurs more rapidly than oxidative cyclization. Conformational model for syn-oxidative cyclization: [2+2] reductive elimination trans-substituted tetrahydrofuran Does this explain the lower degree of "trans-cross-ring" selectivity observed for (E)-olefins?