Oxyanion Orientation in Anionic Oxy-Cope Rearrangements
作者:Eun Lee、Yong Rok Lee、Bongjin Moon、Ohyun Kwon、Mi Seong Shim、Jae Sook Yun
DOI:10.1021/jo00085a037
日期:1994.3
Efficiency of chirality transfer in anionic oxy-Cope rearrangement depends solely on the orientational preference of the oxyanionic bond in the substrates with a single carbinol carbon chiral center. In chairlike transition-state conformations for the rearrangement of simplest substrates like anions generated from (E)-1-phenyl-1,5-hexadien-3-ol and (E)-1,5-heptadien-4-ol, the oxyanionic bond is more prone to adopt the pseudoaxial orientation. On the other hand, anions generated from (E)-2-methyl-1,5-heptadien-4-ol, (E)-5-tert-butyl-1-phenyl-1,5-hexadien-3-ol, and 4-(2'-methyl-1'-cyclohexenyl)-1-buten-3-ol undergo rearrangement via chairlike transition states in which the pseudoequatorial oxyanionic bond is favored. It can thus be surmized that there is a slight stereoelectronic preference for the pseudoaxial oxyanionic bond in the chairlike transition states for the rearrangement of substrates without steric constraints. Substitution at C5 of the basic 1,5-hexadien-3-ol framework of substrates, however, leads to 1,3-diaxial steric interaction in the chairlike transition states with pseudoaxial oxyanionic bond, and pseudoequatorial disposition of oxyanionic bond becomes more favorable.
Khandekar, Girish; Robinson, Gareth C.; Stacey, Nicholas A., Journal of the Chemical Society. Perkin transactions I, 1993, # 13, p. 1507 - 1520
作者:Khandekar, Girish、Robinson, Gareth C.、Stacey, Nicholas A.、Thomas, Eric J.、Vather, Sunil