The Molecular and Crystal Structure of the p-Bromobenzoate of an Unusual Birch Reduction Product

概要

論文の詳細を見る
It has already been found that the Birch reduction of 1,1,4aα-trimethyl-2α-hydroxy-8-methoxy-1,2,3,4,4a,9-hexahydrophenanthrene affords a tetrahydro derivative, contrary to expectations. The present paper will describe the details of the molecular structure of the unexpected reduction product, as revealed by an X-ray crystal analysis of its p-bromobenzoate (racemate). The crystals are triclinic, with two molecules in a unit cell of the dimensions: a=11.155, b=18.123, c=5.912 Å, α=94°39′, β=111°35′, and y=90°42′. The space group is P\bar1. The intensity measurement was made on an automatic four-circle diffractometer with CuKα radiation. The structure was solved by the heavy-atom method, and was refined by the block-diagonal-matrix least-squares method, anisotropic thermal motions being assumed for all the non-hydrogen atoms. From a difference map, twenty-six of the thirty-one hydrogen atoms were also found. The final R factor was 6.5%. As a result of the present study, it has been found that the C ring of cyclohexene-type shows an unusual behavior. The length of the C–C single bond opposite to the double bond in this ring is found to be only about 1.34 Å. This remarkable shortening seems to be due to special vibrations of the two atoms concerned. The whole cyclohexene ring takes a considerably flattened, half-chair form.
公益社団法人日本化学会の論文