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Zur Konfiguration der 2,4,6,8‐Tetrabrom‐cyclooctan‐1,5‐dione Reduktion des β‐Isomers durch Natrium‐borhydrid
Author(s) -
Heller Jürg E.,
Dreiding André S.
Publication year - 1973
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19730560133
Subject(s) - chemistry , sodium borohydride , nonane , bicyclic molecule , stereochemistry , intramolecular force , cyclooctane , derivative (finance) , organic chemistry , financial economics , economics , catalysis
Of the two previously described 2,4,6,8‐tetrabromo‐cyclooctane‐1,5‐diones, the higher melting β‐isomer, mp. 226°, was treated with sodium borohydride to give: (1) by a double reduction and an intramolecular S N 2‐reaction two epimeric alcohols, namely the 2‐ exo ‐hydroxy‐ ( 6 ) and 2‐ endo ‐hydroxy‐ ( 7 ) isomers of 3‐ exo ,5‐ exo ,7‐ endo ‐tribromo‐9‐oxa‐bicyclo[4.2.1]nonane, and (2) by a single step reduction a hemiketal, 1‐hydroxy‐2‐ exo ,4‐ exo ,6‐ endo ,8‐ endo ‐tetrabromo‐9‐oxa‐bicyclo[3.3.1]nonane ( 8 ). The structures of these three hydroxy‐compounds ( 6, 7 and 8 ) were derived from their properties, especially from complete analyses of their NMR.‐spectra, which led to deductions of all configurations and conformations. Of special interest is the preferred existence of the 9‐oxa‐bicyclo[3.3.1]norane derivative 8 in a chair‐chair conformation. The derivation of the configurations of the three hydroxy‐compounds 6, 7 and 8 is tantamount to establishing the 2,4‐ cis , 4,6‐ trans , 6,8‐ cis ‐configuration ( 5 ) of the β‐isomer of 2,4,6,8‐tetrabromocyclooctane‐1,5‐dione, mp. 226°.