Saturated heterocycless-35. Synthesis and conformational analysis of stereoisomeric 2-oxo- and 2-thioxo-cis- and trans-5,6-trimethylene-3,4,5,6-tetrahydro-1,3-oxazines

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cis- and trans 5,6-Trimethylene-3,4,5,6-tetrahydro-1,3-oxazin-2-ones ane 2 thiones (11-20) were synthesized from cis and trans-2-aminomethylcyclopentanols (6-10) by reaction with urea ethyl chloroformate, carbon disulphide or thiophosgene. The cyclization reactions were also successful with the trans-amino-alcohols, at variance with earlier literature data relating to 1,2-disubstituted 1,3-bifunctional trans-cyclopentane derivatives X-Ray diffraction analysis of trans-5,6-trimethylene-3,4,5 6-tetrahydro-1,3 oxazine-2-thione (17) shows that the exocyclic CXXXS sp2 bond takes part in a co-planar delocalized pπ-pπ bond system formed on the S(10) O(1), N(3) and C(2) atoms and consequently both the C(2)-N(3) [1.304(7)å] and C(2)-O(1) [1.337(7)å] bonds gain some multiple bond character. The endocyclic bond angles at C(2) and N(3) are significantly opened, compared with those in related heterocycles. Of the bonds in the six membered hetero ring, C(5)-C(6) is significantly shortened [1.448(9)å] The remarkable ring-closure reaction of the trans cyclopentane derivatives can be explained by the above findings. 1H NMR data on compounds 11-20 suggest conformationally homogeneous systems and the predominance of the O-inside conformers of the cis isomers.

Original languageEnglish
Pages (from-to)1829-1836
Number of pages8
Issue number10
Publication statusPublished - 1983


ASJC Scopus subject areas

  • Biochemistry
  • Drug Discovery
  • Organic Chemistry

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