ChemInform Abstract: SYNTHESIS, STRUCTURE, AND REACTIONS OF 1,3‐OXATHIACYCLOALKANES

Unusual Conformational Isomerization of 1,3-Oxathianes

“…1,3-Oxathianes having intrinsically asymmetric ring turned out to be convenient model compounds for studying effects of heteroatoms on the conformational behavior of cyclohexane heteroanalogs [1]. It is known that chair-chair conformational isomerizations of 1,3-dioxanes [2] and 1,3-dithianes [3] never occur directly, i.e., they necessarily involve an intermediate local minimum corresponding to a flexible structure.…”

Conformational analysis of 1,3-oxathiane

“…But unlike cyclohexane [22], 1,3-dioxanes [22][23][24][25][26][27][28][29][30][31][32], and 1,3-dithiane [33,34], pathways of conformational isomerization of 1,3-oxathiane molecules were not considered. In the majority of cases "chair-chair" inversion was postulated [6,[9][10][11][12][13], and in some cases the participation of flexible forms was suggested [14][15][16]18]. In [35,36] with the help of empiric and semiempiric methods the relative stability of chair conformers and twist-forms of unsubstituted as well as 5-and 2,2,5-substituted 1,3-oxathianes have been studied.…”

“…Besides, these substances from the outset of stereochemical studies of saturated six-membered heterocycles were regaeded as convenient models for invest-tigation of the effect of heteroatom on the changes in the conformational characteristics of cyclohexane heteroanalogs [6][7][8]. According to NMR data the chair conformation is preferred for the majority of 1,3-oxathianes [6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”

Conformational properties of oxonium and sulfonium ions of 1,3-oxathiane

“…1,3-Oxathianes are employed in fine organic synthesis [1] and also possess a fundamentally asymmetric ring and are successfully used as model compounds for a study of the effects of heteroatoms on changes in the conformational parameters of cyclohexane hetero analogs [2]. It is known that protonation of saturated 1,3-and 1,3,2-heterocyclic compounds is the first stage in a variety of heterolytic ring opening reactions [3,4].…”