78742-37-7Relevant articles and documents
Ene Reactions: Evidence that Oxabicyclooctanes, not Oxabicyclooctanes, are formed from the AlCl3-catalysed Reactions of Chloral with Cyclohexene and the Thermal Addition of Chloral to Cyclohexa-1,3-diene
Begley, Michael J.,Benner, Jill P.,Gill, G. Bryon
, p. 1112 - 1118 (2007/10/02)
The oxabicyclooctane (3) is formed in the AlCl3-promoted rearrangement of the ene adduct (1), itself obtained fron the AlCl3-catalysed ene addition of chloral to cyclohexene.This structural assignment, initially made on the basis of mechanistic reasoning, is consistent with the chemical and spectroscopical evidence and is confirmed by an X-ray crystallographic study.Since this compound was previously assigned the oxabicyclooctane structire (4) on the basis of an 'unambiguous' synthesis which utilised the 'Diels-Alder' addition of chloral to cyclohexa-1,3-diene, the diene reaction between carbonyl compounds and cyclohexa-1,3-dienes may not be reliable generally for the construction of oxabicyclooctenes; indeed, the Diels-Alder adduct of chloral and cyclohexa-1,3-diene is obtained only when more than the usial precautions are taken in conducting the (sealed tube) reaction.Mechanisms for the various processes are discussed.Direct methods were employed in the determination of structure (3) from diffractometer data.Crystals are monoclinic, space group P21/c with Z = 4 in a unit cell of dimensions: a = 8.527(4), b = 10.244(4), c = 12.176(5) Angstroem, β = 111.12(3); the structure was refined by full-matrix least-squares to R 0.0925 for 1092 independent reflections.The low m.p. of (3) necessitated the mounting of the crystal in a sealed capillary and this, together with its high solubility in most solvents, contributed to the difficulty in obtaining good quality crystals for the X-ray study.
