Chemistry of Dienyl Anions. II. Crystalline Bis(dienyl)magnesium. Selective Dienylation and Structure in Solution and in the Solid State

Article abstract of DOI:10.1246/bcsj.53.1089

Seven different crystalline bis(dienyl)magnesium TMEDA complexes of open chain or cyclic structure were prepared by metal exchange reaction of corresponding potassium dienides.They are fluxional in solution due to the rapid 1,3-rearrangement.Terminally ?-bonded trans or (E) structure exists primarily in the open chain complexes while centrally ?-bonded cis structure in cyclic dienylmagnesium TMEDA complexes.The former gave 1,3-dienes exclusively but the latter gave 1,4-dienes upon hydrolysis.Molecular structure of bis(2,4-dimethyl-2,4-pentadienyl)magnesium determined by X-ray crystallography showed that it has terminally ?-bonded structure.Addition of dienylmagnesium compounds to acetone followed by hydrolysis gave 1,4-diene derivatives regioselectively but that to diisopropyl ketone gave 1,3-diene derivatives selectively.Unsaturated alcihols with an elongated carbon chain were synthesized by thermal cracking of cyclic ether complexes. 1,3,7-Trienes can be obtained selectively by reaction of appropriate allyl halides in the presence of CuCl catalyst and regiosective dienylation occured by using TiCl2(η5-C5H5)2 as catalyst.