A sterically congested cis-stilbene and its phosphonium salt precursor

作者：Shivaprakash Shivanna; Reddy G Chandrasekara; Jasinski Jerry P; Millikan Sean P; Duff Courtney E; Glidewell Christopher^*

来源：Acta Crystallographica Section C-Structural Chemistry, 2015, 71(6): 479-+.

DOI：10.1107/S2053229615009110

• phosphonium salt
• polyalkoxy-substituted stilbenes
• Wittig reaction
• crystal structure
• hydrogen bonding
• steric congestion

Triphenyl(2,4,5-trimethoxybenzyl)phosphonium chloride is formed in solvent-free form by the reaction under anhydrous conditions between triphenylphosphane and 2,4,5-trimethoxybenzyl chloride, but when it is crystallized from a mixture of ethyl acetate and chloroform in the presence of air it forms a stoichiometric monohydrate, C28H28O3P+Cl-H2O, (I). The reactions between the anhydrous phosphonium salt and alkoxy-substituted benzaldehydes, using Wittig reactions in the presence of potassium tert-butoxide, provide a series of multiply substituted stilbenes, most of which were assigned the Z configuration on the basis of their NMR spectra. However, no such deduction could be made for the symmetrically substituted (Z)-2,2,4,4,5,5-hexamethoxystilbene, C20H24O6, (II). Compound (II) does in fact have the Z configuration and the molecular geometry provides evidence for steric congestion around the central double bond; in particular, the central alkene fragment is nonplanar, with a CC=CC torsion angle of 7.8(4)degrees. In hydrated salt (I), the chloride anions and water molecules are linked by OH...Cl hydrogen bonds to form C-2(1)(4) chains; each cation is linked by CH...O hydrogen bonds to two different chains, so forming a sheet structure. There are no direction-specific intermolecular interactions in the structure of (II).

• 出版日期2015-6