Cucurbit[7]urilhost–guest complexes of cholines and phosphonium cholines in aqueous solution
作者:Ian W. Wyman、Donal H. Macartney
DOI:10.1039/b917610a
日期:——
The neutral host cucurbit[7]uril forms very stable complexes with a series of cationic cholines (R3NCH2CH2ORâ²+) and their phosphonium analogues (R3PCH2CH2ORâ²+) (R3 = Me3, Et3, or Me2Bz, or R3N = quinuclidinium, and Râ² = H, COCH3, CO(CH2)2CH3, or PO3H), and (±)-carnitine, in aqueous solution. The complexation behaviour has been investigated using 1H and 31P NMR spectroscopies, and ESI mass spectrometry. The complexation-induced chemical shift changes of the guests clearly indicate the effects of replacing the N(CH3)3+ end group by P(CH3)3+, and changing the nature of R on the position of the guest with respect to the CB[7] cavity and its polar portal-lining carbonyl groups. This study demonstrates that molecular recognition of cholines in aqueous solution is achievable with a neutral host without the need for aromatic walls for cationâÏ interactions.
Phosphorus-based Bifunctional Organocatalysts for the Addition of Carbon Dioxide and Epoxides
作者:Thomas Werner、Hendrik Büttner
DOI:10.1002/cssc.201402477
日期:2014.12
Bifunctional phosphonium salts were synthesized and employed as organocatalysts for the atom efficient synthesis of cyclic carbonates from CO2 and epoxides for the first time. These catalysts were obtained in high yields by a modular, straightforward one‐step synthesis. The hydrogen‐bond donating alcohol function in the side chain leads to a synergistic effect accelerating the catalytic reaction. The