Petrova, Jordanka; Momchilova, Snejana; Vassilev, Nikolay G., Phosphorus, Sulfur and Silicon and the Related Elements, 1992, vol. 68, # 1-4, p. 45 - 52
ylides derived from short-chain trialkylphosphines in the Wittig-type olefinationreactions toward the synthesis of alkenes, including stilbenes, styrenes, and 1,3-dienes, as well as reagents for homologation reactions, are described. The methods allow easy access to alkenes with high (E)-stereoselectivity in good yield. These reactions are conducted with weak bases in aqueous media, which allows easy
transfer (PCET). Mechanistic experiments and DFT calculations support the possibility of a concerted protonelectron-transfer (CPET) pathway. This Birch-type reduction demonstrates that a small nucleophilic organic molecule can be used as a single electron-transfer (SET) reducing agent with a proper proton source.
Ruthenium‐Catalyzed
<i>E</i>
‐Selective Partial Hydrogenation of Alkynes under Transfer‐Hydrogenation Conditions using Paraformaldehyde as Hydrogen Source
作者:Marcus N. A. Fetzer、Ghazal Tavakoli、Axel Klein、Martin H. G. Prechtl
DOI:10.1002/cctc.202001411
日期:2021.3.5
E‐alkenes were synthesized with up to 100 % E/Z selectivity via ruthenium‐catalyzed partial hydrogenation of different aliphatic and aromatic alkynes under transfer‐hydrogenation conditions. Paraformaldehyde as a safe, cheap and easily available solid hydrogen carrier was used for the first time as hydrogen source in the presence of water for transfer‐hydrogenation of alkynes. Optimization reactions showed
irradiation has been shown to have a beneficial effect on catalyst preparation. The catalyst exhibited excellent activity in ligand‐free C−C Suzuki and Heck couplings with a large number of aryl iodide and bromides, in which microwave irradiation use cuts down reaction time. Pd/Si‐CD have shown high activity and selectivity in the hydrogenationreaction, and the semihydrogenation of phenyl acetylene was also
Palladium-Catalyzed Stereoselective Synthesis of (E)-Stilbenes via Organozinc Reagents and Carbonyl Compounds
作者:Jin-Xian Wang、Kehu Wang、Lianbiao Zhao、Hongxia Li、Ying Fu、Yulai Hu
DOI:10.1002/adsc.200606016
日期:——
In the presence of a catalytic amount of PdCl2(PPh3)2 and a silylating agent, organozinc halides reacted with carbonylcompounds to give the corresponding (E)-stilbenes in good to excellent yields under mild conditions. The reaction mechanism is briefly discussed.