Generation of Reactive Low-Valent Titanium Species Using Μetal−Αrenes as Efficient Organic Reductants for TiCl<sub>3</sub>: Applications to Organic Synthesis
for TiCl(3) has resulted in an efficient method for the generation of highly reactive low-valent titanium (LVT) reagents. The activated titanium species could be prepared by refluxing a mixture of substoichiometric amounts of arenes, TiCl(3), and Li/Mg in THF or DME. Among the LVT reagents screened, TiCl(3)--Li--naphthalene--THF (reagent I) was the best for coupling of carbonyls to olefins. The reagent
Ti(O-i-Pr)4/Me3SiCl/Mg reagent mediated McMurry coupling of aryl aldehydes to biaryl olefins at near room temperature. This low valent titanium (LVT) reagent also mediated the coupling of aldimines to 1,2-diamines (imino pinacol coupling).
Ti(O - Pr)4 / Me 3 SiCl / Mg试剂在接近室温的条件下介导的芳基醛与联芳基烯烃的McMurry偶联。这种低价钛(LVT)试剂还介导了亚胺与1,2-二胺的偶联(亚氨基频哪醇偶联)。
Rapid pinacolization of carbonyl compounds with aluminium-KOH
作者:Jitender M. Khurana、Arti Sehgal
DOI:10.1039/c39940000571
日期:——
A rapid and convenient method is reported for the quantitative pinacolization of aromatic carbonyl compounds with aluminium powder and potassium hydroxide in methanol at ambient temperature.
A simple and efficient method has been developed for the synthesis of fusedpyranobiscoumarins using lead tetraacetate as an oxidizing agent by the condensation of one equivalent of 1,2‐diols and four equivalent of 4‐hydroxy coumarin in acetonitrile as solvent at 80°C with good to excellent yields.
pinacol-type couplings between two structurally similar aromatic aldehydes promoted by low-valenttitanium generated unsymmetrical pinacols in moderate to good isolated yields in an erythro/threo ratio of up to 91:9. This synthetic methodology significantly extends the scope of the cross pinacol-type couplings. pinacol - pinacol-type coupling - cross coupling - McMurry coupling - low-valenttitanium