Lithiation Reactions Catalyzed by Linear and Cross-Linked Arene-Based Polymers. Generation of Functionalized Organolithium Compounds
摘要:
Lithiation of various substrates, such as chlorinated acetals, alpha-chloro ether, dichloro derivatives, benzo-fused heterocycles, and allyl and benzyl derivatives, with excess lithium powder in the presence of a catalytic amount of soluble linear or insoluble cross-linked arene (naphthalene or biphenyl)-based polymers yields the expected organolithium intermediates. The latter react with electrophiles either in two steps or under Barbier-type reaction conditions to afford the corresponding adducts. The catalyst is easily recuperated by filtration at the end of the process, and the procedure can be regarded as a reasonable alternative to the use of free arenes as electron carrier in lithiation reactions.
Functionalised organotitanium compounds: from lithium to titanium intermediates in chemoselective reactions with carbonyl compounds
作者:Isidro M Pastor、Miguel Yus
DOI:10.1016/s0040-4020(01)00103-x
日期:2001.3
The reaction of functionalised organolithium compounds 1 with an equimolecular mixture of two carbonyl compounds in the presence of 2 equiv. of triisopropoxytitanium chloride can discriminate between aldehyde and ketone, the process being selective for aldehydes at room temperature. Electronic and steric effects have been observed for different aldehydes.