Benzannulation from Alkynes and Allyl Tosylates via a π-Allylpalladium Intermediate
作者:Naofumi Tsukada、Shuichi Sugawara、Yoshio Inoue
DOI:10.1021/ol991406n
日期:2000.3.1
[reaction: see text] Allyl tosylate is a good allyl source for a novel palladium-catalyzed benzannulation that affords polysubstituted benzenes from 1 mol of an allyl compound and 2 mol of internal alkynes. Using triphenylphosphite as a ligand, the reaction with terminal alkynes gave trisubstituted benzenes regioselectively.
Zirconacyclopentadienes reacted with electrophiles after treatment with alkyllithium. For example, the reaction with benzaldehyde after treatment with methyllithium to give a nucleophilic addition product of a dienyl moiety to aldehyde, dienylcarbinol, in a moderate yield. Similar reaction of a zirconacyclopentadiene using butyllithium with methyl methacrylate afforded a Michael addition product in a good yield. Treatment of zirconacyclopentadienes with n-BuLi followed by 1-bromo-2-butyne gave a mono-propargylated diene derivative in 95% yield after hydrolysis. When propargyl chloride was treated with n-BuLi first and then added to zirconacyclopentadienes, penta-substituted benzene derivatives were formed in high yields. (C) 2004 Published by Elsevier Ltd.
Palladium-Catalyzed Benzannulation from Alkynes and Allylic Compounds
Various alkynes reacted with allyl tosylates in the presence of palladium catalysts, giving polysubstituted benzenes with good to high regioselectivity. Pentasubstituted and trisubstituted benzenes were readily prepared by reaction of internal alkynes and terminal alkynes, respectively. The combination of allyl alcohols and p-toluenesulfonic anhydride could be utilized in place of isolated allyl tosylates. The cyclization of diynes with allyl tosylate afforded bicyclic compounds containing an aromatic ring.