Thermal [2 + 2]-cycloaddition between silylalkynes and allenylphenols followed by the nucleophilic addition of water: metal-free and economical synthesis of arylcyclobutenals
Ni-Catalyzed Cycloisomerization between 3-Phenoxy Acrylic Acid Derivatives and Alkynes via Intramolecular Cleavage and Formation of the C–O Bond To Give 2,3-Disubstituted Benzofurans
based on transition-metal-catalyzed C-Obondcleavage have attracted much attention as a new synthetic method. Until now, several intermolecular reactions via C-Obondcleavage of aryl ethers, alkenyl ethers, esters, and others have been reported. Here we report an unprecedented C-Obondcleavage of 3-phenoxy acrylic acid derivatives, followed by intramolecular C-Obond formation with alkynes. This reaction
It has been established that a cationicrhodium(I)/BINAPcomplex catalyzes the cycloisomerization of 2-silylethynylphenols, leading to 3-silylbenzofurans, via 1,2-silicon migration. Similarly, the cycloisomerization of 2-silylethynylanilines, leading to 3-silylindoles, via 1,2-silicon migration was catalyzed by a cationicrhodium(I)/H8–BINAP complex.
已经确定,阳离子铑(I)/ BINAP络合物催化2-甲硅烷基乙炔基苯酚的环异构化,通过1,2-硅迁移导致3-甲硅烷基苯并呋喃。同样,阳离子铑(I)/ H 8 -BINAP络合物催化通过1,2-硅迁移的2-甲硅烷基乙炔基苯胺的环异构化,生成3-甲硅烷基。
GaCl<sub>3</sub>-Catalyzed Ortho-Ethynylation of Phenols
Phenols are ethynylated at the ortho position with silylated chloroethyne in the presence of a catalytic amount of GaCl3 and lithium phenoxide. The lithium salt is essential for the catalysis, and addition of 2,6-di(tert-butyl)-4-methylpyridine inhibits desilylation and hydration of the products. The reaction can be applied to various substituted phenols giving the ortho-ethynylated products in high yields, and the turnover numbers based on GaCl3 are between 8 and 10. The reaction mechanism involves addition of in situ formed phenoxygallium to the haloethyne followed by the elimination of GaCl3.
Thermal [2 + 2]-cycloaddition between silylalkynes and allenylphenols followed by the nucleophilic addition of water: metal-free and economical synthesis of arylcyclobutenals
作者:Shohei Ohno、Ramon Francisco Avena、Hiroshi Aoyama、Hiromichi Fujioka、Mitsuhiro Arisawa
DOI:10.1039/c9gc04184b
日期:——
A novel thermal [2 + 2]-cycloaddition between silylalkynes and allenylphenols to form a cyclobutachromene intermediate, followed by the nucleophilic addition of water to yield functionalized arylcyclobutenals.
heterocyclic compounds. We achieved palladium-catalyzed migratory cycloisomerization of 3-o-alkynylphenoxy acrylic acid ester derivatives to give 2,3-disubstitutedbenzofurans. Although there are several reports of benzofuransynthesis with palladium-catalyzed migratory cycloisomerization, migratory groups are limited to allyl and propargyl groups. This report is the first example of benzofuransynthesis with