Cobalt-Catalyzed Addition of Arylzinc Reagents to Alkynes to Form ortho-Alkenylarylzinc Species through 1,4-Cobalt Migration
作者:Boon-Hong Tan、Jinghua Dong、Naohiko Yoshikai
DOI:10.1002/anie.201204388
日期:2012.9.17
A cobalt–Xantphos complex catalyzes the addition of an arylzinc reagent to an unactivatedinternalalkyne; the reaction most likely involves insertion of the alkyne into an arylcobalt species and vinyl‐to‐aryl 1,4‐cobalt migration, followed by transmetalation with the arylzinc reagent. Interception of the resulting ortho‐alkenylarylzinc species with electrophiles allows access to 1‐alkenyl arenes functionalized
Divergent ring-opening coupling between cyclopropanols and alkynes under cobalt catalysis
作者:Junfeng Yang、Yixiao Shen、Yang Jie Lim、Naohiko Yoshikai
DOI:10.1039/c8sc02074d
日期:——
promote ring-opening coupling reactions between cyclopropanols and unactivated internal alkynes, affording either β-alkenyl ketones or multisubstituted cyclopentenol derivatives in good yields with good to excellent regioselectivities. The chemoselectivity between these β-alkenylation and [3 + 2] annulation reactions, which likely share a cobalt homoenolate as a key catalytic intermediate, is exquisitely
Versatile Synthesis of Benzothiophenes and Benzoselenophenes by Rapid Assembly of Arylzinc Reagents, Alkynes, and Elemental Chalcogens
作者:Bin Wu、Naohiko Yoshikai
DOI:10.1002/anie.201304546
日期:2013.9.27
Rapidly aSSembled: The combination of cobalt‐catalyzed migratory arylzincation and copper‐mediated/catalyzed chalcogenative cyclization allows the construction of benzothiophenes and benzoselenophenes from arylzincreagents, alkynes, and elementalchalcogens. Benzothiophenes and benzoselenophenes diversely functionalized at the benzene ring moiety can be prepared, which are not readily accessible by
Flash vacuum pyrolysis of stabilised phosphorus ylides. Part 3. Preparation of o-methoxyphenyl- and o-methylsulfanylphenyl-alkynes and their cyclisation to benzofurans and benzothiophenes
作者:R. Alan Aitken、Graham Burns
DOI:10.1039/p19940002455
日期:——
loss of Me· and cyclisation of the resulting radicals to afford 2-substituted benzofurans or benzothiophenes 17–24. Where the substituent R1 on the ylidic carbon of the starting material is phenyl, this is incorporated unchanged into the heterocyclic products. Where R1 is Et or Pri the vinyl products are formed by intramolecular abstraction of a β-hydrogen atom following cyclisation. For R1= Me, Pr
Synthesis of Substituted Carbazoles, Indoles, and Dibenzofurans by Vinylic to Aryl Palladium Migration
作者:Jian Zhao、Richard C. Larock
DOI:10.1021/jo060727r
日期:2006.7.1
Substituted carbazoles, indoles, and dibenzofurans are readily prepared in moderate to excellent yields by the palladium-catalyzed cross-coupling of alkynes and appropriately substituted aryl iodides. This process proceeds by carbopalladation of the alkyne, heteroatom-directed vinylic to aryl palladium migration, and ring closure via intramolecular arylation or a Mizoroki−Heck reaction. Results from