Zirconium-Mediated Intramolecular Coupling of Terminal Alkynes and Their Subsequent Carbonylation: Novel Synthesis of Seven- and Eight-Membered Heterocycles
摘要:
AbstractThe development of a new method for the intramolecular coupling of terminal alkynes and for the synthesis of seven‐ and eight‐membered benzoheterocycles is reported. The key steps involve the generation of zirconocene‐alkyne complexes from 2‐bromoalkenes and the subsequent intramolecular carbometalation of olefins or acetylides. The 8‐unsubstituted zirconabicyclopentenes were carbonylated to afford unexpected products and allow access to polyfunctionalized molecules from simple starting materials.
Nitrogen Assistance in Intramolecular Nickel-Promoted Tandem Cyclization−Quenching Processes
作者:Daniel Solé、Yolanda Cancho、Amadeu Llebaria、Josep M. Moretó、Antonio Delgado
DOI:10.1021/jo960677y
日期:1996.1.1
A diastereoselective and mild cyclization-quenching process based on the treatment of nitrogen-tethered halodienes with stoichiometric Ni(COD)(2) is described. The success of this methodology relies on the presence of a distal amino group capable of coordinating with the metal in the transient vinyl or alkylnickel species, thus controlling the diastereoselectivity of the cyclization step and preventing Ni-H beta-elimination prior to the quenching, In general, better results are obtained in cyclizations taking place via a 5-exo-trig process, and a diversity of mono- and bicyclic nitrogenated systems are afforded in high yields by the proper choice of starting halodienes and quenching reagents, The presence of 2,2'-bipyridine as a ligand results in an acceleration of the process, and in some cases, higher diastereoselectivities and/or supression of the Ni-H beta-elimination are observed.
Intramolecular Nitrogen Assistance in the Nickel-Promoted Tandem Cyclization-Capture of Amino-Tethered Vinyl Bromides and Alkenes
作者:Daniel Sole、Yolanda Cancho、Amadeu Llebaria、Josep M. Moreto、Antonio Delgado
DOI:10.1021/ja00105a096
日期:1994.12
Zirconium-Mediated Intramolecular Coupling of Terminal Alkynes and Their Subsequent Carbonylation: Novel Synthesis of Seven- and Eight-Membered Heterocycles
作者:José Barluenga、Roberto Sanz、Francisco J. Fañanás
DOI:10.1002/chem.19970030820
日期:1997.8
AbstractThe development of a new method for the intramolecular coupling of terminal alkynes and for the synthesis of seven‐ and eight‐membered benzoheterocycles is reported. The key steps involve the generation of zirconocene‐alkyne complexes from 2‐bromoalkenes and the subsequent intramolecular carbometalation of olefins or acetylides. The 8‐unsubstituted zirconabicyclopentenes were carbonylated to afford unexpected products and allow access to polyfunctionalized molecules from simple starting materials.
Intramolecular Heck-type reactions in aqueous medium. Dramatic change in regioselectivity
Efficient intramolecularHeck-type cyclizations were carried out in aqueousmedium using water-soluble Pd/TPPTS catalysts. Under these conditions, the generally observed exo process was reversed in favor of the regioselective formation of endo cyclized compounds.