Catalytic Cycloisomerization of Unsaturated Organoiodides
作者:William F. Bailey、Matthew W. Carson
DOI:10.1021/jo981991q
日期:1998.12.1
Catalytic quantities of phenyllithium (PhLi) have been found to initiate novel 5-exo cycloisomerization of a variety of structurally diverse unsaturated organoiodides. The isomerization reaction appears to be a process of broad synthetic utility for the preparation of iodomethyl-substituted five-membered rings. Primary, secondary, tertiary, or aryl iodides tethered to a suitably positioned carbon-carbon pi-bond are converted cleanly to their cyclic isomers in good to excellent yield (i.e., 70-90%) by simply allowing a hydrocarbon-MTBE solution of the iodide to stand in the presence of a small quantity of PhLi at an appropriate temperature. The mechanism of the cycloisomerization was found to be substrate dependent: unsaturated aryl and primary alkyl iodides undergo isomerization via a three-step cascade (eqs 1-3) mediated by two reversible lithium-iodine exchange reactions bracketing an irreversible 5-exo cyclization of an unsaturated organolithium; unsaturated secondary and tertiary alkyl iodides apparently isomerize via a radical-mediated atom transfer process initiated by homolytic fragmentation of the ate-complex generated upon attack of PhLi on the iodine atom of the substrate.
BECKWITH A. L. J.; MEIJS G. F., J. ORG. CHEM., 52,(1987) N 10, 1922-1930
作者:BECKWITH A. L. J.、 MEIJS G. F.
DOI:——
日期:——
Iododediazoniation of arenediazonium salts accompanied by aryl radical ring closure