Atom transfer cyclization of simple hexenyl iodides. A caution on the use of alkenyl iodides as probes for the detection of single electron transfer processes
作者:Dennis P. Curran、Dooseop Kim
DOI:10.1016/s0040-4039(00)85336-8
日期:1986.1
The trialkyltin initiated isomerization of 1-iodo-5-hexene to (iodomethyl)cyclopentane is reported. Rapid and reversible iodine atomtransfer between alkyl radicals is the key chain transfer step. The results suggest an important caution in the use of hexenyl iodides as SET probes: a good mechanism exists whereby the yield of rearranged products may be much greater than the amount of radicals produced
An intermolecular, three-component reductive dicarbofunctionalization of alkenes is presented here. The combination of Ni catalysis with TDAE as final reductant enables the direct formation of Csp3-Csp3 and Csp3-Csp2 bonds across a variety of π-systems using two different electrophiles that are sequentially activated with exquisite selectivity under mild reaction conditions.
Reactions of Saturated and Unsaturated Tertiary Alkyl Halides and Saturated Secondary Alkyl Iodides with Lithium Aluminum Deuteride. Convincing Evidence for a Single-Electron-Transfer Pathway
作者:E. C. Ashby、Catherine O. Welder
DOI:10.1021/jo9807058
日期:1998.10.1
Reactions of saturated secondary and tertiary alkyl halides with LiAlH4 (LAH) and LiAlD4 (LAD) have been carried out, and convincing evidence for a single-electron-transfer (SET) pathway has been obtained. Reactions involving saturated alkyl halides with LAD provide a model system in which a halogen-atom radical chain process is not possible, and therefore, the observation of large quantities tin some cases >90%) of protium in the reduction product provides strong evidence for a radical intermediate and a SET pathway. Specifically, the reaction of 2-iodooctane (10) with LAD produced octane with a deuterium content as low as 21%. Also, the reaction of the tertiary halide 2-iodo-2-methylheptane (15) with LAD produced 2-methylheptane (16) with a deuterium content as low as 8%. The effect of stoichiometry, halogen type, and reaction vessel surface on these reactions was studied. Reaction of the unsaturated tertiary halide 6-iodo-6-methyl-1-heptene (25) with LAD was also studied and was found to proceed predominantly by a SET process involving a halogen-atom radical chain process. The possibility of a carbocation intermediate in all of these reactions is discussed.
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.
CURRAN D. P.; KIM DOOSEOP, TETRAHEDRON LETT., 27,(1986) N 48, 5821-5824