Catalytic Cycloisomerization of Unsaturated Organoiodides

Abstract

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 π-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.

Revealing the Chemistry between Band Gap and Binding Energy for Lead‐/Tin‐Based Trihalide Perovskite Solar Cell Semiconductors

“…Some recent studies have already started referring to CH 3 NH 3 PbI 3 and its derivatives as “organohalide perovskites” . According to Varadwaj, this is also misleading because the term organohalide strongly overlaps with the already established terminology that readily refers to organohalide compounds as those containing a carbon–halide covalent bond . This means that organochlorides, organobromides, organoiodides, and so forth, which are halogen‐substituted halocarbon compounds, are organohalide compounds .…”

“…[27][28][29][30] According to Varadwaj, [9] this is also misleading because the term organohalide strongly overlaps with the already established terminologyt hat readily refers to organohalide compounds as those containing ac arbon-halide covalent bond. [30][31][32][33][34][35] This means that organochlorides,o rganobromides, organoiodides, and so forth, which are halogen-substituted halocarbon compounds,a re organohalidec ompounds. [30][31][32][33][34][35] Iodomethane (CH 3 I), chlorofluorocarbon compounds (CFCs), halogen-substituted benzene derivatives (e.g.,h exachlorobenzene), and others are common examples of organohalidec ompounds.S imilarly,a so rganometallic compounds (e.g.,o rganopalladium), organohalidec ompounds are also classified by prefixing the organic moiety with "organo-".…”

“…[30][31][32][33][34][35] This means that organochlorides,o rganobromides, organoiodides, and so forth, which are halogen-substituted halocarbon compounds,a re organohalidec ompounds. [30][31][32][33][34][35] Iodomethane (CH 3 I), chlorofluorocarbon compounds (CFCs), halogen-substituted benzene derivatives (e.g.,h exachlorobenzene), and others are common examples of organohalidec ompounds.S imilarly,a so rganometallic compounds (e.g.,o rganopalladium), organohalidec ompounds are also classified by prefixing the organic moiety with "organo-". The primary difference between these two types of compounds is that the former are coordination compounds, whereas the latter are halogen-substituted organic compounds.…”

Carbometallation Reactions

“…This transformation, originally supposed to be mediated by a reversible lithium-iodine exchange process, in fact involves a radical-mediated atom transfer process [110]. The same trend was found for unsaturated secondary and tertiary alkyl iodides [111]. When 6-chloro-1-hexene 144 was treated with lithium powder and a catalytic amount of 4,4l-di-tert-butylbiphenylide (DTBB, 5 mol %) in THF at -30 hC, the corresponding cyclopentyl derivative 145 was obtained in excellent yield (Scheme 7-88).…”

“…When the exchange is con- ducted using a less reactive organolithium, an equilibrium favoring the more stable organolithium is rapidly established [108]. Therefore, the isomerization of 6-iodo-1-hexene to (iodomethyl)cyclopentane in a variety of solvents with either MeLi or PhLi, was achieved [109]. This transformation, originally supposed to be mediated by a reversible lithium-iodine exchange process, in fact involves a radical-mediated atom transfer process [110].…”