Preparation diiodomethane

An organozmc compound that occupies a special niche m organic synthesis is lodo methyhinc iodide (ICH2ZnI) It is prepared by the reaction of zinc-copper couple [Zn(Cu) zinc that has had its surface activated with a little copper] with diiodomethane m diethyl ether... 

The cyclopropanation of 1-trimethylsilyloxycyclohexene in the present procedure is accomplished by reaction with diiodomethane and diethylzinc in ethyl ether." This modification of the usual Simmons-Smith reaction in which diiodomethane and activated zinc are used has the advantage of being homogeneous and is often more effective for the cyclopropanation of olefins such as enol ethers which polymerize readily. However, in the case of trimethylsilyl enol ethers, the heterogeneous procedures with either zinc-copper couple or zinc-silver couple are also successful. Attempts by the checkers to carry out Part B in benzene or toluene at reflux instead of ethyl ether afforded the trimethylsilyl ether of 2-methylenecyclohexanol, evidently owing to zinc iodide-catalyzed isomerization of the initially formed cyclopropyl ether. The preparation of l-trimethylsilyloxybicyclo[4.1.0]heptane by cyclopropanation with diethylzinc and chloroiodomethane in the presence of oxygen has been reported. "... 

During preparation of cyclopropane derivatives, it is important to add the diiodomethane slowly to a solution of diethylzinc in the alkene. Addition of diethylzinc to an alkene-diiodomethane mixture may be explosively violent. 

Li[Ph4P2N4S2R].274 Alkali-metal derivatives of the dianion [Ph4P2N4S2]2 are prepared by treatment of 111 (E=S, R=Ph) with alkali-metal superhydrides M[Et3BH] (M=Li, Na].275 The methylene bridge between the two sulfur atoms in 116 is introduced by the addition of diiodomethane to... 

Among methods of preparing optically active cyclopropane compounds, the Simmons-Smith reaction, first reported in 1958, is of significance. This reaction refers to the cyclopropanation of alkene with a reagent prepared in situ from a zinc-copper alloy and diiodomethane. The reaction is stereospecific with respect to the geometry of the alkene and is generally free from side reactions in contrast to reactions involving free carbenes. 

F]Fluoroiodomethane, a valuable synthetic precursor for the introduction of a fluoromethyl group into radiopharmaceuticals, has been prepared from diiodomethane (Scheme 55) [224]. Its reactivity toward amine, acid, thiol or phenolate functions has also been studied. 

Protection and deprotection of the dithiol The formaldehyde dithioace-tal (129) could be prepared by reacting the dithiol with diiodomethane and pyridine, but not with paraformaldehyde. Other thioacetals could be prepared by the standard procedure (aldehyde, BF3 etherate). Interestingly, both cis and trans dithiols gave the thioacetal, thereby enabling the complete conversion of mixtures of cis and trans dithiols to the pure cis derivative. Several mechanistic explanations are possible for the epimeri-zation at C-6 in the thioacetalization of the trans dithiol, but detailed analysis has not been done. 

A homogeneous solution of the bis(iodomethyl)zinc DME complex in dichloromethane can be prepared by adding diethylzinc to 1 equivalent of 1,2-dimethoxyethane in dichloromethane followed by 2 equivalents of diiodomethane . The presence of DME makes the preparation of the reagent safer by ensuring that the mixture is constantly homogeneous. This reagent has been useful in enantioselective cyclopropanation reactions vide infra). 

Eisch and Piotrowski reported the preparation of gem-dizinc compounds from diiodomethane and zinc powder in the titanocene chloride mediated methylenation of ketones in 1983 (equation 5)7. In this case, it was not mentioned that they had used pyrometallurgy zinc. The Tebbe-type reagent 2 was shown as an intermediary species. Before addition of titanocene chloride, the amount of methane was measured after hydrolysis of the reaction mixture to determine the formation of gem-dizinc species7. 

In 1998, Matsubara, Utimoto and coworkers reported a general procedure for the preparation of bis(iodozincio)methane, which was obtained as a THF solution (equation 6)9. The detailed structural study of the solution by SANS (small angle neutron scattering), AXS (anomalous X-ray scattering) and EXAFS (extended X-ray absorption fine structure) implied that the g< wt-dizinc species prepared from diiodomethane and zinc is the monomeric bis(iodozincio)methane (3). Formation of polymethylene zinc 4 via Schlenk... 

Organomercury compounds such as ICFbHgl and Hg(CH2Br)2 may be prepared by the reaction of metallic mercury with diiodomethane or by reaction of mercury(II) salts with diazoalkanes. These mercury derivatives are related to the intermediate that has been proposed in the Simmons-Smith reaction, and likewise, they have been found to convert alkenes into cyclopropanes.92... 

The cyclopropanation requires a methylene carbene that can add to the double bond. Under which of the following sets of conditions can methylene be prepared in situ from diiodomethane a) CH.I2, Cu/Zn b) CH2I2, KMn04 c) CH2I2, ZnEt2 ... 

The preparation of dibenzo-fused dithiepins was usually catalyzed by BF3 Et20. For example, the synthesis of dibenzo[7//][l,3]dithiepin from 1,1 -binaphthalene-2,2 -dithiol and dibromomethane and diiodomethane, respectively, failed however, reaction of the dithiol with dimethoxymethane in the presence of BF3-Et20 afforded the desired dithiepin in 71% yield <1995T787>. 

Bis-[iodomethyl tellurium, the only isolated representative of this class of organic tellurium compounds, was obtained by reduction of bis[iodomethyl] tellurium diiodide with potassium disulfite. The diiodide was prepared in widely fluctuating yields never exceeding 30% by heating amorphous tellurium and diiodomethane at 80° for 49 h1. Bis[iodomethyl] tellurium polymerizes in solution and on heating1. 

In recent years, exposing the preparation of the reagent from samarium metal and an oxidant to different stimuli has led to significant improvements in reaction time. Concellon utilized the sonication of samarium metal and iodoform at room temperature to give a solution of Sml2 in THF in approximately 5 min (Scheme 2.3).5 This approach was also used by Flowers to synthesise other Sm(II) species.6 It was also reported that using different oxidants, such as 1,2-diiodoethane, diiodomethane and iodine, works just as well with this technique.5... 

Triphenyl-1,3-dithiole (233) (Rj = R2 = R3 = C6H5) has been converted into the corresponding salt by means of trityl perchlorate.24 On the other hand, the 4,5-dicyano derivative (236) [which was first prepared by Bahr et al.li8 from carbon disulfide and ammonium cyanide by spontaneous desulfurization of the salts of cyanodithio-formic acid (235), followed by ring closure with diiodomethane] is stable towards various oxidizing agents. The ease of oxidation of 233 to 234 is probably dependent on the same structural factors which govern the preparation of dioxolenium salts from 1,3-dioxolanes.149... 

Simmons-Smith reaction (Section 7.6) a method for preparing a cyclopropane by treating an alkene with diiodomethane and zinc-copper. 

The use of 1,1-diiodomethane as an electrophile in the Birch reduction (with lithium in liquid ammonia) of electron-deficient pyrroles 915 furnished pyrrolines 916 (in high to excellent yields), which provided access to the synthetically important functionalized 5,6-dihydro-2(l//)-pyridinones 917 (via radical ring expansion), substructures commonly found in biologically active natural products (Scheme 177) <2004CC1422>. 2-(Chloroalkyl)-substituted pyrrolines 919 were duly prepared by the reductive alkylation (with l-chloro-3-iodopropane or 1-chloro -iodobu-tane) of electron-deficient pyrrole 918. Allylic oxidation then furnished lactams 920 (Scheme 178). 

Bromo- or 6-iodo-9-(/3-D-2,3,5-tri-0-acetylribofuranosyl)purines have been prepared in good yields (72.7% and 68.6%) from 2, 3, 5 -tri-0-acetyladenosine with pentyl nitrite in bromoform or diiodomethane (as halogen sources), respectively, under 200 W illumination (80JOC3969). 

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