Diiodo methane

In this model, the intermediacy of a monomeric zinc species is postulated. To support this assumption, an examination of the effect of stoichiometry and solvent in cyclopropanation involving the 2,4-pentanediol auxiliary was preformed [59]. In the initial reaction protocol, a large excess of both diethylzinc and diiodo-methane is employed. Such excessive conditions are justified on account of the instability of the zinc carbenoid under the reaction conditions. To minimize the un-... 

The methine bridge in acridines can be derived from dihalomethanes. Originally sodium carbonate was used, with dichloro- or diiodo-methane, to prepare dibenzacridine (624) from 2-naphthylamine (02JCS280). Subsequently, better yields were obtained when dichloromethane, 1,1-dichloroethane or benzal chloride, 1-naphthylamine, and a solvent were heated, the products being dibenz(c,/z jacridines (624) (06JCS1387). 

Cyclopentanones may also be synthesized from a,/ -unsaturated ketones and diiodo-methane. The ketone is converted to the O-silyl enol, and carbene is added to the enol double bond using the Simmons-Smith reaction (see p. 74f.). Thermal rearrangement of the resulting 1-siloxy-l-vinylcydopropane and add-catalyzed hydrolysis of the silyl enol ether leads to cyclopentanones in excellent yields (C. Girard, 1974). Very high temperatures, however, are needed, and this obviously limits the generality of this rearrangement reaction. 

Cyclopropanation.1 The cyclopropanation of alkenes by this combination can be facilitated by sonication or by Ti(IV) chloride, but acetyl chloride is more effective. The effectiveness of this promotor may result from removal of traces of water and hydroxylic impurities. Yields using this expedient are generally higher (45-85%) than those obtained by the original Simmons-Smith conditions using diiodo-methane. 

CYCLOPROPANATION Dicarbonyl-cyclopentadienyliron methyldimethyl-sulfonium tctrafluoroborate. Diiodo-methane. Isopropylidene diazo-... 

Isocyanides react with 2-phthalimidosulfanylphenols to give 2-imino-l,3-benzoxathioles (Equation 63) <2003S662>, and water-soluble 4-imino-l,3-oxathiolane derivatives have been formed by reaction with diiodo-methane followed by a silver or lead salt (Equation 64) <2005S2946>. A convenient route to oxathiolanes from 2-hydroxyalkyl /t-butyl sulfides and aldehydes has appeared (Equation 65) <2006T931>. 

Tabel A4.1 Contact angles of several liquids on metals. Abbreviations a = advancing angle r = receding angle a-BN = alpha-bromonaphthalene DIM = diiodo-methane or methylene iodide. In the references methodical information can be found and there the meaning of other (liquid) will also be expleilned. 

Activation of dibromo- and diiodo-methanes can also be effected using samarium powder, which generates Smh in situ. This procedure allows the isolation of the formal adduct of iodomethane to ketones and aldehydes at room temperature with very short reaction times.The iodohydrin so isolated can, of course, be readily converted to the corresponding epoxide. The reaction is thought to occur by a radical chain process. The stereoselectivity of the reaction was briefly investigated (equations 27 and 28). 

The stereochemistry of methylenation of allylsilanes with trimethylaluminum/diiodo-methane has been investigated. The stereochemistry of this reaction is explained, based on earlier work, by the outside (anti stereospecificity) or inside (syn stereospecificity) position taken by the substituent R. 

Upon Simmons-Smith cyclopropanation (CH2I2, Zn/Ag " or Zn/Cu ) vinylidenecyclo-propane gave a mixture of bicyclopropylidene (7) and dispiro[2.1,2.0]heptane (8). - An analogous reaction took place when 7-methylenedispiroheptane (9) was reacted with diiodo-methane and zinc-silver couple to give the trispiro[2.0.2.0.2.0]nonane (10) in quantitative yield.Small quantities of dispiro[2.1.2.0]heptane were isolated from the palladium acetate catalyzed reaction of vinylidenecyclopropane and diazomethane together with a variety of methylene insertion products. 

Several procedures deal with optically active auxiliaries employed in stoichiometric amounts or more, but which are not covalently bonded to one of the reagents. These catalysts influence Simmons-Smith type cyclopropanations of allylic alcohols with moderate to excellent enantiose-lectivities. Whereas the reaction of ( )-3-phenyl-2-propen-l-ol (1) with diethylzinc and diiodo-methane in the presence of (17 ,25 )-A,-methylephedrine (2 equivalents) gives an enantiomeric excess of only 24% under optimized conditions107, the same reaction with (/ ,/f)-diethyl tartrate (1.1 equivalents) as ligand affords (1 ) ,27t)-fra i-l-hydroxymethyl-2-phenylcyclopropane (2) with up to 79% ee108, Similar results are achieved with the corresponding (Z)-olefin, and even higher enantioselectivities are obtained for dimethylphenylsilyl-substituted allylic alcohols such as 3109. 

To 1 2M diethylzinc in toluene which had first been added to a solution of diiodo methane in toluene at 0°, a solution of phenol in toluene was introduced. After 10 secs, the mixture was stirred at 0° for 5 min and refluxed for 1.5 h to give 2-methylphenol. CHjIj + EljZn —> ElZnCHjI... 

Reaction of 5-0-benzyl-2,3-0-isopropylidene ribonolactone with diiodo-methane-samarium diiodide gave a low yield of cyclopropane derivative 5. ... 

Simmons-Smith reaction Areactionin which a cyclopropane ring is produced from an alkene. It uses the Simmons-Smlth recent, which was originally diiodo-methane (CH2I2) with aZn/Cu couple. Usually, diethyl zinc is used rather than Zn/Cu. The mechanism involves the formation of H2C(I) (Znl) and carbene transfer from the zinc to the double bond of the alkene. 

Fig. 22. Percentage yield of cyclopropanated material as a function of time for the reaction of methyl oleate and zinc/diiodo-methane in dimethoxyethane showing the differences in rate of reaction between the sonicated (.) and stirred (----) re-...

In addition, Kwok (Kwok and Neumann, 1996 Kwok et ai, 1998, 1999) showed that the van Oss-Good theory predicts problematic results for several liquid-liquid interfaces for which experimental data are available. While for many aqueous systems the interfacial tensions are predicted rather satisfactorily, the performance of van Oss-Good for several non-aqueous mixtures is not good. In some cases finite values for the interfacial tension are predicted for mixtures which are known to be miscible such as bromonaphthalene with alkanes and squalene-diiodo-methane. The results or at least the main conclusions appear to be independent of the source of reference liquids and parameters used for the van Oss-Good method (original ones or those from Lee, see Section 15.3.4). Kwok and Neumann (1996) state, on basis of these calculations, that it is surprising to see an approach published in well reputed journals when it can be shown to be false by anybody who possesses a simple calculator and a few drops of the liquids used in the approach . Statements like this can be found in several of the articles published by Neumann and coworkers. 

---