Mercury trihalomethyls

More useful for synthetic purposes, however, is the combination of the zinc-copper couple with methylene iodide to generate carbene-zinc iodide complex, which undergoes addition to double bonds exclusively to form cyclopropanes (7). The base-catalyzed generation of halocarbenes from haloforms (2) also provides a general route to 1,1-dihalocyclopropanes via carbene addition, as does the nonbasic generation of dihalocarbenes from phenyl(trihalomethyl)mercury compounds. Details of these reactions are given below. 

III. Dihalocarbenes from Phenyl(trihalomethyl)mercury Compounds... 

Seyferth (7) discovered that phenyl(trihalomethyl)mercury compounds decompose when heated in a solvent giving dihalocarbenes. When the solvent contains a suitable olefin, carbene addition occurs giving 1,1-dihalocyclopropane derivatives. The reaction has the advantage that strong base is not required in the reaction mixture, and base-... 

Before our studies, high temperatures (>600°C) had usually been used to generate dichlorocarbene in the gas phase. Based on trapping experiments we have shown that the trihalomethyl mercury derivatives RHgCHals, which were successfully used earlier as sources of dihalocarbenes in solution (Seyferth, 1972), are also convenient precursors of carbenes in the gas phase (Mal tsev etaL, 1971a,b). 

The preference for formation of dihalocarbenes (but not the trihalomethyl radicals) upon thermolysis of trihalomethyl mercury, silicon and germanium derivatives seems to be a result of intermolecular coordination, of type [1], and of a thermodynamic preference for the carbene-forming pathway. The... 

The advantages of this method of carbene synthesis are that reaction can be carried out in neutral solution, and that reaction yields are often dramatically improved. Thus, although reactions of dihalocarbenes generally do not give rise to products corresponding to single bond insertion, Seyferth has reported insertion of phenyl (trihalomethyl) mercury-generated carbenes into... 

The thermal decomposition of phenyl(trihalomethyl)-mercury compounds, C6H5.Hg.CX3, in the presence of olefins yields the dihalo-cyclopropane virtually quantitatively. A typical example is expressed in equation (15). The initial rate of disappearance of the organometallic... 

A. De Renzi, and E. O. Fischer, l,l-Dihalo-2-phenylvinyl Methyl Ethers from [Phenyl-(methoxy)carbene]pentacarbonylchromium(0) and Phenyl(trihalomethyl)mercurials, Inorg. Chim. Acta 8, 185-189 (1974). 

Seyferth, D. 1972. Phenyl(trihalomethyl)mercury compounds. Exceptionally versatile dihalocarbene precursors. Acc Chem Res 5, 65-74. 

Tor a review of the use of phenyl(trihalomethyl)mercury compounds as dihalocarbene or dihalocarbenoid precursors, see Seyferth, D. Acc. Chem. Res. 1972, 5, 65. For a review of the synthesis of cyclopropanes with the use of organomercury reagents, see Larock, R.C. Organomercurcury Compounds in Organic Synthesis, Springer, NY, 1985, pp. 341-380. 

PhenyH,2,4-triazoline-3,5-dione, 381-382 Phenyltrifluoromethylketene, 383-384 Phenyl(trifluoromethy))mercury, 384-385 Phenyl(trihalomethyl)mcicury, 385 Phenyltrimethylammonium perbromide,... 

Review. The chemistry of phenyl(trihalomethyl)mercury compounds has been reviewed by Seyferth.1... 

Deoxygenation 9-Dia2 fluorene. Diethyl chlmophosphite. Diethylphosphonate. 2,4-Dinitrofiuorobenzene. Hexamethylphosphorous triamide. Phenyl(trihalomethyl)mercury. Phosphorus trichloride. Tri-n-butylphosphine. Triethyl phosphite. Triphenylphosphine. DESULFinuzATiON Aluminum amalgam. Lithium-AIkylamine. Nickel (Raney). Raney cobalt catalyst. Triethyl phosphite. Triphenylphosphine. 

Carboxylic acids Phenyl(trihalomethyl)mercury. Sulfurous acid monomethyl ester... 

There are only a few examples of cyclopropanes prepared via the addition of dichlorocarbene to alkenenitriles. Depending on the structure of the unsaturated nitrile, the chloroform/base/phase-transfer catalyst or dichlorohalomethyl(phenyl)mercury methods are used in the former case, the formation of the adducts of trichloromethyl anion competes considerably. Thus, acrylonitrile, but-2-enenitrile and 3-phenylpropenenitrile gave, by the phase-transfer catalytic method, Michael adducts exclusively. The same occurs if acrylonitrile reacts with trihalomethyl(phenyl)mercury and sodium iodide mixture. An example is the formation of 1 and... 

Phenyl(trihalomethyl)mercury [1, 851-854]. Eastman supplies phenyl(trichloro-methyl)mercury. 

Early studies indicated that dichloro- and dibromocarbene (generated from halo-form) do not react with hindered steroidal double bonds. However, Bond and Cornelia76 report that if phenyl(trihalomethyl)mercury precursors are used addition can be effected to A7-, A5-, andA6-double bonds. 

Phenyl-l, 2,4-triazoline-3,5-dione, 324-326 Phenyl(tribromomethyl)mercury, 276, 277 Phenyl(trihalomethyl)mercury, 326-327 Phenyltrimethylammonium bromide, 328 Phenyltrimethylammonium per bromide,... 

Heterocycles /-Butylisocyanide. N,N -Carbodiimidazole. Cyanogen bromide. Dimethyl acetylenedicarboxylate. Dimethylformamide-POClj. Hydrazine. Phenyldiazomethane. Phenylhydrazine. Phenyl(trihalomethyl)mercury. Polyphosphate ester. Sodium aluminum chloride. 

Preparation.1 These organomercury compounds are prepared by the procedure used for synthesis of phenyl(trihalomethyl)mercury (This volume). 

Seyferth1 reports that phenyl(dihalocarbomethoxymethyl)mercury compounds, although more stable than the corresponding trihalomethyl analogs, are good sources of halocarbomethoxycarbenes. Thus, when phenyl(dibromocarbo-methoxymethyl)mercury is refluxed with cyclooctene (1) in chlorobenzene under nitrogen for 43 hours, phenylmercuric bromide is formed (87% yield) and the two... 

CARBENES, GENERATION Chloral. Dibromofluoromethane. Dimethoxy-methyl)trimethoxysilane. Dimethyl diazomethylphosphonate. S -Dimethyl-N-nitroso-2-oxazolidone. Ethylidene iodide-Diethylzinc. Ethyl trichloroacetate. Phenyl(dibromochloro methyl) mercury. Phenyl(dihalocarbomethoxymethyl)mer-cury. Phenyl(trifluoromethyl)mercury. Phenyl(trihalomethyl)mercury. Sodium chlorodiiluoroacetate. Zinc powder. 

Phenyl (trihalomethyl) mercury compounds as versatile dihalocarbene precursors, useful in synthesis of halocyclopropanes. 

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