Dichlorocarbene

• Carbon ( II) chloride
• Kohlenstoffdichlorid
• Dichloromethylene

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Dichlorocarbene is encountered in organic chemistry carbene. The reactive intermediate with the formula CCl 2 is easily accessible by the reaction between chloroform and a base dissolved in water such as potassium tert -butoxide, or sodium hydroxide. The entry of the present salt as bases in the organic chloroform phase must be carried out using a phase transfer catalyst.

Representation

Dichlorocarbene can be recovered and mercury by reaction of ethyl trichloroacetate with sodium methoxide in pentane or thermal decomposition of phenyl ( trichloromethyl ).

Dichlordiazirin is an experimental dichlorocarbene precursor which is stable in the dark at room temperature and by photolysis to release of molecular nitrogen yields the carbene. Phenol reacted with cyanogen bromide to this phenyl cyanate (A), which is reacted with hydroxylamine to give N -hydroxy- O -phenyl- iminocarbamat (b). The hydroxy group is activated by methanesulfonyl chloride and transferred to a mesyl group (c). The intramolecular ring closure to aziridine succeed with sodium hypochlorite ( d), after which a nitration of the phenyl group is carried out with nitronium tetrafluoroborate (s). In an ionic liquid a nucleophilic substitution with cesium chloride under phase transfer catalysis is carried out with tetrabutylammonium chloride (F).

Dichlorocarbene can be obtained also by sonochemical reaction between carbon tetrachloride with elemental magnesium. This reaction tolerates ester and carbonyl functions, since no strong base is needed.

Reactions

Dichlorocarbene reacts with alkenes in a formal [1 2] cycloaddition to give geminal Dichlorcyclopropanen, which can then be reduced to the corresponding cyclopropanes or hydrolyzed with water to a cyclopropanone. The representation of dichlorocarbene from chloroform and its preparative benefit was discovered in 1954 by William von Eggers Doering, the cyclohexene functionalized in this way.

In the Reimer - Tiemann reaction dichlorocarbene reacts with phenol to salicylaldehyde.

History

Dichlorocarbene as a reactive intermediate was first proposed in 1862 by Johann Georg Anton Geuther, the chloroform took as CCl 2 · HCl. Jack Hine published in 1950 an article about dichlorocarbene as the reaction intermediate Chloroformhydrolyse. Evidence succeeded William von Eggers Doering 1954.

Related reactions

In the Allensynthese by Doering - LaFlamme alkenes are reacted in a chain extension reaction to allenes. For this purpose, the olefin is first contacted with dichlorocarbene to the reaction in order to subsequently obtain through the use of magnesium or sodium, the Allen. This reaction sequence is also present in the extraction of cyclopentadienes by Skattebøl rearrangement. The reaction between phenols with dichlorocarbene is called the Reimer - Tiemann reaction. The dichlorocarbene closely related is the more reactive dibromocarbene CBr2.

Chlorcarben

The related Chlorcarben ( ClHC ) can be obtained by reaction of dichlorocarbene with methyllithium. It can be used to obtain spiro pentadiene.