MERCURIC OXIDE-MODIFIED HUNSDIECKER REACTION

MERCURIC OXIDE-MODIFIED HUNSDIECKER REACTION 1-BROMO-3-CHLOROCYCLOBUTANE... 

Lampman, G. M., Aumiller, J. C. Mercuric oxide-modified Hunsdiecker reaction. 1-Bromo-3-chlorocyclobutane. Org. Synth. 1971, 51, 106-108. 

In a modified procedure the free carboxylic acid is treated with a mixture of mercuric oxide and bromine in carbon tetrachloride the otherwise necessary purification of the silver salt is thereby avoided. This procedure has been used in the first synthesis of [1.1.1 ]propellane 10. Bicyclo[l.l.l]pentane-l,3-dicarboxylic acid 8 has been converted to the dibromide 9 by the modified Hunsdiecker reaction. Treatment of 9 with t-butyllithium then resulted in a debromination and formation of the central carbon-carbon bond thus generating the propellane 10." ... 

Hmtsdiecker Cristol reaction. (I, 657). A detailed procedure for the preparation of l-bromo-3-chlorocyclobutanc by the modified Hunsdiecker reaction has been published. A l-l. three-necked, round-bottomed flask wrapped with aluminum foil to exclude light and equipped with a mechanical stirrer, a reflux condenser, and an addition funnel, is charged with 37 g. (0.17 mole) of red mercuric oxide and 330 ml. 

The degradation of carboxylic acids to alkyl halides using mercuric oxide and halogens involves the initial formation of the mercuric salt of the acid, followed by a normal Hunsdiecker reaction of the salt with halogen. The relative insensitivity of the reaction to water is a consequence of the solubility of the mercury salts in the solvent (CC14). There are two limitations tertiary acids are not degraded, and use of iodine as the halogen frequently leads to the ester RCOOR as the major product. The yields in the modified reaction are usually lower than those obtained with the silver salt method.2... 

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