Cyclopropanes Wurtz reaction

Cyclopropanes undergo a ready reaction with bromine to give 1,3-dibromopropane, and can in turn be formed from 1,3-dibromopropane by the Wurtz reaction. A variation... 

Metals other than sodium may be considered for the reduction in intramolecular Wurtz reactions.11 One of the most common of these is zinc under various reaction conditions. Examples of use of this reagent that have resulted in high yields of cyclopropane and derivatives of cyclopropane include cyclopropane from... 

One type of Wurtz reaction that is quite useful is the closing of small rings, especially three-membered rings.1250 For example, 1,3-dibromopropane can be converted to cyclopropane by Zn and Nal.1251 Two highly strained molecules that have been prepared this way are bicyclobutane1252 and tetracyclo[3.3.1.13 TO - decane.1253 Three- and four-membered... 

Butenyl)-, (2,3-dimethyl-3-butenyl)- and (4-pentenyl)-dimethylsilyl)]carbene have been generated by treatment of the corresponding chloromethylsilanes with sodium. Intramolecular [1 + 2] cycloaddition of the carbenic carbon atom to the double bond leads to l-silabicyclo[3.1.0]hexanes and l-silabicyclo[4.1.0]heptanes, respectively, usually in competition with intramolecular C,H insertion (equation 24)56. In contrast, no carbene-derived product could be obtained from (allyldimethylsilyl)carbene. Finally, reaction of chloromethyldimethylvinylsilane with sodium provided, besides the typical products of a Wurtz reaction (103 and 104), a small amount of cyclopropane 106 (equation 26)56. It has been suggested that (dimethylvinylsilyl)carbene (102) isomerizes to silabicyclo[1.1.0]butane 105 by intramolecular cyclopropanation, and nucleophilic ringopening finally leads to 106. 

Although it s one of organic chemistry s classic reactions, the Wurtz reaction is seldom used for alkane synthesis. Alkanes are typically much more conveniently obtained from petroleum, natural gas, and the reduction of fatty acids. The Wurtz reaction is most valuable for specialized applications, particularly for closing cyclopropane rings, as in the synthesis of bicyclo[1.1.0]butane, shown below ... 

The intramolecular Wurtz-type coupling of dihaloorganic compounds with use of metallic zinc is a classical synthetic route to cyclic compounds. For example, cyclopropane derivatives can be prepared from 1,3-dihalo-propanes (29, 189a, 248, 451), and cyclobutane derivatives from 1,4-dihalobutanes (71). These reactions presumably proceed via the intermediate formation of organozinc compounds. The reaction of diethylzinc with esters of a,a -dibrominated aliphatic dicarboxylic acids leads to the... 

Zinc has a specific role to play in some special cases for removal of halogen in a Wurtz-like reaction.347 It is used especially for the synthesis of smallring compounds, e.g., of cyclopropanes from 1,3-dihalogen compounds.348 Shortridge348 describes the preparation of 1,1-dimethylcyclopropane as follows ... 

---