Cyclic compounds Wurtz reaction

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... 

The use of cesium compounds in C—C bond formation reactions has so far been limited to a few cases. Vogtle and KiUener [21] observed that the use of cesium metal in the Mtiller-Rdscheisen procedure [22] of the Wurtz coupling reaction of p-xylylene dibromide, intended to yield [2 ]paracyclophanes 1, leads to the [23]paracyclophane lb with the highest yield compared to other alkali metals. The yields of the other cyclic compounds Ic-e thereby are much lower compared to the application of sodium metal (Fig. 1) [23]. 

Gilman s significant observation that triphenylchlorosilane is a catalyst in Wurtz-like reactions forming cyclic silanes appears to be due to intermediate formation of triphenylsilyl lithium (see Chapter 9 Cyclic Silanes). The triphenyl compounds are particularly good catalysts because the corresponding alkali-triphenylsilyl compounds are the most stable among the alkali-organo-silicon compounds. 

---