Abstract
Several new reactions of trans-2,3-dichloro-1,4-dioxan (I) have been investigated and the study of several known reactions has been extended. The reaction between (I) and trimethylene glycol, previously thought to yield the cis- and trans- isomers of 2,3-ethylenedioxy-1,4-dioxepin, has been found to give only one product, this being identified as bi-1,3-dioxan-2-yl, while the reaction with propane-1,3-dithiol has been found to yield bi-1,3-dithian-2-yl. The conformation of each of these molecules together with that of tetrahydrobenzo[b]-p-dioxino[2,3-e]-p-dioxin, and of the dimethyl and diethyl (-)-1,4,5,8-tetraoxadecalin-2,3-dicarboxylates have been studied. A mechanism accounting for the formation of these products has been discussed. It has proved possible to substitute the chlorine atoms of (I) with sulphur by utilising its reaction with thiourea which gives SS'-(1,4-dioxan-2,3-diyl)dithiouronium dichloride. The conformation of this molecule has been discussed and several reactions of this compound have been studied in an attempt to prepare several new substituted 1,4-dioxans. Substitution of the chlorine atoms of (I) by nitrogen has been achieved by its reaction with N-methyltoluene-p-sulphonamide, but because the dioxan derivative could not be prepared in large amounts, further reactions were not studied. It has been found that (I) undergoes no reaction with anisole, sodium oxalate, sodium malonate, potassium thiocyanate or sodium sulphite. The conformations of 2-chloro-1,4-dioxene, 2,2-dichloro-1,4-dioxan, 2,2,3-trichloro-1,4-dioxan and the 2,3,5,6-tetra-chloro-1,4-dioxans, m.p.70[0] and m.p.143[0], have been studied by n.m.r. spectroscopy, and the reactions between some of these compounds and concentrated sulphuric acid have been investigated.