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Application of the copper chloride-catalysed addition of substituted aromatic sulphonyl chlorides to ethylene and butadiene is extended to sulphonyl chlorides carrying bromine, carboxy-, chloromethyl, chlorosulphonyl, and 2-chloroethylsulphonyl substituents. Several ethylene adducts are further transformed by chlorosulphonation. dehydrochlorination, and oxidation of a methyl to a carboxy-group.The cis-rrans-isomerisation of but-2-ene by toluene-p-sulphonyl chloride a t 100" is discussed. The isomerisation has a radical-chain character, is strongly retarded by chloride ions, and is completely inhibited by norbornadiene.

Summary. Topochemically controlled photochemical dimerization of diethyl succinylsuccinate in the solid is reported. The structure evaluation by elemental and spectroscopic analysis of the product is given. The participation of chelated enols in photochemical cycloadditions in the crystalline solid state is here demonstrated for the first time.The ground state low molecular [l] as well as macromolecular [2] chemistry of succinylsuccinic esters (1,4-dialkoxycarbonyl-2,5-dihydroxy-cyclohexa-l, 4-dienes) is well documented. Their photochemical behaviour has however received no attention until now.We found that irradiation of powdered triclinic crystals of diethyl succinylsuccinate (DESS) or of their aqueous dispersion with light of A> 260 nm, followedby Soxhlet extraction of unreacted material, gave a photoproduct according to the ollowing s cheme : OHThe production of ~nti-tricyclo[4.4.0~~~.0~~~~]-1,4,7,10-tetrae~hoxycarbonyl 3,6,9,12-tetrahydroxy-dodeca-3,9-diene in this photoreaction is the first example of dimerization of chelated enols in the solid state2) and it reaffirms the anticipated mechanism of participation of chelated enols in 2+2 cycloadditions [4]. The topochemical control [5] of the reaction is demonstrated by the absence of dimerization in solution, by the analogous solid-state dimerization of dimethyl succinylsuccinate3), as expected from its similar crystal structure [6], by contrast with the photostability3) of 1,4-diethoxycarbonyl-2,5-diamino-cyclohexa-1,4-diene [7] under the same conditions, owing to its obviously different crystal packing.Traces of diethyl-2,5-dihydroxyterephthalate were also found in the extract. Although aromatization by way of hydrogen atom abstraction from the cyclohexadiene by a photoexcited species is not unfeasible [S], this compound is believed to be a l) *) 3,Unpublished results.On leave of absence from the Weizmann Institute of Science, Rehovot, Israel. En01 dimerization in solution was only recently first reported [3].

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