Joseph Klein

Stable polycyclic anions: dianions from overcrowded ethylenes

Stable overcrowded ethylene dianions, viz. bifluoren-9-ylidene dianion (1)2– and bi-(4H-cyclopenta[def]phenanthren-4-ylidene) dianion (2)2– were prepared via metal reduction and characterized by 1H and 13C n.m.r. spectroscopy; the spectroscopic results as well as ωβ calculations performed on the hydrocarbons (1) and (2) and the corresponding dianions (1)2– and (2)2– are discussed with respect to their diatropicity and spatial structure.

Metallation reactions: the trimethylenemethane dianion

Metallation of isobutene in the presence of tetramethylenediamine gave consecutively the methylallyl anion and the trimethylenemethane dianion.

New heterocyclic dianions: n.m.r. characterization of 1,3-diphenylbenzo[c]-thiophene dianion, a stable 4nπ charged system containing sulphur

1,3-Diphenylbenzo[c]thiophene dianion, (1)2– a member of the novel series of 4nπ polyheterocyclic dianions, has been prepared and characterized by n.m.r.; it shows a high stability and a peculiar charge distribution pattern in which the sulphur atom polarizes the charge towards the α-positions.

Substituted [24]paracyclophanes

Synthesis, characterization and stereochemistry of new derivatives of [24]paracyclophane, containing carboxylic acid ester groups, are described.

Novel heterocyclic anions: benzo[b]thiophene dianion, the first sulphur doubly charged 4nπ system

Benzo[b]thiophene dianion (1)2–, the first sulphur-containing 4nπ polycyclic dianion, was prepared via metal reduction and characterised by 1H and 13C n.m.r. spectroscopy; the reaction products depend on the reduction conditions.

Dilithiation of propene and allylbenzene and the structure of the dimetallated product

Propene and allylbenzene have been metallated to give dilithio derivatives and the structure of the dilithio derivative of the latter has been suggested.