RESUMO
[reaction: see text] Chiral 2-cyclopropenyl-4-tolyl sulfones, available by the [2 + 1]-cycloaddition of tosyldiazomethane to acetylenes under catalysis by the Rh(II) complex 1, provide a number of unusual transformations and useful chiral products. This chemistry is dominated by the unusual strain and reactivity of the cyclopropene ring system.
RESUMO
[structure: see text] The title 1,4-piperazine-2,5-dione was synthesized in 23% yield over six steps from ethyl 2-amino-4,7-dimethoxyindan-2-carboxylate. Crystallization by slow diffusion of ether into a chloroform solution and by slow evaporation of an ethanol-chloroform-benzene solution produced polymorphic crystalline forms as determined by single-crystal X-ray analysis. The polymorphs exhibited different hydrogen-bonding networks. The association of this piperazinedione in solution was studied using mass spectrometric and nuclear magnetic resonance spectroscopic techniques. The MS and NMR data were interpreted using the solid-state structures as models for solution aggregation. Association constants extracted from the NMR data are in line with those of other cyclic cis amides in chloroform solvent.
