Spezielle Reaktionen von α,β-ungesättigten Ketonen, 1. Mitt.: Über die Dimerisierung von 2-Benzyliden-1-indanon in Gegenwart starker Basen

Heating of 2-benzylidene-1-indanone (1) either in dimethylformamide in the presence of guanidine carbonate or inn-propanol in the presence of thiourea and sodium propylate yields a dimerP with the structure of 1,3-diphenyl-3a,8a-dihydrospiro{cyclopentaa]indene-2,2(1H,3H)-indene}-1,8(3H)-dione (7); this was deduced from the 400 MHz-¹H- and 100MHz-¹³C-nmr-spectra and the corresponding two-dimensional HH- and CH-correlations. A possible mechanism for the formation of the spirocompound 7 is proposed; the stereo formula of the dimer7 K was established on the basis of a 400 MHz-HH-NOESY experiment.