Circular Dichroic Power of Chiral Spiro Aromatics. Theoretical Calculation of the CD and UV Spectra of 2,2' -Spirobi [2H- benzj ejindene ] Derivatives

The CD and UV spectra of (2S)-2,2'-spirobi[2H-benz[e]indene]1,1'(3H,3'H)-dione (2) and (IR,I'S,2S)-I,I',3,3'-tetrahydro-2,2'-spirobi[2H -benz[e]indene]-I,I' -diyl diacetate (3) were theoretical1y calculated by the application of the Jt-electron SCF-CI-DV MO method. The shape of component CD and UV bands was approximated by method (A) of the Gaussian distribution, or by method (B) employing the observed band shape of the UV spectra of model compounds. The calculated CD and UV curves were in good agreement with the observed ones. For compound 2, method (A), calcd CD, Aox! = 318.5 nm (As = +5.8), 250.0 (-63.7), 213.7 (+90.8); obsd. CD, J"" = 336.2 nm (1'11; = +11.9), 253.2 (-96.1), 214.0 (+ 1'12.1). For compound 3, method (A), calcd CD, J,e,! = 279.3 nm (As = +6.5), 224.2 (-590.2), 213.7 (+753.7); obsd. CD, J'e" = 285.0 nm (As = +4.4), 230.2 (-961.5), 221.6 (+567.1). The absolute stereostructures of chiral spiro aromatics 2 and :: have been thus established by the calculation. The mechanism of the widely spread and weak CD Cotton effects of diketone 2 has been also c1arified by the calculation. The calculated CD and UV spectral curves of compound 3 obtained by the application of method (B) were in excel1ent agreement with the observed ones: calcd CD, Ae<t = 282.5 nm (As = +10.2), 231.5 (-1139.5), 221.2 (+474.0); obsd. CD, J,,,! = 285.0 nm (As = + 4.4), 230.2 (-961.5), 221.6 (+ 567.1).