Stereochemistry of some spiropyrazolines and spiroisoxazolines

The stereochemistry and conformational behaviour of spiropyrazoline and spi roisoxazoline derivatives (2-5) obtained by regio- and stereoselective cycl oaddition of 1 (2-arylidene-1-tetralone, 3-arylidene-1-thiochromanone, -chr omanone and -flavanone) to C-2-(5-nitrofuryl)-N-methylnitrile imine, C-2-(5 -nitrofuryl)-N-phenylnitrile imine, C-(4-nitrophenyl)-N-methylnitrile imine and 4-nitrobenzonitrile oxide were investigated by one- and two-dimensiona l H-1, C-13 and N-15 NMR spectroscopy. The sites of the conformational equi libria were also evaluated. (C) 1999 Elsevier Science B.V. All rights reser ved.