X-RAY CRYSTALLOGRAPHIC DETERMINATION OF THE STRUCTURE AND CONFORMATION OF 1,4,4-TRIMETHYLTRICYCLO[5.4.0.03,5]-UNDEC-7-EN-9-ONE AND 1,4,4,8-TETRAMETHYLTRICYCLO[5.4.0.03,5]-UNDEC-7-EN-9-ONE

The crystal structure and conformation of 1,4,4-trimethyltricyclo[5.4.0.0(3.5)]undec-7-en-9-one (I) and 1,4,4,8-tetramethyltricyclo[5.4.0.0(3.5)]undec-7-en-9-one (II) have been determined by X-ray diffraction. In both cases the crystals are orthorhombic, P2(1)2(1)2(1), a = 6.194 (2) (I); 7.499 (2) (II), b = 7.486 (3) (I); 12.855 (3) (II), c = 26.283 (7) (I); 13.928 (4) (II) angstrom, Z = 4. The structure was solved by direct methods, and refined to an R value of 0.048 for 1534 (I) and 0.054 for 1357 (II) with I > 3.0-sigma (I). In both compounds substituted by carbonyl group ring has the distorted 3E sofa conformation whereas the second one possesses the slightly deformed B-7.10 boat conformation.