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-T-en-9-one

The crystal structure and conformation of 1,4,4-trimethyltricyclo[5.4.0.03,5]undec-7-en-9-one (I) and 1,4,4,8-tetramethyltricyclo[5.4.0.03,5]undec-7-en-9-one (II) have been determined by X-ray diffraction. In both cases the crystals are orthorhombic, P212121,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) A,Z=4. The structure was solved by direct methods, and refined to anR value of 0.048 for 1534 (I) and 0.054 for 1357 (II) withI>3.0 σ (I). In both compounds substituted by carbonyl group ring has the distorted3E sofa conformation whereas the second one possesses the slightly deformed7.10B boat conformation.