Circular Dichroism of Tricarbonyl(diene)iron Complexes. The Octant Rule Applied to Ketones Perturbed by Remote Fe(CO)₃ Groups. Crystal Structure of (±)‐Tricarbonyl[(1RS,4RS,5RS,6SR)‐C5,6,C‐η‐(5,6,7,8‐tetramethylidene‐2‐bicyclo[2.2.2]octanone)]iron

Abstract

The preparation and the CD spectra of optically pure (+)‐trans‐μ‐[(1R,4S,5S,6R,7R,8S)‐C,5,6,C ‐η : C,7,8,C‐η‐(5,6,7,8‐tetramethylidene‐2‐bicyclo [2.2.2]octanone)]bis(tricarbonyliron) ((+)‐7) and (+)‐tricarbonyl[(1S,4S,5S,6R)‐C‐5,6,C‐η‐(5,6,7,8,‐tetramethylidene‐2‐bicyclo[2.2.2]octanone)]iron ((+)‐8), and of its 3‐deuterated derivatives (+)‐trans‐μ‐[(1R,3R,4S,5S,6R,7R,8S)‐C,5,6,C‐η : C,7,8,C‐η‐5,6,7,8‐tetramethylidene(3‐D)‐2‐bicyclo[2.2.2]‐(octanone)]bis(tricarbonyliron) ((+)‐11) and (+)‐tricarbonyl[(1S,3R,4S,5S,6R)‐C‐5,6,C‐ η‐(5,6,7,8‐tetramethylidene(3‐D)‐2‐bicyclo[2.2.2]octanone)]iron ((+)‐12) are reported. The chirality in (+)‐7 and (+)‐8 is due to the Fe(CO)3 moieties uniquely. The signs of the Cotton effects observed for (+)‐7 and (+)‐8 obey the octant rule (ketone n→π*CO transition). Optically pure (−)‐3R‐5,6,7,8‐tetramethylidene(3‐D)‐2‐bicyclo[2.2.2]octanone ((−)‐10) was prepared. Its CD spectrum showed an ‘anti‐octant’ behaviour for the ketone n→π*CO transition of the deuterium substituent. The CD spectra of the alcoholic derivatives (−)‐trans‐μ‐[(1R,2R,4S, 5S,6R,7R,8S)‐C,5,6,C‐η : C,7,8,C‐ η‐(5,6,7,8‐tetramethylidene‐2‐bicyclo[2.2.2]octanol)]bis(tricarbonyliron) ((−)‐2) and (−)‐tricarbonyl‐ [(1S,2R,4S,5S,6R)‐ C,5,6,C‐ η‐(5,6,7,8‐tetramethylidene‐2‐bicyclo[2.2.2]octanol)]iron ((−)‐3) and of the 3‐denterated derivatives (−)‐5 and (−)‐6 are also reported. The CD spectra of the complexes (−)‐2, (−)‐3, (+)‐7, and (+)‐8 were solvent and temperature dependent. The ‘endo’‐configuration of the Fe(CO)3 moiety in (±)‐8 was established by single‐crystal X‐ray diffraction.

Metal-Assisted Cycloaddition Reactions in Organotransition Metal Chemistry

“…356,357 Investigations on the influence of coordinated metal fragments on the reactivity of "remote", uncoordinated 1,3-diene moieties in cycloaddition reactions have been performed by several groups. Vogel, Roulet, et al [595][596][597][598][599] have prepared extensive series of stereochemically well-defined mono-and bis-metalcoordinated complexes of (poly)cyclic polyenes with exocyclic s-cis-butadiene groups, such as 371-373. The rates, [600][601][602][603] stereo-and regioselectivities 603 of the free and differently (exo/endo) metal complexed polyenes in Diels-Alder additions with symmetrical and unsymmetrical dienophiles have been studied.…”