Orbital interactions. 6. The Birch reduction as a tool for exploring orbital interactions through bonds. Through-three-bond interactions

An Investigation on the Synthesis of New Molecular Architectures from the Cyclotrimerisation of exo‐ and endo‐Benzotricyclo[4.2.1.02,5]nonene

“…The electrophilic addition of bromine to exobenzocyclobutenonorbornene 3 [5] was first reported by Nenitzescu et al, [7] who described the formation of the trans dibromide 5. In this reaction, beside to the reported non-rearranged product 5 (90%), we also observed formation of the rearranged dibromide 6 (8%).…”

“…The starting materials for the synthesis of the several diastereoisomers implicit in the general structure 2 are the known exo-and endo-benzotricyclo [4.2.1.0 2,5 ]nonenes 3 [5] and 4, [6] which were submitted to bromination followed by dehydrobromination and metallation to obtain the direct precursors for the cyclotrimerisation reaction (these compounds are described in the Results and Discussion). These operations were not trivial, because of the propensity of polycyclic systems to undergo rearrangements, and required an in-depth study of their behaviour.…”

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We have performed an investigation on the cyclotrimerisation of molecules having exo-and endo-benzotricyclo[4.2.1.0 2,5 ]nonene skeletons (3 and 4) with the aim of producing their respective cyclotrimers 2 that feature unusual geometries and electronic properties. Activation towards the cyclotrimerisation reaction was performed using the vic-bromostannyl vinyl derivatives and was accomplished under copper-mediated or palladium-catalysed reaction conditions.

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The observation of remarkable effects of remotely connected but spatially proximate hydroxy-groups on the rates and regiochemistry of the birch reduction of aromatic rings and double bonds

“…Birch reductions of ( l ) , (6a), (lOa), (11 b), and (12b), none of which possess intramolecular O H 0 . x bonds,appeartoobeythird-order kinetics [equation (3)] whereasthoseoftheOH X-bonded alcohols (6b), (lob), (1 1 a), and (1 2a) followed a combination of second-and third-order kinetics [equation (5)]. The rate and product data for the reduction of the alcohols (6b)-(8b), (lob), ( I l a ) , and (1 2a) are explained in terms of the presence of intramolecular O H…”

Metal-nitroxyl interactions. 25. Exchange interactions via saturated linkages in spin-labeled porphyrins

“…Since the electron magnetic moment is much larger than the proton magnetic moment, it is reasonable to expect even longer range spin-spin interactions between two electrons than between two protons or between a proton and an electron. Orbital interactions through six bonds have also been found to be sufficiently large to alter chemical reactivity (13).…”