Carbonyl paracyclophane

In this context transannular interactions must be mentioned, although there are very few authenticated reports of such effects, and they involve solely sp2 carbon atoms. Thus, Maciel and Nakashima (256) ascribed a shielding of the carbonyl atom in 129 of approximately 10 ppm relative to 128 (X = CH2, O, S) to a transannular interaction associated with a partial charge separation (Scheme 40). Less clear-cut results were obtained from the spectra of 3- and 4-thiacyclohexanone (199,257). For the sake of completeness we note that aromatic carbon atoms experience considerable deshielding (6-9 ppm) in bi- and multilayered [2.2]paracyclophanes (258,259). This was attributed to a decrease of the excitation-energy term in the o-p expression (eq. [3], p. 222). 

In the nitro- and carbonyl-substituted [2.2]paracyclophanes the most basic position is at the oxygen of the substituent, and substitution occurs in the pseudo-geminal position. 

Among the effective diphosphine-Ru-diamine complexes used for catalyzing carbonyl hydrogenation enantioselectively is one member in which the phosphorus atoms are attached to a [2,2]paracyclophane unit. ... 

Paracyclophane (la) suflers from peracid oxidation readily oxidation of la with MCPBA proceeded at 0 °C to yield the dimer 109 quantitatively [5b], The formation of dimer 109 is explained in terms of [4 + 2] dimerization of the cyclohexadienone 108 which was formed by epoxide-carbonyl rearrangement of the initially formed epoxide 107 (Scheme 20). Naphthalenophane 55a and anthracenophane 56a (s. Scheme 13) were more reactive the MCPBA oxidation completed immediately at — 78°C to give unstable dienones 110 and 111 (Structures 21) [50]. 

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