Spirocyclic cyclohexenones, formation

Cyclohexadiene-Fe(CO)i complexes. Pearson has reviewed the formation and reactions of these complexes. One particularly inteiesting property is the ability of a methoxy group to direct attack of nucleophiles to the / disubstituted cyclohexenones (3), including spirocyclic compounds. 

In contrast to the substrate-type presented in Scheme 5.6, intramolecular Mizoroki-Heck reactions with cychc alkene moieties are quite common. Negishi and coworkers [21, 29] screened numerous substrates with different substitution patterns, out of which four are shown in Scheme 5.7. Cychzation of aryl iodide 35 proceeded well and furnished tricyclic 36 in good yield, including 10% of a double-bond isomer (not shown) (35 36). Mizoroki-Heck reactions of cyclohexenones 37 and 39 provided 68% and 82% yields respectively and, probably, due to conjugation with the carbonyl group in isomerically pure form (37,39 38,40). The two analogous cyclohexenone derivatives of aryl iodide 35 (not shown) cyclized under identical conditions in 50% and 71% yields respectively. Substrate 41a even allowed for formation of spirocyclic 42a in good yield, yet with poor... 

The influence of electronic effects on aminium radical a-CH kinetic acidities has been observed in product distribution studies of Mariano and co-workers." These workers found that irradiation of (3-aminoethyl-substituted cyclohexenones 12 leads to formation of mixtures of regioisomeric products 14. The SET promoted photocyclization reactions proceed via the intermediacy of zwitterionic biradicals 13. Intramolecular proton transfer between the aminium and enone anion radical moieties in 13 is followed by radical coupling to give spirocyclic aminoketones 14 (Scheme 11). The relative rates of aminium radical... 

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See also in sourсe #XX -- [ ]

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