Conjugated dienes Cope rearrangement

Dienes, 11 addition to, 194-198 cisoid conformation, 197, 350 conjugated, 11 Cope rearrangement, 354 cycUsation, 346 cycloaddition to, 348 Diels-Alder reaction, 197, 349 excited state, 13 heat of hydrogenation, 16,194 isolated, 11 m.o.s of, 12 polymerisation, 323 Dienone intermediates, 356 Dienone/phenol rearrangement, 115 Dienophiles, 198, 350 Digonal hybridisation, 5 Dimedone, 202 Dimroth s Et parameter, 391 solvatochromic shifts, 391 solvent polarity, 391 Y and,392 Dinitrofluorobenzene proteins and, 172... 

The first step is addition of Cl 1 to C4. We still need to form C10-C1 and break C4-C3. Since we have a 1,5-diene (Cl 1=C10-C4-C3-C2=C1), we can do an oxy-Cope rearrangement. This gives a 5-8 system in which we only have to form the C4-C2 bond. C4 is neither nucleophilic nor electrophilic, while Cl 1 is nucleophilic (conjugation from OSiMe3). Upon quenching with water, however, C4 becomes an electrophilic carbonyl C, whereupon Cl 1 attacks with concomitant desilylation of O to give the product. 

It has been established that the course of the sequential pericyclic reaction of cyclopentadienones with acyclic conjugated alkadienes depends on the reaction temperature, thermal treatment at low temperatures affording 3a,4,7,7a-tetrahydroinden-l-one derivatives by way of a Cope rearrangement (see Scheme 38). Roman et al have developed an efficient stereoselective synthesis of enantiomerically pure i-nitrotricyclo[5.2.2.0 ]undeca-3,8-dienes via a tandem consecutive asymmetric Diels-Alder-Cope rearrangement (see Scheme 39). Adducts... 

Conjugated dienes, 11 Conjugation, 11, 368 Conrotation, 345 Coordination polymerisation, 322 Copolymerisation, 322 Cope reaction, 268 Cope rearrangement, 354 Cracking, 112, 305 Cram s rule, 235 Cross-linking, 323... 

Potassium hydride and potassium hexamethyldisilazide are the most commonly used metal sources to generate the alkoxide . But recently, the indium(I)-mediated tandem carbonyl addition-oxy-Cope rearrangement of y-pentadienyl anions to cyclohexenones and conjugated aromatic ketones has been reported. For example, indium alkoxide 8.32, obtained after the addition of 5-bromopenta-1,3-diene (8.31) to the aromatic conjugated ketones 8.30, undergoes a spontaneous oxy-Cope rearrangement to give 8.33 in 55% yield (Scheme 8.9). 

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