Rearrangements in the Benzene Ring of Benzo-Fused Systems

Claisen Rearrangements in the Benzene Ring of Benzo-Fused Systems 

Whatever the exact explanation, the effects of bond localization/orbital control on the direction of the Claisen rearrangement are very powerful, as is demonstrated by the fact that rearrangement of l-allyl-2-allyloxynaphthalene (125) still proceeds to the I-position to give the nonaromatic naphthalenone 126 (64CI(L) 1801). 

As in Sections II and IV, the following discussion is organized by ring system. Rearrangements of both Types are included, but particular emphasis is placed on rearrangements of Type B in which there is a regiochemical problem. 

R = H) and the corresponding ester (128, R = COjEt) to the 4-allyl derivatives in high yield (73BSF2046). 

Higher yields of rearrangement to the 6-position are obtained when the 8-position is blocked. Thus 7-allyloxy-4-hydroxy-8-methyl-3-phenylcoumarin rearranges (50%) to the 6-allyl-7-hydroxy compound on heating (75JIC45). The blocked haloallylcoumarins 168 (X = Cl or Br) undergo Claisen re- 

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