ORGANOALUMINUM-PROMOTED CLAISEN REARRANGEMENT OF ALLYL VINYL ETHERS

Unprecedented stereochemical control has been achieved in the Claisen rearrangement of allyl vinyl ethers of type 4 with certain bulky organoaluminum reagents. Thus, methylaluminum bis(4-bromo-2,6-di-tert-butylphenoxide) (reagent A) can be utilized for obtaining the (Z) isomer, (Z)-6, whereas the (E) isomer, (E)-6 was produced with methylaluminum bis(2,6-diphenylphenoxide) (reagent B). This organoaluminum-promoted Claisen rearrangement proceeds under very mild conditions with very good E and Z selectivities. On the basis of the Claisen rearrangement of optically active substrate 7 with reagent A, the Z selectivity would be interpreted by the intervention of the chairlike transition-state conformation with the isobutyl substituent axial. The present organoaluminum-promoted Claisen rearrangement has been successfully applied to the synthesis of (4E,7Z)-4,7-tridecadienyl acetate (15), a component of the sex pheromone of potato tuberworm moth, in stereoselective fashion. Furthermore, the Claisen rearrangement of bisallyl vinyl ether 16 with reagent A or B has been found to involve the more substituted allylic system to furnish dienal 18 preferentially, not obtainable in the ordinary thermal rearrangement. This chemistry has been further extended to the ionic rearrangement of dienyl vinyl ether 28 by using reagent A in a polar solvent where the previously unknown, remote transfer of the vinyloxy moiety by [3,5]-sigmatropic rearrangement via ionic intermediate 29 has been observed. © 1990, American Chemical Society. All rights reserved.