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Sigmatropic rearrangements substituent effects

Sigmatropic rearrangements are normally classified as concerted processes with relatively nonpolar transition states. However, the Fischer cyclization involves rearrangement of a charged intermediate and ring substituents have a significant effect on the rate of the rearrangement. The overall cyclization rate... [Pg.54]

The reaction occurs suprafacially across the allyl unit through a five-membered ring envelope-shaped transition state. The five-membered cychc transition state of [2,3]-sigmatropic rearrangement shows greater conformational flexibility than the six-membered transition state of [3,3]-sigmatropic rearrangements and should therefore be far more susceptible to the effects of stereochemical control by substituents. ... [Pg.381]

See other pages where Sigmatropic rearrangements substituent effects is mentioned: [Pg.53] [Pg.129] [Pg.2132] [Pg.55] [Pg.672] [Pg.732] [Pg.163] [Pg.672] [Pg.732] [Pg.578] [Pg.1166] [Pg.56] [Pg.312] [Pg.130] [Pg.178] [Pg.1053] [Pg.2132] [Pg.421] [Pg.494] [Pg.154] [Pg.164] [Pg.916] [Pg.312] [Pg.259] [Pg.259] [Pg.4319] [Pg.503] [Pg.192] [Pg.24] [Pg.84] [Pg.707] [Pg.856] [Pg.906] [Pg.973] [Pg.996] [Pg.1002] [Pg.1009] [Pg.335] [Pg.178] [Pg.50] [Pg.88] [Pg.644] [Pg.943]

See also in sourсe #XX -- [ Pg.349 , Pg.350 , Pg.351 , Pg.352 , Pg.431 ]

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Rearrangement effect

Sigmatropic -rearrangements rearrangement

Substituent effects on sigmatropic rearrangements

Substituent effects rearrangements