1 -Amino-1 -anisyl-1-phenyl-1 -propanol

Conformational factors can determine more than the stereochemistry of rearrangement. In light of Collins findings, let us examine work done earlier by D. Y. Curtin (of the University of Illinois) with 2-amino-1-anisy 1-1-phenyl-1-propanol. This resembles Collins labeled compound (p. 899), except that an anisyl group (p-methoxyphenyl group) takes the place of one of the phenyls. Here, the competition in migration is between a phenyl and an anisyl, instead of between labeled and unlabeled phenyl groups. 

Figure 28.2. Pinacolic deamination of diastereomeric 2-amino-l-anisyl-1-phenyl-1-propanols. In each case the most abundant conformer. Via or Vila, of the diazonium ion yields a cation in which an aryl group is in position for back-side migration via a trans transition state anisyl in lb, phenyl in VII6. Such rearrangement predominates. Some of each first-formed cation is converted through rotation into another cation, in which the other aryl group is in position for front-side migration via a trans transition state phenyl in Vic, anisyl in VIIc. Such rearrangement gives the minor product.

The pinacolic deamination of 2-amino-1,1 -diaryl-1 -propanols provides a convincing case for conformational control. Optically active 2-amino-l,l-diphenyl-l-propanoI 209) affords a-phenylpropiophenone (210) with 88% inversion plus 12% retention (76% inversion plus 24% racemization) at the terminus of phenyl migration 196K The diastereomer (211) of 2-amino-l-anisyl-l-phenyl-l-propanol reacts with preferential... 

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