Diastereotopic selection of C2 hydrogens in the rearrangement of C1-substituted epoxides: An examination of styrene oxide

✍ Scribed by J.M. Coxon; D.Q. McDonald

• Publisher: Elsevier Science
• Year: 1988
• Tongue: French
• Weight: 165 KB
• Volume: 29
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)86115-8

✦ Synopsis

Rearrangement of styrene oxide with (a) LiC104 and (b) BF3 to give phenylethanal exhibits diastereotopic selection with migration of the hydrogen trans to the phenyl group being favoured 1.4 and 1.14 times respectively. The rate of rotation about the Cl -C2 bond of the intermediate is comparable, but greater than the rate of hydrogen migration.

In the light of continuing interest'1213 in the rearrangement of substituted styrene oxides we have examined the rearrangement of the isomeric (E)-and (Z)-l-deuterostyrene oxides (1). We now report the resutts of this investigation which show that the rearrangement of these styrene oxides occurs with diastereotopic selection4 of the C2-hydrogen Vans to the phenyl group, in contrast to a recent report on the rearrangement of p-methoxystyrene oxide.'

The rearrangement of the (E)-and (Z)-l-deuterostyrene oxide5 (1) has been studied under a variety of conditions.

With UC104 in benzene at 78", aldehydes (2) and ( 3) are formed in high yield (total 85%). The ratio of aldehydes ( 2) and (3) as determined from the integrals of the 2H NMR spectrum for deutetfum at Cl (9.78 ppm) and at C2 (3.65