Level 3 – Case 40
270
OBs
AcOH
OAc
exo-2
3
AcOH
OAc
endo-2
3
OBs
Scheme 40.1
2. The solvolysis rate of exo-brosylate 2 was enhanced 57-fold relative to the rate
of solvolysis of the endo-isomer.
3. A study of the solvolyses of optically active exo-and endo-brosylates 2 revealed
that the endo-isomer lost 57% of its optical activity while the exo-isomer retained 99% of its optical activity.
4. Independently deuterium-labeled exo-brosylates 2 at C8 and C9 positions were
employed in separate experiments. When labeled at C8, products from acetolysis of exo-2 exhibited a distribution of deuterium over C4 and C8 positions
(compounds 4 and 5), while when labeled at C9 exo-2 gave scrambling of deuterium over C5 and C9 (compounds 6 and 7). The distribution of the labels was
50:50 in both cases (Scheme 40.2).
OBs
D
AcOH
D
OBs
OAc
D
AcOH
OAc
D
OAc
D
OAc
D
4
5
7
6
8
9
4
8
9
5
Scheme 40.2
5. Independently deuterium-labeled endo-brosilates 2 at C8 and C9 positions gave
the same positional scrambling that their exo-epimers. In both experiments a
55-60% of the label was retained at the original position (Scheme 40.3).