1.
Please propose a mechanism for the conversion of 1 to 3. Identify intermediate 2 and indicate
the relative stereochemistry of 3.
NC
O
NH2OH.HCl
80oC
2
∗
NC
∗
CN NaOAc, MeOH
CN
O N
∗
H
1
3
Heating either 2 or 3 at 180 oC gave rise to tricylic compound 4. Please provide a mechanism for
conversion of 3 into 4.
CN
NC
2
or
180oC
O N
NC
N
O
H
CN
3
4
2. Epoxide 1 reacts with thiophenol to afford in high selectivity either 2 or 3 depending on the
reaction conditions. Provide a mechanism for this transformation and explain your predictions
with clear 3D drawings. Draw the 2 chair conformations of 3 and predict why the conformation
with the –SPh in the equatorial position is the favoured conformation of 3.
OTBS
O
TBSO
OTBS
SPh
OH
PhSH, Et3N
A
OTBS
O
O
PhSH
O
TBSO
B
TBSO
SPh
OH
OTBS
OTBS
OTBS
2
1
3
∗