WORKED PROBLEMS
625
The major products from similar base treatment of (2S,3S)- and (2R,3S)-2-bromo-3-methylpentane can be deduced
as below
(2S,3S) is the enantiomer;
opposite configuration at each centre
(2R,3S) is a diastereoisomer;
opposite configuration at C-3
(C-3 is rear chiral centre)
2S,3S
Me
Et
Me
Et
Me
Me
Z
2R,3S
it gives the same
product
it gives the Z
product
E
H
Et
Me
H
Br
Me
Et
Me
H
Me
H
Et
Me
Me
Br
H
Et
Me
Me
H
Problem 16.07 (level 1; chapters 6, 7 and 8)
In the following four transformations, give detailed mechanisms for the steps indicated.
OH
H
pyridine
OMs
H
H
HO
NaOH
H 2 O
MeSO 2 Cl
(MsCl)
(a)
(b)
(c)
(d)
N
H
N
Me Me
MeI
KOH
heat
H
H
Me 2 N
H
Br
OH
H 2 SO 4
Br
O
Mg
Et 2 O
O
O
HO
H +
H 2 O
OH
HO
NH 2
HN
Ac 2 O
O
CH 3
CH 3 COCl
AlCl 3
HN
O
CH 3
O
CH 3
NH 2
O
CH 3
KOH
For each sequence, explain why the intermediary steps are advantageous in obtaining the product shown.