Reduction OxidationFGI FGIH 2 NCH 3O 2 NO 2 NC CO OOH OHThe final stage is to consider the disconnection of both the methyl and nitro
groups.
Key:
Indicates the real compound (derived from the
= synthon) that is used in the reconnection reaction.O 2 NO 2 N+ +NO 2
+CH
3CH 3 CH 3CH 3−− +Toluene is a readily available compound, so the best disconnection is the nitro
group. This is also supported by the fact that it is easy to form 4-nitrotoluene by
nitration of toluene. Consequently, the complete synthesis is
H 2 / PdH 2 N C 2 H 5 OH / H+H
2 NCH (^3) HNO CH 3 COOC 2 H 5
3
H 2 SO (^4) O
2 N
KMnO 4
H+O
2 N
COOH COOH
The disconnection approach may be used for both linear and convergent
syntheses (see section 10.2). However, in both cases the design of a synthesis
using the approach must take into account the following:
1. the order of disconnection could influence the ease and direction of subse-
quent reactions;
2. the need to protect a reactive group in a compound by the use of a suitable
protecting agent and
3. the need to incorporate chiral centres into the structure (see section 10.2.3).
A wide range of disconnections linked to suitable reconnections are known
(Table 10.3). However, a number of functional groups are usually best intro-
duced by FGI (Table 10.4). Once again it cannot be over-emphasized that their
use will depend on the experience of the designer, which only improves with
usage and time.
DESIGNING ORGANIC SYNTHESES 217