Chemistry Reference
In-Depth Information
OR
OR
N
P
N
P
OR
OR
n
RONa
Cl
Cl
P
NHR
NHR
Cl
Cl
Cl
RNH
2
Cl
N
N
N
P
N
P
P
P
Cl
Cl
P
P
N
N
N
NHR
NHR
n
Cl
Cl
RM
R
R
N
P
N
P
R
R
n
obtained by previous dehydration of a supported
urea (Fig. 8.18) [73,74]. The spent reagent is the
starting urea, which can be reconverted to the
carbodiimide.
Fig.
8
.16
Polyphosphazenes.
targeted molecule than in the way it is made;
thus, instead of displaying a catalogue of reactive
polymers, this section has been arranged according
to the expected molecules to be synthesised with
respect to the required polymer-supported reagent.
3.2 Alcohols
The hydrolysis of alkyl halides into alcohols or the
recovery of free alcohols from formate esters is per-
formed with anion-exchanged resins in their formate
or bicarbonate form (Fig. 8.19). Reaction of primary
halides in acetone or tetrahydrofuran gave the
formate esters in good yields; they are hydrolysed to
the corresponding alcohols by a brief treatment with
hydrochloric acid. Alternatively, reaction of primary
and secondary alkyl bromides or iodides in tetrahy-
dropyran or 1,4-dioxane gave the corresponding
alcohols directly in good yields [75]. The latter reac-
tion can be carried out successfully in the presence
of other base-sensitive functions such as ester or
amide groups.
However, the usual way of getting alcohols is the
reduction of aldehydes and ketones; several borane
3.1 Acid chlorides and anhydrides
The immobilised form of the Appel system P(C
6
H
5
)
3
/
CCl
4
is obtained from a triphenylphosphine-grafted
polystyrene resin (Fig. 8.17); this allows the simple
conversion of some free carboxylic acids into their
corresponding chloride without the evolution of
HCl.
Aliphatic and aromatic acids are transformed at
room temperature and the recycling of the phos-
phine oxide back to the initial phosphine may be
possible [71,72].
Acid anhydrides are obtained by dehydration of
acids with a polymer-supported carbodiimide that is
