Chemistry Reference
In-Depth Information
Typical procedure. Anthracene 9-carboxylic acid chloride 1341 [1013]:
A solution of
anthracene 1340 (5 g) and oxalyl chloride (30 mL) in nitrobenzene (150 mL) was
heated to 120
C, and then the temperature was raised to 240
C over a period of
5-6 h. The corresponding acid chloride 1341 was obtained in 67% yield.
Under Friedel-Crafts conditions (AlCl
3
,CS
2
), oxalyl chloride reacts with aro-
matic hydrocarbons to give carbonyl chlorides, which are hydrolyzed by water to
give carboxylic acids. The AlCl
3
-mediated chlorocarbonylation of arenes with oxalyl
chloride has been used in the preparation of symmetrical and unsymmetrical
diaryl ketones [946] (see also Section 4.3.6).
4.4.2.3
Diphosgene
Isocyanato acid chlorides, such as 3-isocyanatopropanoyl chloride 1343, having two
different, highly reactive electrophilic groups, are e
cient reagents for introducing
amino acid residues into organic compounds [161] and polymers [1014]. 3-Iso-
cyanatopropanoyl chloride 1343 has been prepared by the reaction of 3-amino-
propanoic acid hydrochloride 1342 with phosgene [1015]. However, the yield is
only 36%, and hydrogen chloride must be introduced to increase the yield to 92%.
6-Isocyanatohexanoyl chloride can only be prepared in trace amounts with phos-
gene unless additional hydrogen chloride is used.
A procedure using trichloromethyl chloroformate (diphosgene) has been suc-
cessfully applied in the synthesis of isocyanato acid chlorides and isocyanato
chloroformates from amino acids and amino alcohols, respectively [161, 1016].
O
CCl
3
OCOCl
O
¯Cl
+
H
3
N
Dioxane,
55-60 °C
OH
OCN
Cl
1342
1343
Typical procedure. 3-Isocyanatopropanoyl chloride 1343 [1016]:
Caution! Diphosgene is
toxic. The reaction should be carried out in a well-ventilated hood. A 500-mL, two-
necked flask was equipped with a thermometer and a reflux condenser protected at
the top by a calcium chloride guard tube. A Teflon-coated magnetic stirring bar,
anhydrous dioxane (250 mL), finely pulverized 3-aminopropanoic acid hydro-
chloride 1342 (b-alanine
HCl) (12.6 g, 0.1 mol), and diphosgene (23.8 g, 14.4 mL,
0.12 mol) were placed in the flask in the order specified. The mixture was stirred
and heated at 55-60
C. After ca. 5 h, the solid had completely dissolved to give a
clear solution. Heating was discontinued after a total of 7 h and the solvent was
removed under reduced pressure. The residual oil was rapidly distilled under re-
duced pressure and a distillate amounting to 11.2-12.4 g (84-93%) was collected
at 75-85
C/20 mmHg. Redistillation afforded 10.5-11.8 g (79-88%) of 3-iso-
cyanatopropanoyl chloride 1343 as a colorless liquid (bp 92-94
C/25 mmHg).
Comment: Although the reaction can be carried out with an equimolar amount of tri-
chloromethyl chloroformate, a longer time (15-20 h) is required to reach completion,
and the yield is somewhat reduced. If a 1.5-2.0-fold excess of trichloromethyl chloro-
