Chemistry Reference
In-Depth Information
Tab. 4.48.
A comparison of various methods for producing DCC.
Entry
Method
Yield (%)
DCC
Ref.
Starting material
Reagent, reaction conditions
1
dicyclohexylurea
1. COCl
2
, tBuOMe (MTBE)
2. NH
3
98
1253
2
dicyclohexylurea
1. P
2
O
5
, pyridine, sand
2. petroleum ether, water
76
1255
3
dicyclohexylurea
1. POCl
3
,CH
2
Cl
2
2. NaOH, H
2
O
89
1257
4
cyclohexylisocyanate (2 mol)
1. Ti(OBu)
4
2. acetone, H
2
O
98
1285
5
cyclohexylisocyanide
cyclohexylamine
1. Se, DBU, THF
2. O
2
87
1282
6
cyclohexylisocyanide
1. Pd(OAc)
2
,I
2
,Na
2
CO
3
,
MeCN
2. O
2
67
1283
cyclohexylamine
General procedure. 4-Thiazolidinones 1697 by a 3CR [1251]:
The appropriate amine
or amino acid ester 1694 (1.0 mmol) and aldehyde 1695 (2.0 mmol) were stirred in
THF at around 0
C for 5 min, and then mercaptoacetic acid 1696 (3.0 mmol) was
added. After a further 5 min, DCC (1.2 mmol) was added to the reaction mixture at
0
C, and stirring was continued for a further 50 min at room temperature. DCU
(dicyclohexylurea) was removed by filtration, the filtrate was concentrated to dry-
ness under reduced pressure, and the residue was taken up in ethyl acetate. The
organic phase was successively washed with 5% aq. citric acid, water, 5% aq. so-
dium hydrogen carbonate, and brine. It was then dried over sodium sulfate and the
solvent was removed under reduced pressure to leave the crude 1697, which was
purified by column chromatography on silica gel using hexane/ethyl acetate as
eluent.
4.6
Divalent Compounds
All of the synthesized compounds described thus far in this chapter have been of
monovalent reactivity, i.e. the compounds consist of one or more active functional
groups of the same selectivity and, where appropriate, one or more further non-active
functions. Difunctional compounds such as isocyanato-chloroformate 108 [60] (Sec-
tion 4.2.1), 446 [300] (Section 4.3.1.4), isocyanato-carbamoyl chloride 179 [111, 112]
(Section 4.2.2.2), isocyanato acid chloride 1231 [447] (Section 4.3.5.4), and 1343
[1016] (Section 4.4.2.3), also fall into this category because all of their functions are
of the same selectivity, in these examples electrophiles.
