Page 32 - Academic Press Encyclopedia of Physical Science and Technology 3rd Organic Chemistry

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Encyclopedia of Physical Science and Technology EN001F-4 May 7, 2001 16:19

84 Acetylene

aldehydes and ketones in the presence of potassium hy- line required the addition of water to suppress nucleophilic
droxide and polar solvents yield acetylenic alcohols and addition of the amine across the triple bond.
diols. A current site of Russian research is the Institute Trofimov views oligomerization as proceeding simul-
of Organic Chemistry of the Russia Academy of Sci- taneously via the following routes:
ences, at Irkutsk, Siberia. B. A. Trofimov and co-workers
have utilized KOH–dimethyl sulfoxide (KOH–DMSO) as   + − (13)
✭N: + HC CH −→ ✭N CH CH
a superbase medium for a series of novel, acetylene-based
 + −
reactions. Some of the reaction systems developed by ✭N CH CH + C 2 H 2 −→
Trofimov are described in this section.
 +
|✭N CH CH (CH CH) n−1 (14)
A. Pyrroles and Vinylpyrroles from Acetylene CH CH 2 |OH −
and Ketoximes
(CH 3 ) 2 SO + KOH −→
←−
The reaction of excess acetylene with ketoximes in KOH–
DMSO medium under pressure at 70–140 C yields a mix- − +
◦
K + H 2 O
CH 3 S CH ←→ CH 3 S CH 2
2
ture of pyrroles and N-vinylpyrroles. The reaction has ↓ (15)

been studied intensively with aliphatic, alicyclic, and aro- O O −
matic ketoximes and has become known as the Trofimov
I
reaction.
R 1 CH 2 R 2 DMSO-KOH
+ −
C C 2 H 2 I + C 2 H 2 ⇐⇒ K |(CH 3 ) 2 SO|C CH 2
II (16)
N
OH
II + nC 2 H 2 −→
R 2 R 2
− +
HC C |CH CH| n−1 CH CH |(CH 3 ) 2 SO|K
(17)
R 1 R 1
N N
H
− C 2 H 2
CH CH 2 OH + CH CH −→ HO CH CH 2 −−−→
−
This method makes available many substituted pyrroles CH CH (CH CH) n OH (18)
−
not readily synthesized. By using a limited or stoichio-
The products are interesting because of their polyene,
metric amount of acetylene, the pyrrole can be made the
linear structure, solvent solubility, and conductive
predominant product. The N-vinylpyrroles readily poly-
properties.
merize by a free-radical mechanism using azobisisobuty-
ronitrile as the initiator.
C. Reactions of Triads: S 8 –KOH–DMSO,
Se 8 –KOH–DMSO, Te–KOH–HMPA
B. Oligomers from Acetylene
in KOH–NH 3 –DMSO Media A number of interesting transformations reported by
Trofimov and co-workers were based on the reaction of
Trofimov observed that low molecular weight oligomers
S 8 ,Se 8 , and tellurium with acetylene in DMSO–KOH
of the polyene type could be formed from acetylene in
or HMPA (hexamethylphosphoramide)–KOH medium to
aKOH–NH 3 –DMSO system at 80–120 C under pres-
◦
yield the corresponding divinyl compounds:
sure (12–18 atm). The oligomers were deep brown to
yellow solids, readily soluble in acetone, and insoluble 1 DMSO
C 2 H 2 + S 8 + KOH + H 2 O −−−−→ 2(H 2 C CH) S
in hexane and melted with decomposition at 300–400 C. 2 2
◦
80−120 C
◦
The products by infrared examination contained C O,
C O, and OH functionalities, but no nitrogen. Yields The reaction requires aprotic solvents such as DMSO
based on acetylene consumed averaged 75–88%. The and HMPA for satisfactory yields, with both solvents be-
oligomers were paramagnetic and conductive. Moderately ing approximately equal in performance (DMSO, 80%;
polar amines such as triethylamine could be substituted for HMPA, 76% yields). A small amount of water is required
ammonia with equivalent results. However, the use of ani- in the reaction to function as a proton transfer agent.