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the isomeric 2-(4-methoxyphenyl)-1-phenylethanone was
formed.
were able to isolate 92% of C6H5COCD3 after 7 h, 80% of 4-
FC6H4COCD3 after 5 h, 92% of 4-CH3C6H4COCD3 after 3 h, and
96% of 4-MeOC6H4COCD3 after 1 h. According to NMR analysis
all of these products had isotopic purities of approximately
93%. See the Supporting Information for further details on the
purity of the resulting ketones and physical data of the deu-
teriated products.
Replacement of cetyltrimethylammonium bromide (CTAB) by
other cationic surfactants had only a small effect on the reac-
tion efficiency (Table 2, entries 2–4 and entry 7). Some anionic
Table 2. Dependence of the hydration of ethynylbenzene on the nature
of the surfactants.[a]
In conclusion, the simple hydration protocol described here
can be regarded as a green version of this key reaction. It can
potentially be applied to a wide range of substrates, is free of
toxic mercury or late-metal catalysts, and the products can be
isolated just by phase separation.
Entry
Surfactant[b]
Isolated PhCOMe [%][d]
1
2
3
4
5
6
7
8
9
SDS
DTAB
TTAB
CTAC
CTAB
CTAB[c]
OTAB
Marlipal
SDBS
72
96
95
88
87
81
96
83
90
Experimental Section
In a representative experiment, a microemulsion composed of 1-
ethynyl-4-methoxybenzene (19.95 g, 151 mmol, 0.8 wt% of the
starting reaction mixture), CTAB (82.5 g, 3.3 wt%), 1-PrOH (206 mL,
6.6 wt%), and triply distilled water (TDW, 2.23 L, 89.3 wt%) was
placed either in a glass vessel or in an autoclave. Hydrochloric acid
was added to form a 0.33m microemulsion. The reaction mixture
was heated to 808C for 24 h. After cooling, the microemulsion was
broken by addition of NaCl (30 g), and the aqueous phase was ex-
tracted with ether (2ꢁ50 mL). Neutralization with aqueous
NaHCO3, drying (MgSO4), and distillation at 2.0 Torr (1 Torr=1.333ꢁ
102 Pa) afforded 20.0 g (88%) of analytically pure 4-methoxyaceto-
phenone. See the Supporting Information for different reaction
conditions and physical data of some other ketones obtained by
alkyne hydration.
[a] Reaction conditions as described for Table 1, except that all experi-
ments were performed for only 3 h. [b] SDS: Sodium dodecylsulfate;
DTAB: dodecyltrimetylammonium bromide; TTAB: tetradecyltrimethylam-
monium bromide; CTAC: cetyltrimethylammonium chloride; CTAB: cetyl-
trimethylammonium bromide; OTAB: octadecyltrimethylammonium bro-
mide; Marlipal: C12ÀC14 alcohols polyoxyethyleneglycol ethers (7-EO);
SDBS: sodium 4-dodecylbenzenesulfonate. [c] The hydrochloric acid was
replaced by 0.33m hydrobromic acid. [d] Average of at least two experi-
ments that did not differ by more than Æ2%.
Acknowledgements
and non-ionic additives (e.g., sodium dodecylsulfate, C12–C14 al-
cohols–polyoxyethylene glycol ethers), however, had a more
significant effect on the process. In none of the short experi-
ments of Table 2 did the yield of vinylic side product men-
tioned in Table 1 exceed 0.3%. The presence of the vinyl hal-
ides could be completely eliminated by using sodium 4-dode-
cyl benzene sulfonate (SDBS) as surfactant and by replacing
the hydrochloric acid by 0.33m aqueous sulfuric acid. When
using SDBS, however, it proved necessary to prepare the mi-
croemulsions at temperatures between 50 and 558C and
extend the reaction times. On the other hand the SDBS surfac-
tant, which is sparingly soluble at room temperature, could be
recovered upon cooling of the reaction mixture. 1-Ethenyl-4-
methylbenzene, 4-ethynyl-1-fluorobenzene, and 1-(1,1-dime-
thylethyl)-4-ethynylbenzene gave the corresponding ketones
in quantitative yields after 16 h at 1408C. Under these condi-
tions the disubstituted 1-propyn-1-ylbenzene was hydrated to
the extent of 60%.
Financial support of this study by The Israel Science Foundation
through grant number 229/10 is kindly acknowledged.
Keywords: alkynes
·
green chemistry
·
homogeneous
catalysis · microemulsions · synthetic methods
[1] M. Berthelot, Acad. Sci. C. R. 1860, 50, 805–808.
and references therein.
[4] a) A. Desgrez, Ann. Chim. 1894, 8, 209; b) R. Schaad, V. N. Ipatieff, J. Am.
[7] M. Kutscheroff, Ber. Bunsen-Ges. 1881, 14, 1540–1542.
[8] a) R. Jira, R. T. Laib, H. M. Bolt, in Ullmann’s Encyclopedia of Industrial
Chemistry, 5th ed. (Eds.: W. Gerharz, Y. S. Yamamoto, F. T. Campbell, R.
Pfefferkorn, J. F. Rounsaville), VCH, Weinheim, 1985, pp. 31–44; b) R.
in.
The hydration of the alkynes in aqueous microemulsions is
coupled with a selective hydrogen exchange. Therefore, the re-
placement of the water by D2O can be used for an efficient
preparation of terminal CD3-substituted ketones. The use of
microemulsions permits recovery of most of the D2O in a way
that the deuterium content in the fourth run is still as high as
93%, even when using non-labeled HCl and 1-PrOH. Under the
conditions of Table 1 (1408C) but replacing H2O by D2O, we
696, 7–11; b) G. A. Carriedo, S. López, S. Suꢃrez-Suꢃrez, D. Presa-Soto, A.
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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