Full Papers
In summary, we improved the selectivity and yield for the n-
aldehyde and acyloin of every applied substrate, obtaining
a general method for the direct conversion of olefins into acy-
loins in one preparative step. This orthogonal tandem catalysis
is advantageous towards a one-pot reaction wherein the sub-
sequent addition of the carbene precursor and base favour the
aldol reaction, which led to low selectivities.
kenes. It is conceivable that ethoxylation of 3 will directly lead
to a surfactant. Thereby, a surfactant can be synthesised within
only two preparative steps.
Conclusion
We described an advanced development of the tandem hydro-
formylation/acyloin reaction, which leads directly to acyloins
from olefins by suppressing numerous side products. We
found new catalyst systems for each reaction, by changing re-
agents and conditions step by step, which was necessary be-
cause of the interactions between both catalyst systems. This
tandem catalysis is finally transferable to various substrates. Ex-
cellent overall reaction selectivities up to >99% have been
achieved with excellent yields up to 96% for the desired inter-
mediate n-aldehydes and very good yields up to 79% for the
final acyloin products were obtained. For the side products,
only negligible amounts up to 5% were observed. Further-
more, we observed foaming properties and determined surfac-
tant activity after attaching a polar head group to the acyloin
starting from 1-decene, which opens up a new class of surfac-
tants.
Both acyloin products from 5-hexenenitrile (Table 4, no. 4.5)
and methyl undecylenoate (no. 4.6) are interesting precursors
for potential monomers in polymerisation, owing to their a,w-
functionalisation. A possible application of long-chain acyloins,
for example, from 1-decene (no. 4.4) is not visible at first
glance. Owing to the long carbon chain and the alcohol
moiety, the acyloin backbone can be used as a nonpolar pre-
cursor in surfactants creating a double-tail surfactant with two
linear alkyl chains. Attaching succinic acid anhydride as a linker
to the acyloin 3, which resulted in 69% of 3a, we were able to
attach poly(ethylene glycol) 600 (PEG-600) yielding 3b almost
quantitatively (Scheme 6). This synthesized double-tail mole-
Experimental Section
General procedure of the tandem hydroformylation/acyloin
reaction
Rh(CO) (acac) (0.03 mmol), L4 (0.09 mmol), C2 (0.6 mmol) and
2
Scheme 6. Three-step reaction pathway for the double-tail surfactant 3b.
1
(6 mmol) were dissolved in a 40 mL custom-made stainless-steel
autoclaves in 5 mL NMP. After adding triethylamine (1.2 mmol) the
autoclave was pressurised with 30 bar syngas (CO/H =1:1) and the
2
cule with a polar head group showed foaming activity during
the work-up process. A quantification of the surface active
properties revealed a critical micelle concentration (C.M.C.) of
mixture was stirred at 908C for 16 h magnetically. After cooling to
RT the autoclave was depressurized and flushed with argon. For
the GC measurements, a sample of the mixture was taken and ana-
lysed by GC with dodecane as internal standard and isopropyl al-
cohol as additional solvent. Otherwise the reaction mixture was
concentrated and purified by column chromatography (cyclohex-
ane/ethyl acetate 100:1!5:1) yielding white solid 12-hydroxydoco-
À1
À1
0
.13 gL , a water solubility of 0.022 gL and a surface ten-
À1
sion of 33.1 mNm (Figure 4). The value of the C.M.C. was
low, attributable to the poor water solubility. Therefore, a modi-
fication to shorter chain length should increase the water solu-
bility. In this way, a new synthetic route and a new class of sur-
factants has been opened up employing three steps from 1-al-
1
san-11-one (3). H NMR (400 MHz, CDCl3): d=0.90 (m, 6H), 1.29 (m,
2
9H), 1.45–1.64 (m, 4H), 1.83 (m, 1H), 2.46 (m, 2H), 3.50 (d, J=
13
4.8 Hz, 1H), 4.18 ppm (m, 1H); C NMR (100 MHz, CDCl3): d=14.5
2C), 23.1 (2C), 24.1, 25.2, 29.6, 29.7, 29.7, 29.8, 29.8, 29.9 (2C),
0.0 (2C), 30.0, 32.3 (2C), 34.2, 38.3, 76.8, 213.0 ppm; HRMS
(
3
+
(
ESI) analysis calcd for C H O [M+H]
341.34141, found
22
45
2
À1
3
41.34083. IR: n˜ =3322, 2913, 2848, 1709 cm .
The characterisation data of other acyloin products can be taken
[17]
from the literature.
Procedure for the synthesis of 3b
We followed the procedure according to dl-a-tocopherol succinate
yielding 69% of 3a and TPGS-750M yielding 99% of 3b from the
[29]
1
experimental section in the literature. For 3b: H NMR (400 MHz,
CDCl ): d=0.87 (m, 6H), 1.25 (m, 30H), 1.56 (m, 2H), 1.71 (m, 2H),
3
2
4
.35 (m, 1H), 2.45 (m, 1H), 2.56 (bs, 1H), 2.68 (m, 3H), 3.64 (m,
8H), 4.24 (m, 2H), 4.98 ppm (m, 1H); C NMR (100 MHz, CDCl3):
13
d=214.3, 222.9, 23.3, 25.1, 25.4, 29.1, 29.2, 29.4, 29.5, 29.5,
29.5, 29.6, 29.6, 29.7, 29.7, 29.8, 30.7, 32.1, 34.4, 38.8, 62.0, 63.6,
64.1, 69.3, 69,4, 70.6, 70.8, 70.9, 72.7, 79.0, 172.3, 172.1, 207.7 ppm;
Figure 4. Pendency of the surface tension to the concentration of the surfac-
tant 3b.
ChemCatChem 2015, 7, 2607 – 2613
2612
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim