Regioselective Hydroformylation of Terminal Alkenes
COMMUNICATIONS
The reaction mixture was saturated with synthesis gas applying
three cycles of careful evacuation and refilling with synthesis
gas [CO/H2 (1:1)]. The solution was magnetically stirred em-
ploying a cross-type stirring bar for 20 h [228C, approx. 1 bar
CO/H2 (1:1)]. Reaction progress (conversion) can be moni-
tored by following the gas consumption. After full conversion
(in most cases after 20 h) the solution was concentrated and the
resulting crude product was purified by bulb-to-bulb distilla-
tion.
(entry 30) did not disturb the ligandꢁs hydrogen bonding
system as reflected in the high regioselectivity found for
these systems. The chemoselectivity profile of the rhodi-
um/6-DPPon (1) catalyst allows the regioselective hy-
droformylation of a terminal alkene in the presence of
a 1,2-disubstituted alkene function (entry 31). However,
if the internal alkene is part of an a,b-unsaturated ester a
competing hydrogenation reaction is observed which
leads after prolonged reaction time to the product aris-
ing from a tandem hydroformylation-hydrogenation re-
action (entry 26). On the other hand, a trisubstituted
enoate function is neither hydrogenated nor hydrofor-
mylated under these hydroformylation conditions (en-
try 25).
Caution: Synthesis gas is toxic and explosive, all operations
should be performed in a well-ventilated fume hood!
Acknowledgements
This work was supported by the Fonds der Chemischen Indus-
trie, the Alfried Krupp Award for young university teachers of
the Krupp foundation (to BB) and BASFAG.
In summary, the rhodium/6-DPPon (1) catalyst allows
for the first time a room temperature/ambient pressure
regioselective hydroformylation of terminal alkenes
with low catalyst loadings in good activity. The general-
ity of this catalyst under these conditions was demon-
strated for a wide range of structurally diverse alkenes
equipped with many important functional groups.
Thus, this practical and highly selective hydroformyla-
tion protocol, which omits the need for special pressure
equipment, should find wide application in organic syn-
thesis.
References and Notes
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Experimental Section
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General Procedure for the Room Temperature/
Ambient Pressure (RTAP) Hydroformylation
A Schlenk tube (10 to 15 mLvolume) connected to the RTAP
hydroformylation apparatus (see Figure 1) was loaded with
[Rh(CO)2acac] (2.5 mg, 9.7 mmol) and 6-DPPon (1) (13.5 mg,
48.4 mmol) under an atmosphere of argon. Then THF
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Figure 1. RTAP hydroformylation apparatus.
Adv. Synth. Catal. 2005, 347, 1488 – 1494
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