Minimization of side reactions in bromine magnesium exchanges with i-PrMgCl/LiCl and s-BuMgCl/LiCl mixtures

Article abstract of DOI:10.1021/op0600153

The efficiency of halogen-magnesium exchange reactions can dramatically be increased by the addition of LiCl. However, also the organic substituents at the magnesium center of the Grignard reagent play an important role. In a competitive reaction gaseous side products are formed. In the presence of LiCl this interfering reaction is suppressed. Thus, carrying out bromine-magnesium exchanges with RMgCl/LiCl TurboGrignard solutions instead of RMgCl gives better results (R = i-Pr, s-Bu). The application either of i-PrMgCl/LiCl or of s-BuMgCl/ LiCl in halogen-magnesium exchange reactions results in higher conversions and also in less gaseous side products, facts that should be considered for scale-up processes.

Full text of DOI:10.1021/op0600153

Organic Process Research & Development 2006, 10, 733−738
Minimization of Side Reactions in Bromine Magnesium Exchanges with
i-PrMgCl/LiCl and s-BuMgCl/LiCl Mixtures
Dieter Hauk, Sebastian Lang, and Alexander Murso*
Chemetall GmbH, Trakehner Strasse 3, D-60487 Frankfurt am Main, Germany
Scheme 1. First synthesis of a Grignard reagent via
bromine-magnesium exchange reaction
Abstract:
The efficiency of halogen-magnesium exchange reactions can
dramatically be increased by the addition of LiCl. However,
also the organic substituents at the magnesium center of the
Grignard reagent play an important role. In a competitive
reaction gaseous side products are formed. In the presence of
LiCl this interfering reaction is suppressed. Thus, carrying out
bromine-magnesium exchanges with RMgCl/LiCl TurboGrig-
nard solutions instead of RMgCl gives better results (R ) i-Pr,
s-Bu). The application either of i-PrMgCl/LiCl or of s-BuMgCl/
LiCl in halogen-magnesium exchange reactions results in
higher conversions and also in less gaseous side products, facts
that should be considered for scale-up processes.
Scheme 2. LiCl accelerated halogen-magnesium exchange
reactions
Meanwhile, several examples illustrating the superiority
of mixtures of Grignard solutions with LiCl (hereafter
referred to as TurboGrignard) in halogen-magnesium ex-
change reactions have been published.7 These reactions, using
commercially attractive organic halides are becoming more
and more relevant for industrial applications.
Halogen-magnesium exchanges are equilibrium pro-
cesses, favoring the formation of the most stable Grignard
reagent (sp > sp2(vinyl) > sp2(aryl) > sp3(primary) > sp3-
(secondary)). However, the mechanism of halogen-magne-
sium exchange reactions is not fully understood, but a
halogenate complex is believed to be an intermediate.5 For
TurboGrignard reagents, it has been proposed that LiCl
breaks the polymeric aggregates of the Grignard, forming a
magnesiumate complex, in which the magnesium fragment
is more negatively charged and hence displays a higher
reactivity towards organic halides.5a,6 However, relatively
little is known about the influence of different s-alkyl
substituents at the magnesium center.
To develop commercially attractive mixtures of LiCl and
Grignard reagents for halogen-magnesium exchange reac-
tions, we decided to prepare THF solutions of i-PrMgCl/
LiCl and s-BuMgCl/LiCl. During this development work,
we obtained some interesting results on the difference
between i-PrMgCl/LiCl and s-BuMgCl/LiCl mixtures and
on the influence of LiCl in halogen-magnesium exchange
reactions, which are topics of the present report.
Introduction
Halogen-magnesium exchange reactions are the method
of choice for preparing functionalized organometallic com-
pounds.1 These exchange reactions show much higher
functional group tolerance than, for example, corresponding
exchanges with alkyl lithium reagents.2 In 1931, Pre´vost
reported the first example of a bromine-magnesium ex-
change, however, only in moderate yield (Scheme 1).3
Good conversions could only be obtained when aromatic
iodides or highly activated aromatic bromides, for example,
1-bromo-3,5-ditrifluoromethylbenzene, were employed.4 With
less activated bromides, long reaction times were needed,
and even then, only moderate conversions could be ob-
tained.1,5
The restrictions of halogen-magnesium exchange reac-
tions were overcome after the recent discovery of P. Knochel
and A. Krasovskiy that lithium chloride accelerates these
exchanges dramatically. Additionally, they showed that the
presence of lithium chloride results in higher yields of the
desired products (Scheme 2).6
* To whom correspondence should be addressed. Telephone: +49 (0)69 7165
2497. Fax: +49 (0)69 7165 3622. E-mail: alexander.murso@chemetall.com.
(1) Knochel, P.; Dohle, W.; Gommermann, N.; Kneisel, F. F.; Kopp, F.; Korn,
T.; Sapountzis, I.; Vu, V. A. Angew. Chem., Int. Ed. 2003, 42, 4302.
(2) (a) Wittig, G. Chem. Ber. 1938, 71, 1903. (b) Jones, R. Org. React. 1951,
6, 339. (c) Gilman, H. J. Am. Chem. Soc. 1939, 61, 106. (d) Parham, W. J.
Org. Chem. 1976, 41, 1187. (e) Parham, W. J. Org. Chem. 1975, 40, 2394.
(f) Parham, W. J. Org. Chem. 1976, 41, 2704. (g) Parham, W. J. Org. Chem.
1977, 42, 260. (h) Parham, W. J. Org. Chem. 1977, 42, 257. (i) Tucker, C.
J. Am. Chem. Soc. 1992, 114, 3983.
(3) Pre´vost, C. Bull. Soc. Chim. Fr. 1931, 49, 1372.
(4) Leazer, J. L., Jr.; Cvetochiv, R.; Tsay, F.-R.; Dolling, U.; Vickery, T.;
Bachert, D. J. Org. Chem. 2003, 68, 3695.
(5) (a) Knochel, P. Handbook of Functionalized Organometallics; Wiley-
VCH: Weinheim: 2005. (b) Bailey, W. F.; Patricia, J. J. J. Organomet.
Chem. 1988, 352. (c) Farnham, W. B.; Calabrese, J. C. J. Am. Chem. Soc.
1986, 108, 2449. (d) Reich, H. J.; Philipps, N. H.; Reich, I. L. J. Am. Chem.
Soc. 1985, 107, 4101.
(6) (a) Knochel, P.; Krasovskiy, A. EP 1 582 523 A1, 2005. (b) Knochel, P.;
Krasovskiy, A. Angew. Chem., Int. Ed. 2004, 43, 3333.
(7) (a) Kopp, F.; Krasovskiy, A.; Knochel, P. Chem. Commun. 2004, 2288. (b)
Ren, H.; Krasovskiy, A.; Knochel, P. Org. Lett. 2004, 6, 4215. (c) Ren, H.;
Krasovskiy, A.; Knochel, P. Chem. Commun. 2005, 543. (d) Sapountzis,
I.; Lin, W.; Kofink, C.; Despotopoulou, C.; Knochel, P. Angew. Chem.,
Int. Ed. 2005, 44, 1654. (e) Baron, O.; Knochel, P. Angew. Chem., Int. Ed.
2005, 44, 3133.
10.1021/op0600153 CCC: $33.50 © 2006 American Chemical Society
Published on Web 06/24/2006
Vol. 10, No. 4, 2006 / Organic Process Research & Development
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Figure 1. Comparison of i-PrMgCl/LiCl mixtures (3, 4; solid lines) with s-BuMgCl/LiCl solutions (5, 6; dashed lines) in the
benchmark exchange reaction with bromobenzene.
Table 1. Grignard solutions and Grignard/LiCl mixtures
used for the experiments
Scheme 3. Benchmark reaction of i-PrMgCl/LiCl (3, 4)
and s-BuMgCl/LiCl solutions (5, 6) with bromobenzene
RMgCl
LiCl:RMgCla
[OH]- b
[wt%]c
1
2
3
4
5
6
i-PrMgCl
s-BuMgCl
i-PrMgCl
i-PrMgCl
s-BuMgCl
s-BuMgCl
-
1.99
2.15
1.78
1.35
1.26
1.25
20
25
18
14
15
15
-
0.79
1.02
1.13
0.96
Results and Discussion
A plot of the conversion versus reaction time illustrates
the progress of the reactions (Figure 1). For both i-PrMgCl/
LiCl mixtures (3, 4) as well as for s-BuMgCl/LiCl solutions
(5, 6), it is obvious that in each system the conversion
improves with higher LiCl content. For all four curves, the
shape is almost identical, and after a certain time the high
rate of conversion observed at the beginning of the reactions
decreases.
The reduction in rate is similar for both s-BuMgCl
TurboGrignard solutions (5, 6) and for both i-PrMgCl
TurboGrignard reagents (3, 4). This property seems to be
insensitive to the LiCl content. However, the apparent rate
decrease is greater when using i-PrMgCl/LiCl mixtures (3,
4), than when carrying out the exchanges with s-BuMgCl/
LiCl solutions (5, 6). Hence, at a given point (marked X in
Figure 1), s-BuMgCl/LiCl solutions (5, 6) display a higher
rate of conversion than i-Pr TurboGrignard reagents (3, 4),
finally resulting in higher conversions. From these experi-
ments, one can conclude that, not only the content of LiCl
present in solution during the exchange reaction is important
for a fast halogen-magnesium exchange, but also the nature
of the organic fragment attached to the magnesium center.
Just one methyl group more results in indeed small, but
obvious, changes.8
a LiCl as [Li]+. b In [mmol/g]. c RMgCl as total base [OH]-.
Synthesis
Concentrated THF solutions of i-PrMgCl 1 (20 wt %)
and s-BuMgCl 2 (25 wt %) were prepared by standard
oxidative addition of the corresponding chlorides to mag-
nesium turnings. An excess of dry LiCl was added, and the
dissolved amount was determined by wet analyses. Stepwise
dilution with THF gave higher concentrations of dissolved
LiCl. The prepared i-PrMgCl and s-BuMgCl solutions and
their mixtures with LiCl are listed in Table 1.8
To obtain a reliable comparison of the abovementioned
Grignard/LiCl mixtures 3-6 in halogen-magnesium ex-
change reactions, we chose deliberately the very slow
exchange with unactivated, electron-poor bromobenzene as
a benchmark reaction, to be able to detect even small
differences in the behavior of the TurboGrignard reagents.
Stoichiometric amounts of bromobenzene were reacted with
Grignard/LiCl mixtures 3-6, and reaction aliquots were
taken after defined reaction times and subjected to quantita-
tive GC analyses after derivatization of the aliquots with
iodine (Scheme 3).
The reason for this different behavior of i-PrMgCl and
s-BuMgCl TurboGrignard solutions in bromine-magnesium
exchange reactions was unclear. During the exchange reac-
(8) More detailed information, figures and tables are given in the Supporting
Information.
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Table 2. Results from inline IR and gas flow measurements
Inline IR Results
concentrateda
[wt %]
IR mode
period of
analyses [min]
gradient
(Figure 3)
relative
ratec
Grignard
LiCl:RMgCl
alkyl bromide
at [cm-1
]
i-PrMgCl (1)
s-BuMgCl (2)
i-PrMgCl/LiCl (4)
s-BuMgCl/LiCl (6)
20
25
14
15
-
-
1.02
0.96
i-PrBr
s-BuBr
i-PrBr
s-BuBr
1227
1208
1227
1208
150-210
150-210
150-210
150-210
-4.20 × 10-4
-7.46 × 10-5
-8.01 × 10-5
-3.67 × 10-5
11.40
2.03
2.18
1.00
Gas Flow Results
alkyl bromide
concentrateda
[wt %]
gas volume
[L]b
period of
analyses [min]
gradient
(Figure 4)
relative
ratec
Grignard
LiCl:RMgCl
i-PrMgCl (1)
s-BuMgCl (2)
i-PrMgCl/LiCl (4)
s-BuMgCl/LiCl (6)
20
25
14
15
-
-
1.02
0.96
i-PrBr
s-BuBr
i-PrBr
s-BuBr
3.48
1.16
1.78
0.50
221-321
137-291
146-335
130-316
2.73 × 10-2
5.20 × 10-3
6.80 × 10-3
2.00 × 10-3
13.65
2.60
3.40
1.00
a As total base [OH]-. b From start until end of the reaction. c Via division of the gradients by the gradient of the slowest reaction with TurboGrignard 6.
cm-1 could easily be identified in the waterfall diagrams.8
To determine the kinetics of each reaction, the period at
Scheme 4. Competitive formal HBr elimination in
halogen-magnesium exchange reactions
constant reaction conditions, i.e., after the end of the addition
of the alkyl bromide and at a constant temperature of 45
°C, were taken. The wetting of the surface of the diamond
IR dipper can be considered to be equal in all experiments.
This, together with the assumption of almost equal molar
coefficients of the extinction for both alkyl bromides (ꢀ )
Scheme 5. Reactions to study the kinetics of the HBr
elimination observed in halogen-magnesium exchange
reactions
constant, d ) constant), the law of Lambert-Beer can be
taken to determine the decrease of the concentration of the
alkyl bromides (log(I/I0) concentration).
Figure 2 depicts the decrease of the concentrations of the
alkyl bromides, using the law of Lambert-Beer. The values
for log(I/I0) concentration are relative to the intensity I0
at 150 min.8 It is obvious that the alkyl bromides are
consumed in these reactions. The curves show almost linear
behavior at constant reaction conditions; thus, the gradients
of the curves, obtained by linear regression, illustrate the
tions, the formation of gaseous products was observed, and
quantitative relationship between the four experiments.
GC/MS identified propane in solutions from exchange
Consequently, one can deduce the relative kinetics of the
reactions with i-PrMgCl/LiCl, and butane for the transforma-
tions with the s-BuMgCl TurboGrignard. These gases are
formed by reaction of TurboGrignard solutions with the
i-PrBr or the s-BuBr byproduct which results from the
four reactions. The results of these analyses are given in
Table 2.
The observed loss of concentration is higher for the
reactions of the Grignard solutions with the alkyl bromides
respective halogen-magnesium exchange. Formally, a HBr
in absence of LiCl (1, 2) than for the respective experiments
with the TurboGrignard solutions in the presence of LiCl
(4, 6). The formal HBr elimination from the reaction of
i-PrMgCl (1) with i-PrBr is approximately 5 times faster than
for the reaction carried out in the presence of LiCl, using
the i-PrMgCl/LiCl TurboGrignard solution (4). For the
reactions of s-BuBr with s-BuMgCl (2) and with s-BuMgCl/
LiCl (6), respectively, this difference is indeed smaller, yet
still a factor of ∼2. From these data, it is obvious that the
presence of LiCl in solution minimizes the side reaction of
Grignard solutions with alkyl bromides. This is a hint for
the low conversions observed for halogen-magnesium
exchange reactions, carried out in the absence of LiCl, as it
was state of the art before the discovery of Knochel: without
LiCl, these kinds of transformations are slow. In rather slow
halogen-magnesium exchanges, the reaction of formed alkyl
elimination takes place (Scheme 4).5,6
We think that this competitive HBr elimination is faster
for i-PrMgCl TurboGrignard (3, 4) than for s-BuMgCl/LiCl
mixtures (5, 6) and that this is the reason for the observed
differences in both the slope of the curves and extent of
conversions in the benchmark reaction of the different
TurboGrignard solutions with bromobenzene. To verify this
thesis, i-PrMgCl was reacted with i-PrBr, and s-BuMgCl was
reacted with s-BuBr both in the presence and absence of
lithium chloride (Scheme 5).
To quantify the kinetics of the HBr elimination reaction
in these experiments, they were monitored by inline IR and
gas flow measurements. Details are given in Table 2 in the
Experimental Section and in the Supporting Information.
Results from Inline IR Measurements. The specific IR
active modes of i-PrBr at 1227 cm-1 and s-BuBr at 1208
Vol. 10, No. 4, 2006 / Organic Process Research & Development
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735

Figure 2. Decrease of the concentrations of i-PrBr and s-BuBr, respectively, determined via inline IR measurements.
Figure 3. Gas evolution at constant reaction conditions in reactions of i-PrMgCl and s-BuMgCl with i-PrBr and s-BuBr, in the
presence and absence of LiCl, respectively.
bromide with unreacted Grignard is an important (and rather
fast) competitive reaction, consuming unreacted Grignard and
therefore lowering conversions.
Figure 2 also clearly shows the difference between the
two LiCl-containing TurboGrignard reagents (4, 6). In the
reaction of i-PrBr with i-PrMgCl/LiCl (4), one observes a
∼2 times faster decrease of the concentration of the alkyl
bromide than that in the reaction of s-BuBr with s-BuMgCl/
LiCl (6).
Results from Gas Flow Measurements. In addition to
inline IR, the experiments were monitored with a gas meter
to determine the evolution of the gaseous side products,
propane and propene, and butane and butene, respectively.
Figure 3 depicts the gas flow in the area of constant reaction
conditions after addition of the alkyl bromides to the
corresponding Grignard or TurboGrignard solutions. The
determined relative rates are higher than those obtained from
inline IR measurements, which is due to the minor accuracy
of the method.9 However, the obtained data are qualitatively
in accordance with those discussed for the inline IR
measurements and give the same trends (see Table 2).
Regarding the total gas evolved during the reactions of
the Grignard and TurboGrignard reagents with the respective
alkyl bromides (see Table 2), it is clear from the present
(9) Possible reasons for the differences are different vapour pressures of the
reaction mixtures or different solubilities of the gases in THF.
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discussion that in the absence of LiCl a much higher total
gas volume is observed than that in the presence of LiCl.
Also, the total gas volume is less in the reaction of
s-BuMgCl/LiCl with s-BuBr (6) than it is in the reaction of
i-PrMgCl/LiCl with i-PrBr (4) during comparable reaction
times. Hence, for scale up of halogen-magnesium exchange
reactions, one has to consider that a much higher gas volume
will be evolving when carrying out these transformations in
the absence of LiCl. Also, applying s-BuMgCl/LiCl Turbo-
Grignard solutions in halogen-magnesium exchange reac-
tions gives less gas evolution than transformations with
i-PrMgCl/LiCl TurboGrignard mixtures. Thus, regarding
process safety, the use of s-BuMgCl/LiCl reagents may be
better suited, at least for rather slow exchange reactions.
(complexometric), [Cl-] (argentometric), and [OH-] (acidi-
metric) were obtained via titrations, those of [Li+] via atomic
absorption spectroscopy (AAS). GC/MS measurements were
performed on a THERMO ELECTRON FINNIGAN Trace
GC or a Trace-DSQ GC with the following parameters:
column: DB1 (60 m × 0.25 mm; film: 0.25 µm); method:
oven 90 °C for 10 min; heating rate 20 K/min until 280 min;
injector/detector temperature 280 °C; split: He/FID; flow
rate 1.5 mL/min (He).
Quantitative GC measurements were performed on a
FOCUS GC from FINNIGAN with the following param-
eters: column: DB1 (60 m × 0.25 mm; film: 0.25 µm);
method: oven 90 °C for 10 min; heating rate 20 K/min until
280 min; injector/detector temperature 280 °C; split: He/
FID; flow rate 1.2 mL/min (He). Calibrations were performed
with exact amounts of bromo- and iodobenzene as external
standards. All measurements were repeated four times, and
the average values of the integrals were taken to calculate
the mass percents.
Infrared spectra during the reactions of i-PrMgCl, s-
BuMgCl, i-PrMgCl/LiCl, and s-BuMgCl/LiCl, with i-PrBr
or s-BuBr, respectively, were recorded inline every 2 min
on a REACTIR 1000 from ASI APPLIED SYSTEMS from
3000 to 700 cm-1 with a diamond IR dipper. The spectra
are referenced against an Ar background spectrum. Charac-
teristic modes of i-PrBr (1227 cm-1) and s-BuBr (1208 cm-1)
were identified from waterfall diagrams obtained during the
reactions. The reaction profiles (Figure 2) of the modes were
obtained from the “quick profile function” of the software,10
generating an absorption versus time plot for each mode.
The kinetics of the reactions were evaluated at constant
reaction conditions after 150 min. The calculated values log-
(I/I0) concentration are relative to the intensity I0 after 150
min (see Supporting Information).
Bromo-Magnesium Exchanges of i-PrMgCl/LiCl and
s-BuMgCl/LiCl Mixtures with Bromobenzene. To 50.0
mmol of TurboGrignard solutions (3-6) from Table 1 in
100-mL flasks was added 45.5 mmol of bromobenzene at
25 °C. After certain times, reaction aliquots were taken,
derivatized with iodine, and subjected to quantitative GC.
The conversion at a certain time was calculated as:
Conclusion
The yields obtained in halogen-magnesium exchange
reactions are dependent on the presence and amount of
lithium chloride dissolved in the Grignard solutions and also
on the organic substituents at the magnesium center of the
Grignard. Changing the reagents from i-PrMgCl/LiCl to
s-BuMgCl/LiCl gives obvious changes in conversions.
Although slower at the beginning of exchange reactions, the
rate of conversion using s-BuMgCl/LiCl mixtures for the
transformation drops less as the reaction progresses than if
carrying out the exchange with i-PrMgCl/LiCl solutions.
Hence, with s-BuMgCl/LiCl TurboGrignard solutions, slightly
better conversions are obtained.
As a competitive reaction a formal HBr elimination,
accompanied by evolution of gaseous products, takes place:
the Grignard reagent reacts with the respective alkyl halide,
which is formed in equivalent stoichiometric amounts relative
to the new Grignard product, giving magnesium salts,
alkanes, and alkenes. The rate of this competitive formal HBr
elimination, responsible for low conversions in exchange
reactions, is strongly influenced by dissolved LiCl. In
presence of LiCl, this elimination is slower, causing less of
the Grignard reagent to be consumed in the side reaction,
therefore giving higher conversions. Additionally, the com-
petitive HBr elimination is slower for s-BuMgCl/LiCl
solutions than for i-PrMgCl/LiCl TurboGrignard mixtures.
Therefore, the application of s-BuMgCl/LiCl in halogen-
magnesium exchange reactions results in higher conversions
and also in less gaseous side products, facts that should be
considered for scale-up of halogen-magnesium exchange
reactions.
1
conversion ) 1 -
mass % (PhI)/M(PhI)
+ 1
mass % (PhBr)/M(PhBr)
The detailed time-dependent conversions are given in the
Supporting Information.
Experimental Section
Kinetics of the Formal HBr Elimination Reaction. In
an 0.8-L double-jacketed reactor, equipped with a temper-
ature-control device (internal and external), dosing pump,
gas meter, condenser, and the inline IR dipper, each
respective Grignard solution was added and heated to 45 °C.
After a constant reaction temperature of 45 °C was reached,
the respective alkyl bromide was added continuously over a
period of 120 min, and the reaction temperature was
maintained at 45 °C. After the complete addition, the solution
All manipulations were performed in an atmosphere of
dry argon using Schlenk techniques. Solvents and LiCl were
dried prior to use. All other reagents were used as purchased.
The Grignard reagents i-PrMgCl and s-BuMgCl were
prepared by standard oxidative addition of the respective
chlorides to Mg turnings in THF. TurboGrignard reagents,
i-PrMgCl/LiCl and s-BuMgCl/LiCl, differing in the amount
of dissolved LiCl were prepared by dilution of the previously
prepared Grignard solutions with THF and addition of the
appropriate amount of LiCl. The concentrations of [Mg2+]
(10) ReactIR, version 2.1; ASI Applied Systems, 1996.
Vol. 10, No. 4, 2006 / Organic Process Research & Development
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737

was stirred at a temperature of 45 °C for the period, as
indicated in Table 2.
i-PrMgCl (1) + i-PrBr. To 270.4 g (538 mmol) of
i-PrMgCl (20 wt % in THF) was added 66.2 g (538 mmol)
of i-PrBr.
i-PrMgCl/LiCl (4) + i-PrBr. To 266.7 g (360 mmol) of
i-PrMgCl/LiCl (14 wt % in THF, with LiCl:i-PrMgCl )
1.02) was added 44.3 g (360 mmol) of i-PrBr.
s-BuMgCl (2) + s-BuBr. To 285.6 g (614 mmol) of
s-BuMgCl (25 wt % in THF) was added 84.1 g (614 mmol)
of s-BuBr.
s-BuMgCl/LiCl (6) + s-BuBr. To 288.8 g (361 mmol)
of s-BuMgCl (15 wt % in THF, with LiCl:s-BuMgCl ) 0.96)
was added 49.5 g (361 mmol) of s-BuBr.
1-4: Waterfall diagrams of the reactions of i-PrMgCl (1)
and i-PrMgCl/LiCl (4) with i-PrBr and of s-BuMgCl (2) and
s-BuCl/LiCl (6) with s-BuBr, respectively. Table 3: Time-
dependent intensities of the characteristic IR modes of i-PrBr
and of s-BuBr and lg(I/I0) from Figures 1-4. Table 4: Time-
dependent values for the gas flow measurements during the
reactions of i-PrMgCl (1) and i-PrMgCl/LiCl (4) with i-PrBr
and of s-BuMgCl (2) and s-BuCl/LiCl (6) with s-BuBr,
respectively. Figure 5: Intensity versus time plot of the IR
modes of i-PrBr and s-BuBr in the reactions with Turbo-
Grignard reagents according to Scheme 5 in the paper,
illustrating the loss of intensity of the IR modes and the
procedure of data evaluation to determine reaction rates. This
material is available free of charge via the Internet at http://
pubs.acs.org.
Supporting Information Available
Table 1: Analytical results of the Grignard and Turbo-
Grignard reagents. Table 2: Time-dependent conversions in
the reactions of i-PrMgCl/LiCl (3, 4) and s-BuMgCl/LiCl
(5, 6) in the benchmark reaction with bromobenzene. Figures
Received for review January 16, 2006.
OP0600153
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