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Supporting Information

© Wiley-VCH 2007

69451 Weinheim, Germany

-S1- Relative Rates of Bromine-Magnesium Exchange Reactions in Substituted Bromobenzenes Lei Shi, Yuanyuan Chu, Paul Knochel, Herbert Mayr* Butenandtstrasse 5-13 (Haus F), 81377 München, Germany

Fax: (+49) 89-2180-77717

E-mail: Herbert.Mayr@cup.uni-muenchen.de

General information:

All reactions involving the use of Grignard reagents were carried out under nitrogen atmosphere in dried glassware using Schlenk techniques. The materials were purchased from commercial sources and used without further purification. The solvent THF was dried and freshly distilled over sodium/benzophenone before use. Isopropylmagnesium chloride/lithium chloride 1:1 (i-PrMgClLiCl) in THF was from Chemetall GmbH.

Gas chromatographic equipment:

GC analyses were performed on a GC-8130 gas chromatograph (Fisons) equipped with a standard injector, a FI detector, and an Optima-1710 capillary column (0.25 µm × 25m × 0.25mm, Macherey-Nagel). The carrier gas was nitrogen; peak areas were obtained with the integration tool of the Chrom-Card software. Determination of relative response factors for the gas chromatographic analysis:

The relative response factors (f)

[S1] are now calculated as 11

11[1] [ ]

[] [1]RR RR

IS ISAR AISffAIS AR

11

11[1] [ ]

[] [2]PP PP

IS ISAP AISffAIS AP

A R1 , A P1 , A IS are areas of R1 (reactant 1), P1 (product 1) and internal standard (n-C 14 H 30
[R1], [P1], [IS] are the corresponding concentrations. Typical procedure: A mixture of R1, R2, P1, P2, and internal standard (n-C 14 H 30
) was analyzed by GC to give area ratios. Each mixture was run at least three times. For each compound in one run we

can get appropriate relative response factor, and the reported values of relative response factors (see

Table 1) are an average obtained from all runs.

[S1] D. J. David, Gas Chromatographic Detectors, Wiley, New York, 1974; Chapter 3. -S2- Table 1. Relative response factor of reactants and products versus internal standard (n-C 14 H 30
f Br CN CN Br

BrNCCN

I CN CN I INC Average value 0.443 0.431 0.447 0.469 0.408 0.424 0.403 f Br CF 3 CF 3 Br BrF 3 CCF 3 I CF 3 Br Cl Cl Br Average value 0.488 0.465 0.476 0.518 0.480 0.428 0.411 f

BrClCl

I Cl Cl I ICl Br F F Br Average value 0.418 0.439 0.413 0.401 0.423 0.441 0.443 f BrF F IF Br I Br Br BrBr Average value 0.402 0.487 0.373 0.367 0.376 0.402 0.406 f Br CO 2 tBu I CO 2 tBu

Average value 0.482 0.654 0.630

Determination of the concentration of i-PrMgClLiCl solution Method 1) A 10 mL round-bottom flask equipped with a magnetic stirring bar and a septum was heated with a heat gun under reduced pressure and cooled to room temperature under a nitrogen atmosphere. The dry flask was charged with accurately weighed I 2 (ca. 1 mmol), fitted with a rubber septum, and flushed with nitrogen. After the iodine was completely dissolved in THF (5 mL), the resulting brown solution was cooled to 0 o C in an ice bath and stirred. The i-PrMgClLiCl was added dropwise via a 1.00 mL syringe until the brown color disappeared. -S3- Table 2. Determination of the concentration of i-PrMgClLiCl with I 2 m iodine (mg) 256.7 259.4 248.6 262.7 M iodine (g/mol) 253.81 n iodine (mmol) 1.0114 1.0220 0.9795 1.0350 V i-PrMgClLiCl (mL)

0.852 0.878 0.834 0.885

c i-PrMgClLiCl (mol/L) 1.1871 1.1640 1.1744 1.1695 Av c i-PrMgClLiCl (mol/L)1.17 Method 2) A 25mL flame-dried, round-bottom flask with a magnetic stirring bar was rapidly charged with a sample of accurately weighed menthol and 1,10-phenanthroline (4 mg) before being capped with a rubber septum and flushed with dry nitrogen via a syringe needle. Freshly distilled (from Na, benzophenone) dry THF (8 mL) was introduced and the resulting solution was stirred at room temperature under nitrogen atmosphere. Dropwise addition of Grignard solution to be assayed was carried out by syringe technique until a distinct violet or burgundy color persisted longer than one minute. Table 3. Determination of the concentration of i-PrMgClLiCl with menthol m menthol (mg) 177.4 142.4 184.1 M menthol (g/mol) 156.27 n menthol (mmol) 1.1352 0.9112 1.1781 V i-PrMgClLiCl (mL) 0.980 0.778 1.005 c i-PrMgClLiCl (mol/L) 1.1584 1.1713 1.1722 Av c i-PrMgClLiCl (mol/L) 1.17

Determination of the Relative Exchange Rates ț

For a reaction, where reactant R1 gives product P1 and reactant R2 gives product P2, e.g. CN Br CN Br R1R2

1) i-PrMgCl

LiCl 2) I 2 CN P1I CN I P2

the relative reactivity of R1 and R2 is expressed by the competition constant ț which is defined by eq.

(1) 0

0log([1]/[1])1log([ 2] /[ 2])t

tRR RR (1) Three different methods have been employed to determine ț -S4-Method 1: ț1

Substitution of [R1]

0 and [R2] 0 in eq.(1) by the expressions in eq.(2) and (3) (mass balance) yields eq.(4)

0[1] [1] [1]ttRRP (2)

0[2] [2] [2]ttRRP (3)

log(1+[ 1] /[ 1]) log(1+[ 2] /[ 2])tt ttPR PR (4) Competition constants calculated according to eq. (4) from the chromatographically determined ratios [P1] t /[R1] t and [P2] t /[R2] t are represented as ț1 in the following Tables.

Method 2: ț2

In some cases, the products obtained from R1 and R2 are identical, e.g. in the case of trapping

regioisomeric Grignard reagents with methanol. The competition constant (represented as ț2) is then

calculated by determining [R1] t and [R2] t gas chromatographically (comparison of the areas with that of the internal standard n-C 14 H 30
) and substituting directly into eq. (1). Particularly in the case of

a low conversion, the ț2 values are not very reliable and will only be used, if method 1 (ț1) is not

applicable.

Method 3: ț3

With

0[1] [1] [1]ttRRPand 0[2] [2] [2]ttRRP eq.(1) is converted into eq.(5)

00

00[1] [2]3 log( )/log( )[1][1] [2][2]

tt RR RP RP (5) [P1] t and [P2] t are obtained gas chromatographically by comparison with the internal standard n-C 14 H 30
-S5- Typical Procedure (Iodine Quench): (0.25M : 0.25M) A dry and nitrogen flushed 25-mL flask, equipped with a magnetic stirrer, was charged with

3-bromobenzonitrile R1 (1.17 mmol, 214 mg), 4-bromobenzonitrile R2 (1.17 mmol, 214 mg) and

internal standard (n-C 14 H 30
) in THF (3.70 mL). The reaction mixture was cooled to 0 o C. i-PrMgCl LiCl (1.17 mmol, 1.00 mL solution in THF) was added in one portion. After certain times (for example 20 min), about 0.2 mL of the mixture was taken out with a syringe and sprayed on some crystals of iodine under nitrogen protection. The reaction mixture was washed with aqueous Na 2 S 2 O 3 solution (50 mL, 0.15 M). The aqueous phase was extracted with diethylether (about 25 ~ 30 mL).

The etheral solutions were dried over Na

2 SO 4 and analyzed by GC. CN Br CN Br R1R2

1) i-PrMgCl

LiCl 2) I 2 CN P1I CN I P2 -S6-Combination of 0.25M 3-bromobenzonitrile (R1), 0.25M 4-bromobenzonitrile (R2), 0.25M internal standard (n-C 14 Hquotesdbs_dbs19.pdfusesText_25

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