Catalyzed Reactions of Enol Ethers with SN1 Active Groups: A Novel Method for the Preparation of α-Alkylated Ketones

Article abstract of DOI:10.1002/adsc.200303059

The performance of tert-alkylations, alkoxyalkylations, and aldehyde enolate allylations proceeding with low catalyst loading (0.1 mol % - 5 mol %) is described. The reactions are complete within short times and can even be performed without solvent and under ambient conditions. The mechanism of the reaction was investigated by deuterium labeling and cross-over studies.

Full text of DOI:10.1002/adsc.200303059

FULL PAPERS
Catalyzed Reactions of Enol Ethers with SN1 Active Groups:
A Novel Method for the Preparation of a-Alkylated Ketones
Andreas Gans‰uer,* Doris Fielenbach, Christoph Stock, Daniel Geich-Gimbel
¬
Kekule-Institut f¸r Organische Chemie und Biochemie, Rheinische Friedrich-Wilhelms-Universit‰t, Gerhard Domagk Str.1,
53121 Bonn, Germany
Fax: ( ‡ 49)-228-73-4760, e-mail: andreas@gansaeuer.de
Received: March 31, 2003; Accepted: May 21, 2002
Abstract: The performance of tert-alkylations, alkoxy- reaction was investigated by deuterium labeling and
alkylations, and aldehyde enolate allylations proceed- cross-over studies.
ing with low catalyst loading (0.1 mol % 5 mol %) is
described. The reactions are complete within short
times and can even be performed without solvent and Keywords: alkylation; boron; catalysis; copper; eno-
under ambient conditions. The mechanism of the lates; Lewis acids; ketones
Introduction
Results and Discussion
The alkylation of ketone enolates constitutes one of the We reasoned that useful precursors for the planned
central reactions for the formation of carbon-carbon transformation would be p-methoxybenzyl (PMB) enol
bonds in chemistry. To achieve this transformation ethers, adamantyl enol ethers, enol ethers of acetals, and
enolates are usually generated under strongly basic allyl enol ethers in reactions with protic acids or strong
conditions and are further reacted with an alkylating Lewis acids as potential catalysts. All compounds would,
reagent.[1] More recently, these transformations have after acid-induced cleavage of the oxygen-carbon bond,
been achieved in the presence of catalysts.[2] In spite of lead to enolates and stabilized cations.[8]
intense efforts a drawback of these procedures is that
high regio- and stereoselectivity of enolate generation is
not always easy to achieve, especially in the case of Initial Optimization of the Reaction Conditions
ketones with sterically similar substituents. Also, the
atom economy of the overall process is usually low.[3]
A
The results of our exploratory studies with substrates 1,
different concept developed by Reetz allows for the 2, and 3 are summarized in Table 1.
reaction of SN1 active electrophiles with silyl enol ethers
When 1, that was used as 78:22 mixture of (Z) and (E)
in the presence of stoichiometric amounts of Lewis isomers, was exposed to BF3 ¥ Et2O, Cu(OTf)2,[9] or
acids.[4] However, a general reaction catalytically gen- B(C6F5)3,[10] the desired product 4 could be obtained in
erating an alkylating reagent for a suitable enolate or good yield (75 84%) with low catalyst loading (entries
enol derivative has remained elusive.
1 3). The reactions were run at high concentration
We decided to address exactly these issues by employ- (1 M).
ing enol ethers as enolate equivalents that can be
In the case of starting material 2 the same Lewis acids
cleaved in an SN1 manner as precursors for this type of also lead to satisfactory results in CH2Cl2 at 1 M to 3 M
transformation. The method is based on reports that concentration and room temperature. It is interesting to
many simple ethers can be cleaved in the presence of note that for both B(C6F5)3 and Cu(OTf)2 a reduction in
Lewis acids.[5] A less general concept has been realized catalysts loading to 0.1 and 0.25 mol % (entries 4 and 5)
in Ferrier-type rearrangements.[6] To the best of our
knowledge, a catalytic or enantioselective variation of
these systems has, as yet, not been described. The
general idea of the reaction is depicted in Figure 1.
Efficient and well established methods for the syn-
thesis of enol ethers are olefinations of esters and
isomerizations of allyl ethers either by transition metal
complexes or base.[7] The necessary starting materials
are thus readily available.
Figure 1. Concept for the Lewis acid-catalyzed alkylation of
enolates.
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DOI: 10.1002/adsc.200303059
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Table 1. Lewis acid catalyzed reaction of enol ethers in CH2Cl2.
Entry
1
Substrate
Product
Catalyst
Yield [%]
84[a]
B(C6F5)3, 1 mol %
2
3
4
1
1
4
4
Cu(OTf)2, 5 mol %
BF3 ¥ Et2O, 5 mol %
B(C6F5)3, 0.1 mol %
77[a]
75[a]
84[b]
5
6
7
8
2
2
2
5
5
5
Cu(OTf)2, 0.25 mol %
BF3 ¥ Et2O, 5 mol %
Bu2BOTf, 1 mol %
B(C6F5)3, 0.1 mol %
87[b]
86[c]
85
54: 40[d]
(6/PhCOEt)
9
10
11
3
3
3
6
6
6
Cu(OTf)2, 0.25 mol %
BF3 ¥ Et2O, 5 mol %
Bu2BOTf, 1 mol %
81[e]
73[e]
83[f]
[a]
1: Z/E ˆ 78: 22; 1 M.
[b]
[c]
[d]
[e]
[f]
2: Z/E ˆ 80: 20; 3 M.
2: Z/E ˆ 80: 20; 1 M.
By GC-analysis of the crude mixture.
3: Z/E ˆ 84: 16; 2 M.
3: Z/E ˆ 84: 16; 1 M.
led to a small but noticeable increase in the yield (84%
and 87%) of 5 compared to reactions performed with 1
or 5 mol % catalyst (79% and 68% yield). It should be
noted that Bu2BOTf was a suitable catalyst for the
rearrangement reaction, also. An 85% yield of 5 could
be obtained with a low catalyst loading of 1 mol %
(entry 7).
A different outcome was observed with substrate 3. In
this case Cu(OTf)2 (83%, 1 mol %, 5 min, entry 9), BF3 ¥
Et2O (73%, 5 mol %, entry 10), and Bu2BOTf (83%,
1 mol %, entry 11) led to satisfactory results in CH2Cl2
(1 M). With B(C6F5)3 a 54:40 mixture of 6 and propio-
phenone was obtained (entry 8). A possible reason for
this failure of the reaction could be deactivation of the
sterically demanding catalyst by complexation of the
ether group present in 6.
Figure 2. Ionic pathway for the synthesis of [1,3]-Claisen
products.
We also tested some protic acids (TfOH, aqueous
HCl, HOAc, 10-CSA, BOC-proline, and TFA) as
catalysts in reactions with 3. Of these reagents, only
TfOH (ca. 10 mol %) led to appreciable amounts of tion would deliver the product resulting from attack at
desired product (72% 6 and 15% propiophenone) as the least hindered site of the cation. Formally, this would
judged by GC analysis of the reaction mixture.
result in the product of a [1,3]-rearrangement.[11,12] As
In the case of the readily accessible allyl enol ethers, demonstrated in Table 2 this regioselectivity was indeed
care has to be taken in distinguishing the desired enolate exclusively observed and only the [1,3]-product was
allylation from a concerted [3,3]-Claisen rearrange- obtained.
ment. We chose substrate 7 shown in Figure 2 to address
this possible mechanistic ambiguity.
As in the case of 3 it turned out that the use of both
BF3 ¥ Et2O (entry 1) and Cu(OTf)2 (entry 2) resulted in
Because of the formation of an unsymmetrically efficient catalytic turn-over and 72% and 60% isolated
substituted allyl cation it was assumed that the alkyla- yields of 8. With BF3 ¥ Et2O lowering the reaction
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A Novel Method for the Preparation of a-Alkylated Ketones
temperature to À 788C resulted in a decreased yield of
FULL PAPERS
We also investigated the possibility of performing the
55% (entry 1, see footnote). B(C6F5)3 performed reaction in the absence of solvent. The reaction of 3
distinctly inferior to give 8 in only 30% yield. However, proceeded smoothly to give 5 in 72% isolated yield in
analysis of the crude reaction mixture revealed com- the presence of 0.1 mol % Cu(OTf)2. The reaction of 15,
plete consumption of the starting material. This result possessing an additional methoxy group also proceeded
could be explained by an elimination reaction of a eventlessly with Cu(OTf)2 and BF3 ¥ Et2O (entry 7 and
proton from the allyl cation by the enolate. We were footnotes) indicating that both Lewis acids are not
unable to isolate the diene, however. Because of the high prone to product inhibition by ethers.
steric bulk of B(C6F5)3 this side reaction should be more
In the case of tertiary cations that are not stabilized by
relevant than for the less hindered reagents BF3 ¥ Et2O conjugation it is important to note the difference
and Cu(OTf)2. This point will be discussed more between the 1-adamantyl and tert-butyl enol ethers.
thoroughly, later (see Table 4).
Because the 1-adamantyl cation is relatively stable
towards elimination, the strained bridgehead olefin
adamantene[14] would be formed, excellent results can
be obtained. In contrast, from the tert-butyl cation a
proton can be readily eliminated to yield 2-methylpro-
pene by the strongly basic enolate. It therefore came as
Scope and Limitation of the Lewis Acid-Catalyzed
Rearrangement
With a set of reliable reaction conditions in hand we no surprise that the attempted tert-alkylation using 19
turned our attention to the scope and limitation of the gave a mixture of the desired product 20 in 32% yield
reaction next.
and propiophenone in 40% yield (entry 9). So far it has
The results with some enol ethers leading to stabilized been impossible to generate secondary cations under
saturated cations are summarized in Table 3.
It turned out that for all cases with the PMB enol
our reaction conditions.
The Lewis acid-catalyzed rearrangement of allyl enol
ethers examined the yields were reasonable to high and ethers also proved to be fairly general as summarized in
that B(C6F5)3 was slightly superior to Cu(OTf)2. Reac- Table 4.
tion times were extremely short (<5 min). Lowering of
As shown in entries 1 and 2 enol ethers 21 and 23 could
the reaction temperature to À 308C still resulted in a be rearranged in reasonable to high yields with low
very fast reaction (<5 min) and essentially the same catalyst loadings. A proof for the non-concerted mech-
yield (entry 4b). Entry 4 also demonstrates the specific anism of formation of 24 will be presented in the
usefulness of our enol ether method. 3-Nonanone, the following paragraph. It should be noted that catalysis of
starting material for enolate alkylation under basic the [3,3]-rearrangement of 23 by Yamamoto× s excellent
conditions, cannot be deprotonated regioselectively in bulky aluminum reagents gave inferior results in his
the presence of bases.[13] Performing the reaction under hands concerning both yield and catalyst loading
an atmosphere of air in undistilled and undried solvent (10 mol %, 45% yield after 13 h).[12c]
was possible (entries 2 and 3) with just a slight reduction
in yield.
Increasing the steric bulk compared to our initial
substrate 7 by introduction of a tert-butyl group
The importance of the stabilization of the cation was (substrate 25, entry 3) resulted in a slight reduction in
manifested by the observation that exposure of the yield (63%).When the double bond carried an additional
corresponding benzyl ethers to the Lewis acids did not terminal methyl substituent (entries 4 and 5) the yields
give any of the desired products. Instead, intractable again deteriorated slightly. The reaction of the propio-
mixtures of products containing varying amounts of the phenone-derived enol ether 31 is interesting with regard
ketones resulting from protic cleavage were obtained.
to the mechanism of the reaction. The reduction in the
Table 2. Lewis acid catalyzed reaction of allyl enol ethers in CH2Cl2.
Entry
1
Substrate
Product
Catalyst
Yield [%]
72[a]
BF3 ¥ Et2O, 7 mol %
2
3
7
7
8
8
Cu(OTf)2, 5 mol %
B(C6F5)3, 1 mol %
60[b]
30[c]
[a]
0.1 M; À 788C 55%.
[b]
[c]
1 M; À 558C.
1 M.
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Table 3. Lewis acid-catalyzed reaction of allyl vinyl ethers in CH2Cl2 (1 M).
Entry
1
Substrate
Product
Catalyst
Yield [%]
78[a]
B(C6F5)3, 1 mol %
2
3
9
10
B(C6F5)3, 1 mol % in air
B(C6F5)3, 1 mol % in air
67[b, c]
80[d]
4
5
6
B(C6F5)3, 1 mol %
B(C6F5)3, 1 mol %
71[b, c]
71[e]
Cu(OTf)2, 0.1 mol %, neat
72
7
8
9
Cu(OTf)2, 1 mol %
B(C6F5)3, 1 mol %, 3 M
BF3 ¥ Et2O, 5 mol %
71[f]
69[g]
32[h]
[a]
1 mol % Cu(OTf)2 64%.
[b]
[c]
[d]
[e]
[e]
[f]
9: Z/E ˆ 88: 12; À 308C 66%.
1 mol % Cu(OTf)2 70%.
1: Z/E ˆ 78: 22, 5 mol % BF3 ¥ Et2O 65%.
1 mol % Cu(OTf)2 71%.
13: Z/E ˆ 80: 20.
15: Z/E ˆ 80: 20.
[g]
[h]
17: Z/E ˆ 83: 17; 1 mol % Cu(OTf)2 70%.
19: Z/E ˆ 80: 20; 1 M, À 788C to rt.
basicity of the enolate through conjugation with the of the increased stability of the methallyl cation. For a
aromatic ring results in good to reasonable yields of 32 proof of the non-concerted nature of the reaction see the
for all three catalysts investigated. Only minor amounts following mechanistic discussion.
of propiophenone were obtained. This observation
lends support to our hypothesis of base-induced elim- introduced by Grieco that uses the highly polar 5 M
inations as undesired side reactions. solutions of LiClO4 in Et2O to induce [1,3]-rearrange-
Our method is therefore superior to the method
The reaction could also be successfully performed ments.[15] With this reagent only tri- or tetrasubstituted
with allyl and methallyl enol ethers as described in allyl cations could be generated. Therefore, the Lewis
entries 7 and 8. In the case of the allyl enol ether a 54% acidity of the LiClO4 system must be considered as
yield of 34 could be obtained at À 408C. At lower substantially lower than our systems. Moreover, it has
temperature no rearrangement was observed. Increas- been reported that the LiClO4/diethyl ether reagent is
ing the temperature led to substantial reductions of the potentially hazardous.[16]
isolated yield, e.g., 26% at room temperature. The
corresponding methallyl enol ether 35 could already be
cleaved at À 658C to give the desired product 36 in 75% Mechanistic Considerations
yield. At À 158C a 62% yield of 36 was obtained.
The ease of cleavage of 35 and increased yields of 36, In our initial mechanistic studies we were concerned
especially at low temperatures, constitutes a reflection with a proof of the non-concerted pathway for the
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A Novel Method for the Preparation of a-Alkylated Ketones
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Table 4. Lewis acid-catalyzed reaction of allyl vinyl ethers in CH2Cl2 (1 M).
Entry
1
Substrate
Product
Catalyst
Yield [%]
84[a]
BF3 ¥ Et2O, 5 mol %, 0.01 M
2
3
B(C6F5)3, 0.25 mol %
82[b]
63
BF3 ¥ Et2O, 5 mol %, 0.1 M
4
5
6
Cu(OTf)2, 5 mol %, À 158C
BF3 ¥ Et2O, 5 mol %, 0.1 M
Cu(OTf)2, 5 mol %, À 408C
59[c]
59[d]
77[e]
7
8
Cu(OTf)2, 5 mol %, À 408C
Cu(OTf)2, 5 mol %, À 658C
54
75
[a]
1 mol % Cu(OTf)2 64%; 1 mol % B(C6F5)3, 0.1 M, 72%.
5 mol % Cu(OTf)2, 67%.
[b]
[c]
[d]
[e]
1 mol % Cu(OTf)2, 0.5 M, À 158C, 59%, drˆ 69: 31.
5 mol % Cu(OTf)2 40%, drˆ 64: 36.
31: Z/E ˆ 91: 9, 5 mol % BF3 ¥ Et2O, 0.1 M, 83%, 1 mol % B(C6F5)3, 0.1 M, 54%.
symmetrical allyl cations (Table 4, entries 2, 7, and 8). the former case a reagent-controlled course of the
As shown in Figure 3 it was demonstrated by deuterium alkylation should become possible by ligand variation of
labeling studies in two of the three cases that attack of the catalyst. In the latter case a chain mechanism would
the enolate on the allyl cation occurred without be operating with the usual consequence of a substrate-
regioselectivity. This would not have been the case in a controlled transformation.
concerted [3,3]-Claisen rearrangement. We did not
This course of events seems unlikely when considering
investigate the allyl enol ether because of the volatility the results of Tables 1 4. Once a cation is generated the
of deuterated allyl alcohol necessary for the synthesis of further progress of the transformation should be inde-
labeled 33.
pendent of the potential initiator and should also be
A question of general importance for the mechanism general within a series of similar substrates. This was not
of the reaction concerns the problem of attack of the observed, however. Especially in the case of the
cation on either the generated enolate or on a second B(C6F5)3-catalyzed enolate allylations the less basic
enol ether. The latter situation is depicted in Figure 4. In enolates (Table 4, entry 6 and footnotes) give reason-
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Figure 3. Deuterium labeling studies as proof of a non-
concerted mechanism.
Figure 5. Cross-over study as evidence for long-lived ionic
intermediates.
Experimental Section
Typical Experimental Procedures for the Syntheses of
Enol Ethers
Figure 4. Addition to enol ethers via a chain mechanism as
alternative to enolate alkylation.
General Procedure A Olefination of Esters[18]: Under an
argon atmosphere a 1.0 M solution of TiCl4 (4 equiv.) in CH2Cl2
was added at 08C to dry THF. After the resulting yellow
suspension was warmed to room temperature TMEDA (8
equiv.) was added and the brown solution was stirred for
10 min. Zinc (9 equiv.) was added and after the color of the
suspension had changed from brown to dark greenish blue (ca.
30 min) the 1,1-dibromoalkanes (2.2 equiv.) and the ester (1
equiv.) were added simultaneously and the mixture was stirred
overnight. After ice-cooled hydrolysis by a saturated K2CO3
solution the complete reaction mixture was filtered through a
short column of alumina (Merck, aluminum oxide 90 stand-
ardized) using diethyl ether as eluent. The solvent was
removed under reduced pressure and the residue purified by
column chromatography on alumina to yield the correspond-
ing enol ether.
General Procedure B Mercury-Catalyzed Vinylation of
Allylic Alcohols[19]: Mercury(II) acetate (0.2 equiv) was dried
prior to the reaction by gentle heating under vacuum and
dissolved under an argon atmosphere in freshly distilled ethyl
vinyl ether. To this solution the allylic alcohol (1 equiv) was
added and the mixture was stirred for 5 days at ambient
temperature. The resulting solution was washed 3 times with
H2O and dried over MgSO4. The solvent was removed under
reduced pressure and the crude product was isolated by
filtration through a short column of alumina (Merck, alumi-
num oxide 90, standardized) using pentane as a solvent to yield
the corresponding allyl vinyl ether.
able results, whereas the other more basic enolates
essentially result in the failure of the reaction. Besides,
the presence of the ketones arising from protonation of
the enol ether moiety cannot be readily explained by the
chain mechanism. Thus, our reactions did in deed seem
to proceed via the reaction of enolates with cations.
Another question of mechanistic interest is concerned
with the persistence of the ions generated under the
reaction conditions. This problem can be addressed
experimentally by cross-over studies. The result of a
typical experiment is summarized in Figure 5.
All possible products were observed in the GC
analysis of the crude reaction mixture in substantial
amounts. It should be noted that the numbers refer to
the intensities of the corresponding GC signals and do
not represent isolated yields. It was impossible to
separate the four products.
Thus, the ions generated under our conditions were
able to diffuse freely before recombination and should
not be considered as contact ion pairs according to the
Winstein nomenclature.[17]
Conclusion
In conclusion, we have devised an efficient catalytic
system for the alkylation and allylation of enolates
based on the Lewis acid-catalyzed cleavage of enol
ethers. We anticipate that the mild reaction conditions,
insensitivity to ambient exposure, low catalyst loading,
and high to excellent turnover frequencies of our system
meet the demands for efficient synthesis and will thus
lead to considerable use in organic synthesis.
Typical Experimental Procedures for the
Rearrangement Reactions
General Procedure C: The solid catalyst B(C6F5)3 or Cu(OTf)2
was dried by gentle heating (1 min) under vacuum and was
dissolved under an argon atmosphere in CH2Cl2 at the
indicated temperature. After addition of the enol ether stirring
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A Novel Method for the Preparation of a-Alkylated Ketones
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(1-Methoxymethoxypropenyl)-benzene (3)[20]
was continued for the declared time. The conversion of the
starting material was monitored by TLC and GC analysis.
After quenching by addition of 3 drops of triethylamine the
solvent was removed and the residue purified immediately by
SiO2 chromatography to give the desired ketone.
General Procedure D: Under an argon atmosphere the enol
ether was dissolved in dichloromethane at the indicated
temperature. After the addition of the liquid catalyst BF3 ¥
OEt2 or n-Bu2BOTf (1.0 M in CH2Cl2) the solution was stirred
until complete conversion of the starting material was moni-
tored by TLC and GC analysis. The catalyst was quenched by
addition of 3 drops of NEt3. After removal of the solvent the
crude product was purified immediately by SiO2 chromatog-
raphy to yield the desired ketone.
According to the General Procedure A: TiCl4 (40 mL (1.0 M in
CH2Cl2), 40 mmol) in THF (150 mL), TMEDA (12 mL,
80 mmol), Zn (6.00 g, 90 mmol), after the change of color is
complete 1,1-dibromoethane (2.70 mL, 22 mmol), and benzoic
acid methoxymethyl ester (1.66 g, 10 mmol). The reaction
mixture was stirred overnight. Standard work-up followed by
column chromatography (Al2O3, PE) afforded 3 as a colorless
oil; yield: 1.10 g (6.2 mmol, 62%). Z/E ˆ 83:17; Rf (PE, Al2O3):
0.2. 1H NMR (400 MHz, C6D6): d ˆ 7.48 7.39** (m, 2H),
7.13 7.09** (m, 2H), 7.08 7.01** (m, 1H), 5.26 * (m, 1H), 5.24
(q, J ˆ 6.9 Hz, 1H), 4.80* (s, 2H), 4.70 (s, 2H), 3.24 (s, 3H), 3.21*
(s, 3H), 1.80 (d, J ˆ 6.8 Hz, 3H), 1.60 (d, J ˆ 7.2 Hz, 3H);
13C NMR (100 MHz, C6D6): d ˆ 153.4, 137.2, 136.1*, 128.5,
127.9, 126.5, 110.2, 101.3*, 95.9, 94.3*, 56.6, 55.6*, 13.0*, 11.4;
‡¥
HRMS (EI, 70 eV): calcd. for (M ): 178.0994; found: 178.0997;
IR (neat): n ˆ 2920, 1660, 1495, 1445, 1315, 1260, 1210, 1155,
1095, 1020 cmÀ1. * signals of the minor isomer ** signals of
minor and major isomer not separated.
1-Methoxy-4-(1-methylpropenyloxymethyl)-benzene
(1)
According to the General Procedure A: TiCl4 (20 mL (1.0 M in
CH2Cl2), 20 mmol) in THF (150 mL), TMEDA (6 mL,
40 mmol), Zn (3.00 g, 45 mmol), after the change of color is
complete 1,1-dibromoethane (1.35 mL, 11 mmol), and acetic
acid 4-methoxybenzylic ester (0.90 g, 5 mmol). The reaction
mixture was stirred over night. Standard work-up followed by
column chromatography (Al2O3, PE:Et2O, 95:5) afforded 1 as
a colorless oil; yield: 0.54 g (2.8 mmol, 60%); Z/E ˆ 78:22; Rf
(PE, Al2O3): 0.2; 1H NMR (300 MHz, C6D6): AA×XX× system
with signals at d ˆ 7.31 and 6.89 (4H)**, 4.67 (s, 2H), 4.65* (s,
2H), 4.62 (m, 1H), 3.42 (s, 3H)**, 1.92* (s, 3H), 1.84 (d, J ˆ
6.7 Hz, 3H), 1.79 (t, J ˆ 1.3 Hz, 3H), 1.66* (dd, J ˆ 6.8 Hz,
0.8 Hz, 3H). 13C-NMR (75 MHz, C6D6): d ˆ 159.7, 153.2*,
150.9, 131.0*, 130.3, 129.2*, 129.0, 114.0, 103.8, 91.4*, 69.4, 68.5,
54.7, 18.2, 16.1*, 12.0*, 10.5; HRMS (EI, 70 eV): calcd. for
4-(4-Methoxyphenyl)-3-methylbutan-2-one (4)[21]
Table 1: Entry 1: According to the General Procedure C:
B(C6F5)3 (5.8 mg, 10 mmol) in CH2Cl2 (1 mL) at room temper-
ature, 1 (195 mg, 1 mmol). After 5 min the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2O, 90:10) afforded 4 as
a colorless oil; yield: 165 mg (0.8 mmol, 84%).
Table 1: Entry 2: According to the General Procedure C:
Cu(OTf)2 (18.0 mg, 50 mmol) in CH2Cl2 (1 mL) at room
temperature, 1 (196 mg, 1 mmol). After 10 min the reaction
was quenched by addition of NEt3. Standard work-up followed
by column chromatography (SiO2, PE:Et2O ˆ 90:10) afforded
4 as a colorless oil; yield: 151 mg (0.9 mmol, 77%).
Table 1: Entry 3: According to the General Procedure D: 1
(187 mg, 0.9 mmol) in CH2Cl2 (1 mL) at room temperature,
BF3 ¥ OEt2 (1 drop, ꢀ 5 mol %). After 5 min the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2O, 90:10) afforded 4 as
a colorless oil; yield: 141 mg (0.8 mmol, 75%).
‡
(M ): 192.1150; found: 192.1151; IR (neat): n ˆ 2915, 1685,
1615, 1550, 1465, 1380, 1305, 1250, 1175, 1100, 1035, 820 cmÀ1.
*signals of the minor isomer, ** signals of minor and major
isomer not separated.
Table 3: Entry 3: According to the General Procedure C, but
in air: B(C6F5)3 (2.7 mg, 5 mmol) in non-dried CH2Cl2 (1 mL) at
room temperature, 1 (110 mg, 0.6 mmol). After 5 min the
reaction was quenched by addition of NEt3. Standard work-up
followed by column chromatography (SiO2, PE:Et2O, 90:10)
afforded 4 as a colorless oil; yield: 88 mg (0.4 mmol, 80%). Rf
(PE:Et2O, 90:10, SiO2): 0.3; 1H NMR (300 MHz, CDCl3):
AA×XX× system with signals at d ˆ 6.97 and 6.72 (4H), 3.70 (s,
3H), AB signal (dA ˆ 2.82, dB ˆ 2.41, JA,B ˆ 13.4 Hz, addition-
ally split by J ˆ 6.8 Hz/7.3 Hz, 2H), 2.68 (m, 1H), 1.98 (s, 3H),
0.97 (d, J ˆ 7.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): d ˆ 212.2,
158.0, 131.6, 129.7, 113.7, 55.1, 48.9, 38.0, 28.8, 16.1; HRMS (EI,
1-(1-Phenylpropenyloxy)-adamantane (2)
According to the General Procedure A: TiCl4 (40 mL (1.0 M in
CH2Cl2), 40 mmol) in THF (150 mL), TMEDA (12 mL,
80 mmol), Zn (6.00 g, 90 mmol), after the change of color is
complete 1,1-dibromoethane (2.7 mL, 22 mmol), and 1-ada-
mantyl benzoate (2.56 g, 10 mmol). The reaction mixture was
stirred overnight. Standard work-up followed by column
chromatography (Al2O3, PE) afforded 2 as a colorless oil;
yield: 2.5 g (9.3 mmol, 93%). Z/E ˆ 80:20; Rf (PE, Al2O3): 0.6;
1H NMR (400 MHz, C6D6): d ˆ 7.59 7.49** (m, 2H), 7.19
7.11** (m, 2H), 7.09 7.03** (m, 1H), 5.46* (q, J ˆ 7.3 Hz, 1H),
5.37 (q, J ˆ 6.8 Hz, 1H), 1.93 1.83** (m, 10H), 1.41* (mc, 2H),
1.34 (mc, 3H); 13C NMR (100 MHz, C6D6): d ˆ 151.9, 150.2*,
142.8, 139.9*, 129.0, 128.1*, 127.3, 126.4*, 113.9, 113.3*, 78.4,
76.8*, 44.0, 43.7*, 36.5, 36.4*, 31.3, 31.2*, 13.3, 13.0*; HRMS
‡
70 eV): calcd. for (M ): 192.1150; found: 192.1154; IR (neat):
n ˆ 2935, 2835, 1710, 1610, 1515, 1460, 1360, 1300, 1250, 1180,
1115, 1035, 815 cmÀ1.
‡¥
(EI, 70 eV): calcd. for (M ): 268.1827; found: 268.1822; IR
2-Adamantan-1-yl-1-phenyl-propan-1-one (5)[22]
(neat), n ˆ 2910, 2850, 1445, 1355, 1325, 1300, 1100, 1065, 780,
700 cmÀ1. * signals of the minor isomer; ** signals of minor and
major isomer not separated.
Table 1: Entry 4: According to the General Procedure C:
B(C6F5)3 (1.5 mg, 3 mmol) in CH2Cl2 (1 mL) at room temper-
Adv. Synth. Catal. 2003, 345, 1017 1030
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Andreas Gans‰uer et al.
FULL PAPERS
ature, 2 (804 mg, 3 mmol). After 20 h the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, CH:EE, 99:1) afforded 5 as a
colorless oil; yield: 680 mg (2.5 mmol, 84%).
Table 1: Entry 5: According to the General Procedure C:
Cu(OTf)2 (2.7 mg, 7.5 mmol) in CH2Cl2 (1 mL) at room
temperature, 2 (804 mg, 3 mmol). After 20 h the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, CH:EE, 99:1) afforded 5 as a
colorless oil; yield: 699 mg (2.6 mmol, 87%).
less oil; yield: 515 mg (2.9 mmol, 72%). Rf (PE:Et2O, 96:4,
SiO2): 0.1; 1H NMR (300 MHz, CDCl3): d ˆ 7.89 (dd, J ˆ
7.9 Hz, 1.6 Hz, 2H), 7.13 7.01 (m, 3H), 3.63 (dd, J ˆ 8.5 Hz,
7.2 Hz, 1H), 3.55 (dquintet, J ˆ 5.9 Hz, 6.8 Hz, 1H), 3.24 (dd,
J ˆ 8.2 Hz, 5.7 Hz, 1H), 3.01 (s, 3H), 1.06 (d, J ˆ 6.8 Hz, 3H);
13C NMR (75 MHz, CDCl3): d ˆ 201.7, 137.5, 132.6, 2 x 128.6,
‡¥
75.4, 58.7, 41.4, 14.7; HRMS (EI, 70 eV): calcd. for (M ):
178.0994; found: 178.0996; IR (neat): n ˆ 2975, 2880, 1680,
1595, 1580, 1450, 1385, 1220, 1110, 980, 945 cmÀ1.
Table 1: Entry 6: According to the General Procedure D: 2
(278 mg, 1.0 mmol) in CH2Cl2 (1 mL) at room temperature,
BF3 ¥ OEt2 (1 drop, ꢀ 5 mol %). After 4 h the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2O, 98:2) afforded 5 as a
colorless oil; yield: 240 mg (0.9 mmol, 86%).
3-Isopropenyloxy-1,5,5-trimethylcyclohexene (7)
According to the General Procedure A: TiCl4 (40 mL, 1.0 M in
CH2Cl2, 40 mmol) in THF (150 mL), TMEDA (12 mL,
80 mmol), Zn (6.00 g, 90 mmol), after the change of color is
complete dibromomethane (1.52 mL, 22 mmol), and acetic
acid 3,5,5-trimethylcyclohex-2-enyl ester (1.82 g, 10 mmol).
The reaction mixture was stirred overnight. Standard work-up
followed by column chromatography (Al2O3, PE) afforded 7 as
a colorless oil; yield: 970 mg (5.3 mmol, 54%). Rf (PE, Al2O3):
Table 1: Entry 7: According to the General Procedure D: 2
(1.23 g, 4.6 mmol) in CH2Cl2 (5 mL) at room temperature, n-
Bu2BOTf (0.05 mL, 1.0 M in CH2Cl2, 50 mmol). After 5 min the
reaction was quenched by addition of NEt3. Standard work-up
followed by column chromatography (SiO2, PE:Et2O, 98:2)
afforded 5 as a colorless oil; yield: 1.05 g (3.9 mmol, 85%). Rf
1
0.9; H NMR (400 MHz, CDCl3): d ˆ 5.42 (bs, 1H), 4.46 (bs,
1
(PE:Et2O, 98:2): 0.3. H NMR (300 MHz, CDCl3): d ˆ 7.97
1H), 3.80 (s, 1H), 3.77 (s, 1H), 1.78 (d, J ˆ 17.5 Hz, 1H), 1.70 (s,
3H), 1.67 (dd, J ˆ 13.2 Hz, 6.5 Hz, 1H), 1.58 (s, 3H), 1.60 1.54
(m, 1H), 1.31 (dd, J ˆ 12.5 Hz, 8.6 Hz, 1H), 0.89 (s, 3H), 0.82 (s,
3H); 13C NMR (100 MHz, CDCl3): d ˆ 158.4, 137.4, 119.8, 81.8,
71.3, 44.3, 40.8, 31.0, 30.8, 26.8, 23.8, 21.8; HRMS (EI, 70 eV):
7.80 (m, 2H), 7.51 7.43 (m, 1H), 7.41 7.31 (m, 2H), 3.24 (q,
J ˆ 7.0 Hz, 1H), 1.87 (bs, 3H), 1.74 1.37 (m, 12H), 1.02 (d, J ˆ
7.0 Hz, 3H). 13C NMR (75 MHz, CDCl3): d ˆ 205.2, 139.2,
132.6, 128.5, 128.2, 49.3, 40.2, 37.0, 35.9, 28.7, 11.5; HR-MS (EI,
‡¥
70 eV): calcd. for (M ): 268.1827; found: 268.1823; IR (neat):
‡¥
calcd. for (M ): 180.1529; found: 180.1514; IR (neat), n ˆ 3115,
n ˆ 2905, 2850, 1675, 1595, 1445, 1355, 1210, 960, 720, 695 cmÀ1.
2950, 2825, 1650, 1380, 1370, 1275, 1055, 995, 790 cmÀ1.
3-Methoxy-2-methyl-1-phenylpropan-1-one (6)[23]
1-(3,5,5-Trimethylcyclohex-2-enyl)propan-2-one (8)[24]
Table 1: Entry 8: According to the General Procedure C:
B(C6F5)3 (15.5 mg, 50 mmol) in CH2Cl2 (1 mL) at room temper-
ature, 3 (178 mg, 1 mmol). After 24 h the reaction was
quenched by addition of NEt3. GC analysis indicated full
conversion but a mixture of 6 (54%) and propiophenone (40%).
No attempts were made to isolate 6 from the mixture.
Table 1: Entry 9: According to the General Procedure C:
Cu(OTf)2 (2.2 mg, 6 mmol) in CH2Cl2 (1 mL) at room temper-
ature, 3 (445 mg, 2.5 mmol). After 20 h the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2O, 96:4) afforded 6 as a
colorless oil; yield: 360 mg (2.0 mmol, 81%).
Table 1: Entry 10: According to the General Procedure D: 3
(178 mg, 1.0 mmol) in CH2Cl2 (1 mL) at room temperature,
BF3 ¥ OEt2 (1 drop, ꢀ 5 mol %). After 2 h the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2, 96:4) afforded 6 as a
colorless oil; yield: 130 mg (0.7 mmol, 73%).
Table 1: Entry 11: According to the General Procedure D: 3
(720 mg, 4.0 mmol) in CH2Cl2 (4 mL) at room temperature, n-
Bu2BOTf (0.04 mL, 1.0 M in CH2Cl2, 40 mmol). After 5 min the
reaction was quenched by addition of NEt3. Standard work-up
followed by column chromatography (SiO2, PE:Et2O, 96:4)
afforded 6 as a colorless oil; yield: 595 mg (3.3 mmol, 83%).
Table 3: Entry 8: According to the General Procedure C:
Cu(OTf)2 (1.8 mg, 4 mmol) neat at room temperature, 3
(712 mg, 4 mmol). After 18 h the reaction was quenched by
addition of NEt3. Standard work-up followed by column
chromatography (SiO2, PE:Et2O, 96:4) afforded 6 as a color-
Table 2: Entry 1: According to the General Procedure D: 7
(150 mg, 0.8 mmol) in CH2Cl2 (5 mL) at room temperature,
BF3 ¥ OEt2 (1 drop, ꢀ 7 mol %). After 20 min the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2O, 96:4) afforded 8 as a
colorless oil; yield: 108 mg (0.6 mmol, 72%).
Table 2: Entry 2: According to the General Procedure C:
Cu(OTf)2 (18.0 mg, 50 mmol) in CH2Cl2 (1 mL) at À 558C, 7
(180 mg, 1.0 mmol). After 1 h slowly warming up to À 208C,
after 4 h the reaction was quenched by addition of NEt3.
Standard work-up followed by column chromatography (SiO2,
PE:Et2O, 96:4) afforded 8 as a colorless oil; yield: 109 mg
(0.6 mmol, 60%).
Table 2: Entry 3: According to the General Procedure C:
B(C6F5)3 (15.5 mg, 50 mmol) in CH2Cl2 (1 mL) at room temper-
ature, 7 (180 mg, 1 mmol). After 5 h the reaction was quenched
by addition of NEt3. Standard work-up followed by column
chromatography (SiO2, PE:Et2O, 96:4) afforded 8 as a color-
less oil; yield: 54 mg (0.3 mmol, 30%). Rf (PE:Et2O, 98:2, SiO2):
1
0.1; H NMR (400 MHz, CDCl3): d ˆ 5.13 (s, 1H), 2.61 (mc,
1H), AB-signal (dA ˆ 2.39, dB ˆ 2.32, JAB ˆ 16.0 Hz, addition-
ally split by J ˆ 7.1 Hz/7.3 Hz; 2H), 2.14 (s, 3H), AB-signal
(dA ˆ 1.77, dB ˆ 1.54, JAB ˆ 17.2 Hz, 2H), 1.61 (s, 3H), 1.39 (dd,
J ˆ 12.4 Hz, 5.0 Hz, 1H), 0.93 (s, 3H), 0.87 (s, 3H), 0.99 0.80
(m, 1H); 13C NMR (100 MHz, CDCl3): d ˆ 208.9, 133.9, 123.0,
50.6, 44.2, 42.7, 31.9, 30.7, 30.1, 30.0, 25.4, 23.9; HRMS (EI,
‡¥
70 eV): calcd. for (M ): 180.1529; found: 180.1522; anal. calcd.
for C12H20O (180.29): C 79.94, H 11.18; found: C 79.73, H 11.01;
IR (neat): n ˆ 2950, 1715, 1435, 1360, 1255, 1155, 820 cmÀ1.
1024
¹ 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
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A Novel Method for the Preparation of a-Alkylated Ketones
FULL PAPERS
‡
11.9*, 10.7; HRMS (EI, 70 eV): calcd. for M : 262.1933; found:
1-Isoprenyloxymethyl-4-methoxybenzene (9)
262.1930; IR (neat): n ˆ 2930, 2860, 1680, 1615, 1585, 1515,
1465, 1300, 1250, 1170, 1040, 820 cmÀ1. *signals of the minor
isomer
According to the General Procedure A: TiCl4 (40 mL, 1.0 M in
CH2Cl2, 40 mmol) in THF (250 mL), TMEDA (12 mL,
80 mmol), Zn (6.00 g, 90 mmol), after the change of color is
complete 1,1-dibromomethane (1.52 mL, 22 mmol), acetic
acid 4-methoxybenzylic ester (1.80 g, 10 mmol). The reaction
mixture was stirred overnight. Standard work-up followed by
column chromatography (Al2O3, PE:Et2O, 95:5) afforded 9 as
a colorless oil; yield: 0.67 g (3.8 mmol, 38%). Rf (PE:Et2O, 96:4,
Al2O3): 0.4; 1H NMR (400 MHz, CDCl3): AA×XX×-system
with signals at d ˆ 7.13 and 6.74 (4H), 4.53 (s, 2H), 3.95 (t, J ˆ
0.9 Hz, 2H), 3.38 (s, 3H), 1.72 (s, 3H); 13C NMR (100 MHz,
CDCl3): d ˆ 160.0, 159.8, 129.7, 129.4, 114.0, 82.1, 69.4, 54.7,
1-(4-Methoxy-phenyl)-2-methylnonan-3-one (12)
Table 3: Entry 4: According to the General Procedure C:
B(C6F5)3 (5.8 mg, 10 mmol) in CH2Cl2 (1 mL) at room temper-
ature, 11 (258 mg, 1.0 mmol). After 5 min the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2O, 98:2) afforded 12 as
a colorless oil; yield: 182 mg (0.7 mmol, 71%). Rf (PE: Et2O,
96:4, SiO2): 0.5; 1H NMR (300 MHz, CDCl3): AA×XX× system
with signals at d ˆ 7.05 and 6.80 (4 H), 3.78 (s, 3 H), AB signal
(dA ˆ 2.90, dB ˆ 2.50, JAB ˆ 13.3 Hz, additionally split by J ˆ
7.3 Hz/7.0 Hz, 2H), 2.78 (ddq, J ˆ 7.0 Hz, 7.0 Hz, 7.0 Hz, 1H),
AB signal (dA ˆ 2.37, dB ˆ 2.24, JAB ˆ 16.8 Hz, additionally
split by J ˆ 7.3 Hz, 2H), 1.10 1.60 (m, 8H), 1.06 (d, J ˆ 6.8 Hz,
3H), 0.87 (t, J ˆ 7.1 Hz, 3H); 13C-NMR (75 MHz, CDCl3): d ˆ
214.4, 158.0, 131.8, 129.8, 113.7, 55.1, 48.2, 42.0, 38.3, 31.5, 28.8,
‡
21.1; HRMS (EI, 70 eV): calcd. for (M ): 178.0994; found:
178.0990; IR (neat): n ˆ 2995, 2955, 2835, 1655, 1615, 1515,
1465, 1365, 1280, 1250, 1175, 1060, 1035, 990, 825 cmÀ1.
4-(4-Methoxyphenyl)-butan-2-one (10)[25]
Table 3: Entry 1: According to the General Procedure C:
B(C6F5)3 (4.9 mg, 10 mmol) in CH2Cl2 (1 mL) at room temper-
ature, 9 (162 mg, 0.9 mmol). After 5 min the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2O, 90:10) afforded 10 as
a colorless oil; yield: 126 mg (0.7 mmol, 78%).
‡
23.4, 22.4, 16.5, 13.9; HRMS (EI, 70 eV): calcd. for (M ):
262.1923; found: 262.1928; IR (neat): n ˆ 2930, 2855, 1715,
1610, 1515, 1460, 1300, 1245, 1180, 1035, 820 cmÀ1.
Table 3: Entry 2: According to the General Procedure C, but
in air: B(C6F5)3 (5.1 mg, 10 mmol) in non-dried CH2Cl2 (1 mL)
at room temperature, 9 (178 mg, 1.0 mmol). After 5 min the
reaction was quenched by addition of NEt3. Standard work-up
followed by column chromatography (SiO2, PE:Et2O, 90:10)
afforded 10 as a colorless oil; yield: 119 mg (0.7 mmol, 67%). Rf
(PE:Et2O, 96:4, SiO2): 0.3; 1H NMR (300 MHz, CDCl3):
AA×XX×-system with signals at d ˆ 7.09 and 6.82 (4 H), 3.28
(s, 3 H), AA×XX×-system with signals at d ˆ 2.80 and 2.71 (4H),
2.12 (s, 3H); 13C NMR (75 MHz, CDCl3): d ˆ 208.0, 157.9,
132.9, 129.1, 113.8, 55.1, 45.3, 30.0, 28.8; HRMS (EI, 70 eV):
1-(1-Cyclohexyl-propenyloxymethyl)-4-
methoxybenzene (13)
According to the General Procedure A: TiCl4 (20 mL, 1.0 M in
CH2Cl2, 20 mmol) in THF (150 mL), TMEDA (6 mL,
40 mmol), Zn (3.00 g, 45 mmol), after the change of color is
complete 1,1-dibromoethane (1.35 mL, 11 mmol), cyclohex-
anecarboxylic acid 4-methoxybenzylic ester (1.24 g, 5 mmol).
The reaction mixture was stirred overnight. Standard work-up
followed by column chromatography (Al2O3, PE:Et2O, 95:5)
afforded 13 as a colorless oil; yield: 1.02 g (3.9 mmol, 78%). Rf
(PE, Al2O3): 0.3; 1H NMR (300 MHz, CDCl3): AA×XX× system
with signals at d ˆ 7.29 (4H) and 6.81 (4H), 4.71 (qd, J ˆ 6.8 Hz,
0.9 Hz, 1H), 4.62 (s, 2H), 3.33 (s, 3H), 2.11 (m, 1H), 1.69 (dd, J ˆ
6.8 Hz, 1.3 Hz, 1H), 2.00 1.00 (m, 10 H); 13C NMR (75 MHz,
CDCl3): d ˆ 160.8, 159.7, 131.2, 129.2, 114.0, 103.6, 71.6, 54.7,
‡
calcd. for (M ): 178.0994; found: 178.0996; IR (neat): n ˆ 2955,
2835, 1610, 1515, 1440, 1365, 1300, 1245, 1180, 1035, 820,
740 cmÀ1.
1-(1-Hexylpropenyloxymethyl)-4-methoxybenzene
(11)
‡
41.1, 31.8, 26.8, 26.7, 11.9; HRMS (EI, 70 eV): calcd. for (M ):
260.1776; found: 260.1779; IR (neat): n ˆ 2925, 2850, 1675,
1615, 1515, 1450, 1300, 1250, 1170, 1035 cmÀ1.
According to the General Procedure A: TiCl4 (20 mL (1.0 M in
CH2Cl2), 20 mmol) in THF (150 mL), TMEDA (6 mL,
40 mmol), Zn (3.00 g, 45 mmol), after the change of color is
complete 1,1-dibromoethane (1.35 mL, 11 mmol), heptanoic
acid-4-methoxybenzylic ester (1.25 g, 5 mmol). The reaction
mixture was stirred overnight. Standard work-up followed by
column chromatography (Al2O3, PE:Et2O, 95:5)afforded 11 as
a colorless oil; yield: 1.00 g (3.8 mmol, 76%). Z/E ˆ 78:22; Rf
(PE:Et2O ˆ 96:4, Al2O3): 0.6; 1H NMR (400 MHz, C6D6):
AA×XX× system with signals at d ˆ 7.26 and 6.79 (4H), 7.22*
(part of an AA×XX× system, 2H), 4.65 (q, J ˆ 6.7 Hz, 1H), 4.61
(s, 2H), 4.55* (s, 2H), 4.47* (q, J ˆ 6.9 Hz, 1H), 3.32 (s, 3H),
3.30'* (s, 3H), 2.28* (t, J ˆ 7.5 Hz, 2H), 2.11 (t, J ˆ 7.3 Hz, 2H),
1.72 (dt, J ˆ 6.7 Hz, 1.1 Hz, 3H), 0.80 2.00 (m, 11H); 13C NMR
(100 MHz, C6D6): d ˆ 159.7, 159.7*, 157.1*, 155.2, 131.0,
130.5*, 129.2*, 129.1, 114.0, 104.8, 91.3*, 70.1, 68.5*, 54.7,
32.5, 32.1 32.0*, 30.4*, 29.3*, 29.2, 27.8, 27.6*, 23.0, 22.9, 14.2,
1-Cyclohexyl-3-(4-methoxyphenyl)-2-methylpropan-1-
one (14)
Table 3: Entry 5: According to the General Procedure C:
B(C6F5)3 (3.5 mg, 7 mmol) in CH2Cl2 (1 mL) at room temper-
ature, 13 (183 mg, 0.7 mmol). After 5 min the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2O, 95:5) afforded 14 as
a colorless oil; yield: 131 mg (0.7 mmol, 71%). Rf (PE:Et2O,
96:4, SiO2): 0.3; 1H NMR (400 MHz, CDCl3): AA×XX×system
with signals at d ˆ 7.03 and 6.77 (4H), 3.77 (s, 3H), 2.86 (m, 2H),
2.45 (m, 1H), 2.25 (tt, J ˆ 10.9 Hz, 3.0 Hz, 1H), 1.80 1.10 (m,
10H), 1.01 (d, J ˆ 6.8 Hz, 3H); 13C NMR (75 MHz, CDCl3) d ˆ
217.0, 157.9, 132.0, 129.9, 113.7, 55.2, 50.2, 46.7, 38.4, 28.2, 27.9,
Adv. Synth. Catal. 2003, 345, 1017 1030
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¹ 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1025

Andreas Gans‰uer et al.
FULL PAPERS
‡
25.6, 25.5, 16.9; HRMS (EI, 70 eV): calcd. for (M ): 260.1776;
found: 260.1776; IR (neat): n ˆ 2930, 2855, 1705, 1610, 1510,
1450, 1245, 1180, 1035, 990, 810 cmÀ1.
column chromatography (Al2O3, PE) afforded 17 as a colorless
oil; yield: 1.83 g (8.9 mmol, 89%). Z/E ˆ 80:20; Rf (PE, Al2O3):
0.6, 0.5*; 1H NMR (400 MHz, C6D6): d ˆ 4.80 (qq, J ˆ 6.6 Hz,
0.7 Hz, 1H), 1.97 (bs, 3H), 1.87 (bs, 6H), 1.76 (quintet, J ˆ
1.3 Hz, 3H), 1.68 (dq, J ˆ 6.5 Hz, 1.2 Hz, 3H), 1.45 (s, 6H);
1H NMR* (400 MHz, C6D6): d ˆ 5.06 (qq, J ˆ 6.9 Hz, 1.0 Hz,
1H), 1.96 (bs, 3H), 1.88 1.82 (m, 6H), 1.74 (quintet, J ˆ 1.0 Hz,
3H), 1.50 (dq, J ˆ 6.6 Hz, 1.1 Hz, 3H), 1.49 1.45 (m, 6H);
13C NMR (100 MHz, C6D6): d ˆ 149.5, 110.6, 76.3, 44.2, 36.9,
31.7, 24.6, 12.6; 13C-NMR* (100 MHz, C6D6): d ˆ 148.9, 109.5,
75.9, 43.9, 37.0, 31.6, 19.4, 12.9; HRMS (EI, 70 eV): calcd. for
1-Methoxy-2-(1-methoxymethoxypropenyl)-benzene
(15)
According to the General Procedure A: TiCl4 (40 mL, 1.0 M in
CH2Cl2, 40 mmol) in THF (150 mL), TMEDA (12 mL,
80 mmol), Zn (6.00 g, 90 mmol), after the change of color is
complete 1,1-dibromoethane (2.70 mL, 22 mmol), and 2-
methoxybenzoic acid methoxymethyl ester (1.96 g, 10 mmol).
The reaction mixture was stirred overnight. Standard work-up
followed by column chromatography (Al2O3, PE:Et2O, 95:5)
afforded 15 as a colorless oil; yield: 1.17 g (5.6 mmol, 56%).
Z/E ˆ 80:20; Rf (PE, Al2O3): 0.2; 1H NMR (400 MHz, C6D6):
d ˆ 7.47 (dd, J ˆ 7.5 Hz, 1.8 Hz, 1H), 7.39* (dd, J ˆ 7.4 Hz,
1.8 Hz, 1H), 7.14* (ddd, J ˆ 8.1 Hz, 7.3 Hz, 1.8 Hz, 1H), 7.10
(ddd, J ˆ 8.2 Hz, 7.4 Hz, 1.8 Hz, 1H), 6.88* (td, J ˆ 7.6 Hz,
1.2 Hz, 1H), 6.85 (td, J ˆ 7.5 Hz, 1.0 Hz, 1H), 6.61* (dd, J ˆ
8.0 Hz, 0.6 Hz, 1H), 6.55 (dd, J ˆ 8.3 Hz, 0.9 Hz, 1H), 5.42* (q,
J ˆ 7.0 Hz, 1H), 5.22 (q, J ˆ 6.8 Hz, 1H), 4.89* (s, 2H), 4.75 (s,
2H), 3.31* (s, 3H), 3.28 (s, 3H), 3.26* (s, 3H), 3.24 (s, 3H), 1.93
(d, J ˆ 6.8 Hz, 3H), 1.56* (d, J ˆ 6.9 Hz, 3H); 13C NMR
(100 MHz, C6D6): d ˆ 158.3*, 158.2, 151.5*, 151.1, 132.3*,
131.8, 130.1*, 129.8, 126.3*, 125.7, 121.1, 120.8*, 111.8*, 111.5,
110.4, 102.5*, 94.8, 94.6*, 56.4, 55.8*, 55.4*, 55.3, 13.2*, 11.5;
‡¥
(M ): 206.1687; found: 206.1667; IR (neat): n ˆ 2910, 2850,
1675, 1450, 1350, 1325, 1300, 1190, 1070, 980 cmÀ1. * spectra of
minor isomer.
3-Adamantan-1-ylbutan-2-one (18)
Table 3: Entry 8: According to the General Procedure C:
B(C6F5)3 (5.1 mg, 10 mmol) in CH2Cl2 (1 mL) at room temper-
ature, 17 (206 mg, 1 mmol). After 15 min the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2O, 97:3) afforded 18 as
a colorless oil; yield; 142 mg (0.7 mmol, 69%). Rf (PE: Et2O,
97:3, SiO2): 0.4; 1H NMR (300 MHz, CDCl3): d ˆ 2.30 (q, J ˆ
7.0 Hz, 1H), 2.13 (s, 3H), 1.96 (mc, 3H), 1.56 (mc, 9H), 1.49,
(ddd, J ˆ 12.2 Hz, 4.9 Hz, 2.7 Hz, 3H), 0.97 (d, J ˆ 7.2 Hz, 3H);
13C-NMR (75 MHz, CDCl3): d ˆ 213.8, 56.9, 40.0, 37.1, 35.5,
‡¥
32.8, 28.7, 10.7; HRMS (EI, 70 eV): calcd. for (M ): 206.1687;
‡¥
HRMS (EI, 70 eV): calcd. for (M ): 208.1111; found: 208.1083.
found: 206.1673; anal. calcd. for C14H22O (206.32): C 81.50, H
10.75; found: C 81.44, H 10.86; IR (neat): n ˆ 3380, 2900, 2850,
2675, 1700, 1450, 1420, 1355, 1165, 1065, 955, 815 cmÀ1.
*signals of the minor isomer
3-Methoxy-1-(2-methoxyphenyl)-2-methylpropan-1-
one (16)
(1-tert-Butoxypropenyl)-benzene (19)[18]
Table 3: Entry 7: According to the General Procedure C:
Cu(OTf)2 (3.6 mg, 10 mmol) in CH2Cl2 (1 mL) at room temper-
ature, 15 (208 mg, 1.0 mmol). After 5 min the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, CH:EE, 2% EE) afforded 16
as a colorless oil; yield: 148 mg (0.7 mmol, 71%). Rf (CH:EE ˆ
98:2, SiO2): 0.1; 1H NMR (400 MHz, CDCl3): d ˆ 7.77 (dd, J ˆ
7.6 Hz, 1.8 Hz, 1H), 7.05 (ddd, J ˆ 8.3 Hz, 7.3 Hz, 1.8 Hz, 1H),
6.74 (td, J ˆ 7.5 Hz, 0.9 Hz, 1H), 6.41 (d, J ˆ 8.3 Hz, 1H), 3.82
(sextet, J ˆ 6.6 Hz, 1H), 3.73 (dd, J ˆ 8.8 Hz, 6.2 Hz, 1H), 3.37
(dd, J ˆ 8.8 Hz, 6.3 Hz, 1H), 3.16 (s, 3H), 3.06 (s, 3H), 1.27 (d,
J ˆ 6.8 Hz, 1H); 13C-NMR (100 MHz, CDCl3): d ˆ 204.3, 158.1,
132.6, 130.8, 130.1, 121.0, 111.6, 75.3, 58.7, 54.9, 46.5, 14.3;
According to the General Procedure A: TiCl4 (60 mL, 1.0 M in
CH2Cl2, 60 mmol) in THF (250 mL), TMEDA (18 mL,
120 mmol), Zn (9.00 g, 135 mmol), after the change of color
is complete 1,1-dibromoethane (4.04 mL, 16.5 mmol), and
benzoic acid tert-butyl ester (2.66 g, 15 mmol). The reaction
mixture was stirred overnight. Standard work-up followed by
column chromatography (Al2O3, PE) afforded 19 as a colorless
oil; yield: 2.48 g (13.1 mmol, 87%). Z/E ˆ 80:20; Rf (PE,
Al2O3): 0.7; 1H NMR (400 MHz, CDCl3): d ˆ 7.39 7.30**
(m, 2H), 7.27 7.10** (m, 3H), 5.30 (q, J ˆ 6.7 Hz, 1H), 5.28*
(q, J ˆ 7.4 Hz, 1H), 1.70 (d, J ˆ 6.8 Hz, 3H), 1.62* (d, J ˆ
7.3 Hz, 3H), 1.13 (s, 9H), 1.08 (s, 9H) ; 13C NMR (100 MHz,
CDCl3): d ˆ 152.0, 150.6*, 141.6, 138.8*, 128.8*, 127.9, 127.7*,
127.3*, 127.1, 126.3, 114.2, 112.9*, 79.3, 77.8*, 29.6, 29.2*, 13.2*,
‡¥
HRMS (EI, 70 eV): calcd. for (M ): 208.1111; found: 208.1086;
‡¥
anal. calcd for C12H16O3 (208.25): C 79.94, H 11.18; found: C
79.73, H 11.01; IR (neat): n ˆ 2950, 1715, 1435, 1360, 1255, 1160,
820 cmÀ1.
12.6; HRMS (EI, 70 eV): calcd. for (M ): 190.1371; found:
190.1354; IR (neat): n ˆ 2975, 2930, 1650, 1365, 1320, 1170,
1050, 1020, 780, 730, 700 cmÀ1. *signals of the minor isomer, **
signals of major and minor isomer not separated.
1-(1-Methylpropenyloxy)-adamantane (17)
2,3,3-Trimethyl-1-phenylbutan-1-one (20)[26]
According to the General Procedure A: TiCl4 (40 mL (1.0 M in
CH2Cl2), 40 mmol) in THF (150 mL), TMEDA (12 mL,
80 mmol), Zn (6.00 g, 90 mmol), after the change of color is
complete 1,1-dibromoethane (2.70 mL, 22 mmol), and acetic
acid adamantan-1-yl ester (1.94 g, 10 mmol). The reaction
mixture was stirred overnight. Standard work-up followed by
Table 3: Entry 9: According to the General Procedure D: 19
(190 mg, 1.0 mmol) in CH2Cl2 (1 mL) at À 788C, BF3 ¥ OEt2 (1
drop, ꢀ 5 mol %). After 2 h warming up to room temperature
the reaction and quenching by addition of NEt3. Standard
work-up followed by column chromatography (SiO2, PE:Et2O,
1026
¹ 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
Adv. Synth. Catal. 2003, 345, 1017 1030

A Novel Method for the Preparation of a-Alkylated Ketones
FULL PAPERS
98:2) afforded 20 as a colorless oil; yield: 61 mg (0.3 mmol,
32%). Rf (PE:Et2O, 98:2, SiO2): 0.3; 1H NMR (400 MHz,
CDCl3): d ˆ 7.85 (m, 2H), 7.43 (dddd, J ˆ 8.2 Hz, 6.5 Hz,
2.3 Hz, 1.1 Hz, 1H), 7.34 (m, 2H), 3.34 (q, J ˆ 7.0 Hz, 1H), 1.06
(d, J ˆ 7.0 Hz, 3H); 0.88 (s, 9H); 13C NMR (100 MHz, CDCl3):
d ˆ 205.5, 139.1, 132.7, 128.6, 128.3, 48.4, 33.9, 28.1, 13.5;
129.7, 128.84, 128.80, 128.1, 127.1, 90.0, 82.3; HRMS (EI,
70 eV): calcd. for (M ): 236.1201; found: 236.1202; IR (neat):
‡
n ˆ 3030, 2825, 2725, 1720, 1600, 1495, 1450, 1405, 1180,
1030 cmÀ1.
‡¥
HRMS (EI, 70 eV): calcd. for (M ): 190.1371; found: 190.1367;
(E)-3,5-Diphenyl-4-pentenal (24)[12c]
IR (neat): n ˆ 3060, 2960, 1680, 1595, 1445, 1395, 1225, 1180,
1000, 965 cmÀ1.
Table 4: Entry 2: According to the General Procedure C:
B(C6F5)3 (1.9 mg, 4 mmol) in CH2Cl2 (15 mL) at room temper-
ature, 23 (370 mg, 15 mmol). After 5 h the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2O, 90:10, SiO2) afford-
ed 24 as a white solid; yield: 305 mg (1.3 mmol, 82%). Rf
1,5,5-Trimethyl-3-vinyloxycyclohexene (21)[27]
According to the General Procedure B: mercury(II) acetate
(3.2 g, 10 mmol) in ethyl vinyl ether (500 mL), 3,5,5-trimethyl-
2-cyclohexen-1-ol (7.0 g, 50 mmol). After 5 d stirring at room
temperature standard work-up followed by column chroma-
tography through a short column (Al2O3, pentane) afforded 21
as a colorless oil; yield: 7.1 g (43 mmol, 86%). Rf (PE, Al2O3):
0.8. 1H NMR (400 MHz, C6D6): d ˆ 6.22 (dd, J ˆ 14.3 Hz,
6.6 Hz, 1H), 5.44 (bs, 1H), 4.34 (dd, J ˆ 14.3 Hz, 1.2 Hz, 1H),
4.19 (mc, 1H), 3.93 (dd, J ˆ 6.6 Hz, 1.2 Hz, 1H), 1.50 1.42 (m,
2H), 1.36 (s, 3H), 1.33 (dd, J ˆ 12.8 Hz, 8.6 Hz, 1H), 1.24 (d, J ˆ
17.7 Hz, 1H), 0.73 (s, 3H), 0.63 (s, 3H); 13C NMR (100 MHz,
C6D6): d ˆ 151.2, 136.8, 120.7, 88.0, 74.2, 44.2, 41.4, 30.7, 30.6,
26.8, 23.6; IR (neat): n ˆ 3115, 2955, 1630, 1455, 1325, 1195,
1
(PE:Et2O, 98:2): 0.1; H NMR (300 MHz, CDCl3): d ˆ 9.67
(t, J ˆ 2.0 Hz, 1H), 7.33 7.07 (m, 10H), 6.35 (d, J ˆ 16.0 Hz,
1H), 6.25 (dd, J ˆ 16.0 Hz, 6.6 Hz, 1H), 4.04 (q, J ˆ 7.2 Hz, 1H),
AB signal (dA ˆ 2.88, dB ˆ 2.82, JAB ˆ 16.8 Hz, additionally
split by J ˆ 7.5 Hz/7.3 Hz, 2.2 Hz/1.9 Hz, 2H); 13C NMR
(75 MHz, CDCl3): d ˆ 201.4, 142.8, 137.3, 132.2, 130.8, 129.2,
128.0, 127.9, 127.3, 126.7, 49.4, 43.3; HRMS (EI, 70 eV): calcd.
‡
for M : 236.1201; found: 236.1199; anal. calcd for C17H16O
(236.1): C 86.41, H 6.82; found: C 086.25, H 6.86; IR (neat): n ˆ
3025, 2840, 2740, 1715, 1595, 1490, 1445, 1410, 1050, 1015, 965,
765, 750, 695 cmÀ1.
1050, 985, 945, 820 cmÀ1
.
3-(1-tert-Butylvinyloxy)-1,5,5-trimethylcyclohexene
(25)
(3,5,5-Trimethylcyclohex-2-enyl)-acetaldehyde (22)
Table 4: Entry 1: According to the General Procedure D: 21
(166 mg, 1.0 mmol) in CH2Cl2 (100 mL) at room temperature,
BF3 ¥ OEt2 (1 drop, ꢀ 5 mol %). After 18 h the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, pentane:Et2O, 98:2) afforded
22 as a colorless oil; yield: 140 mg (0.8 mmol, 84%). Rf
(PE:Et2O ˆ 98:2, SiO2): 0.2; 1H NMR (400 MHz, CDCl3):
d ˆ 9.72 (t, J ˆ 2.2 Hz, 1H), 5.12 (bs, 1H), 2.62 (bs, 1H), AB
According to the General Procedure A: TiCl4 (20 mL, 1.0 M in
CH2Cl2, 20 mmol) in THF (125 mL), TMEDA (6 mL,
40 mmol), Zn (3.00 g, 45 mmol), after the change of color is
complete dibromomethane (0.76 mL, 11 mmol), and 2,2-
dimethylpropionic acid 3,5,5-trimethylcyclohex-2-enyl ester
(1.07 g, 4.8 mmol). The reaction mixture was stirred overnight.
Standard work-up followed by column chromatography
(Al2O3, PE) afforded 25 as a light yellow oil; yield: 0.26 g
ˆ
signal (dA ˆ 2.34, dB 2.27, JAB ˆ 16.2 Hz, additionally split by
1
(1.1 mmol, 23%). Rf (PE, Al2O3): 0.9; H NMR (400 MHz,
J ˆ 6.7 Hz/7.1 Hz, 2.2 Hz, 2H), AB signal (dA ˆ 1.74, dB ˆ 1.51,
JAB ˆ 17.2 Hz, 2H), 1.57 (s, 3H), 1.45 (dd, J ˆ 12.8 Hz, 5.7 Hz,
1H), 0.95 (m, 1H), 0.88 (s, 3H), 0.82 (s, 3H); 13C NMR
(100 MHz, CDCl3) d ˆ 203.0, 134.5, 122.4, 50.3, 43.9, 42.4, 31.7,
C6D6): d ˆ 5.68 (s, 1H), 4.61 (bs, 1H), 4.15 (s, 1H), 3.97 (s, 1H),
1.70 1.36 (m, 4H), 1.54 (bs, 3H), 1.22 (s, 9H), 0.91 (s, 3H), 0.81
(s, 3H); 13C NMR (100 MHz, CDCl3): d ˆ 169.7, 136.7, 120.9,
78.4, 71.3, 44.7, 41.3, 36.5, 30.9, 30.7, 29.1, 27.8, 24.1; HRMS (EI,
‡¥
30.0, 28.9, 25.3, 23.9; HRMS (EI, 70 eV): calcd. for (M ):
‡¥
70 eV): calcd. for (M ): 222.2003; found: 222.1988.
166.1358; found: 166.1359; anal. calcd for C11H18O (166.1): C
79.47, H 10.91; found: C 79.48, H 10.96; IR (neat): n ˆ 2950,
2715, 1725, 1455, 1365, 1135, 1065, 865, 820 cmÀ1.
3,3-Dimethyl-1-(3,5,5-trimethylcyclohex-2-enyl)-
butan-2-one (26)[24]
1,3-Diphenyl-1-vinyloxyprop-2-ene (23)[12c]
Table 4: Entry 3: According to the General Procedure D: 25
(222 mg, 1.0 mmol) in CH2Cl2 (10 mL) at À 788C, BF3 ¥ OEt2
(1 drop, ꢀ 5 mol %). After 5 min the reaction was quenched by
addition of NEt3. Standard work-up followed by column
chromatography (SiO2, CH:EE, 99:1) afforded 26 as a color-
less oil; yield: 139 mg (0.6 mmol, 63%). Rf (PE:Et2O ˆ 98:2,
SiO2): 0.3; 1H NMR (400 MHz, CDCl3): d ˆ 5.10 (s, 1H), 2.67
(mc, 1H), 2.48 2.33 (m, 2H), AB signal (dA ˆ 1.77, dB ˆ 1.53,
JAB ˆ 17.2 Hz, 2H), 1.40 (dd, J ˆ 12.3 Hz, 5.4 Hz, 1H), 1.11 (s,
9H), 0.92 (s, 3H), 0.87 (s, 3H), 0.81 (t, J ˆ 12.0 Hz, 1H);
13C NMR (100 MHz, CDCl3): d ˆ 215.3, 133.6, 123.8, 44.3, 44.2,
43.4, 42.5, 32.0, 30.1, 29.6, 26.4, 25.4, 24.0; HRMS (EI, 70 eV):
According to the General Procedure B: Mercury(II) acetate
(0.64 g, 2 mmol) in ethyl vinyl ether (250 mL), trans-1,3-
diphenyl-2-propen-1-ol (1.05 g, 5 mmol). After 5 d stirring at
room temperature standard work-up followed by column
chromatography through a short column (Al2O3, pentane)
afforded 23 as a colorless oil; yield: 0.48 g (2.0 mmol, 40%).
1H NMR (300 MHz, C6D6): d ˆ 7.53 6.79 (m, 10H), 6.52 (d,
J ˆ 16.0 Hz, 1H), 6.38 (dd, J ˆ 14.0 Hz, 6.6 Hz, 1H), 6.25 (dd,
J ˆ 15.9 Hz, 6.5 Hz, 1H), 5.18 (d, J ˆ 6.4 Hz, 1H), 4.53 (dd, J ˆ
14.2 Hz, 1.6 Hz, 1H), 4.07 (dd, J ˆ 6.5 Hz, 1.6 Hz, 1H);
13C NMR (75 MHz, C6D6): d ˆ 150.6, 140.8, 136.8, 131.9,
Adv. Synth. Catal. 2003, 345, 1017 1030
asc.wiley-vch.de
¹ 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1027

Andreas Gans‰uer et al.
FULL PAPERS
‡¥
calcd. for (M ): 222.2003; found: 222.1982; IR (neat): n ˆ 2950,
1H NMR (400 MHz, C6D6): d ˆ 5.77 (bs, 1H), 4.74* (q, J ˆ
7.0 Hz; 1H), 4.74* (s, 1H), 1.82 (dd, J ˆ 12.6 Hz, 5.9 Hz, 1H),
1.69 (d, J ˆ 7.1 Hz, 3H), 1.63 1.69 (m, 1H), 1.57 (dd, J ˆ
12.1 Hz, 8.6 Hz, 1H), 1.55 (s, 3H), 1.40 (d, J ˆ 17.2 Hz, 1H),
1.20 (s, 9H), 0.92 (s, 3H), 0.81 (s, 3H); 13C NMR (100 MHz,
C6D6): d ˆ 163.9, 135.7, 123.0, 99.2, 75.3, 44.7, 43.5, 37.1, 31.7,
1705, 1475, 1365, 1270, 1135, 1070, 990, 820 cmÀ1.
3-(1-Cyclohexylpropenyloxy)-1,5,5-
trimethylcyclohexene (27)
‡¥
31.4, 29.9, 26.8, 24.1, 13.1; MS (EI, 70 eV): m/z (%) ˆ 236 (M ,
0.2), 123 (100), 107 (3), 81 (11); IR (neat), n ˆ 2955, 2825, 1655,
According to the General Procedure A: TiCl4 (20 mL (1.0 M in
CH2Cl2), 20 mmol) in THF (125 mL), TMEDA (6 mL,
40 mmol), Zn (3.00 g, 45 mmol), after the change of color is
complete 1,1-dibromoethane (1.35 mL, 11 mmol), cyclohex-
anecarboxylic acid 3,5,5-trimethylcyclohex-2-enyl ester
(1.25 g, 5.0 mmol). The reaction mixture was stirred overnight.
Standard work-up followed by column chromatography
(Al2O3, PE) afforded 27 as a colorless oil; yield: 0.97 g
ˆ
1455, 1390, 1325, 1300, 1130, 1000, 970 cmÀ1.
2,2-Dimethyl-4-(3,5,5-trimethylcyclohex-2-enyl)-
entan-3-one (30)
Table 4: Entry 5: According to the General Procedure D: 29
(472 mg, 2.0 mmol) in CH2Cl2 (20 mL) at room temperature,
BF3 ¥ OEt2 (1 drop, ꢀ 2.5 mol %). After 5 min the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2O, 99:1) afforded 30 as
a colorless oil;: yield: 277 mg (1.1 mmol, 59%). drˆ 64:36; Rf
(3.7 mmol, 74%).Z/E
> 99: < 1, Rf (PE, Al2O3): 0.8;
1H NMR (400 MHz, C6D6): d ˆ 5.68 (s, 1H), 4.77 (qd, J ˆ
6.6 Hz, 0.9 Hz, 1H), 4.50 (mc, 1H), 2.25 2.00 (m, 3H), 1.78
(dd, J ˆ 6.6 Hz, 1.2 Hz, 3H), 1.86 1.49 (m, 6H), 1.69 (d, J ˆ
15.3 Hz, 1H), 1.56 (s, 3H), 1.31 1.04 (m, 6H), 0.93 (s, 3H), 0.82
(s, 3H); 13C-NMR (100 MHz, CDCl3): d ˆ 159.6, 135.8, 122.7,
103.6, 72.6, 44.7, 43.1, 40.9, 32.5, 32.4, 31.6, 31.2, 27.27, 27.26,
1
(PE:Et2O, 98:2; SiO2): 0.3; H NMR (300 MHz, CDCl3): d ˆ
5.32* (s, 1H), 4.86 (s, 1H), 2.71 (dq, J ˆ 8.3 Hz, 6.8 Hz, 1H),
2.67* (dq, J ˆ 15.9 Hz, 6.8 Hz, 1H), 2.37 2.15** (m, 2H), 1.68
‡¥
27.23, 27.0, 24.0, 11.7; HRMS (EI, 70 eV): calcd. for (M ):
262.2319; found: 262.2301; IR (neat), n ˆ 2925, 2855, 1670,
ˆ
(d, J 17.3 Hz, 1H), 1.55* (s, 3H), 1.48 (s, 3H), 1.40 (d, J ˆ
1450, 1360, 1315, 1170, 1130, 1040, 950 cmÀ1.
17.1 Hz, 1H), 1.33 (dt, J ˆ 5.6 Hz, 1.5 Hz, 1H), 1.29 (dt, J ˆ
5.5 Hz, 1.5 Hz, 1H), 1.05 (s, 9H), 1.03* (s, 9H), 0.95* (d, J ˆ
6.8 Hz, 3H), 0.89 (d, J ˆ 6.8 Hz, 3H), 0.85 (s, 3H), 0.80* (s, 3H),
0.72** (s, 3H); 13C NMR (75 MHz, CDCl3): d ˆ 219.9, 219.4*,
134.4*, 133.7, 123.2, 120.8*, 45.5, 44.8*, 44.7*, 44.4, 44.3*, 44.2,
41.6*, 39.4, 37.2, 36.8*, 32.2, 32.1*, 30.1, 30.0*, 26.7, 26.6*, 25.4,
25.1*, 24.3*, 24.0, 15.9*, 15.8; HRMS (EI, 70 eV): calcd. for
1-Cyclohexyl-2-(3,5,5-trimethylcyclohex-2-enyl)-
propan-1-one (28)
Table 4: Entry 4: According to the General Procedure C:
Cu(OTf)2 (1.6 mg, 4 mmol) in CH2Cl2 (1 mL) at -158C, 27
(131 mg, 0.5 mmol). After 5 h the reaction was quenched by
addition of NEt3. Standard work-up followed by column
chromatography (SiO2, PE:Et2O, 96:4) afforded 28 as a
colorless oil; yield: 77 mg (0.3 mmol, 59%). drˆ 69:31; Rf
(PE:Et2O ˆ 98:2, SiO2): 0.2; 1H NMR (400 MHz, CDCl3):
d ˆ 5.14* (s, 1H), 4.90 (s, 1H); 2.45 (quintet, J ˆ 7.1 Hz, 1H),
1.50 (s, 3H), 0.91* (d, J ˆ 6.9 Hz, 1H), 0.63 (d, J ˆ 6.9 Hz, 1H),
0.81 (s, 3H), 0.73 (s, 3H), 2.45 0.71 (m); 13C NMR (100 MHz,
CDCl3): d ˆ 217.9, 217.6*, 134.7*, 134.1, 122.8, 120.7*, 50.8*,
50.4, 49.9, 48.9*, 44.3*, 44.1, 40.7*, 38.7, 36.2*, 36.1, 32.2, 32.1*,
30.1*, 30.0, 29.0*, 28.9, 28.3*, 28.0, 26.1, 26.0*, 25.9, 25.8*, 25.7*,
25.3, 25.24*, 24.22*, 24.1, 13.7*, 13.3; HRMS (EI, 70 eV): calcd.
‡¥
(M ): 236.2161; found: 236.2135; anal. calcd. for C16H28O
(236.39): C 81.29, H 11.94; found: C 81.05, H 11.94; IR (neat):
n ˆ 2950, 1700, 1480, 1365, 1060, 990, 960, 905, 825 cmÀ1.
*signals of minor diastereomer; ** signals of major and minor
diastereomer not separated.
[1-(3,5,5-Trimethylcyclohexenyloxy)-propenyl]-
benzene (31)
According to the General Procedure A: TiCl4 (20 mL, 1.0 M in
CH2Cl2, 20 mmol) in THF (125 mL), TMEDA (6 mL,
40 mmol), Zn (3.00 g, 45 mmol), after the change of color is
complete 1,1-dibromoethane (1.35 mL, 11 mmol), benzoic
acid 3,5,5-trimethyl-cyclohex-2-enyl ester (1.22 g, 5.0 mmol).
The reaction mixture was stirred overnight. Standard work-up
followed by column chromatography (Al2O3, PE) afforded 31
as a colorless oil; yield: 1.03 g (4.0 mmol, 80%). Z/E ˆ 91:9; Rf
(PE, Al2O3): 0.7; 1H NMR (400 MHz, CDCl3): d ˆ 7.37
7.28** (m, 2H), 7.25 7.20** (m, 2H), 7.18 7.12** (m, 1H),
5.49* (bs, 1H), 5.43 (bs, 1H), 5.25 (q, J ˆ 6.9 Hz, 1H), 4.93* (q,
J ˆ 7.5 Hz, 1H), 4.38* (mc, 1H), 4.13 (mc, 1H), AB signal (dA ˆ
1.82, dB ˆ 1.51. JAB ˆ 17.5 Hz, 2H), 1.72 (d, J ˆ 6.6 Hz, 3H), 1.61
(bs, 3H), 1.64 1.61 (m, 1H), 1.42 (dd, J ˆ 12.6 Hz, 8.9 Hz, 1H),
0.96** (s, 3H), 0. 68** (s, 3H); 13C NMR (100 MHz, CDCl3):
d ˆ 153.2, 137.3, 136.4, 127.9, 127.5, 126.1, 120.8, 120.3*, 110.2,
99.4*, 73.6, 71.4*, 44.2, 41.8, 41.2*, 31.2, 31.0, 26.4, 23.7, 13.0*,
‡¥
for (M ): 262.2319; found: 262.2293; anal. calcd. for C18H30O
(262.43): C 82.38, H 11.20; found: C 82.40, H 11.33; IR (neat):
n ˆ 2930, 1705, 1450, 1375, 1145, 990, 905, 820 cmÀ1. *signals of
the minor diastereomer.
3-(1-tert-Butylpropenyloxy)-1,5,5-
trimethylcyclohexene (29)
According to the General Procedure A: TiCl4 (20 mL (1.0 M in
CH2Cl2), 20 mmol) in THF (125 mL), TMEDA (6 mL,
40 mmol), Zn (3.00 g, 45 mmol), after the change of color is
complete 1,1-dibromoethane (1.35 mL, 11 mmol), cyclohex-
anecarboxylic acid 3,5,5-trimethylcyclohex-2-enyl ester
(1.07 g, 4.8 mmol). The reaction mixture was stirred overnight.
Standard work-up followed by column chromatography
(Al2O3, PE) afforded 29 as a colorless oil; yield: 1.03 g
‡¥
11.7; HR-MS (EI, 70 eV): calcd. for (M ): 256.1827; found:
256.1831; IR (neat): n ˆ 3030, 2950, 2825, 1655, 1490, 1445,
ˆ
(4.3 mmol, 91%). Z/E > 99: < 1; Rf (PE, Al2O3): 0.9;
1365, 1320, 1260, 1175, 1050, 970, 945, 810, 775, 750, 700,
1028
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A Novel Method for the Preparation of a-Alkylated Ketones
FULL PAPERS
645 cmÀ1. * signals of minor isomer, **signals of major and
minor isomer not separated.
J ˆ 13.7 Hz, 6.9 Hz, 6.9 Hz, 0.8 Hz, 1H), 1.93 (ddd, J ˆ 14.0 Hz,
7.1 Hz, 7.1 Hz, 1H), 1.00 1.90 (m, 10H), 1.03 (d, J ˆ 6.9 Hz,
3H); 13C NMR (100 MHz, CDCl3): d ˆ 216.9, 135.9, 116.5, 49.8,
44.1, 37.2, 28.4, 28.2, 25.8, 16.4; HRMS (EI, 70 eV): calcd. for
‡
(M ): 180.1514; found: 180.1519; IR (neat): n ˆ 2930, 2855,
1-Phenyl-2-(3,5,5-trimethylcyclohex-2-enyl)-propan-1-
one (32)
1705, 1640, 1450, 1375, 1145, 995, 915 cmÀ1.
Table 4: Entry 6: According to the General Procedure C:
Cu(OTf)2 (15.5 mg, 50 mmol) in CH2Cl2 (1 mL) at À 408C, 31
(256 mg, 1.0 mmol). After 3 h at À 308C the reaction was
quenched by addition of NEt3. Standard work-up followed by
column chromatography (SiO2, PE:Et2O, 99:1) afforded 32 as
a white solid; yield: 197 mg (0.8 mmol, 77%). drˆ 57:43, Rf
[1-(2-Methylallyloxy)-prop-(Z)-enyl]-cyclohexane (35)
According to the General Procedure A: TiCl4 (20 mL, 1.0 M in
CH2Cl2, 20 mmol) in THF (125 mL), TMEDA (6 mL,
40 mmol), Zn (3.00 g, 45 mmol), after the change of color is
complete 1,1-dibromoethane (1.35 mL, 11 mmol), cyclohex-
anecarboxylic acid 2-methyl-allylic ester (0.93 g, 5.0 mmol).
The reaction mixture was stirred overnight. Standard work-up
followed by column chromatography (Al2O3, pentane) afford-
ed 35 as a colorless oil; yield: 0.70 g (3.6 mmol, 71%). Rf (PE,
1
(PE:Et2O, 98:2, SiO2): 0.3; H NMR (300 MHz, CDCl3): d ˆ
7.93 7.82** (m, 2H), 7.53 7.34** (m, 3H), 5.30 (s, 1H), 5.09*
(s, 1H), 3.33* (dq, J ˆ 7.0 Hz, 7.0 Hz, 1H), 3.26 (dq, J ˆ 6.6 Hz,
6.7 Hz, 1H), 2.64 2.42** (m, 1H), 1.73** (d, J ˆ 17.1 Hz, 2H),
1.57 (s, 3H), 1.51* (s, 3H), 1.46** (d, J ˆ 17.1 Hz, 2H), 1.30 (dd,
J ˆ 12.0 Hz, 5.5 Hz, 1H), 1.23* (dd, J ˆ 12.9 Hz, 5.5 Hz, 1H),
1.10 (d, J ˆ 6.8 Hz, 3H), 1.05* (d, J ˆ 7.0 Hz, 3H), 0.97** (dd,
J ˆ 12.0 Hz, 11.9 Hz, 2H), 0.88* (s, 3H), 0.84 (s, 3H), 0.76 (s,
3H), 0.73 (s, 3H); 13C NMR (75 MHz, CDCl3): d ˆ 204.9,
204.6*, 137.6, 137.6*, 135.1, 134.5*, 133.1, 128.9, 128.7, 128.6*,
123.0, 120.6*, 46.1, 45.2*, 44.6, 44.5*, 40.8, 38.7, 37.0, 37.0*, 32.4,
32.3*, 30.4, 30.3*, 25.6, 25.5*, 24.4, 24.3*, 14.1, 14.0*; HR-MS
1
Al2O3): 0.5; H NMR (400 MHz, C6D6): d ˆ 5.30 (d, J ˆ 0.7; 1
H), 4.99 (d, J ˆ 0.7; 1 H), 4.77 (qd, J ˆ 6.9, 0.7; 1 H), 4.12 (s, 2 H),
2.15 (m, 1 H), 1.81 (dd, J ˆ 6.8, 1.1; 3 H), 1.79 (s, 3 H), 0.90 2.00
(m, 10 H); 13C NMR (100 MHz, C6D6): d ˆ 160.9, 142.7, 111.4,
103.1, 73.6, 41.1, 31.7, 26.8, 26.7, 19.6, 10.8; HRMS (EI, 70 eV):
‡
calcd. for (M ): 194.1671; found: 194.1679; IR (neat): n ˆ 2925,
2855, 1675, 1450, 1375, 1315, 1190, 1170, 1050, 895, 805 cmÀ1.
‡¥
(EI, 70 eV): calcd. for C18H24O (M ): 256.1827; found:
256.1827; anal. calcd for C18H24O (256.2): C 84.32, H 9.43;
found: C 84.45, H, 9.59; IR (film): n ˆ 2950, 1680, 1595, 1365,
1-Cyclohexyl-2,4-dimethylpent-4-en-1-one (36)
1250, 1210, 970, 750, 690, cmÀ1
.
Table 4: Entry 8: According to the General Procedure C:
Cu(OTf)2 (89.2 mg, 250 mmol) in CH2Cl2 (5 mL) at À 658C, 35
(1.007 g, 5.2 mmol). After 3 h the reaction was quenched by
addition of NEt3. Standard work-up followed by column
chromatography (SiO2, PE:Et2O, 98:2) afforded 36 as a
colorless liquid; yield: 751 mg (3.9 mmol, 75%). Rf (PE:Et2O,
96:4, SiO2): 0.3; 1H NMR (400 MHz, CDCl3): d ˆ 4.72 (s, 1H),
4.63 (d, J ˆ 0.7 Hz, 1H), 2.83 (m, 1H), 2.43 (tt, J ˆ 11.0 Hz,
2.9 Hz, 1H), 2.32 (dd, J ˆ 14.0 Hz, 6.4 Hz, 1H), 1.91 (dd, J ˆ
14.0 Hz, 7.9 Hz, 1H), 1.67 (s, 3H), 0.98 (d, J ˆ 6.9 Hz, 3H),
1.80 1.10 (m, 10H); 13C NMR (100 MHz, CDCl3): d ˆ 217.1,
143.0, 112.3, 49.9, 42.4, 41.0, 28.5, 28.3, 25.8, 25.7, 25.6, 22.3,
[1-(2-Methylallyloxy)-propenyl]-cyclohexane (33)
According to the General Procedure A: TiCl4 (20 mL, 1.0 M in
CH2Cl2, 20 mmol) in THF (125 mL), TMEDA (6 mL,
40 mmol), Zn (3.00 g, 45 mmol), after the change of color is
complete 1,1-dibromoethane (1.35 mL, 11 mmol), cyclohex-
anecarboxylic acid allylic ester (0.84 g, 5.0 mmol). The reaction
mixture was stirred overnight. Standard work-up followed by
column chromatography (Al2O3, pentane) afforded 33 as a
colorless oil (single isomer); yield: 0.37 g (2.0 mmol, 41%). Rf
(PE, Al2O3): 0.8; 1H NMR (400 MHz, C6D6): d ˆ 6.00 5.90 (m,
1H), 5.31 5.47 (m, 1H), 5.18 5.07 (m, 1H), 4.74 (qd, J ˆ
6.9 Hz, 1.0 Hz, 1H), 4.16 (dt, J ˆ 5.7 Hz, 1.6 Hz, 2H), 1.67
(dd, J ˆ 6.7 Hz, 1.1 Hz, 3H), 0.80 2.20 (m, 11H); 13C NMR
(100 MHz, C6D6): d ˆ 160.8, 135.4, 115.6, 103.3, 70.7, 41.0, 31.6,
‡
16.4; HRMS (EI, 70 eV): calcd. for (M ): 194.1671; found:
194.1674; IR (neat): n ˆ 2930, 2855, 1705, 1650, 1450, 1375,
1145, 1060, 995, 890 cmÀ1.
‡
26.7, 26.7, 10.8; HRMS (EI, 70 eV): calcd. for (M ): 180.1514;
found: 180.1514; IR (film): n ˆ 2925, 2855, 1710, 1675, 1450,
Acknowledgements
1315, 1170, 1050, 990, 920, cmÀ1.
A. G. thanks the Fonds der Chemischen Industrie for a Dozen-
tenstipendium.
1-Cyclohexyl-2-methylpent-4-en-1-one (34)
Table 4: Entry 7: According to the General Procedure C:
Cu(OTf)2 (18.4 mg, 50 mmol) in CH2Cl2 (1 mL) at À 408C, 33
(194 mg, 1.1 mmol). After 48 h the reaction was quenched by
addition of NEt3. Standard work-up followed by column
chromatography (SiO2, PE:Et2O, 98:2) afforded 34 as a
colorless liquid; yield: 105 mg (0.5 mmol, 54%). Rf (PE:Et2O,
96:4, SiO2): 0.3; 1H NMR (400 MHz, CDCl3): d ˆ 5.58 (dddd,
J ˆ 17.1 Hz, 10.0 Hz, 7.1 Hz, 7.1 Hz, 1H), 4.91 (dd, J ˆ 16.9 Hz,
1.6 Hz, 1H), 4.92 4.85 (m, J ˆ 9.8 Hz, 1H), 2.62 (ddq, J ˆ
6.9 Hz, 6.9 Hz, 6.9 Hz, 1H), 2.38 2.30 (m, 1H), 2.26 (dddt,
References and Notes
[1] For recent reviews see: a) D. Caine, in Comprehensive
Organic Synthesis, (Eds.: B. M. Trost, I. Fleming),
Pergamon, Oxford, 1991, Vol. 3, p. 1 63; b) D. L.
Hughes, in Comprehensive Asymmetric Catalysis, (Eds.:
E. N. Jacobsen, A. Pfaltz, H. Yamamoto), Springer,
Berlin, 1999, Vol. 1, p. 1273.
Adv. Synth. Catal. 2003, 345, 1017 1030
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¹ 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Andreas Gans‰uer et al.
FULL PAPERS
[2] For some recent references see: a) M. Palucki, S. L.
Buchwald, J. Am. Chem. Soc. 1997, 119, 11108; b) B. M.
Trost, G. M. Schroeder, J. Am. Chem. Soc. 1999, 121,
6759; c) M. Braun, F. Laicher, T. Meier, Angew. Chem.
2000, 112, 3637; Angew. Chem. Int. Ed. 2000, 39, 3494.
[3] a) B. M. Trost, Science 1991, 254, 1471; b) B. M. Trost,
Angew. Chem. 1995, 107, 285; Angew. Chem. Int. Ed.
Engl. 1995, 34, 259.
R. Barner, Helv. Chim. Acta 1973, 56, 14; b) K. Non-
oshita, H. Banno, K. Maruoka, H. Yamamoto, J. Am.
Chem. Soc. 1990, 112, 316; c) S. Saito, K. Shimada, H.
Yamamoto, Synlett 1996, 720; d) B. M. Trost, G. M.
Schroeder, J. Am. Chem. Soc. 2000, 122, 3785; e) M.
Hiersemann, L. Abraham, Org. Lett. 2001, 3, 49; f) L.
Abraham, R. Czerwonka, M. Hiersemann, Angew.
Chem. 2001, 113, 4835; Angew. Chem. Int. Ed. 2001, 40,
4700.
[4] M. T. Reetz, Angew. Chem. 1982, 94, 97; Angew. Chem.
Int. Ed. Engl. 1982, 21, 96.
[13] For the deprotonation at the more hindered site of
ketones in the presence of stoichiometric amount of a
bulky aluminum Lewis acid see: S. Saito, M. Ito, H.
Yamamoto, J. Am. Chem. Soc. 1997, 119, 611.
[14] See, for example: R. T. Conlin, R. D. Miller, J. Michl, J.
Am. Chem. Soc. 1979, 101, 7637 and references cited
therein.
[15] a) P. A. Grieco, J. D. Clark, C. T. Jagoe, J. Am. Chem.
Soc. 1991, 113, 5488; b) N. Palini, K. K. Balasubrama-
nian, Tetrahedron Lett. 1993, 34, 5001; c) M. T. Reetz, A.
Gans‰uer, Tetrahedron 1993, 49, 6025.
[5] a) G. W. Kabalka, C. Narayana, N. K. Reddy, Synth.
Commun. 1992, 22, 1793; b) J. F. W. McOmie, M. L.
Watts, D. E. West, Tetrahedron 1968, 24, 2289; c) M. H.
Park, R. Takeda, K. Nakanishi, Tetrahedron Lett. 1987,
28, 3823.
[6] a) H. Frauenrath, Synthesis 1989, 721; b) R. J. Ferrier, S.
Middleton, Chem. Rev. 1993, 93, 2779; c) N. A. Petasis,
S.-P. Lu, J. Am. Chem. Soc. 1995, 117, 6394; d) A. B.
Smith III, P. R. Verhoest, K. P. Minbiole, J. J. Lim, Org.
Lett. 1999, 1, 909.
[7] a) N. A. Petasis, in Transition Metals for Organic Syn-
thesis, (Eds.: M. Beller, C. Bolm), Wiley-VCH: Wein-
heim, 1998, Vol. 1, p. 361; b) S. Otsuka, K. Tani, in
Transition Metals for Organic Synthesis, (Eds.: M. Beller,
C. Bolm), Wiley-VCH: Weinheim, 1998, Vol. 1, p. 147;
c) Y. Okimoto, S. Sakaguchi, Y. Ishii, J. Am. Chem. Soc.
2002, 124, 1590.
[8] For a recent discussion of the stability of cations see: H.
Mayr, B. Kempf, A. R. Ofial, Acc. Chem. Res. 2003, 36,
66 and references cited therein.
[16] For a report on an explosion with 5 M LPDE see: R. A.
Silva, Chem. Eng. News 1992, 70 (52), 2.
[17] S. Winstein, E. Clippinger, A. H. Fainberg, R. Heck,
G. C. Robinson, J. Am. Chem. Soc. 1956, 78, 328.
[18] T. Okazoe, K. Takai, K. Oshima, K. Utimoto, J. Org.
Chem. 1987, 52, 4410.
[19] W. G. Dauben, T. J. Dietsche, J. Org. Chem. 1972, 37,
1212.
[20] P. G. McDougal, J. G. Rico, Tetrahedron Lett. 1984, 25,
5977.
[9] M. P. Sibi, G. R. Cook, in Lewis Acids in Organic
Synthesis, (Ed.: H. Yamamoto), Wiley-VCH: Weinheim,
2001, Vol. 2, p. 543.
[10] a) K. Ishihara, N. Hanaki, M. Funahashi, M. Miyata, H.
Yamamoto, Bull. Chem. Soc. Jpn. 1995, 68, 1721; b) D. J.
Parks, W. E. Piers, J. Am. Chem. Soc. 1996, 118, 9440;
c) W. E. Piers, T. Chivers, T. Chem. Soc. Rev. 1997, 345;
d) K. Ishihara, H. Yamamoto, Eur. J. Org. Chem. 1999,
527.
[21] Y. Kawai, M. Hayashi, Y. Inaba, K. A. Saitou, A. Ohno,
Tetrahedron Lett. 1998, 39, 5225.
[22] G. L. Borosky, A. B. Adriana, R. A. Rossi, J. Org. Chem.
1990, 55, 3705.
[23] S. H. Pines, A. W. Douglas, J. Org. Chem. 1977, 42, 2786.
[24] A. V. Malkov, I. R. Baxendale, D. Dvorak, D. J. Mans-
field, P. Kokovsky, J. Org. Chem. 1999, 64, 2737.
[25] S. P. Kolis, M. E. Kopach, R. Liu, W. D. Harman, J. Org.
Chem. 1997, 62, 130.
[11] a) J. J. Gajewski, Acc. Chem. Res. 1997, 30, 219; b) H. Ito,
T. Taguchi, Chem. Soc. Rev. 1999, 28, 43.
[12] For work on catalytic [3,3]-rearrangements see: a) J.
Borgulya, R. Madeja, P. Fahrni; H.-J. Hansen, H. Schmid,
[26] L. Duhamel, J.-M. Poirier, J. Org. Chem. 1979, 44, 3585.
[27] J. Boivin, E. Fouquet, S. Z. Zard, Tetrahedron Lett. 1990,
31, 85.
1030
¹ 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Adv. Synth. Catal. 2003, 345, 1017 1030