Allylation and vinylation of aryl radicals generated from diazonium salts

Article abstract of DOI:10.1021/jo701717k

(Chemical Equation Presented) Allylation and vinylation of aryl radicals generated from aryl diazonium salts provides rapid and efficient access to chlorinated and brominated derivatives of styrene and allylbenzene. Allyl chlorides were found to be better substrates than bromides due to decreased halogen transfer. Donor- and acceptor-substituted diazonium salts are well tolerated. The products represent important precursors for numerous further transformations.

Full text of DOI:10.1021/jo701717k

Allylation and Vinylation of Aryl Radicals Generated from
Diazonium Salts
Markus R. Heinrich,* Olga Blank, Daniela Ullrich, and Marcel Kirschstein
Lehrstuhl fu¨r Organische Chemie I, Technische UniVersita¨t Mu¨nchen, D-85747 Garching, Germany
markus.heinrich@ch.tum.de
ReceiVed August 8, 2007
Allylation and vinylation of aryl radicals generated from aryl diazonium salts provides rapid and efficient
access to chlorinated and brominated derivatives of styrene and allylbenzene. Allyl chlorides were found
to be better substrates than bromides due to decreased halogen transfer. Donor- and acceptor-substituted
diazonium salts are well tolerated. The products represent important precursors for numerous further
transformations.
Introduction
sulfones,8 cobaloximes,9 silanes,10 halides,11 and phosphine
oxides12 has been investigated as well. Allylation reactions have
been carried out with a wide variety of carbon-centered radicals,
including all types of alkyl and acyl radicals.13 Only reports on
the behavior of aryl radicals, as depicted in Scheme 1 (path A),
remained rare in the literature and thus appear to be more
complicated.14,15 A recent advance in this field was made by
Frejd,16 who achieved allylation of aryl radicals via diazotizative
deamination of acceptor-substituted aromatic amines in the
presence of allyl bromide. Literature precedence for the corre-
Starting from the earliest report by Lewis and Winstein,1
radical addition-fragmentation reactions have become widely
used for the allylation and vinylation of carbon-centered
radicals.2 While major studies were based on trialkyltin-
substituted olefinic substrates,3,4 the role of several other allylic
substituents or functional groups5 such as sulfides,6 sulfoxides,7
* Address correspondence to this author. Phone: +49-89-289-13328. Fax:
+49-89-289-13329.
(1) Lewis, S. N.; Miller, J. J.; Winstein, S. J. Org. Chem. 1972, 37, 1478-
1484.
(7) Barton, D. H. R.; Crich, D. J. Chem. Soc., Perkin Trans. 1 1986,
1613-1619.
(2) For reviews on allylations and vinylations, see: (a) Ramaiah, M.
Tetrahedron 1987, 43, 3541-3676. (b) Curran, D. P. Synthesis 1988, 417-
439. (c) Jasperse, C. P.; Curran, D. P.; Fevig, T. L. Chem. ReV. 1991, 91,
1237-1286.
(3) (a) Kosugi, M.; Kurino, K.; Takayama, K.; Migita, T. J. Organomet.
Chem. 1973, 56, C11-C13. (b) Grignon, J.; Pereyre, M. J. Organomet.
Chem. 1973, 61, C33-C35. (c) Grignon, J.; Servens, C.; Pereyre, M. J.
Organomet. Chem. 1975, 96, 225-235.
(4) For examples demonstrating the versatility of allyltin-based reactions,
see: (a) Keck, G. E.; Yates, J. B. J. Am. Chem. Soc. 1982, 104, 5829-
5831. (b) Keck, G. E.; Enholm, E. J.; Kachensky, D. F. Tetrahedron Lett.
1984, 25, 1867-1870. (c) Keck, G. E.; Enholm, E. J.; Yates, J. B.; Wiley,
M. R. Tetrahedron 1985, 41, 4079-4094. (d) Keck, G. E.; Kachensky, D.
F.; Enholm, E. J. J. Org. Chem. 1985, 50, 4317-4325. (e) Sibi, M. P.;
Chandramouli, S. V. Tetrahedron Lett. 1997, 38, 8929-8932. (f) Sibi, M.;
Porter, N. A. Acc. Chem. Res. 1999, 32, 163-171.
(8) (a) Quiclet-Sire, B.; Zard, S. Z. J. Am. Chem. Soc. 1996, 118, 1209-
1210. (b) Le Guyader, F.; Quiclet-Sire, B.; Seguin, S.; Zard, S. Z. J. Am.
Chem. Soc. 1997, 119, 7410-7411. (c) Quiclet-Sire, B.; Seguin, S.; Zard,
S. Z. Angew. Chem., Int. Ed. 1998, 37, 2864-2866. (d) Blakskjaer, P.;
Pedersen, L.; Skrydstrup, T. J. Chem. Soc., Perkin Trans. 1 2001, 910-
916.
(9) Johnson, M. D. Acc. Chem. Res. 1983, 16, 343-349.
(10) For radical additions to silanes with subsequent fluoride-induced
elimination, see: (a) Porter, N. A.; Zhang, G.; Reed, A. D. Tetrahedron
Lett. 2000, 41, 5773-5777. (b) Chabaud, L.; Landais, Y.; Renaud, P. Org.
Lett. 2002, 4, 4257-4280. (c) Briggs, M. E.; Zard, S. Z. Synlett 2005, 334-
336.
(11) Huval, C. D.; Singleton, D. A. Tetrahedron Lett. 1993, 34, 3041-
3042.
(12) Ouvry, G.; Quiclet-Sire, B.; Zard, S. Z. Angew. Chem., Int. Ed. 2006,
45, 5002-5006.
(13) For overviews, see: (a) Curran, D. P.; Porter, N. A.; Giese, B.,
Eds. Stereochemistry of Radical Reactions: Concepts, Guidelines, and
Synthetic Applications; VCH: Weinheim, Germany, 1996. (b) Giese, B.
Radicals in Organic Synthesis: Formation of Carbon-Carbon Bonds;
Pergamon Press: Oxford, UK, 1986.
(5) For an overview, see: Rosenstein, I. J. In Radicals in Organic
Synthesis; Renaud, P., Sibi, M. P., Eds.; Wiley-VCH: Weinheim, Germany,
2001; Vol. 1, pp 50-71.
(6) (a) Keck, G. E.; Byers, H. J. J. Org. Chem. 1985, 50, 5442-5444.
(b) Yanagisawa, A.; Noritake, Y.; Yamamoto, H. Chem. Lett. 1988, 1899-
1902. (c) Breuilles, P.; Uguen, D. Tetrahedron Lett. 1990, 31, 357-360.
10.1021/jo701717k CCC: $37.00 © 2007 American Chemical Society
Published on Web 11/14/2007
J. Org. Chem. 2007, 72, 9609-9616
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Heinrich et al.
SCHEME 1. Allylation (A), Allenylation (B), and Vinylation
(C) of Aryl Radicals via an Addition-Fragmentation
Mechanism
olefinic chlorides and bromides are summarized in Tables 1-3.
Initial experiments identified several factors that were crucial
to achieving good selectivity and high yields in these reactions.
A key element to achieve selectivity in reactions of aryl radicals
appears to be the use of water as a solvent or at least
cosolvent.21c,22 For the purpose of allylation and vinylation, it
is crucial that the concentration of the aryl diazonium ions in
the reaction mixture is kept at a low level at any time. If this is
not the case, azo coupling reactions occur as undesired side
processes, which are due to the fact that aryl diazonium salts
can act as efficient nitrogen-centered radical scavengers.14,22,23
To suppress these side processes, we adjusted our basic
procedure such that the diazonium salt was added slowly to
the reaction mixture. In our initial experiments, we were pleased
to find that these alterations indeed had the desired effect and
only traces of azo compounds were formed as byproducts.
Another important issue of radical allylation and vinylation
reactions is the nature of the leaving group.24 Unlike most known
radical functionalizations of this type, we chose to perform the
reaction in a non-chain, self-terminating fashion. To facilitate
broader application, we concentrated our efforts on the use of
low-cost, commercially available chlorides and bromides as
olefinic substrates. Since a bromine or chlorine radical would
be formed in the final â-scission step, which possesses itself
significant reactivity, this radical has to be reduced to the
corresponding anion as fast as possible to minimize side
reactions. Regarding the overall results of the allylation and
vinylation experiments, iron(II) appears to be a suitable and
efficient scavenger for the halogen radicals forming in this
process.
Except for the attempts to achieve allenylation, all allylation
and vinylation experiments furnished synthetically useful yields.
A careful examination of the product mixtures revealed that
the reaction, as described here, can be disturbed by hydrogen
abstraction, halogen abstraction, double addition, and intramo-
lecular cyclization. These four types of undesired side reactions
will be discussed in the above-mentioned order. Hydrogen
abstraction occurs when the addition step of the aryl radical to
the substrate is too slow (e.g., sterically hindered olefins) or
when easily abstractable hydrogen atoms are present in the target
molecule. In general, acceptor-substituted aryl radicals more
likely stabilize themselves by hydrogen abstraction than donor-
substituted intermediates as can be seen from the three series
of entries 5-6, 7-9-10, and 20-22.25 The increased amount
of reduced products found with 3-chloro-1-butene (2d) (entries
5 and 6) is most probably caused by the presence of a hydrogen
atom on a chlorine-substituted secondary carbon atom. In all
other substrates, the carbon atom bearing the allylic hydrogen
is primary.26
sponding allenylation and vinylation reactions, which would be
based on a similar radical addition-fragmentation sequence, is
even more difficult to find (Scheme 1, paths B and C).17
In general, the addition of aryl radicals to olefins is well-
known from the classical Meerwein arylation,18 although this
reaction type is mostly employed for a limited group of
activated, electron-deficient olefins.19,20 Nonactivated olefins,
in contrast, were believed to be too unreactive giving rise to
side reactions such as hydrogen abstraction or biaryl couplings.21a
This uncertainty is somehow reflected by the wide range of rate
constants published for the addition step.21 Since our recent
studies on radical functionalizations indicate that the large
number of nonactivated olefins represents an equally suitable
group of substrates for aryl radicals,22 we got inspired to
investigate reactions of aryl radicals with a variety of allylic,
vinylic, and propargylic halides. Herein, we would like to report
our results on allylation and vinylation.
Results and Discussion
The products obtained from the reactions of p-methoxy-,
p-fluoro-, o-carbomethoxy-, p-carbomethoxy-, and o-nitro-
substituted aryl diazonium tetrafluoroborates 1a-e with various
(14) For the first report on allylations of aryl radicals, see: Al Adel, I.;
Salami, B. A.; Levisalles, J.; Rudler, H. Bull. Soc. Chim. Fr. 1976, 934-
938.
(15) For other studies on allylations of aryl radicals, see: (a) Doyle, M.
P.; Siegfried, B.; Elliot, R. C.; Dellaria, J. F., Jr. J. Org. Chem. 1977, 42,
2431-2436. (b) Migita, T.; Kosugi, M.; Takayama, K.; Nakagawa, Y.
Tetrahedron 1973, 29, 51-55. (c) Migita, T.; Nagai, K.; Kosugi, M. Bull.
Chem. Soc. Jpn. 1983, 56, 2480-2484. (d) Yashkina, L. V.; Kopylova, B.
V. Bull. Acad. Sci. USSR, Chem. Sci. 1989, 38, 863-865.
(16) Ek, F.; Axelsson, O.; Wistrand, L.-G.; Frejd, T. J. Org. Chem. 2002,
67, 6376-6381.
(17) (a) Cohen, S. G.; Wolosinski, H. T.; Scheuer, P. J. J. Am. Chem.
Soc. 1950, 72, 3952-3953. (b) Reijnhart, A. F. A. Recl. TraV. Chim. Pays-
Bas 1927, 46, 72-76.
(18) Rondestvedt, C. S. Org. React. 1976, 24, 225-259.
(19) For Meerwein arylations of (nonacceptor substituted) 1,3-butadienes,
see: (a) Taylor, E. C; Strojny, E. J. J. Am. Chem. Soc. 1956, 78, 5104-
5108. (b) Arai, E.; Tokuyama, H.; Linsell, M. S.; Fukuyama, T. Tetrahedron
Lett. 1998, 39, 71-74.
In contrast to bromine abstraction by the aryl radical, the atom
transfer of chlorine was not observed in our study. This
circumstance, undoubtedly related to the increased strength of
(20) For notable exceptions, see: (a) Raucher, S.; Koolpe, G. A. J. Org.
Chem. 1983, 48, 2066-2069. (b) Gorbovoi, P. M.; Kudrik, E. Y.; Grishchuk,
B. D. Russ. J. Gen. Chem. 1998, 68, 1132-1134. (c) Molinaro, C.; Mowat,
J.; Gosselin, F.; O’Shea, P. D.; Marcoux, J.-F.; Angelaud, R.; Davies, I.
W. J. Org. Chem. 2007, 72, 1856-1858. (d) Reference 16.
(21) (a) Galli, C. Chem. ReV. 1988, 88, 765-792. (b) Citterio, A.;
Minisci, F.; Vismara, E. J. Org. Chem. 1982, 47, 81-88. (c) Garden, S. J.;
Avila, D. V.; Beckwith, A. L. J.; Bowry, V. W.; Ingold, K. U.; Lusztyk, J.
J. Org. Chem. 1996, 61, 805-809.
(22) (a) Heinrich, M. R.; Blank, O.; Wo¨lfel, S. Org. Lett. 2006, 8, 3323-
3325. (b) Heinrich, M. R.; Blank, O.; Wetzel, A. J. Org. Chem. 2007, 72,
476-484. (c) Heinrich, M. R.; Wetzel, A.; Kirschstein, M. Org. Lett. 2007,
9, 3833-3835.
(23) Depending on whether the aryl radicals are trapped by the diazonium
salts before or after reacting with the olefin (as alkyl radicals), biaryl azo
compounds or carbodiazenylation products are obtained. See also ref 22.
(24) For relative rate constants of â-fragmentations, see: Wagner, P. J.;
Sedon, J. H.; Lindstrom, M. J. J. Am. Chem. Soc. 1978, 100, 2579-2580.
(25) A reliable determination of the degree of hydrogen abstraction by
p-fluoroaryl radicals was not possible due to the volatility of fluorobenzene.
(26) The absolute rate constants determined for the addition of aryl
radicals to double and triple bonds differ only by a factor of 2 (kdouble )
2.9 × 107 M-1 s-1 and ktriple ) 1.4 × 107 M-1 s-1), see ref 21c. For relative
rates of aryl radical additions to various olefins, see: Bridger, R. F.; Russell,
G. A. J. Am. Chem. Soc. 1963, 85, 3754-3765.
9610 J. Org. Chem., Vol. 72, No. 25, 2007

Allylation and Vinylation of Aryl Radicals
TABLE 1. Allylation of Arenes
a Reactions conducted according to the general procedure. b Structures and yields of products were determined by GC, 1H NMR, and 13C NMR analysis
of the crude product mixture.
the carbon-chlorine bond, made chlorinated substrates become
our preferred substrates. This became even more true since we
saw no negative effect arising from the fragmentation step,
although â-scission has been reported to proceed about 65 times
faster when bromine is released instead of a chlorine radical,24
and Migita15b observed a drop in yield from 63% to 8% when
reacting phenyl radicals with allyl chloride instead of allyl
bromide. Although troubled by halogen transfer, good results
can be obtained from brominated compounds, given that the
addition step to the double or triple bond occurs sufficiently
fast. The competition of the desired addition-fragmentation
pathway and bromine abstraction is reflected in the series of
entries 17, 3, and 12. As the addition to the substrate becomes
more and more effective, bromine transfer is more and more
repressed.21c,26 It is interesting to note that the experiment with
allyl bromide (2b) (entry 3) leads to the same ratio of abstraction
versus addition as previously reported,16 despite the fact that
the reaction conditions applied are totally different.
Double addition is observed when the product formed in the
addition-fragmentation sequence represents a more reactive
olefin than the original substrate itself. Notable examples are
listed in entries 16, 18, and 19. The addition to propargyl
chloride (2h) is not disturbed by halogen abstraction as seen
from the corresponding bromide 2i, nor does hydrogen abstrac-
tion occur. These two findings suggest that the aryl radicals
effectively undergo addition reactions, with the simple but far-
reaching limitation that those which are generated in a later stage
of the reaction more likely attack allene 3n than they would
add to the alkyne 2h. As a result, only a small amount of allene
J. Org. Chem, Vol. 72, No. 25, 2007 9611

Heinrich et al.
TABLE 2. Attempted Allenylation of Arenes
yields together with several side products of higher molecular
weight (entries 24 and 25).
Among the five diazonium salts 1a-e, only the o-nitro-
substituted derivative 1e failed to yield allylation products in
the reaction with 2,3-dichloropropene (2e) (entry 11). In this
special case, the chloroalkyl radical arising from the addition
step preferably attacks the nitro group rather than stabilizing
itself by â-scission (Scheme 2).29,30 Nitroketone (4d) is most
likely formed by subsequent hydrolysis of an intermediate
benzoxacine.31 When 2,3-dibromopropene (2f) is used instead
of the dichloro derivative 2e, the release of bromine in the
fragmentation step is sufficiently fast to overcome the cyclization
on the nitro group.
In summary, we have shown that the intermolecular ally-
lation and vinylation of aryl radicals is a simple, low-cost, and
environmentally benign route to halogenated allylbenzenes
and styrenes, which has so far only marginally been ex-
ploited. Especially the chlorinated and brominated products are
important precursors for a wide range of further transfor-
a Reactions conducted according to the general procedure. b Structures
1
and yields of products were determined by GC, H NMR, and 13C NMR
analysis of the crude product mixture.
3n was detected among a complex mixture of other products
with higher molecular weight.
(31) The structure of nitro compound 4d was confirmed by conversion
to aminothiazole 5 according to the literature: Hardy, K. D.; Harrington,
F. P.; Stachulski, A. V. J. Chem. Soc., Perkin Trans. 1 1984, 1227-1236.
Unlike with propargyl chloride (2h), single and double
addition to 1,2-dichloroethenes 2j and 2k led to simple mixtures
containing chlorostyrene 3o and stilbene 4e as main products.
Only the (E)-configured styrene 3o was isolated from both
attempts, and the final product distribution is somehow effected
by the initial olefin configuration. To get a better insight, we
repeated the experiment with increasing amounts of (E)-1,2-
dichloroethene (2k) (entry 19, 10 and 20 equiv) and found
that the double addition to give the stilbene 4e can successfully
be suppressed. The different ratios of styrene 3o to stilbene 4e
obtained under standard conditions with 6 equiv of substrate
2k can be explained in the following way. As the concentration
of the initial chlorostyrene product 3o increases over the course
of the reaction, it competes with the starting 1,2-dichloro-
ethene 2k for addition of the aryl radical. Since the rate of
addition to (E)-1,2-dichloroethene (2k) is probably faster
than the rate for addition to (Z)-1,2-dichloroethene (2j), more
stilbene 4e is produced in the reaction with the less reactive
(Z)-isomer (entry 18). Similar differences in olefin reactivity
have been found by Giese,27 who reported that the cyclohexyl
radical adds faster to a series of (E)-olefins than to the
corresponding (Z)-olefins. The effectiveness of the initially
undesired aryl radical addition to chlorostyrene 3o becomes
apparent in an independent experiment, in which the dia-
zonium salt 1a and only 2 equiv of styrene 3o furnished 61%
of stilbene 4e (entry 23). Due to the trisubstituted double bond
present in the styrenes 3p-r (entries 20-22), double addition
does not occur in reactions with trichloroethene (2l),21b,28
but it does again complicate the formation of the cinnamic ester
3s. Vinylation experiments with the chloro- and bromoacrylates
2m and 2n as radical acceptors gave the cinnamate 3s in poor
(32) (a) Hanzawa, Y.; Kowase, N.; Taguchi, T. Tetrahedron Lett. 1998,
39, 583-586. (b) Perri, S. T.; Dyke, H. J.; Moore, H. W. J. Org. Chem.
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A.; Valacchi, M. Tetrahedron 2005, 61, 6791-6800. (g) Sahli, S.; Stump,
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D.; Boehm, H.-J. HelV. Chim. Acta 2005, 88, 707-730.
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361-362. (b) Cunico, R. F.; Maity, B. C. Org. Lett. 2003, 5, 4947-4950.
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Epperlein, J. J. Prakt. Chem. 1985, 327, 63-79. (b) Bahr, J. L.; Yang, J.;
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(27) Giese, B. Angew. Chem., Int. Ed. 1983, 22, 753-764.
(28) Attempts to achieve vinylation with tetrachloroethene and diazonium
salt 1a gave nearly quantitative yields of anisole and only traces of
trichlorostyrene although additions of aryl radicals to this substrate have
been reported. See ref 17.
(29) For intramolecular additions of alkyl radicals to nitrobenzenes,
see: Beckwith, A. L. J.; Lawton, D. L. J. Chem. Soc., Perkin Trans. 2
1973, 2134-2137.
(30) The allylation reported by Freyd does tolerate o-nitro substituents
due to the use of allyl bromide, which undergoes faster fragmenation. See
ref 16.
(36) (a) Inoue, A.; Kitagawa, K.; Shinokubo, H.; Oshima, K. J. Org.
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9612 J. Org. Chem., Vol. 72, No. 25, 2007

Allylation and Vinylation of Aryl Radicals
TABLE 3. Vinylation of Arenes
1
a Reactions conducted according to the general procedure (6 equiv of olefinic substrate). b Structures and yields of products were determined by GC, H
NMR, and 13C NMR analysis of the crude product mixture. c Experiment with 10 equiv of substrate 2k. d Experiment with 20 equiv of substrate 2k. e Experiment
with 2 equiv of substrate 3o, standard solvent mixture changed to DMSO-H2O (5:1 v/v) due to the solubility of substrate 3o.
mations. 2-Chloroallyl and 2-bromoallyl derivatives, for ex-
ample, have successfully been employed as precursors
for reactive organotitanium,32a organolithium,32b,c and organo-
zirconium32d intermediates as well as in copper-32e and stannane-
based32f,g cross-coupling reactions. 2-Chlorostyrenes have served
as reactants in carbonylations33a,b and metal-mediated C-C
bond-forming processes.33c-e 2,2-Dichlorostyrenes can be con-
verted to acetylenes,34a,b chloroacetylenes,34c and allenes.34d
Cross-couplings have been achieved via Grignard34e and
Negishi34f,g protocols. In contrast to Friedel-Crafts alkylation
and previously described radical allylations,16 our access is not
limited to either donor- or acceptor-substituted arenes. The
J. Org. Chem, Vol. 72, No. 25, 2007 9613

Heinrich et al.
SCHEME 2. Cyclization versus Fragmentation in
Allylations of o-Nitrophenyl Radicals
4.29 (dd, J ) 0.4 Hz, J ) 1.2 Hz, 2 H), 5.96 (m, 1H), 6.38 (m, 1
H); 13C NMR (CDCl3, 63 MHz) δ 14.1 (CH3), 42.6 (CH2), 61.2
(CH2), 128.4 (CH2), 137.1 (Cq), 165.0 (Cq); GC-MS (EI) m/z (%)
150 (1) [37Cl - M+], 148 (4) [35Cl - M+], 122 (29), 120 (86), 113
(62), 105 (34), 103 (100), 95 (18), 85 (25), 75 (35).
Ethyl (Z)-3-chloropropenoate (2m) was prepared according to
the procedure described in ref 35f: 1H NMR (CDCl3, 250 MHz) δ
1.30 (t, J ) 7.1 Hz, 3 H), 4.23 (q, J ) 7.1 Hz, 2 H), 6.18 (d, J )
8.2 Hz, 1 H), 6.69 (d, J ) 8.2 Hz, 1 H); 13C NMR (CDCl3, 63
MHz) δ 14.1 (CH3), 60.6 (CH2), 121.4 (CH), 132.3 (CH), 163.4
(Cq); GC-MS (EI) m/z (%) 134 (1) [35Cl - M+], 121 (1), 119 (3),
108 (5), 106 (15), 99 (79), 91 (52), 89 (100).
Ethyl (Z)-3-bromopropenoate (2n) was prepared according to
the procedure described in ref 35f: 1H NMR (CDCl3, 250 MHz) δ
1.31 (t, J ) 7.1 Hz, 3 H), 4.23 (q, J ) 7.1 Hz, 2 H), 6.60 (d, J )
8.3 Hz, 1 H), 6.98 (d, J ) 8.3 Hz, 1 H); 13C NMR (CDCl3, 63
MHz) δ 14.1 (CH3), 60.7 (CH2), 121.1 (CH), 124.5 (CH), 163.9
(Cq); GC-MS (EI) m/z (%) 180 (1) [81Br - M+], 178 (1) [79Br -
M+], 152 (20), 150 (20), 135 (98), 133 (100), 107 (21), 105 (22),
99 (63).
reaction also compares well with known organometallic meth-
ods36,38 due to the simple conditions, easily available starting
materials, and insensitivity toward cheap bulk materials of
technical grade purity.
Experimental Section
General Procedure for Allylation and Vinylation. To a mixture
of olefin (6 mmol) and iron(II)-sulfate heptahydrate (2.50 g, 9
mmol) in DMSO-H2O (3 mL, 5:2 v/v) under argon was dropwise
added a solution of the diazonium salt (1 mmol) in DMSO-H2O
(1.5 mL, 5:2 v/v) over a period of 10 min. The resulting mixture
was stirred for 10 min, diluted with H2O (50 mL), and extracted
with Et2O (3 × 30 mL). The combined extracts were washed with
brine and dried over sodium sulfate. After careful evaporation of
the solvents (volatility) the crude products were purified by silica
gel column chromatography.
General Details. All chemicals were used as commercially
available without further purification. The solvent mixture DMSO-
H2O (5:2 v/v) and the olefins were degassed by a stream of argon
prior to use.
General Procedure for the Preparation of the Aryl Diazonium
Tetrafluoroborates 1a-e. To an ice-salt-cooled solution of the
aniline (40.0 mmol) in HBF4 (50%, 14 mL) and water (15 mL)
was dropwise added a precooled solution of NaNO2 (2.90 g, 42.0
mmol) in water (6.5 mL). During the addition, the temperature was
carefully kept below 5 °C and the resulting mixture was left to stir
at 0 °C for 30 min. The diazonium salt was collected by filtration,
washed with Et2O, and extensively dried in vacuo. (Yields: 80-
95%). (Caution: Diazonium salts may decompose violently upon
heating.)
1-Allyl-4-methoxybenzene (3a):36a colorless oil; Rf 0.75 (100%
1
3
Et2O); H NMR (CDCl3, 360 MHz) δ 3.31 (d, J ) 6.8 Hz, 2 H),
3.76 (s, 3 H), 5.00-5.02 (m, 1 H), 5.03-5.07 (m, 1 H), 5.93 (ddd,
J ) 6.8 Hz, J ) 10.2 Hz, J ) 16.9 Hz, 1 H), 6.82 (d, J ) 8.6 Hz,
2 H), 7.08 (d, J ) 8.6 Hz, 2 H); 13C NMR (CDCl3, 90 MHz) δ
39.3 (CH2), 55.2 (CH3), 113.8 (2 × CH), 115.3 (CH2), 129.4 (2 ×
CH), 132.0 (Cq), 137.8 (CH), 157.9 (Cq); GC-MS (EI) m/z (%)
148 (100) [M+], 147 (62), 133 (20), 121 (32), 117 (30), 105 (18),
91 (20), 77 (21).
4-Methoxybenzenediazonium tetrafluoroborate (1a):35a 1H
NMR (CD3CN, 250 MHz) δ 4.05 (s, 3H), 7.34 (d, J ) 9.5 Hz, 2
H), 8.42 (d, J ) 9.5 Hz, 2 H); 13C NMR (CD3CN, 63 MHz) δ 58.4
(CH3), 100.9 (Cq), 118.7 (2 × CH), 136.7 (2 × CH), 171.2 (Cq).
4-Fluorobenzenediazonium tetrafluoroborate (1b):35a 1H NMR
(CD3CN, 250 MHz) δ 7.67 (dd, JHF ) 8.0 Hz, J ) 9.1 Hz, 2 H),
8.59 (dd, JHF ) 4.3 Hz, J ) 9.1 Hz, 2 H); 13C NMR (CD3CN, 63
MHz) δ 111.1 (Cq), 121.0 (d, JCF ) 25.4 Hz, 2 × CH), 137.6 (d,
JCF ) 12.6 Hz, 2 × CH), 170.8 (d, JCF ) 270.5 Hz, Cq); 19F NMR
(CD3CN, 235 MHz) δ -150.2.
1-Allyl-4-fluorobenzene (3b):36b colorless oil; Rf 0.85 (P/EtOAc
) 20:1); 1H NMR (CDCl3, 250 MHz) δ 3.37 (d, J ) 6.7 Hz, 2 H),
5.03-5.08 (m, 1 H), 5.10-5.12 (m, 1 H), 5.96 (tdd, J ) 6.8 Hz,
J ) 13.3 Hz, J ) 15.9 Hz, 1 H), 6.99 (dd, J ) 8.8 Hz, JHF ) 8.8
Hz, 2 H), 7.15 (dd, JHF ) 5.5 Hz, J ) 8.8 Hz, 2 H); 13C NMR
(CDCl3, 63 MHz) δ 39.3 (CH2), 114.1 (d, JCF ) 21.2 Hz, 2 ×
CH), 115.9 (CH2), 129.9 (d, JCF ) 7.7 Hz, 2 × CH), 135.6 (d, JCF
) 3.1 Hz, Cq), 137.3 (CH), 161.4 (d, JCF ) 243.6 Hz, Cq); 19F
NMR (CDCl3, 235 MHz) δ -118.0; GC-MS (EI) m/z (%) 136 (88)
[M+], 135 (100), 133 (26), 115 (23), 109 (51), 83 (12).
2-Methoxycarbonylbenzenediazonium
tetrafluoroborate
(1c): 1H NMR (CD3CN, 250 MHz) δ 4.07 (s, 3 H), 8.17 (ddd, J
) 1.6 Hz, J ) 7.5 Hz, J ) 8.3 Hz, 1 H), 8.33-8.46 (m, 2 H), 8.70
(dd, J ) 1.1 Hz, J ) 8.4 Hz, 1 H); 13C NMR (CD3CN, 63 MHz)
δ 55.1 (CH3), 115.4 (Cq), 132.2 (Cq), 134.1 (CH), 136.3 (CH), 136.4
(CH), 142.8 (CH), 162.5 (Cq).
1-Methoxy-4-(2-methylallyl)benzene (3c):36c colorless oil; Rf
0.90 (100% CH2Cl2); 1H NMR (CDCl3, 250 MHz) δ 1.68 (s, 3 H),
3.27 (s, 2 H), 3.80 (s, 3 H), 4.72 (s, 1 H), 4.80 (s, 1 H), 6.86 (d, J
) 8.6 Hz, 2 H), 7.11 (d, J ) 8.6 Hz, 2 H); 13C NMR (CDCl3, 63
MHz) δ 22.0 (CH3), 43.7 (CH2), 55.2 (CH3), 111.5 (CH2), 113.7
(2 × CH), 129.8 (2 × CH), 131.8 (Cq), 145.5 (Cq), 158.0 (Cq);
GC-MS (EI) m/z (%) 162 (95) [M+], 147 (100), 131 (23), 121 (79),
115 (16), 91 (34), 77 (16).
4-Methoxycarbonylbenzenediazonium tetrafluoroborate (1d):
35b 1H NMR (CD3CN, 250 MHz) δ 3.98 (s, 3 H), 8.41 (d, J ) 9.1
Hz, 2 H), 8.60 (d, J ) 9.1 Hz, 2 H); 13C NMR (CD3CN, 63 MHz)
δ 54.2 (CH3), 119.5 (Cq), 132.8 (2 × CH), 133.8 (2 × CH), 142.0
(Cq), 164.8 (Cq).
2-Nitrobenzenediazonium tetrafluoroborate (1e):35c 1H NMR
(CD3CN, 250 MHz) δ 8.29-8.36 (m, 1 H), 8.48-8.56 (m, 1 H),
8.71 (dd, J ) 1.2 Hz, J ) 8.3 Hz, 1 H), 8.84 (dd, J ) 1.2 Hz, J )
8.1 Hz, 1 H); 13C NMR (CD3CN, 63 MHz) δ 129.5 (CH), 137.8
(CH), 137.9 (CH), 144.2 (CH), two Cq signals not visible.
2-Chloromethylacrylic acid ethyl ester (2g) was prepared
according to procedures described in refs 35d,e: 1H NMR (CDCl3,
250 MHz) δ 1.32 (t, J ) 7.1 Hz, 3 H), 4.26 (q, J ) 7.1 Hz, 2 H),
1-((E)-But-2-enyl)-4-methoxybenzene (3d):36c colorless oil; Rf
0.85 (P/Et2O ) 2:1); 1H NMR (CDCl3, 250 MHz: δ 1.68 (d, J )
6.0 Hz, 3 H), 3.26 (d, J ) 6.0 Hz, 2 H), 3.79 (s, 3 H), 5.44-5.64
(m, 2 H), 6.83 (d, J ) 8.8 Hz, 2 H), 7.10 (d, J ) 8.8 Hz, 2 H); 13
C
NMR (CDCl3, 63 MHz) δ 17.8 (CH3), 38.1 (CH2), 55.2 (CH3),
113.7 (2 × CH), 125.9 (CH), 129.3 (2 × CH), 130.4 (CH), 133.1
(Cq), 157.8 (Cq); GC-MS (EI) m/z (%) 162 (94) [M+], 147 (100),
131 (8), 131 (15), 121 (24), 117 (9), 115 (17), 91 (30), 77 (15).
2-((E)-But-2-enyl)benzoic acid methyl ester (3e): colorless oil;
(38) (a) Barluenga, J.; Moriel, P.; Aznar, F.; Valde´s, C. AdV. Synth. Catal.
2006, 348, 347-353. (b) Braverman, S.; Zafrani, Y. Tetrahedron 1998,
54, 1901-1912. (c) Mun, S.; Lee, J.-E.; Yun, J. Org. Lett. 2006, 8, 4887-
4889.
1
Rf 0.90 (P/Et2O ) 1:2); H NMR (CDCl3, 250 MHz) δ 1.66 (dd,
J ) 1.3 Hz, J ) 6.1 Hz, 3 H), 3.67 (d, J ) 6.3 Hz, 2 H), 3.88 (s,
3 H), 5.41-5.68 (m, 2 H), 7.21-7.31 (m, 2 H), 7.42 (“t”, J ) 7.6
9614 J. Org. Chem., Vol. 72, No. 25, 2007

Allylation and Vinylation of Aryl Radicals
Hz, 1 H), 7.85 (dd, J ) 1.2 Hz, J ) 7.6 Hz, 1 H); 13C NMR (CDCl3,
63 MHz) δ 17.9 (CH3), 37.2 (CH2), 51.9 (CH3), 125.9 (CH), 126.3
(CH), 129.6 (Cq), 129.8 (CH), 130.4 (CH), 130.7 (CH), 131.9 (CH),
142.5 (Cq), 168.2 (Cq); GC-MS (EI) m/z (%) 190 (28) [M+], 161
(75), 159 (26), 158 (100), 157 (25), 148 (14), 133 (26), 131 (35),
130 (25), 129 (62), 128 (29), 115 (51), 91 (31), 77 (11); HRMS
(EI) calcd for C12H14O2 [M+] 190.0988, found 190.0995.
3 H), 4.18 (s, 2 H), 5.39 (dt, J ) 1.5 Hz, J ) 1.5 Hz, 1 H), 5.48
(m, 1 H), 7.31-7.38 (m, 2 H), 7.45-7.52 (m, 1 H), 7.92-7.96
(dd, J ) 1.3 Hz, J ) 8.3 Hz, 1 H); 13C NMR (CDCl3, 63 MHz) δ
45.4 (CH2), 52.0 (CH3), 117.8 (CH2), 127.1 (CH), 129.9 (Cq), 130.9
(CH), 131.5 (CH), 132.1 (CH), 132.2 (Cq), 138.4 (Cq), 167.5 (Cq);
GC-MS (EI) m/z (%) 235 (3) [81Br - M+ - OCH3], 233 (3) [79Br
- M+ - OCH3], 176 (12), 175 (100) [M+ - Br], 160 (6), 143
(28), 131 (6), 116 (23), 115 (38); MS (APCI) m/z (%) 255 [79Br -
2-((Z)-But-2-enyl)benzoic acid methyl ester (3e′): colorless oil;
M+ + H]; HRMS (APCI) calcd for C11H1279BrO2 [79Br - M+
+
1
Rf 0.90 (P/Et2O ) 1:2); H NMR (CDCl3, 250 MHz) δ 1.73 (dd,
H] 255.0015, found 225.0001.
J ) 0.8 Hz, J ) 5.1 Hz, 3 H), 3.76 (d, J ) 5.4 Hz, 2 H), 3.89 (s,
3 H), 5.41-5.68 (m, 2 H), 7.21-7.31 (m, 2 H), 7.42 (“t”, J ) 7.6
Hz, 1 H), 7.85 (dd, J ) 1.2 Hz, J ) 7.6 Hz, 1 H); 13C NMR (CDCl3,
63 MHz) δ 12.9 (CH3), 31.6 (CH2), 51.9 (CH3), 124.9 (CH), 125.8
(CH), 128.9 (CH), 129.7 (Cq), 130.4 (CH), 130.5 (CH), 131.9 (CH),
142.6 (Cq), 169.2 (Cq).
1-(2-Bromoallyl)-2-nitrobenzene (3l): light yellow oil; Rf 0.70
1
(P/EtOAc ) 4:1); H NMR (CDCl3, 250 MHz) δ 4.12 (s, 2 H),
5.53-5.58 (m, 2 H), 7.42-7.48 (m, 2 H), 7.56-7.63 (m, 1 H),
7.96 (d, J ) 8.7 Hz, 1 H); 13C NMR (CDCl3, 63 MHz) δ 44.1
(CH2), 119.5 (CH2), 124.9 (CH), 128.3 (CH), 129.5 (Cq), 131.8
(Cq), 132.3 (CH), 133.1 (CH), 149.1 (Cq); GC-MS (EI) m/z (%)
226 (9) [81Br - M+ - OH], 224 (9) [79Br - M+ - OH], 162 (100)
[M+ - Br], 145 (28), 134 (48), 130 (28), 117 (54), 116 (35), 115
(97), 104 (22), 91 (32), 89 (49), 77 (31); HRMS (EI) calcd for
C9H781BrNO [81Br - M+ - OH] 225.9691, found 225.9692.
2-(4-Methoxybenzyl)acrylic acid ethyl ester (3m):36g colorless
oil; Rf 0.50 (P/EtOAc ) 4:1); 1H NMR (CDCl3, 360 MHz) δ 1.27
(t, J ) 7.1 Hz, 3 H), 3.57 (s, 2 H), 3.79 (s, 3 H), 4.18 (q, J ) 7.1
Hz, 2 H), 5.43 (dt, J ) 1.5 Hz, J ) 1.5 Hz, 1 H), 6.20 (m, 1 H),
6.83 (d, J ) 8.7 Hz, 2 H), 7.11 (d, J ) 8.7 Hz, 2 H); 13C NMR
(CDCl3, 91 MHz) δ 14.2 (CH3), 37.2 (CH2), 55.2 (CH3), 60.7 (CH2),
113.8 (2 × CH), 125.6 (CH2), 130.0 (2 × CH), 130.8 (Cq), 140.8
(Cq), 158.1 (Cq), 167.0 (Cq); GC-MS (EI) m/z (%) 221 (11), 220
(83) [M+], 191 (8), 175 (23), 147 (25), 146 (100), 145 (28), 131
(19), 121 (25), 115 (17), 103 (16), 91 (11).
1-(2-Chloroallyl)-4-methoxybenzene (3f):36d colorless oil; Rf
0.75 (P/EtOAc ) 20:1); 1H NMR (CDCl3, 250 MHz) δ 3.55 (s, 2
H), 3.76 (s, 3 H), 5.09 (dt, J ) 1.3 Hz, J ) 1.3 Hz, 1 H), 5.21 (m,
1 H), 6.85 (d, J ) 8.8 Hz, 2 H), 7.13 (d, J ) 8.8 Hz, 2 H); 13C
NMR (CDCl3, 63 MHz) δ 44.5 (CH2), 55.1 (CH3), 113.1 (CH2),
113.8 (2 × CH), 128.8 (Cq), 130.0 (2 × CH), 142.1 (Cq), 158.5
(Cq); GC-MS (EI) m/z (%) 184 (29) [37Cl - M+], 182 (95) [35Cl -
M+], 167 (12), 147 (60), 131 (14), 121 (100), 115 (23), 103 (22),
91 (15), 77 (22).
1-(2-Chloroallyl)-4-fluorobenzene (3g): colorless oil; Rf 0.85
1
(P/EtOAc ) 20:1); H NMR (CDCl3, 250 MHz) δ 3.61 (s, 2 H),
5.15 (dt, J ) 1.3 Hz, J ) 1.3 Hz, 1 H), 5.27 (m, 1 H), 7.02 (dd, J
) 8.8 Hz, JHF ) 8.8 Hz, 2 H), 7.21 (dd, JHF ) 5.6 Hz, J ) 8.8 Hz,
2 H); 13C NMR (CDCl3, 63 MHz) δ 44.6 (CH2), 113.6 (CH2), 115.3
(d, JCF ) 21.4 Hz, 2 × CH), 130.5 (d, JCF ) 7.6 Hz, 2 × CH),
132.5 (d, JCF ) 3.3 Hz, Cq), 141.4 (Cq), 161.9 (d, JCF ) 245.1 Hz,
Cq); 19F NMR (CDCl3, 235 MHz) δ -116.4; MS (EI) m/z (%) 172
(6) [37Cl - M+], 170 (18) [35Cl - M+], 135 (38), 133 (22), 110
(11), 109 (100), 83 (10); HRMS (EI) calcd for C9H835ClF [35Cl -
M+] 170.0299, found 170.0300.
1-Methoxy-4-propa-1,2-dienylbenzene (3n):37 1H NMR (CDCl3,
250 MHz) δ ) 3.78 (s, 3 H), 5.12 (d, J ) 6.8 Hz, 2 H), 6.13 (t, J
) 6.8 Hz, 1 H), 6.86 (d, J ) 8.8 Hz, 2 H), 7.23 (d, J ) 8.8 Hz, 2
H); 13C NMR (CDCl3, 63 MHz) δ 55.2 (CH3), 78.7 (CH2), 93.3
(CH), 114.1 (2 × CH), 126.0 (Cq), 127.7 (2 × CH), 158.7 (Cq),
209.3 (Cq); GC-MS (EI) m/z (%) 146 (100) [M+], 131 (27), 115
(14), 103 (55), 102 (16), 77 (20).
2-(2-Chloroallyl)benzoic acid methyl ester (3h): colorless oil;
1
Rf 0.80 (P/Et2O ) 1:1); H NMR (CDCl3, 250 MHz) δ 3.88 (s, 3
H), 4.08 (s, 2 H), 4.97 (dt, J ) 1.3 Hz, J ) 1.3 Hz, 1 H), 5.23 (m,
1 H), 7.31-7.37 (m, 2 H), 7.45-7.51 (m, 1 H), 7.94 (dd, J ) 1.5
Hz, J ) 8.0 Hz, 1 H); 13C NMR (CDCl3, 63 MHz) δ 43.1 (CH2),
52.0 (CH3), 113.4 (CH2), 127.0 (CH), 129.8 (Cq), 130.8 (CH), 131.4
(CH), 132.0 (CH), 138.1 (Cq), 141.3 (Cq), 167.5 (Cq); MS (EI) m/z
(%) 175 (100) [M+ - Cl], 143 (35), 116 (11), 115 (32), 91 (9), 89
(8); HRMS (EI) calcd for C11H11O2 [M+ - Cl] 175.0759, found
175.0759; MS (APCI) m/z (%) 211 [35Cl - M+ + H]; HRMS
(APCI) calcd for C11H1235ClO2 [35Cl - M+ + H] 211.0521, found
211.0519.
1-((E)-2-Chlorovinyl)-4-methoxybenzene (3o):38a colorless oil;
Rf 0.50 (P/Et2O ) 20:1); 1H NMR (CDCl3, 250 MHz) δ 3.80 (s, 3
H), 6.49 (d, J ) 13.8 Hz, 1 H), 6.77 (d, J ) 13.8 Hz, 1 H), 6.85
(d, J ) 8.8 Hz, 2 H), 7.22 (d, J ) 8.8 Hz, 2 H); 13C NMR (CDCl3,
63 MHz) δ 55.2 (CH3), 114.2 (2 × CH), 116.3 (CH), 127.3 (2 ×
CH), 127.6 (Cq), 132.6 (CH), 159.5 (Cq); GC-MS (EI) m/z (%)
170 (34) [37Cl - M+], 168 (100) [35Cl - M+] 155 (17), 153 (49),
133 (8), 125 (29), 89 (18).
1-(2,2-Dichlorovinyl)-4-methoxybenzene (3p):38b colorless oil;
Rf 0.90 (100% CH2Cl2); 1H NMR (CDCl3, 250 MHz) δ 3.83 (s, 3
H), 6.79 (s, 1 H), 6.90 (d, J ) 8.8 Hz, 2 H), 7.51 (d, J ) 8.8 Hz,
2 H); 13C NMR (CDCl3, 63 MHz) δ 55.2 (CH3), 113.8 (2 × CH),
118.7 (Cq), 125.9 (Cq), 128.0 (CH), 130.0 (2 × CH), 159.5 (Cq);
GC-MS (EI) m/z (%) 206 (11) [37Cl2 - M+], 204 (63) [37Cl35Cl -
M+], 202 (100) [35Cl2 - M+], 191 (6), 189 (39), 187 (60), 161
(20), 159 (32), 132 (9), 123 (14), 89 (15); HRMS (EI) calcd for
C9H835Cl2O [35Cl2 - M+] 201.9952, found 201.9948.
4-(2-Chloroallyl)benzoic acid methyl ester (3i): colorless oil;
1
Rf 0.70 (P/EtOAc ) 4:1); H NMR (CDCl3, 250 MHz) δ 3.68 (s,
2 H), 3.90 (s, 3 H), 5.17 (dt, J ) 1.3 Hz, J ) 1.3 Hz, 1 H), 5.29
(m, 1 H), 7.31 (d, J ) 8.2 Hz, 2 H), 8.00 (d, J ) 8.2 Hz, 2 H); 13
C
NMR (CDCl3, 63 MHz) δ 45.3 (CH2), 52.0 (CH3), 114.2 (CH2),
128.9 (Cq), 129.0 (2 × CH), 129.8 (2 × CH), 140.5 (Cq), 142.0
(Cq), 166.8 (Cq); MS (EI) m/z (%) 212 (7) [37Cl - M+], 210 (29)
[35Cl - M+], 181 (29), 179 (89), 175 (100), 151 (34), 147 (14),
131 (22), 116 (40), 115 (85), 91 (15), 89 (15); HRMS (EI) calcd
for C11H1135ClO2 [35Cl - M+] 210.0448, found 210.0446.
1-(2,2-Dichlorovinyl)-4-fluorobenzene (3q): colorless oil; Rf
0.90 (100% CH2Cl2); 1H NMR (CDCl3, 250 MHz) δ 6.82 (s, 1 H),
7.06 (dd, J ) 8.8 Hz, JHF ) 8.8 Hz, 2 H), 7.52 (dd, JHF ) 5.4 Hz,
1-(2-Bromoallyl)-4-methoxybenzene (3j): colorless oil; Rf 0.90
J ) 8.8 Hz, 2 H); 13C NMR (CDCl3, 91 MHz) δ 115.5 (d, JCF
)
1
(P/Et2O ) 10:1); H NMR (CDCl3, 250 MHz) δ 3.68 (s, 2 H),
21.7 Hz, 2 × CH), 120.9 (Cq), 127.4 (CH), 129.5 (d, JCF ) 3.4
Hz, Cq), 130.5 (d, JCF ) 8.2 Hz, 2 × CH), 162.4 (d, JCF ) 249.6
Hz, Cq); 19F NMR (CDCl3, 235 MHz) δ -112.4; GC-MS (EI) m/z
(%) 194 (8) [37Cl2 - M+], 192 (62) [37Cl35Cl - M+], 190 [35Cl2 -
M+], 157 (8), 155 (31), 135 (6), 120 (58); HRMS (EI) calcd for
C8H535Cl2F [35Cl2 - M+] 189.9747, found 189.9744.
3.81 (s, 3 H), 5.49 (m, 1 H), 5.55 (dt, J ) 1.5 Hz, J ) 1.5 Hz, 1
H), 6.87 (d, J ) 8.8 Hz, 2 H), 7.15 (d, J ) 8.8 Hz, 2 H); 13C NMR
(CDCl3, 63 MHz) δ 46.9 (CH2), 55.2 (CH3), 113.9 (2 × CH), 117.6
(CH2), 129.3 (Cq), 130.0 (2 × CH), 133.4 (Cq), 158.6 (Cq); MS
(EI) m/z (%) 228 (82) [81Br - M+], 226 (84) [79Br - M+], 188
(18), 186 (16), 147 (100), 121 (95), 115 (23), 103 (16), 91 (26), 78
(16), 77 (25); HRMS (EI) calcd for C11H1179BrO [79Br - M+]
225.9993, found 225.9991.
2-(2,2-Dichlorovinyl)benzoic acid methyl ester (3r): colorless
1
oil; Rf 0.90 (100% CH2Cl2); H NMR (CDCl3, 250 MHz) δ 3.90
(s, 3 H), 7.36-7.42 (m, 1 H), 7.43 (s, 1 H), 7.50-7.59 (m, 2 H),
8.01 (d, J ) 8.3 Hz, 1 H); 13C NMR (CDCl3,91 MHz) δ 52.2 (CH3),
121.7 (Cq), 128.2 (CH), 128.6 (Cq), 128.7 (CH), 130.4 (CH), 130.6
2-(2-Bromoallyl)benzoic acid methyl ester (3k): colorless oil;
1
Rf 0.85 (P/EtOAc ) 1:1); H NMR (CDCl3, 250 MHz) δ 3.89 (s,
J. Org. Chem, Vol. 72, No. 25, 2007 9615

Heinrich et al.
(CH), 132.1 (CH), 135.0 (Cq), 166.7 (Cq); GC-MS (EI) m/z (%)
197 (35) [37Cl - M+ - Cl], 195 (100) [35Cl - M+ - Cl], 152
(15), 153 (49), 136 (12); HRMS (EI) calcd for C10H835ClO2 [35Cl
- M+ - Cl] 195.0207, found 195.020.
164 (98) [M+ - CH2Cl], 137 (19), 136 (100) [M+ - COCH2Cl],
120 (73), 92 (42), 89 (42), 78 (79), 77 (47); MS (ESI) m/z (%) 212
[M+ - H]; HRMS (ESI) calcd for C9H7O3N135Cl [M+ - H]
212.0115, found 212.0131.
(E)-4,4′-Dimethoxystilbene (4e):39c colorless solid; Rf 0.55 (P/
Ethyl (E)-3-(4-methoxyphenyl)-2-propenoate (3s):38c 1H NMR
(CDCl3, 250 MHz) δ 1.32 (t, J ) 7.0 Hz, 3 H), 4.25 (q, J ) 7.0
Hz, 2 H), 6.30 (d, J ) 16.0 Hz, 1 H), 6.89 (d, J ) 8.9 Hz, 2 H),
7.47 (d, J ) 8.9 Hz, 2 H), 7.64 (d, J ) 16.0 Hz, 1 H); 13C NMR
(CDCl3, 63 MHz) δ 14.3 (CH3), 55.3 (CH3), 60.6 (CH2), 114.3 (2
× CH), 115.8 (CH), 127.3 (CH), 129.6 (2 × CH), 144.4 (Cq), 161.5
(Cq), 167.4 (Cq); GC-MS (EI) m/z (%) 206 (73) [M+], 178 (11),
161 (100), 134 (45), 133 (27).
EtOAc ) 10:1); 1H NMR (CDCl3, 360 MHz) δ 3.83 (s, 6 H), 6.89
(d, J ) 8.6 Hz, 4 H), 6.93 (s, 2 H), 7.43 (d, J ) 8.6 Hz, 4 H); 13
C
NMR (CDCl3, 91 MHz) δ 55.3 (2 × CH3), 114.1 (4 × CH), 126.2
(2 × CH), 127.4 (4 × CH), 130.5 (2 × Cq), 159.0 (2 × Cq); GC-
MS (EI) m/z (%) 240 (100) [M+], 225 (53), 165 (19), 153 (14).
4-(2-Nitrobenzyl)thiazol-2-ylamine (5): dark brown oil; Rf 0.40
(CH2Cl2/MeOH ) 20:1); 1H NMR (CDCl3, 360 MHz) δ 4.21 (s, 2
H), 6.09 (s, 1 H), 7.34-7.39 (m, 2 H), 7.49-7.54 (m, 1 H), 7.92
(dd, J ) 1.1 Hz, J ) 8.6 Hz, 1 H); 13C NMR (CDCl3, 91 MHz) δ
34.7 (CH2), 104.8 (CH), 124.8 (CH), 127.6 (CH), 132.3 (CH), 133.0
(CH), 133.9 (Cq), 149.0 (Cq), 167.8 (Cq), one Cq signal missing
due to overlap; MS (ESI) m/z (%) 236 [M+ + H]; HRMS (ESI)
calcd for C10H10O2N332S [M+ + H] 236.0488, found 236.0485.
1-Bromo-4-methoxybenzene (4b):39a colorless oil; 1H NMR
(CDCl3, 250 MHz) δ 3.78 (s, 3 H), 6.79 (d, J ) 9.0 Hz, 2 H), 7.38
(d, J ) 9.0 Hz, 2 H); 13C NMR (CDCl3, 63 MHz) δ 55.4 (CH3),
112.8 (Cq), 115.7 (2 × CH), 132.2 (2 × CH), 158.6 (Cq); GC-MS
(EI) m/z (%) 188 (96) [81Br - M+], 186 (100) [79Br - M+] 173
(45), 171 (46), 145 (37), 143 (38).
1-Chloro-3-(2-nitrophenyl)propan-2-one (4d):39b orange solid;
mp 85-88 °C; Rf 0.75 (CH2Cl2/MeOH ) 50:1); 1H NMR (CDCl3,
500 MHz) δ 4.28 (s, 2 × 2 H), 7.33 (d, J ) 7.5 Hz, 1 H), 7.50
(“t”, J ) 7.5 Hz, 1 H), 7.63 (“t”, J ) 7.5 Hz, 1 H), 8.16 (d, J )
7.5 Hz, 1 H); 13C NMR (CDCl3, 91 MHz) δ 45.1 (CH2), 48.2 (CH2),
125.5 (CH), 128.8 (CH), 129.5 (Cq), 133.8 (CH), 133.9 (CH), 148.2
(Cq), 198.5 (Cq); GC-MS (EI) m/z (%) 167 (3) [35Cl - M+ - NO2],
Acknowledgment. This project was financed by the Fonds
der Chemischen Industrie (Liebig fellowship) and the Deutsche
Forschungsgemeinschaft. We are grateful to the Pra¨sidialfonds
(M.K.) and the Ausbildungszentrum (D.U.) of the Technische
Universita¨t Mu¨nchen. The generous help and support of Prof.
Dr. Thorsten Bach and his group is gratefully acknowledged.
Supporting Information Available: 1H NMR and 13C NMR
spectra for all new compounds and 13C NMR for 3a-m, 3o-r,
4d, and 5. This material is available free of charge via the Internet
at http://pubs.acs.org.
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Org. Biomol. Chem. 2003, 1, 2506-2511. (b) Moore, J. A.; Ahlstrom, D.
H. J. Org. Chem. 1961, 26, 5254-5255. (c) Khartulyari, A. S.; Kapur, M.;
Maier, M. E. Org. Lett. 2006, 8, 5833-5836.
JO701717K
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