Iron-catalyzed allylic C-H amination of substituted 1,3-dienes

Article abstract of DOI:10.1002/ejoc.201301914

A catalytic method for the selective allylic C-H amination of dienes and trienes using arylhydroxylamines has been developed. This iron-catalyzed approach involves the in situ generation of activated nitrosoarenes, which in turn react with dienes or trienes to give the corresponding aminomethyl dienes or trienes as the major products, and hetero-Diels-Alder adducts as minor products. The selectivity depends on the structures of both the catalyst and the substrate. We have also studied substituent effects using p-substituted phenylhydroxylamines. Copyright

Full text of DOI:10.1002/ejoc.201301914

FULL PAPER
DOI: 10.1002/ejoc.201301914
Iron-Catalyzed Allylic C–H Amination of Substituted 1,3-Dienes
Siva Murru[a] and Radhey S. Srivastava*[a]
Keywords: Homogeneous catalysis / Amination / Allylic compounds / Iron / Dienes / Chemoselectivity
A catalytic method for the selective allylic C–H amination of
dienes and trienes using arylhydroxylamines has been devel-
oped. This iron-catalyzed approach involves the in situ gen-
eration of activated nitrosoarenes, which in turn react with
dienes or trienes to give the corresponding aminomethyl
dienes or trienes as the major products, and hetero-Diels–
Alder adducts as minor products. The selectivity depends on
the structures of both the catalyst and the substrate. We have
also studied substituent effects using p-substituted phenyl-
hydroxylamines.
lyzed allylic amination using prefunctionalized dienes,
such as dienyl acetates or halomethyl-1,3-dienes (path
c),[15c,15d,15e] and the reaction of allenes (2 equiv.) with
amines in the presence of Pd catalysts (path d).[15h] Al-
though the reaction of allenes with amines is effective,
bis(dienyl)amines were observed as by-products. Other
methods include the reaction of 2-halomethyl-1,3-dienes
with secondary amines, but this requires the tedious prepa-
ration of 2-halomethyl-1,3-dienes.[15f,15g] The Grignard
cross-coupling reaction of 2-bromo-3-aminopropene and
vinyl bromides is reported to proceed with poor chemose-
lectivity.[15h,15i] In general, all of these methods rely on leav-
ing-group chemistry and multi-step transformations, and
require prefunctionalized substrates.
Introduction
The construction of C–N bonds by C–H amination is
one of the most exciting and important developments in
organic synthesis.[1] The practical utility of such reactions
for the synthesis of complex molecules comes from their
ability to operate with predictable chemo-, stereo-, regio-,
and site selectivity.[2] Classical amination methods range
from nucleophilic displacement of leaving groups to re-
ductive amination of carbonyl compounds.[3] Modern meth-
ods have taken advantage of transition-metal-catalyzed
C–H amination.[4] The main approaches include oxidative
C(sp2)–N coupling,[1a–1e] and benzylic[5] and allylic[1f,6]
C–H amination.
Allylic C–H amination is a very useful process, and it
replaces the classical nucleophilic allylic substitution
method to access allylamines, which are fundamental build-
ing blocks in organic synthesis.[1a] Transition-metal-cata-
lyzed allylic C–H amination occurs via metal–nitrene spe-
cies,[7] via π-allyl species,[8] by dehydrogenative diamin-
ation,[9] or by ene-like reactions.[10–12] Recently, Muniz et
al. reported a metal-free hypervalent-iodine-mediated allylic
amination approach.[13] However, all these methods focused
on the allylic amination of olefins. No method has been
reported for the allylic C–H amination of 1,3-dienes to pre-
pare aminomethyl-1,3-dienes, which are also useful interme-
diates in organic synthesis.[14]
A few methods have been reported for the preparation[15]
of aminomethyl-1,3-dienes using prefunctionalized sub-
strates (Scheme 1). These include ene–yne cross metathesis
using the expensive Grubbs II catalyst (path a),[15a] the ad-
dition of highly reactive organometallic reagents to imines
using 1,4-dibromo-2-butyne (path b),[15b] Pd- or Ir-cata-
Scheme 1. Comparative chart of existing routes and our approach
to aminomethyl 1,3-dienes.
[a] Department of Chemistry, University of Louisiana at Lafayette,
Lafayette, Louisiana 70504, USA
Results and Discussion
E-mail: rss1805@louisiana.edu
In a continuation of our efforts on the development of
transition-metal-catalyzed allylic C–H amination[11] of alk-
enes by nitroso-ene reactions,[10] we were interested in de-
http://chemistry.louisiana.edu
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201301914.
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Iron-Catalyzed Allylic C–H Amination of Substituted 1,3-Dienes
veloping a method for the allylic C–H amination of 1,3- and phenylhydroxylamine (1). For our initial experimenta-
dienes. Although significant progress has been made in the tion we used our standard allylic amination pro-
area of metal-catalyzed allylic amination by nitroso-ene re- cedure,[11b,11c] in which a phenylhydroxylamine (0.25 mmol)
actions using simple olefins,[10–12] no method has been re- solution in dioxane (4 mL) is added slowly using a syringe
ported for the allylic amination of polyenes such as dienes pump to the solution of metal catalyst (0.025 mmol) and
or trienes that yields aminomethyl polyenes selectively. This isoprene (1 mmol) in dioxane (3 mL) over 4 h at 90 °C
is mainly due to the propensity of dienes and trienes to (Scheme 2). To find an efficient catalyst for the selective
react with dienophiles to give hetero-Diels–Alder (HDA) amination reaction, we screened some known allylic amin-
adducts[16] instead of allylamines. Rarely has any effort been ation catalysts, as shown in Table 1.
made to develop selective allylic amination by a nitroso-ene
Copper-based catalysts (Table 1, entries 1 and 2) did not
reaction for the synthesis of useful aminomethyl-1,3-dienes work well. However, good conversions were observed with
(Scheme 2).
most iron catalysts. The iron azobenzene dioxide complex
[11b,11c]
[Fe{PhN(O)N(O)Ph}3][FeCl4]2
(Table 1, entries
8, 10, and 11) was found to be the most efficient catalyst to
yield the allylic amine selectively in good to high yield. We
also examined the reaction with 30 mol-% of FeCl2
(Table 1, entry 5) and FeCl3 (Table 1, entry 7) to compare
their reactivities with that of the Fe azobenzene dioxide
complex (10 mol-%), but poor selectivity for the allylic
amine was observed. In these reactions, both possible iso-
meric HDA adducts were observed, along with varying
amounts of aniline and azoxybenzene, which are common
by-products in amination reactions. The yield improved
slightly when the reaction temperature was lowered to
60 °C, but the selectivity remained almost the same
(Table 1, entry 10). Lowering the temperature further led to
a decrease in the yield and selectivity of formation of the
allylic amine (Table 1, entry 11). Based on these results, we
chose to use Fe azobenzene dioxide as a catalyst at 60 °C
to test the selective allylic amination of other substituted
1,3-dienes.
Scheme 2. Formation of allylic amine and HDA adduct of isoprene.
Our interest in allylic amination using arylhydroxyl-
amines and our experience in this area led us to consider a
metal-catalyzed approach for the selective allylic C–H
amination of simple 1,3-dienes. In our previous study, we
have used 2,3-dimethyl-1,3-butadiene to probe whether the
reaction is an “on-metal” or “off-metal” process, i.e.,
whether free nitrosoarene is absent or present in the reac-
tion mixture. The facts that the allylic amine was formed as
the major product, and that a negligible amount of the
HDA adduct was formed ruled out the presence of free
nitrosoarene in our reactions. In contrast to our observa-
tions, Lau et al. (using a CuCl2 catalyst)[12j] and Ragaini et
al. [using a Ru(Ar-BIAN) catalyst; BIAN = 1,2-bis(aryl-
Next, we evaluated a set of 1,3-dienes with allylic C–H
imino)acenaphthene][12k] detected the formation of HDA groups at the 1, 2, 3, and 4 positions of the diene moiety
adducts as major products along with the allylic amines (Table 2). We observed an intriguing dependence of the
(minor product), which confirms the presence of a free product selectivity on the structure of the substrate. 2,3-
nitrosoarene intermediate.
Dimethyl-1,3-butadiene (b) was relatively less selective than
Furthermore, based on our mechanistic insights into all- isoprene (a), but nevertheless, it reacted well to give allylic
ylic amination, we envisaged that the use of a suitable metal amine 1b in 56% yield. Similar dienes with different substi-
catalyst that operates in an “on-metal” fashion would result tution patterns, i.e., 2,4-dimethyl-1,3-pentadiene (c) and 3-
in the selective allylic amination of 1,3-dienes. Accordingly, methyl-1,3-pentadiene (d) were converted into the corre-
we started our study with a set of copper and iron catalysts sponding allylic amines (i.e., 1c and 1d) in good yields (68
(Table 1) for the reaction of isoprene (a; an allylic 1,3-diene) and 70%, respectively) with high selectivity; Ͻ5% of the
Table 1. Catalyst optimization for the selective allylic amination (AA)of dienes.[a,b]
Entry
Catalyst
Yield [%]
[AA + HDA]
AA
selectivity [%]
1
2
3
4
5
6
7
8
CuCl2·4H2O
35
51
47
69
73
39
45
64
67
71
56
31.4
41.2
63.8
37.6
29.8
64.1
52.3
86.1
67.2
84.5[c]
73.2[d]
Cu(MeCN)4PF6
Fe(Pc)
FeCl2·4H2O
FeCl2·4H2O (30 mol-%)
FeCl3
FeCl3 (30 mol-%)
[Fe{Ph(O)NN(O)Ph}3][FeCl4]2
FeCl2·4H2O/FeCl3 (9:1)
[Fe{Ph(O)NN(O)Ph}3][FeCl4]2
[Fe{Ph(O)NN(O)Ph}3][FeCl4]2
9
10
11
[a] All reactions were performed at 90 °C with 1:4 substrate ratio (PhNHOH: isoprene). [b] Yield and Selectivity calculated based on GC
yields of AA and HDA products. [c] Reaction carried out at 60 °C. [d] Reactions carried out at 40 °C.
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S. Murru, R. S. Srivastava
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Table 2. Substrate dependence of selective allylic amination.[a]
[a] All reactions were performed at 60 °C with 1:4 substrate ratio (PhNHOH: diene/triene). [b] GC yields. [c] Both possible isomers
detected. [d] Ͻ5% HDA adduct observed. [e] Combined yield of both isomeric amines.
HDA adducts were observed. Another set of 1,3-dienes substitution on the 2 or 3 position. Allylic amination of
with methyl substituents at the 1 and 4 positions, i.e., 2,4- myrcene (g) led to two different allylic amine products (1g
hexadiene (e) and 2,5-dimethyl-2,4-hexadiene (f) gave the and 1gЈ), as shown in Table 2. To our surprise, 2,6-dimethyl-
HDA adducts (i.e., 1eЈ and 1fЈ) as the major products. It 2,4,6-octatriene (h) gave an allylic amination product (1h,
seems that the presence of methyl substituents on either the 73%) with exceptional selectivity, with retention of conjuga-
2 or 3 position of the 1,3-diene is a prerequisite for a selec- tion.
tive allylic amination that gives a product in which the con-
jugation of the diene is retained.
We then further extended this method to ortho- and para-
substituted arylhydroxylamines. For these reactions, we
Based on the observed selectivity for allylic amine forma- chose a set of the most selective as well as efficient diene
tion, we classified the 1,3-dienes into two categories: i) 1,3- and triene substrates, i.e., 2,4-dimethyl-1,3-pentadiene (c),
dienes with at least one methyl substitution at either the 2 3-methyl-1,3-pentadiene (d), and 2,6-dimethyl-2,4,6-octatri-
or 3 position (a, b, c, and d); and ii) 1,3-dienes without ene (h) (Table 3). As expected, p-tolylhydroxylamine (2) re-
methyl substitution (allylic position) at either the 2 or 3 acted well with both dienes c and d and triene h to produce
position (e and f). To further investigate the influence of the corresponding allylic amines (i.e., 2c, 2d, and 2h). The
the substrate structure on the outcome of the reaction, we halogenated polyene products generated from halo-substi-
tested two substituted octatrienes (i.e., g and h) that satisfy tuted phenylhydroxylamines 3–6, allow further transforma-
the requirement for selective allylic amination of methyl tions to access complex compounds by metal-catalyzed cou-
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Iron-Catalyzed Allylic C–H Amination of Substituted 1,3-Dienes
pling reactions.[14c] 4-halo phenylhydroxylamines 3–5 re- the skew effect, which says that the abstraction of a hydro-
acted well with 2,4-dimethyl-1,3-pentadiene (c) to give the gen in nitroso-ene reactions is mainly due to the twix (cis
corresponding dienyl allylic amines (i.e., 3c, 4c, and 5c) in and gem) orientation of double bond.[9]
excellent yields. Despite the sterically bulky nature of its
To understand the electronic nature of the transition
ortho substituent, the reaction of 2-iodophenyl hydroxyl- state, rate constants were determined for the reaction of 2,4-
amine (6) with the dienes and triene gave the corresponding dimethyl-1,3-pentadiene (c) with a set of para-substituted
allylic amines (i.e., 6c, 6d, and 6h) with very good selectivi- phenylhydroxylamines, as shown in Figure 1. Electron-with-
ties in high yields up to 76%.
drawing groups (R = Cl, Br) gave increased reaction rates
compared to the unsubstituted compound (R = H),
whereas an electron-rich substituent (R = Me) led to a de-
crease in rate. The Hammett plot indicates the development
of a small negative charge on the nitrogen of the nitroso
intermediate. This observation is consistent with our pre-
vious study on allylic amination using para-substituted
nitrobenzenes.[11g]
Table 3. Selective allylic amination of dienes and triene.[a,b]
Figure 1. Hammett plot (krel vs. σ) for the reaction of diene c with
p-substituted phenylhydroxylamines.
[a] All reactions were performed at 60 °C with a 1:4 substrate ratio
(PhNHOH: diene/triene). [b] Isolated yields. [c] Ͻ5% HDA adduct
observed in GC–MS.
In our previous reports, involvement of the Fe azobenz-
ene dioxide complex and its olefin adducts (on-metal pro-
The selectivity for the allylic amination over the HDA cess) in allylic amination has been strongly implicated on
reaction can be attributed to steric and electronic properties the basis of kinetic and isolation studies of reactions with
of both the catalyst and the substrates. Two findings were different olefins.[11c,11i] For instance, acyclic and cyclic
observed from the results shown in Tables 1–3: i) the selec- diene–iron complexes are stable compounds that have
tive formation of the allylic amines from dienes is catalyst found a wide range of applications in organic synthe-
dependent, and the Fe azobenzene dioxide catalyst is the sis.[17,18] The reactivity of the 1,3-diene system is altered
best catalyst for this reaction; and ii) the selectivity also de- drastically by coordination to the iron complexes. For acy-
pends on the structure of the substrate – there is a require- clic 1,3-dienes, the diene adopts an s-cis conformation to
ment for at least one methyl group at either the 2 or 3 posi- form stable η4 complexes, which requires C–C single-bond
tion of the 1,3-diene for the product of selective allylic rotation.
amination to be formed. The presence of a methyl group at
Considering these facts, we believe that the selective all-
the 2 or 3 position is necessary if the conjugation of the ylic amination approach described in this paper involve the
diene is to be retained after the formation of the allylic formation of intermediate iron η2 complexes with 2,3-sub-
amine (see Tables 2 and 3). This behavior is consistent with stituted dienes. Our observations show that 2,3-unsubsti-
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S. Murru, R. S. Srivastava
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Scheme 3. Plausible reaction pathway for the selective allylic amination of dienes.
tuted dienes preferentially give HDA reaction products, method for the preparation of functionalized polyenes, and
whereas 2,3-substituted 1,3-dienes prefer allylic amination. it may find applications in the polymer and/or related in-
The formation of HDA products might involve formation dustries.
of η4 diene complexes by attaining an s-cis conformation.
However, for 2,3-substituted 1,3-dienes, it is difficult to at-
tain an s-cis conformation, due to possible steric factors
and restricted C–C single bond rotation, so the dienes
Experimental Section
would form η2 complexes. In this case, only one double
bond is activated by the metal, and this might be the origin
of the selectivity for allylic amination over HDA reaction.
Based on these considerations and our previous reports,[11]
we propose a pathway for the selective allylic amination of
1,3-dienes, as shown in Scheme 3. This pathway involves the
Fe-catalyzed oxidation of arylhydroxylamine to activated
azo complex i followed by diene coordination to form either
an η2 or an η4 complex, depending on the structure of the
diene (vide supra). The η2 diene complex would lead to the
formation of dienyl allyl N-hydroxylamine and Fe nitroso
complex ii by path A, whereas the η4 diene complex would
lead to the HDA adduct (path B). Further reduction (deox-
ygenation) of dienyl N-hydroxyallylamine gives the desired
dienyl allylamine with concomitant oxidation of FeII to
FeIII catalytic species iii, and the catalytic cycle continues in
the same way.
General Information: All the reagents were commercial grade, and
were purified according to established procedures. The [Fe{PhN-
(O)N(O)Ph}3][FeCl4]2 catalyst, a dark brown crystalline com-
pound, was prepared following our reported procedure.[11b,11c] The
purity of the recrystallized catalyst was confirmed by comparing
its IR spectrum with that of the original product. Organic extracts
were dried with anhydrous sodium sulfate. Solvents were removed
using a rotary evaporator under reduced pressure. Silica gel (60–
120 mesh size) was used for the column chromatography. Reactions
were monitored by TLC on silica gel 60 F254 (0.25 mm). GC–MS
analysis was carried out using an Agilent GC–MS (7890A-5975C
VL MSD) system. NMR spectra were recorded in CDCl3 with tet-
ramethylsilane (TMS) as the internal standard for 1H (400 MHz)
and for 13C (100 MHz) spectra.
General Procedure for the Selective Allylic Amination of Dienes and
Trienes: A solution of arylhydroxylamine (0.25 mmol) in dioxane
(4 mL) was slowly added by syringe pump over 4 h to a solution
of [Fe{PhN(O)N(O)Ph}3][FeCl4]2 (28 mg, 0.025 mmol) and olefin
(1 mmol) in dioxane (3 mL) at 60 °C. Reactions were allowed to
continue for a further 2 h to ensure complete consumption of the
arylhydroxylamine. After that, the mixture was filtered through Ce-
lite, and the filtrate was concentrated to dryness. The crude product
was purified over a short column of silica gel (hexane/ethyl acetate
eluents) to give the corresponding N-aryl- and aminomethyl-substi-
tuted 1,3-diene/triene, which was analyzed directly by GC–MS and
NMR spectroscopy.
Conclusions
In conclusion, we have developed the first method for
the selective allylic amination of substituted 1,3-dienes. The
selectivity depends on the electronic and steric properties of
both the catalyst and the substrate. We conclude that the
catalyst also plays a key role in accelerating the ene reaction
by hindering the HDA reaction by selective activation of
the diene and the nitrosoarene. A variety of 1,3-dienes and
trienes with an allylic C–H (methyl) group at the 2 or 3
position of the diene moiety were selectively converted into
N-(4-Methyl-2-methylenepent-3-enyl)benzeneamine (1c): Yield 67%.
1H NMR (400 MHz, CDCl3): δ = 1.80 (s, 3 H), 1.81 (s, 3 H), 3.71
(s, 2 H), 3.82 (br. s, 1 H), 4.94 (s, 1 H), 5.22 (s, 1 H), 5.64 (s, 1 H),
6.60 (d, J = 6.0 Hz, 2 H), 6.69 (t, J = 6.8 Hz, 1 H), 7.16 (t, J =
6.8 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 19.9, 27.0,
50.0, 113.1, 113.8, 117.5, 123.9, 129.3, 137.3, 143.2, 148.4 ppm. IR
the respective allylic amines. This is a simple and useful (KBr): ν = 691, 748, 898, 1061, 1179, 1267, 1316, 1375, 1453, 1504,
˜
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Iron-Catalyzed Allylic C–H Amination of Substituted 1,3-Dienes
1600, 1727, 2871, 2929, 2967, 3406 cm–1. GC–MS: m/z = 159.0
(s, 3 H), 1.80 (s, 3 H), 3.68 (s, 2 H), 3.84 (br. s, 1 H), 4.94 (s, 1 H),
5.19 (s, 1 H), 5.61 (s, 1 H), 6.51 (d, J = 8.0 Hz, 2 H), 7.10 (d, J =
8.0 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 19.8, 26.9,
49.9, 113.8, 114.1, 121.9, 123.6, 129.0, 137.4, 142.7, 146.8 ppm. IR
[M]+.
N-(3-Methylenepent-4-en-2-yl)benzeneamine (1d): Yield 69%. 1H
NMR (400 MHz, CDCl3): δ = 1.39 (d, J = 6.8 Hz, 3 H), 3.81 (br.
s, 1 H), 4.20 (q, J = 6.8 Hz, 1 H), 5.09 (s, 1 H), 5.13 (d, J = 11.2 Hz,
1 H), 5.26 (s, 1 H), 5.37 (d, J = 18.0 Hz, 1 H), 6.42 (dd, J = 11.2,
J = 18.0 Hz, 1 H), 6.51 (d, J = 6.4 Hz, 2 H), 6.67 (t, J = 7.2 Hz, 1
H), 7.13 (t, J = 6.4 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 22.0, 49.4, 113.0, 114.3, 122.3, 125.5, 129.1, 137.0, 144.0,
(KBr): ν = 811, 901, 1071, 1122, 1178, 1318, 1497, 1595, 2855,
˜
2911, 2928, 2968, 3426 cm–1. GC–MS: m/z = 221.0 [M]+.
4-Bromo-N-(4-methyl-2-methylenepent-3-enyl)benzeneamine (4c):
1
Yield 83%, colorless gum. H NMR (400 MHz, CDCl3): δ = 1.79
(s, 3 H), 1.82 (s, 3 H), 3.69 (s, 2 H), 3.89 (br. s, 1 H), 4.95 (s, 1 H),
5.19 (d, J = 1.6 Hz, 1 H), 5.62 (s, 1 H), 6.47 (d, J = 8.8 Hz, 2 H),
7.23 (d, J = 8.8 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 19.7, 26.8, 49.7, 108.8, 113.7, 114.4, 123.4, 131.8, 137.4, 142.5,
147.9 ppm. IR (KBr): ν = 684, 763, 906, 1024, 1071, 1162, 1275,
˜
1299, 1437, 1482, 1602, 1729, 2853, 2924, 3066, 3407 cm–1. GC–
MS: m/z = 173.1 [M]+.
147.1 ppm. IR (KBr): ν = 811, 901, 1000, 1071, 1122, 1178, 1268,
˜
3,6-Dihydro-3,6-dimethyl-2-phenyl-2H-1,2-oxazine (1eЈ): Yield 52%.
1H NMR (400 MHz, CDCl3): δ = 1.10 (d, J = 6.4 Hz, 3 H), 1.30
(d, J = 6.8 Hz, 3 H), 4.14 (q, J = 6.4 Hz, 1 H), 4.67 (q, J = 6.8 Hz,
1 H), 5.77 (d, J = 10.0 Hz, 1 H), 5.92 (m, 1 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 14.6, 19.1, 54.5, 73.7, 115.7, 121.2, 129.0,
1318, 1446, 1497, 1595, 2856, 2911, 2968, 3426 cm–1. GC–MS: m/z
= 265.1 [M]+.
4-Iodo-N-(4-methyl-2-methylenepent-3-enyl)benzeneamine (5c):
1
Yield 78%, colorless gum. H NMR (400 MHz, CDCl3): δ = 1.78
129.2, 130.2, 148.9 ppm. IR (KBr): ν = 687, 751, 906, 1025, 1082,
˜
(s, 3 H), 1.80 (s, 3 H), 3.68 (d, J = 4.8 Hz, 2 H), 3.87 (br. s, 1 H),
4.94 (s, 1 H), 5.18 (d, J = 1.2 Hz, 1 H), 5.61 (s, 1 H), 6.38 (d, J =
8.8 Hz, 2 H), 7.39 (d, J = 9.2 Hz, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 19.9, 27.0, 49.7, 78.0, 113.9, 115.3, 123.6, 137.6, 137.8,
1215, 1275, 1328, 1437, 1490, 1506, 1602, 2839, 2928, 3057 cm–1.
GC–MS: m/z = 189.0 [M]+.
N-[(E)-7-Methyl-3-methyleneocta-4,6-dien-2-yl]benzeneamine (1h):
1
142.6, 147.8 ppm. IR (KBr): ν = 809, 899, 1059, 1122, 1181, 1268,
˜
Yield 73%. H NMR (400 MHz, CDCl3): δ = 1.41 (d, J = 6.4 Hz,
1293, 1318, 1446, 1495, 1591, 2926, 2965, 3424 cm–1. GC–MS: m/z
3 H), 1.78 (s, 3 H), 1.82 (s, 3 H), 3.81 (br. s, 1 H), 4.20 (q, J =
6.4 Hz, 1 H), 5.05 (s, 1 H), 5.17 (s, 1 H), 5.90 (d, J = 11.2 Hz, 1
H), 6.18 (d, J = 15.6 Hz, 1 H), 6.52 (d, J = 7.6 Hz, 2 H), 6.60 (dd,
J = 16.0 Hz, J = 11.2 Hz, 1 H), 6.66 (t, J = 6.8 Hz, 1 H), 7.13 (t,
J = 7.6 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 18.7,
22.4, 26.4, 50.3, 112.8, 113.2, 117.3, 125.3, 125.8, 129.3, 130.1,
= 312.9 [M]+.
2-Iodo-N-(4-methyl-2-methylenepent-3-enyl)benzeneamine (6c):
Yield 67%. 1H NMR (400 MHz, CDCl3): δ = 1.79 (s, 3 H), 1.82
(s, 3 H), 3.77 (s, 2 H), 4.41 (br. s, 1 H), 4.96 (s, 1 H), 5.21 (s, 1 H),
5.65 (s, 1 H), 6.43 (t, J = 7.6 Hz, 1 H), 6.51 (d, J = 8.0 Hz, 1 H),
7.17 (t, J = 8.0 Hz, 1 H), 7.65 (d, J = 8.0 Hz, 1 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 19.8, 26.9, 49.9, 85.5, 111.3, 113.8, 118.8,
136.8, 147.4, 148.3 ppm. IR (KBr): ν = 692, 750, 957, 1030, 1076,
˜
1257, 1316, 1375, 1453, 1504, 1600, 1727, 2871, 2929, 2967,
3406 cm–1. GC–MS: m/z = 227.3 [M]+.
123.6, 129.5, 137.7, 139.1, 142.4, 147.3 ppm. IR (KBr): ν = 754,
˜
1016, 1074, 1289, 1378, 1434, 1465, 1511, 1586, 1721, 2929, 2982,
4-Methyl-N-(4-methyl-2-methylenepent-3-enyl)benzeneamine (2c):
Yield 65%. 1H NMR (400 MHz, CDCl3): δ = 1.81 (s, 6 H), 2.43
(s, 3 H), 3.86 (s, 2 H), 4.94 (s, 1 H), 5.30 (s, 1 H), 5.65 (s, 1 H),
6.63 (d, J = 8.0 Hz, 2 H), 7.05 (d, J = 8.0 Hz, 2 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 19.9, 20.5, 26.9, 50.2, 113.2, 122.3, 124.0,
3365 cm–1. GC–MS: m/z = 313.0 [M]+.
2-Iodo-N-(3-methylenepent-4-en-2-yl)benzeneamine (6d): Yield 72%.
1H NMR (400 MHz, CDCl3): δ = 1.48 (d, J = 6.8 Hz, 3 H), 4.22
(t, J = 6.8 Hz, 1 H), 4.34 (br. s, 1 H), 5.07 (s, 1 H), 5.15 (d, J =
11.6 Hz, 1 H), 5.17 (s, 1 H), 5.36 (d, J = 18.0 Hz, 1 H), 6.33 (d, J
= 8.0 Hz, 1 H), 6.38–6.46 (m, 2 H), 7.12 (t, J = 8.0 Hz, 1 H), 7.63
(d, J = 8.0 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 22.3,
50.1, 85.5, 111.8, 113.8, 114.8, 118.7, 129.4, 137.1, 139.0, 146.2,
126.6, 129.8, 137.0, 143.3, 146.1 ppm. IR (KBr): ν = 806, 1018,
˜
1261, 1518, 1616, 1681, 1752, 2923, 2965, 3349 cm–1. GC–MS: m/z
= 200.9 [M]+.
4-Methyl-N-(3-methylenepent-4-en-2-yl)benzeneamine (2d): Yield
1
147.4 ppm. IR (KBr): ν = 739, 902, 1004, 1171, 1279, 1319, 1375,
˜
63%. H NMR (400 MHz, CDCl3): δ = 1.38 (d, J = 6.4 Hz, 3 H),
1425, 1450, 1506, 1590, 2927, 2965, 3073, 3396 cm–1. GC–MS: m/z
2.21 (s, 3 H), 3.68 (br. s, 1 H), 4.17 (q, J = 6.4 Hz, 1 H), 5.07 (s, 1
H), 5.13 (d, J = 11.2 Hz, 1 H), 5.22 (s, 1 H), 5.37 (d, J = 17.6 Hz,
1 H), 6.43 (d, J = 8.0 Hz, 2 H), 6.95 (d, J = 8.0 Hz, 2 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 20.5, 22.2, 49.7, 113.3, 114.4, 122.3,
= 299.1 [M]+.
2-Iodo-N-[(E)-7-methyl-3-methyleneocta-4,6-dien-2-yl]benzeneamine
(6h): Yield 76%. 1H NMR (400 MHz, CDCl3): δ = 1.49 (d, J =
6.4 Hz, 3 H), 1.80 (s, 3 H), 1.83 (s, 3 H), 4.22 (br. s, 1 H), 4.35 (br.
s, 1 H), 5.03 (s, 1 H), 5.08 (s, 1 H), 5.88 (d, J = 10.8 Hz, 1 H), 6.16
(d, J = 15.6 Hz, 1 H), 6.34–6.41 (m, 2 H), 6.60 (dd, J = 15.6, J =
10.8 Hz, 1 H), 7.11 (t, J = 7.6 Hz, 1 H), 7.62 (d, J = 7.6 Hz, 1 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 18.8, 22.6, 26.4, 50.9, 85.5,
112.0, 113.1, 118.7, 125.4, 125.8, 129.5, 129.9, 137.0, 139.0, 146.3,
126.4, 129.8, 137.3, 145.0, 148.3 ppm. IR (KBr): ν = 759, 902, 1068,
˜
1165, 1206, 1274, 1302, 1439, 1598, 2847, 2933, 3057, 3402 cm–1.
GC–MS: m/z = 187.0 [M]+.
4-Methyl-N-[(E)-7-methyl-3-methyleneocta-4,6-dien-2-yl]benzene-
1
amine (2h): Yield 71%. H NMR (400 MHz, CDCl3): δ = 1.39 (d,
J = 6.8 Hz, 3 H), 1.77 (s, 3 H), 1.81 (s, 3 H), 2.20 (s, 3 H), 3.68 (br.
s, 1 H), 4.16 (q, J = 6.8 Hz, 1 H), 5.04 (s, 1 H), 5.15 (s, 1 H), 5.89
(d, J = 10.8 Hz, 1 H), 6.16 (d, J = 15.6 Hz, 1 H), 6.43 (d, J =
8.0 Hz, 2 H), 6.60 (dd, J = 15.6 Hz, J = 10.8 Hz, 1 H), 6.93 (d, J
= 8.0 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 18.7, 20.6,
22.5, 26.4, 50.5, 112.7, 113.4, 115.9, 125.2, 125.8, 129.8, 130.2,
147.6 ppm. IR (KBr): ν = 742, 799, 870, 1018, 1260, 1314, 1376,
˜
1454, 1505, 1588, 2964, 3395 cm–1. GC–MS: m/z = 352.9 [M]+.
Supporting Information (see footnote on the first page of this arti-
1
cle): Copies of the H and 13C NMR spectra are provided.
136.7, 145.1, 148.5 ppm. IR (KBr): ν = 705, 807, 890, 1038, 1095,
˜
1259, 1298, 1375, 1447, 1518, 1617, 2868, 2914, 2965, 3409 cm–1.
Acknowledgments
GC–MS: m/z = 241.3 [M]+.
4-Chloro-N-(4-methyl-2-methylenepent-3-enyl)benzeneamine (3c):
Yield 80%, colorless gum. H NMR (400 MHz, CDCl3): δ = 1.78 Board of Regents [grant number LEQSF(2013-16)-RD-B-06].
The authors are grateful for financial support from the Louisiana
1
Eur. J. Org. Chem. 2014, 2174–2181
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2179

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Received: December 23, 2013
Published Online: February 3, 2014
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2181