Fe(II)-catalyzed imidation of allyl sulfides and subsequent [2,3]- sigmatropic rearrangement. Preparation of α-branched N-tert-butyloxycarbonyl (Boc)-protected N-allylamines

Article abstract of DOI:10.1021/jo991569p

Allyl aryl sulfides 1 and 5 were shown to undergo an imidation/[2,3]- sigmatropic rearrangement reaction upon treatment with N-tert- butyloxycarbonyl azide (BocN₃) and catalytic amounts of FeCl₂ in CH₂Cl₂. The N-Boc-protected N-allyl sulfenamides 3 and 21 were obtained in yields between 48 and 75% (12 examples). Whereas the reaction is well suited for the transformation of α-unbranched sulfides to α-branched sulfenamides, the enantiomerically pure α-branched sulfides 10 and 13 reacted sluggishly. The corresponding sulfenamides 22 and 23 were obtained in only moderate enantiomeric excess (36-39% ee). A reaction mechanism is proposed that postulates the intermediacy of an N-Boc-substituted Fe(IV)-nitrene complex 14 acting as the imidation reagent in the catalytic cycle. Possible side reactions are discussed. The benzenesulfenamides 3 were further converted into N-Boc-N-allylamines 4 by removal of the phenylsulfanyl group. Bu₃SnH in benzene was found to be the reagent of choice for the deprotection of α- branched amines that bear a secondary allyl substituent (five examples, 71- 93% yield). This method failed for the α-branched amines 3i-k with a tertiary allyl substituent. The phenylsulfanyl group was finally removed with P(OEt)₃/NEt₃ in CH₂Cl₂ (three examples, 43-62% yield).

Full text of DOI:10.1021/jo991569p

2358
J . Org. Chem. 2000, 65, 2358-2367
F e(II)-Ca ta lyzed Im id a tion of Allyl Su lfid es a n d Su bsequ en t
[2,3]-Sigm a tr op ic Rea r r a n gem en t. P r ep a r a tion of r-Br a n ch ed
N-ter t-Bu tyloxyca r bon yl (Boc)-P r otected N-Allyla m in es
Thorsten Bach* and Christina Ko¨rber
Fachbereich Chemie der Philipps-Universita¨t Marburg, D-35032 Marburg, Germany
Received October 8, 1999
Allyl aryl sulfides 1 and 5 were shown to undergo an imidation/[2,3]-sigmatropic rearrangement
reaction upon treatment with N-tert-butyloxycarbonyl azide (BocN3) and catalytic amounts of FeCl2
in CH2Cl2. The N-Boc-protected N-allyl sulfenamides 3 and 21 were obtained in yields between 48
and 75% (12 examples). Whereas the reaction is well suited for the transformation of R-unbranched
sulfides to R-branched sulfenamides, the enantiomerically pure R-branched sulfides 10 and 13
reacted sluggishly. The corresponding sulfenamides 22 and 23 were obtained in only moderate
enantiomeric excess (36-39% ee). A reaction mechanism is proposed that postulates the
intermediacy of an N-Boc-substituted Fe(IV)-nitrene complex 14 acting as the imidation reagent
in the catalytic cycle. Possible side reactions are discussed. The benzenesulfenamides 3 were further
converted into N-Boc-N-allylamines 4 by removal of the phenylsulfanyl group. Bu3SnH in benzene
was found to be the reagent of choice for the deprotection of R-branched amines that bear a secondary
allyl substituent (five examples, 71-93% yield). This method failed for the R-branched amines 3i-k
with a tertiary allyl substituent. The phenylsulfanyl group was finally removed with P(OEt)3/NEt3
in CH2Cl2 (three examples, 43-62% yield).
In tr od u ction
reagent with a more labile protective group is conse-
quently a topic of current interest.7 Research in our group
has centered on the use of N-tert-butyloxycarbonyl azide
(BocN3) as the source of an N-Boc-protected nitrene
fragment. Indeed, we could show that the imidation of
sulfoxides and sulfides with this reagent was possible if
FeCl2 was employed as a promoter.8 For the imidation
of sulfides to the corresponding N-Boc-protected sulfimines,
substoichiometric amounts of FeCl2 (10-20 mol %) were
sufficient and the reaction was ligand-accelerated in CH2-
Cl2 at 0 °C. As expected, the removal of the protective
group proceeded readily. In this paper, we would like to
report on an extension of the sulfide imidation methodol-
ogy based on an imidation/[2,3]-sigmatropic rearrange-
ment sequence. If applied to allyl sulfides 1, the reagent
combination BocN3/FeCl2 yielded intermediate sulfimides
2 that rearranged further to N-allylamines 3. The
nitrogen atom of these amines is protected by a Boc and
a phenylsulfanyl group (Scheme 1), each of which can be
readily removed. In this study, we have looked into the
selective removal of the phenylsulfanyl group, which
yielded the title compounds 4. The method appears to
be particularly useful for the synthesis of R-branched
N-Boc-N-allylamines.
In recent years, oxygen-transfer reactions to nucleo-
philes, e.g., to alkenes1 and sulfides,2 have been developed
into a generally applicable synthetic method. Enantiose-
lective variants have been found that allow the prepara-
tion of a variety of epoxides3 and sulfoxides4 with
significant enantiomeric excess. Analogous nitrogen-
transfer reactions have been studied less frequently, and
the available methodology for the latter reaction type is
limited as compared to what is known in the area of
oxygen transfer. Still, there have been major improve-
ments concerning in particular the transfer of a “NTs”
(Ts ) tosyl) fragment from PhIdNTs or chloramine-T to
nucleophiles.5,6 Despite the excellent yields and stereo-
selectivities occasionally obtained with these reagents,
the somewhat awkward removal of the tosyl group in the
product is considered to be a serious drawback. Replacing
the tosyl group at the nitrogen atom of the transfer
(1) Reviews: (a) Rao, K. A. In Comprehensive Organic Synthesis;
Trost, B., Fleming, I., Eds.; Pergamon: Oxford, 1991; Vol. 7, p 357. (b)
Barto´k, M.; La´ng, K. L. In The Chemistry of Heterocyclic Compounds;
Weissberger, A., Taylor, E. C., Series Eds.; Hassner, A., Ed.; Wiley:
New York 1985; Vol. 42, Part 3, p 15.
(2) Review: Kresze, G. In Methoden der Organischen Chemie
(Houben-Weyl) 4te Aufl., Klamann, D., Ed.; Thieme: Stuttgart 1985;
Vol. E 11, Part 1, p 702.
(3) Reviews: (a) J ohnson, R. A.; Sharpless, K. B. In Catalytic
Asymmetric Synthesis; Ojima, I., Ed.; VCH: Weinheim, 1991; p 103.
(b) J acobsen, E. N. In Catalytic Asymmetric Synthesis; Ojima, I., Ed.;
VCH: Weinheim, 1991; p 159.
(4) Review: Kagan, H. B. In Catalytic Asymmetric Synthesis; Ojima,
I., Ed.; VCH: Weinheim, 1991; p 203.
The direct preparation of N-Boc-protected N-allyl-
amines from allyl sulfides has not yet been reported.
However, there has been a study on the Pd(II)-catalyzed
nitrene transfer from ethoxycarbonyl azide to allyl sul-
fides.9 In addition, the [2,3]-sigmatropic rearrangement
(5) Transfer to alkenes: (a) Evans, D. A.; Faul, M. M.; Bilodeau, M.
T. J . Am. Chem. Soc. 1994, 116, 2742. (b) Li, Z.; Quan, R. W.; J acobsen,
E. N. J . Am. Chem. Soc. 1995, 117, 5889. (c) Review: Mu¨ller, P. In
Advances in Catalytic Processes Vol. 2, Asymmetric Catalysis; Doyle,
M. P., Ed.); J AI, Greenwich 1997; p 131.
(6) Transfer to sulfides: (a) Takada, H.; Nishibayashi, Y.; Ohe, K.;
Uemura,S. J . Chem. Soc., Chem. Commun. 1996, 931. (b) Takada, H.;
Nishibayashi, Y.; Ohe, K.; Uemura, S.; Baird, S. C. P.; Sparey, T. J .;
Taylor, P. C. J . Org. Chem. 1997, 62, 6512.
(7) For some recent examples: (a) Dauban, P.; Dodd, R. H. J . Org.
Chem. 1999, 64, 5304. (b) Tomooka, C. S.; LeCloux, D. D.; Sasaki, H.;
Carreira, E. M. Org. Lett. 1999, 1, 149. (c) J eong, J . U.; Tao, B.;
Sagasser, I.; Henniges, H.; Sharpless, K. B. J . Am. Chem. Soc. 1998,
120, 6844.
(8) (a) Bach, T.; Ko¨rber, C. Tetrahedron Lett. 1998, 39, 5015. (b)
Bach, T.; Ko¨rber, C. Eur. J . Org. Chem. 1999, 1033.
(9) Migita, T.; Hongoh, K.; Naka, H.; Nakaido, S.; Kosugi, M. Bull.
Chem. Soc. J pn. 1988, 61, 931.
10.1021/jo991569p CCC: $19.00 © 2000 American Chemical Society
Published on Web 03/28/2000

Fe(II)-Catalyzed Imidation of Allyl Sulfides
J . Org. Chem., Vol. 65, No. 8, 2000 2359
Ta ble 1. Syn th esis of Allyl Su lfid es 1 by Nu cleop h ilic
Su bstitu tion
Sch em e 1
entry
X
base
solvent
product
yielda (%)
1
2
3
4
5
6
Br
Br
Br
Br
Cl
Br
NEt3
NaOEt
NEt3
NaOEt
NaOEt
NEt3
THF
1a
1c
1d
1e
1i
95b
88
82
EtOH
Et2O
EtOH
EtOH
THF
94
88
1k
quantc
Yield of isolated product. E/Z ratio: 86/14. c E/Z ratio: 80/
a
b
20.
solvent16 or with NaOEt as the base in EtOH as the
solvent.17 Using the NaOEt procedure, the known sulfides
1c,17 1e,18 and 1i19 were synthesized as depicted in eq 1
and Table 1 (entries 2, 4, and 5).
of other allyl sulfimines is known. Some examples10 of
related, previously reported conversions of allyl sulfides
to N-allylamines include the reaction with chloramine-
T,11 with PhIdNTs in the presence of a Cu(I)-salt,6 with
O-mesitylenesulfonylhydroxylamine (MSH),12 with N-
aminophthalimide/Pb(OAc)4,13 and with ethyl N-[(tri-
fluoromethanesulfonyl)oxy]carbamate.14 The preparation
of N-allylamines from the corresponding allyl selenides
by imidation/[2,3]-sigmatropic rearrangement has been
intensively studied.15
In addition, the anisyl (An ) p-methoxyphenyl) ana-
logue 520 of compound 1a was prepared by the very
same method starting from p-methoxythiophenol (eq 2).
Resu lts a n d Discu ssion
P r ep a r a tion of th e Allyl Su lfid es. The structures
of the allyl phenyl sulfides 1 employed in this study are
shown below.
Reduction of ester 1d with Dibal-H in hexane yielded the
alcohol 1b21 in 46% yield. The nucleophilic substitution
reactions of crotyl bromide, of methyl 4-bromocrotonate,
and of 1-benzyloxy-4-bromo-2-methyl-2-butene22 to yield
sulfides 1a ,16 1d ,23 and 1k were carried out with NEt3
as the base (entries 1, 3, and 6 in Table 1).
Allyl phenyl sulfides with an alkyl group R2 at the
internal carbon atom of the double bond were favorably
prepared from the corresponding ketones 6 by a modifi-
cation of a previously reported procedure.24 Accordingly,
R-lithiated thioanisol was generated from thioanisol by
treatment with n-butyllithium in THF (0 °C f rt).25
Subsequent addition of the ketones 6 yielded the tertiary
alcohols 7. These alcohols were not further purified but
directly taken into the next step. They underwent a clean
elimination to the target compounds 1f,26 1g,27 1h , and
1j28 upon heating with p-toluenesulfonic acid (TsOH) in
benzene (eq 3). The sulfides 1g and 1h were obtained as
a mixture of E/Z isomers. The elimination 7h f 1h was
not fully regioselective and led to the formation of the
Most of these allyl sulfides were prepared from the
corresponding halides by nucleophilic substitution with
thiophenolate. The displacement reaction was either
conducted with NEt3 as the base in THF or ether as the
(16) (a) Babler, J . H.; Haack, R. A. J . Org. Chem. 1982, 47, 4801.
(b) Birkofer, L.; Hartwig, I. Chem. Ber. 1954, 87, 1189.
(17) Briscoe, P. A.; Challenger, F.; Duckworth, P. S. J . Chem. Soc.
1956, 1755.
(18) Pasto, D. J .; Warren, S. E.; Morrison, M. A. J . Org. Chem. 1981,
46, 2837.
(10) For further references on the preparation of N-allylamines,
see: (a) Xu, Q.; Dittmer, D. C. Tetrahedron Lett. 1999, 40, 2255. (b)
J ohannson, M.; J ørgensen, K. A. Chem. Rev. 1998, 98, 1689.
(11) (a) Ash, A. S. F.; Challenger, F.; Greenwood, D. J . Chem. Soc.
1951, 1877. (b) J ohnson, C. R.; Mori, K.; Nakanishi, A. J . Org. Chem.
1979, 44, 2065. (c) Dolle, R. E.; Li, C.-S.; Shaw, A. N. Tetrahedron Lett.
1989, 30, 4723.
(19) Fleming, I.; Paterson, I.; Pearce, A.J . Chem. Soc., Perkin Trans.
1 1981, 256.
(12) Tamura, Y.; Matsushima, H.; Minamikawa, J .; Ikeda, M.;
Sumoto, K. Tetrahedron 1975, 31, 3035.
(13) Atkinson, R. S.; Awad, S. B. J . Chem. Soc., Perkin Trans. 1
1977, 346.
(20) Harayama, H.; Kozera, T.; Kimura, M.; Tanaka, S.; Tamaro,
Y. Chem. Lett. 1996, 543.
(21) Oswald, A. A.; Griesbaum, K.; Hudson, B. E. J . Org. Chem.
1963, 28, 2355.
(14) Tamura, Y.; Ikeda, H.; Mukai, C.; Morita, I.; Ikeda, M. J . Org.
Chem. 1981, 46, 1732.
(15) Shea, R. G.; Fitzner, J . N.; Fankhauser, J . E.; Spaltenstein, A.;
Carpino, P. A.; Peevey, R. M.; Pratt, D. V.; Tenge, B. J .; Hopkins, P.
B. J . Org. Chem. 1986, 51, 5243.
(22) Sato, K.; Inoue, S.; Takagi, Y.; Morii, S. Bull. Chem. Soc. J pn.
1976, 49, 3351.
(23) Ducher, S.; J ournou, M. N. Ann. Chim. 1973, 8, 359.
(24) Hiroi, K.; Sato, H.; Kotsuji, K. Chem. Lett. 1986, 743.
(25) Corey, E. J .; Seebach, D. J . Org. Chem. 1966, 31, 4097.

2360 J . Org. Chem., Vol. 65, No. 8, 2000
Bach and Ko¨rber
Ta ble 2. Syn th esis of P r otected N-Allyla m in es 3 by
Sch em e 2
Im id a tion /[2,3]-Rea r r a n gem en t
entry
sulfide
FeCl2 (equiv)
product
yielda (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
1a b
1a
1b
1c
1d
1d
1e
0.25
0.10
0.25
0.10
0.25
0.10
0.25
0.25
0.25
0.25
0.10
0.25
0.10
0.10
3a
3a
3b
3c
3d
3d
3e
3f
3g
3h
3i
3j
3j
69
75
70
62 (94)
22 (-)c
32 (40)
48
1f
65 (78)
70
1gd
1h e
1i
70f
66 (75)
48 (60)
41 (84)
52
1j
1j
1k g
3k
a
Yield of isolated product. The yield based on sulfide conversion
is given in parentheses. E/Z ratio: 86/14. c Amount of recovered
b
starting material was not determined. E/Z ratio: 69/31. e Used
d
as a 90/10 mixture of double bond isomers (vide infra). E/Z
double-bond isomer 2-(2-methylpropyl)-2-propenyl phenyl
sulfide (isomer ratio: 90/10).
ratio: 82/18. f Obtained as a 84/16-mixture of double bond isomers.
g
E/Z ratio: 80/20.
in CH2Cl2. Nitrogen evolved, and the color of the mixture
turned from colorless to red. After the mixture was
stirred overnight, the desired protected N-allylamines
were obtained. Most experiments were conducted with
the allyl phenyl sulfides 1, which gave the corresponding
N-allylamines 3 (eq 4). It is important to note that in
these experiments the reagents BocN3 and sulfide 1 were
used in a 1:1 ratio whereas in many related transforma-
tions of this type one reagent is used in considerable
excess. All yields provided in Table 2 refer to isolated
product. In cases in which the conversion of sulfide was
incomplete the yield was corrected with regard to the
amount of recovered starting material and this value is
given in brackets. Obviously, an increase of the sulfide/
BocN3 ratio has a beneficial influence on the yield but
for reasons of practicability this possibility was not looked
into more closely.
Initial experiments were carried out with a catalyst
loading of 25 mol %. It turned out in the course of the
study that lower catalyst/substrate ratios led to an
increase in yield (entries 1/2, 5/6, 12/13) and were
therefore preferred. A catalyst/substrate ratio of 1:10
(0.1 equiv of FeCl2) is recommended. Side reactions
(vide infra) are suppressed, and the conversion is still
sufficient. Functional groups tolerated include alcohols
(entry 3), ethers (entry 14), and esters (entry 6). The
reaction makes sterically congested allylamines acces-
sible that bear a tertiary alkyl group at the nitrogen atom
(entries 11-14).
As an example for an R-branched allyl sulfide, the
enantiomerically pure substrate 13 was prepared starting
from the known, lactic acid-derived tosylate 8.29 The
sequence we followed has been described for the re-
lated isopropylsulfanyl-substituted product in a paper by
Bellus et al. (Scheme 2).29 Nucleophilic substitution of
tosylate 8 by thiophenolate delivered methyl 2-phenyl-
sulfanylpropionate (9), which was converted to acrylate
10 by reduction to the aldehyde and subsequent Horner-
Wadsworth-Emmons reaction. Reduction of the ester
with Dibal-H at 0 °C in CH2Cl2 furnished the allyl alcohol
11, whose enantiomeric purity was determined by de-
rivatization with (-)-menthyl chloroformate. GLC and
1H NMR analysis revealed the presence of a single
diastereoisomer (>95% de). Since the subsequent trans-
formations, i.e., the bromodehydroxylation to the bromide
12 and the reduction to the target compound, obviously
did not interfere with the stereogenic center the sulfide
13 was assumed to be enantiomerically pure (>95% ee).
Im id a tion a n d [2,3]-Rea r r a n gem en t. The nitrene-
transfer reaction was performed as previously described8
employing BocN3 as the nitrene source and FeCl2 as the
catalyst. The reaction was carried out at room temper-
ature by simply adding the catalyst to a premixed
Mechanistically, we assume the nitrene transfer to
occur via an Fe(IV)-nitrene complex 14, which is formed
from the azide and FeCl2 (Scheme 3). The transfer of the
solution of BocN3 (CAUTION!31) and the allyl sulfide
30
(30) BocN3 was prepared according to
a published procedure:
(26) Hannaby, M.; J udson, P. Warren, S. J . Chem. Soc., Perkin
Trans. 1 1992, 2609.
(27) Giese, B.; Mazumdar, P. Chem. Ber. 1981, 114, 2859.
(28) Clennan, G. L.; Chen, X.; Koda, J . J . J . Am. Chem. Soc. 1990,
112, 5193.
(29) Ernst, B.; Gonda, J .; J eschke, R.; Nubbemeyer, U.; Oehrlein,
R.; Bellus, D. Helv. Chim. Acta 1997, 80, 876.
Carpino, L. A.; Carpino, B. A.; Crowley, P. J .; Giza, C. A.; Terry, P. H.
Organic Syntheses; Wiley: New York, 1973; Collect. Vol. 5, p 157.
(31) CAUTION! Explosions have been reported to occur during
attempted distillation of BocN3, cf. P. Feyen, P. Angew. Chem. 1977,
89, 119; Angew. Chem., Int. Ed. Engl. 1977, 16, 115. The substance is
a potential explosive and is known to be a health hazard. Appropriate
safety protections and utmost care are required while handling BocN3.

Fe(II)-Catalyzed Imidation of Allyl Sulfides
J . Org. Chem., Vol. 65, No. 8, 2000 2361
Sch em e 3
Starting material and catalyst were wasted and the yield
diminished. It might also explain why the anisyl reagent
5 despite its higher nucleophilicity delivered a somewhat
lower yield of N-allylamine 21 (eq 5) than the comparable
phenyl sulfide 1a . The single electron transfer is fast but
the higher reactivity might lead to an increased tendency
for C-S bond cleavage. Indeed, the p-methoxybenzene-
sulfenamide related to 20 was observed as a byproduct
in the transformation of 5 f 21.
In a final set of experiments, the R-branched allyl
sulfides 10 and 13 were used as substrates for the
Fe(II)-catalyzed imidation and the subsequent sulfimide
rearrangement. It is well established that a chirality
transfer occurs in [2,3]-sigmatropic rearrangement reac-
tions33 and the closely related sulfoxide/allyl alcohol
rearrangement has been intensively studied.34 In the
sulfimine series, an efficient chirality transfer was
observed by Dolle et al., who successfully employed the
imidation of R-branched allyl methyl sulfides with MSH
and the concomitant rearrangement in the synthesis of
enantiomerically pure alkaloids and â-lactams.35,36 Due
to the steric bias on the sulfur atom, the nucleophilicity
of R-branched allyl sulfides is significantly reduced. Dolle
et al. therefore recommended the use of allyl methyl
sulfides instead of allyl phenyl sulfides. On the basis of
this precedence and based on our previous experience
with methoxycarbonyl substituted allyl sulfides (cf. 1d
f 3d ) the sulfide 10 was certainly not an ideal substrate
and it was foreseen that its reaction was sluggish. Indeed,
the attempted sulfimidation/rearrangement reaction with
substrate 10 (Scheme 2) gave a disappointing low yield
of the corresponding N-allylamine 22 (eq 6). Even worse,
“NBoc” fragment to sulfur liberates FeCl2, which is
available for the next catalytic cycle. If the N-S bond
formation is slow, a competition reaction with FeCl2 as
the nucleophile can lead to an Fe(III)-µ-imido complex
15,32 which is not catalytically active any more and which
yields carbamate 16 upon hydrolysis. This sequence of
events parallels the reaction course suggested earlier8b
for simple sulfides. The second reaction step as pointed
out in Scheme 1 is the [2,3]-shift (2 f 3), which is likely
to proceed in a sigmatropic fashion. We have not found
an indication for a simple homolysis of the C-S bond in
the intermediate sulfimide 2, which should give a radical
pair and which should yield at least partially a 1,2-
rearrangement product. However, there is an indication
for a C-S bond cleavage as possible side reaction before
the sulfimide formation is complete. A side product
isolated in varying amounts was proven to be N-tert-
butyloxycarbonyl benzenesulfenamide (20), which is likely
to be formed from an Fe(III) species 19 upon hydrolysis.
If the nitrene transfer from complex 14 to the sulfide 1
is not a two-electron process but occurs via the Fe(III)
intermediate 17, a simple explanation for the occurrence
of 19 and 20 can be put forward. Intermediate 17 has
two possible reaction pathways, one of which is the
homolytic cleavage of the Fe-N bond leading to sulfimide
2 and regenerating FeCl2. The other pathway, however,
does not complete the catalytic cycle but rather provides
access to the metalated amide 19 and to an allyl radical
18 by C-S bond cleavage. The fate of the transient allyl
radical 18 is less clear than the fate of the amide 19. It
might react further either by combining with FeCl2
(giving an alkene after workup), by recombination, by
reaction with the solvent, or by other less well-defined
events. The tentative mechanistic picture is summarized
in Scheme 3. For clarity, possible ligands at the iron
atoms have been omitted.
the chirality transfer was insufficient and the enantio-
meric excess of 22 was determined to be 39% ee by chiral
HPLC (Daicel Chiracel OD). Whereas the low yield of the
reaction 10 f 22 can be explained by the weak nucleo-
philicity of the sulfide and by the facile C-S bond
cleavage which shuts down the catalytic cycle (vide supra)
we were not sure why the enantiomeric purity of the
product was so low. Our initial assumption of a possible
racemization of the starting material had to be discarded
as the recovered sulfide 10 proved to be still 90% optically
pure. A racemization of the product 22, however, might
be possible as a consequence of its substantial CH-acidity.
This argument was plausible at first. It worried us,
however, that the double bond isomer of 22 which should
The mechanism depicted in Scheme 3 explains well the
unsatisfactory results obtained with the acrylic ester 1d
in the attempted imidation. The cleavage to the stabi-
lized, methoxycarbonyl-substituted allyl radical 18d
could effectively compete with the nitrene transfer.
(33) Hill, R. K. In Asymmetric Synthesis; Morrison, J . D., Ed.;
Academic: New York, 1984; Vol. 3, part B, p 503.
(34) (a) Evans, D. A.; Andrews, G. C. Acc. Chem. Res. 1974, 7, 147.
(b) Hoffmann, R. W. Angew. Chem. 1979, 91, 625; Angew. Chem., Int.
Ed. Engl. 1979, 18, 563.
(35) (a) Dolle, R. E.; Osifo, K. I.; Li, C.-S. Tetrahedron Lett. 1991,
32, 5029. (b) Dolle, R. E.; Li, C.-S.; Novelli, R.; Kruse, L. I.; Eggleston,
D. J . Org. Chem. 1992, 57, 128.
(36) For a related rearrangement, see: Whitesell, J . K.; Yaser, H.
K. J . Am. Chem. Soc. 1991, 113, 3526.
(32) A related µ-imido complex has been isolated and structurally
characterized: Nichols, P. J .; Falon, G. D.; Murray, K. S.; West, B. O.
Inorg. Chem. 1988, 27, 2795.

2362 J . Org. Chem., Vol. 65, No. 8, 2000
Bach and Ko¨rber
Ta ble 3. Dep r otection of Su lfen a m id es 3 w ith Tr ibu tyl
Tin h yd r id e
also result from such a process was not detected. We
turned toward the other substrate 13 which should yield
a configurationally stable product.
Unfortunately, sulfide 13 ([R]25D ) +46.1) did not prove
much superior to 10 in its reaction with BocN3 and FeCl2.
The yield of the protected N-allylamine 23 (eq 7) was
again unsatisfactory (32%) albeit higher than the yield
of amine 22 obtained earlier. With an excess of sulfide
entry
sulfenamide
R1
CH3
CH2OH
-(CH2)4-
R2
product
yielda (%)
1
2
3
4
5
3a
3b
3f
H
H
4a
4b
4f
4g
4h
93
71
86
90
76c
3g
CH3
i-Pr
CH3
CH3
3h b
a
b
Yield of isolated product. Employed as a 84/16 mixture of
double bond isomers (vide infra). c Obtained as a 77/23 mixture
of double bond isomers.
and cleanly by refluxing the sulfenamide 3, Bu3SnH and
a catalytic amount of AIBN in benzene (eq 8, Table 3).
13 (1.6 equiv), the yield could be improved to 47%.
Surprisingly, the recovered sulfide 13 showed a rather
strong detoriation of its optical purity ([R]25 ) +34.5;
D
75% ee). The enantiomeric excess of the product 23 was
determined after desulfurization (vide supra) to the
corresponding N-Boc-protected allylamine by chiral HPLC
(Daicel Chiracel OD). Although the baseline separation
was not fully complete the enantiomeric excess was
clearly in the same range ((5% ee) as the one determined
for 22 (39% ee). As product 23 is certainly not CH-acidic
enough to account for racemization and as the optical
purity of product and recovered starting material are not
identical additional factors appear to influence the extent
of the chirality transfer. It is our current opinion that
the stereogenic center in N-Boc-substituted sulfimines
does have a significant impact on the course of the [2,3]-
sigmatropic rearrangement and that it is this impact
which renders the stereochemical outcome of the reaction
less selective and less predictable than the outcome of
related rearrangements. At this point, we stopped looking
into the reaction of R-branched allyl sulfides more closely
for several reasons. First, the yields of their transforma-
tion had not been preparatively useful. Second, the
sulfides 10 and 13 were not configurationally stable
under the reaction conditions. A possible racemization
might be caused by the C-S bond cleavage in intermedi-
ates related to 17 (Scheme 3) and subsequent recombina-
tion. Third, the facial diastereoselectivity of the imidation
with BocN3/FeCl2 employing chiral R-branched sulfides
is low and the stereogenic center at sulfur could therefore
not be controlled.37 The situation would dramatically
change if a chiral Fe(II)-catalyst was at hand which
allowed the enantioselective preparation of sulfimides.
Work along these lines is currently in progress in our
laboratories.
When we attempted to apply the very same conditions
to R-branched N-allylamines with a tertiary carbon
moiety the results were disappointing. There was an
array of side products which were difficult to separate
and the yield of the desired products remained low. In
the case of the sulfenamide 3j one of the side products
was isolated in pure form and its structure was eluci-
dated by spectroscopic methods. It turned out to be the
enamide 24 which hydrolyzed upon standing to the amide
25 whose structure was unambiguously proven by com-
parison with the known compound.40 To explain the
formation of product 24, we assume that a nitrogen
centered radical 26 is formed by attack of the tributyl
tin radical at the sulfur. A subsequent 1,2-shift, possibly
via an aziridine intermediate, results in the carbon
centered radical which abstracts a hydrogen atom from
Bu3SnH to give product 24.
The failure of the Bu3SnH-method for the deprotection
of the above-mentioned sulfenamides let us return to the
nucleophilic displacement reaction with triethyl phos-
phite which has been used frequently for the deprotection
of related N-allyl sulfenamides.11c In the case of the
corresponding benzenesulfenamide its use is a bit ham-
pered by increased steric hindrance at the electrophilic
sulfur atom. Methanesulfenamides are certainly better
substrates for this reagent. Nonetheless, we were able
to achieve a reasonable good yield of N-Boc amines 4 by
treatment of the sulfenamides 3 with P(OEt)3 and NEt3
in CH2Cl2 at reflux. The reaction is outlined in eq 9 and
the results are summarized in Table 4.
Desu lfu r iza tion of th e N-Boc-P r otected Allylic
Su lfen a m id es 3. The removal of an arylsulfanyl group
from the corresponding sulfenamide to yield the unpro-
tected amine is well precedented.38 In our case, it was of
interest to find a method that would leave the N-Boc
group in place while the phenylsulfanyl group was
removed. This premise ruled out the use of many rather
drastic deprotection conditions. For the branched N-
allylamines 3 that bear a secondary branched carbon
chain at the nitrogen atom (Scheme 1, R ) H), a radical-
based method employing Bu3SnH39 proved ideal. The
removal of the phenylsulfanyl moiety proceeded rapidly
As a final remark, it should be mentioned that in the
imidation/rearrangement sequence deprotected N-Boc
N-allylamines 4 can be formed directly from the sulfides
1. In particular, if larger quantities of FeCl2 (>10 mol
(37) Ko¨rber, C. Ph.D. Thesis, Universita¨t Marburg, 1999.
(38) Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic
Synthesis, 3rd ed.; Wiley: New York, 1999; pp 600.
(39) Bowman, W. R.; Clark, D. N.; Marmon, R. J . Tetrahedron 1994,
50, 1275.
(40) White, D. K.; Greene, F. D. J . Org. Chem. 1978, 43, 4530.

Fe(II)-Catalyzed Imidation of Allyl Sulfides
J . Org. Chem., Vol. 65, No. 8, 2000 2363
Ta ble 4. Dep r otection of Su lfen a m id es 3 w ith Tr ieth yl
P h osp h ite
cooled to -78 °C. 60 mL Dibal-H (60 mmol, 1 N in hexane)
was added dropwise. After being stirred for 30 min, 6.5 mL
aqueous acetic acid (50%) was added and the mixture was
warmed to room temperature. The precipitate was removed
by filtration and washed with acetone. The filtrate was
concentrated, and the residue was purified by column chro-
matography (P/MTBE ) 55/45). 1.7 g (46%) of 1b was obtained
as a yellow liquid. The NMR data were in agreement with the
literature values.21
entry sulfenamide
R
R1
R2 product yielda (%)
1
2
3
3i
3j
3k
CH3 CH3
CH3 CH3
CH3 CH2OBn
H
CH3
H
4i
4j
4k
62
50
43
a
Yield of isolated product.
(E)-3-Met h oxyca r b on ylp r op -2-en yl P h en yl Su lfid e
(1d ).23 A 3.6 mL portion of methyl 4-bromocrotonate43 (5.4 g,
30 mmol) and 3.1 mL of thiophenol (3.3 g, 30 mmol) were
dissolved in 50 mL of dry diethyl ether and cooled to -10 °C.
A 4.1 mL portion of triethylamine (3.0 g, 30 mmol) was added
dropwise during 1 h. After being stirred at -10 °C for 30 min,
the mixture was refluxed for 1.5 h and stirred overnight at
room temperature. The precipitate was removed by filtration
and washed with diethyl ether. The filtrate was washed with
aqueous NaOH and dried over MgSO4. After the solvent was
removed the residue was purified by column chromatography
(P/MTBE ) 96/4). 5.1 g (82%) of 1d was obtained as a colorless
liquid. The NMR data were in agreement with the literature
values.23
%) were employed the amount of deprotected product
increased in some cases to a significant extent. As an
instructive example the sulfide 1i yielded a 66% yield of
the corresponding sulfenamide 3i upon treatment with
BocN3 and 10 mol-% FeCl2 (eq 4, Table 2, entry 11). If
25 mol % of FeCl2 were employed in the very same
transformation the yield of sulfenamide 3i decreased to
32%. Simultaneously, the deprotected amine 4i was
isolated in 30% yield. In separate experiments we showed
that FeCl2 can be used to deprotect sulfenamides but the
yields obtained never exceeded the yields obtained with
the conventional reagents used above.
(E)-4,4-Dim eth ylpen t-2-en yl P h en yl Su lfide (1e).18 Typi-
ca l P r oced u r e A. Sodium (0.50 g, 20 mmol) was dissolved in
20 mL of dry ethanol. Subsequently, 2.1 mL of thiophenol (2.2
g, 20 mmol) and a solution of 3.5 g of (E)-4,4-dimethyl-2-
pentenyl bromide42 (20 mmol) in 20 mL of dry ethanol were
added. The mixture was stirred for 5 h at room temperature
and then poured into 100 mL of water. The aqueous layer was
extracted with CH2Cl2. The combined organic layers were
washed with water and dried over MgSO4. After the solvent
was removed the residue was purified by column chromatog-
raphy (P/MTBE ) 96/4), 3.9 g (94%) of 1e was obtained as a
colorless liquid. The NMR data were in agreement with the
literature values.18
Con clu sion a n d Ou tlook
In summary, the synthesis of N-Boc-protected R-
branched allylic sulfenamides can be readily achieved
from the corresponding allyl sulfides by treatment
with BocN3 and catalytic amounts of FeCl2. The subse-
quent removal of the phenylsulfanyl group is facile for
R-branched N-Boc benzenesulfenamides with a secondary
allyl group at the nitrogen atom, the reagent of choice
being Bu3SnH. For N-Boc benzenesulfenamides with a
tertiary group at the nitrogen atom the deprotection is
best conducted with P(OEt)3. The results obtained with
the latter procedure are not fully satisfactory but it is
likely that methanesulfenamides can be more readily
deprotected. The use of a methylsulfanyl instead of a
phenylsulfanyl group might also be advantageous for the
rearrangement of R-branched allyl sulfides which pro-
ceeded sluggishly with the substrates tested in this study.
Further work regarding the stereoselectivity of the
imidation/[2,3]-sigmatropic rearrangement is currently
conducted in our laboratories.
3-Meth yl-2-bu ten yl P h en yl Su lfid e (1i).19 As described
in typical procedure A, the reaction of 0.50 g of sodium (20
mmol), 2.1 mL of thiophenol (2.2 g, 20 mmol), and 2.1 g of
1-chloro-3-methyl-2-butene41 (20 mmol) was carried out at
reflux temperature (reaction time: 3.5 h). The crude product
was purified by column chromatography (P). A total of 3.1 g
(88%) of 1i was obtained as a colorless liquid. The NMR data
were in agreement with the literature values.19
2-Bu ten yl p-Meth oxyp h en yl Su lfid e (5).20 As described
in typical procedure A, the reaction of 0.25 g of sodium (10
mmol), 1.2 mL of p-methoxythiophenol (1.4 g, 10 mmol), and
1.4 g of crotyl bromide (10 mmol) was carried out at room
temperature (reaction time: 2 h). The crude product was
purified by column chromatography (P/MTBE ) 98.5/1.5). A
total of 1.9 g (quant) of 5 was obtained as a colorless liquid
(E/Z: 86/14). Rf ) 0.37 (P/MTBE ) 98.5/1.5). 1H NMR: δ )
1.60-1.64 (m, 3 H), 3.36-3.40 (m, 2 H), 3.77 (s, 3 H), 5.39-
5.50 (m, 2 H), 6.79-6.84 (m, 2 H), 7.29-7.38 (m, 2 H). 13C
NMR: δ ) 17.6, 38.5, 55.2, 114.2, 126.5, 128.5, 136.0, 140.0,
158.9.
Exp er im en ta l Section
Gen er a l Meth od s. For general remarks see ref 8b. Solvents
(P ) pentane, MTBE ) methyl tert-butyl ether) used for
chromatography were distilled prior to use. High-pressure
liquid chromatography (HPLC) was performed on a Merck-
Hitachi L6200A instrument (flow rate: 0.4 mL × min-1
,
4-Ben zyloxy-3-m eth yl-2-bu ten yl P h en yl Su lfid e (1k ).
A 605 mg portion of 1-benzyloxy-4-bromo-2-methyl-2-butene22
(2.4 mmol) (E/Z: 80/20) was dissolved in 8 mL of dry THF
and cooled to 0 °C. Subsequently, 0.42 mL of triethylamine
(303 mg, 3 mmol) and 0.30 mL of thiophenol (323 mg, 2.9
mmol) were added. The mixture was stirred at 0 °C for 30 min.
Stirring was continued at room temperature for an additional
3 h. The mixture was poured into 100 mL of water. After the
addition of 50 mL of diethyl ether, the layers were separated,
and the aqueous layer was extracted with diethyl ether. The
combined organic layers were washed successively with water,
aqueous NaOH, aqueous HCl, and aqueous NaHCO3. After
drying over MgSO4, the solvent was removed and the residue
was purified by column chromatography (P/MTBE ) 99/1). A
total of 730 mg (quant) of 1k was obtained as a colorless liquid
(E/Z: 80/20). Rf ) 0.19 (P/MTBE ) 99/1). IR (film): ν˜ ) 1071
n-hexane/2-propanol ) 99/1), equipped with an UV spectrom-
eter detector (254 nm). For the determination of ee values
a
Daicel Chiracel OD column was used. The following
compounds were synthesized as described in the literature:
2-butenyl phenyl sulfide (1a ),16 (E)-1-phenyl-2-propenyl phenyl
sulfide (1c),17 methyl (S)-O-toluenesulfonyl lactate (8),29 1-chloro-
3-methyl-2-butene,41 (E)-4,4-dimethyl-2-pentenyl bromide,42
methyl 4-bromo-crotonate,43 1-benzyloxy-4-bromo-2-methyl-2-
butene.22
(E)-4-Hyd r oxy-2-bu ten yl P h en yl Su lfid e (1b).21 A 4.1 g
portion of (E)-3-methoxycarbonylprop-2-enyl phenyl sulfide
(1d ) (20 mmol) was dissolved in 60 mL of dry toluene and was
(41) Schneider P.; Cloux R.; Foti, K.; Kovats, E. Synthesis 1990, 11,
1027.
(42) de la Mare, P. B. D.; Hughes, E. D.; Merriman, P. C.; Pichat,
L.; Vernon, C. A. J . Chem. Soc. 1958, 2563.
(43) Ziegler, K.; Spa¨ht, A.; Schaaf, L.; Schumann, W.; Winkelmann,
L. J ustus Liebigs Ann. Chem. 1942, 551, 80.
1
cm-1 (s, COC), 738 (s, SC). (E)-1k . H NMR: δ ) 1.66 (br s, 3
H), 3.62 (dq, J ) 7.3, 0.7 Hz, 2 H), 3.91 (d, J ) 0.7 Hz, 2 H),
4.42 (s, 2 H), 5.64 (tq, J ) 7.3, 1.5 Hz, 1 H), 7.20-7.40 (m, 10

2364 J . Org. Chem., Vol. 65, No. 8, 2000
Bach and Ko¨rber
H). 13C NMR: δ ) 13.8, 31.7, 71.4, 75.2, 122.7, 126.2, 127.5,
-78 °C. A 16 mL portion of Dibal-H (16 mmol, 1 N in hexane)
was added dropwise. To this solution was added a mixture of
530 mg of NaH (80% in white oil, 17 mmol) and 3.2 mL of
diethoxyphosphoryl acidic acid methyl ester (3.7 g, 17 mmol)
in 10 mL of dry CH2Cl2. The mixture was warmed overnight
with stirring. After addition of 60 mL of aqueous KNa tartrate
(30% w/w), the solution was stirred for an additional hour. An
80 mL portion of water was added, and after separation of the
layers, the aqueous layer was extracted with CH2Cl2. The
combined organic layers were washed with water and brine
and dried over MgSO4. After the removal of the solvent, the
residue was purified by flash chromatography (P/MTBE ) 96/
64). Compound 10 (2.0 g, 66%) was obtained as a colorless
liquid (E/Z: >95/5). [R]25D ) +85.3 (c ) 1.1, acetone). The NMR
data were in agreement with the literature values.45
1
127.7, 128.3, 128.7, 130.1, 136.1, 138.8. (Z)-1k . H NMR: δ )
1.83 (q, J ) 1.0 Hz, 3 H), 3.57 (br d, J ) 7.5 Hz, 2 H), 3.91 (d,
J ) 0.7 Hz, 2 H), 4.45 (s, 2 H), 5.56 (tq, J ) 7.5, 1.0 Hz, 1 H),
7.20-7.40 (m, 10 H). 13C NMR: δ ) 21.7, 25.5, 67.9, 71.8,
123.8, 126.2, 127.1, 127.6, 128.4, 129.0, 129.8, 130.1, 136.4.
HRMS (C18H20OS): calcd 284.1234, found 284.1229.
1-Cycloh exen ylm eth yl P h en yl Su lfid e (1f).26 Typ ica l
P r oced u r e B.24 A 2.4 mL portion of thioanisol (2.5 g, 20 mmol)
was dissolved in 35 mL of dry THF and cooled to 0 °C. A 12.5
mL portion of n-BuLi (20 mmol, 1.6 n in hexane) was slowly
added, and the mixture was stirred 15 min at 0 °C. Stirring
was continued at room temperature overnight. The mixture
was cooled to 0 °C, and a solution of 2.1 mL of cyclohexanone
(6f) (2.0 g, 20 mmol) in 4 mL of dry THF was added. After the
mixture was stirred at room temperature for 2.5 h, 200 mL of
water was added. The aqueous layer was extracted with CH2-
Cl2. The combined organic layers were washed with water and
brine. The solution was dried over Na2CO3. The solvent was
removed and the resulting hydroxy compound 7f was dissolved
in 200 mL of benzene. After addition of a catalytic amount of
p-toluenesulfonic acid the mixture was refluxed for 4 h. The
cold solution was washed with aqueous NaOH and dried over
Na2CO3. The solvent was removed and the residue was purified
by column chromatography (P). A total of 3.1 g (76% over two
steps) of 1f was obtained as a colorless liquid. The NMR data
were in agreement with the literature values.26
(E)-(R)-4-Hyd r oxy-1-m eth yl-2-bu ten yl P h en yl Su lfid e
(11). A 1.5 g portion of (E)-(R)-3-methoxycarbonyl-1-methyl-
2-butenyl phenyl sulfide (10) (6.5 mmol) was dissolved in 20
mL of dry THF and cooled to 0 °C. A 22 mL portion of Dibal-H
(22 mmol, 1 n in hexane) was added, and after the mixture
was stirred for 1 h at 0 °C, 3 mL of methanol, 20 mL of water,
2 mL of aqueous NaOH, and 20 mL of aqueous KNa tartrate
(30% w/w) were added successively. The mixture was stirred
for 2 h at room temperature, and the layers were separated.
The aqueous layer was extracted with CH2Cl2 (3 × 20 mL),
and the combined organic layers were washed with water and
brine and dried over MgSO4. After evaporation of the solvent,
the residue was purified by column chromatography (P/MTBE
) 80/20). Compound 11 (1.1 g, 87%) was obtained as a colorless
2-Meth yl-2-bu ten yl P h en yl Su lfid e (1g).27 As described
in typical procedure B, the reaction was carried out with 8
mL of 2-butanone (6g) (1.4 g, 20 mmol). The subsequent
elimination reaction of the resulting hydroxy compound 7g
yielded 2.8 g (78% over two steps) of 1g as a colorless liquid
(E/Z 69/31). The NMR data were in agreement with the
liquid. Rf ) 0.33 (P/MTBE ) 60/40), [R]25 ) +37.3 (c ) 1.1,
D
acetone). IR (film): ν˜ ) 3357 cm-1 (w, OH), 1191 (s, COC),
748 (s, SC). 1H NMR: δ ) 1.38 (d, J ) 7.0 Hz, 3 H), 1.59
(br s, 1 H), 3.76 (quint, J ) 7.0 Hz, 1 H), 3.98 (br d, J ) 5.2
Hz, 2 H), 5.48 (dt, J ) 15.6, 5.2 Hz, 1 H), 5.66 (ddt, J ) 15.6,
7.5, 1.0 Hz, 1 H), 7.18-7.41 (m, 5 H). 13C NMR: δ ) 20.7,
48.6, 63.2, 117.7, 129.1, 130.0, 133.4, 133.7, 135.0. HRMS
(C11H14OS): calcd 194.0765, found 194.0761.
27
literature values.
2,4-Dim eth yl-2-p en ten yl P h en yl Su lfid e (1h ). As de-
scribed in typical procedure B, the reaction was carried out
with 2.1 mL of isobutyl methyl ketone (6h ) (1.7 g, 17 mmol).
The subsequent elimination reaction of the resulting hydroxy
compound 7h yielded 3.5 g (quant over two steps) of an iso-
meric mixture of 1h (ratio: 90/10) as a colorless liquid (E/Z:
82/18). Rf ) 0.26 (P). IR (film): ν˜ ) 2956 cm-1 (s, CH), 740 (s,
(E)-(R)-4-Br om o-1-m eth yl-2-bu ten yl P h en yl Su lfide (12).
A 2.36 g portion of (E)-(R)-4-hydroxy-1-methyl-2-butenyl phen-
yl sulfide (11) (12.1 mmol) and 0.32 mL of pyridine (0.31 g,
3.8 mmol) were dissolved under argon in 19 mL of pentane.
The mixture was cooled to -15 °C. A solution of 0.49 mL of
PBr3 (1.48 g, 5.3 mmol) in 4 mL of pentane was added dropwise
during 2 h. Stirring was continued at -10 °C for 2 h and after
the addition of 40 mL of water for an additional hour at room
temperature. The layers were separated, and the aqueous
layer was extracted with pentane. The combined organic layers
were washed with water and brine and dried over MgSO4, and
the solvent was removed. A total of 1.68 g (54%) of 12 was
obtained as a colorless liquid, which was used in the next step
1
SC). (E)-1h . H NMR: δ ) 0.82 (d, J ) 6.5 Hz, 6 H), 1.72 (d,
J ) 1.1 Hz, 3 H), 2.31-2.53 (m, 1 H), 3.43 (d, J ) 1.0 Hz, 2
H), 4.99 (dq, J ) 9.3, 1.1 Hz, 1 H), 7.10-7.38 (m, 5 H). 13C
NMR: δ ) 14.9, 22.6, 27.2, 44.5, 126.2, 127.7, 128.5, 131.0,
1
136.1, 137.2. (Z)-1h . H NMR: δ ) 0.87 (d, J ) 6.5 Hz, 6 H),
1.81 (d, J ) 1.5 Hz, 3 H), 2.31-2.53 (m, 1 H), 3.50 (d, J ) 1.0
Hz, 2 H), 4.91-4.92 (m, 1 H), 7.10-7.38 (m, 5 H). HRMS
(C13H18S): calcd 206.1129, found 206.1132.
2,3-Dim eth yl-2-bu ten yl P h en yl Su lfid e (1j).28 As de-
scribed in typical procedure B, the reaction was carried out
with 2.1 mL of methyl isopropyl ketone (6j) (1.7 g, 20 mmol).
The subsequent elimination reaction of the resulting hydroxy
compound 7j yielded 2.6 g (66% over two steps) of 1j as a
colorless liquid. The NMR data were in agreement with the
literature values.28
1
without further purification. Rf ) 0.76 (P/MTBE ) 60/40). H
NMR: δ ) 1.37 (d, J ) 7.0 Hz, 3 H), 3.72 (quint, J ) 7.2 Hz,
1 H), 3.84 (d, J ) 7.2 Hz, 2 H), 5.50 (dt, J ) 14.9, 7.2 Hz, 1 H),
5.73 (dd, J ) 14.9, 8.0 Hz, 1 H), 7.20-7.37 (m, 5 H). 13C NMR:
δ ) 20.0, 32.1, 45.0, 126.2, 127.5, 128.6, 133.0, 136.9.
(E)-(R)-1-Meth yl-2-bu ten yl P h en yl Su lfid e (13).46 A 0.24
g portion of LiAlH4 (6.3 mmol) was added to 17 mL of dry THF.
After the dropwise addition of a solution of 1.41 g of (E)-(R)-
4-bromo-1-methyl-2-butenyl phenyl sulfide (12) (5.5 mmol) in
5 mL of dry THF, the mixture was refluxed for 4 h. The
mixture was allowed to cool to room temperature. Then, 0.5
mL of water, 0.5 mL of aqueous NaOH, and 0.5 mL of water
were successively added to the stirred solution. After the
mixture was stirred for an additional hour at room tempera-
ture, the resulting slurry was extracted with CH2Cl2 and the
combined organic layers were dried over MgSO4. The solvent
was removed, and the residue was purified by column chro-
matography (P). Compound 13 (0.61 g, (62%) was obtained as
(R)-2-P h en ylsu lfa n ylp r op ion a te (9).44 A 11.3 g portion
of finely ground K2CO3 (82.0 mmol) and 4.46 mL of thiophenol
(4.74 g, 43.0 mmol) were mixed in 100 mL of CH3CN. Within
1 h, 10.6 g of methyl (S)-O-toluenesulfonyl lactate29 (8) in 100
mL of CH3CN was added dropwise. The mixture was vigor-
ously stirred for 5 d at room temperature. The solvent was
removed at 30 °C, and the residue was dissolved in 300 mL of
diethyl ether. The organic layer was washed with water and
brine and dried over MgSO4. The solvent was removed, and
the residue was purified by column chromatography (P/MTBE
) 98.5/1.5). 7.8 g (96%) of 9 was obtained as a colorless liquid.
[R]25 ) +65.5 (c ) 1.0, acetone). The NMR data were in
D
a colorless liquid. [R]25 ) +46.1 (c ) 1.0, acetone). The NMR
agreement with the literature values.44
D
data were in agreement with the literature values.46
(E)-(R)-3-Meth oxyca r bon yl-1-m eth yl-2-bu ten yl P h en yl
Su lfid e (10).45 2.7 g (R)-2-Phenylsulfanylpropionate (9) (14
mmol) was dissolved in 50 mL of dry CH2Cl2 and cooled to
(45) Brownbridge, P.; Hunt, P. G.; Warren, S. J . Chem. Soc., Perkin
Trans. 1 1986, 1695.
(46) Furuta, K.; Ikeda, Y.; Meguriya, N.; Ikeda, N.; Yamamoto, H.
Bull. Chem. Soc. J pn 1984, 57, 2781.
(44) Leyendecker, F.; Comte, M.-T. Tetrahedron 1986, 42, 1413.

Fe(II)-Catalyzed Imidation of Allyl Sulfides
J . Org. Chem., Vol. 65, No. 8, 2000 2365
N-ter t-Bu tyloxyca r bon yl-N-(1-m eth yl-2-p r op en yl)ben -
zen esu lfen a m id e (3a ). Typ ica l P r oced u r e C. A 143 mg
portion of BocN3 (1.0 mmol) and 165 mg of 2-butenyl phenyl
sulfide (1a ) (1.0 mmol) were dissolved in 1.0 mL of dry CH2-
Cl2. After addition of 32 mg of FeCl2 (0.25 mmol) [12 mg, 0.1
mmol], the mixture stirred at room temperature overnight. The
crude reaction mixture was separated by column chromatog-
raphy (P/MTBE ) 98.5/1.5). A total of 187 mg (69%) [207 mg,
75%] of 3a was obtained as a colorless oil. Rf ) 0.18 (P/MTBE
) 99/1). IR (film): ν˜ ) 1701 cm-1 (s, CdO), 1642 (s, CdC),
(321.49): C, 67.25; H, 8.47; N, 4.36. Found: C, 67.07; H, 8.42;
N, 4.11.
N-ter t-Bu tyloxyca r bon yl-N-(2-m eth ylen e cycloh exyl)-
ben zen esu lfen a m id e (3f). The reaction was carried out on
the same scale as described in typical procedure C starting
with 205 mg of 1-cyclohexenylmethyl phenyl sulfide (1f) (1.0
mmol). A total of 207 mg (65%) of 3f was obtained as colorless
crystals (P/MTBE ) 98.5/1.5 as eluent). Rf ) 0.32 (P/MTBE )
98/2). Mp: 57 °C. IR (KBr): ν˜ ) 1700 cm-1 (s, CdO), 1292 (s,
1
COC), 851 (s, SN), 737 (s, SC). H NMR: δ ) 1.19-1.15 (m, 2
1
H), 1.44 (s, 9 H), 1.66-2.08 (m, 5 H), 2.42-2.48 (m, 1 H), 4.47
(br s, 1 H), 4.73-4.80 (m, 1 H), 4.79 (br s, 1 H), 7.10-7.20 (m,
3 H), 7.26-7.31 (m, 2 H). 13C NMR: δ ) 25.5, 27.0, 27.9, 31.4,
35.1, 63.0, 81.7, 105.0, 123.4, 125.6, 128.6, 140.9, 147.1, 157.0.
Anal. Calcd for C18H25NO2S (319.45): C, 67.67; H, 7.89; N,
4.38. Found: C, 67.42; H, 7.96; N, 4.49.
1160 (s, C-O-C), 737 (s, S-C). H NMR (373 K, DMSO-d6):
δ ) 1.26 (d, J ) 6.8 Hz, 3 H), 1.42 (s, 9 H), 4.89 (dtq, J ) 6.8,
5.9, 1.4 Hz), 5.07 (dt, J ) 10.4, 1.4 Hz, 1 H,), 5.12 (dt, J )
17.3, 1.4 Hz, 1 H), 5.85 (ddd, J ) 17.3, 10.4, 5.9 Hz, 1 H),
7.17-7.24 (m, 3 H), 7.32-7.37 (m, 2 H). 13C NMR (373 K,
DMSO-d6): δ ) 19.0, 28.5, 58.6, 82.1, 116.0, 124.9, 126.9,
N-ter t-Bu tyloxyca r bon yl-N-(1,2-d im eth yl-2-p r op en yl)-
ben zen esu lfen a m id e (3g). The reaction was carried out on
the same scale as described in typical procedure C starting
with 180 mg of 2-methyl-2-butenyl phenyl sulfide (1g) (1.0
mmol). A total of 199 mg (70%) of 3g was obtained as a
colorless oil (P/MTBE ) 98/2 as eluent). Rf ) 0.27 (P/MTBE )
98/2). IR (film): ν˜ ) 1700 cm-1 (s, CdO), 1293 (s, COC), 1163,
853 (s, SN), 737 (s, SC). 1H NMR: δ ) 1.28 (d, J ) 6.7 Hz,
3 H), 1.47 (s, 9 H), 1.67 (s, 3 H), 4.82-4.97 (m, 3 H), 7.14-
7.20 (m, 5 H). 13C NMR: δ ) 16.9, 20.4, 28.0, 59.3, 81.7,
112.0, 124.5, 125.9, 128.5, 140.2, 145.0, 156.9. Anal. Calcd.
for C16H23NO2S (293.43): C, 65.49; H, 7.90; N, 4.77. Found:
C, 65.22; H, 7.75; N, 4.79.
N-ter t-Bu t yloxyca r b on yl-N-(2-m et h yl-1-isop r op yl-2-
p r op en yl)ben zen esu lfen a m id e (3h ). The reaction was car-
ried out on the same scale as described in typical procedure C
starting with 210 mg of 2,4-dimethyl-2-pentenyl phenyl sulfide
(1h ) (1.0 mmol). A total of 226 mg (70%) of an isomeric mixture
(ratio: 84/16) was obtained, from which 3h could be separated
from selected chromatography fractions as a colorless oil (P/
MTBE ) 99/1 as eluent). Rf ) 0.34 (P/MTBE ) 98.5/1.5). IR
(film): ν˜ ) 1701 cm-1 (s, CdO), 1281 (s, COC), 736 (s, SC). 1H
NMR: δ ) 0.86 (d, J ) 6.5 Hz, 3 H), 0.88 (d, J ) 6.5 Hz, 3 H),
1.45 (s, 9 H), 1.64 (s, 3 H), 2.27 (dsept, J ) 11.0, 6.5 Hz, 1 H),
4.35 (br d, J ) 11.0 Hz, 1 H), 4.87 (t, J ) 1.5 Hz, 1 H), 5.05 (br
s, 1 H), 7.12-7.40 (m, 5 H). 13C NMR: δ ) 19.7, 20.0, 21.2,
28.0, 69.8, 81.7, 115.6, 125.0, 126.0, 128.3, 139.6, 142.2, 157.3.
Anal. Calcd. for C18H27NO2S (321.48): C, 67.25; H, 8.46; N,
4.34. Found: C, 67.31; H, 8.32; N, 4.61.
129.5, 139.5, 141.7, 156.5. Anal. Calcd for
C15H21NO2S
(279.40): C, 64.48; H, 7.58; N, 5.01. Found: C, 64.38; H, 7.31;
N, 5.13.
N-ter t-Bu t yloxyca r b on yl-N-(1-h yd r oxym et h yl-2-p r o-
p en yl)ben zen esu lfen a m id e (3b). The reaction was carried
out on the same scale as described in typical procedure C
starting with 170 mg of (E)-4-hydroxy-2-butenyl phenyl sulfide
(1b) (1.0 mmol). A total of 207 mg (70%) of 3b was obtained
as a colorless oil (P/MTBE ) 65/35 as eluent). Rf ) 0.41 (P/
MTBE ) 65/35). IR (film): ν˜ ) 3452 cm-1 (w, OH), 1701 (s,
CdO), 740 (s, SC). 1H NMR: δ ) 1.46 (s, 9 H), 3.20 (br s, 1 H),
3.67 (dd, J ) 11.5, 5.5 Hz, 1 H), 3.81 (dd, J ) 11.5, 8.2 Hz, 1
H,), 4.85-4.95 (m, 1 H), 5.17 (dd, J ) 10.3, 1.2 Hz, 1 H), 5.22
(dd, J ) 17.2, 1.2 Hz, 1 H), 5.81 (ddd, J ) 17.2, 10.3, 6.8 Hz,
1 H), 7.16-7.30 (m, 5 H). 13C NMR: δ ) 28.4, 63.8, 65.1, 82.8,
119.0, 124.9, 126.8, 129.3, 134.2, 140.1, 157.6. Anal. Calcd. for
C
15H21NO3S (295.40): C, 60.99; H, 7.17; N, 4.74. Found: C,
60.85, H, 6.84; N, 4.79.
N-ter t-Bu tyloxyca r bon yl-N-(1-p h en yl-2-p r op en yl)ben -
zen esu lfen a m id e (3c). The reaction was carried out on the
same scale as described in typical procedure C starting with
226 mg of (E)-1-phenyl-2-propenyl phenyl sulfide17 (1c) (1.0
mmol). A total of 178 mg (52%) [212 mg, 62%] of 3c was
obtained as a colorless oil (P/MTBE ) 96/4 as eluent). Rf )
0.46 (P/MTBE ) 96/4). IR (film): ν˜ ) 1701 cm-1 (s, CdO), 1287
1
(s, COC), 737 (s, SC). H NMR: δ ) 1.42 (s, 9 H), 5.07 (dd, J
) 10.3, 1.0 Hz, 1 H), 5.25 (dd, J ) 17.0, 1.0 Hz, 1 H), 6.00 (d,
J ) 6.5 Hz, 1 H), 6.19 (ddd, J ) 17.0, 10.3, 6.5 Hz, 1 H), 7.06-
7.30 (m, 10 H). 13C NMR: δ ) 28.4, 66.5, 82.6, 118.7, 124.8,
126.4, 127.9, 128.3, 128.6, 129.0, 136.2, 140.0, 141.7, 157.0.
Anal. Calcd for C20H23NO2S (341.47): C, 70.35; H, 6.79; N,
4.10. Found: C, 70.38; H, 6.73; N, 4.11.
N-ter t-Bu tyloxyca r bon yl-N-(1,1-d im eth yl-2-p r op en yl)-
ben zen esu lfen a m id e (3i). The reaction was carried out on
the same scale as described in typical procedure C starting
with 180 mg of 3-methyl-2-butenyl phenyl sulfide (1i) (1.0
mmol). A total of 97 mg (32%) [198 mg, 66%] of 3i was obtained
as colorless crystals (P/MTBE ) 99/1 as eluent). Rf ) 0.33
(P/MTBE ) 98.5/1.5). Mp: 29 °C. IR (KBr): ν˜ ) 1710 cm-1 (s,
N-ter t-Bu tyloxyca r bon yl-N-(1-m eth oxyca r bon yl-2-p r o-
p en yl)ben zen esu lfen a m id e (3d ). The reaction was carried
out on the same scale as described in typical procedure C
starting with 177 mg of (E)-3-methoxycarbonyl-2-propenyl
phenyl sulfide (1d ) (1.0 mmol). A total of 72 mg (22%) [94 mg,
32%] of 3d was obtained as a colorless oil (P/MTBE ) 97/3
as eluent). Rf ) 0.10 (P/MTBE ) 97/3). IR (film): ν˜ ) 1704
1
CdO), 1283 (s, COC), 740 (s, SC). H NMR: δ ) 1.44 (s, 9 H),
1.51 (s, 6 H), 4.96 (dd, J ) 10.8, 0.7 Hz, 1 H), 5.00 (br d, J )
17.5 Hz, 1 H), 6.10 (dd, J ) 17.5, 10.8 Hz, 1 H), 7.09-7.19 (m,
5 H). 13C NMR: δ ) 28.0, 28.1, 64.5, 81.7, 110.3, 127.1, 127.4,
1
cm-1 (s, CdO), 1298 (s, COC), 740 (s, SC). H NMR: δ ) 1.45
129.0, 136.9, 145.8, 156.6. Anal. Calcd. for
C16H23NO2S
(s, 9 H), 3.70 (s, 3 H), 5.11 (d, J ) 7.4 Hz, 1 H), 5.29 (dd, J )
10.0, 1.0 Hz, 1 H), 5.29 (dd, J ) 17.2, 1.0 Hz, 1 H), 6.08 (ddd,
J ) 17.2, 10.0, 7.4 Hz, 1 H), 7.21-7.31 (m, 5 H). 13C NMR: δ
) 28.4, 52.8, 67.9, 83.3, 121.0, 125.2, 126.9, 129.1, 131.7, 139.5,
156.4, 170.7. Anal. Calcd for C16H21NO4S (323.41): C, 59.42;
H, 6.54; N, 4.33. Found: C, 59.40; H, 6.58; N, 4.43.
(293.43): C, 65.49; H, 7.90; N, 4.77. Found: C, 65.24; H, 8.03;
N, 4.59.
N-ter t-Bu tyloxycar bon yl-N-(1,1,2-tr im eth yl-2-pr open yl)-
ben zen esu lfen a m id e (3j). The reaction was carried out on
the same scale as described in typical procedure C starting
with 195 mg of 2,3-dimethyl-2-butenyl phenyl sulfide (1j)
(1.0 mmol). A total of 147 mg (48%) [126 mg, 41%] of 3j
was obtained as a colorless oil (P/MTBE ) 98.5/1.5 as eluent).
Rf ) 0.21 (P/MTBE ) 98.5/1.5). IR (film): ν˜ ) 1711 cm-1 (s,
N-ter t-Bu t yloxyca r bon yl-N-(1-ter t-b u t yl-2-p r op en yl)-
ben zen esu lfen a m id e (3e). The reaction was carried out on
the same scale as described in typical procedure C starting
with 207 mg of (E)-4,4-dimethyl-2-pentenyl phenyl sulfide (1e)
(1.0 mmol). A total of 154 mg (48%) of 3e was obtained as a
colorless oil (P/MTBE ) 96/4 as eluent). Rf ) 0.18 (P/MTBE )
96/4). IR (film): ν˜ ) 1749 cm-1 (s, CdO), 1287 (s, COC), 739
1
CdO), 1288 (s, COC), 848 (s, SN), 737 (s, SC). H NMR: δ )
1.45 (s, 9 H), 1.51 (s, 6 H), 1.70 (s, 3 H), 4.75 (br s, 1 H), 4.80
(br s, 1 H), 7.15-7.26 (m, 5 H). 13C NMR: δ ) 19.5, 28.1, 28.4,
67.1, 81.8, 108.2, 124.7, 126.1, 128.2, 141.3, 151.2, 156.8. Anal.
Calcd for C17H25NO2S (307.45): C, 66.41; H, 8.19; N, 4.55.
Found: C, 66.61; H, 8.11; N, 4.77.
1
(s, SC). H NMR: δ ) 0.95 (s, 9 H), 1.42 (s, 9 H), 4.66-4.80
(m, 1 H), 5.13 (dd, J ) 9.9, 1.5 Hz, 1 H), 5.24 (dd, J ) 16.8, 1.5
Hz, 1 H), 6.14 (ddd, J ) 16.8, 9.9, 7.5 Hz, 1 H), 7.03-7.28 (m,
5 H). 13C NMR: δ ) 27.6, 28.3, 55.7, 81.8, 82.1, 120.2, 123.0,
125.7, 128.8, 129.2, 134.4, 156.9. Anal. Calcd for C18H27NO2S
N-ter t-Bu tyloxycar bon yl-N-(1-ben zyloxym eth yl-1-m eth -
yl-2-p r op en yl)ben zen esu lfen a m id e (3k ). The reaction was
carried out on the same scale as described in typical procedure

2366 J . Org. Chem., Vol. 65, No. 8, 2000
Bach and Ko¨rber
C starting with 290 mg of 4-benzyloxy-3-methyl-2-butenyl
phenyl sulfide (1k ) (1.0 mmol). A total of 208 mg (52%) of
3k was obtained as a colorless oil (P/MTBE ) 99/1 as eluent).
Rf ) 0.15 (P/MTBE ) 99/1). IR (film): ν˜ ) 1706 cm-1 (s,
were converted as described in typical procedure D. A total of
56 mg (71%) of 4b was obtained as a colorless oil (P/MTBE )
50/50 as eluent). The NMR data were in agreement with the
literature values.48
1
CdO), 1285 (s, COC), 855 (s, SN), 737 (s, SC). H NMR: δ )
N-ter t-Bu tyloxyca r bon yl-N-(2-m eth ylen ecycloh exyl)-
a m in e (4f). A 234 mg portion of N-tert-butyloxycarbonyl N-(2-
methylenecyclohexyl)benzenesulfenamide (3f) (0.73 mmol)
and 0.28 mL of Bu3SnH (349 mg, 1.2 mmol) were converted
as described in typical procedure D. A total of 133 mg
(86%) of 4f was obtained as colorless crystals. Rf ) 0.23
(P/MTBE ) 96/4). Mp: 55 °C, IR (KBr): ν˜ ) 3330 cm-1 (w,
1.31 (s, 9 H), 1.47 (s, 3 H), 3.75 (br s, 2 H), 4.42 (s, 2 H), 4.96
(d, J ) 16.9 Hz, 1 H), 4.99 (d, J ) 11.3 Hz), 6.11 (dd, J ) 16.9,
11.3 Hz, 1 H), 6.97-7.22 (m, 10 H).13C NMR: δ ) 23.4, 27.9,
66.8, 73.1, 75.2, 81.6, 112.2, 123.1, 125.3, 127.3, 127.4, 128.2,
128.4, 138.3, 141.6, 156.5. Anal. Calcd for
C23H29NO3S
(399.56): C, 69.14; H, 7.31; N, 3.50. Found: C, 69.16; H, 7.41;
N 3.75.
1
NH), 1687 (s, CdO), 1273 (s, COC). H NMR (373 K, DMSO-
N-ter t-Bu t yloxyca r b on yl-N-(1-m et h yl-2-p r op en yl)-p -
m eth oxyben zen esu lfen a m id e (21). The reaction was car-
ried out on the same scale as described in typical procedure C
starting with 195 mg of 2-butenyl p-methoxyphenyl sulfide (5)
(1.0 mmol). A total of 160 mg (51%) [205 mg, 66%] of 21 was
obtained as a colorless oil (P/MTBE ) 98/2 as eluent). Rf )
0.20 (P/MTBE ) 98/2). IR (film): ν˜ ) 1700 cm-1 (s, CdO), 1292
d6): δ ) 1.22-1.45 (m, 4 H), 1.39 (s, 9 H), 1.64-1.67 (m, 1 H),
1.73-1.79 (m, 2 H), 1.96-2.00 (m, 1 H), 2.33-2.36 (m, 1 H),
3.82-3.88 (m, 1 H), 4.65 (s, 1 H), 4.68 (br s, 1 H). 13C NMR:
δ ) 25.2, 27.6, 28.4, 34.6, 35.2, 53.2, 79.2, 105.0, 149.3. Anal.
Calcd for C12H21NO2 (211.30): C, 68.21; H, 10.02; N, 6.63.
Found: C, 67.89; H, 9.68; N, 6.64.
N-ter t-Bu tyloxyca r bon yl-N-(1,2-d im eth yl-2-p r op en yl)-
a m in e (4g). A 140 mg portion of N-tert-butyloxycarbonyl-N-
(1,2-dimethyl-2-propenyl)benzenesulfenamide (3g) (0.48 mmol)
and 0.22 mL of Bu3SnH (247 mg, 0.85 mmol) were converted
as described in typical procedure D. A total of 80 mg (90%) of
4g was obtained as colorless crystals. Rf ) 0.34 (P/MTBE )
90/10). Mp: 53 °C. IR (KBr): ν˜ ) 3428 cm-1 (w, NH), 1683 (s,
1
(s, COC), 828 (s, SN), 737 (s, SC). H NMR: δ ) 1.23 (d, J )
6.8 Hz, 3 H), 1.45 (s, 9 H), 3.74 (s, 3 H), 4.82-4.90 (m, 1 H),
5.01 (dt, J ) 10.4, 1.4, 10.4 Hz, 1 H,), 5.04 (dt, J ) 17.3, 1.4
Hz, 1 H), 5.85 (ddd, J ) 17.3, 10.4, 5.7 Hz, 1 H), 6.76-6.84
(m, 2 H), 7.28-7.35 (m, 2 H). 13C NMR: δ ) 18.5, 28.1, 55.3,
57.9, 81.5, 114.4, 115.0, 129.8, 131.2, 139.0, 156.8, 159.2. Anal.
Calcd for C16H23NO3S (309.43): C, 62.11; H, 7.49; N, 4.53.
Found: C, 61.83; H, 7.56; N, 4.90.
1
CdO), 1253 (s, COC). H NMR: δ ) 1.17 (d, J ) 7.0 Hz, 3 H),
1.40 (s, 9 H), 1.67 (s, 3 H), 3.98-4.14 (m, 1 H), 4.50 (br s, 1 H),
N-ter t-Bu tyloxyca r bon yl-N-[(E)-1-m eth oxyca r bon yl-2-
bu ten yl]ben zen esu lfen a m id e (22). The reaction was carried
out as described in typical procedure C starting with 333 mg
of (E)-(R)-3-methoxycarbonyl-2-butenyl phenyl sulfide (10) (1.5
mmol), 143 mg of BocN3 (1.0 mmol), and 12 mg of FeCl2 (0.1
mmol). A total of 20 mg (6%) of 22 was obtained as a colorless
oil (39% ee) (P/MTBE ) 96/4 as eluent). Rf ) 0.08 (P/MTBE )
4.75 (br s, 1 H), 4.82 (br s, 1 H). 13C NMR: δ ) 19.3, 19.9,
28.3, 51.1, 79.1, 109.7, 146.7, 155.1. Anal. Calcd for C10H19
-
NO2 (185.29): C, 64.82; H, 10.34; N, 7.56. Found: C, 64.66;
H, 10.12, N, 7.24.
N-ter t-Bu t yloxyca r b on yl-N-(2-m et h yl-1-isop r op yl-2-
p r op en yl)a m in e (4h ). A 202 mg portion of N-tert-butyloxy-
carbonyl-N-(2-methyl-1-isopropyl-2-propenyl)benzenesulfen-
amide (3h ) (0.63 mmol) and 0.26 mL of Bu3SnH (285 mg, 0.98
mmol) were converted as described in typical procedure D. A
total of 102 mg (76%) of a mixture of 4h and its double-bond
isomer (ratio: 77/23) was obtained as colorless crystals that
could not be separated. Rf ) 0.18 (P/MTBE ) 96/4). Mp: 34
°C. IR (KBr): ν˜ ) 3337 cm-1 (w, NH), 1686 (s, CdO), 1246 (s,
COC). 1H NMR: δ ) 0.81 (d, J ) 6.7 Hz, 3 H), 0.86 (d, J ) 6.2
Hz, 3 H), 1.38 (s, 9 H), 1.64 (s, 3 H), 1.74-1.83 (m, 1 H), 3.49
(d, J ) 6.0 Hz, 1 H), 4.53 (br s, 1 H), 4.73-4.81 (m, 2 H). 13C
NMR: δ ) 19.1, 19.9, 22.3, 28.3, 29.5, 45.3, 79.0, 111.7, 144.3.
N-ter t-Bu t yloxyca r b on yl-N-isop r op yl-N-2-p r op en yl-
a m in e (24). A 151 mg portion of N-tert-butyloxycarbonyl-N-
(1,1,2-trimethyl-2-propenyl)benzenesulfenamide (3k ) (0.47
mmol) and 0.20 mL of Bu3SnH (221 mg, 0.76 mmol) were
converted as described in typical procedure D. A total of
72 mg (77%) of 24 was obtained as a colorless oil. Rf ) 0.21
(P/MTBE ) 96/4). IR (film): ν˜ ) 1698 cm-1 (s, CdO), 1272 (s,
96/4). [R]25 ) -11.5 (c ) 2.0, acetone). HPLC: tR ) 11.63,
D
12.30 min. IR (film): ν˜ ) 1702 cm-1 (s, CdO), 1200 (s, COC),
1
856 (s, SN), 739 (s, SC). H NMR: δ ) 1.42 (s, 9 H), 1.62 (d,
J ) 5.3 Hz, 3 H), 3.67 (s, 3 H), 5.01-5.10 (m, 1 H), 5.67 (dd,
J ) 15.5, 6.7 Hz, 1 H), 5.71 (dq, J ) 15.5, 5.3 Hz, 1 H), 7.13-
7.15 (m, 1 H), 7.24-7.28 (m, 4 H). 13C NMR: δ ) 17.7, 27.8,
52.1, 66.4, 82.5, 124.2, 124.7, 126.2, 128.4, 132.7, 139.3, 156.0,
170.7. Anal. Calcd for C17H23NO4S (337.44): C, 60.51; H, 6.87;
N, 4.15. Found: C, 60.29; H, 7.20; N, 4.35.
N-ter t-Bu t yloxyca r b on yl-N-[(E)-1-m et h yl-2-b u t en yl]-
ben zen esu lfen a m id e (23). The reaction was carried out as
described in typical procedure C starting with 179 mg of (E)-
(R)-1-methyl-2-butenyl phenyl sulfide (13) (1.0 mmol), 143 mg
of BocN3 (1.0 mmol), and 12 mg of FeCl2 (0.1 mmol). A total of
97 mg (32%) of 23 was obtained as a colorless oil (P/MTBE )
98.5/1.5 as eluent). Rf ) 0.25 (P/MTBE ) 98.5/1.5). [R]25
)
D
-10.7 (c ) 1.0, acetone). IR (film): ν˜ ) 1699 cm-1 (s, CdO),
1
1
1293 (s, COC), 736 (s, SC). H NMR: δ ) 1.16 (d, J ) 6.8 Hz,
COC). H NMR: δ ) 1.14 (d, J ) 6.8 Hz, 6 H), 1.41 (s, 9 H),
3 H), 1.37 (s, 9 H), 1.52 (d, J ) 5.8 Hz, 3 H), 4.86 (quint, J )
5.8 Hz, 1 H), 5.32-5.58 (m, 2 H), 7.01-7.24 (m, 5 H). 13C
NMR: δ ) 17.5, 18.9, 28.0, 68.0, 81.5, 123.9, 125.6, 126.7,
1.80 (s, 3 H), 4.20 (sept, J ) 6.8 Hz, 1 H), 4.68 (br s, 1 H), 4.90
(br s, 1 H). 13C NMR: δ ) 21.1, 20.3, 27.2, 48.0, 79.2, 113.1,
142.3, 153.8. MS (70 eV): m/z 143 (15) [M+ - C4H8], 98 (15)
[M+ - Boc], 84 (22) [M+ - C4H8 - CO2 - CH3], 57 (100)
[C4H9+].
Hydrolysis of enecarbamate 24 yielded compound 25, the
NMR data of which were in agreement with the literature
values.40
N-ter t-Bu tyloxyca r bon yl-N-(1,1-d im eth yl-2-p r op en yl)-
a m in e (4i).15 Typ ica l P r oced u r e E. A 136 mg portion of
N-tert-butyloxycarbonyl-N-(1,1-dimethyl-2-propenyl)benzene-
sulfenamide (3i) (0.46 mmol), 0.27 mL of triethylamine (189
mg, 1.8 mmol), and 0.12 mL of triethyl phosphite (113 mg,
0.69 mmol) were dissolved in 5 mL of dry CH2Cl2 and refluxed
for 3.5 h. The mixture was poured into 5 mL of water, and the
aqueous layer was extracted with CH2Cl2. The combined
organic layers were washed with aqueous HCl and saturated
aqueous NaHCO3. After drying over MgSO4, the solvent was
removed and the residue was purified by column chromatog-
raphy (P/MTBE ) 96/4). A total of 53 mg (62%) of 4i was
128.4, 131.6, 139.3, 156.5. Anal. Calcd for
C16H23NO2S
(293.43): C, 65.49; H, 7.90; N, 4.77. Found: C, 65.30; H, 8.04;
N, 5.14.
N -t er t -Bu t yloxyca r b on yl-N -(1-m e t h yl-2-p r op e n yl)-
a m in e (4a ).47 Typ ica l P r oced u r e D. A 190 mg portion
of N-tert-butyloxycarbonyl-N-(1-methyl-2-propenyl)benzene-
sulfenamide (3a ) (0.68 mmol), 0.27 mL of Bu3SnH (320 mg,
1.1 mmol), and a catalytic amount of AIBN were dissolved in
50 mL of dry benzene and refluxed for 1 h. The solvent was
removed, and the residue was purified by column chromatog-
raphy (P/MTBE ) 94/4). A total of 108 mg (93%) of 4a was
obtained as a colorless oil. The NMR data were in agreement
with the literature values.47
N-ter t-Bu t yloxyca r b on yl-N-(1-h yd r oxym et h yl-2-p r o-
p en yl)a m in e (4b ).48 A 124 mg portion of N-tert-butyloxy-
carbonyl-N-(1-hydroxymethyl-2-propenyl)benzenesulfenamide
(3b) (0.42 mmol) and 0.19 mL of Bu3SnH (209 mg, 0.71 mmol)
(47) Moriwake, T.; Hamano, S.; Saito, S. Torii, S. J . Org. Chem.
1989, 54, 4114.
(48) Moriwake, T.; Hamano, S.; Saito, S.; Torii, S. Chem. Lett. 1987,
2085.

Fe(II)-Catalyzed Imidation of Allyl Sulfides
J . Org. Chem., Vol. 65, No. 8, 2000 2367
obtained as a colorless oil. Rf ) 0.21 (P/MTBE ) 96/4). 1H
NMR: δ ) 1.32 (s, 6 H), 1.39 (s, 9 H), 4.55 (br s, 1 H), 4.98 (d,
J ) 10.5 Hz, 1 H), 5.04 (d, J ) 17.4 Hz, 1 H), 5.93 (dd, J )
17.4, 10.5 Hz, 1 H). 13C NMR: δ ) 27.8, 28.8, 53.3, 78.9, 111.3,
144.4, 154.8.
dure E. A total of 62 mg (43%) of 4k was obtained as a colorless
oil. Rf ) 0.11 (P/MTBE ) 96/4). IR (film): ν˜ ) 3431 cm-1 (w,
1
NH), 3359 (w, NH), 1723 (s, CdO), 1248 (s, COC). H NMR:
δ ) 1.35 (s, 12 H), 3.29 (d, J ) 9.0 Hz, 1 H), 3.38 (d, J ) 9.0
Hz, 1 H), 4.46 (s, 2 H), 4.94 (br s, 1 H), 5.06 (d, J ) 11.2 Hz,
1 H), 5.07 (d, J ) 17.0 Hz, 1 H), 5.89 (dd, J ) 17.0, 11.2 Hz),
7.25 (s, 5 H, arom. H).13C NMR: δ ) 21.8, 28.3, 56.4, 73.3,
75.8, 79.0, 113.5, 127.5, 127.6, 128.4, 138.0, 141.0, 154.7. MS
(70 eV): m/z 235 (1) [M+ - C4H8], 114 (38) [C6H12NO+], 91
(79) [C7H7+], 57 (100) [C4H9+].
N-ter t-Bu tyloxycar bon yl-N-(1,1,2-tr im eth yl-2-pr open yl)-
a m in e (4j). A 133 mg portion of N-tert-butyloxycarbonyl-N-
(1,1,2-trimethyl-2-propenyl)benzenesulfenamide (3j) (0.43 mmol),
0.27 mL of triethylamine (189 mg, 1.8 mmol), and 0.12 mL of
triethyl phosphite (113 mg, 0.69 mmol) were converted as
described in typical procedure E. A total of 43 mg (50%) of 4j
was obtained as colorless oil, which crystallized slowly. Rf )
0.13 (P/MTBE ) 96/4). Mp: 49 °C. IR (film): ν˜ ) 3332 cm-1
(w, NH), 1698 (s, CdO), 1250 (s, COC), 1164 (s, COC). 1H
NMR: δ ) 1.35 (s, 6 H), 1.39 (s, 9 H), 1.72 (br s, 3 H), 4.56 (br
s, 1 H), 4.80 (br s, 1 H), 4.85 (br s, 1 H). 13C NMR: δ ) 19.0,
27.4, 28.4, 55.5, 78.9, 109.7, 149.7. MS (70 eV): m/z 143 (28)
[M+ - C4H8], 128 (29) [M+ - C4H8 - CH3], 83 (38) [C6H11+],
57 (100) [C4H9+].
N-ter t-Bu tyloxycar bon yl-N-(1-ben zyloxym eth yl-1-m eth -
yl-2-p r op en yl)a m in e (4k ). A 200 mg portion of N-tert-
butyloxycarbonyl-N-(1-benzyloxymethyl-1-methyl-2-propenyl)-
benzenesulfenamide (3k ) (0.5 mmol), 0.32 mL of triethylamine
(222 mg, 2.2 mmol), and 0.14 mL of triethyl phosphite (134
mg, 0.81 mmol) were converted as described in typical proce-
Ack n ow led gm en t. This research project was sup-
ported by the Deutsche Forschungsgemeinschaft (SFB
260 and Graduiertenkolleg “Metallorganische Chemie”)
and by the Fonds der Chemischen Industrie. The skillful
assistance of Stephan Gru¨newald (undergraduate re-
search participant) is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: NMR spectra (1H,
13C) of compounds 1h (mixture of isomers), 1k (mixture of
isomers), 11, 4h (mixture of isomers), 4j, 4k , and 24. This
material is available free of charge via the Internet at
http://pubs.acs.org.
J O991569P