On the NHC/DBU-Mediated Tosyl Group Transfer to Allenes: Is There an Organocatalytic Role for DBU?

Article abstract of DOI:10.1055/s-0036-1558951

The reactions of allenylphosphonates/allenylphosphine oxides or an allenyl sulfone [4-Cl-C₆H₄-SO₂C(R)=C=CMe₂] with the aldimine PhCH=NTs in the presence of a carbene [NHC·HCl/DBU] afford tosylated allylic phosph

Full text of DOI:10.1055/s-0036-1558951

SYNTHESIS
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0
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9
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8
8
1
1
4
3
7
-
2
1
0
X
©
Georg Thieme Verlag Stuttgart · New York
2017, 49, A–K
A
paper
Synthesis
K. C. Kumara Swamy et al.
Paper
On the NHC/DBU-Mediated Tosyl Group Transfer to Allenes:
Is There an Organocatalytic Role for DBU?
R2
K. C. Kumara Swamy*
A (10 mol%)
DBU (10 mol%)
R2
R3
Ts
R. Rama Suresh
G. Gangadhararao
Mandala Anitha
P
P
R3
•
+
N
R1
Ph
P
toluene, Δ
tosyl transfer
R1
Ts
O
O
O
P
Cl–
or
Ph2P(O)–
A
School of Chemistry, University of Hyderabad, Telangana,
Hyderabad 500046, India
+
N
N
Mes
Mes
kckssc@uohyd.ac.in
Me
.
.
N
Ph
N
H
O
O
O
2:1
toluene
.
.
O
P
P
H
H
O
N
[X-ray]
•
O
r.t., 1 h
Ph
Ph
N
O
O
.
.
P
(
2 equiv)
DBU (1 equiv)
O
(
+ other products)
Received: 12.11.2016
Accepted after revision: 19.01.2017
Published online: 21.02.2017
alyst, the allenoate reacted with two molecules of N-to-
sylated imine to give dihydropyridines 4 with the liberation
of tosylamine.4a In contrast, Lu and co-workers found that
triphenylphosphine catalyzed the reaction of methyl 2,3-
butadienoate with N-tosylated imines leading to pyrroli-
DOI: 10.1055/s-0036-1558951; Art ID: ss-2016-z0794-op
Abstract The reactions of allenylphosphonates/allenylphosphine ox-
ides or an allenyl sulfone [4-Cl-C H -SO C(R)=C=CMe ] with the aldi-
mine PhCH=NTs in the presence of a carbene [NHC·HCl/DBU] afford to-
sylated allylic phosphonates/phosphine oxides or sulfone. This
6
4
2
2
4b
dines 5 via [3 + 2] cycloaddition. If the allene (e.g., 6) had
an α-methyl group, then treatment with N-tosylated imines
a
reaction involves C–S bond formation and not C–O bond formation,
and thus is different from similar reactions of allenes with PhCH=NTs in
the presence of bases like DMAP, DBU or Ph P/(alkyl) P wherein cyc-
in the presence of catalytic DMAP in DMSO afforded the
corresponding Baylis–Hillman adducts 7 (Scheme 1 b).
4c
3
3
When the same reaction was performed in the presence of
tri-n-butylphosphine, [4 + 2] cycloaddition took place to
give tetrahydropyridines 8 in excellent yields and with
complete regioselectivity.4 Panossian et al. accomplished
the synthesis of phosphono-pyrroline 10 and phosphono-
tetrahydropyridine 11 from the reaction of allenylphospho-
nate 9 with N-tosylated imines in the presence of various
trialkylphosphines (Scheme 1 c).5 These allenylphospho-
nates were found to be less reactive when compared to alle-
nyl esters.
loaddition products are generally observed. The reactions of phosphor-
ylated allenes with DBU lead to the unprecedented formation of prod-
ucts in which the DBU ring is cleaved, as evidenced by single crystal X-
ray crystallography. This observation suggests a ‘reactant’ role for DBU
when using this base in the reactions of allenes.
d
Key words allenes, phosphorus, sulfur allenes, N-heterocyclic carb-
enes, tosyl migration, DBU ring cleavage
As allenes are unsaturated hydrocarbons having two cu-
mulative double bonds, the incoming nucleophile can at-
tack any one of the three carbon atoms depending on sub-
The close analogy of an NHC to a phosphine makes the
former valuable as a powerful nucleophile in many synthet-
ically useful reactions. As shown by Hou and co-workers,
reactions of electron-deficient unsaturated compounds (in-
cluding allenes) with N-tosylimines 2 in the presence of a
catalytic amount of the NHC generated from 12a afforded,
rather unexpectedly, the products of tosyl group transfer
13–15 (Scheme 2) in good to high yields, demonstrating a
contrasting (cf. Scheme 1) new reaction pattern for imines
1
stituents. These reactions can also be initiated by a base, a
transition-metal catalyst or an N-heterocyclic carbene
[
(NHC), that could actually act like a base].2,3 In this context,
the reactions of allenes with tosylimines (ArCH=NTs) pro-
vides an interesting case, because in addition to the C=N
double bond that could take part in cycloaddition, the pres-
ence of the lone pair of electrons on nitrogen (a weak do-
nor) can lead to a diverse range of products as shown in
Scheme 1. Shi et al. reported that under DABCO catalysis, N-
tosylated imines 2 undergo [2 + 2] cycloaddition with ethyl
6
as well as for organocatalysis by an NHC. Clearly, these re-
actions are completely different from those shown in
Scheme 1, despite the fact that in both cases a tosylimine
and a base are reacted with an allene. In this context, and in
2,3-butadienoate (1) to afford azetidines 3 (Scheme 1 a).
When 4-dimethylaminopyridine (DMAP) was used as a cat-
©
Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–K

B
Synthesis
K. C. Kumara Swamy et al.
Paper
COR'
H
12a + DBU
(10 mol% each)
DABCO
Ar
R' = OEt
N
CO2Et
Ts
CO2Et
+
ArCH=NTs
Ts
3
[2 + 2]
13
2
Ts
N
1
2a + DBU
H
Ar
Ar
(10 mol% each)
Ts
DMAP
(
a)
•
•
+
ArCH=NTs
+
ArCH=NTs
COR'
R' = OEt
2
CO2Et
1
2
COR'
CO2Et
4
14
Ts
[4 + 2]
Ts
N
12a + DMAP
10 mol% each)
(
Ar
PPh3
+
ArCH=NTs
CO2Me
2
CO2Me
15
R' = OMe
3 + 2]
5
COR'
[
Me
N
NHTs
H
Me
DMAP
+N
R
Ar
•
Cl–
Me
Me
Me
R
COR'
7
(
b)
•
+
ArCH=NTs
Me
COR'
Ts
N
12a
6
2
Ar
P(n-Bu)3
Scheme 2 Tosyl transfer reactions using alkynes, allenes and alkenes
COR'
8
Ts
N
P(n-Bu)3
Ar
R = H
light, the desired product 19 was obtained in a decent yield
(64%) along with the isomer 19′ (14%) (Table 1, entry 1). But
the starting material (the allene) was not consumed com-
R
P(O)(OEt)2
(
c)
•
10
Ts
+
ArCH=NTs
P(O)(OEt)2
9
2
31
pletely ( P NMR evidence). When the reaction was con-
P(n-Bu)3 Ar
N
ducted with DMAP as the base, the yield of 19 increased to
R = Me
91% (Table 1, entry 2). The yield of 19 was reduced to 84%
P(O)(OEt)2
when carbene 12b was used instead of 12a (Table 1, entry
11
3
4
); NHC-3·HCl (12c) was not very effective (Table 1, entry
). The yield of 19 was much better (96%) when the reaction
Scheme 1 Diverse modes of reactivity of allenes with tosylimines
was conducted in toluene at 90 °C using 10 mol% each of
12a and DBU (Table 1, entry 5). Other conditions that we
checked did not result in any increase in the yield of the
product (Table 1, entries 6–9). The reaction using sodium p-
toluenesulfinate under other conditions reported in the lit-
erature14 did not afford any detectable product. It is import-
ant to note that the other possible isomers 19′′ and 19′′′
were not observed in these reactions (Figure 2). Thus, the
reaction conditions were optimized to 10 mol% each of 12a
7
continuation of our interest in allene chemistry, we were
curious to know the relative reactivity of allenylphospho-
nates with tosylimines in the presence of DBU. It should be
noted that in the reactions shown in Scheme 2, it is possible
that the proton from the tosylimine can be transferred to
either of the terminal carbon atoms of the allene, and this
was also one of our minor interests. In addition, since DBU
itself is a base, we were curious to know whether it itself
reacts with the allenylphosphonates or not. The results of
these studies are reported herein.
The precursors used in the present study are shown in
Figure 1. The phosphorus-based allenes 16 and 17 were
readily prepared by the reaction of the corresponding
P(III)–Cl precursors with the appropriate propargylic alco-
O
O
O
α
Ph
Ph
O
P
β
γ
R2
P
R2
•
•
R3
R1
R1
R3
7
a,e,8–11
1
2
3
hols.
The reaction of 4-chlorophenylsulfenyl chlo-
R
= H, R = R = Me [16a, δ 8.8]
1
2
3
P
R
= H, R = R = Me [17a, δP 27.1]
12
R1 = R3 = H, R2 = Me [16b, δ 8.9]
R1 = Me, R2 = R3 = H [17b, δ 27.1]
ride with 2-methylbut-3-yn-2-ol in the presence of Et N
P
P
3
1
1
1
1
1
1
2
3
1
2
3
R
R
R
R
R
R
= Me, R = R = H [16c, δP 11.2]
R
= Ph, R = R = H [17c, δP 30.2]
led to an allenylsulfoxide which was oxidized by m-CPBA to
2
3
= Ph, R = R = H [16d, δP 6.6]
13
2
3
give allenylsulfone 18.
= 4-MeC H , R = R = H [16e, δP 7.8]
O
O
6
4
2
3
S
Me
Me
= 4-MeOC6H4, R = R = H [16f, δP 7.5]
Initially, we examined the reaction of allenylphospho-
nate 16a with N-tosyl aldimine 2 in the presence of NHC-
•
2
3
= 4-ClC6H4, R = R = H [16g, δP 6.8]
= 1-naphthyl, R = R = H [16h, δP 8.3]
2
3
Cl
H
18
1·HCl (12a)/DBU in toluene at 60 °C (Scheme 3). To our de-
Figure 1 The allene precursors used in this study
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Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–K

C
Synthesis
K. C. Kumara Swamy et al.
Paper
and DBU with toluene as the solvent and the temperature
being maintained at 90 °C. Similar observations were made
by previous workers also.6a
O
O
O
O
Me
Ts
O
O
P
Me
P
H
H
Under the above optimized conditions, we were able to
generate the tosylated products 19–29 by using allenyl-
phosphonates 16a–h/allenylphosphine oxides 17a–c and
Me
19"
Ts
19"'
Me
not observed
31
N-tosyl aldimine 2 (Scheme 4). The yields and P NMR
Figure 2 The isomers 19′′ and 19′′′ that were not observed in the re-
action
chemical shifts for the products are given in Table 2.
O
Me
Ts
O
O
P
P
Me
Me
O
O
1
2a (10 mol%)
19
P
Me
base (10 mol%)
•
O
+
(HC)Ph NTs
+
H
Me
O
solvent
O
O
2
1
6a
Ts
19'
i-Pr
i-Pr
OH
+
N
N
+
N
+
N
N
I–
Cl–
Cl–
N
Me
i-Pr
i-Pr
NHC-1⋅HCl
2a
NHC-3⋅HCl
12c
NHC-2⋅HCl
1
12b
Scheme 3 Formation of compounds 19 and 19′
O
O
R2
12a (10 mol%)
DBU (10 mol%)
O
O
P
R2
Ts
P
R3
+
N
O
•
O
Ph
toluene
90–100 °C, 12–18 h
R3
R1
1
R1
Ts
6a–h
2
R = H, R = R3 = Me (19)
1
2
1
2
3
R = H, R = Me, R = H (20)
1
2
3
R = Me, R = R = H (21; X-ray)
R = Ph, R = R3 = H (22)
1
2
1
2
3
R = 4-MeC6H4, R = R = H (23)
R = 4-MeOC6H4, R = R3 = H (24)
1
2
R = 4-ClC6H4, R = R3 = H (25)
1
2
R1 = naphthyl, R = R = H (26)
2
3
O
R2
Ph
Ph
1
2a (10 mol%)
Ph
Ph
O
R2
Ts
P
DBU ( 10 mol%)
N
P
+
•
R3
Ph
R3
toluene
R1
80 °C, 12–18 h
R1
Ts
17a–c
2
R1 = H, R2 = R3 = Me (27)
R1 = Me, R2 = R = H (28)
R1 = Ph, R2 = R3 = H (29, X-ray)
3
Scheme 4 Scope of the synthesis of tosylated products from N-tosyl aldimine 2
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D
Synthesis
K. C. Kumara Swamy et al.
Paper
All the above compounds were characterized by IR,
likely because the PCH2 protons of 19′ are diastereotopic
and therefore are magnetically non-equivalent. In addition,
compound 19′ shows two singlets at δ 4.90 and 5.12 corre-
sponding to the olefinic protons. Finally, the X-ray crystal
structure of compound 21, which confirms the formation of
the S-attacked products, was determined (Figure 3). The lo-
cation of the double bond C(7)–C(8) is easily discerned by
the corresponding bond distance of 1.379(4) Å. Even in the
case of phosphine oxides, the structure is similar as shown
for compound 29.15
1
13
31
NMR ( H, C, P) and LC–MS/CHN analyses. The PCH pro-
2
2
tons of 19 appear as a doublet at δ 3.38 ( J
= 20.4 Hz).
P–H
However, the minor isomer 19′ shows primarily a doublet
2
2
of doublets with fine structure at δ 2.59 ( J , JH–H), most
P–H
Table 1 Optimization of the Conditions for the Reaction of Allenyl-
a
phosphonate 16a with Imine 2
Entry NHC salt Base
Solvent
Temp
Yield of Yield of
b b
(
°C)
19
19′
1
2
3
4
5
6
7
8
12a
12a
12b
12c
12a
12b
12a
12a
12b
DBU
toluene
toluene
toluene
toluene
toluene
toluene
THF
60
80
80
80
90
80
60
60
60
64
91
84
35
96
46
63
75
6
14
–
DMAP
DMAP
DMAP
DBU
16
–
–
DBU
54
30
–
DBU
DMAP
DMAP
THF
9
THF
–
a
Other parameters: allene 16a (0.5 mmol), N-tosyl aldimine 2 (0.5 mmol),
NHC salt (10 mol%), base (10 mol%), solvent (0.5 mL), 14 h.
b
31
Based on P NMR analysis (accuracy ±5%).
Figure 3 Molecular structure of compound 21. Selected bond lengths
(
1
Å) with estimated standard deviations given in parentheses: P1–C6
.933(3), C6–C9 1.316(3), C(6)–C(7) 1.714(4), C(7)–C(8) 1.379(4),
Table 2 Details on the Yields and 31P NMR of Tosylated Products 19–
C(7)–S(1) 1.838(3)
2
9
In a manner similar to the above, the reaction of allenyl-
sulfone 18 with aldimine 2 gave the tosylated product 30
Entry
Allene
Producta
Yield (31P NMRb); δ (31P)
isolated (%)
(
Scheme 5). Although the NMR spectra were similar to
1
2
3
4
5
6
7
8
9
16a
16b
16c
16d
16e
16f
19
(96); 79
(92); 84
(55); 43
(76); 63
(89); 66
(93); 67
(74); 63
(63); 47
(92); 78
(98); 88
(76); 66
18.7
18.3
21.7
15.1
15.3
15.4
14.6
15.5
28.7
33.1
32.0
those described above, since in this case the allene is a sul-
fone, we also determined the structure of compound 30 by
X-ray crystallography (Figure 4). It is noteworthy that the
tosyl group (SO C H CH ) has two nucleophilic centers (O
and S), and hence can lead to either the O-addition or the S-
addition product depending upon the substrates.6a Howev-
er, when the substrate is a phosphorylated allene or an alle-
noate, only the S-attacked products are observed.
20
21 (X-ray)
22
2
6
4
3
23
24
16g
16h
17a
17b
17c
25
26
To make the above reactions synthetically useful, we en-
visaged the synthesis of substituted 1,3-butadiene deriva-
tives by subjecting them to Horner–Wadsworth–Emmons
27
10
28
HWE) reactions with various aldehydes.1
6,17
Unfortunately,
(
11
29 (X-ray)
in only one case, using compound 20, were we able to iso-
late the expected product 31 (Scheme 6). In other cases,
a
Although isomers are possible, we isolated a single isomer.
P NMR spectra were recorded at 162 or 202 MHz in CDCl
5%.
b 31
3
. Accuracy is
±
O
O
O
O
12a (10 mol%)
Ts
S
Me
Me
Ts DBU (10 mol%)
S
N
•
+
Me
Ph
toluene (0.25 M)
Cl
H
Cl
100 °C, 12 h
Me
18
2
30 (65%)
Scheme 5 Reaction of allenylsulfone 18 with imine 2
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Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–K

E
Synthesis
K. C. Kumara Swamy et al.
Paper
Ts
Ts
–N
HN
PhCH=NTs
Mes
Mes
2
+
..
N
N
N
N
Ph
Ph
Mes
Mes
.
.
H
N
N
Mes
Mes
I
II
NH
Mes
N+
O
Ph
–
S
+
Me
N
O
Mes
IV
III
–
H+
16a
–
N
O
P
Me
Ts
Mes
+
O
O
N
Me
Ph
–
N
H
Mes
V
VI
+ H+
–
PhCN
O
Me
O
Figure 4 Molecular structure of compound 30. Selected bond lengths
Å) with esds values given in parentheses: C(8)–C(9) 1.332(6), C(7)–
C(8) 1.505(5), S(1)–C(7) 1.791(4), S(2)–C(8) 1.785(4)
N
N
P
Me
(
Mes
Mes
.
.
–
O
Ts
19
Scheme 7 Possible pathway for the formation of compound 19
mixtures of products were obtained (TLC). The identity of
compound 31 was confirmed by NMR ( H, C), LC–MS and
elemental analysis.
1
13
In the reactions shown above, we used DBU as a base.
We were a bit curious because of an earlier result in which
the carbon (of the seven-membered ring), which is β to
both the nitrogen atoms, is fairly reactive.20 Hence we treat-
ed the allenylphosphonate 16d with DBU in toluene
(Scheme 8). Interestingly, the 31P NMR spectrum of the
crude mixture showed peaks at δ 17.7, 19.0, 22.1 and 22.5.
We tried to separate the products by column chromatogra-
phy, and in this process obtained a very small quantity of
A plausible mechanism for the transfer of the tosyl
6a
group based on the available literature is depicted in
Scheme 7. Initially, the imine 2 reacts with the carbene
(
NHC) generated in situ to form the adduct I.18 This is fol-
lowed by proton transfer to provide the intermediate II,
which undergoes dissociation to afford the cation III and
the tosyl anion IV. Anion IV then attacks, via the sulfur at-
om, the allenylphosphonate 16a at the β-position of phos-
phonate and abstracts a proton from III to afford the final
product 19 (via intermediate VI), along with benzonitrile
crystalline 32 [δ 19.1 and 22.0 (showing minor shifts from
P
those in the reaction mixture, probably due to the solvent)],
(
PhCN) and the carbene to complete the catalytic cycle.19 As
far as the allene chemistry is concerned, it is known that in
but good H and C NMR spectra could not be obtained.
Since the crystals were suitable for X-ray diffraction, we ob-
tained the structure which is shown in Figure 5.
1
13
3
a,b
most cases the nucleophiles attack the β-carbon; what is
proposed herein is consistent with allene chemistry. As is
the case with many such studies, we have not attempted to
isolate and reuse the NHC salt; although the turnover num-
bers are not high (10 mol% of carbene is used), the proce-
dure represents a new synthetic methodology.
The formation of compound 32 can be explained by the
3
a
initial attack of DBU on the β-carbon of the allene that
may lead to intermediate VII, which is further neutralized
by subsequent elimination of a proton that may produce in-
termediate VIII (Scheme 9). Next, the lone pair on nitrogen
may initiate the reaction further with another allenylphos-
phonate 16d, which will lead to ionic intermediate IX. In-
termediate IX undergoes cyclization to produce X. Subse-
quent breaking of the C–N bond coupled with proton cap-
ture by nitrogen may finally lead to 32. Some of these
intermediates can be stabilized by the presence of the
phosphoryl (P=O) group. Although our efforts are only par-
tially successful, it must be noted that DBU is a base that is
H
O
H
PhCHO
THF/NaH
Me
O
O
P
Me
Ph
0
°C–r.t., 12 h
Ts
31 (32%)
20
Ts
Scheme 6 Horner–Wadsworth–Emmons (HWE) reaction affording di-
ene 31
3a
commonly used for similar reactions with allenes, and
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F
Synthesis
K. C. Kumara Swamy et al.
Paper
Me
.
.
N
Ph
O
N
O
O
O
H
.
.
P
H
H
N
toluene
r.t., 1 h
O
P
+
•
N
O
Ph
..
O
O
Ph
P
DBU
16d
O
[
32, δp: 19.1, 22.0; X-ray]
Scheme 8 Reaction of allene 16d with DBU
.
.
N
.
.
Ph
P
N
H
H
N
. .
N
. .
N
+
•
O
O
N
.
.
H
P
O
P
Me
VIII
16d
VII
Ph
Ph
16d
Me
.
.
N
.
.
.
.
N
N
Ph
N
.
.
.
.
H
P
P
N
N
P
H
Ph
Me
Me
Ph
Ph
Ph
Ph
P
P
P
X
IX
32
O
O
O
P
P
Scheme 9 A possible pathway for the formation of compound 32
hence a caveat is in order! This observation suggests that in
reactions of allenes DBU may also act as a ‘reactant’ rather
than as an organocatalyst.
ing a SUPERFIT local hot-stage melting point apparatus and are un-
corrected. IR spectra were recorded on a JASCO FT/IR 5300 spectro-
1
13
31
1
photometer. H, C, and P NMR spectra ( H: 400 MHz or 500 MHz;
13
31
C: 100 or 125 MHz; P: 162 or 202 MHz) were recorded using
In summary, the reactions of allenylphosphonates
Bruker 400 or 500 MHz spectrometers in CDCl (unless stated other-
3
(
OCH CMe CH O)P(O)C(R)=C=CR′
(16a–h)/allenylphos-
2
2
2
2
wise), with shifts referenced to SiMe4 (δ = 0) or 85% H PO4 (δ = 0).
3
phine oxides (Ph) P(O)C(R)=C=CR′ (17a–c) and 4-Cl-C H -
2
2
6
4
Mass spectra were recorded using Shimadzu LC MS-2010A equip-
ment. HRMS were obtained using a Bruker maXis ESI-TOF analyzer.
Elemental analyses were carried out on a Perkin-Elmer 240C CHN or a
Thermo Finnigan EA1112 CHNS analyzer.
SO C(R)=C=CMe (18) with the aldimine PhCH=NTs in the
2
2
presence of a carbene (NHC) afforded tosylated allylic phos-
phonates/phosphine oxides 19–29 and sulfone 30. This re-
action involves formation of a C–S bond and not C–O bond
formation. The reaction of a phosphorylated allene with
DBU leads to the unprecedented formation of a product in
which the DBU ring is cleaved. Since DBU as a base is uti-
lized in reactions using allenes, this result should act as a
caveat in such cases.
Tosylated Phosphonates/Phosphine Oxides/Sulfones 19–30
Screening of the Reaction Conditions
To a 25 mL round-bottomed flask was added compound 12a–c (10
21
mol%), the allene and the solvent (THF or toluene) (ca. 0.5 mL). DBU
or DMAP (10 mol%) was added and the mixture was stirred at r.t.
(25 °C) for 10 min. Next, N-tosylphenylimine 2 (0.13 g, 0.5 mmol) fol-
lowed by allene 16a (0.11 g, 0.5 mmol) were added and stirring was
All the chemicals used were purchased from Aldrich/Fluka or local
manufacturers, and were used without further purification. Freshly
distilled solvents were used. Melting points were determined by us-
continued at the indicated temperature for 14 h. A small sample of
the reaction mixture was analyzed by P NMR spectroscopy. Other
details are presented in Table 1.
31
©
Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–K

G
Synthesis
K. C. Kumara Swamy et al.
Paper
5
,5-Dimethyl-2-(3-methyl-2-tosylbut-3-en-1-yl)-1,3,2-dioxa-
phosphinane 2-Oxide (19′)
This compound was obtained by using NHC-2·HCl salt 12b instead of
2a (see Table 1, entry 6). The residue, after removing the solvent
1
from the mixture obtained from the reaction of 12b (10 mol%, 0.05
mmol), DBU (10 mol%, 0.05 mmol), allene 16a (0.5 mmol) and 2 (0.5
mmol in toluene, 5 mL), was subjected to column chromatography
(EtOAc–hexane, 1:1.5) to afford the products 19 (28%) and 19′ (40%).
Yield: 0.074g (40%; using 0.50 mmol of allene 16a and NHC salt 12b);
white solid; mp 162–164 °C.
IR (KBr): 2980, 1642, 1595, 1474, 1271, 1144, 1003, 911 cm–1
.
1
H NMR (500 MHz, CDCl ): δ = 1.04 and 1.07 [2 s, 6 H, C(CH ) ], 1.80
3
3 2
[
s, 3 H, =C(CH )], 2.45 (s, 3 H, O SC H CH ), 2.50–2.70 [m, 2 H,
3 2 6 4 3
P(O)CH ], 3.79–3.88 [m, 2 H, OCH (A)], 3.95–3.96 (m, 1 H, CH), 4.09–
2
2
4
.17 [m, 2 H, OCH (B)], 4.90 (s, 1 H, C=CH ), 5.12 (s, 1 H, C=CH ), 7.33
2
A
B
3
3
(d, J
= 8.0 Hz, 2 H, Ar-H), 7.72 (d, J
= 8.0 Hz, 2 H, Ar-H).
H–H
H–H
13
C NMR (125 MHz, CDCl ): δ = 20.7, 21.5, 21.6, 21.7, 21.8 (d, 1JP–C
=
3
1
38.4 Hz, CH ), 32.6 (d, J
= 6.5 Hz, CMe ), 66.5 (s, CH), 75.61 [s,
2
P–C 2
OCH (A)], 75.64 [s, OCH (B)], 121.2, 129.4, 129.7, 133.4, 136.1, 145.2.
Figure 5 Molecular structure of compound 32·n-C H12. Hydrogen at-
oms (except NH) and the solvent molecule are omitted for clarity. Se-
lected bond lengths (Å): P1–C6 1.737(6), C6–C13 1.344(9), C13–C14
2
2
5
1
3
C NMR DEPT (125 MHz, CDCl ): δ = 20.6, 21.50, 21.51, 21.7, 21.8 (d,
3
1J
= 138.5 Hz, CH ), 66.4 (CH), 75.5 [s, OCH (A)], 75.6 [s, OCH (B)],
P–C
2
2
2
1
.535(8), C14–C15 1.504(9), C13–C16 1.434(9), C15–C16 1.383(9),
C15–N1 1.326(8), N1–C21 1.468(8), C21–C22 1.505(9), C22–C23
.514(9), C23–N2 1.467(8), N2–C24 1.338(8), C24–C25 1.500(9),
1
21.1 (=CH ), 129.3, 129.6.
2
31
P NMR (202 MHz, CDCl ): δ = 22.1.
3
1
LC–MS: m/z = 373 [M]+.
Anal. Calcd for C17H25O PS: C, 54.83; H, 6.77. Found: C, 54.92; H, 6.71.
C24–C26 1.379(9), C26–P2 1.745(6)
5
(E)-5,5-Dimethyl-2-(2-tosylbut-2-en-1-yl)-1,3,2-dioxaphosphi-
Optimized Procedure
nane 2-Oxide (20)
To a stirred solution of the NHC salt [12a (10 mol% with respect to the
allene)] in dry toluene (0.5 mL) was added DBU (10 mol% with respect
to the allene), and stirring was continued for 10–15 min at r.t. After
this, N-tosylphenylimine 2 (1.0 mmol) and allenyl phosphonate/sul-
fonyl allene (16a–h, 17a–c or 18) (1.0 mmol) were added and the
mixture was stirred at 90–100 °C for 12–18 h. The solvent was re-
moved using a rotary evaporator and the residue was directly subject-
ed to column chromatography (EtOAc–hexane, 1:1 to 1.5:1) to afford
the pure product.
Yield: 0.30 g (84%; using 1.0 mmol of allene 16b); white solid; mp
108–112 °C.
IR (KBr): 2969, 1642, 1597, 1474, 1252, 1058, 1012, 801, 559 cm–1
.
1
H NMR (500 MHz, CDCl ): δ = 1.00 and 1.05 [2 s, 6 H, C(CH ) ], 2.02
3
3 2
2
[
m, 3 H, =C(CH )], 2.45 (s, 3 H, O SC H CH ), 3.04 [d, J
= 21.6 Hz, 2
3
2
6
4
3
P–H
3
2
H, P(O)CH ], 3.89 [dd→t, JP–H
= JH–H ~11.4 Hz, 2 H, OCH (A)], 4.05
2
2
3
2
[
dd→t, J
= J
~11.0 Hz, 2 H, OCH (B)], 7.14–7.21 (m, 1 H, =C–H),
P–H
H–H
2
3
3
7
.34 (d, J
~8.2 Hz, 2 H, Ar-H), 7.77 (d, J
= 8.2 Hz, 2 H, Ar-H).
H–H
H–H
1
3
C NMR (125 MHz, CDCl ): δ = 15.5 (d, J = 2.7 Hz, =CCH ), 21.3, 21.5
3
P–C
1
3
and 21.6 (2 CH + O SC H CH ), 23.3 (d, J = 138.4 Hz, CH ), 32.5 (d,
3
2
6
4
3
P–C
2
5
,5-Dimethyl-2-(3-methyl-2-tosylbut-2-en-1-yl)-1,3,2-dioxa-
JP–C = 6.6 Hz, CMe ), 75.8, 75.9, 128.3, 129.8, 133.8 (d, J = 10.7 Hz),
2
P–C
phosphinane 2-Oxide (19)
136.4, 142.2 (d, JP–C = 8.7 Hz), 144.3.
Yield: 1.00 g (79%; using 3.37 mmol of allene 16a); white solid; mp
31
P NMR (202 MHz, CDCl ): δ = 18.3.
124–126 °C.
3
LC–MS: m/z = 359 [M + 1]+.
Anal. Calcd for C16 PS: C, 53.62; H, 6.47. Found: C, 53.45; H, 6.51.
IR (KBr): 2967, 1626, 1402, 1277, 1142, 1007, 812 cm–1
.
1
H O
23 5
H NMR (500 MHz, CDCl ): δ = 1.02 and 1.18 [2 s, 6 H, C(CH ) ], 1.96
3
3 2
5
5
[
d, JP–H = 6.0 Hz, 3 H, =C–CH (A)], 2.08 [d,
J
= 4.4 Hz, 3 H, =C–
3
P–H
CH (B)], 2.43 (s, 3 H, O SC H CH ), 3.38 [d, 2JP–H = 20.4 Hz, 2 H,
5,5-Dimethyl-2-(3-tosylbut-3-en-2-yl)-1,3,2-dioxaphosphinane 2-
Oxide (21)
3
2
6
4
3
3
P(O)CH ], 4.04–4.19 [m, 4 H, OCH (A) + OCH (B)], 7.31 (d, JH–H = 8.0
2
2
2
Hz, 2 H, Ar-H), 7.84 (d, JH–H = 8.0 Hz, 2 H, Ar-H).
Yield: 0.154 g (43%; using 1.0 mmol of allene 16c); white solid; mp
1
3
129–131 °C.
C NMR (125 MHz, CDCl ): δ = 21.1, 21.5, 21.8 (O SC H CH ), 23.1
3
2
6
4
3
1
IR (KBr): 3098, 2969, 1593, 1474, 1314, 1271, 1163, 835, 799 cm–1
and 25.3 [2 d, JP–C = 3.0 Hz, 3.3 Hz, =C(CH ) ], 25.5 (d, J = 135.7 Hz,
.
3
2
P–C
CH ), 32.6 (d, J = 6.7 Hz, CMe ), 76.4 [s, OCH (A)], 76.5 [s, OCH (B)],
1
2
P–C
2
2
2
H NMR (500 MHz, CDCl ): δ = 0.89 and 1.04 [2 s, 6 H, C(CH ) ], 1.33–
.39 (m, 3 H, CHCH ), 2.45 (s, 3 H, O SC H CH ), 3.05–3.13 (m, 1 H,
3
3 2
127.0, 128.1 (d, JP–C = 11.2 Hz), 129.6, 139.6, 143.7, 153.5 (d, JP–C = 10.0
1
3 2 6 4 3
Hz).
3
2
CHCH ), 3.62 (dd→t, J
= JH–H ~11.0 Hz, 1 H, OCH H ), 3.76 (dd→t,
A B
3
2
P–H
31
3
3
2
P NMR (202 MHz, CDCl ): δ = 18.7.
JP–H = J
~11.0 Hz, 1 H, OCH H ), 3.91 (dd→t, J = J
~11.4 Hz, 1
~11.4 Hz, 1 H, OCH H ), 6.43–6.44
3
H–H
A
2
B
P–H
H–H
3
LC–MS: m/z = 373 [M + 1]+.
H, OCH H ), 4.05 (dd→t, J = J
C
D
P–H
H–H
C
3
D
(m, 1 H, =CH H ), 6.52–6.53 (m, 1 H, =CH H ), 7.35 (d, J
= 8.0 Hz, 2
A
B
A
B
H–H
Anal. Calcd for C17H25O PS: C, 54.83; H, 6.77. Found: C, 54.75; H, 6.81.
5
3
H, Ar-H), 7.78 (d, J
= 8.0 Hz, 2 H, Ar-H).
H–H
©
Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–K

H
Synthesis
K. C. Kumara Swamy et al.
Paper
1
3
1
C NMR (125 MHz, CDCl ): δ = 17.3 (d, J
= 5.1 Hz, CHCH ), 21.2,
H NMR (500 MHz, CDCl ): δ = 0.88 and 1.10 [2 s, 6 H, C(CH ) ], 2.37
3
P–C
1
3
3
3 2
2
1.5 and 21.6 (2 CH + O SC H CH ), 29.0 (d, J = 135.4 Hz), 32.4 [d,
JP–C = 6.5 Hz, C(CH ) ], 75.8 [d, J = 6.5 Hz, OCH (A)], 75.9 [d, J = 6.4
(s, 3 H, O SC H CH ), 3.74–3.87 [m, 5 H, OCH (A) + OCH ], 4.00 [dd→t,
3
2
6
4
3
P–C
2 6 4 3 2 3
3
3
2
2
JP–H = JH–H ~12.4 Hz, 2 H, OCH (B)], 4.38 [d, JP–H = 22.8 Hz, 1 H,
2
3
2
P–C
2
P–C
Hz, OCH (B)], 127.3 (d, J = 6.3 Hz), 128.7, 129.9, 135.2, 144.9, 147.6
P(O)CH], 6.66–6.69 (m, 3 H, =CH H + Ar-H), 6.85 (s, 1 H, =CH H ),
2
P–C
A
3
B
A
3
B
(d, JP–C = 4.9 Hz).
7.07–7.09 (m, 2 H, Ar-H), 7.15 (d, J
~8.2 Hz, 2 H, Ar-H), 7.55 (d, J
H–H H–H
3
1
~8.2 Hz, 2 H, Ar-H).
P NMR (202 MHz, CDCl ): δ = 21.7.
3
13C NMR (125 MHz, CDCl
SO C H CH ), 32.5 (d, J
): δ = 21.0, 21.5 and 21.6 (2 CH
+
LC–MS: m/z = 360 [M + 1]+.
3
3
1
= 6.7 Hz, CMe ), 40.5 (d, JP–C = 132.9 Hz,
2
6
4
3
P–C
2
Anal. Calcd for C16H23O PS: C, 53.62; H, 6.47. Found: C, 53.75; H, 6.41.
5
PCH), 55.3 (OCH ), 76.4 [d, J = 6.6 Hz, OCH (A)], 76.6 [d, J = 6.9 Hz,
3
P–C
2
P–C
This compound was crystallized from a mixture of EtOAc, hexane and
traces of CH Cl at 30 °C.
OCH (B)], 124.2 (d, J = 7.3 Hz), 128.4, 128.5 (d, JP–C = 5.8 Hz), 129.5,
2 P–C
2
2
130.1 (d, JP–C = 6.5 Hz), 133.9 (d, JP–C = 2.0 Hz), 135.7, 144.4, 145.9,
59.2 (d, JP–C = 2.7 Hz).
1
5
,5-Dimethyl-2-(1-phenyl-2-tosylallyl)-1,3,2-dioxaphosphinane 2-
31
P NMR (202 MHz, CDCl ): δ = 15.4.
3
Oxide (22)
LC–MS: m/z = 451 [M + 1]+.
Yield: 0.106 g (63%; using 0.4 mmol of allene 16d); white solid; mp
Anal. Calcd for C22H27O PS: C, 58.66; H, 6.04. Found: C, 58.71; H, 6.12.
6
188–192 °C.
IR (KBr): 2964, 1597, 1311, 1263, 1157, 1059, 833, 758 cm–1
.
2
-[1-(4-Chlorophenyl)-2-tosylallyl]-5,5-dimethyl-1,3,2-dioxa-
1
H NMR (500 MHz, CDCl ): δ = 0.86 and 1.05 [2 s, 6 H, C(CH ) ], 2.37
3
3
2
phosphinane 2-Oxide (25)
(
s, 3 H, O SC H CH ), 3.80–3.87 [m, 2 H, OCH (A)], 3.96–4.02 [m, 2 H,
2 6 4 3 2
Yield: 0.143 g (63%; using 0.5 mmol of allene 16g); white solid; mp
2
OCH (B)], 4.42 [d, J = 22.8 Hz, 1 H, P(O)CH], 6.72 and 6.88 (2 s, 2 H,
=
2
P–H
1
56–158 °C.
IR (KBr): 2922, 1725, 1603, 1491, 1265, 1156, 1057, 1009, 708 cm–1
1H NMR (500 MHz, CDCl
): δ = 1.00 and 1.12 [2 s, 6 H, C(CH ], 2.39
s, 3 H, O SC H CH ), 3.83–3.90 [m, 2 H, OCH (A)], 4.00–4.06 [m, 2 H,
3
CH ), 7.10–7.27 (m, 7 H, Ar-H), 7.53 (d, JH–H= 8.0 Hz, 2 H, Ar-H).
2
.
1
3
C NMR (125 MHz, CDCl ): δ = 21.0, 21.5, 21.6 [SO C H CH +
3
3
2
6
4
1
3
)
3 2
C(CH ) ], 32.5 (d, J = 6.7 Hz, CMe ), 41.4 (d, JP–C = 131.6 Hz, PCH),
3
2
P–C
2
(
76.5, 76.6, 127.7 (d, JP–C = 2.8 Hz), 128.4, 128.5 (d, JP–C = 2.2 Hz), 128.8
2
6
4
3
2
2
OCH (B)], 4.41 [d, J = 24.0 Hz, 1 H, P(O)CH], 6.74 and 6.88 (2 s, 2 H,
(d, JP–C = 5.8 Hz), 129.0 (d, JP–C = 6.4 Hz), 129.5, 132.4 (d, JP–C = 7.5 Hz),
2
P–H
=
CH and =CH ), 7.10–7.54 (m, 8 H, Ar-H).
135.6, 144.4, 145.6.
A B
13C NMR (125 MHz, CDCl
): δ = 21.0, 21.5 [O
SC
H
CH
+ C(CH
)
],
31
3
2
6
4
3
3
2
P NMR (202 MHz, CDCl ): δ = 15.1.
3
1
32.5 (d, JP–C = 6.7 Hz, CMe ), 40.8 (d, JP–C = 132.0 Hz, PCH), 76.5
2
LC–MS: m/z = 421 [M + 1]+.
[
OCH (A)], 76.6 [OCH (B)], 128.4, 128.6 (d, J = 2.2 Hz), 128.9 (d, JP–C
=
2 2 P–C
Anal. Calcd for C21H25O PS: C, 59.99; H, 5.99. Found: C, 59.86; H, 5.41.
5.7 Hz), 129.6, 130.4 (d, JP–C = 6.6 Hz), 131.0 (d, JP–C = 6.8 Hz), 133.9,
35.5, 144.8, 145.4.
5
1
5
,5-Dimethyl-2-[1-(p-tolyl)-2-tosylallyl]-1,3,2-dioxaphosphinane
31
P NMR (202 MHz, CDCl ): δ = 14.6.
3
2
-Oxide (23)
LC–MS: m/z = 457 (37Cl) [M + 1] , 455 (35Cl) [M + 1]+.
+
Yield: 0.226 g (66%; using 0.79 mmol of allene 16e); white solid; mp
56–158 °C.
Anal. Calcd for C21H24ClO PS: C, 55.45; H, 5.32. Found: C, 55.36; H,
5
1
5.38.
IR (KBr): 3027, 2963, 1597, 1512, 1267, 1059, 771 cm–1
.
1
H NMR (500 MHz, CDCl ): δ = 0.88 and 1.11 [2 s, 6 H, C(CH ) ], 2.27
3
3
2
5,5-Dimethyl-2-[1-(naphthalen-1-yl)-2-tosylallyl]-1,3,2-dioxa-
phosphinane 2-Oxide (26)
(s, 3 H, C H CH ), 2.37 (s, 3 H, O SC H CH ), 3.75–3.88 [m, 2 H,
6 4 3 2 6 4 3
2
OCH (B)], 3.95–4.02 [m, 2 H, OCH (A)], 4.39 [d, JP–H = 22.4 Hz, 1 H,
P(O)CH], 6.69–6.70 (m, 1 H, =CH H ), 6.87–7.16 (m, 7 H, =CH H + Ar-
H), 7.55 (d, J
2
2
Yield: 0.22 g (47%; using 1.0 mmol of allene 16h); white solid; mp
A
B
A
B
1
14–116 °C.
IR (KBr): 3052, 2976, 1595 1455, 1273, 1123, 1059, 808, 666 cm–1
1H NMR (500 MHz, CDCl
): δ = 0.83 and 1.01 [2 s, 6 H, C(CH ], 2.09
= 10.8 Hz, 2 H, OCH (A)],
3
= 8.4 Hz, 2 H, Ar-H).
H–H
.
13
C NMR (125 MHz, CDCl ): δ = 21.0, 21.5 and 21.6 (2 CH
+
=
3
3
1
3
)
3 2
O SC H CH + C H CH ), 32.5 (d, J
1
OCH (B)], 128.4, 128.6 (d, J = 5.9 Hz), 128.8 (d, JP–C = 6.5 Hz), 129.2
= 6.8 Hz, CMe ), 40.9 (d, JP–C
2
6
4
3
6
4
3
P–C
2
3
2
(s, 3 H, O SC H CH ), 3.74 [dd→t, J = J
32.0 Hz, PCH ), 76.5 [d, JP–C = 6.8 Hz, OCH (A)], 76.6 [d, J = 6.6 Hz,
2
6
3
4
3
2
P–H
H–H
2
2
2
P–C
3
3.90 (dd→t, J
= J
~11.4 Hz, 1 H, OCH ), 4.01 (dd→t, J
= J
P–H
H–H
B
P–H H–H
2
P–C
2
~
11.8 Hz, 1 H, OCH ), 5.41 [d, JP–H = 24.0, Hz, 1 H, P(O)CH], 6.66 (d,
(d, JP–C = 2.2 Hz), 129.3 (d, JP–C = 7.4 Hz), 129.5, 135.7, 137.6 (d, JP–C
=
B′
3
JH–H = 8.4 Hz, 2 H, Ar-H), 6.85 (s, 1 H, =CH H ), 7.06 (s, 1 H, =CH H ),
3
.1 Hz), 144.4, 145.7.
A
B
A
B
3
7.19–7.24 (m, 3 H, Ar-H), 7.44–7.61 (m, 4 H, Ar-H), 7.74 (d, J
= 8.0
H–H
31
P NMR (202 MHz, CDCl ): δ = 15.3.
3
3
Hz, 1 H, Ar-H), 8.00 (d, J
= 8.4 Hz, 1 H, Ar-H).
H–H
LC–MS: m/z = 435 [M + 1]+.
Anal. Calcd for C22H27O PS: C, 60.82; H, 6.26. Found: C, 60.75; H, 6.21.
13
C NMR (125 MHz, CDCl ): δ = 21.1, 21.3 and 21.5 [C(CH ) +
3 2
3
1
5
O SC H CH ], 32.5 (d, J
2
6
4
3
P–C
= 6.8 Hz, CMe ), 36.4 (d, JP–C = 135.0 Hz,
2
PCH), 76.3 [d, JP–C = 6.7 Hz, OCH (A)], 76.8 [d, J = 7.0 Hz, OCH (B)],
2
P–C
2
2
-[1-(4-Methoxyphenyl)-2-tosylallyl]-5,5-dimethyl-1,3,2-dioxa-
122.6, 125.1 (d, JP–C = 3.5 Hz), 125.6, 126.5, 127.7, 127.8 (d, JP–C = 5.8
Hz), 128.2 (d, JP–C = 8.7 Hz), 128.3 (d, JP–C = 3.3 Hz), 128.8, 128.9, 129.1
phosphinane 2-Oxide (24)
(
1
d, JP–C = 5.7 Hz), 131.3 (d, JP–C = 6.4 Hz), 133.7 (d, JP–C = 1.5 Hz), 135.3,
43.8, 146.7.
Yield: 0.15 g (67%; using 0.5 mmol of allene 16f); white solid; mp
144–146 °C.
31P NMR (202 MHz, CDCl
LC–MS: m/z = 471 [M + 1]+.
): δ = 15.5.
IR (KBr): 2955, 1615, 1512, 1308, 1269, 1059, 1012, 837, 774 cm–1
.
3
Anal. Calcd for C25H27O PS: C, 63.82; H, 5.78. Found: C, 63.75; H, 5.71.
5
©
Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–K

I
Synthesis
K. C. Kumara Swamy et al.
Paper
1
(
3-Methyl-2-tosylbut-2-en-1-yl)diphenylphosphine Oxide (27)
Yield: 0.332 g (78%; using 1.0 mmol of allene 17a); white solid; mp
88–190 °C.
H NMR (500 MHz, CDCl ): δ = 2.07 and 2.16 [2 s, 6 H, C=C(CH ) ],
3
3 2
3
2
2
7
.45 (s, 3 H, O SC H CH ), 4.58 (s, 2 H, O SCH ), 7.32 (d, J
= 8.4 Hz,
2
6
4
3
2
2
3
H–H
H, Ar-H), 7.57–7.59 (m, 2 H, Ar-H), 7.84 (d, J
= 8.0 Hz, 2 H, Ar-H),
1
H–H
.94–7.96 (m, 2 H, Ar-H).
IR (KBr): 3054, 1617, 1437, 1291, 1188, 1134, 816, 781 cm–1
1
.
13
C NMR (125 MHz, CDCl ): δ = 21.6, 23.5 and 26.0 [C(CH ) +
3 2
H NMR (500 MHz, CDCl ): δ = 1.93 and 2.04 [2 d, 5J
3
~4.0 Hz, 6 H,
P–H
3
O SC H CH ], 56.4 (O SCH ), 127.4, 127.5, 129.6, 129.7, 130.1, 137.8,
2
2
6
4
3
2
2
C(CH ) ], 2.38 (s, 3 H, SO C H CH ), 3.88 [d, JP–H = 12.0 Hz, 2 H,
P(O)CH ], 7.17–7.19 (d, JH–H = 8.0 Hz, 2 H, Ar-H), 7.50–7.56 (m, 8 H,
Ar-H), 7.88–7.92 (m, 4 H, Ar-H).
1
3
2
2
6
4
3
1
39.2, 140.9, 144.1, 159.2.
LC–MS: m/z = 400 (37Cl) [M] , 398 (35Cl) [M]+.
Anal. Calcd for C18H19ClO S : C, 54.19; H, 4.80. Found: C, 54.36; H,
3
2
+
3
C NMR (125 MHz, CDCl ): δ = 21.5 (O SC H CH ), 23.1 and 26.0 [2 d,
4 2
3
2
6
4
3
1
4.75.
JP–C = 2.0 Hz, C(CH ) ], 32.5 (d, J = 53.4 Hz, CH ), 126.9, 128.5 (d,
3
2
P–C
2
JP–C = 9.4 Hz), 129.0 (d, JP–C = 7.6 Hz), 129.4, 131.3 (d, JP–C = 7.3 Hz),
31.9 (d, JP–C = 2.1 Hz), 132.9 (d, JP–C = 78.4 Hz), 139.8, 143.4, 153.7 (d,
JP–C = 6.1 Hz).
1
1-Methyl-4-{[(1E,3Z)-1-phenylpenta-1,3-dien-3-yl]sulfonyl}ben-
zene (31)
3
1
P NMR (202 MHz, CDCl ): δ = 28.7.
To a stirred solution of NaH (0.025 g, 0.636 mmol) in dry THF (5 mL)
at 0 °C was added tosylated compound 20 (0.152 g, 0.424 mmol) and
the reaction mixture was stirred at 0 °C to r.t. for 10 min. To this mix-
ture, benzaldehyde (0.045 g, 0.424 mmol) was added. The contents
3
LC–MS: m/z = 425 [M + 1]+.
Anal. Calcd for C24H25O PS: C, 67.91; H, 5.94. Found: C, 67.85; H, 5.96.
3
were stirred at r.t. for 12 h. H O (5 mL) was added and the aqueous
2
Diphenyl(3-tosylbut-3-en-2-yl)phosphine Oxide (28)
layer thoroughly extracted with Et O (3 × 15 mL). The combined or-
2
Yield: 0.18 g (88%; using 0.5 mmol of allene 17b); white solid; mp
ganic layer was dried over anhyd Na SO , filtered and concentrated to
2 4
120–126 °C.
give the crude product that was subjected to column chromatography
IR (KBr): 3063, 2924, 1595, 1439, 1300, 1263, 1157, 1080, 815 cm–1
.
(hexane–EtOAc, 1:20) to afford the desired product 31.
1
Yield: 0.04 g (32%), gummy solid.
IR (KBr): 3059, 2926, 2305, 1719, 1597, 1302, 814 cm–1
H NMR (500 MHz, CDCl ): δ = 1.22–1.28 (m, 3 H, CHCH ), 2.42 (s, 3 H,
3
3
SO C H CH ), 3.49–3.52 (m, 1 H, CHCH ), 6.29 (s, 1 H, = CH H ), 6.73
.
2
6
4
3
3
A
B
(
1
s, 1 H, = CH H ), 7.23–7.81 (m, 14 H, Ar-H).
1
A
B
H NMR (500 MHz, CDCl ): δ = 2.05 [s, 3 H, =C(CH )], 2.42 (s, 3 H,
3
3
3
3
3
C NMR (125 MHz, CDCl ): δ = 16.8 (d, J
= 2.8 Hz, CHCH ), 21.6
O
2
SC
6
H
4
CH
3
3
), 6.68 (d,
JH–H = 16.4 Hz, 1 H), 6.93 (d, JH–H = 16.4 Hz, 1
3
P–C
3
1
(SO C H CH ), 32.6 (d, JP–C = 66.7 Hz, CH), 127.6 (d, JP–C = 5.7 Hz),
H), 7.15 (d, JH–H = 7.2 Hz, 1 H), 7.29–7.40 (m, 7 H, Ar-H), 7.75–7.77 (m,
2 H, Ar-H).
2
6
4
3
1
28.3, 128.4, 128.8 (d, JP–C = 11.5 Hz), 130.0, 130.4, 130.8 (d, JP–C = 8.7
1
Hz), 131.60 (d, JP–C = 9.0 Hz), 131.63 (d, JP–C = 2.7 Hz), 131.7 (d, J
5
=
13
P–C
C NMR (125 MHz, CDCl ): δ = 14.8, 21.6, 116.7, 126.8, 127.9, 128.6,
3
7.3 Hz), 131.9 (d, JP–C = 2.8 Hz), 135.4, 144.7, 148.7 (d, JP–C = 3.7 Hz).
128.7, 130.0, 136.3, 136.9, 137.2, 137.6, 140.5, 144.0.
LC–MS: m/z = 299 [M + 1]+.
3
1
P NMR (202 MHz, CDCl ): δ = 33.1.
3
LC–MS: m/z = 411 [M + 1]+.
Anal. Calcd for C18H18O S: C, 72.45; H, 6.08. Found: C, 72.35; H, 6.13.
2
Anal. Calcd for C23H23O PS: C, 67.30; H, 5.65. Found: C, 67.42; H, 5.59.
3
2-{(Z)-2-[(3-{(E)-8-[(5,5-Dimethyl-2-oxido-1,3,2-dioxaphosphi-
Diphenyl(1-phenyl-2-tosylallyl)phosphine Oxide (29)
nan-2-yl)(phenyl)methylene]-2-azabicyclo[5.2.0]non-1(7)-en-2-
yl}propyl)amino]-1-phenylprop-1-en-1-yl}-5,5-dimethyl-1,3,2-di-
oxaphosphinane 2-Oxide (32)
Yield: 0.17 g (66%; using 0.5 mmol of allene 17c); white solid; mp
204–206 °C.
IR (KBr): 3061, 1595, 1437, 1312, 1154, 1078, 963 cm–1
Allenylphosphonate 16d (0.204 g, 0.77 mmol) was dissolved in dry
toluene (3 mL). To this was added DBU (0.06 mL, 0.39 mmol) and the
mixture was stirred at r.t. for 1 h. Next, the solution was concentrated
.
1
2
H NMR (500 MHz, CDCl ): δ = 2.25 (s, 3 H, O SC H CH ), 4.70 (d, J
P–H
3
2
6
4
3
=
7
9.6 Hz, 1 H, PCHPh), 6.56 (s, 1 H =CH H ), 6.79–6.98 (m, 7 H, Ar-H),
31
A
B
in vacuo (to ca. 1 mL). The crude mixture showed P NMR peaks at δ
.15 (s, 1 H, =CH H ), 7.19–7.35 (m, 7 H, Ar-H), 7.52–7.58 (m, 3 H, Ar-
A
B
~17.7, 19.0, 22.1 and 22.5. There were some minor variations (within
H), 7.95–8.00 (m, 2 H, Ar-H).
1
1
.5 ppm) depending on the dilution. The H NMR spectrum showed a
13
1
C NMR (125 MHz, CDCl ): δ = 21.5 (O SC H CH ), 45.7 (d, J = 61.7
complicated pattern but two N–H proton signals at δ ~8.90 and δ
3
2
6
4
3
P–C
Hz, CH), 127.0, 127.8, 128.1, 128.20, 128.24, 128.9 (d, JP–C = 11.6 Hz),
29.3, 129.4, 129.8 (d, JP–C = 4.6 Hz), 130.3, 131.0, 131.1, 131.5 (d,
JP–C = 8.7 Hz), 131.7, 132.2, 135.8, 144.2, 147.1.
~8.80 (in 2:1 ratio) suggesting it to be an isomeric mixture. HRMS
+
1
(ESI) of compound 32: m/z [M + Na] calcd for C37H50N O P Na:
2
6 2
703.3042; found: 703.3043. To this isomeric mixture was added n-
3
1
pentane (1 mL) and the mixture was cooled to –4 °C to afford a very
P NMR (202 MHz, CDCl ): δ = 32.0.
3
small quantity of crystals of 32 [main signals: δ 19.1 and 22.0]; the
P
LC–MS: m/z = 473 [M + 1]+.
1
H NMR spectrum was still complicated (see the supporting informa-
Anal. Calcd for C28H25O PS: C, 71.17; H, 5.33. Found: C, 71.25; H, 5.28.
tion). The X-ray crystal structure was determined for one crystal. The
data quality was not good but the structure was clear. The reaction
using 16f and DBU also gave HRMS values consistent with the forma-
3
1
-Chloro-4-[(3-methyl-2-tosylbut-2-en-1-yl)sulfonyl]benzene (30)
Yield: 0.13 g (65%; using 0.5 mmol of allene 18); white solid; mp 180–
84 °C.
IR (KBr): 3005, 1620, 1582, 1396, 1300, 1084, 762 cm–1
31
tion of a similar compound(s) [ P NMR: δ 16.1, 19.6, 22.4 and 22.9;
+
HRMS (ESI): m/z [M + H] calcd for C39H55N O P : 741.3433; found:
1
2
8 2
741.3436], but we were unable to isolate a pure product.
.
©
Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–K

J
Synthesis
K. C. Kumara Swamy et al.
Paper
X-ray Data
(3) (a) Bhuvan Kumar, N. N.; Nagarjuna Reddy, M.; Kumara Swamy,
K. C. J. Org. Chem. 2009, 74, 5395. (b) Chakravarthy, M.; Kumara
Swamy, K. C. Synthesis 2007, 3171. (c) Kumara Swamy, K. C.;
Balaraman, E.; Satish Kumar, N. Tetrahedron 2006, 62, 10152.
Crystallographic data were collected on a Bruker APX-II-SMART or an
OXFORD diffractometer using Mo-Kα radiation (λ = 0.71073 Å) and
have been deposited at the Cambridge Crystallographic Data Centre
(4) (a) Zhao, G.-L.; Huang, J.-W.; Shi, M. Org. Lett. 2003, 5, 4737.
(CCDC). The data can be obtained free of charge from The Cambridge
(b) Xu, Z.; Lu, X. J. Org. Chem. 1998, 63, 5031. (c) Zhao, G.-L.; Shi,
Crystallographic Data Centre via www.ccdc.cam.ac.uk/getstructures.
Structures were solved and refined using standard methods.
22
M. Org. Biomol. Chem. 2005, 3, 3686. (d) Zhu, X.-F.; Lan, J.; Kwon,
O. J. Am. Chem. Soc. 2003, 125, 4716.
(
5) Panossian, A.; Fleury-Brégeot, N.; Marinetti, A. Eur. J. Org. Chem.
Compound 21
2008, 3826.
Empirical formula: C16H24ClO PS; FW = 359.38; crystal system:
monoclinic; space group: P2 /c; a = 9.866(2); b = 11.350(2); c =
5
(6) (a) Chen, D.-D.; Hou, X.-L.; Dai, L.-X. J. Org. Chem. 2008, 73,
1
5578. (b) Liu, H.; Zhang, Q.-M.; Wang, L.; Tong, X. Chem. Eur. J.
3
–3
1
μ
7
0
1
6.641(3) Å; β = 97.82(3)°; V = 1846.1(6) Å ; Z = 4; Dcalc = 1.293 g cm ;
2010, 16, 1968. (c) Zhu, Y.; Lu, W.-T.; Sun, H.-C.; Zhan, Z.-P. Org.
–1
=
0.282 mm
; F(000) = 764; data/restraints/parameters =
Lett. 2013, 15, 4146. (d) Fernández, M.; Uria, U.; Orbe, L.;
Vicario, J. L.; Reyes, E.; Carrillo, L. J. Org. Chem. 2014, 79, 441.
7) (a) Kumar, N. N. B.; Chakravarty, M.; Kumar, N. S.; Sajna, K. V.;
Kumara Swamy, K. C. J. Chem. Sci. 2009, 121, 23; and references
cited therein. (b) Balaraman, E.; Srinivas, V.; Kumara Swamy, K.
C. Tetrahedron 2009, 65, 7603. (c) Sajna, K. V.; Kumara Swamy,
K. C. J. Org. Chem. 2012, 77, 8712. (d) Pavan, M. P.; Reddy, M. N.;
Kumar, N. N. B.; Kumara Swamy, K. C. Org. Biomol. Chem. 2012,
10, 8113. (e) Siva Kumari, A. L.; Srinivas, V.; Kumara Swamy, K.
C. J. Chem. Sci. 2013, 125, 1405. (f) Gangadhararao, G.;
Kotikalapudi, R.; Reddy, M. N.; Kumara Swamy, K. C. Beilstein J.
Org. Chem. 2014, 10, 996. (g) Anitha, M.; Gangadhararao, G.;
Kumara Swamy, K. C. Org. Biomol. Chem. 2016, 14, 3591.
345/0/212; S = 0.835; R1 [I > 2σ (I)] = 0.0658; wR2 (all data) =
.1909; max/min residual electron density = 0.310/–0.296 eÅ . CCDC
516448.
–
3
(
Compound 30
Empirical formula: C18H19ClO S ; FW = 398.90; crystal system: mono-
clinic; space group: P2 /c; a = 26.477(2); b = 10.3161(8); c =
4
2
1
3
1
3.8248(11) Å; β = 103.977(1)°; V = 3664.4(5) Å ; Z = 8; Dcalc = 1.446
–3
–1
g cm ; μ = 0.456 mm ; F(000) = 1664; data/restraints/parameters =
6
0
1
461/0/457; S = 1.145; R1 [I > 2σ (I)] = 0.0761; wR2 (all data) =
.1432; max/min residual electron density = 0.520/–0.415 eÅ . CCDC
516450.
–3
(h) Nagaraju, K.; Kumara Swamy, K. C. Org. Biomol. Chem. 2016,
1
4, 5079. (i) Kumara Swamy, K. C.; Rama Suresh, R.;
Compound 32·n-C H
5
12
Gangadhararao, G.; Anitha, M. Phosphorus, Sulfur Silicon Relat.
Elem. 2016, 191, 1427.
Empirical formula: C42H62N O P ; FW = 752.88; crystal system: tri-
clinic; space group: P-1; a = 9.7795(10); b = 12.6937(13); c =
2
6 2
(
8) (a) Enchev, D. D.; Kirilov, M. Phosphorus, Sulfur Silicon Relat.
Elem. 2005, 180, 2269. (b) Guo, H.; Qian, R.; Guo, Y.; Ma, S. J. Org.
Chem. 2008, 73, 7934.
9) Satish Kumar, N. Ph.D. Thesis; University of Hyderabad: India,
2004.
1
1
8
7.1610(17) Å; α = 101.547(2); β = 102.290(2); γ = 110.168(2)°; V =
864.9(3) Å ; Z = 2; Dcalc = 1.341 g cm ; μ = 0.169 mm ; F(000) =
12; data/restraints/parameters = 6514/5/477; S = 1.145; R1 [I > 2σ
3
–3
–1
(
(
I)] = 0.1226; wR2 (all data) = 0.2646; max/min residual electron den-
–3
sity = 1.008/–1.015 eÅ . CCDC 1516451. The data quality was only
moderate but the structure could be refined readily.
(
(
(
(
10) Fuji, K.; Morimoto, T.; Tsutsumi, K.; Kakiuchi, K. Chem. Commun.
005, 3295.
11) Tang, Y.; Deng, L.; Zhang, Y.; Dong, G.; Chen, J.; Yang, Z. Org. Lett.
005, 7, 1657.
2
2
Acknowledgment
12) Armer, R. E.; Boyd, E. A.; Brookfield, F. A. WO2005121141, 2005;
Chem. Abstr. 2005, 144, 51458
13) (a) Scheufler, F.; Maier, M. E. Eur. J. Org. Chem. 2000, 3945.
We thank the Council of Scientific and Industrial Research (CSIR), De-
partment of Science and Technology (DST-FIST and PURSE), and the
University Grants Commission (UGC-UPE-2; CAS) for financial sup-
port.
(
(
b) Braverman, S.; Lior, Z. Tetrahedron Lett. 1994, 35, 6725.
c) Phani Pavan, M. Ph.D. Thesis; University of Hyderabad: India,
2
010.
14) (a) Chawla, R.; Singh, A. K.; Yadav, L. D. S. Tetrahedron 2013, 69,
720. (b) Núňez, A. Jr.; Martín, M. R.; Fraile, A.; Ruano, J. L. G.
(
(
(
1
Supporting Information
Chem. Eur. J. 2010, 16, 5443.
15) The data for compound 29 was incomplete (see the Supporting
Information), but the structure could be readily solved and
refined: CCDC 1516449.
16) (a) Muthiah, C.; Kumar, K. P.; Kumaraswamy, S.; Kumara
Swamy, K. C. Tetrahedron 1998, 54, 14315. (b) Muthiah, C.;
Kumar, K. P.; Aruna Mani, C.; Kumara Swamy, K. C. J. Org. Chem.
2000, 65, 3733. (c) Chakravarty, M.; Srinivas, B.; Muthiah, C.;
Kumara Swamy, K. C. Synthesis 2003, 2368. (d) Kumara Swamy,
K. C.; Srinivas, V.; Pavan Kumar, K. V. P.; Praveen Kumar, K. Syn-
thesis 2007, 893.
Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0036-1558951.
S
u
p
p
ortioIgnfrm oaitn
S
u
p
p
ortioIgnfrm oaitn
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Paper
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©
Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–K