Synthesis of bispyrrolidines by radical cyclisation of diallylamines using phosphorus hydrides

Article abstract of DOI:10.1055/s-2008-1072789

Sequential radical addition-cyclisation reactions of diallylamines using either hypophosphorous acid or a bisphosphinothioate are shown to afford bispyrrolidines in good to excellent yields. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2008-1072789

2142
LETTER
Synthesis of Bispyrrolidines by Radical Cyclisation of Diallylamines Using
Phosphorus Hydrides
B
ispyrrolidines by
n
Radica
l
Cyc
d
lisation rew F. Parsons,* Anthony Wright
Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
Fax +44(1904)432516; E-mail: afp2@york.ac.uk
Received 6 March 2008
Dedicated to Professor Sir Jack Baldwin F. R. S. on the occasion of his 70th birthday
group have shown, for example, that N-benzoylated dial-
Abstract: Sequential radical addition–cyclisation reactions of dial-
lylamines using either hypophosphorous acid or a bisphosphi-
nothioate are shown to afford bispyrrolidines in good to excellent
yields.
lylamines are efficiently cyclised to give pyrrolidines on
reaction with (EtO)2P(O)H, (EtO)2P(S)H or Ph2P(O)H,
and a radical initiator.6b To apply the radical cyclisation of
diallylamines 2 to the synthesis of bispyrrolidines of type
4 and 6, we report herein novel radical cyclisation reac-
tions using compounds containing two P–H bonds; either
a hypophosphorous acid derivative of type 3 or a bisphos-
phorus hydride of type 5.
Key words: addition reactions, cyclisations, phosphorus, radical
reactions
Bispyrrolidines are an interesting family of compounds
and their synthesis has attracted considerable interest. A
small number of natural alkaloids are bispyrrolidines,1
whereas synthetic bispyrrolidines have been investigated
as potential anticancer agents,2 antiarrhythmic agents,3
complexing agents for metals4 and as ligands, such as bis-
phosphoramide 1, for use in synthesis (Figure 1).5
Preliminary studies concentrated on the reaction of 1
equivalent of hypophosphorous acid, H3PO2, with 2.3
equivalents of diallylamine 2a or 2b using AIBN as the
initiator (Scheme 2). Pleasingly, both reactions gave the
desired bispyrrolidine phosphinic acids, either 8a or 8b,
which, following column chromatography, were isolated
in excellent yields as mixtures of inseparable isomers (the
ratio of pyrrolidine rings with cis vs. trans stereochemis-
1
try was calculated from the H NMR spectra).7,8 Similar
N
N
N
N
O
O
H
H
H
H
P
(CH2)5
P
yields of 8a and 8b were obtained when the reactions were
carried out at room temperature, in the absence of THF,
using Et3B and O2 as the initiator.
N
N
Me
Me
1
Previous work on the double radical addition of H3PO2 or
sodium hypophosphite (H2PO2Na) to C=C bonds has
shown how the ratio of reactants can influence the yields
of products formed from mono- or diaddition.9 As predict-
ed from this work, increasing the number of equivalents of
H3PO2 to the diallylamine resulted in the isolation of the
intermediate phosphinic acid (7a,b). For example, heating
ten equivalents of H3PO2 with one equivalent of diallyl-
Figure 1
With the aim of developing a new, concise, general and
mild synthetic route to bispyrrolidines, with phosphorus-
containing groups linking the two rings, the radical cycli-
sation of diallylamines was investigated using various
phosphorus hydrides (Scheme 1).6 Previous studies in our
OR'
OR'
H
OR'
H
H
P
X
4
P
P
X
2
3
X
N
R
N
N
R
R
N
R
X = O, S
R'
O
R'
O
2a, R = Ts
2b, R = Cbz
2c, R = Boc
R'
O
R'
O
P
X
P
H
H
P
X
PH
X
X
N
R
N
R
5
6
Scheme 1
SYNLETT 2008, No. 14, pp 2142–2146
2
2
.0
8
.2
0
0
8
Advanced online publication: 07.05.2008
DOI: 10.1055/s-2008-1072789; Art ID: D07408ST
© Georg Thieme Verlag Stuttgart · New York

LETTER
Bispyrrolidines by Radical Cyclisation
2143
HO
H
OH
H
H
AIBN, THF
heat
P
P
+
O
N
N
R
O
R
7a,b
(1 equiv)
(2.3 equiv)
2a, R = Ts; 2b, R = Cbz
OH
P
OEt
OEt
H
P
P
O
O
N
N
O
N
N
N
R
R
Ts
Ts
Ts
9
10
8a, 82% (cis/trans = 2.2:1)
8b, 96% (cis/trans = 1.7:1)
Scheme 2
amine 2a and AIBN in THF, followed by esterification of
the phosphinic acids (to aid product isolation/purification)
using EtOCOCl and Et3N,10 gave monosubstituted phos-
phinate 9 in 31% yield (cis/trans = 3.2:1) and disubstitut-
ed phosphinate 10 in only 14% yield (cis/trans = 1.7:1)
after chromatography. Similarly, when ten equivalents of
H3PO2 were treated with one equivalent of diallylamine
2a and Et3B11 at room temperature (in the absence of a sol-
vent), followed by reaction with EtOCOCl and Et3N,
phosphinate 9 was isolated in 41% yield (cis/
trans = 2.8:1) and phosphinate 10 in only 6% yield (cis/
trans = 1.4:1).
Ph
OR
OBu
CH2(OEt)2
OR
CH2(OEt)2
P
X
H
P
P
O
N
N
O
Ts
Ts
12a, R = Et
12b, R = H
15a, X = S
15b, X = O
11a, R = Et
11b, R = H
Figure 2
1. 1,3-propanediol,
DCC, THF, –78 °C
to r.t. (73%)
Ph
O
Ph
O
Ph
OH
H
H
H
P
P
S
P
2. Lawesson's reagent,
toluene, heat (55%)
O
S
An alternative one-pot synthesis of phosphinates 9 and 10
was also developed whereby esterification of H3PO2, fol-
lowed by radical cyclisation, was combined in the same
reaction pot. Hence, H3PO2 (10 equiv) was heated with di-
ethoxy dimethylsilane, (EtO)2SiMe2 (15 equiv),12 in THF.
After heating for two hours, the crude solution of ethyl
phosphinate, H2PO(OEt), was cooled to room temperature
and diallylamine 2a (1 equiv) and Et3B added. Following
workup and chromatography, phosphinate 9 was isolated
in 43% yield (cis/trans = 1.6:1) and disubstituted phosph-
inate 10 in 22% yield (cis/trans = 3.2:1). It is noted that
the reaction of phosphinates, such as H2PO(OEt), with
two C=C bonds, to form disubstituted products, has been
described as being generally inefficient and low-yield-
ing.6l
14
13
AIBN,
THF, heat
Ph
Ph
N
R
O
O
P
P
S
(2 equiv)
S
N
R
N
R
2a, R = Ts
2c, R = Boc
16a, R = Ts; 75% (cis/trans = 2.5:1)
16b, R = Boc; 77% (cis/trans = 2.1:1)
TFA
16c, R = H; 95%
Scheme 3
known to efficiently form 12a (10 equiv),14 followed by
addition of diallylamine 2a (1 equiv) and Et3B gave phos-
phinate 11a in an excellent 90% yield (cis/trans = 5.3:1).
Similarly, reaction of 2a (1 equiv) with phosphinic acid
12b (1.5 equiv) and Et3B in THF gave 11b in an excellent
91% yield (cis/trans = 4.6:1).
In a related one-pot approach, reaction of H3PO2 (1 equiv)
with triethyl orthoformate, (EtO)3CH (2 equiv), in THF–
toluene at room temperature for two hours,13 was used to
form H2PO(OEt), which was immediately reacted with di-
allylamine 2a (4 equiv) and Et3B. Following workup and
chromatography, disubstituted phosphinate 10 was isolat-
ed in 18% yield (cis/trans = 4.3:1) – the only other prod-
uct isolated was phosphinate 11a in 22% yield (cis/
trans = 1.6:1; Figure 2). Similar results were obtained us-
ing diallylamines containing N-Cbz (2b) or N-Boc (2c)
protecting groups.
Our attention then moved to the preparation and radical
reactions of bisphosphorus hydrides of type 5 (Scheme 1).
Hence, novel racemic bisphosphorus hydride 14 was
formed using a DCC-promoted coupling between phen-
ylphosphinic acid 13 (2.1 equiv) and 1,3-propanediol (2
equiv) followed by thionation using Lawesson’s reagent
(Scheme 3). Conversion of the P=O bonds to P=S bonds
was expected to weaken the adjacent P–H bonds,6a,15
thereby producing a more efficient hydrogen-atom donor,
that would react more effectively with a diallylamine.
This proposed change in reactivity was supported by the
results from a model study. When O-butyl phenylphosphi-
nothioate, Ph(BuO)P(S)H (1.3 equiv), was heated with 2a
(1 equiv) and AIBN in THF this gave phosphinothioate
The formation of phosphinate 11a is presumably ex-
plained by the formation and subsequent radical addition
reaction of ethyl (diethoxymethyl)phosphinate (12a). In-
deed, esterification of H3PO2 using (EtO)3CH in the pres-
ence of PTSA at room temperature, under conditions
Synlett 2008, No. 14, 2142–2146 © Thieme Stuttgart · New York

2144
A. F. Parsons, A. Wright
LETTER
H
N
H
N
O
P
OH
1. (COCl)2, DMF,
CH2Cl2
O
P
3
O
O
N
N
2. 1,3-propanediol,
Et3N, DMAP, THF
Cbz
Cbz
8b
P
3. H2, 10% Pd/C,
EtOH–AcCl
O
N
H
N
H
17, 63%
Scheme 4
OH
OH
H
H
AIBN, THF
P
P
+
heat
O
O
EtO2C
CO2Et
EtO2C
CO2Et
EtO2C
CO2Et
(1 equiv)
(2.3 equiv)
96% (cis/trans = 6.1:1)
Scheme 5
15a in an excellent 83% yield (cis/trans = 3:1; Figure 2). attractive alternative to traditional approaches (e.g., using
In comparison, when butyl phenylphosphinate, toxic metal hydrides, such as Bu3SnH) and the use of se-
Ph(BuO)P(O)H, (1.3 equiv) was treated with 2a under the quential cyclisations may find application in the prepara-
same conditions, phosphinate 15b was isolated in only tion of target molecules with alternative ring systems, as
47% yield (cis/trans = 3.5:1). Even when using five illustrated in Scheme 5.
equivalents of Ph(BuO)P(O)H to one equivalent of 2a
(under the same conditions), phosphinate 15b was only
isolated in 72% yield.
Acknowledgment
We thank Dr. Alastair Marrion for his time, expertise, and the hel-
pful discussions during the course of the project. We thank the Uni-
versity of York for funding.
Gratifyingly, heating bisphosphinothioate 14 (1 equiv)
with 2a (2 equiv) and AIBN in THF gave bispyrrolidine
16a in 75% yield, as a mixture of diastereomers (cis/
trans = 2.5:1) after chromatography (Scheme 3).16 Simi-
References and Notes
larly, reaction of 14 (1 equiv) with 2c (2 equiv) and
AIBN, under the same reaction conditions, gave 16b in
77% yield (cis/trans = 2.1:1). Surprisingly, no monopyr-
rolidine adduct could be detected from either of the radi-
cal reactions. Biscarbamate 16b was subsequently
deprotected using TFA in CH2Cl2 (0 °C to r.t.), to afford
the corresponding bispyrrolidine 16c, in 95% yield.
(1) (a) Dochnahl, M.; Schulz, S. R.; Blechert, S. Synlett 2007,
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The bispyrrolidines prepared in this work are useful build-
ing blocks for the synthesis of oligopyrrolidines, which
are of interest as RNA-binding agents and also, as sub-
units in artificial anion channels.17 For example, reaction
of 8b with oxalyl chloride forms an intermediate phosphi-
nyl chloride, which on treatment with 1,3-propanediol fol-
lowed by N-deprotection gives tetrapyrrolidine 17
(Scheme 4).
In summary, we have developed new and efficient ap-
proaches to bispyrrolidines of type 4 and 6, using radical
addition–cyclisations of diallylamines promoted by hypo-
phosphorous acid or a bisphosphinothioate. Using phos-
phorus hydrides in radical cyclisations of dienes offers an
Synlett 2008, No. 14, 2142–2146 © Thieme Stuttgart · New York

LETTER
Bispyrrolidines by Radical Cyclisation
2145
(6) For recent work on addition reactions of phosphorus-centred
radicals, see: (a) Jessop, C. M.; Parsons, A. F.; Routledge,
A.; Irvine, D. J. Eur. J. Org. Chem. 2006, 1547. (b) Jessop,
C. M.; Parsons, A. F.; Routledge, A.; Irvine, D. Tetrahedron
Lett. 2003, 44, 479. (c) Jessop, C. M.; Parsons, A. F.;
Routledge, A.; Irvine, D. J. Tetrahedron Lett. 2004, 45,
5095. (d) Cho, D. H.; Jang, D. O. Synlett 2005, 59.
(e) Hunt, T. A.; Parsons, A. F.; Pratt, R. J. Org. Chem. 2006,
71, 3656. (f) Montchamp, J.-L. J. Organomet. Chem. 2005,
690, 2388. (g) Leca, D.; Fensterbank, L.; Lacôte, E.;
Malacria, M. Chem. Soc. Rev. 2005, 34, 858. (h) Parsons,
A. F.; Sharpe, D. J.; Taylor, P. Synlett 2005, 2981. (i) Hunt,
T.; Parsons, A. F.; Pratt, R. Synlett 2005, 2978. (j) Healy,
M. P.; Parsons, A. F.; Rawlinson, J. G. T. Org. Lett. 2005, 7,
1597. (k) Carta, P.; Puljic, N.; Robert, C.; Dhimane, A.-L.;
Fensterbank, L.; Lacôte, E.; Malacria, M. Org. Lett. 2007, 9,
1061. (l) Montchamp, J.-L.; Antczak, M. I. Synthesis 2006,
3080. (m) Healy, M. P.; Parsons, A. F.; Rawlinson, J. G. T.
Synlett 2008, 329. (n) Beaufils, F.; Dénès, F.; Renaud, P.
Angew. Chem. Int. Ed. 2005, 44, 5273.
CDCl3): d = 39.6. ESI-MS: m/z (%) = 316 (100), 567 (92)
[M – H+]. ESI-HRMS: m/z calcd for C26H37N2O6PS2:
567.1758; found: 567.1752.
(9) (a) Williams, R. H.; Hamilton, L. A. J. Am. Chem. Soc. 1955,
77, 3411. (b) Nifant’ev, E. E.; Magdeeva, R. K.;
Shchepet’eva, N. P. J. Gen. Chem. USSR 1980, 50, 1416.
(c) Dubert, O.; Gautier, A.; Condamine, E.; Piettre, S. R.
Org. Lett. 2002, 4, 359.
(10) Froestel, W.; Mickel, S. J.; Hall, R. G.; von Sprecher, G.;
Strub, D.; Baumann, P. A.; Brugger, F.; Gentsch, C.; Jaekel,
J.; Olpe, H.-R.; Rihs, G.; Vassout, A.; Waldmeier, P. C.;
Bittiger, H. J. Med. Chem. 1995, 38, 3297.
(11) In the absence of AIBN or Et3B, pyrrolidine products were
formed in low yields after extended reaction times. For
example, heating 2a (1 equiv) with H3PO2 (4.3 equiv) in
degassed dioxane for 3 d, followed by esterification, gave a
4.7:1 mixture of 9 and 10, respectively, in a combined yield
of only 34%.
(12) (a) Deprèle, S.; Montchamp, J.-L. J. Organomet. Chem.
2002, 643-644, 154. (b) Montchamp, J.-L. J. Organomet.
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(7) All new compounds gave spectroscopic data and high-
resolution mass spectrometric data consistent with their
assigned structure.
(8) Bis({4-methyl-1-[(4-methylphenyl)sulfonyl]-3-
pyrrolidinyl}methyl)phosphinic Acid (8a)
(13) (a) Cristau, H.-J.; Coulombeau, A.; Genevois-Borella, A.;
Sanchez, F.; Pirat, J.-L. J. Organomet. Chem. 2002, 643-
644, 381. (b) Deprèle, S.; Montchamp, J.-L. J. Org. Chem.
2001, 66, 6745.
A boiling solution of N,N-diallyl-4-methylbenzenesulfon-
amide (2a, 0.613 g, 2.439 mmol) and hypophosphorous acid
(0.070 g, 1.061 mmol), in anhyd THF (5 mL) was treated
with AIBN (4 × 0.087 g, 4 × 0.531 mmol) over 36 h. After
cooling to r.t., brine (20 mL) was added and the mixture
extracted with CH2Cl2 (3 × 20 mL). The combined layers
were dried (MgSO4), concentrated (under reduced pressure),
and column chromatography [SiO2, PE–EtOAc (4:6) to
EtOAc–MeOH (1:1)] gave phosphinic acid 8a (0.495 g,
82%) as an inseparable mixture of isomers, with a cis/trans
ratio of 2.2:1 (from the 1H NMR spectrum); white solid; mp
118–127 °C. IR (CH2Cl2): nmax = 3541, 3058, 2964, 2882,
1598, 1479, 1454, 1406, 1384, 1337, 1160, 1093, 1044, 955
cm–1.
(14) (a) Gallagher, M. J.; Honegger, H. Aust. J. Chem. 1980, 33,
287. (b) Kehler, J.; Ebert, B.; Dahl, O.; Krogsgaard-Larsen,
P. Tetrahedron 1999, 55, 771.
(15) Bond-dissociation energies based on DFT calculations
(B3LYP functional, 6-13G(d,p) basis set, calculations
performed using Gaussian03) for PhP(S)(OEt)H and
PhP(O)(OEt)H are around 316 and 345 kJ mol–1,
respectively. McGrady, J. E.; Pantazis, D. unpublished
results.
(16) O-(3-{[({4-Methyl-1-[(4-methylphenyl)sulfonyl]-3-pyr-
rolidinyl}methyl)(phenyl)phosphorothioyl]oxy}prop-
yl){4-methyl-1-[(4-methylphenyl)sulfonyl]-3-
pyrrolidinyl}methyl(phenyl)phosphinothioate (16a)
A boiling solution of N,N-diallyl-4-methylbenzene
sulfonamide (2a, 0.372 g, 1.479 mmol) and O-(3-{[phen-
yl(thioxo)phosphoranyl]oxy}propyl)phenylphosphinothioate
(14, 0.264 g, 0.741 mmol) in anhyd THF (15 mL) was
treated portionwise with AIBN (4 × 0.024 g, 4 × 0.148
mmol) over 36 h. After cooling to r.t., 1 M aq NaOH (20 mL)
was added and the mixture extracted with CH2Cl2 (3 × 15
mL). The combined organic layers were dried (MgSO4),
concentrated (under reduced pressure), and column
chromatography [SiO2, CH2Cl2–EtOAc (97:3)] gave
bispyrrolidine 16a (0.477 g, 75%) as an inseparable mixture
of isomers, with a cis/trans ratio of 2.5:1 (from the 1H NMR
spectrum); white solid; mp 61–66 °C. IR (CHCl3):
cis-Diastereomers: 1H NMR (400 MHz, CDCl3): d = 7.72 (d,
J = 8.0 Hz, 4 H, 4 × SCCH, arom), 7.43–7.38 (m, 4 H,
4 × CHCCH3, arom), 3.52 (dd, J = 9.5, 7.5 Hz, 2 H,
2 × CHaHbCHCH2P), 3.36–3.26 (m, 2 H,
2 × CH3CHCHaHb), 3.08–2.95 (m, 4 H,
2 × CHaHbNCHaHbCHCH2P), 2.50–2.30 (m, 2 H,
2 × CHCH2P), 2.43, 2.42 (2 × br s, 6 H, 2 × ArCH3), 2.30–
2.11 (m, 2 H, 2 × CH3CH), 1.47 (dq, J = 15.0, 4.5 Hz, 2 H,
2 × CHaHbP), 1.37–1.10 (m, 2 H, 2 × CHaHbP), 0.68, 0.65 (d
and dd, J = 7.0 Hz and 7.0, 2.5 Hz, 6 H, 2 × CH3CH). 13
NMR (100 MHz, CDCl3): d = 145.0, 144.9 (2 × SCCH,
arom), 135.2, 135.1 (2 × CHCCH3, arom), 130.8
C
(4 × CHCCH3), 128.7, 128.6 (4 × SCCH, arom), 55.6
nmax = 3022, 2967, 2892, 2433, 2401, 2255, 1965, 1919,
(2 × CH3CHCH2), 53.0, 52.7 (br s and d, 3JCP = 5.5 Hz,
1822, 1598, 1479, 1437, 1400, 1385, 1342, 1305, 1289,
2 × CH2CHCH2P), 37.9–37.4 (m, 2 × CHCH2P), 37.7, 37.2
1216, 1160, 1109, 1095, 1041, 1017, 968 cm–1.
(2 × d, 3JCP = 12.0, 10.5 Hz, 2 × CH3CH), 30.3 (br d, 1JCP
89.5 Hz, 2 × CH2P), 21.5 (2 × ArCH3), 13.7, 13.6
(2 × CH3CH).
=
cis-Diastereomers: 1H NMR (400 MHz, CDCl3): d = 7.89–
7.75 (m, 4 H, 4 × PCCH, arom), 7.72–7.66 and 7.62–7.56
(2 × m, 4 H, 4 × SCCH, arom), 7.59–7.51 (m, 2 H,
2 × PCCHCHCH, arom), 7.55–7.41 (m, 4 H, 2 × PCCHCH,
arom), 7.35–7.26 (m, 4 H, 4 × SCCHCH, arom), 4.20–4.04
and 3.75–3.58 (2 × m, 4 H, POCH2CH2CH2), 3.25 (dd, J =
9.5, 6.5 Hz, 2 H, 2 × CH3CHCHaHbN), 3.17 (br t, J = 9.0 Hz,
2 H, 2 × NCHaHbCHCH2P), 3.04–2.94 (m, 2 H,
trans-Diastereomers: 1H NMR (400 MHz, CDCl3):
d = 3.81–3.70 (m, 2 H, 2 × CHaHbCHCH2P), 3.52–3.43 (m,
2 H, 2 × CH3CHCHaHb), 3.08–2.90 (m, 2 H,
2 × CHaHbCHCH2P), 2.73 (br t, J = 9.5 Hz, 2 H,
2 × CH3CHCHaHb), 1.72–1.05 (m, 8 H, 2 × CHCHCH2P),
0.91, 0.87 (d and dd, J = 6.5 Hz and 8.0, 6.5 Hz, 6 H,
2 × CH3CH). 13C NMR (100 MHz, CDCl3): d = 55.7–55.2
(m, 2 × CH3CHCH2), 55.3–54.9 (2 × CH2CHCH2P), 41.9–
41.3 (m, 2 × CH3CHCH), 31.7 (br d, 1JCP = 90.5 Hz,
2 × CH2P), 15.9, 15.8 (2 × CH3CH). 31P NMR (162 MHz;
2 × CH3CHCHaHbN), 2.80–2.67 (m, 2 H,
NCHaHbCHCH2P), 2.56–2.35 (m, 2 H, 2 × CHCH2P), 2.44,
2.42 (2 × s, 6 H, 2 × ArCH3), 2.30–1.96 (m, 2 H,
2 × CH3CH), 2.05–1.65 (m, 4 H, 2 × CH2P), 1.97–1.78 (m, 2
H, POCH2CH2), 0.74, 0.70 (2 × d, J = 7.0, 7.0 Hz) and 0.65–
Synlett 2008, No. 14, 2142–2146 © Thieme Stuttgart · New York

2146
A. F. Parsons, A. Wright
LETTER
trans-Diastereomers: 1H NMR (400 MHz; CDCl3):
d = 3.82–3.68 (m, 2 H, 2 × NCHaHbCHCH2P), 3.56–3.35
(m, 4 H, 2 × CH3CHaHbNCHaHbCHCH2P), 0.91–0.85 and
0.81–0.76 (2 × m, 6 H, 2 × CH3CH). 13C NMR (100 MHz;
CDCl3): d = 53.6–53.3 (m, 2 × CH3CHCH2), 53.4–53.0 (m,
2 × CH2CHCH2P), 40.3–40.1 and 40.0–39.8 (2 × m,
2 × CHCH2P), 40.0–39.6 (m, 2 × CH3CH), 38.9–37.5 (m,
2 × CH2P), 15.6, 15.3 (2 × CH3CH). HRMS–FAB: m/z calcd
for C41H52N2O6P2S4: 859.2256; found: 859.2264.
0.59 (m, 6 H, 2 × CH3CH). 13C NMR (100 MHz, CDCl3):
d = 143.2 (2 × SCCH, arom), 133.8–131.6 (m, 2 × PCCH,
2 × SCCHCHCCH3, arom), 132.5–132.2 (m,
2 × PCCHCHCH, arom), 131.3–129.0 (m, 4 × PCCH,
arom), 129.6, 129.5 (4 × SCCHCH, arom), 128.8–128.4
(4 × PCCHCH, arom), 127.3, 127.2 (4 × SCCH, arom),
60.9–60.2 (m, 2 × POCH2), 54.1, 53.9 (2 × CH3CHCH2N),
51.2, 50.9 (2 × d, 3JCP = 5.5, 8.5 Hz, 2 × CH2CHCH2P), 36.3
(s) and 36.0–35.8 (m) (2 × CHCH2P), 35.7, 35.6 (2 × d,
3JCP = 10.5, 10.5 Hz, 2 × CH3CH), 34.5, 34.3 (2 × d, 1JCP
=
(17) Arndt, H.-D.; Welz, R.; Müller, S.; Ziemer, B.; Koert, U.
Chem. Eur. J. 2004, 10, 3945.
79.5, 80.0 Hz, 2 × CH2P), 31.1–30.7 (m, POCH2CH2), 21.4,
21.4 (2 × ArCH3), 13.2, 13.1 (2 × CH3CH).
Synlett 2008, No. 14, 2142–2146 © Thieme Stuttgart · New York

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