Formation of cyclic phosphonium salts in trichlorosilane reduction of phosphine oxides bearing a pendant hydroxyl group and their hydrolysis to cyclic phosphine oxides

Article abstract of DOI:10.1080/10426500701280137

An unusual ring closure to cyclic phosphonium salts was observed during trichlorosilane reduction of phosphine oxides with a pendant hydroxylmethyl group. Alkaline hydrolysis of the cyclic phosphonium salts afforded a cyclic phosphine oxide and a ring-fis

Full text of DOI:10.1080/10426500701280137

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Formation of Cyclic
Phosphonium Salts in
Trichlorosilane Reduction of
Phosphine Oxides Bearing a
Pendant Hydroxyl Group and
Their Hydrolysis to Cyclic
Phosphine Oxides
Zuo-Gang Huang a , Biao Jiang a & Ke-Jun Cheng a
a CAS-SIOC , Shanghai, China
Published online: 07 Jun 2007.
To cite this article: Zuo-Gang Huang , Biao Jiang & Ke-Jun Cheng (2007) Formation
of Cyclic Phosphonium Salts in Trichlorosilane Reduction of Phosphine Oxides
Bearing a Pendant Hydroxyl Group and Their Hydrolysis to Cyclic Phosphine Oxides,
Phosphorus, Sulfur, and Silicon and the Related Elements, 182:7, 1609-1619, DOI:
10.1080/10426500701280137
To link to this article: http://dx.doi.org/10.1080/10426500701280137
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Phosphorus, Sulfur, and Silicon, 182:1609–1619, 2007
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500701280137
Formation of Cyclic Phosphonium Salts in
Trichlorosilane Reduction of Phosphine Oxides Bearing
a Pendant Hydroxyl Group and Their Hydrolysis to Cyclic
Phosphine Oxides
Zuo-Gang Huang
Biao Jiang
Ke-Jun Cheng
CAS-SIOC, Shanghai, China
An unusual ring closure to cyclic phosphonium salts was observed during
trichlorosilane reduction of phosphine oxides with a pendant hydroxylmethyl group.
Alkaline hydrolysis of the cyclic phosphonium salts afforded a cyclic phosphine ox-
ide and a ring-fission product.
Keywords Alkaline hydrolysis; phosphine oxide; phosphonium salt; trichlorosilane re-
duction
INTRODUCTION
Trichlorosilane is an often-used reducing agent for converting phos-
phine oxides into phosphines.1 Generally, the P-chirogenic relative con-
figuration is retained when a phosphine oxide is reduced by trichlorosi-
lane alone, while the relative configuration is inverted when trichlorosi-
lane is used in combination with an organic base such as triethylamine.2
Phosphine oxides can also be reduced by triethoxysilane or a safer alter-
native, polymethyl-hydrosiloxane (PMHS) with titanium isopropoxide
catalysis.3 It is noteworthy that the phosphine produced by the latter
method may be reacted in situ with an alkyl halide to give a quaternary
phosphonium salt.4 Herein, we report the formation of cyclic phospho-
nium salts in trichlorosilane reduction of phosphine oxides bearing a
pendant hydroxyl group. The reaction possibly involved a reduction step
Received January 29, 2006; accepted January 9, 2007.
We thank National Natural Science Foundation of China and Shanghai Municipal
Committee of Science and Technology for financial support.
Address correspondence to Biao Jiang, State Key Laboratory of Organometallic Chem-
istry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences (CAS-
SIOC), 354 Fenglin Road, Shanghai 200032, China, Fax: +86-21-64166128. E-mail:
jiangb@mail.sioc.ac.cn
1609

1610
Z.-G. Huang et al.
and quaternization of the phosphine intermediate with a neighboring
methylene moiety.
RESULTS AND DISCUSSION
As illustrated in Scheme 1, reduction of phosphine oxides 1 with
trichlorosilane in the presence of triethylamine afforded phosphines
2, which were used as chiral P, N-ligands for asymmetric catalysis.5 We
found that when phosphine oxide 1a containing the pyrrolidinyl group
bearing a pendant free hydroxyl group was subject to reduction, an un-
usual product was isolated and identified as quaternary phosphonium
salt 3a, along with the normal tertiary phophine product 2a.
SCHEME 1
The reaction showed a large tendency to undergo quaternization
at elevated temperature and with prolonged reaction time. The 31P
NMR signals of the phosphine oxide, phosphine and phosphonium salt
were characteristically at about 29, −16, and 10 ppm, respectively. The
31P NMR analysis of samples from different solvents such as xylene,
toluene, benzene, or acetonitrile indicated that 3a was the major prod-
uct along with the yield of 2a less than 10%, while less forcing conditions
(m-xylene, 120◦C, and 6 h in Refs. 5a and 5b) gave 90% yield of 2a. In
the absence of triethylamine, the conversions of 1a to phosphines or
phosphonium salts were incomplete, showing the 31P NMR signals cor-
responding to 1a, 2a and 3a and a peak at -39 ppm (probably indicating
the C-P bond-cleavage Ph2PH).6
After quenching the reaction with aqueous sodium hydroxide, 3a
could be extracted into methylene chloride, purified by column chro-
matography eluting with methylene chloride/methanol, and recrystal-
lized from methylene chloride/petroleum ether. The 1H NMR spectrum
of 3a is somewhat elusive. Signal of one hydrogen atom from four at
3ꢀ and 4ꢀ position on the pyrrolidinyl ring downfield shifts to 4.8 ppm
(Figure 1). The structure is confirmed by X-ray analysis of its single
crystal (CCDC 245589).7 The aza-phospha-six-membered ring has a
partially half chair conformation with C1 locating at the tip position

Trichlorosilane Reduction of Phosphine Oxides
1611
FIGURE 1 Selected 1H NMR Data and X-Ray Structure (Cl− not Shown)
for 3a.
and the phenyl group (C12–C17) projecting at the axial position. In a
mechanistic consideration, though the explicit reaction sequence could
not be depicted at this stage, It is obvious that, as shown in Scheme 2,
the reaction involved reduction of phosphine oxide into tertiary phos-
phine and intramolecular quarternization with the neighboring methy-
lene moiety (probably to be a chlorine-displaced one or in the form of a
siloxy species).8
SCHEME 2
Reduction of 1b gave tertiary phosphine 2b in more than 80% yield.
The formation of 3b was not observed, suggesting that the possible
axial rotamers might not adopt a suitable conformation to undergo
quaternization.9 As for phosphine oxide 1c, the tertiary phosphine 2c
was isolated in about 50% yield, while the yield of quaternary phospho-
nium salt 3c was less than 30% based on 31P NMR spectrum (δ 12.5–
11.5 ppm). However, 3c could not be purified for satisfactory NMR spec-
tra even when the chlorine anion was exchanged by BF4 or PF6 anions.
Its cationic component was confirmed by ESI-HRMS to be 394.1715 in
accordance with the formula [C27H25NP]+ calcd. for 394.1719.

1612
Z.-G. Huang et al.
SCHEME 3
Achiral phosphine oxides 4a, b were also prepared according to the
literature.10 Reduction of 4a did not give any phosphonium product de-
tectable by 31P NMR analysis. Reduction of 4b afforded phosphonium
salt 5b in 75% yield, the characteristic 31P NMR signal of which was at
about +9 ppm (Scheme 3). Beeby and Mann had described the prepara-
tion of cyclic phosphonium bromide 7 from tertiary phosphine 6 bear-
ing an alkyloxy side chain through the sequential dealkyloxy bromina-
tion, biphasic extraction, neutralization and quaternization process.11
Hamanaka et al. reported that active alcohol such as allylic or benzylic
alcohol and unactivated alcohols (even in the form of esters and lac-
tones) could be heated and reacted with the hydrobromic salt of triph-
enylphosphine to form quaternary phosphonium salts.12 Halogenation
and cyclization of phosphine 2d were attempted. Heating of 2d with
reagents such as HCl (concd), SOCl2, P(O)Cl3 or HBr/HOAc, and so on,
only resulted in a complex mixture as indicated by 31P NMR analysis.
The starting material or its oxide 4b were recovered, and 4c with the
hydroxyl group displaced by chlorine was also isolated.
The application of phosphonium salts in phase transfer catalysis is
of interest. We examined the usage of 3a and 5b in reactions such as
epoxidation of chalcone with sodium hypochlorite, Darzens reaction,
alkylation of benzophenone imine of tert-butyl glycine ester and chloro-
form condensation.13 The yields were good, but the enantioselectivities
were very low (typically less than 10% ee).
We noticed that in some cases the phosphonium salts as catalysts
could not be recovered due to degradation under strong basic conditions.
Then the alkaline hydrolysis of 3a and 5b by sodium hydroxide was
investigated.14 Heating the solution of 3a for several hours, by method
A (aq. 2 M NaOH, 100◦C), cyclic phosphine oxide 8a, and ring-cleavage
product 9a were formed in 80% and 10% yields according to 31P NMR.
Using method B (1 M NaOH in water/methanol, v/v = 1/5, 80◦C), 8a and

Trichlorosilane Reduction of Phosphine Oxides
1613
9a were isolated in 49% and 23% yields. As for achiral 5b, the yields
and ratios of 8b and 9b were 50% to 20% by method A, and 43% to 44%
by method B, respectively (Scheme 4).
SCHEME 4
The product distribution and stereoselectivity for hydrolysis of 3a
might be attributed to its rigid conformation.15 The diastereoselectiv-
ity was ca. 5/1 to 7/1 regardless of method A or B. However, obtained
as waxy solids, the configurations of 8a could not be fully defined. The
mechanism of stereoselectivity is much complicate since the hydrol-
ysis involving trigonal bipyramid phosphorus intermediates could be
resulted from facial attacks (via route a, b, c, and d), or attacks from
edge sites and subsequent rearrangements.16 Tentatively, route d would
be least likely because of the crowded triaryl surroundings (Scheme 5),
and attack by hydroxide ion anti to the pseudo axial phenyl group via
route a might be more favorable than route b and c, eventually leading
to (S, Sp)-8a as the major diastereoisomer.
SCHEME 5
It is worthy to note that attempts to prepare 8a,b in an alterna-
tive way were unsuccessful (Scheme 6). Double lithiation of 10a,b by

1614
Z.-G. Huang et al.
SCHEME 6
n-BuLi and reaction with benzenephosphonous dichloride were con-
ducted. Subsequently, trimethylsilyl iodide promoted intramolecular
Michaelis-Arbuzov rearrangement17 of phosphite intermediate 11a,b
was performed, but there were no formation of phosphine oxides 8a,b
as indicated by 31P NMR analysis.
In summary, an unusual ring closure to form cyclic phosphonium
salts in reduction of phosphine oxides bearing a pendant hydroxyl group
was observed. The molecular structure of phosphonium salt 3a was
determined by X-ray diffraction. The alkaline hydrolysis of the cyclic
phosphonium salts were also examined, giving a cyclic phosphine oxide,
and a ring-opened product.
EXPERIMENTAL
Melting points were uncorrected. Specific rotation was recorded on
a PERKIN-ELMER 341 polarimeter.1H NMR (300 MHz, CDCl3), 13C
NMR (75 MHz), and 31P NMR (121 MHz) analyses were performed on
a VARIAN MERCURY 300 spectrometer. IR spectra were recorded on a
BIO-RAD FTS-185 spectrometer. EI MS and HRMS were obtained on
an AGILENT 5973N MSD and an IONSPEC 4.7 TESLA FTMS spec-
trometer. ESI MS were obtained on an APEXIII 7.0 TESLA FTMS spec-
trometer.
Reduction of Phosphine Oxide 1a and 4b
Into an ice-water cooled 100-mL tube with Teflon-tipped valve contain-
ing a solution of the phosphine oxide (1.5 mmol) and triethylamine
(1.1 mL, 8.0 mmol) in dry o-xylene (10 mL) trichlorosilane (0.8 mL, 8
mmol) was added slowly. The slurry in the sealed tube was stirred and
heated at 150◦C overnight. After cooled to 0◦C, the mixture was treated
with 2 M NaOH (50 mL) with caution and stirred until all solids were
dissolved. The mixture was extracted with ether (3×50 mL) and CH2Cl2
(3 × 50 mL), and the combined organic layer was dried over Na2SO4.

Trichlorosilane Reduction of Phosphine Oxides
1615
After filtration and evaporation in vacuo, the residue was purified by
chromatography on silica gel eluting with CH2Cl2/MeOH (v/v = 10/1)
to afford a semi-solid, which was recrystallized from CH2Cl2/petroleum
ether to give the phosphonium salt.
(3aS)-5,5-diphenyl-1,2,3,3a,4-pentahydro-9b-aza-cyclopenta-
[c]phosphinolinium chloride (3a)
95% yield. m.p. 244.4–245.0◦C; [α]D20 –74.5◦ (c 0.62, CHCl3); IR (KBr)
3401, 2868, 1599, 1546, 1492, 1475, 1454, 1437, 1354, 1110, 750 cm−1
;
1H NMR: δ 8.20–8.12 (m, 2H), 7.80–7.50 (m, 9H), 7.11–7.03 (m, 1H),
6.78–6.71 (m, 2H), 4.86–4.76 (dt, J = 14.5, 2 Hz, 1H), 3.67–3.60 (m,
1H), 3.50–3.46 (m, 2H), 3.09–2.97 (m,1H), 2.81–2.73 (m,1H), 2.23–2.09
(m, 2H), 1.93–1.85 (m, 1H); 13C NMR: δ 150.0 (d, J = 5 Hz), 136.4 (d,
J = 2 Hz), 134.7, 134.6 (d, J = 4 Hz), 133.5, 133.4 (d, J = 11 Hz), 133.2
(d, J = 10 Hz), 130.3 (d, J = 14 Hz), 129.9 (d, J = 13 Hz), 120.0 (d, J =
27 Hz), 118.6 (d, J = 27 Hz), 116.4 (d, J = 12 Hz), 114.0 (d, J = 8 Hz),
92.2 (d, J = 92 Hz), 53.2 (d, J = 7 Hz), 47.9, 34.3 (d, J = 15 Hz), 22.6,
22.0 (d, J = 52 Hz); 31P NMR: δ 10.5; ESI MS m/z 344 ([M-Cl]+); HRMS
Calcd. for C23H23NP+ 344.1563, Found 344.1558.
1,1-Diphenyl-4-methyl-2,3-dihydro-4-aza-phosphinolinium
Chloride (5b)
75% yield. m.p. 250.6–251.1◦C; IR (KBr) 3443, 3366, 2920, 1598, 1550,
1505, 1438, 1337, 1109, 1076, 955, 750 cm−1; 1H NMR: δ 7.84–7.76 (m,
6H), 7.71–7.65 (m, 4H), 7.61–7.55 (m,1H), 7.15–7.07 (m,1H), 6.93–6.81
(m, 2H), 3.99–3.95 (m,1H), 3.92–3.87 (m,1H), 3.83–3.76 (m, 2H), 3.15
(s, 3H); 13C NMR: δ 152.7 (d, J = 4 Hz), 136.5 (d, J = 3 Hz), 134.8 (d,
J = 2 Hz), 134.0 (d, J = 7 Hz), 133.4 (d, J = 11 Hz), 130.2 (d, J = 13
Hz), 119.4 (d, J = 88 Hz), 117.5 (d, J = 12 Hz), 114.4 (d, J = 7 Hz), 94.3
(d, J = 90 Hz), 46.8 (d, J = 7 Hz), 40.5, 18.9 (d, J = 53 Hz); 31P NMR: δ
9.3; ESI MS m/z 318 ([M-Cl]+); HRMS Calcd. for C21H21NP+ 318.1406,
Found 318.1394.
2-((2-(Diphenylphosphoryl)phenyl)(methyl)amino)ethanol (4b)
m.p.: 158–160◦C; IR (film) 3215, 3055, 2934, 1586, 1567, 1440, 1286,
1
1172, 1113, 1045, 754, 706, 535 cm−1; H NMR: δ 7.75–7.67 (m, 4H),
7.59–7.53 (m, 7H), 7.51–7.36 (m, 1H), 7.19–7.13 (m, 1H), 7.01 (dd, 1H,
J = 7.3, 13.0 Hz), 6.23 (t, 1H, J = 5.1 Hz), 3.57 (dd, 2H, J = 4.9, 9.4 Hz),
3.04 (t, 2H, J = 4.5 Hz), 1.97 (s, 3H); 13C NMR: δ 159.2 (d, J = 4.0 Hz),

1616
Z.-G. Huang et al.
134.20, 134.04, 133.95, 133.92, 133.30, 131.88, 131.60, 131.46, 131.43,
131.39, 128.44, 128.28, 125.53, 125.52, 125.42, 125.37, 62.0, 59.2, 41.7;
31P NMR: δ +29.8; EIMS: 352 ([M+H]+, 23%), 318 (29%), 242 (100%);
Anal. Calcd. for C21H22NO2P: C, 71.78; H, 6.31; N, 3.99. Found: C, 71.79;
H, 6.30; N, 3.80.
N-(2-Chloroethyl)-2-(diphenylphosphoryl)-N-
methylbenzenamine (4c)
m.p.: 154–155◦C; IR (film) 2960, 2794, 1584, 1568, 1474, 1435, 1180,
1
1118, 934, 753, 696, 537 cm−1; H NMR: δ 7.68–7.61 (m, 4H), 7.51–
7.37 (m, 7H), 7.29–7.24 (m, 1H), 7.10–7.06 (m, 2H), 3.10–3.07 (m, 2H),
3.04–2.98 (m, 2H), 2.42 (s, 3H); 13C NMR: δ 157.96 (d, J = 4.0 Hz),
134.75, 134.59, 134.42, 133.62, 133.59, 133.01, 131.26, 131.21, 131.14,
131.07, 131.04, 130.98, 129.58, 128.22, 128.11, 128.06, 124.85, 124.69,
124.28, 124.18, 59.5, 43.1, 40.6; 31P NMR: δ +26.8; EIMS: 370 ([M+H]+,
22.8%), 372 (7.6%), 334 (7.7%), 318 (23%), 242 (100%); HRMS: [M+H]+
Calcd. for C21H22ClNOP+ 370.1122, Found 370.1122; Anal. Calcd. for
C21H21ClNOP: C, 68.20; H, 5.72; N, 3.79. Found: C, 68.17; H, 5.75; N,
3.48.
Hydrolysis of Phosphonium Salt 3a and 5b
The phosphonium salt (0.7 mmol) was added into 50 mL of 2 M NaOH
or 1 M NaOH in water/MeOH (v/v = 1/5). The mixture was stirred and
refluxed gently for 12 h. After cooled to rt and neutralized with 2 M HCl,
the mixture was extracted with CH2Cl2 (4×50 mL), and the combined
organic layer was dried over Na2SO4. After filtration and evaporation in
vacuo, the residue was purified by chromatography on silica gel eluting
with acetone to give two phosphine oxide products.
(3aS)-5-phenyl-1,2,3,3a,4-pentahydro-9b-aza-cyclopenta-
[c]phosphinoline Oxide (8a)
[α]2D0 −65◦ (c 0.87, CHCl3); IR (film from CDCl3) 3422, 2966, 1710, 1598,
1
1554, 1477, 1439, 1255, 1328, 1173, 1113, 747, 697 cm−1; H NMR:
δ 7.72–7.65 (m, 2H), 7.53–7.43 (m, 3H), 7.38–7.29 (m,1H), 7.24–7.17
(m,1H), 6.66–6.60 (m, 2H), 4.00 (m,1H), 3.54 (m,1H), 3.40 (m,1H), 2.49
(m,1H), 2.34 (m,1H), 2.13 (m,1H), 1.99 (m,1H), 1.75 (m, 2H); 13C NMR:
δ 149.4, 133.5, 133.03, 132.93, 131.73, 131.68, 131.64, 131.60, 131.4,
131.3, 128.5, 128.4, 128.3, 128.27, 116.3, 116.1, 116.0, 115.8, 112.8,
112.7, 112.0, 111.9, 53.7 (d, J = 6 Hz), 47.8, 34.8, 34.3 (d, J = 66 Hz),
22.8; 31P NMR: δ 21.5 for (3aS, 5Sp)-8a and (3aS, 5Rp)-8a at 23.8 ppm

Trichlorosilane Reduction of Phosphine Oxides
1617
could not be fully separated. EI MS m/e 283 (M+, 53%); HRMS Calcd.
for C17H18NOP+ 283.1126, Found 283.1084.
(S)-2-((Diphenylphosphoryl)methyl)-1-phenylpyrrolidine (9a)
m.p. 165.7–165.8◦C; [α]D20 −32◦ (c 1.15, CHCl3); IR (KBr) 2925, 1724,
1
1598, 1506, 1438, 1177, 1118, 744, 692 cm−1; H NMR: δ 7.85–7.70
(m, 4H), 7.61–7.42 (m, 6H), 7.13–7.08 (m, 2H), 6.65–6.60 (m,1H), 6.29–
6.25 (m, 2H), 4.07 (m,1H), 3.36 (m,1H), 3.15 (m,1H), 2.70 (m,1H), 2.25
(m,1H), 2.03 (m, 4H); 13C NMR: δ 145.8, 134.2, 133.32, 133.28, 133.12,
132.07, 132.02, 131.9, 131.83, 131.79, 131.1, 130.9, 130.6, 130.5, 129.2,
128.78, 128.73, 128.58, 128.56, 128.4, 115.7, 111.9, 52.7, 47.4, 31.6, 29.6,
23.0; 31P NMR: δ 30.0; EI MS m/e 361 (M+, 10%); HRMS Calcd. for
C23H25NOP+ ([M+H]+) 362.1668, Found 362.1668.
1-Phenyl-4-methyl-2,3-dihydro-4-phosphinoline Oxide (8b)
IR (film from CDCl3) 3429, 2833, 1598, 1557, 1497, 1431, 1326, 1173,
1115, 954, 753, 696 cm−1; 1H NMR: δ 7.71–7.64 (m, 2H), 7.51–7.37 (m,
5H), 6.76 (m, 2H), 3.81–3.66 (m,1H), 3.61–3.45 (m,1H), 3.05 (s, 3H),
2.51–2.37 (m,1H), 2.32–2.20 (m,1H); 13C NMR: δ 151.1 (d, J = 5 Hz),
133.7, 132.89, 132.87, 132.3, 132.2, 131.05, 131.0, 130.8, 130.7, 127.8,
127.7, 116.6, 116.4, 113.8, 112.5, 112.4, 112.3, 47.6 (d, J = 7 Hz), 39.9,
28.0 (d, J = 67 Hz); 31P NMR: δ 21.6; EI MS m/e 257 (M+, 100%); HRMS
calcd for C15H17NOP+ ([M+H]+) 258.1042, Found 258.1033.
Methylphenylaminoethyl Diphenylphosphine Oxide (9b)
m.p. 107.7–107.9◦C; IR (KBr) 3494, 1598, 1504, 1437, 1355, 1180, 1121,
974, 753, 695; 1H NMR: δ 7.77–7.70 (m, 4H), 7.57–7.45 (m, 6H), 7.19 (m,
2H), 6.72 (m,1H), 6.56 (m, 2H), 3.72 (m, 2H), 2.84 (s, 3H), 2.54 (m, 2H);
13C NMR: δ 147.9, 133.2, 131.93, 131.89, 131.86, 130.6, 130.54, 130.5,
129.2, 128.75, 128.60, 116.78, 112.57, 45.6, 38.0, 26.0 (d, J = 68 Hz); 31
P
NMR: δ 31.7; EI MS m/e 335 (M+, 18%); HRMS Calcd. for C21H23NOP+
([M+H]+) 336.1512, Found 336.1507.
REFERENCES AND NOTES
[1] (a) L. D. Quin, A Guide to Organophosphorous Chemistry, (Wiley, New York, 2000);
b) H.-C. Wu, J.-Q. Yu, and J. B. Spencer, Org. Lett., 6, 4675–4678 (2004).
[2] (a) L. Horner and W. D. Balzer, Tetrahedron Lett., 6, 1157–1162 (1965); (b) K.
Naumann, G. Zon, and K. Mislow, J. Am. Chem. Soc., 91, 7012–7023 (1969).

1618
Z.-G. Huang et al.
[3] N. J. Lawrence, M. D. Drew, and S. M. Bushell, J. Chem. Soc. Perkin Trans., 1,
3381–3391 (1999).
[4] T. Coumbe, N. J. Lawrence, and F. Muhammad, Tetrahedron Lett., 35, 625–628
(1994).
[5] (a) T. Mino, Y. Tanaka, K. Akita, M. Sakamoto, and T. Fujita,Heterocycles, 60, 9–13
(2003); (b) Y. Tanaka, T. Mino, K. Akita, M. Sakamoto, and T. Fujita, J. Org. Chem.,
69, 6679–6687 (2004); An alternative method: (c) B. Jiang, Z.-G. Huang, and K.-J.
Cheng, Tetrahedron: Asymmetry, 17, 942–951 (2006).
[6] (a) J. C. Tebby, Eds., CRC Handbook of Phosphorus-31 Nuclear Magnetic Resonance
Data, (CRC, Boca Raton, 1990); (b) L. J. Higham, E. F. Clarke, H. Muller-Bunz, and
D. G. Gilheany, J. Organomet. Chem., 690, 211–219 (2005).
[7] On a Bruker SMART APEX diffractometer at 293(2) K: crystal size for 3a (mm) 0.466
× 0.256 × 0.243, C23H23NPCl·CH2Cl2 FW 464.77, colorless monoclinic, P2(1), a =
◦
3
˚
˚
9.761(3), b = 10.203(3), c = 12.066(4) A, β = 93.707(6) , V = 1199.1(6) A , Z =
2, Dcalc = 1.287 g/cm3, θ range 1.69–28.31◦, index ranges -12 = h = 12, -13 = k
= 10, -15 = l = 15, λ = 0.71073 A, μ(Mo Kα) = 0.460 mm−1, F(000) = 484, no.
˚
reflns collected/unique 7375/4313, Rint = 0.0541, GOF = 0.858. The final R indices
[I > 2σ(I)]: R1 = 0.0491, wR2 = 0.0906; R indices (all data): R1 = 0.0746, wR2
=
3
˚
0.0985. The largest diff. peak and kole: 0.336, -0.328 e/A . CCDC-245589 contains
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Trichlorosilane Reduction of Phosphine Oxides
1619
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