A novel and effective synthetic approach to 9,10-dihydro-9-oxa-10- phosphaphenanthrene-10-oxide (DOPO) derivatives

Article abstract of DOI:10.1080/10426500701407417

DOPO and its derivatives generally exhibit an outstanding performance as flame retardants in various polymers. Starting from trivalent 10-alkoxy-10H-9-oxa-10-phosphaphenanthrenes, a broad range of DOPO derivatives was synthesized via transesterification with aliphatic alcohols and subsequent Michaelis-Arbuzov rearrangement using catalytic amounts of p-toluenesulfonic acid methylester. Due to the considerable differences in the nature of the alcohols employed, several procedures for processing them are presented.

Full text of DOI:10.1080/10426500701407417

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Phosphorus, Sulfur, and Silicon
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A Novel and Effective
Synthetic Approach to
9,10-Dihydro-9-oxa-10-
phosphaphenanthrene-10-
oxide (DOPO) Derivatives
Johannes Artner a , Michael Ciesielski a , Martin
Ahlmann a , Olaf Walter a , Manfred Döring a , Raul
M. Perez b , Volker Altstädt b , Jan K. W. Sandler c
Bernhard Schartel d
&
a Karlsruhe Research Center GmbH , Institute for
Technical Chemistry , Karlsruhe, Germany
b Polymer Engineering , University of Bayreuth ,
Bayreuth, Germany
c BASF Aktiengesellschaft , Ludwigshafen, Germany
d Federal Institute for Materials Research and
Testing , Berlin, Germany
Published online: 16 Jul 2007.
To cite this article: Johannes Artner , Michael Ciesielski , Martin Ahlmann ,
Olaf Walter , Manfred Döring , Raul M. Perez , Volker Altstädt , Jan K. W.
Sandler & Bernhard Schartel (2007) A Novel and Effective Synthetic Approach
to 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) Derivatives,
Phosphorus, Sulfur, and Silicon and the Related Elements, 182:9, 2131-2148, DOI:
10.1080/10426500701407417
To link to this article: http://dx.doi.org/10.1080/10426500701407417

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Phosphorus, Sulfur, and Silicon, 182:2131–2148, 2007
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500701407417
A Novel and Effective Synthetic Approach to
9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide
(DOPO) Derivatives
Johannes Artner
Michael Ciesielski
Martin Ahlmann
Olaf Walter
¨
Manfred Doring
Karlsruhe Research Center GmbH, Institute for Technical Chemistry,
Karlsruhe, Germany
Raul M. Perez
¨
Volker Altstadt
Polymer Engineering, University of Bayreuth, Bayreuth, Germany
Jan K. W. Sandler
BASF Aktiengesellschaft, Ludwigshafen, Germany
Bernhard Schartel
Federal Institute for Materials Research and Testing, Berlin, Germany
DOPO and its derivatives generally exhibit an outstanding performance as flame
retardants in various polymers. Starting from trivalent 10-alkoxy-10H-9-oxa-10-
phosphaphenanthrenes, a broad range of DOPO derivatives was synthesized via
transesterification with aliphatic alcohols and subsequent Michaelis-Arbuzov rear-
rangement using catalytic amounts of p-toluenesulfonic acid methylester. Due to the
considerable differences in the nature of the alcohols employed, several procedures
for processing them are presented.
Keywords DOPO; flame retardant; Michaelis-Arbuzov rearrangement; transesterifica-
tion
Received January 26, 2007; accepted March 9, 2007.
Address correspondence to Manfred Do¨ring, Karlsruhe Research Center GmbH,
Institute for Technical Chemistry, POB 3640, Karlsruhe 76021, Germany. E-mail:
manfred.doering@itc-cpv.fzk.de
2131

2132
J. Artner et al.
INTRODUCTION
Phosphorus is able to form stable compounds with a coordination num-
ber ranging from 1 to 6 and an oxidation state of −III to +V. Con-
sequently, organophosphorus compounds are characterized by an un-
usually large variety of structures and a wide range of uses. They are
commonly found in applications for plant protection, pharmaceutics,
and flame retardancy.1,2
With the increasing use of natural and synthetic polymeric mate-
rials and changing legislation regarding their halogen-based alterna-
tives, phosphorus-based flame retardants are gaining increasing at-
tention. In particular, commercially available 9,10-dihydro-9-oxa-10-
phosphaphenanthrene-10-oxide (DOPO, Figure 1) and its derivatives
were found to exhibit an outstanding performance as flame retardant
components in various polymers.2−4
Commonly, DOPO derivatives are synthesized by nucleophilic reac-
tions of DOPO on activated double bonds (e.g., acrylics5), oxiranes,6
halides (1,7 98), and carbonylic compounds.9 Besides the increase of ap-
plications for DOPO derivatives, limitations of these reactions lead to
a high demand for new possibilities of incorporating this compound in
larger chemical frameworks.
As recently demonstrated by our group, pentavalent DOPO re-
acts with trialkyl orthoformates and a large excess of alkyl alco-
hols under acidic conditions to form trivalent 10-alkoxy-10H-9-oxa-10-
phosphaphenanthrenes.10 Alternatively, these compounds can be syn-
thesized via base-catalyzed alcoholysis of trivalent 10-chloro-10H-9-
oxa-10-phosphaphenanthrene.11,12
Generally alkoxy substituted, trivalent phosphorus derivatives
(phosphites, phosphinous acid esters, and phosphonous acid di-
esters) readily undergo transesterification (e.g., trialkylphosphites,13
methylethylphosphinous acid ethylester,14 alkylphosphonous acid
diethylesters15). Transesterification of the phosphonous acid diesters
10-alkoxy-10H-9-oxa-10-phosphaphenanthrene with aliphatic alcohols
FIGURE 1 DOPO (left), 10-methyl-10H-9-oxa-10-phosphaphenanthrene
(middle), 1 (right).

Novel Synthesis of DOPO Derivatives
2133
has not been described so far. Combined with a subsequent Michaelis-
Arbuzov rearrangement16 using catalytic amounts of a suitable species
(e.g., halides, sulfonates), new opportunities result for the effective
synthesis of DOPO-based flame retardants. This rearrangement has
already been demonstrated by Chernyshev et al. for the conversion
of trivalent 10-methoxy-10H-9-oxa-10-phosphaphenanthrene into 1
(Figure 1), but only by using an equimolar amount of methyl iodide.12
We used these two types of reaction to synthesise a broad range of
chemical compounds containing one or more DOPO subunits. Due to
the considerable differences in the nature of the alcohols used, sev-
eral procedures for processing them are presented. Furthermore, in or-
der to prepare an oligomeric DOPO-based flame retardant, a procedure
for the synthesis of a 1,3,5-tris-(2-hydroxyethyl) cyanuric acid-based
oligomeric compound has been developed.
RESULTS AND DISCUSSION
10-Alkyl-9-oxa-10-phosphaphenanthrene-10-oxides 1–3 were synthe-
sised with a purity exceeding 95% starting from the corresponding
10-alkoxy-10H-9-oxa-10-phosphaphenanthrenes, which were prepared
in a manner recently reported by our group.10 To obtain absolutely
halogen-free products, p-toluenesulfonic acid methylester (0.7 mol. %)
was used instead of the commonly employed alkylhalides (Scheme 1).
The structure of 1 was confirmed by single crystal X-ray diffractome-
try (Figure 2). The torsion angle between the two aromatic rings in 1
C1-C6-C7-C12 of 13.0◦ once again reflects the uniqueness of the ring
system of unmodified DOPO with a corresponding torsion angle of only
2.7◦.17 This fact and the resulting exceptional chemical properties of
DOPO were discussed recently.10
For the synthesis of 10-alkyl-9-oxa-10-phosphaphenanthrene-10-
oxides 4–9, a two-step and one-pot procedure (Scheme 2) was adopted
using 10-alkoxy-10H-9-oxa-10-phosphaphenanthrenes as starting
SCHEME 1 Rearrangement of 10-alkoxy-10H-9-oxa-10-phosphaphenan-
threnes to form 1, 2, and 3; PTSAMe: p-toluenesulfonic acid methylester.

2134
J. Artner et al.
SCHEME 2 Transesterification of 10-ethoxy-10H-9-oxa-10-phosphaphenan-
threne with various aliphatic monoalcohols and subsequent Michaelis-Arbuzov
rearrangement; catalyst for 4, 6 – 9: p-toluenesulfonic acid methylester, for 5:
1-bromo-2-ethyl-hexane.
compounds. In the first step, the alkoxy group was replaced by another
one via non-catalyzed transesterification with a different aliphatic al-
cohol, and the released alcohol was removed in situ by vacuum distil-
lation. For this purpose, an excess of the alcohol had to be used with
low-boiling alcohols, because otherwise this alcohol would have been
removed entirely prior to the completion of the reaction. Furthermore,
10-methoxy-10H-9-oxa-10-phosphaphenanthrene was used because of
the lower boiling point of methanol compared to that of ethanol and
1-propanol.
With high-boiling alcohols, an equimolar amount of 10-ethoxy-10H-
9-oxa-10-phosphaphenanthrene was employed (for a short overview of
the different procedures applied, see Table I). It is worth mentioning
FIGURE 2 Molecular structure of 1 in the crystal; hydrogen atoms are omitted
˚
for clarity; selected bond lengths (A): C13-P1 = 1.753(3), O2-P1 = 1.480(2),
P1-C12 = 1.782(2), C7-C12 = 1.404(3), C6-C7 = 1.483(3), C1-C6 = 1.394(3),
O1-C1 = 1.400(3), P1-O1 = 1.604(2); selected bond angles (◦): O2-P1-C13 =
114.1(1), O2-P1-C12 = 113.1(1), O2-P1-O1 = 114.3(1), O1-P1-C13 = 101.8(1),
O1-P1-C12 = 101.8(1), C13-P1-C12 = 110.6(1), C7-C12-P1 = 117.8(2), C12-C7-
C6 = 120.9(2), C1-C6-C7 = 121.4(2), C6-C1-O1 = 121.5(2), C1-O1-P1 = 119.7(1).

Novel Synthesis of DOPO Derivatives
2135
TABLE I Main Reaction Features Applied for Different Types of
Alcohols
Alcohols used
None
Main reaction features
Synthesised compounds
Rearrangement of
1–3
10-alkoxy-10H-9-oxa-10-
Phosphaphenanthrenesa
Transesterification with
equimolar alcohol
Transesterification of
10-methoxy-10H-9-oxa-
10-Phosphaphenanthrene
with excess alcohol
Longer reaction time for
transesterification,Deficit
alcohol
High-boiling monoalcohols
Low-boiling monoalcohols
4-–8
9
Well miscible polyalcohols
Poorly miscible polyalcohols
10–13b
14, 15
Higher temperature for
transesterification,Deficit
alcohol
aalkoxy = methyl, ethyl, propyl; bMichaelis-Arbuzov rearrangement failed for 10
and 11.
that—as long as the released alcohol could be removed in situ—the spe-
cific 10-alkoxy-10H-9-oxa-10-phosphaphenanthrene applied for trans-
esterification never appeared to change the reaction progress in a per-
ceivable manner.
In the second step, the resulting intermediates were rearranged in
the same way as for the synthesis of 1–3 to yield the products at a purity
exceeding 95%. Only when using 2-ethylhexanol to obtain compound
5, a considerably longer reaction time and larger amounts of catalyst
(1-bromo-2-ethylhexane was used to minimise the by-products) were
required. The strongly decreased reactivity is attributed to steric hin-
drance due to the additional alkyl group in β-position.
For the synthesis of compounds 12–15 (Figure 3), procedures similar
to those described for the processing of the monoalcohols were adopted.
To minimize the by-products arising from the incomplete transester-
ification of the hydroxy groups within the polyalcohols, the reaction
time for this step was extended, and an excess of 10-ethoxy-10H-9-oxa-
10-phosphaphenanthrene was used and removed after the completion
of the reaction by vacuum distillation. Furthermore, the reaction tem-
perature was increased for poorly soluble compounds (e.g., 1,3,5-tris-(2-
hydroxyethyl) cyanuric acid and its oligomeric analogue 16) to achieve a
sufficient solubility. The Michaelis-Arbuzov rearrangement was accom-
plished smoothly and a product purity exceeding 95% was achieved. The

2136
J. Artner et al.
FIGURE 3 Di-, tri-, and oligo-DOPO derivatives 12–15; oligomeric 1,3,5-tris-
(2-hydroxyethyl) cyanuric acid 16; l, m, n = 0, 1, 2. . . ; [a] for reasons of simplicity
and relative frequency, secondary branchings are not plotted.
above procedure using p-toluenesulfonic acid methylester as a catalyst
was applied.
Synthesis of the novel oligomeric 1,3,5-tris-(2-hydroxyethyl) cyanuric
acid-based compound 16 (Figure 3) was accomplished with a sulfonate-
containing cation exchange resin as a catalyst under heat and vacuum.
An immobilised catalyst was chosen, because acidic species strongly
interfere with the transesterification reaction and removal can be per-
formed easily in this way. The reaction was monitored by 1H NMR and
stopped when the CH/OH ratio reached ≈ 7.5 (ratio
= 4). At this
t=0
polymerisation level, a maximum chain length of 6 could be detected
via ESI. The resulting transesterification and rearrangement product
15 was found to have a maximum chain length of 9 using MALDI.
It was intended to synthesise DOPO-containing flame retardants
based on 2,2-dimethyl-1,3-propandiol and trimethylolpropane using

Novel Synthesis of DOPO Derivatives
2137
FIGURE 4 Compounds 10 and 11 that could not be rearranged via Michaelis-
Arbuzov reaction due to steric hindrance.
the approach presented here. Transesterification was accomplished
smoothly when applying the procedures for readily soluble polyols to
yield 10 and 11 (Figure 4) at a purity exceeding 95%. Michaelis-Arbuzov
rearrangement with these compounds failed; 10 was left completely un-
affected and 11 was largely destroyed. This is attributed to steric hin-
drance, which is even larger than in the precursor of 5 and which is
caused by the quaternary carbon atom in β-position.
CONCLUSIONS
A novel and effective synthetic approach to 9,10-dihydro-9-oxa-10-
phosphaphenanthrene-10-oxide derivatives was presented. A broad
range of chemical compounds containing one or more DOPO subunits
was synthesized starting from aliphatic alcohols. Their large multitude
and diversity, in combination with the method presented herein, result
in a large number of alternatives to design such compounds in terms of
synthetic effort or chemical, physical, processing, and flame-retardant
properties.
In the course of the reaction DOPO subunits were introduced at the
hydroxy groups and due to the considerable differences in the nature of
the alcohols used, several procedures for processing them were applied
and presented. The only limitations encountered concerned the steric
hindrance arising from β-branching of the aliphatic alcohols, which
makes difficult or completely inhibits the Michaelis-Arbuzov rearrange-
ment of the trivalent 10-alkoxy-10H-9-oxa-10-phosphaphenanthrene
intermediates. It is assumed that α-branching restricts Michaelis-
Arbuzov rearrangement to an even larger extent.

2138
J. Artner et al.
EXPERIMENTAL
Infrared spectra (IR) were obtained using a Perkin-Elmer system 2000
FT-IR spectrophotometer. Nuclear magnetic resonance (NMR) spec-
tra were recorded with a Bruker AC-250 instrument using tetram-
ethylsilane and trimethylphosphate18 as internal standards. Elemen-
tal analysis was performed with a Vario EL III instrument from El-
ementar Analysensysteme GmbH. Electron impact mass spectrome-
try (MS) was accomplished with a Finnigan MAT-4000-1 spectrometer.
Electron spray ionisation mass spectrometry (ESI) was carried out with
a Hewlett-Packard LC-MSD 1100 instrument. Matrix-assisted laser
desorption/ionisation mass spectrometry (MALDI) was performed with
an Applied Biosystems Voyager DE-STR instrument. Melting points
were obtained with a Bu¨chi B-545 apparatus at a heating rate of
3◦C/min. Purity of the compounds was determined by 1H and 31P NMR
spectroscopy.
X-ray diffractometry (XRD) was performed using a Siemens SMART
CCD 1000 diffractometer with an irradiation time of 10 s to 20 s per
frame, thus collecting a full sphere of data using an ω-scan technique
with ꢀω ranging from 0.3 to 0.45◦. For searches relating to single-crystal
X-ray diffraction data, the Cambridge Structural Database was used.19
Data were corrected for polarization and Lorentz effects, and an experi-
mental absorption correction was performed with SADABS.20 SHELX-
9721 was used for the structure refinement, for graphical evaluation
and visualisation of the data XPMA22 and ORTEP-323 were used.
Structures with more than one DOPO subunits were considered too
complex to be denominated correctly according to IUPAC and just re-
ferred to by their numbers.
Synthesis of Compounds 1—3: General Procedure
10-Alkoxy-10H-9-oxa-10-phosphaphenanthrene [1 mol;
R
=
Me
(230.1 g), Et (244.1 g), Pr (258.1 g)] and p-toluenesulfonic acid
methylester (7 mmol, 1.06 mL) were stirred under argon for 24 h
at 175◦C to yield the corresponding clear, glassy 10-alkyl-9-oxa-10-
phosphaphenanthrene-10-oxide (1–3) in a purity exceeding 95%. Re-
crystallization from ethanol.
Compound 1
M.p. 131◦C (lit: 124–6◦C7). Analfound
: C, 68.67; H, 4.79%.
Analcalc(C13H11O2P): C, 67.83; H, 4.82%. MS (70 eV): m/z = 230, 215,
168. IR (KBr): 3059, 2981, 2919, 1606, 1595, 1581, 1560, 1477, 1446,
1431, 1308, 1272, 1226, 1205, 1171, 1147, 1118 cm−1. 1H NMR (CDCl3):

Novel Synthesis of DOPO Derivatives
2139
δ = 1.78 (d, J = 14.6 Hz, 3H, CH3), 7.18 (d, J = 8.1 Hz, 1H,
PH
HH
O C CH), 7.19 (t, J
= 7.2 Hz, 1H, O C C CH CH), 7.32 (t,
HH
J
HH = 7.6 Hz, 1H, O C CH CH), 7.45 (td, JHH = 7.5 Hz, JPH = 3.0 Hz,
1H, P C CH CH), 7.63 (t, J = 7.8 Hz, 1H, P C C CH CH), 7.81
HH
(dd, J
= 7.3 Hz, J = 13.0 Hz, 1H, P C CH), 7.85 (d, J
=
HH
PH
HH
7.7 Hz, 1H, O C C CH), 7.89 (dd, J = 8.9 Hz, J = 4.7 Hz, 1H,
HH
PH
P C C CH). 13C NMR (CDCl3): δ = 14.6 (J = 100.3 Hz, CH3), 120.3
PC
(J = 5.9 Hz, O C CH), 122.3 (J = 11.3 Hz, O C C), 123.7 (J
=
PC
PC
PC
9.5 Hz, P C C CH), 124.5 (O C C CH CH), 125.0 (O C C CH),
125.6 (J = 123.4 Hz, P C), 128.3 (J = 13.6 Hz, P C CH CH),
PC
PC
129.2 (J = 11.5 Hz, P C CH), 130.4 (O C CH CH), 132.9 (J
=
=
PC
PC
2.3 Hz, P C C CH CH), 134.9 (J = 5.9 Hz, P C C), 148.8 (J
PC
PC
8.0 Hz, O-C). 31P NMR (CDCl3): δ = 36.0. XRD: T = 200(2) K, λ(Mo
˚
Kα) = 0.71073 A, crystal system = monoclinic, space group = P2(1)/n
˚
˚
˚
(No. 14), a = 8.4590(18) A, b = 11.807(3) A, c = 10.853(2) A, β =
92.150(3) , volume = 1083.2(4) A , Z = 4, Dcalc = 1.412 g.cm−3, μ(Mo-Kα)
= 0.233 mm−1, F(000) = 480, crystal size = 0.15 × 0.05 × 0.05 mm3, θ
range = 2.55◦ to 28.46◦, hkl range = −11/11; −15/14; −14/14, reflections
collected = 10488, unique reflections = 2703, Rint = 0.1061, reflections
observed (I > 2σ) = 1361, parameters refined = 149, goodness-of-fit on
◦
3
˚
F2 = 0.854, (ꢀp)max,min = 0.235 and −0.285 e.A−3, final R indices (I >
˚
2σ): R1 = 0.0455; wR2 = 0.0911, R indices (all data): R1 = 0.1196; wR2 =
0.1092.
Compound 2
M.p. 105◦C. Analfound: C, 69.80; H, 5.33%. Analcalc(C14H13O2P): C,
68.85; H, 5.37 %. MS (70 eV): m/z = 244, 216, 215, 168. IR (KBr): 3064,
2979, 2936, 1604, 1595, 1580, 1558, 1479, 1445, 1431, 1379, 1287, 1273,
1239, 1209, 1169, 1145, 1118 cm−1. 1H NMR (CDCl3): δ = 1.11 (td, J
=
HH
7.7 Hz, JPH = 19.5 Hz, 3H, CH3), 2.04 (qd, JHH = 7.7 Hz, JPH = 15.2 Hz,
2H, CH2), 7.18 (d, J = 8.1 Hz, 1H, O C CH), 7.19 (t, J = 7.0 Hz,
HH
HH
1H, O C C CH CH), 7.33 (t, J = 7.5 Hz, 1H, O C CH CH), 7.46
HH
(td, J = 7.5 Hz, J = 2.9 Hz, 1H, P C CH CH), 7.64 (t, J
=
HH
PH
HH
7.7 Hz, 1H, P C C CH CH), 7.82 (dd, J = 7.5 Hz, J = 12.6 Hz,
HH
PH
1H, P C CH), 7.87 (d, JHH = 8.8 Hz, 1H, O C C CH), 7.92 (dd, J
=
=
HH
8.4 Hz, JPH = 5.0 Hz, 1H, P C C CH). 13C NMR (CDCl3): δ = 5.7 (J
PC
5.7 Hz, CH3), 21.6 (JPC = 98.6 Hz, CH2), 120.2 (JPC = 5.9 Hz, O C CH),
122.1 (JPC = 10.7 Hz, O C C), 123.7 (JPC = 9.3 Hz, P C C CH), 124.1
(J = 118.2 Hz, P-C), 124.3 (O C C CH CH), 125.0 (O C C CH),
PC
128.2 (J = 13.2 Hz, P C CH CH), 129.8 (J = 11.0 Hz, P C CH),
PC
PC
130.4 (O C CH CH), 133.0 (J = 2.3 Hz, P C C CH CH), 135.5
PC
(JPC = 5.8 Hz, P-C-C), 149.1 (JPC = 8.3 Hz, O-C). 31P NMR (CDCl3): δ =
40.6.

2140
J. Artner et al.
Compound 3
M.p. 108◦C. Analfound: C, 70.48; H, 5.80%. Analcalc(C15H15O2P): C,
69.76; H, 5.85 %. MS (70 eV): m/z = 258, 230, 216, 215, 168. IR
(KBr): 3051, 2966, 2929, 2876, 1606, 1595, 1583, 1558, 1479, 1445,
1429, 1381, 1345, 1302, 1273, 1252, 1225, 1203, 1164, 1138 cm−1
.
1H NMR (CDCl3): δ = 0.95 (t, J = 7.3 Hz, 3H, CH3), 1.49–1.71 (m,
HH
2H, CH3-CH2), 1.90–2.07 (m, 2H, P-CH2), 7.17 (d, J = 7.7 Hz, 1H,
HH
O C CH), 7.18 (t, J = 7.6 Hz, 1H, O C C CH CH), 7.32 (t, J
=
HH
HH
7.6 Hz, 1H, O C CH CH), 7.45 (td, J = 7.5 Hz, J = 2.9 Hz, 1H,
HH
PH
P C CH CH), 7.63 (t, J = 7.7 Hz, 1H, P C C CH CH), 7.81 (dd,
HH
J
= 7.2 Hz, J = 12.3 Hz, 1H, P C CH), 7.85 (d, J = 8.1 Hz, 1H,
HH
PH
HH
O C C CH), 7.90 (dd, J = 8.3 Hz, J = 4.8 Hz, 1H, P C C CH).
HH
PH
13C NMR (CDCl3): δ = 15.1 (J = 16.3 Hz, CH3), 15.3 (J = 4.4 Hz,
PC
PC
CH3-CH2), 30.4 (J = 96.5 Hz, P-CH2), 120.2 (J = 6.0 Hz, O-C-CH),
PC
PC
122.1 (JPC = 10.9 Hz, O C C), 123.7 (JPC = 9.3 Hz, P C C CH), 124.3
(O C C CH CH), 124.6 (J = 118.0 Hz, P C), 125.0 (O C C CH),
PC
128.2 (J = 13.1 Hz, P C CH CH), 129.8 (J = 10.9 Hz, P C CH),
PC
PC
130.3 (O C CH CH), 132.9 (J = 2.3 Hz, P C C CH CH), 135.4
PC
(J = 5.9 Hz, P C C), 149.1 (J = 8.2 Hz, O C). 31P NMR (CDCl3):
PC
PC
δ = 39.1.
Synthesis of Compounds 4–8—General Procedure
10-Ethoxy-10H-9-oxa-10-phosphaphenanthrene (1 mol, 230.1 g) and
the respective alcohol [1 mol, 1-octanol (157.5 mL), 2-ethyl-1-
hexanol (156.3 mL), 1-decanol (190.9 mL), 1-octadecanol (270.5 g), 2-
allyloxyethanol (106.9 mL)] were stirred intensely at 120◦C. Pressure
was slowly decreased down to ≈10 mbar—keeping the reaction mixture
boiling gently. When boiling was not noticed any longer, temperature
and pressure were kept at 120◦C and ≈10 mbar, respectively, for an-
other 3 h. The reaction vessel was charged with argon, p-toluenesulfonic
acid methylester [precursor of 4, 6–8, 7 mmol, 1.06 mL] or 1-bromo-2-
ethylhexane (precursor of 5, 50 mmol, 8.89 mL) was added, the temper-
ature was increased to 175◦C, and kept for another 24 h (precursor of
4, 6–8) or 60 h (precursor of 5), respectively, to yield the corresponding
clear 10-alkyl-9-oxa-10-phosphaphenanthrene-10-oxide (4 oily liquid, 5
oily liquid, 6 oily liquid, 7 glassy substance, 8 oily liquid) in a purity
exceeding 95%. Recrystallization of 7 from hexane.
Compound 4
Analfound: C, 74.65; H, 7.90%. Analcalc(C20H25O2P): C, 73.15; H,
7.67%. MS (70 eV): m/z = 328, 243, 230, 216, 215, 168. IR (film): 3064,

Novel Synthesis of DOPO Derivatives
2141
2953, 2927, 2855, 1606, 1595, 1582, 1560, 1477, 1448, 1432, 1296, 1275,
1252, 1235, 1207, 1147, 1119 cm−1. 1H NMR (CDCl3): δ = 0.81 (t, J
=
HH
6.5 Hz, 3H, CH3), 1.04–1.41 (m, 10H, CH3-(CH2)5), 1.47–1.68 (m, 2H,
P-CH2-CH2), 1.91–2.14 (m, 2H, P-CH2), 7.18 (d, J = 7.7 Hz, 1H,
HH
O C CH), 7.19 (t, J = 7.4 Hz, 1H, O C C CH CH), 7.33 (t, J
=
HH
HH
7.6 Hz, 1H, O C CH CH), 7.46 (td, J = 7.4 Hz, J = 2.8 Hz, 1H,
HH
PH
P C CH CH), 7.64 (t, J = 7.7 Hz, 1H, P C C CH CH), 7.82 (dd,
HH
J
= 7.2 Hz, J = 12.4 Hz, 1H, P C CH), 7.86 (d, J = 7.9 Hz,
HH
PH
HH
1H, O C C CH), 7.91 (dd, JHH = 8.2 Hz, JPH = 4.9Hz, 1H, P-C-C-CH).
13C NMR (CDCl3): δ = 13.8 (CH3), 21.3 (JPC = 4.6 Hz, P-CH2-CH2), 22.3
(CH2), 28.2 (JPC = 96.6 Hz, P-CH2), 28.59 (CH2), 28.62 (CH2), 30.2 (J
=
PC
15.4 Hz, P-CH2-CH2-CH2), 31.4 (CH2), 120.0 (J = 5.9Hz, O-C-CH),
PC
122.0 (J = 10.7Hz, O-C-C), 123.6 (J = 9.3 Hz, P C C CH), 124.2
PC
PC
(O C C CH-CH), 124.5 (J = 118.0 Hz, P-C), 124.8 (O-C-C-CH),
PC
128.0 (J = 13.1 Hz, P C CH-CH), 129.6 (J = 10.9 Hz, P C CH),
PC
PC
130.2 (O C CH CH), 132.8 (J = 2.3 Hz, P C C CH CH), 135.2
PC
(J = 6.0 Hz, P C C), 148.9 (J = 8.3 Hz, O C). 31P NMR (CDCl3):
PC
PC
δ = 39.2.
Compound 5
Analfound: C, 74.07; H, 7.73%. Analcalc(C20H25O2P): C, 73.15; H,
7.67%. MS (70 eV): m/z = 328, 299, 271, 230, 216, 215, 168. IR (film):
3067, 3065, 2959, 2931, 2872, 1607, 1595, 1583, 1559, 1476, 1457,
1448, 1432, 1399, 1380, 1275, 1255, 1236, 1205, 1147, 1118 cm−1
.
1H NMR (CDCl3): δ = 0.66–0.90 (m, 8H), 1.02–1.26 (m, 4H), 1.26–1.50
(m, 4H), 1.74–2.00 (m, 3H, P-CH2, CH2-CH), 7.10–7.25 (m, 2H, O-C-CH,
O C C CH CH), 7.33 (t, J = 7.5 Hz, 1H, O C CH CH), 7.46 (td,
HH
J
= 7.5 Hz, J = 2.5 Hz, 1H, P C CH CH), 7.64 (t, J = 7.5 Hz,
HH
PH
HH
1H, P C C CH CH), 7.78–7.96 (m, 3H, P C CH, O C C CH, P-C-
C-CH). 13C NMR (CDCl3): δ = 10.2, 10.3 (CH-CH2-CH3), 13.9 (CH2-
CH2-CH3), 22.60, 22.65 (CH2-CH2-CH3), 26.8, 27.0 (J = 24.4 Hz,
CP
CH-CH2-CH3), 28.1, 28.2 (CH2-CH2-CH3), 32.4, 32.5 (J = 95.0 Hz,
CP
P CH2), 33.4–33.8 (m, CH-CH2-CH2, CH2-CH), 120.3 (J = 5.7 Hz,
O C CH), 122.3 (J = 10.7 Hz, O C C), 123.6 (J PC= 9.5 Hz,
PC
PC
P C C CH), 124.3 (O C C CH CH), 125.0 (O C C CH), 125.5,
125.6 (J = 116.7 Hz, P C), 128.2 (J = 12.8 Hz, P C CH CH),
PC
PC
123.0 (J = 10.3 Hz, P C CH), 130.4 (O C CH CH), 132.9 (J
=
=
PC
PC
2.3 Hz, P C C CH CH), 135.4 (J = 6.3 Hz, P C C), 149.3 (J
PC
PC
8.2 Hz, O C). 31P NMR (CDCl3): δ = 39.4, 39.6.
Compound 6
Analfound: C, 74.50; H, 8.34%. Analcalc(C22H29O2P): C, 74.13; H,
8.20%. MS (70 eV): m/z = 356, 243, 230, 216, 215, 168. IR (film):

2142
J. Artner et al.
3065, 2925, 2854, 1607, 1595, 1583, 1560, 1477, 1448, 1432, 1255,
1235, 1208, 1148, 1119 cm−1
6.6Hz, 3H, CH3), 1.07–1.43 (m, 14H, CH3-(CH2)7), 1.49–1.72 (m, 2H,
P-CH2-CH2), 1.92–2.12 (m, 2H, P-CH2), 7.13-7.24 (m, 2H, O C CH,
.
1H NMR (CDCl3): δ = 0.87 (t, J
=
HH
O C C CH CH), 7.32 (t, J = 7.6 Hz, 1H, O C CH CH), 7.46 (td,
HH
J
= 7.4 Hz, J =2.6 Hz, 1H, P C CH CH), 7.62 (t, J = 7.7 Hz,
HH
PH
HH
1H, P C C CH CH), 7.81-7.94 (m, 3H, P C CH, O C C CH,
P C C CH). 13C NMR (CDCl3): δ = 13.5 (CH3), 21.0 (J = 4.6 Hz,
PC
P CH2-CH2), 22.0 (CH2), 27.9 (J = 97.1 Hz, P-CH2), 28.4 (CH2),
PC
28.6 (CH2), 28.7 (CH2), 28.9 (CH2), 29.9 (J = 15.4 Hz, P-CH2-CH2-
PC
CH2), 31.2 (CH2), 119.7 (JPC = 5.9 Hz, O C CH), 121.7 (JPC = 10.8 Hz,
O C C), 123.3 (J = 9.3 Hz, P C C CH), 123.9 (O C C CH CH),
PC
124.2 (JPC = 118.1 Hz, P-C), 124.6 (O C C CH), 127.7 (JPC = 13.1 Hz,
P C CH CH), 129.3 (JPC = 10.9 Hz, P C CH), 129.9 (O C CH CH),
132.5 (J = 2.2 Hz, P C C CH CH), 134.9 (J = 5.9 Hz, P C C),
PC
PC
148.6 (J = 8.2 Hz, O C). 31P NMR (CDCl3): δ = 39.2.
PC
Compound 7
M.p. 59—61◦C. Analfound: C, 77.17; H, 9.96%. Analcalc(C30H45O2P):
C, 76.88; H, 9.68%. MS (70 eV): m/z = 468, 243, 230, 216, 215, 168.
IR (KBr): 2953, 2918, 2850, 1606, 1594, 1581, 1560, 1477, 1467, 1445,
1432, 1401, 1378, 1275, 1259, 1249, 1231, 1203, 1146, 1120 cm−1
.
1H NMR (CDCl3): δ = 0.85 (t, J = 6.5 Hz, 3H, CH3), 1.07–1.42 (m,
HH
30H, CH3-(CH2)15), 1.47–1.69 (m, 2H, P-CH2-CH2), 1.93–2.12 (m, 2H,
P-CH2), 7.19 (d, J = 7.8 Hz, 1H, O-C-CH), 7.21 (t, J = 7.4 Hz, 1H,
HH
HH
O C C CH CH), 7.34 (t, J = 7.5 Hz, 1H, O C CH CH), 7.47 (td,
HH
J
= 7.4 Hz, J = 2.8 Hz, 1H, P C CH CH), 7.65 (t, J = 7.7 Hz,
HH
PH
HH
1H, P C C CH CH), 7.84 (dd, J = 6.8 Hz, J = 11.0 Hz, 1H,
HH
PH
P C CH), 7.88 (d, J = 7.0 Hz, 1H, O C C CH), 7.92 (dd, J
=
8.4 Hz, J = 4.9 Hz, 1H, P C C CH). 13C NMR (CDCl3): δ =H1H4.0
HH
PH
(CH3), 21.5 (JPC = 4.7 Hz, P CH2 CH2), 22.6 (CH2), 28.4 (JPC = 96.8 Hz,
P-CH2), 28.9 (CH2), 29.2 (CH2), 29.3 (CH2), 29.4 (CH2), 29.5 (CH2), 29.5-
29.7 (m, CH2), 30.4 (J = 15.6 Hz, P CH2 CH2 CH2), 31.8 (CH2),
PC
120.3 (J = 6.0 Hz, O C CH), 122.2 (J = 10.8 Hz, O C C), 123.7
PC
PC
(J = 9.2 Hz, P C C CH), 124.4 (O C C CH CH), 124.7 (J
=
PC
PC
118.0 Hz, P-C), 125.0 (O-C-C-CH), 128.2 (JPC = 13.1 Hz, P C CH CH),
129.8 (J = 10.9 Hz, P C CH), 130.4 (O C CH CH), 133.0 (J
=
=
PC
PC
2.3 Hz, P C C CH CH), 135.5 (J = 5.9 Hz, P C C), 149.2 (J
PC
PC
8.2 Hz, O C). 31P NMR (CDCl3): δ = 39.2.
Compound 8
Analfound: C, 67.39; H, 5.60%. Analcalc(C17H17O3P): C, 68.00; H,
5.71%. MS (70 eV): m/z = 300, 216, 215, 168. IR (film): 3066, 2867,

Novel Synthesis of DOPO Derivatives
2143
1606, 1595, 1583, 1559, 1477, 1448, 1432, 1254, 1236, 1208, 1147,
1119 cm−1. 1H NMR (CDCl3): δ = 2.39 (td, JHH = 7.0 Hz, JPH = 14.3 Hz,
2H, P CH2), 3.59–3.77 (m, 2H, P CH2 CH2), 3.80 (d, J = 5.6 Hz,
HH
2H, CH CH=CH2), 5.01–5.18 (m, 2H, CH CH2), 5.61–5.81 (m, 1H,
CH CH2), 7.17 (d, J =7.8 Hz, 1H, O C CH), 7.18 (t, J = 7.7 Hz,
HH
HH
1H, O C C CH CH), 7.31 (t, J
= 7.6 Hz, 1H, O C CH CH),
HH
7.45 (td, J
= 7.5 Hz, J = 3.0 Hz, 1H, P C CH CH), 7.63 (t,
HH
PH
J
= 7.7 Hz, 1H, P C C CH CH), 7.82-7.95 (m, 3H, P C CH,
HH
O C C CH, P C C CH). 13C NMR (CDCl3): δ = 29.8 (JPC = 96.4 Hz,
P-CH2), 63.0 (J = 1.9 Hz, P-CH2-CH2), 71.6 (CH2-CH=CH2), 117.0
PC
(CH=CH2), 120.1 (J = 6.1 Hz, O C CH), 121.9 (J = 11.0 Hz,
PC
PC
O C C), 123.5 (J = 9.7 Hz, P C C CH), 124.4 (O C C CH-CH),
PC
124.4 (JPC = 121.6 Hz, P-C), 124.9 (O C C CH), 128.2 (JPC = 13.6 Hz,
P C CH CH), 130.1 (JPC = 11.3 Hz, P C CH), 130.3 (O C CH CH),
133.0 (J = 2.4 Hz, P-C-C-CH-CH), 133.8 (CH=CH2), 135.2 (J
=
PC
PC
6.3 Hz, P C C), 148.8 (JPC = 8.3 Hz, O-C). 31P NMR (CDCl3): δ = 36.6.
10-Allyl-9-oxa-10-phosphaphenanthrene-10-oxide (9)
10-Methoxy-10H-9-oxa-10-phosphaphenanthrene (0.175 mol, 40.3 g)
and allyl alcohol (0.175 mol, 12.0 mL) were stirred for 6 h under ar-
gon at 120◦C in a 100 mL flask equipped with a Vigreux column
(200 mm height, 14 mm diameter) and a Liebig chiller. Every hour,
the removed distillate was replaced by the same volume of allyl alco-
hol. Subsequently, ≈10 mbar were applied for 5 min to remove volatile
compounds and the apparatus was filled with argon again. Another
1.2 mL of allyl alcohol were added, the reaction mixture stirred for
another 3 h, ≈10 mbar were applied for 5 min to remove volatile com-
pounds, and the apparatus filled with argon again; this procedure was
repeated once. p-Toluenesulfonic acid methylester [1 mmol, 0.15 mL]
was added and the reaction mixture stirred for 16 h at 160◦C. Re-
crystallisation from toluene/cyclohexane = 1:1 gave white crystals of
9 with a purity exceeding 95%. Yield: 33.2 g (74%). Mp: 106◦C (lit: 102 -
3◦C8). Analfound: C, 70.59; H, 5.20 %. Analcalc(C15H13O2P): C, 70.31; H,
5.11 %. MS (70 eV): m/z = 256, 216, 215, 168. IR (KBr): 3083, 3054,
3008, 2959, 2887, 1635, 1608, 1595, 1582, 1559, 1479, 1443, 1421, 1394,
1303, 1296, 1273, 1249, 1219, 1199, 1162, 1137 cm−1. 1H NMR (CDCl3):
δ = 2.88 (dd, J = 7.5 Hz, J = 17.8 Hz, 2H, P-CH2), 4.97–5.16 (m,
HH
PH
2H, CH=CH2), 5.59–5.81 (m, 1H, CH=CH2), 7.18 (d, J = 8.4 Hz,
HH
1H, O C CH), 7.20 (t, J = 8.2 Hz, 1H, O C C CH CH), 7.33 (t,
HH
J
HH = 7.6 Hz, 1H, O C CH CH), 7.46 (td, JHH = 7.5 Hz, JPH = 3.0 Hz,
1H, P C CH CH), 7.65 (t, J = 7.8 Hz, 1H, P C C CH CH), 7.84
HH
(dd, J
= 7.6 Hz, J = 12.7 Hz, 1H, P C CH), 7.87 (d, J
=
HH
PH
HH

2144
J. Artner et al.
7.3 Hz, 1H, O C C CH), 7.91 (dd, J = 8.1 Hz, J = 4.9 Hz, 1H,
HH
PH
P C C CH). 13C NMR (CDCl3): δ = 34.6 (J = 94.3 Hz, P-CH2),
PC
120.2 (J = 6.2 Hz, O C CH), 121.0 (J = 13.2 Hz, CH=CH2), 122.0
PC
PC
(JPC = 10.9 Hz, O-C-C), 123.6 (JPC = 9.7 Hz, P C C CH), 123.9 (J
=
PC
120.1 Hz, P-C), 124.4 (O C C CH CH), 125.0 (O C C CH), 125.9
(J = 10.2 Hz, CH=CH2), 128.2 (J = 13.2 Hz, P C CH CH), 130.2
PC
PC
(J = 10.5 Hz, P C CH), 130.4 (O C CH CH), 133.2 (J = 2.4 Hz,
PC
P C C CH CH), 135.6 (J = 6.1 Hz, P-C-C), 149.2 (JPC = 8.6 Hz,
PC
PC
O-C). 31P NMR (CDCl3): δ = 34.4.
Synthesis of Compounds 10—13—General Procedure
10-Ethoxy-10H-9-oxa-10-phosphaphenanthrene (0.36 mol, 82.8 g) and
the respective alcohol [2,2-dimethyl-1,3-propanediol (0.15 mol, 15.6 g),
trimethylolpropane (0.10 mol, 13.4 g), 1,4-butandiol (0.15 mol, 13.3 mL),
terephthalic acid diglycolester (0.15 mol, 38.1 g)] were stirred intensely
at 120◦C. Over a period of 6 h, pressure was slowly decreased down
to ≈10 mbar, keeping the reaction mixture boiling gently, and subse-
quently kept there for another 12 h. Excess of 10-ethoxy-10H-9-oxa-
10-phosphaphenanthrene was distilled off (10−3 bar, T < 150◦C). At
this point, clear glassy compounds 10 and 11 were obtained in a purity
exceeding 95%.
Afterwards, the reaction vessel was charged with argon, p-
toluenesulfonic acid methylester (2 mmol, 0.3 mL) was added, tem-
perature was increased to 175◦C, and kept for another 24 h to yield
clear glassy 12 and 13 in a purity exceeding 95%. Hot 12 was poured
into 200 mL intensely stirred, boiling toluene. The resulting suspen-
sion was cooled to RT and the formed precipitate filtered off and dried
in vacuo.
Compound 10
Analfound: C, 70.12; H, 5.09 %. Analcalc(C29H26O4P2): C, 69.60; H,
5.24%. MS (70 eV): m/z = 500, 415, 301, 233, 217, 216, 215, 200,
199, 168, 152. IR (KBr): 3061, 2960, 2872, 1604, 1593, 1583, 1476,
1445, 1429, 1398, 1364, 1277, 1236, 1202, 1116 cm−1 1H NMR
.
(CDCl3): δ = 0.43–0.57 (m, 6H, CH3), 3.20–3.46 (m, 4H, CH2), 7.12–
7.23 (m, 4H, O C C CH CH, O C CH), 7.32 (t, J = 7.6 Hz, 2H,
HH
O C CH CH), 7.44 (t, J = 7.8 Hz, 2H, P C CH CH), 7.54–7.71
HH
(m, 4H, P C C CH CH, P-C-CH), 7.88–8.04 (m, 4H, O C C CH, P-
C-C-CH). 13C NMR (CDCl3): δ = 20.68–20.97 (CH3), 36.57-36.90 (CH3-
C), 73.12–73.54 (CH2), 120.4 (O-C-CH), 122.5 (J = 6.0 Hz, O-C-C),
PC
123.0 (O C C CH-CH), 123.2 (P-C-C-CH), 124.6 (O C C CH), 127.3
(J = 13.4 Hz, P C CH CH), 129.4 (O C CH CH), 131.20, 131.24
PC

Novel Synthesis of DOPO Derivatives
2145
(J = 47.3 Hz, P C CH), 131.4 (P C C CH CH), 131.82–131.93
PC
(P C ∧ P C C), 132.3 (J = 17.0 Hz, P C ∧ P C C), 149.6 (J
=
PC
PC
9.2 Hz, O-C). 31P NMR (CDCl3): δ = 128.7.
Compound 11
Analfound: C, 70.13; H, 4.80%. Analcalc(C42H35O6P3): C, 69.22; H,
4.84%. MS (70 eV): m/z = 728, 529, 513, 415, 414, 413, 313, 297, 217,
216, 215, 200, 199, 168, 152. IR (KBr): 3060, 2935, 2878, 1603, 1592,
1582, 1475, 1444, 1429, 1277, 1236, 1201, 1116 cm−1. 1H NMR (CDCl3):
δ = 0.28 (t, J = 7.5 Hz, 3H, CH3), 0.75 (q, J = 7.5 Hz, 2H, CH2-
HH
HH
CH3), 3.15–3.39 (m, 6H, O-CH2), 7.10–7.24 (m, 6H, O C C CH CH,
O-C-CH), 7.33 (t, J = 7.3 Hz, 3H, O C CH CH), 7.43 (t, J
=
HH
HH
7.1 Hz, 3H, P C CH CH), 7.50–7.66 (m, 6H, P C C CH CH, P-C-
CH), 7.86–8.03 (m, 6H, O C C CH, P-C-C-CH). 13C NMR (CDCl3):
δ = 6.6 (CH3), 20.9 (CH2-CH3), 43.43–43.94 (CH2-C), 66.78–67.69 (O-
CH2), 120.3 (O-C-CH), 122.4 (JPC = 5.8 Hz, O-C-C), 123.0 (O C C CH-
CH), 123.1 (P-C-C-CH), 124.5 (O C C CH), 127.2 (J = 13.0 Hz,
PC
P C CH CH), 129.4 (O-C-CH-CH), 131.2 (J = 48.6 Hz, P C CH),
PC
131.4 (P C C CH CH), 131.8 (P-C ∧ P C C), 132.2 (J = 16.9 Hz,
PC
P C ∧ P C C), 149.5 (JPC = 8.9 Hz, O C). 31P NMR (CDCl3): δ = 129.1.
Compound 12
Analfound: C, 69.31; H, 4.92%. Analcalc(C28H24O4P2): C, 69.14; H,
4.97%. MS (70 eV): m/z = 486, 271, 243, 216, 215, 168. IR (KBr): 3059,
2929, 1607, 1592, 1582, 1560, 1474, 1449, 1430, 1402, 1321, 1299, 1277,
1246, 1233, 1205, 1182, 1148 cm−1. 1H NMR (CDCl3): δ = 1.53–1.77 (m,
4H, P-CH2-CH2), 1.86–2.07 (m, 4H, P-CH2), 7.11 (d, J = 8.0Hz, 2H,
HH
O C CH), 7.19 (t, J = 7.4 Hz, 2H, O C C CH CH), 7.31 (t, J
=
HH
HH
7.6 Hz, 2H, O C CH CH), 7.44 (td, J = 7.4 Hz, J = 2.9 Hz, 2H,
HH
PH
P C CH CH), 7.63 (t, J = 7.7 Hz, 2H, P C C CH CH), 7.77 (dd,
HH
J
= 7.6 Hz, J = 12.7 Hz, 2H, P C CH), 7.85 (d, J = 8.7 Hz, 2H,
HH
PH
HH
O C C CH), 7.89 (dd, J = 8.1 Hz, J = 4.8 Hz, 2H, P C C CH).
13C NMR (CDCl3): δ = 22.5 (dd, J P=H 16.7, 4.5 Hz, P-CH2-CH2),
HH
PC
27.0 (J = 97.0 Hz, P CH2), 120.2 (J = 6.1 Hz, O C CH), 122.0
PC
PC
(J = 11.0 Hz, O C C), 123.8 (J = 9.6 Hz, P-C-C-CH), 124.1 (J
=
PC
PC
PC
119.4 Hz, P-C), 124.5 (O C C CH CH), 125.0 (O C C CH), 128.3
(J = 13.2 Hz, P C CH CH), 129.8 (J = 11.0 Hz, P C CH), 130.5
PC
PC
(O C CH CH), 133.2 (J = 2.4 Hz, P C C CH CH), 135.4 (J
=
PC
PC
6.2 Hz, P C C), 148.9 (JPC = 8.4 Hz, O-C). 31P NMR (CDCl3): δ = 38.3.
Compound 13
Analfound: C, 66.86; H, 4.43 %. Analcalc(C36H28O8P2): C, 66.45; H,
4.34%. ESI (10eV): m/z = 668 (M + NH+4 ), 489, 459, 430, 326,

2146
J. Artner et al.
245, 198, 186. IR (KBr): 3064, 3006, 2960, 2908, 1717, 1607, 1597,
1583, 1560, 1478, 1459, 1448, 1432, 1413, 1384, 1282, 1270, 1248,
1230, 1213, 1174, 1146 cm−1
.
1H NMR (CDCl3): δ = 2.47-2.75 (m,
4H, P-CH2), 4.48–4.70 (m, 4H, O-CH2), 7.12 (d, J = 8.0 Hz, 2H,
HH
O C CH), 7.19 (t, J = 7.5 Hz, 2H, O C C CH CH), 7.30 (t, J
=
HH
HH
7.6 Hz, 2H, O C CH CH), 7.42 (td, J = 7.4 Hz, J = 3.0 Hz,
HH
PH
2H, P C CH CH), 7.62 (t, J
= 7.8 Hz, 2H, P C C CH CH),
HH
7.75-7.93 (m, 10H, P C CH, O C C CH, P C C CH, O=C-C-CH).
13C NMR (CDCl3): δ = 28.7 (J = 97.1 Hz, P-CH2), 58.8 (J
=
=
=
PC
PC
2.5 Hz, P CH2-CH2), 120.1 (J = 6.2 Hz, O C CH), 121.7 (J
PC
PC
11.2 Hz, O C C), 123.8 (J = 9.6 Hz, P C C CH), 123.9 (J
PC
PC
122.4 Hz, P-C), 124.7 (O C C CH CH), 125.0 (O C C CH), 128.5
(J = 13.5 Hz, P C CH CH), 129.3 (O C C CH), 129.9 (J
=
=
=
PC
PC
11.2 Hz, P C CH), 130.6 (O C CH CH), 133.2 (O C C), 133.4 (J
PC
2.3 Hz, P C C CH CH), 135.4 (J = 6.3 Hz, P C C), 148.7 (J
PC
PC
8.3 Hz, O C), 164.9 (O C). 31P NMR (CDCl3): δ = 34.0.
Synthesis of Compounds 14 and 15—General Procedure
10-Ethoxy-10H-9-oxa-10-phosphaphenanthrene (0.36 mol; 82.8 g)
and the respective alcohol [1,3,5-tris-(2-hydroxyethyl) cyanuric acid
(0.1 mol, 26.1 g); 16 made of 0.15 mol of 1,3,5-tris-(2-hydroxyethyl) cya-
nuric acid (dissolved in ≈25 mL of dioxane remaining from preparation
of 16)] were unified under vigorous stirring. In the case of 16, dioxane
was primarily removed by vacuum distillation while simultaneously
heating the reaction mixture up to 135◦C.
Starting from 135◦C, the temperature was constantly increased
up to 160◦C over 9 h applying a vacuum of 10 mbar. After another
6 h of stirring at 160◦C and 10 mbar, excess 10-ethoxy-10H-9-oxa-
10-phosphaphenanthrene was distilled off (10−3 bar, T < 160◦C). Fol-
lowing this procedure, the reaction vessel was charged with argon, p-
toluenesulfonic acid methylester (2 mmol, 0.3 mL) was added, the tem-
perature was increased to 175◦C, and the mixture was kept for another
24 h at the same temperature to yield clear glassy 14 and 15 in a purity
exceeding 95%.
Compound 14
Analfound: C, 63.81; H, 4.30; N, 4.54%. Analcalc(C45H36N3O9P3): C,
63.16; H, 4.24; N, 4.91%. ESI (10 eV): m/z = 873 (M + NH+4 ), 856
(M + H+), 511, 489, 430, 245, 186. IR (KBr): 3060, 2962, 2931, 2873,
1689, 1609, 1595, 1583, 1561, 1475, 1431, 1402, 1376, 1338, 1260,
1245, 1204, 1146, 1120 cm−1
6H, P-CH2), 3.88–4.15 (m, 6H, N-CH2), 7.10–7.25 (m, 6H, O C CH,
.
1H NMR (CDCl3): δ = 2.26–2.61 (m,

Novel Synthesis of DOPO Derivatives
2147
O C C CH CH), 7.32 (t, J
(td, J
= 7.6 Hz, 3H, O C CH CH), 7.46
= 7.4 Hz, J
=H2H.9 Hz, 3H, P C CH CH), 7.64 (t,
HH
PH
J
= 7.7 Hz, 3H, P C C CH CH), 7.73–7.96 (m, 9H, P C CH,
HH
O C C CH, P C C CH). 13C NMR (CDCl3): δ = 26.1 (JPC = 96.4 Hz,
P CH2), 36.5 (N CH2), 120.3 (J = 5.9 Hz, O C CH), 121.7 (J
=
PC
PC
11.1 Hz, O C C), 123.6 (J = 122.3 Hz, P C), 123.8 (J = 9.6 Hz,
PC
PC
P C C CH), 124.7 (O C C CH CH), 125.0 (O C C CH), 128.3
(J = 13.6 Hz, P C CH CH), 129.8 (J = 11.7 Hz, P C CH), 130.5
PC
PC
(O C CH CH), 133.3 (J = 2.2 Hz, P C C CH CH), 135.3 (J
=
PC
PC
6.0 Hz, P C C), 147.7 (C O), 148.6 (J = 8.3 Hz, O C). 31P NMR
PC
(CDCl3): δ = 33.54, 33.59, 33.63.
Compound 15
MALDI: m/z = 4287 (nonamer), 3946 (octamer), 3504, 3063, 2622,
2181, 1738, 1297 (dimer), 856 (monomer). IR (KBr): 3066, 2968, 2913,
2876, 1692, 1607, 1595, 1582, 1562, 1463, 1431, 1367, 1325, 1260,
1233, 1201, 1147, 1118 cm−1
.
1H NMR (CDCl3): δ = 2.25–2.70 (m,
P CH2), 3.38–3.66 (m, O CH2), 3.74–4.14 (m, N CH2), 7.08–7.21 (m,
O C CH, O C C CH CH), 7.23–7.34 (m, O C CH CH), 7.35–7.48
(m, P C CH CH), 7.52–7.66 (m, P C C CH CH), 7.71–7.91 (m,
P C CH, O C C CH, P C C CH). 13C NMR (CDCl3): δ = 25.6 (bd,
J
= 96.3 Hz, P-CH2), 35.9 (bs, P CH2-CH2), 41.1 (bs, O CH2 CH2),
PC
66.2 (bs, O CH2), 119.4–119.9 (m, O C CH), 121.1 (bd, JPC = 11.1 Hz,
O C C), 123.0 (bd, J = 121.1 Hz, P C), 123.3 (bd, J = 8.9 Hz,
PC
PC
P C C CH), 124.1 (bs, O C C CH CH), 124.5 (bs, O C C CH),
127.5–128.1 (m, P C CH CH), 129.1 (bd, J = 11.1 Hz, P C CH),
PC
129.9 (bs, O C CH CH), 132.8 (bs, P C C CH CH), 134.5 (bd, J
=
PC
5.8 Hz, P C C), 146.9–148.3 (m, C O, O C). 31P NMR (CDCl3): δ =
33.8–34.2 (m).
Oligomeric 1,3,5-Tris-(2-hydroxyethyl) Cyanuric Acid (16)
1,3,5-Tris-(2-hydroxyethyl) cyanuric acid (0.15 mol, 39.2 g) and 4.5 g
Amberlite IR-120 (plus) were stirred at 170◦C under a gentle stream
of argon. Every hour, a pressure of ≈10 mbar was applied for 5 min to
1
remove formed water. The reaction was traced by H NMR and when
the CH/OH-ratio reached 7.0 (≈10–15 h; ratiot=0 = 4), vacuum was
applied a last time for 5 min. The oligomer was cooled to 80◦C and
dissolved in 150 mL of boiling dioxane. The solution was cooled to RT
and filtered through kieselguhr. 40 mL of toluene were added and the
solvents were removed by vacuum distillation to remove the remaining
water azeotropically. The residue was dissolved in another 80 mL of
dioxane and a few drops of triethanolamine and 2 g of triethyl orthofor-

2148
J. Artner et al.
mate were added to neutralise the remaining traces of acid and water.
The solution was reduced to half of its volume by vacuum distillation
and used without further treatment. ESI (50 eV): m/z = 1494 (hexamer
+ NH+4 ), 1251 (pentamer + NH+4 ), 1008 (tetramer + NH+4 ), 765 (trimer
+ NH+4 ), 748 (trimer + H+), 522 (dimer + NH+4 ), 505 (dimer + H+), 262
(monomer + H+), 244 (monomer-OH−). 1H NMR (d6-DMSO): δ = 3.40-
3.62 (m, 3.5H, O CH2), 3.65-3.96 (m, 3.5H, N CH2), 4.73 (s, 1H, OH).
13C NMR (d6-DMSO): δ = 41.5 (CH2-CH2-O-CH2), 44.6 (CH2-CH2-OH),
57.8 (CH2-OH), 66.7 (CH2 O CH2), 149.1 (C O), 149.2 (C O), 149.3
(C O), 149.4 (C O).
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