Diastereoselective formation of 18-membered ring BINOL-hydrogen phosphonate dimers - Quasicovalent hydrogen bonds?

Article abstract of DOI:10.1139/V07-060

Diastereoselective syntheses of the unusual dimers, 4-heptyl-2-(2′- hydroxy-binaphthyl)hydrogen phosphonate (5) and the cyclohexyl analogue (7), are achieved by hydrolysis of 4-(3,5-dioxa-4-phosphacyclohepta[2,1-α;3,4- α′]dinaphthalene-4-yloxy)heptane (4)

Full text of DOI:10.1139/V07-060

466
Diastereoselective formation of 18-membered ring
BINOL-hydrogen phosphonate dimers — Quasi-
covalent hydrogen bonds?
Hossein A. Dabbagh, Nader Noroozi-Pesyan, Ali R. Najafi-Chermahini,
Brian O. Patrick, and Brian R. James
Abstract: Diastereoselective syntheses of the unusual dimers, 4-heptyl-2-(2′-hydroxy-binaphthyl)hydrogen phosphonate
(5) and the cyclohexyl analogue (7), are achieved by hydrolysis of 4-(3,5-dioxa-4-phosphacyclohepta[2,1-α;3,4-α′]-
dinaphthalene-4-yloxy)heptane (4) and the cyclohexane analogue (6), respectively. Two out of eight possible pairs of
monomers units are involved in the stereoselective formation of the dimer 5a of configuration BINOLR-PS:BINOLR-PS;
this is determined by X-ray crystallographic data, which reveal a centrosymmetric, 18-membered ring structure with Ci
symmetry, consisting of two monomers strongly hydrogen-bonded between the oxygen of P=O units and hydroxyl hy-
drogen atoms. Mass spectrometric, melting point, and thermal decomposition point data, as well as NMR data, support
the presence of strong, quasi-covalent hydrogen bonds. Computational analysis suggests that the diastereoselectivity is
controlled by molecularly constrained geometry of the monomer. Compound 7, although not characterized crystallo-
graphically, appears to be analogous to 5.
Key words: 18-membered ring, phosphonate dimer, diastereoselectivity, hydrogen-bonds, computational analysis.
Résumé : On a réalisé les synthèses diastéréosélectives des dimères inhabituels du phosphonate acide de 4-heptyl-2-
(2N-hydroxybinaphtyle) (5) et de son analogue cyclohexyle (7) par le biais de l’hydrolyse respectivement du 4-(3,5-
dioxa-4-phosphacycloheptane[2.1-α;3,4-α′]dinaphtalène-4-yloxy)heptane (4) et de son analogue cyclohexane (6). Deux
des huit paires possibles d’unités monomères sont impliquées dans la formation stéréosélective du dimère 5a de confi-
guration BINOLR-PS:BINOLS-PR; cette conclusion est basée sur des données de diffraction des rayons X qui mettent en
évidence l’existence d’une structure cyclique centrosymétrique à 18 chaînons de symétrie Ci, formée de deux monomè-
res reliés fortement par une liaison hydrogène entre l’oxygène des unités P=O et les atomes d’hydrogène des hydroxy-
les. Les données de spectrométrie de masse, de point de fusion et de point de décomposition thermique ainsi que les
données de la RMN sont en accord avec la présence de liaisons hydrogènes fortes et de nature pratiquement covalen-
tes. Une analyse par des calculs théoriques suggère que la diastéréosélectivité est contrôlée par la géométrie fixée
d’une façon moléculaire du monomère. Même si le composé 7 n’a pasété caractérisé d’une façon cristallographique, il
semble être analogue au composé 5.
Mots-clés : cycle à 18 chaînons, dimère de phosphonate, diastéréosélectivité, liaisons hydrogènes, analyse par des
calculs théoriques.
[Traduit par la Rédaction] Dabbagh et al. 474
Introduction
few selected recent articles exemplify the general scope of
the topic, ranging from the role of H bonding in: weak inter-
actions in the gas phase (1), supramolecular assemblies (2),
helical structures (3), promoting catalytic enantioselective
reactions (4), molecular rotors (5), through to measurement
of H-bond acidity of organics (6). Important consequences
of both inter- and intra-molecular H bonding have long been
recognized in the physiochemical behavior of DNA and
RNA (7), while H bonding within phosphorus systems, of
During studies aimed at developing new chiral phosphine
ligands based on the binaphthol backbone, we accidentally
discovered a dimeric structure maintained by two exception-
ally strong hydrogen bonds, and this work is described here.
Hydrogen bonding plays a key role in biology and chem-
istry and remains a topic of intense current interest, as
judged by an enormous continuing amount of literature. A
Received 24 April 2007. Accepted 25 May 2007. Published on the NRC Research Press Web site at canjchem.nrc.ca on 27 June
2007.
H.A. Dabbagh. Department of Chemistry, Isfahan University of Technology, P.O. Box: 84155, Isfahan, Iran.
N. Noroozi-Pesyan. Department of Chemistry, Faculty of Science, Urmia University, 57159, Urmia, Iran.
A.R. Najafi-Chermahini. Department of Chemistry, Yasuj University, Yasuj, Iran.
B.O. Patrick and B.R. James.1 Department of Chemistry, The University of British Columbia, Vancouver, BC V6T 1Z1, Canada.
1Corresponding author (e-mail: dabbagh@cc.iut.ac.ir; brj@chem.ubc.ca).
Can. J. Chem. 85: 466–474 (2007)
doi:10.1139/V07-060
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Dabbagh et al.
467
Table 1. Classification of hydrogen bonds within P-containing
Scheme 1. Formation of the dimeric phosphonates.
systems.
Bond distance
Linkages
[range, donor---H---acceptor] (Å) Strength
P-O-H---O-P
P-OH---O-P
P-O-H---O-C
P-H---OH2
P-O---H-N
C-O-H---O=Pa 2.70
2.39–2.50
2.50–2.70
2.41–2.82
2.56–3.15
2.65–3.10
Very strong
Strong
Strong
Moderate
Moderate
Strong
Note: Data taken from from refs. 8a, 10b, 10f, and 11a.
aDetermined by an X-ray crystallographic study of 5a (see Scheme 2
and Fig. 1).
relevance to our paper, is also well documented (8). Some
contributions from our collaborative group have also demon-
strated the importance of hydrogen bonding in determining
the structure, conformation, energy, and reactivity properties
of a molecule (9).
The factors determining the strength of a hydrogen bond,
other than electronegativities of the donor and acceptor
atoms, remain of interest. Homonuclear linear O---H---O
bonds are well understood and display a practically continu-
ous range of O---H---O distances from 2.36 to 3.69 Å: the
upper value is the sum of the van der Waals radii and not a
physical limit of the hydrogen-bond interaction that has been
qualitatively defined as very strong (<2.50 Å), strong (2.41–
2.82 Å), medium (2.56–3.15 Å), or weak (>3.15 Å); see
Table 1 (8a, 10, 11). The strongest hydrogen bonds are seen
in homonuclear linear or nearly linear systems with an
O–H–O angle > 165°; the energies of bent O–H–O systems
have been evaluated computationally and are 90%, 60%, and
10% of the linear system value for angles of 165°, 149°, and
110°, respectively (10b, 11a). A unified hydrogen bond theory
has been presented in which O---H---O bonds are divided
into five classes: negative charge-assisted [–O---H---O–]–
(a strong H bond); positive charge-assisted [=O---H---O=]+
(strong); resonance-assisted [-O–H---O=] (strong), where
the two oxygens are connected by a π-conjugated system
of variable length, including cases where the oxygens
are attached to P or As atoms; polarization-assisted
[---O(R)–H---O(R)H---] (moderate); and isolated H bonds
[-O-H---O(R)(R)] (weak) (11a). Of note, a recently reported
variable-temperature X-ray crystallographic and DFT com-
putational study of the N-H---O/N---H-O tautomeric compe-
tition in 1-(arylazo)-2-naphthol has led to a transition-state
hydrogen bond theory (12).
structures, 4-heptyl-2-(2′-hydroxybinaphthyl)hydrogen phos-
phonate (5a) and the cyclohexyl analogue (7a) (the “a” label
refers to a particular stereoisomer of these dimers — see
later). The 18-membered ring structure of these dimeric
compounds is maintained by the presence of two strong
hydrogen bonds, as discussed later (see Scheme 1).
Results and discussion
Prior to a discussion of compounds 5a and 7a and their
unusual structures, it is best to introduce some general com-
ments about H bonding in phosphorus compounds. The de-
gree of such bonding, which is seen in the solid, liquid, and
solution states, varies depending on the solvent, temperature,
and the nature of the substituent group on the P atom.
Most phosphorus acids form dimers with strong H bonds
within a 6- to 10-membered ring (8a), although the esters
(RO)PO(OH)2 (R = 3-methylhexyl or n-octyl) are polymers
containing intermolecular H bonding (8a). Relevant to our
paper, aryl H-phosphonates have been synthesized and char-
acterized by 31P NMR spectroscopy (13).
Dimeric centrosymmetric ring structures are quite
common within phosphorus chemistry: 1 and 2 exemplify
12- and 8-membered ring structures, respectively (8a), and
according to spectroscopic evidence, esters of (trichloro-
acetyl)amidophosphoric acid exist as 2a rather than 2b,
which suggests that the H bond in N-H---O=P is more stable
than that in N-H–O=C (8a).
Our current work, based on designing chiral phosphines,
prompted us to synthesize 4-(3,5-dioxa-4-phosphacyclo-
hepta[2,1-α;3,4-α′]-dinaphthalene-4-yloxy)heptane (4) and
the corresponding cyclohexane analogue (6) (see Scheme 1).
During the attempted purification of 4 and 6, we discovered
their hydrolysis products, which proved to be the dimeric
Although lower oxy-acids of phosphorus were initially
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Can. J. Chem. Vol. 85, 2007
1
1
thought to exist primarily in tautomeric forms in which the
central atom was trivalent, it is now well-established that the
majority of such compounds prefer structures that incorpo-
rate formally pentavalent phosphorus (8a, 14). A detailed
analysis of bond and contact distances has suggested that
when the O---O interaction is decreased from 2.80 to
2.40 Å, the H bond is transferred from a symmetrical
O---H---O electrostatic interaction to a covalent unsymmet-
rical O–H---O bond (10b, 11a).
Analysis of crude samples of 5 by solution H, H{31P},
31P, and 31P{1H} NMR spectroscopy (see Experimental sec-
tion) showed two major components 5a and 5b, two minor
components 5c and 5d, and a trace amount of an unknown
compound 5x (Figs. S1–S8).2 The 31P NMR spectrum of
pure 5a (grown as a single crystal from a cyclohexane-
CH2Cl2 solution of crude 5) is a doublet of doublets centered
at δ 3.80 because of coupling to two protons (1JPH = 707,
3JPH = 10.7 Hz), as confirmed by a H-decoupled spectrum
1
that generates a 31P{1H} singlet; the JPH value is in the ex-
1
1
pected range (16). The H NMR spectrum for 5a, showing
Synthesis of the BINOL phosphonates and solution
NMR characterization (Scheme 1)
signals for the heptyl and binaphthyl protons, is consistent
with the solid-state structure described later; the PH proton
of 5a is seen as a doublet at δ 6.65 (1JPH = 703 Hz), which
Hydrolysis of the phosphate esters 4-(3,5-dioxa-4-phos-
phacyclohepta[2,1-α;3,4-α′]-dinaphthalene-4-yloxy)heptane
(4) and the cyclohexane analogue (6) produced what initially
are the respective monomers, 4-heptyl-2-(2′-hydroxybina-
phthyl)hydrogen phosphonate (5m) and the 4-cyclohexyl an-
alogue (7m). The monomers, being chiral at phosphorus
coupled with the axial chirality of the BINOL moiety, can
exist theoretically in four possible configurations (BINOLR-
PR, BINOLR-PS, BINOLS-PS, BINOLR-PS). Of interest, both
precursor monomers appear to dimerize selectively with
their mirror images to form the 18-membered ring dimers;
certainly, the structurally characterized 5a (see later) has the
configuration BINOLR-PS:BINOLR-PS, maintained by two
strong hydrogen bonds, while a second stereoisomer seen in
solution (5b, see later) could be the BINOLR-PR:BINOLS-PS
form. The analogous system based on 7 is considered from
NMR data to behave similarly.
collapses to a singlet in the H{31P} spectrum. A 13C{1H}
1
NMR spectrum of 5a shows 27 signals corresponding to the
number of binaphthyl and heptyl carbon atoms (20 and 7, re-
spectively). Although 5a was the only compound isolated in
a pure state, it was not difficult (e.g., from the relative peak
heights of the doublet of doublet patterns seen in the
31P{1H} spectra and relative intensities of the various 1H res-
onances) to determine the NMR assignments (from data for
mixtures) associated with what are possibly other stereo-
isomers (i.e., 5b, 5c, and 5d, see later); similar reasoning al-
lowed for the determination of resonances associated with
each of 7a–7d.
The NMR spectra of 5b are similar to those of 5a, and
similar data are seen for 5c, but for this species the 31P shift
is centered at δ 8.80; 5d is characterized by just a doublet
1
centered at δ 5.45 in the 31P spectrum with a JPH value of
The necessary precursor reagent 4-chloro-3,5-dioxa-4-
phosphacyclohepta[2,1-α;3,4-α′]-dinaphthalene (3) was pre-
pared by reaction of PCl3 with 2,2′-dihydroxy-1,1′-bina-
phthyl (BINOL) in dry Et2O under an N2 atmosphere, using
procedures from the literature (15). This chloro compound
was used without purification in the next step for the pro-
duction of the phosphate esters 4 and 6 by treatment with the
appropriate alcohol, 4-heptanol, or cyclohexanol, respec-
tively. The esters were isolated in 70%–80% yields as yel-
low powders. The heptyl ester 4 was characterized in
720 Hz. The structure of 5a was elucidated by X-ray crystal-
lography, while relevant EI and ES mass spectrometric data
were also measured (see later).
The cyclohexyl-2-(2′-hydroxybinaphthyl)hydrogen phos-
phonate (7), like 5, was isolated as a pale yellow solid. 31P,
31P{1H}, H, and H{31P} NMR analysis revealed again the
presence of two major components, 7a (40%) and 7b (38%),
and two minor components, 7c (18%) and 7d (4%); Figs. S9
and S10.2 Unfortunately, we were unsuccessful in obtaining
any crystals of 7 suitable for X-ray analysis. However, the
NMR data correspond closely to those measured for the 5a–
5d mixture (after allowance for the replacing of the 4-heptyl
by a cyclohexyl moiety), and the structure of 7a is likely to
be analogous to that of 5a but with a different R group
(Scheme 1).
1
1
1
solution by H NMR (with signals assigned for the methyl,
methylene, and methyne protons of the heptyl group and the
12 binaphthyl protons) and a 31P{1H} singlet at δ 146. The
corresponding cyclohexyl analogue 6 similarly showed three
1
sets of H signals for the 10 methylene protons, the single
CH proton, and binaphthyl protons, as well as a 31P{1H} sin-
glet at δ 150.
X-ray structure of 5a
The remarkable hydrolysis products from 4 and 6 were
accidentally synthesized by leaving acetone solutions of the
esters in air at ambient temperatures for several days. After
work-up procedures and purification by recrystallization, the
respective yellow solid products 4-heptyl-2-(2′-hydroxy-
binaphthyl)hydrogen phosphonate (5) and the cyclohexyl an-
alogue (7) were isolated as dimeric forms, based on NMR
and MS data and an X-ray analysis of 5a.
The X-ray crystallographic analysis of 5a reveals the es-
sential monomer structure 5m shown in Fig. 1 (see also
Scheme 1), while the unit cell reveals two such monomer
units interacting strongly via two hydrogen bonds between
phosphonate P=O moieties and the OH groups of the
BINOL; an overall centrosymmetric dimer structure for 5a is
seen with an 18-membered ring with Ci symmetry (Fig. 1
2 Supplementary data for this article are available on the journal Web site (http://canjchem.nrc.ca) or may be purchased from the Depository
of Unpublished Data, Document Delivery, CISTI, National Research Council Canada, Ottawa, ON K1A 0R6, Canada. DUD 5180. For more
information on obtaining material refer to http://cisti-icist.nrc-cnrc.gc.ca/irm/unpub_e.shtml. CCDC 623091 contains the crystallographic
data for this manuscript. These data can be obtained, free of charge, via http://www.ccdc.cam.ac.uk/conts/retrieving.html. Figs. S1–S13 in-
1
1
1
clude: 31P{1H}, 31P, H, and H{31P} NMR spectra of 5a, 5b, 5c, and 5d; 31P{1H}, 31P, and H NMR spectra of 7a, 7b, 7c, and 7d; com-
puter-generated minimum configurations for the six pairs of 5m monomers; and computer-generated minimum configuration for a 5b dimer.
© 2007 NRC Canada

Dabbagh et al.
469
Scheme 2. Diagram showing hydrogen bonding within the dimer.
Fig. 1. Molecular structure of dimer 5a (top) and monomer 5m
(bottom).
Scheme 3. Diagram showing resonance-assisted hydrogen bond-
ing.
Scheme 4. Summary of the mass spectral data. Values in paren-
theses are the % base peak from EI. Values in boldface marked
with asterisks (*) are the % base peak from TOF MS Electron
Spray (ES+).
and Schemes 2 and 3). The torsion angles between the two
BINOL rings are ~96°, favoring the s-transoid conformation.
One of the BINOL units in the dimer structure necessarily
has R axial symmetry and the other unit has S symmetry.
As expected, the P=O bond is some 0.1 Å shorter than the
P–O bonds in the binaphthyl and heptyl groups, which are
1.58 and 1.55 Å, respectively. Within the hydrogen bonds,
the distance between the hydroxyl-H and the acceptor-O
atom is 1.81(2) Å, while the bond length for the hydroxyl
group is 0.89(2) Å, and the O–H---O bond angle is 159°; the
distance between the oxygens of the O---H-O moiety is
~2.70 Å, implying the presence of a strong hydrogen bond
within this P=O---H-O-C system (Scheme 2 and Table 1).
The strength of hydrogen bonding in the dimer may result
from contributions of resonance-assisted and (or) polariza-
tion-assisted hydrogen bonds (see Introduction and Table 1),
while the deviation from linearity of the O–H---O angle
likely allows for a decrease in strain energy of the dimer
structure (Scheme 3). More information supporting the pres-
ence of strong hydrogen bonds in 5a was gleaned from mass
spectrometric data.
Mass spectroscopic analysis
Positive ion electrospray mass spectral data for a solution
of 5a in CH3OH–CHCl3 showed molecular ions of m/z val-
+
ues around 897 corresponding to the dimer formulation M2 ,
449 corresponding to the monomer M+, and a 100% base
peak at 350 corresponding to [BINOL + PO2H]. Electron
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Can. J. Chem. Vol. 85, 2007
Scheme 5. Plausible pathways for fragmentation of dimer 5a.
Fig. 2. (a) Computer-generated minimum configuration of mono-
mers 5m using the HF/STO-3G program. Black lines (——) in-
dicate hypothetical points of interactions to form dimers 5a (left)
and 5b (right). (b) Computer-generated minimum configuration
of dimer 5a (BINOLR-PS---BINOLS-PR). Dotted lines show com-
puted H bonds.
+
impact MS data did not show M2 and instead revealed a
610/611 fragment (not detected by the ES analysis), a peak
for M+, the 350 peak, a peak at 332, and a 100% base peak
at 286 for binaphthol. Scheme 4 summarizes these MS data
and the formulations that correspond to the m/z values.
The percent abundance in the EI spectrum of the M+ 448
peak is only about a fifth that of the 610/611 fragment,
implying that cleavage of one P–OBINOL bond and one
[O–H---O] H-bond to form the 610/611 fragment takes pref-
erence over cleavage of the two H bonds to form the mono-
mer; this suggests that the hydrogen bonding is strong (as
indicated by the O---H---O structural data) and indeed even
implies strength comparable to that of a P–O bond (at least
under the EI conditions!). The reverse situation pertains to
ES conditions where the monomer is formed exclusively
(with the 350/332 fragments) from the dimer with respect to
the 610/611 fragment; presumably, methanol breaks down
most of the dimer structure by hydrogen-bond formation and
prevents the intramolecular rearrangement required to pro-
duce the 610 fragment (Scheme 4).
Plausible mechanisms for the conversion of dimer 5a to
fragment 610 m/z (depicted by structures 5a1 and 5a2) are
outlined in Scheme 5 and involve direct loss of binaphthol
from the dimer to give 5a1 (step b), rearrangement of 5a1 to
5a2, or direct nucleophilic attack by a binaphthol oxygen of
one monomer at the phosphorus of the second monomer to
give 5a2 again with loss of binaphthol (step a). The facts that
(i) the 610 fragment is not seen in the ES-MS, (ii) the polar
methanol solvent does not break up completely the hydrogen
bonds of the dimer, and (iii) judging by the sharp melting
point at 144 to 145 °C (the hydrogen bonds likely remain in-
tact at this temperature) are all consistent with the [O---H---
O=P] hydrogen bond of the dimer being as strong as the
P-OBINOL bond. The loss of BINOL would then release
strain to give 5a1, which could rearrange to 5a2. Justification
of the direct rearrangement of the dimer 5a1 to 5a2 rear-
rangement is less obvious: a direct intramolecular nucleo-
philic attack by an oxygen of a BINOL hydroxyl group is
unlikely because methanol is a better nucleophile and should
interact more readily with the dimer to breakup the H bonds.
However, the strength of H bonds between methanol and
monomer is considered to be less than that of the H bonding
in the dimer (judging by the observation of the M2 ion). As
+
evidenced by the high melting point, the boiling point
(~180 °C in air), and thermal stability up to 250 °C (clear
liquid at boiling point temperature with no color change),
the stability of the dimer that results from the strong (“quasi-
covalent”) H bonds is remarkable. Liquid dimer, when
cooled to room temperature (RT), re-melts again at 144 to
145 °C; when the dimer is placed under vacuum in a sealed
capillary tube, decomposition becomes apparent at ~260 °C,
with darkening of the color. A CDCl3 solution of the dimer
slowly decomposes in air (likely via hydrolysis) at RT to an
unknown mixture as shown by 31P NMR spectroscopy
(Fig. S11).2
Diastereoselectivity of the dimer formation
Monomer 5m has a chiral P center and axial chirality
within the BINOL unit, while the dimer correspondingly has
twice as many chiral moieties. The X-ray data of 5a show
the presence of the diastereomers BINOLS-PR:BINOLR-PS
(meso form), and the NMR data of the crystal dissolved in
CDCl3 are consistent with the same structure. The solution
NMR spectra of the crude sample show that the major com-
ponent corresponds to 5a; seen also are very similar reso-
nances for the other major component (5b) and those of two
1
minor ones (5c and 5d), which have the same H and 31P
NMR patterns as 5a and 5b, but as noted earlier the 31P
shifts are about 4 and 1 ppm downfield, respectively, from
those of 5a and 5b (Figs. S1-S5).2
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Dabbagh et al.
471
Fig. 3. Variable temperature 31P NMR spectra of crude mixture of 4-n-heptyl-2-(2′-hydroxybinaphthyl)hydrogen phosphonate 5a (*), 5b
(ٗ), 5c (᭺), and 5d (#) in CDCl3.
Computational analysis of the molecular geometry of the
monomers predicts that only two enantiomeric pairs of
these, with configurations BINOLR-PS:BINOLR-PS and
BINOLR-PR:BINOLS-PS, have the appropriate geometry to
interact and form the dimers (see Figs. 2, S12 and S13).2
The first combination (BINOLR-PS:BINOLR-PS) is that
found experimentally for 5a, while the non-isolated 5b is
most likely of the BINOLR-PR:BINOLS-PS configuration.
Other double combinations of monomers via hydrogen
bonding to form the six other diastereomers are not possible
because the monomers do not have the appropriate configu-
rations, as seen in Fig. S12.2
strongly hydrogen bonded via two P=O---H–O moieties; a
corresponding cyclohexyl analogue appears to behave simi-
larly. Racemic BINOL was used as a precursor reagent, but
only two out of the eight possible diastereomeric dimers are
formed from the racemic mixture of monomers. The
diastereoselective formation of the H-bonded dimers is con-
trolled by molecularly constrained geometry of the mono-
mer.
Experimental
The various NMR spectra were recorded at RT (~20 °C)
in CDCl3 solution (unless stated otherwise) on Varian
90 MHz or Bruker AV 300 or 400 MHz instruments; singlet
(s), doublet (d), triplet (t), multiplet (m), quintet (quin),
broad (br); J values are given in Hz. FT-IR spectra (KBr, re-
ported in cm–1) were obtained on a Shimadzu IR-470 instru-
ment. MS data (stated as m/z values) were acquired on
Kratos Concept IIHQ LSIMS or Bruker Esquire ESI instru-
ments. The computational analyses were performed using
HyperChem pro 6.0, with PM3 calculations optimized by
Polak-Ribiere algorithms. The PM3 optimized geometries
were then taken for further optimization with the HF/STO-
3G basis set. Racemic 1,1′-bi-2-naphthol (BINOL) was ei-
ther purchased or prepared by a reported method (17).
Variable temperature 31P NMR data from 210–380 K
(Fig. 3) indicate that the chemical shifts of the major compo-
nents (5a and 5b) do not vary much with temperature, while
those of the minor components (5c and 5d) do. The NMR
behavior is reversible, and the original ratio of isomers was
seen on cooling the solution to 230 K; the data are qualita-
tively consistent with reversible conversion of dimers to
monomers with increasing temperature, and so speculatively
5c and 5d might be monomeric diastereomers.
NMR and MS data on the mixture of major species 7a
and 7b and minor species 7c and 7d, in which the 4-heptyl
group of 5 has been replaced by cyclohexyl, suggest behav-
ior similar to that found for the 4-heptyl system.
X-ray crystallographic analysis of 5a
Conclusions
Measurements were made at –100 °C on a Rigaku ADSC
CCD area detector with graphite monochromated Mo Kα ra-
diation (λ = 0.710 60 Å). The final unit-cell parameters were
based on 7004 reflections with 2θ = 4.2°–55.7°. The data
were collected and processed using the d*TREK program
(18). The structure was solved by direct methods (19) and
The dimer 4-heptyl-2-(2′-hydroxybinaphthyl)hydrogen
phosphonate, accidentally synthesized by hydrolysis of 4-
(3,5-dioxa-4-phosphacyclohepta[2,1-α;3,4-α′]-
dinaphthalene-4-yloxy)heptane at RT, is a centrosymmetric
18-membered ring structure consisting of monomers,
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Can. J. Chem. Vol. 85, 2007
Table 4. Selected bond angles of 5a (esds in
Table 2. Crystal data for 5a.
parentheses).
Emprical formula
C27H29O4P
Bonda
Angle (°)
Formula weight
Crystal size (mm3)
Crystal system
Space group
a (Å)
448.50
0.20 × 0.20 × 0.20
Triclinic
P1 (#2)
O(4)–H(4)–O(3)
O(3)–P(1)–O(2)
O(3)–P(1)–O(1)
O(2)–P(1)–O(1)
O(3)–P(1)–H(1)
O(2)–P(1)–H(1)
O(1)–P(1)–H(1)
C(1)–O(1)–P(1)
C(21)–O(2)–P(1)
C(12)–O(4)–H(4)
C(10)–C(1)–C(2)
C(10)–C(1)–O(1)
C(2)–C(1)–O(1)
C(9)–C(10)–C(11)
O(4)–C(12)–C(11)
O(4)–C(12)–C(13)
O(2)–C(21)–C(22)
O(2)–C(21)–C(25)
C(22)–C(21)–C(25)
O(2)–C(21)–H(21)
C(22)–C(21)–H(21)
C(25)–C(21)–H(21)
159(2)
118.32(7)
113.50(7)
102.16(6)
112.7(7)
103.9(7)
104.7(8)
122.24(9)
122.27(10)
114.4(14)
123.47(14)
117.78(13)
118.66(13)
120.98(12)
124.08(14)
114.68(13)
107.92(12)
111.86(18)
108.84(18)
109.4
1.6440(2)
11.3196(3)
11.4692(2)
67.535(9)
86.23(1)
67.544(8)
1175.0(1)
2
b (Å)
c (Å)
α (°)
β (°)
γ (°)
Volume (Å3)
Z
Dcalcd (mg m–3)
1.268
F(000)
µ cm–1
476
1.48
10 620
4785 (R(int) = 0.032)
(I > 2σ(I)) 3759
4785, 335
Reflections collected
Unique reflections
No. of observations
Data, parameters
Goodness-of-fit (all data)
Final R indices
1.00
(I > 2σ(I)) R1 = 0.040, wR2 = 0.103
R1 = 0.055, wR2 = 0.109
109.4
109.4
R indices (all data)
aAtom numbers correspond to those shown in Fig. 1.
Table 3. Selected bond lengths of 5a
(esds in parentheses).
Bonda
Length (Å)
yellow solid. IR: 3500 (m), 3100 (m), 1620 (s), 1590 (s),
1
1500 (s), 1210 (s), 960 (s), 820 (s), 750 (s). H NMR (CCl4)
P(1)—O(3)
P(1)—O(2)
P(1)—O(1)
P(1)—H(1)
O(1)—C(1)
O(2)—C(21)
O(4)—C(12)
O(4)—H(4)
O(3)—H(4)
C(10)—C(11)
1.4578(11)
1.5544(12)
1.5865(11)
1.295(16)
1.4073(17)
1.5006(19)
1.3634(18)
0.89(2)
δ: 7.3–7.7 (m, 8H), 8.0–8.3 (m, 4H). 31P NMR (CDCl3) δ:
(s, 178.8). Compound 3 was used without further purifica-
tion for the synthesis of 4.
4-(3,5-Dioxa-4-phosphacyclohepta[2,1-␣;3,4-␣′]-
dinaphthalene-4-yloxy)heptane (4)
Under conditions used for the preceding synthesis, to
compound 3 (1.50 g, 4.3 mmol) dissolved in 20 mL dry tolu-
ene was added 4-heptanol (0.50 g, 4.3 mmol). To this solu-
tion at 0 °C, Et3N (2.5 mL, 8.6 mmol) was added dropwise,
and the mixture was stirred for 48 h, with the reaction prog-
ress being monitored by TLC. The white solid [Et3NH]+Cl–
was removed by filtration, and the filtrate evaporated to
dryness to give a light yellow solid, which was then washed
through a silica gel column using cyclohexane – ethyl ace-
tate (9:1); the fraction containing 4 was evaporated to dry-
ness and the solid residue was recrystallized from the same
solvent mixture to yield pure 4 in 80% yield. Melting point
124–126 °C. IR: 3050 (w), 2900 (m), 2850 (m), 1620, (m),
1580 (s), 1500 (s), 1375 (s), 1320 (s), 1060 (m), 950 (s), 930
1.81(2)
1.4942(19)
aAtom numbers correspond to those shown
in Fig. 1.
expanded using Fourier techniques (20). The non H atoms
were refined anisotropically, while the H atoms were in-
cluded but not refined. Some of the crystallographic data are
given in Table 2, while selected bond lengths and angles are
given in Tables 3 and 4, respectively.
4-Chloro-3,5-dioxa-4-phosphacyclohepta-[2,1-␣;3,4-␣′]-
dinaphthalene (3)
1
(s), 820 (s), 750 (s), 695 (m), 640 (m), 550 (m). H NMR δ:
In a 250 mL, two-necked flask, maintained at ~0 °C and
equipped with a magnetic stirrer, freshly redistilled PCl3
(1.5 mL, 17.2 mmol) was dissolved in 50 mL of dry Et2O
under N2. To this solution was added BINOL (3.67 g,
13 mmol) in 100 mL of dry Et2O, followed by Et3N
(4.3 mL, 14.9 mmol) dropwise, and the solution was stirred
for 20 h at ~0 °C. The reaction mixture was then filtered,
and the residue was washed with 5 mL of dry Et2O; solvent
was evaporated under vacuum from the filtrate to yield a
0.8–1.7 (m, 6H, CH3; and 8H, CH2), 4.1–4.5 (m, 1H, CH),
7.2–8.2 (m, 12H, binaphthyl). 31P{1H} δ: (s, 146.0).
4-n-Heptyl-2-(2′-hydroxybinaphthyl)-hydrogen-
phosphonate (5)
The compound was prepared by allowing compound 4 to
stand in air at ambient temperature for days, either in the
solid state or in acetone solution. A mixture of species is
formed but one, labeled 5a, was isolated as pale yellow crys-
© 2007 NRC Canada

Dabbagh et al.
473
1
tals (mp 144 to 145 °C, bp. ~180 °C), which were grown by
slow evaporation of solvent at RT from a 9:1 mixture of
cyclohexane–CH2Cl2 solution of the crude isolated product.
Characterization data of 5a were as follows. 1H NMR
6.43 (d, JHP = 720), 4.31 (m), 4.02 (m), 3.78 (m), 3.42 (m)
and 1.70–0.70 (m); Fig. S10. 31P{1H} NMR analysis showed
components at δ: 3.94 (7a, 40%), 4.23 (7b, 38%), 8.55 (7c,
18%), 5.50 (7d, 4%), and a trace amount of an unknown
component; Fig. S9. 31P NMR for 7a–7d, respectively, δ:
δ
binaphthyl: 8.08 (d, 1H, J = 9), 8.02 (d, 1H, J = 8.98), 7.97 (d,
1
3
1
1H, J = 8.91), 7.89 (d, 1H, J = 7.42), 7.69 (dd, 1H, J = 8.94,
J = 1.0), 7.47 (t, 1H, J = 8.0), 7.39 (d, 1H, J = 8.90), 7.30
(m, 4H, one due to OH?), 7.25 (d, 1H, J = 8.3), δ: 7.20 (d,
3.95 (dd, JPH = 720, JPH = 9.9); 4.29 (dd, JPH = 720,
3JPH = 9.3); 8.60 (dd, JPH = 704, JPH = 9.0); 5.50 (br d,
1JPH = 725); Fig. S9. Low-resolution ESI MS (CH3OH–
CHCl3): dimer M+ 866.1 (10%), 865.3 (26%), 863.0 (8.8%),
795.3 (3%), 770.3 (3.8%), 707.3 (6.6%), 693.3 (6.6%),
619.3 (8.6%), 605.3 (1.16%), 561.2 (12.9%), 534.1 (26.5%),
532.1 (23%), 517.2 (10.1%); monomer M+ = 433.1
(32.99%), 351 (40.74%), 311 (8.68%), 237 (100%).
1
3
1
1H, J = 9.0), 6.65 (d, 1H, JHP = 703, O=P-H; seen as a sin-
1
glet in the H{31P} spectrum), 3.64 (m, 1H, CH), 1.27–1.07
(m, 8H, CH2), 0.60 (t, 3H, J = 7.30, CH3), 0.72 (t, 3H, J =
1
3
7.30, CH3); Fig. S6. 31P NMR δ: 3.80 (dd, JPH = 707, JPH
10.7); Fig. S7. 31P{1H} NMR δ: 3.80 (s); Fig. S7. 13C{1H}
NMR (1:1 CD3COCD3–CDCl3) δ: 18.08, 18.34, 28.50,
37.36, 37.40, 37,44, 77.50, 114.6, 118.7, 121.5, 121.5,
123.5, 124.8, 125.9, 126.2, 126.9, 127.2, 128.3, 128.5,
130.2, 130.4, 132.0, 134.2, 134.4, 146.5, 146.6, 153.1. MS
(EI): dimer M+ = 896 (0%); M – 286 = 610 (25%), 611
(19%); monomer M+ 448 (8%), 350 (22%), 332 (55%), 286
(100%), 268 (40%), 239 (40%). Low-resolution ESI MS
(CH3OH–CHCl3): dimer M+ 897.3 (17%), 898.3 (6.5%),
899.3 (1.1%), 610 (0%); monomer M+ = 449.1 (24%), 450.1
(4.2%), 352.0 (10.8%), 351.0 (100%), 333.0 (2%), 338.3
(2.2%), 287.1 (2%), 269.1 (1.86%).2
Acknowledgments
We thank the Isfahan University of Technology (Research
Council Grant number 85/500/9143) and the Natural Sci-
ences and Engineering Research Council of Canada
(NSERC) for financial support.
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