The X-ray Structures of (R)-2,2′-Dimethyl-1,1′-binaphthyl and (±)-2-Bromomethyl-2′-dibromomethyl-1,1′-binaphthyl

Article abstract of DOI:10.1007/s10870-020-00876-9

Molecular structures of (R)-2,2′-dimethyl-1,1′-binaphthyl [monoclinic, a = 11.24420 (11), b = 10.56190 (9), c = 13.27180 (13) ?, β = 90.7041 (9)°, space group P2₁] and (±)-2-bromomethyl-2′-dibromomethyl-1,1′-binaphthyl [triclinic, a = 9.4637 (14), b = 9.9721 (18), c = 9.9922 (19) ?, α = 100.093 (5), β = 97.141 (5), γ = 92.585 (4)°, space group P-1] are reported and compared with those of other simple 2,2′-disubstituted-1,1′-binaphthyls. Graphic Abstract: Inter-ring bond length and torsion angles are compared with other simple 2,2′-disubstututed-1,1′-binaphthyls.[Figure not available: see fulltext.]

Full text of DOI:10.1007/s10870-020-00876-9

Journal of Chemical Crystallography
https://doi.org/10.1007/s10870-020-00876-9
ORIGINAL PAPER
The X‑ray Structures of (R)‑2,2′‑Dimethyl‑1,1′‑binaphthyl and (±)‑2‑ꢀro
momethyl‑2′‑dibromomethyl‑1,1′‑binaphthyl
R. Alan Aitken1 · Ryan A. Inwood · Alexandra M. Z. Slawin
1
1
Received: 29 July 2020 / Accepted: 18 December 2020
©
The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature 2021
Abstract
Molecular structures of (R)-2,2′-dimethyl-1,1′-binaphthyl [monoclinic, a=11.24420 (11), b=10.56190 (9), c=13.27180
(
(
13) Å, β=90.7041 (9)°, space group P2 ] and (±)-2-bromomethyl-2′-dibromomethyl-1,1′-binaphthyl [triclinic, a=9.4637
1
14), b=9.9721 (18), c=9.9922 (19) Å, α=100.093 (5), β=97.141 (5), γ=92.585 (4)°, space group P-1] are reported and
compared with those of other simple 2,2′-disubstituted-1,1′-binaphthyls.
Graphic Abstract
Inter-ring bond length and torsion angles are compared with other simple 2,2′-disubstututed-1,1′-binaphthyls.
Br
Me
Me
H
H
H
Br
Br
two molecules, ring
ring torsion angle 87.7°
torsion angle 81.9, 89.6°
Keywords Binaphthyl · Torsion angle · Inter-ring bond length
Introduction
compound 1 has frequently been reported as a non-crystalline
oil, resin or glass both in racemic [4–7] and enantiomerically
pure [8, 9] form. However when we prepared it by reaction
of methymagnesium iodide with the bis(triꢁate) derived from
(R)-BINOL in the presence of (Ph P) NiCl [8], the product
Although the 2,2′-disubstituted-1,1′-binaphthyl structure has
emerged as one of the most powerful and useful molecu-
lar frameworks for asymmetric catalysis, most famously
in the Nobel prize-winning work of Noyori involving the
bis(phosphine) BINAP [1], there are a number of simple deriv-
atives that have not so far been characterised by X-ray diꢀrac-
tion. In the course of recent work to synthesise a chiral diamine
ligand containing this structure [2, 3], we came across two
such compounds that, for diꢀerent reasons, had not been sub-
ject to previous X-ray structure determination. The dimethyl
3
2
2
was obtained as colourless crystals that proved to be suitable
for X-ray diꢀraction. The next stage in the synthesis involved
bromination of 1 with N-bromosuccinimide to form dibromide
2 and, in our hands, this was always accompanied by a small
quantity of the tribromide 3 which could be separated from
2 chromatographically, although with diꢂculty. The forma-
tion of this minor byproduct has been noted in several previ-
ous papers [6, 10] and patents [11–13] but it has never been
1
fully characterised and the only reported data seems to be H
*
R. Alan Aitken
raa@st-and.ac.uk
NMR shifts for the aliphatic protons [14]. By subjecting the
pure racemic dibromide 2 to further bromination and chroma-
tographic separation we were able to isolate 3 in pure form
1
EaStCHEM School of Chemistry, University of St Andrews,
St Andrews, Fife KY16 9ST, UK
Vol.:(0
1
123456789)
3

Journal of Chemical Crystallography
1
13
and characterise it by melting point, H and C NMR and
plug, washing with hexane. The resulting ꢃltrate was con-
centrated in vacuo. The crude residue was puriꢃed by ꢁash
column chromatography (SiO , hexanes), to give at R 0.19
X-ray diꢀraction. The resulting structures of (R)-1 and (±)-
3
are compared with those of other simple symmetrical and
2
f
unsymmetrical 2,2′-disubstituted-1,1′-binaphthyls.
the title compound (100 mg, 17%) as colourless crystals,
m.p. 183−185 °C; δ (Bruker AV400, 400 MHz, CDCl )
H
3
Experimental
8.21 (1 H, d, J 8.8, ArH), 8.12 (1 H, d, J 8.8, ArH), 8.06 (1
H, d, J 8.6, ArH), 7.96−7.92 (2 H, m, ArH), 7.79 (1 H, d,
J 8.6, ArH), 7.54–7.48 (2 H, m, ArH), 7.32–7.26 (2 H, m,
(
R)-(1,1′-binaphthyl)-2,2′-diylbis(triꢁuoromethanesulfo-
nate) was prepared from (R)-BINOL (Fluorochem) using
the published method [14]. (±)-2,2′-Bis(bromomethyl)-
ArH), 7.06−7.00 (2 H, m, ArH), 6.22 (1 H, s, CHBr ), 4.33
2
and 4.14 (2 H, AB pattern, J 10.4, CH Br); δ (125 MHz)
AB
2
C
1
,1′-binaphthyl 2 was prepared [4] by NBS bromination of
137.6 (C), 134.5 (C), 133.7 (C), 133.2 (C), 132.14 (C),
132.06 (C), 131.2 (C), 130.2 (CH), 129.8 (CH), 129.6 (C),
128.1 (CH), 128.0 (CH), 127.8 (CH), 127.61 (CH), 127.59
(CH), 127.25 (CH), 127.16 (CH), 127.0 (CH), 126.7 (CH),
(
±)-2,2′-dimethyl-1,1′-binaphthyl, itself obtained by Grig-
nard mediated coupling [5] of 1-bromo-2-methylnaphthalene
15].
[
1
26.1 (CH), 39.8 (CHBr ) and 31.6 (CH Br).
2 2
(
R)‑2,2′‑Dimethyl‑1,1′‑binaphthyl 1
X-ray diꢀraction data were collected using a Rigaku
XtalLAB P200 (confocal optics) with Cu-Kα radiation at
125 K for 1 and Mo-Kα radiation at 173 K for 3 (data were
integrated using CrysAlis Pro for 1 and CrystalClear for
3). All data were corrected for Lorentz, polarisation and
long-term intensity ꢁuctuations. Absorption eꢀects were
corrected on the basis of multiple equivalent reꢁections.
The structures were solved by direct methods and reꢃned
Following a modiꢃed literature procedure [8], a mixture of
magnesium turnings (4.75 g, 194.8 mmol) in dry Et O (60
2
3
cm ) was placed under an N atmosphere and a single iodine
2
3
crystal was added. Methyl iodide (11.0 cm , 177.1 mmol)
was added dropwise with occasional heating using a heat
gun to maintain reaction. Once the addition was complete
2
(
ca. 10 min) the mixture was allowed to stir with occasional
by full-matrix least-squares against F (SHELXTL [17]).
heating until no further reaction was observed. The resulting
M solution of MeMgI was transferred portionwise via can-
Carbon-bound hydrogen atoms were assigned riding iso-
tropic displacement parameters and constrained to idealised
geometries. Table 1 summarises the X-ray data.
3
nula over 5 min to a stirred solution of (R)-(1,1′-binaphthyl)-
2
,2′-diylbis(triꢁuoromethanesulfonate) (22.15 g, 40.2 mmol)
3
and Ni(PPh ) Cl (1.32 g, 2.0 mmol) in Et O (160 cm )
3
2
2
2
under N at 0 °C. Once the addition was complete the reac-
Results and Discussion
2
tion was stirred overnight at rt and then diluted with EtOAc
3
(
100 cm ). The mixture was cooled to 0 °C and quenched by
Compounds 1 and 3 were prepared using literature meth-
ods (Scheme 1) and in each case slow crystallisation of the
oil obtained from chromatographic puriꢃcation led directly
to crystals suitable for X-ray diꢀraction. The structures of
1 and 3 are similar with the naphthyl rings being close to
orthogonal in both structures. The crystal structure of (R)-1
showed two closely similar molecules in the unit cell (Fig. 1)
which diꢀer mainly in the torsion angle between the two
naphthalene rings (89.6° in the former case vs. 81.9° in the
latter). For the tribromo compound 3 there was a single mol-
ecule in the unit cell (Fig. 2) and the large size of the bro-
mine atoms caused this to adopt a deꢃnite conformation with
the two naphthalene systems at right angles (torsion angle
careful dropwise addition of 1 M HCl solution before being
ꢃltered through Celite. The layers were separated, and the
aqueous layer extracted with EtOAc (× 3). The combined
organic layers were dried and evaporated and the residue was
puriꢃed by ꢁash column chromatography on SiO eluting
2
with hexanes to give an orange oil which slowly crystallised
to give the title compound (8.40 g, 74%) as faintly yellow
crystals. m.p. 67–70 °C (lit. [5] 67–71 °C); [α] = −38.2 (c
D
1
1
.008, CHCl ), (lit. [16] − 35.6 (c 1.0, CHCl )). The H and
3
3
1
3
C NMR spectroscopic data was in accordance with that
previously reported [7].
8
7.7°), the CHBr group oriented to minimise steric interac-
2
(±)‑2‑(ꢀromomethyl)‑2′‑(dibromomethyl)‑1,
1′‑binaphthyl 3
tions with C(19)–H in the plane of the lower ring placing the
two bromines as far as possible from the upper ring, and the
C(2)–C(9) bond oriented to place the CH Br bromine as far
2
To a stirred solution of (±)-2,2′-bis(bromomethyl)-1,1′-
as possible away from the CHBr group.
2
3
binaphthyl 2 (500 mg, 1.14 mmol) in CHCl (10 cm ),
Figures 3 and 4 illustrate the packing in 1 and 3. In 1 we
did not observe any signiꢃcant π–π interactions. There are
weak C–H-π intermolecular contacts: H(9B) and H(19B) to
C(31)–C(38A) mean plane distances are 2.67(1) and 2.83(1)
3
was added AIBN (37 mg, 0.23 mmol) and NBS (243 mg,
1
.37 mmol) and the solution heated under reꢁux for 3 h. The
reaction mixture was cooled to rt and ꢃltered through a silica
1
3

Journal of Chemical Crystallography
Table 1 Crystal data and
CCDC deposit no.
Empirical formula
Crystal system
Space group
2010797
C H
monoclinic
2010798
structure reꢃnement details for
C H Br
(
R)-1 and (±)-3
22 18
22 15
3
triclinic
P-1 (No. 2)
P2 (No. 4)
1
Temperature (K)
Crystal form
125
173
Colourless prism
Colourless prism
0.10×0.10×0.10 mm
a=9.4637(14) Å
b=9.9721(18) Å
c=9.9922(19) Å
α=100.093(5)°
β=97.141(5)°
γ=92.585(4)°
919.0(3)
0
.20×0.20×0.20 mm
Unit cell dimensions
a=11.24420(11) Å
b=10.56190(9) Å
c=13.27180(13) Å
β=90.7041(9)°
Volume (Å3)
1576.04(3)
Z
4
2
–
3
D (g cm )
1.190
0.505 mm
Cu Kα, 1.54184 Å
600.0
1.876
6.605 mm
Mo Kα, 0.71075 Å
504.0
c
–
1
–1
Absorption coeꢂcient
Radiation type, wavelength
F(000)
θ range
Limiting indices
3.330–75.485°
2.079–25.389°
−13≤h≤13,−12≤k≤13,−16≤
−11≤h≤11,−12≤
l≤15
k≤12,−12≤l≤12
Reꢁections collected/unique
Rint
16327/5990
0.0154
33694/3349
0.0501
Data/restraints/parameters
Data with I>2σ(I)
Goodness of ꢃt on F
5990/1/398
5932
1.028
3349/0/226
2947
1.142
2
R , wR (data with I>2σ(I))
0.0390, 0.1058
0.0411, 0.1097
0.21 and−0.27
0.1(9)
0.0566, 0.1829
0.0624, 0.1861
1.15 and−2.48
–
1
2
R , wR (all data)
1
2
–
3
Largest diꢀ. peak/hole (e Å )
Flack parameter
Scheme 1 Synthetic routes used
to obtain compounds 1 and 3
MeMgI
Ni cat.
Tf O
2
OH
OH
OTf
OTf
Me
Me
(
R)-1
NBS
Me
Me
CH
CH
2
Br
Br
CH Br
2
+
CHBr2
2
2
3
(± ±)1
NBS
1
3

Journal of Chemical Crystallography
Fig. 1 The two molecules of 1 showing the numbering system used (ORTEP diagram with ellipsoids at 50% probability level)
Fig. 2 Molecular structure of 3 showing the numbering system used (ORTEP diagram with ellipsoids at 50% probability level) and schematic
representation
1
3

Journal of Chemical Crystallography
Å respectively; H(29B) and H(39B) to C(11)–C(18A) mean
plane distances are 3.00(1) and 2.84(1) Å respectively.
In 3 the packing (Fig. 4) is dominated by the intermo-
lecular Br⋯Br interactions shown more clearly in Fig. 5
compounds with the lowest torsion angle are those bearing
powerfully electron-donating groups such as NH (4), OMe
2
(6) and OEt (7) which all give values below 70°. Most of the
other compounds have torsion angles over 85° but the behav-
iour we have observed for 1 with two diꢀerent molecules in
the unit cell is also observed for compounds 11, 12, 13 and
15 and in the last of these cases there is an 11° diꢀerence in
torsion angle compared to 7.7° for 1. Although having fairly
similar torsion angles, the extremes of inter-ring bond length
are all observed in compounds 11–13 which each have one
form with a long bond and one with a short bond. Except for
the long-bonded molecule of trimethylstannyl compound 13,
compound 3 exhibits the longest inter-ring bond among such
simple compounds at 1.513 Å. This can be compared with
the value of 1.475 Å for 1,1′-binaphthyl itself, which also
shows a low torsion angle of 68.1° [32]. It might be noted
that in many of the structures such as that of BINOL 5 and
the boronic acid 10, there is signiꢃcant hydrogen bonding
which is not possible for either 1 or 3.
[
Br(19)⋯Br(9A) 3.5353(13) Å]. There are no signiꢃcant
π–π overlaps; the C(7)⋯C(7A) and C(6)⋯C(7A) distances
are 3.221(10) and 3.386(10) Å respectively.
By chance these two structures are almost at the extremes
of possible 2,2′-disubstituted binaphthyls, one with two
equivalent small substituents and one with two unequal
very large substituents. We therefore thought it worthwhile
to make a systematic comparison with previously reported
structures for simple 2,2′-disubstituted binaphthyls focusing
particularly on the length of the C(1)–C(1′) bond linking the
two naphthalene rings and the torsion angle betweeen them
(
Fig. 6, Table 2).
It can be seen that the inter-ring bond length varies from
1
.46 to 1.54 Å and the torsion angle from 68 to 90° but
against this background several trends are obvious. The
Fig. 3 Packing of 1 viewed down the b axis
1
3

Journal of Chemical Crystallography
Fig. 4 Packing of 3 viewed down the c axis
R1
R2
4–15
Fig. 5 Detail of intermolecular Br–Br interactions in 3
Fig. 6 General structure of 2,2′-disubstituted-1,1′-binaphthyls
Conclusion
The dimethyl compound 1 shows two molecules in the
unit cell which diꢀer in both inter-ring bond length and
torsion angle, a pattern of behaviour previously noted
for the group 14-substitited derivatives 11–13 and the
methyl hydroxy compound 15. In contrast the tribromo
compound 3 has the its rings nearly orthogonal but with
1
3

Journal of Chemical Crystallography
Table 2 Structural parameters
for 1, 3 and other binaphthyls
R1
R2
Cpd
Ref code
Length
Torsion
Refs.
C1–C1′ (Å)
angle (°)
(
R)-1a
Me
Me
1.494(3)
81.9
89.6
87.7
88.3
68.2
67.6
89.5
78.5
77.3
78.6
69.0
67.9
89.5
88.4
88.3
87.1
88.1
89.6
90.0
89.3
82.7
86.0
85.9
87.0
76.0
This work
1
.497(3)
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
±)-3
CHBr2
CH Br
NH2
NH2
OH
OH
OH
OH
OMe
OEt
CH Br
CH Br
NH2
NH2
OH
OH
OH
OH
OMe
OEt
1.513(9)
1.4947(3)
1.496(3)
1.495(2)
1.500(3)
1.489(3)
1.497(3)
1.494(3)
1.4871(1)
1.492(3)
1.497(7)
1.504(3)
1.499(7)
1.506(6)
1.509(4)
This work
[18]
[19]
[20]
[21]
[22]
[23]
[21]
[24]
[25]
[26]
[27]
[28]
[29]
[29]
2
S)-2
BRMBNP
AJULAS
AJULAS01
BIRKOC01
UKILAC
BUCZIK
WANNII
BUBLIT
LEHLUG
DUWGOR
HUZGUE
PASRAC
ROGMEF
ROGLII
2
2
R)-4
R)-4
±)-5
±)-5
S)-5
R)-5
±)-6
S)-7
R)-8
S)-9
R)-9
±)-10
±)-11
NC
NC
PPh2
PPh2
B(OH)2
SiMe3
PPh2
PPh2
B(OH)2
SiMe3
a
1
.497(4)
1.50(2)
.46(2)
1.54(2)
.47(2)
(
±)-12a
±)-13a
±)-14
ROGLOO
ROGLEE
GeMe3
SnMe3
GeMe3
SnMe3
[29]
[29]
1
(
1
(
(
GIVRIM
KEZYAQ
OH
OH
NH2
Me
1.506(7)
1.489(3)
[30]
[31]
a
S)-15
1
.498(3)
aTwo molecules in unit cell
the bromine-containing groups oriented to minimise steric
interactions and a very long inter-ring bond.
12. Kleiner H-J, Regnat D, Röschert H (1995) Eur Pat 675095 A1
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4. Page PCB, Buckley BR, Farah MM, Blacker AJ (2009) Eur J Org
Chem 2009:3413–3426
Acknowledgements We would like to thank the Engineering and Phys-
ical Sciences Research Council and CRITICAT Centre for Doctoral
Training for ꢃnancial support [Grant Code: EP/L016419/1].
1
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(
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