The influence of a 1,1-diarylvinyl moiety on the photochromism of naphthopyrans

Article abstract of DOI:10.1039/c0ob00141d

1,1,3-Triarylpent-4-en-1-yn-3-ols, efficiently obtained in two steps from 1,1,3-triarylprop-2-yn-1-ols by a Meyer-Schuster rearrangement and subsequent addition of lithium trimethylsilylacetylide, react with either a 1- or 2- naphthol to afford photochrom

Full text of DOI:10.1039/c0ob00141d

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
The influence of a 1,1-diarylvinyl moiety on the photochromism of
naphthopyrans†
Christopher D. Gabbutt, B. Mark Heron,* Colin Kilner and Suresh B. Kolla
Received 18th May 2010, Accepted 25th June 2010
DOI: 10.1039/c0ob00141d
1,1,3-Triarylpent-4-en-1-yn-3-ols, efficiently obtained in two steps from 1,1,3-triarylprop-2-yn-1-ols by
a Meyer-Schuster rearrangement and subsequent addition of lithium trimethylsilylacetylide, react with
either a 1- or 2- naphthol to afford photochromic 1,1-diarylvinyl substituted naphtho[1,2-b]- or
naphtho[2,1-b]-pyrans respectively. Irradiation of solutions of these naphthopyrans results in reversible
electrocyclic ring-opening to afford photomerocyanines which possess an extended conjugated system
and show a bathochromically-shifted lmax relative to the non-vinyl substituted analogues.
A similar bathochromic shift should operate for photochromic
Introduction
naphthopyrans wherein one or more vinyl units are incorporated
between the aryl donor groups and the sp3 hybridised C-atom of
the pyran ring, e.g. 5a. Electrocyclic ring-opening of 5a initiated by
UV irradiation would result in the trienone 6 rather than a typical
dienone tautomer expected from a simple di-aryl substituted
naphthopyran (Scheme 2)7 Interestingly, trienone 6 may either
undergo an 8p-electrocyclisation to afford the naphthoxocine 5b or
a 6p-electrocyclisation to the spirocycle 5c; these alternative modes
of cyclisation offer a hitherto unknown aspect of the normal pyran
electrocylisation. Unsurprisingly, examination of the patent litera-
ture reveals that the incorporation of a monosubstituted vinyl unit
has been previously reported for the 3H-naphtho[2,1-b]pyran e.g.
5a,8 and then extended in claims to include the indole-fused
naphthopyran 79 and most recently for an indenonaphthopyran
8;10 however only in the former account was the influence of the
monoarylvinyl unit on the photochromic properties described.
A common approach employed to shift the wavelength of the
maximum absorption band (lmax) of a dye to longer wavelength,
a bathochromic shift, has been through the introduction of
additional conjugating groups, e.g. vinyl, phenyl, styryl, between
the donor and acceptor units of the dye molecule.1 This approach is
perhaps best known for cyanine dyes e.g. 1, where each additional
vinyl group introduced between the donor and acceptor termini
induces a shift in lmax of ca. 100 nm and is termed the vinylene
shift.2 Bathochromic shifts of varying magnitude in lmax have been
noted for the extension of the conjugating pathway of other dye
classes including benzodifuranones e.g. 2a, b,3 thiopyrylium salts
e.g. 34 and photochromic dithienylethenes5 4a, b (Scheme 1) and
triarylmethines.6
Scheme 1
Scheme 2
We have previously examined a range of colour-structure effects
on the photochromic response of various naphthopyran isomers.11
Of relevance to this current study was the observation that
electron rich 1,1-diarylprop-2-yn-1-ols and 1,1,3-triarylprop-2-yn-
1-ols undergo a facile Meyer-Schuster12 or Rupe rearrangement13
to 3,3-diarylprop-2-enals and 1,3,3-triarylprop-2-enones respec-
tively under the typical reaction conditions employed to access
School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK. E-mail:
b.m.heron@leeds.ac.uk; Fax: +44 (0)113 3436565; Tel: +44 (0)113
3432925
† Electronic supplementary information (ESI) available: 1H, 13C NMR
and IR spectra and HRMS data for all new compounds. CCDC reference
number 777577. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/c0ob00141d
4874 | Org. Biomol. Chem., 2010, 8, 4874–4883
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
Scheme 3
naphthopyrans (Scheme 3).14 It was thought that the latter
unsaturated ketones might serve as precursors for new 1,1,3-
triarylpent-4-en-1-yn-3-ols which in turn would afford novel
3-(1,1-diarylvinyl)-3-aryl substituted 3H-naphtho[2,1-b]pyrans
upon reaction with a 2-naphthol, thus allowing exploration of the
influence of a diarylvinyl group on the photochromic properties of
the naphthopyran system. Precursors that allow for the incorpora-
tion of the 1,1-diarylvinyl unit in the naphthopyran cannot readily
be constructed using the previously reported chalcone-based
derived strategy8 because of the difficulty of the condensation
between electron rich benzophenones and acetophenones which
would lead to 1,3,3-triarylprop-2-enones.15
the acid catalyst–solvent system of choice because of the ease
of catalyst removal from the reaction mixture by simple filtration.
Thus treatment of propynol 10a gave 1,1-bis(4-methoxyphenyl)-3-
phenylprop-2-enone 11a in 70% yield as dark yellow micro-crystals
after elution from silica (20% EtOAc–hexane) (Scheme 3). In a
similar manner, propynols 10b and 10c yielded 11b (65%) and
1
11c (89%) respectively. The H NMR spectra of 11a–c displayed
a singlet at ca. d 7.0 which confirms the rearrangement and
is assigned to the alkene proton. 13C NMR spectroscopy also
supported the rearrangement by the presence of a low field
signal at d 192 for the C O group. This two step protocol
from commercially available benzophenones is more efficient
and convenient than the benzotriazole-mediated process reported
for 11a.20
The unsaturated ketones 11a–c were smoothly and effi-
ciently converted into the respective 1,1,3-triarylpent-4-en-1-yn-
3-ols 12a–c in excellent yield (86–98%) by the addition of
lithium trimethylsilylacetylide with subsequent in situ hydroxide-
promoted desilylation (Scheme 4). The 1H NMR spectrum of 12a
derived from 11a displayed a singlet for the terminal alkyne proton
at d 2.70 and a broadened singlet for hydroxyl proton at d 2.71. The
alkene proton resonated at d 6.33 shifted upfield relative to that
in the ketone precursor 11a. Similar chemical shifts were recorded
for the corresponding protons of the new pent-4-en-1-yn-3-ols 12b
and 12c.
Discussion
Three 1,1,3-triarylprop-2-yn-1-ols 10a–c were expediently ob-
tained (81–99%) by addition of a benzophenone 9 to a lithium
arylacetylide, obtained by deprotonation of the arylacetylene
with n-butyllithium in THF at ca. -70 ◦C, followed by careful
neutralisation of the basic solution and extraction. Notably a
slightly longer reaction time was required for the addition of
phenylacetylide to 4,4¢-dimethylaminobenzophenone to afford
1,1-bis(4-dimethylaminophenyl)-3-phenylprop-2-yn-1-ol 10b. The
1H NMR spectra of 10a–c each displayed a slightly broadened
singlet for the OH group at ca. d 2.8. The equivalent methoxy
groups of 10a resonated at d 3.77 and the dimethylamino groups
of 10b at d 2.93. The 1H NMR spectrum of 10c displayed singlets
for the different methoxy group environments at d 3.78 (6H) and
d 3.79 (3H).
The Meyer-Schuster rearrangement12 of these propynols 10a–c
was explored next. A variety of acidic catalysts such as H2SO4,16
acetic acid,17 AuCl3,18 acidic Al2O3,14 and InCl3 under microwave
heating19 have been used to effect this rearrangement. In this
work, acidic Al2O3 suspended in hot toluene was employed as
Scheme 4
This journal is
The Royal Society of Chemistry 2010
Org. Biomol. Chem., 2010, 8, 4874–4883 | 4875
©

View Article Online
A toluene solution of each of the crude foregoing vinylalkynols
12a–c was heated directly with 2-naphthol in the presence of acidic
alumina according to the established protocol.14 Naphthopyrans
13a and 13c were isolated after flash chromatography in 28% and
52% yield from 12a and 12c respectively (Scheme 4). The 1H NMR
spectrum of 13a was remarkable in that the key pyran ring signal, 2-
H, resonated at d 5.69 shifted upfield by ca. 0.5 ppm relative to the
usual narrow range for this signal at d 6.2.21 This chemical shift is
more akin to that of the corresponding proton (3-H) in simple 2,2-
dialkyl substituted 2H-[1]benzopyrans which appears at ca. d 5.4 –
5.6.22 The chemical shift of 1-H, d 7.23, and the coupling constant
J1,2 = 9.9 Hz are in accordance with those routinely reported for
other naphthopyrans.21 It is likely that 2-H is shielded by one of the
nearby aryl rings on the vinyl moiety. The vinyl proton appeared
as a sharp singlet at d 6.40 and the non-equivalent methoxy groups
resonated at d 3.75 and d 3.76. The 1H NMR spectrum of 13a is
displayed together with that of 13d (expected signal for 2-H at d
6.23 with a coupling constant of 9.9 Hz) to allow a comparison
and afforded signals at ca. d 2.9. The 13C NMR spectrum of 14
provided a signal at d 33.2 assigned to the methine carbon atom
(1-C). The absence of a signal at ~ d 81, present in all known
3,3-diaryl substituted naphtho[2,1-b]pyrans, suggested that the
product lacked a quaternary 3-C atom. A crystallographic analysis
confirmed the structure as 14 (Fig. 2)23 The formation of this
product in which the diarylvinyl unit and the phenyl substituent
are now 1,3-disposed may be rationalised by protonation at 2-C
assisted by the pyran ring oxygen atom. A subsequent sigmatropic
[1,5]-diarylvinyl shift affords a new oxonium ion; the elimination
of a proton from which affords the product 14 (Scheme 5).
Migrations of vinyl groups though relatively scarce have been
1
of the pyran ring and aromatic signals (Fig. 1). The H NMR
spectrum of 13c also indicated an upfield shift for 2-H which
appeared at d 5.66 and with 1-H appearing at d 6.88 for which
J1,2 = 9.9 Hz. The vinyl proton appeared as a sharp singlet at
d 6.42 and the non-equivalent methoxy groups resonated at d
3.75, d 3.76 and d 3.77. The signal for 3-C of the pyran ring of
13a, c appeared in the expected region at d 81.0 in the 13C NMR
spectrum.21
However, a similar reaction of the vinylalkynol 12b with 2-
naphthol gave a complex mixture from which a new compound
14 was isolated in 22% yield after extensive chromatography. The
1H NMR spectrum of 14 showed 1-H as double doublet at d
4.85 coupled to 2-H (d 5.70, J1,2 = 5.1 Hz) and to the vinyl
proton which appeared as a doublet at d 5.89 (J = 9.7 Hz),
respectively. Interestingly the NMe2 groups were non-equivalent
Scheme 5
Fig. 1 1H NMR spectra of vinyl substituted naphthopyran 13a and diaryl naphthopyran 13d.
4876 | Org. Biomol. Chem., 2010, 8, 4874–4883 This journal is The Royal Society of Chemistry 2010
©

View Article Online
Fig. 2 X-Ray crystal structure of compound 14.
documented24 as have acid initiated sigmatropic shifts, for example
the rearrangement of 1-allyl-1-methyl-1H(2)-naphthalenone to 4-
allyl-1-methyl-2-naphthol proceeds by a [3,4]-sigmatropic shift
induced by a catalytic amount of H2SO4.25 Investigations on
the formation of this unexpected product from this study on
photochromic naphthopyrans is ongoing.
Compound 13b displayed an unusual broad absorption spec-
trum which was manifest as a purple-grey shade with an ab-
sorption maximum centred at 566 nm (PhMe) upon irradiation
together with a half-life (t1/2) 6 s (Fig. 4). The non-vinyl ana-
logue of this compound, 3-(4-dimethylaminophenyl)-3-phenyl-
3H-naphtho[2,1-b]pyran 13e has a reported absorption maximum
at 533 nm with half-life of 5.4 s in toluene solution.27,28 Once again
there is no appreciable change in the stability of the ring-opened
species but a significant shift to longer wavelength with a Dlmax
of 33 nm is noted, a value comparable to that observed for the
di(4-methoxyphenyl)vinyl compound 13a.
The reaction of vinylalkynol 12b was repeated but using a
weaker acidic catalyst, Sasol Pural MG-30 (magnesium aluminium
hydroxy carbonate, 30% Mg content on silica), which resulted
in the formation of the expected vinyl substituted naphthopyran
1
13b in 25% yield. The H NMR spectrum of 13b displayed the
key pyran signal for 2-H at d 5.69 and for 1-H at d 6.95 with a
coupling constant of 10.0 Hz. The vinyl proton resonated at d
6.33 as a singlet and the non-equivalent NMe2 groups appeared at
ca. d 2.9. The 13C NMR spectrum of 13b displayed a signal for a
quaternary C atom at d 81.4, confirming the geminal disubstitution
at 3-C.21
The photochromic response of the new naphthopyrans 13 were
examined and compared with structurally close analogues to en-
able the influence of the diarylvinyl unit to be quantified. To enable
a close comparison to be made, the naphthopyran 13d was synthe-
sised from 2-naphthol and 1-(4-methoxyphenyl)-1-phenylprop-2-
yn-1-ol 10d, which was obtained from 4-methoxybenzophenone
and lithium trimethylacetylide in the usual manner. Conversion to
13d was achieved in excellent yield using a combination of pyri-
dinium p-toluenesulfonate (PPTS) and trimethyl orthoformate in
1,2-dichloroethane.26
A toluene solution of 13a (ca. 1 ¥ 10-5 mol dm-3) displayed
an intense red colour under UV irradiation with an absorption
maxima of 502 nm. The half-life (t1/2, the time taken for the
developed colour under steady state conditions to fade to half
of the original intensity) was 9 s. By comparison, naphthopyran
13d appears orange in solution (lmax 465 nm) and has a similar fade
rate with t1/2 of 8 s.21,27 The difference between lmax for these two
analogues, i.e. the vinylene shift, was 37 nm and constitutes a useful
bathochromic shift for a relatively simple structural modification
(Fig. 3).
Irradiation of a solution of 13c resulted in the development of
a red colour with an absorption maximum at 506 nm (PhMe)
with a half-life (t1/2) of 3.2 s (Fig. 5). The non-vinyl analogue,
3,3-bis-(4-methoxyphenyl)-3H-naphtho[2,1-b]pyran 13f has an
absorption maximum of 478 nm and a comparably short half-
life with t1/2 of 2.4 s.27 Once again this simple structural mod-
ification has shown merit with a bathochromic shift of 28 nm.
Irradiation (365 nm) of a CDCl3 solution of 13c resulted in
the development of the expected red colour which gradually
1
faded upon cessation of irradiation. Re-examination of the H
NMR spectrum of the recyclised material gave no indication
of the presence of alternative cyclisation products akin to 5b
and 5c. Additionally TLC examination of this solution in a
series of solvent systems failed to indicate the presence of a new
component.
Noting this bathochromic vinylene shift for the series of
naphthopyrans derived from 2-naphthol it was decided to explore
this effect on the isomeric 2H-naphtho[1,2-b]pyrans derived
from a 1-naphthol. Thus heating 1,1-bis-(4-methoxyphenyl)-3-
phenylpent-1-en-4-yn-3-ol 12a with ethyl 4-hydroxynaphthalene-
2-carboxylate 1529 in toluene containing acidic alumina under
reflux gave ethyl 2-[2,2-bis-(4-methoxyphenyl)vinyl]-2-phenyl-2H-
naphtho[1,2-b]pyran-5-carboxylate 16a in 19% yield (Scheme 5).
The 1H NMR spectrum of 16a displayed a doublet (J = 10 Hz) for
3-H at d 5.80 again shifted upfield relative to that for the non-vinyl
analogues where 3-H resonates at ca. d 6.2.27 The alkene proton
This journal is
The Royal Society of Chemistry 2010
Org. Biomol. Chem., 2010, 8, 4874–4883 | 4877
©

View Article Online
Fig. 3 UV-visible spectra of naphthopyrans 13a and 13d.
Fig. 4 UV-visible spectra of naphthopyrans 13b and 13e.
appears as a sharp singlet at d 6.01. Ethyl 2-(4-methoxyphenyl)-2-
phenyl-2H-naphtho[1,2-b]pyran-5-carboxylate 16b was prepared
for comparative purposes in 75% yield using the PPTS/(MeO)3CH
protocol with naphthol 15 and propynol 10d (Scheme 6). The
1H NMR spectrum of 16b exhibited doublets for the pyran ring
protons, 3-H at d 6.20 and 4-H at d 7.64 (J = 9.4 Hz).21
A toluene solution of naphthopyran 16a displayed a dark cherry
red shade upon UV-irradiation, with an absorption maximum
at 516 nm and t1/2 of 17 s. Its non-vinyl analogue, 16b, has
an absorption maximum of 483 nm and a half-life of 7 s. The
difference between the absorption maximum values (Dlmax) gave a
vinylene shift of 33 nm (Fig. 6) confirming that the effect translates
to the isomeric 2H-naphtho[1,2-b]pyran isomers; interestingly a
longer half-life was noted for the vinyl compound.
Conclusions
The incorporation of a 1,1-diaryl-substituted vinyl unit into the
classical naphthopyran structure enables longer wavelength ab-
sorption bands to be generated through the additional conjugation
consequent upon ring-opening to the merocyanine. This vinylene
4878 | Org. Biomol. Chem., 2010, 8, 4874–4883
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
Fig. 5 UV-visible spectra of naphthopyrans 13c and 13f.
Fig. 6 UV-visible spectra of naphthopyrans 16a and 16b.
Scheme 6
This journal is
The Royal Society of Chemistry 2010
Org. Biomol. Chem., 2010, 8, 4874–4883 | 4879
©

View Article Online
shift of ca. 25–40 nm is observed for both the [2,1-b] and [1,2-b]
naphthopyrans.
ii) 1,1,3-Tris(4-methoxyphenyl)prop-2-yn-1-ol 10c. From 4,4¢-
dimethoxybenzophenone and 4-methoxyphenylacetylene (6.04 g)
81% yield as a viscous pale yellow oil; nmax 1242, 2195, 3675 cm-1;
dH 2.89 (1H, bs, OH), 3.79 (6H, s, (OMe)2), 3.81 (3H, s, OMe),
6.84 (6H, m, Ar–H), 7.41 (2H, m, Ar–H), 7.55 (4H, m, Ar–H).
Spectroscopic data were identical to those reported previously.14,31
Experimental
Unless otherwise stated, reagents were used as supplied. NMR
spectra were recorded on a Bruker Avance 400 MHz spectropho-
tometer (1H NMR 400 MHz, 13C NMR 100 MHz) for sample
solutions in CDCl3 with tetramethylsilane as an internal reference.
The crystal structure determination was carried out at 150 K on a
Bruker-Nonius Apex X8 diffractometer equipped with an Apex
II CCD detector and using graphite monochromated Mo-Ka
radiation from a FR591 rotating anode generator. The structure
was solved by direct methods and refined using SHELXL-97. FT-
IR spectra were recorded on either a Perkin Elmer Spectrum
One spectrophotometer system equipped with a golden gate
ATR attachment (neat sample) or in KBr discs. UV-visible
spectra were recorded in quartz cuvettes (10 mm pathlength) for
spectroscopic grade toluene solutions of the naphthopyrans (ca.
1 ¥ 10-5 mol dm-3) using a Cary 50 Probe spectrophotometer
with activating irradiation provided by a TLC inspection lamp
(Spectroline E Series 365 nm, 8 W). Half-life determinations
were obtained using the Cary 50 Probe spectrophotometer kinetic
analysis software; samples were irradiated at a lamp wavelength
of 365 nm for 5 min with thorough mixing immediately prior to
kinetic data collection. All compounds were homogeneous by TLC
using a range of eluent systems of differing polarity. Mass spectra
were recorded at the National EPSRC Mass Spectrometry Service
Centre, Swansea. Sasol Pural MG-30 (magnesium aluminium
hydroxy carbonate, 30% Mg content on silica) was supplied by
James Robinson Ltd.
General method for acid-catalysed rearrangement of
1,1,3-triarylprop-2-yn-1-ols 10
A stirred solution of 1,1-bis(4-methoxyphenyl)-3-phenylprop-2-
yn-1-ol 10a (5.6 g, 16.5 mmol) in toluene (100 mL) was warmed
to 50 ◦C. Acidic alumina (3.0 g) was added and the mixture
was refluxed until none of the prop-2-yn-1-ol remained by TLC
(~1.5 h). The cooled mixture was filtered and the alumina was
washed with hot toluene (2 ¥ 50 mL). Removal of the toluene from
the combined washings and elution from silica (20% EtOAc in
hexane) gave 1,1-bis(4-methoxyphenyl)-3-phenylprop-2-enone 11a
◦
(3.97 g) 70% yield as deep yellow micro-crystals, m.p. 94–95 C;
n
max 509, 550, 703, 763, 786, 821, 959, 1032, 1185, 1242, 1424, 1507,
1553, 1578, 1596, 1650, 2839, 2933, 3010, 3064 cm-1; dH 3.78 (3H, s,
OMe), 3.85 (3H, s, OMe), 6.80 (2H, m, Ar–H), 6.88 (2H, m, Ar–H),
7.00 (1H, s, alkene-H), 7.12 (2H, m, Ar–H), 7.36 (4H, m, Ar–H),
7.46 (1H, m, Ar–H), 7.89 (2H, m, Ar–H); dC 55.19, 55.40, 113.40,
113.75, 121.40, 128.30, 128.65, 130.32, 131.43, 131.46, 132.39,
134.24, 138.74, 155.13, 159.81, 160.76, 192.55; Found [M+H]+ =
345.1485. C23H20O3 requires [M+H]+ = 345.1489. Spectroscopic
data were identical with that reported previously.20
The following compounds were obtained in this manner:
i) 1,1-Bis(4-dimethylaminophenyl)-3-phenylprop-2-enone 11b.
From 1,1-bis(4-dimethylaminophenyl)-3-phenylprop-2-yn-1-ol
10b (3.82 g) 65% yield after elution from silica (40% EtOAc
in hexane) as orange micro-crystals, m.p. 143–145 ◦C [lit. m.p.
Preparation of 1,1-bis(4-methoxyphenyl)-3-phenylprop-2-yn-1-ol
10a and related 1,1,3-triarylprop-2-yn-1-ols 10b and c
◦
148–149 C,32]; nmax 507, 545, 644, 673, 749, 823, 842, 947, 1017,
1066, 1149, 1188, 1351, 1445, 1516, 1571, 1604, 1650, 1897, 2803,
2892 cm-1; dH 2.96 (6H, s, (NMe2)2), 3.02 (6H, s, (NMe2)2), 6.60
(2H, m, Ar–H), 6.66 (2H, m, Ar–H), 6.92 (1H, m, alkene-H), 7.11
(2H, m, Ar–H), 7.33 (4H, m, Ar–H), 7.44 (1H, m, Ar–H), 7.91
(2H, m, Ar–H); dC 40.27, 105.92, 111.18, 111.42, 117.86, 126.86,
128.10, 128.51, 129.79, 130.61, 131.72, 131.84, 139.83, 150.65,
151.29, 157.89, 191.95; Found [M+H]+ = 371.2118. C25H26N2O
requires [M+H]+ = 371.2117.
n-BuLi (1.6 M in hexanes, 17.3 mmol, 10.8 mL) was added slowly
◦
to a cold (-70 C) stirred solution of the phenylacetylene (1.7 g,
17.3 mmol) in anhydrous THF (70 mL) under nitrogen. Upon
completion of the addition the cold solution was stirred for 30 min.
4,4¢-Dimethoxybenzophenone (4.0 g, 16.5 mmol) was added in
a single portion and the mixture stirred until no benzophenone
remained by TLC (~2 h). The mixture was poured into water
(250 mL) containing saturated aq. NH4Cl solution (40 mL), the
organic layer was separated and the aqueous layer extracted with
EtOAc (3 ¥ 50 mL). The organic extracts were combined and
washed with water (2 ¥ 100 mL) and dried over anhyd. Na2SO4.
Removal of the solvent afforded the 1,1-bis(4-methoxyphenyl)-3-
phenylprop-2-yn-1◦-ol 10a (5.62 g) 99% yield as yellow coloured
solid, m.p. 94–96 C [lit m.p. 92–94 ◦C,14]; nmax 1245, 1605, 2189,
3445 cm-1; dH 2.88 (1H, bs, OH), 3.78 (6H, s, (OMe)2), 6.85 (4H,
m, Ar–H), 7.31 (3H, m, Ar–H), 7.50 (2H, m, Ar–H), 7.55 (4H, m,
Ar–H).
ii) 1,3,3-Tris(4-methoxyphenyl)prop-2-enone 11c. From 1,1,3-
tris(4-methoxyphenyl)prop-2-yn-1-ol 10c (5.33 g) 89% yield as a
glassy oil after elution from silica (5% EtOAc in toluene), nmax 417,
512, 609, 757, 827, 958, 1020, 1111, 1151, 1165, 1214, 1223, 1352,
1419, 1459, 1505, 1595, 1650, 1734, 2837, 2934, 3001 cm-1; dH 3.79
(3H, s, OMe), 3.84 (6H, s, (OMe)2), 6.84 (4H, m, Ar–H), 6.96
(1H, m, alkene-H), 7.11 (2H, m, Ar–H), 7.32 (2H, m, Ar–H), 7.91
(2H, m, Ar–H); dC 55.16, 55.38, 55.43, 113.39, 113.51, 113.70,
121.71, 130.19, 130.98, 131.35, 131.59, 131.61, 134.42, 153.88,
159.67, 160.57, 163.05, 191.25. Spectroscopic data were identical
with that reported previously.14
The following propynols were obtained in this way:
i) 1,1-Bis(4-dimethylaminophenyl)-3-phenylprop-2-yn-1-ol 10b.
From 4,4¢-dimethylaminobenzophenone (5.39 g) 98% yield as a
pale greenish-blue solid, m.p. 161–163 ◦C [lit m.p. 163–164 ◦C,30];
General method for the preparation of
1,1,3-triarylpent-4-en-1-yn-3-ols 12
d
H 2.68 (1H, bs, OH), 2.93 (12H, s, (NMe2)2), 6.69 (4H, m, Ar–H),
n-Butyllithium (1.6 M in hexanes, 9.5 mL, 15.2 mmol) was
added slowly via syringe to a cold (-70 ◦C), stirred solution
7.31 (3H, m, Ar–H), 7.52 (6H, m, Ar–H).
4880 | Org. Biomol. Chem., 2010, 8, 4874–4883
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
of trimethylsilylacetylene (2.15 mL, 15.2 mmol) in anhydrous
tetrahydrofuran (70 mL) under a nitrogen atmosphere. On com-
pletion of the addition (ca. 15 min) the cold solution was allowed
to stir for 1 h. 1,1-Bis(4-methoxyphenyl)-3-phenylprop-2-enone
11a (3.5 g, 10.1 mmol) was added in a single portion and the
mixture stirred at room temperature until TLC examination of
the reaction mixture indicated that none of this ketone remained
(ca. 2 h). The reaction mixture was re-cooled to 0 ◦C and a
solution of methanolic potassium hydroxide [(from potassium
hydroxide (1.1 g, 20 mmol) in methanol (10 mL)] was added in
a single portion. The cooling bath was then removed and the
mixture warmed to room temperature. After ca. 20 min TLC
examination indicated that desilylation was complete. The mixture
was poured into water (300 mL) and carefully neutralised to pH
~ 7 using glacial acetic acid. The organic layer was separated and
the aqueous layer extracted with ethyl acetate (3 ¥ 70 mL). The
combined organic phases were washed with water (3 ¥ 50 mL)
and dried (anhyd. Na2SO4). Removal of the solvent gave the
crude 1,1-bis-(4-methoxyphenyl)-3-phenylpent-4-en-1-yn-3-ol 12a
(3.66 g) 98% yield as a pale yellow viscous oil; nmax 825, 1019,
1167, 1240, 1507, 1593, 1650, 2834, 2935 cm-1; dH 2.66 (1H, s,
alkyne-H), 2.71 (1H, bs, OH), 3.76 (3H, s, OMe), 3.82 (3H, s,
OMe), 6.33 (1H, s, alkene-H), 6.81 (4H, m, Ar–H), 7.10 (4H, m,
Ar–H), 7.25–7.38 (4H, m, Ar–H), 7.60 (2H, m, Ar–H).
acetic acid and then poured into water (700 mL). The organic
layer was separated and the aqueous layer extracted with ethyl
acetate (3 ¥ 100 mL). The organic phases were combined, washed
with water (3 ¥ 100 mL) and dried (anhyd. Na2SO4). Removal of
the solvent gave the title compound 10d as a viscous pale yellow
oil (9.99 g) ◦99% yield whi◦ch gradually solidified upon standing,
m.p. 41–43 C [lit m.p. 43 C33]; nmax 700, 1030, 1174, 1247, 1448,
1585, 1607, 3281, 3422 cm-1; dH 2.84 (1H, s, alkyne-H), 2.98 (1H,
bs, OH), 3.75 (3H, s, OMe), 6.83 (2H, m, Ar–H), 7.27–7.31 (3H,
m, Ar–H), 7.49 (2H, m, Ar–H), 7.58 (2H, m, Ar–H).
Synthesis of 1-(2,2-bis(4-dimethylaminophenyl)vinyl)-3-phenyl-
1H-naphtho[2,1-b]pyran 14
A stirred solution of 2-naphthol (1.09 g, 7.5 mmol) and
the crude 1,1-bis-(4-dimethylaminophenyl)-3-phenylpent-4-en-1-
yn-3-ol 12b (3.0 g, 7.5 mmol) in toluene (80 mL) was warmed
to 50 ◦C. Acidic alumina (2.5 g) was added and the mixture
was heated under reflux until TLC examination indicated that
none of the pent-1-en-4-yn-3-ol remained (ca. 1 h). The mixture
was cooled to ~50 ◦C, filtered and the alumina was washed
with hot toluene (3 ¥ 20 mL). Removal of the toluene from the
combined washings and filtrate gave a viscous brown oil that was
eluted from silica (25% EtOAc in hexane). Recrystallisation from
acetone and MeOH gave 1-(2,2-bis(4-dimethylaminophenyl)vinyl)-
3-phenyl-1H-naphtho[2,1-b]pyran 14 (0.86 g) 22% yield as pale
green micro-crystals, m.p. 221–223 ◦C; vmax 417, 564, 690, 746,
765, 809, 813, 944, 1017, 1097, 1166, 1188, 1221, 1325, 1353, 1516,
1597, 1608, 1665, 2796, 2883 cm-1; dH 2.87 (6H, s, (NMe2)2), 3.05
(6H, s, (NMe2)2), 4.86 (1H, dd, J = 9.7 Hz, 5.1 Hz, 1-H), 5.69
(1H, d, J = 5.1 Hz, 2-H), 5.89 (1H, d, J = 9.7 Hz, alkene-H),
6.53 (2H, m, Ar–H), 6.89 (2H, m, Ar–H), 7.03 (2H, m, Ar–H),
7.28–7.43 (8H, m, Ar–H), 7.61 (1H, m, Ar–H), 7.72 (1H, d, J =
8.8 Hz, 7-H), 7.77 (3H, m, Ar–H); dC 33.25, 40.61, 100.53, 112.03,
112.35, 115.74, 117.99, 123.97, 124.16, 124.66, 126.09, 128.05,
128.29, 128.37, 130.66, 130.73, 132.26, 134.32, 139.11, 147.82,
148.44, 149.77; Found [M+H]+ = 523.2744. C37H34N2O requires
[M+H]+ = 523.2747.
Other compounds prepared using this protocol:
i) 1,1-Bis-(4-dimethylaminophenyl)-3-phenylpent-4-en-1-yn-3-ol
12b. From
1,1-bis(4-dimethylaminophenyl)-3-phenylprop-2-
enone 11b as a straw coloured viscous oil (2.29 g) 86% yield; nmax
828, 1024, 1165, 1237, 1514, 1591, 1653, 2839, 2936 cm-1; dH 2.69
(1H, s, alkyne-H), 2.92 (6H, s, (NMe2)2), 2.97 (6H, s, (NMe2)2),
3.04 (1H, bs, OH), 6.23 (1H, s, alkene-H), 6.59 (2H, m, Ar–H),
6.67 (2H, m, Ar–H), 7.09 (2H, m, Ar–H), 7.13 (2H, m, Ar–H),
7.28 (1H, m, Ar–H), 7.32 (2H, m, Ar–H), 7.66 (2H, m, Ar–H).
ii) 1,1,3-Tris-(4-methoxyphenyl)pent-4-en-1-yn-3-ol 12c. From
1,3,3-tris(4-methoxyphenyl)prop-2-en-one 11c as a viscous yellow
oil (5.74 g) 96% yield; nmax 826, 1021, 1164, 1233, 1504, 1595, 1649,
2836, 2933 cm-1; dH 2.63 (1H, s, alkyne-H), 2.64 (1H, bs, OH), 3.78
(3H, s, OMe), 3.810 (3H, s, OMe), 3.816 (3H, s, OMe), 6.33 (1H, s,
alkene-H), 6.76–6.86 (6H, m, Ar–H), 7.08 (2H, m, Ar–H), 7.13
(2H, m, Ar–H), 7.52 (2H, m, Ar–H).
Preparation of 3-[2,2-bis-(4-methoxyphenyl)vinyl]-3-phenyl-3H-
naphtho[2,1-b]pyran 13a and related diarylvinyl substituted
naphthopyrans 13c and 16a
Preparation of 1-(4-methoxyphenyl)-1-phenylprop-2-yn-1-ol 10d
A stirred solution of 2-naphthol (0.39 g, 2.7 mmol) and 1,1-bis-
(4-methoxyphenyl)-3-phenylpent-4-en-1-yn-3-ol 12a (1.0 g, 2.7
mmol) in toluene (40 mL) was warmed to 50 ◦C. Acidic alumina
(1.5 g) was added and the mixture was heated under reflux until
TLC examination indicated that none of the pent-1-en-4-yn-3-ol
remained (ca. 1 h). The mixture was cooled to ~50 ◦C, filtered
and the alumina was washed with hot toluene (2 ¥ 20 mL).
Removal of the toluene from the combined washings and filtrate
gave a viscous brown oil that was eluted from silica (30% EtOAc
in hexane); recrystallisation from acetone/MeOH gave 3-[2,2-
bis-(4-methoxyphenyl)vinyl]-3-phenyl-3H-naphtho[2,1-b]pyran 13a
(0.37 g) 28% yield as colourless micro-crystals, m.p. 101–103 ◦C;
lmax 502 nm (PhMe); vmax 526, 545, 585, 678, 700, 730, 804, 963,
1018, 1032, 1088, 1173, 1249, 1298, 1461, 1507, 1603, 1626, 2837,
2959, 3008 cm-1; dH 3.756 (3H, s, OMe), 3.760 (3H, s, OMe), 5.69
(1H, d, J = 9.9 Hz, 2-H), 6.40 (1H, s, alkene-H), 6.69 (2H, m,
n-Butyllithium (1.6 M in hexanes, 31.8 mL, 50.5 mmol) was
added slowly via syringe to a cold (-78 ◦C), stirred solution
of trimethylsilylacetylene (7.20 mL, 50.8 mmol) in anhydrous
tetrahydrofuran (120 mL) under a nitrogen atmosphere. On
completion of the addition the cold solution was allowed to stir
for 1 h. 4-Methoxybenzophenone (9.0 g, 42.4 mmol) was added
in a single portion and the mixture stirred at room temperature
until TLC examination of the reaction mixture indicated that none
of the benzophenone remained (ca. 2 h). The reaction mixture
was re-cooled to 0 ◦C and a solution of methanolic potassium
hydroxide [(from potassium hydroxide (4.7 g, 84.8 mmol) in
methanol (50 mL)] was added in a single portion. The cooling bath
was then removed and the mixture warmed to room temperature,
after ca. 20 min TLC examination indicated that desilylation was
complete. The mixture was neutralised to pH ~ 7 using glacial
This journal is
The Royal Society of Chemistry 2010
Org. Biomol. Chem., 2010, 8, 4874–4883 | 4881
©

View Article Online
Ar–H), 6.74 (2H, m, Ar–H), 6.86 (2H, d, J = 8.8 Hz, 5-H, Ar–H),
6.90 (2H, m, Ar–H), 7.11 (2H, m, Ar–H), 7.23 (1H, d, J = 9.9 Hz,
1-H), 7.30 (3H, m, Ar–H), 7.42 (1H, m, Ar–H), 7.53–7.58 (3H, m,
Ar–H), 7.69 (1H, d, J = 8.0 Hz, 7-H), 7.83 (1H, d, J = 8.4 Hz, 10-
H); dC 55.19, 55.26, 81.09, 112.77, 113.33, 113.95, 117.87, 118.28,
121.27, 123.34, 126.25, 126.33, 127.02, 127.36, 128.17, 128.42,
128.77, 129.17, 129.18, 129.70, 130.50, 131.40, 132.13, 135.73,
143.23, 145.85, 150.52, 158.68, 159.20; Found [M]+ = 496.2028.
C35H28O3 requires [M]+ = 496.2033.
2-naphthol and 1,1-bis-(4-dimethylaminophenyl)-3-phenylpent-4-
en-1-yn-3-ol 12b after elution from silica (30% EtOAc in hexane)
and recrystallisation from acetone/MeOH (0.41 g) 25% yield as
very pale green coloured micro-crystals, m.p. 170–172 ◦C; vmax
513, 692, 748, 811, 902, 945, 1017, 1081, 1126, 1191, 1208, 1350,
1445, 1516, 1601, 2796 cm-1; lmax 566 nm (PhMe); dH 2.90 (6H, s,
(NMe2)2), 2.91 (6H, s, (NMe2)2), 5.69 (1H, d, J = 10.0 Hz, 2-H),
6.33 (1H, s, alkene-H), 6.51 (2H, m, Ar–H), 6.56 (2H, m, Ar–H),
6.81 (1H, d, J = 10.0 Hz, 1-H), 6.88 (2H, m, Ar–H), 6.95 (1H,
d, J = 8.7 Hz, 5-H), 7.09 (2H, m, Ar–H), 7.21 (1H, m, Ar–H),
7.27–7.31 (3H, m, Ar–H), 7.41 (1H, app. t, J = 7.3 Hz, 9-H), 7.57
(3H, m, Ar–H, 6-H), 7.69 (1H, d, J = 8.0 Hz, 7-H), 7.82 (1H, d, J =
8.4 Hz, 10-H); dC 39.63, 40.49, 40.61, 81.42, 111.36, 111.77, 114.32,
117.41, 118.47, 121.35, 123.18, 126.15, 126.37, 127.17, 127.58,
128.05, 128.26, 128.38, 128.58, 128.89, 129.16, 129.76, 131.27,
131.75, 144.29, 146.39, 149.59, 150.00, 150.78; Found [M+H]+ =
523.2739. C37H34N2O3 requires [M+H]+ = 523.2744.
The following naphthopyrans were obtained using a similar
method:
i) 3-[2,2-Bis-(4-methoxyphenyl)vinyl]-3-(4-methoxyphenyl)-3H-
naphtho[2,1-b]pyran 13c. From 2-naphthol and 1,1,3-tris-(4-
methoxyphenyl)pent-4-en-1-yn-3-ol 12c after elution from silica
(30% DCM in hexane) and recrystallisation from acetone/MeOH
gave the title compound (1.02 g) 52% yield as pale purple coloured
micro-crystals, m.p. 125–127 ◦C; vmax 426, 549, 584, 719, 752, 804,
837, 961, 1018, 1029, 1081, 1173, 1252, 1298, 1452, 1506, 1603,
1629, 2836, 2954, 3064 cm-1; lmax 506 nm (PhMe); dH 3.75 (3H, s,
OMe), 3.76 (3H, s, OMe), 3.77 (3H, s, OMe), 5.66 (1H, d, J =
9.9 Hz, 2-H), 6.42 (1H, s, alkene-H), 6.69 (2H, m, Ar–H), 6.74
(2H, m, Ar–H), 6.82 (3H, d, J = 8.8 Hz, 5-H, Ar–H), 6.88 (3H,
m, 1-H, Ar–H), 7.11 (2H, m, Ar–H), 7.29 (1H, m, Ar–H), 7.41
(1H, m, Ar–H), 7.44 (2H, m, Ar–H), 7.55 (1H, d, J = 8.8 Hz,
6-H), 7.69 (1H, d, J = 8.0 Hz, 7-H), 7.84 (1H, d, J = 8.4 Hz, 10-
H); dC 55.20, 55.26, 80.96, 112.80, 113.33, 113.48, 114.01, 117.93,
118.33, 121.26, 123.306, 126.311, 126.99, 127.78, 128.42, 128.75,
129.12, 129.16, 129.70, 130.79, 131.38, 132.19, 135.82, 137.96,
142.74, 150.49, 158.65, 158.83, 159.17; Found [M+H]+ = 527.2213.
C36H30O4 requires [M+H]+ = 527.2217.
General method for preparation of naphthopyrans 13d and 16b
using pyridinium p-toluenesulfonate catalysis
A stirred solution of 2-naphthol (2.0 g, 13.8 mmol), the 1-(4-
methoxyphenyl)-1-phenylprop-2-yn-1-ol 10d (3.6 g, 15.2 mmol),
trimethyl orthoformate (2.9 g, 27.7 mmol) with catalytic amount
of PPTS in 1,2-dichloroethane (70 mL) was heated under reflux
until TLC examination indicated that none of the prop-2-yn-1-ol
remained (ca. 1 h). The mixture was cooled to ~50 ◦C and washed
with water (2 ¥ 50 mL). Removal of the combined solvent gave
the crude compound which was eluted from silica (70% DCM
in hexane), followed by recrystallisation from acetone/MeOH to
afford 3-(4-methoxyphenyl)-3-phenyl-3H-naphtho[2,1-b]pyran 13d
◦
as colourless micro-crystals (4.67 g) 93% yield, m.p. 146–149 C
◦
[lit. m.p. 154–157 C,34]; lmax 465 nm (PhMe); nmax 422, 571,
ii)
Ethyl
2-[2,2-bis-(4-methoxyphenyl)vinyl]-2-phenyl-2H-
naphtho[1,2-b]pyran-5-carboxylate 16a. From ethyl-4-hydroxy-
naphthalene-2-carboxylate 15 and 1,1-bis-(4-methoxyphenyl)-
3-phenylpent-4-en-1-yn-3-ol 12a after elution from silica (50%
DCM in hexane) and recrystallisation from acetone/MeOH, as
pale yellow micro-crystals (0.40 g) 19% yield, m.p. 191–193 ◦C;
vmax 515, 541, 585, 617, 698, 760, 829, 837, 965, 995, 1026, 1104,
1175, 1195, 1290, 1364, 1450, 1506, 1572, 1604, 1711, 2836,
2953 cm-1; lmax 516 nm (PhMe); dH 1.42 (3H, t, 7.1 Hz, CH2CH3),
3.73 (3H, s, OMe), 3.77 (3H, s, OMe), 4.38 (2H, q, J = 7.1 Hz,
CH2CH3), 5.80 (1H, d, J = 10.0 Hz, 3-H), 6.49 (1H, s, alkene-H),
6.65 (2H, m, Ar–H), 6.75 (2H, m, Ar–H), 6.90 (2H, m, Ar–H),
7.12 (2H, m, Ar–H), 7.20 (1H, m, Ar–H), 7.23–7.28 (3H, m,
4-H, Ar–H), 7.44 (2H, m, 8-H, 9-H), 7.51 (2H, m, Ar–H), 7.75
(1H, m, 7-H), 7.92 (1H, m, 10-H), 8.00 (1H, bs, 6-H); dC 14.37,
55.15, 55.28, 60.98, 81.04, 112.96, 113.37, 114.62, 120.80, 122.34,
124.15, 124.72, 126.09, 126.52, 126.78, 127.35, 128.17, 128.55,
128.70, 131.10, 131.21, 132.08, 132.40, 135.77, 142.91, 145.67,
148.57, 158.62, 159.23, 167.08; Found [M]+ = 568.2244. C38H32O5
requires [M]+ = 568.2246.
766, 934, 1080, 1217, 1302, 1448, 1509, 1581, 1609, 1630, 2959,
3064 cm-1; dH 3.76 (3H, s, OMe), 6.23 (1H, d, J = 9.9 Hz, 2-H),
6.82 (2H, m, Ar–H), 7.18 (1H, d, J = 8.8 Hz, 5-H), 7.24 (1H, m,
Ar–H), 7.32 (4H, m, Ar–H, 1-H), 7.38 (2H, m, Ar–H), 7.46 (3H,
m, Ar–H), 7.65 (1H, d, J = 8.8 Hz, 6-H), 7.71 (1H, d, J = 8.0 Hz, 7-
H), 7.95 (1H, d, J = 8.4 Hz, 10-H); dC 55.22, 82.33, 113.37, 113.94,
118.35, 119.35, 121.30, 123.54, 126.57, 126.86, 127.40, 127.86,
128.05, 128.49, 129.27, 129.76, 136.91, 145.07, 150.52, 158.90.
The following pyran was also obtained using this method:
i) Ethyl 2-(4-methoxyphenyl)-2-phenyl-2H-naphtho[1,2-b]pyran-
5-carboxylate 16b. From ethyl 4-hydroxynaphthalene-2-
carboxylate 15 and 1-(4-methoxyphenyl)-1-phenylprop-2-yn-1-ol
10d after elution from silica (50% DCM in hexane) and
recrystallisation from acetone/MeOH, as colourless micro-
crystals (0.39 g) 75% yield m.p. 102–103 ◦C; nmax 414, 538, 566,
591, 677, 697, 748, 770, 803, 839, 961, 997, 1012, 1041, 1056,
1181, 1200, 1244, 1291, 1363, 1377, 1448, 1510, 1583, 1609, 1708,
2903, 2978 cm-1; lmax 483 nm (PhMe); dH 1.41 (3H, t, J = 6.8 Hz,
CH2CH3), 3.71 (3H, s, OMe), 4.39 (2H, q, J = 6.8 Hz, CH2CH3),
6.20 (1H, d, J = 9.9 Hz, 3-H), 6.81 (2H, m, Ar–H), 7.23 (1H, m,
Ar–H), 7.30 (2H, m, Ar–H), 7.42 (2H, m, Ar–H), 7.46–7.51 (3H,
m, Ar–H), 7.56 (1H, app. t, J = 7.5 Hz, Ar–H), 7.65 (1H, d, J =
9.9 Hz, 4-H), 7.78 (1H, d, J = 8.0 Hz, 7-H), 8.06 (1H, s, 6-H), 8.35
(1H, d, J = 8.5 Hz, 10-H); dC 14.81, 55.60, 61.45, 82.76, 113.91,
115.40, 122.56, 122.65, 125.02, 125.20, 126.78, 127.43, 127.83,
128.22, 128.34, 128.55, 128.82, 129.25, 133.13, 137.29, 145.56,
3-[2,2-Bis-(4-dimethylaminophenyl)vinyl]-3-phenyl-3H-
naphtho[2,1-b]pyran 13b
This was obtained using the foregoing method for the preparation
of 13a, c, and 16a but using Sasol Pural MG-30 (magnesium
aluminium hydroxy carbonate, 30% Mg content on silica) 1.5 g as
the catalyst in place of acidic alumina. The title compound from
4882 | Org. Biomol. Chem., 2010, 8, 4874–4883
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
149.00, 159.43, 167.45; Found [M+H]+ = 437.1750. C29H24O4
requires [M+H]+ = 437.1747.
13 H. Rupe, Helv. Chim. Acta, 1926, 9, 672.
14 C. D. Gabbutt, B. M. Heron, A. C. Instone, D. A. Thomas, S. M.
Partington, M. B. Hursthouse and T. Gelbrich, Eur. J. Org. Chem.,
2003, 1220–1230.
15 Yu. G. Yatluk, V. Ya. Sosnovskikh and A. L. Suvorov, Russ. J. Org.
Acknowledgements
Chem., 2004, 40, 763–765.
16 K. H. Meyer and K. Schuster, Chem. Ber., 1922, 55, 819.
17 M. Edens, D. Boerner, C. Roane Chase, D. Nass and M. D. Schiavelli,
J. Org. Chem., 1977, 42, 3403–3408.
18 D. A. Engel and G. B. Dudley, Org. Lett., 2006, 8, 4027–4029.
19 V. Cadierno, J. Francos and J. Gimeno, Tetrahedron Lett., 2009, 50,
4773–4776.
The authors thank James Robinson Ltd. (Huddersfield, UK) and
Yorkshire Forward for a research studentship to SBK and the
EPSRC for access to the National Mass Spectrometry Service
(Swansea). The Worshipful Company of Clothworkers’ of the City
of London are thanked for a millennium grant for the purchase
of a Bruker Avance NMR spectrophotometer and for an annual
grant for the purchase of a Cary 50 Probe spectrophotometer.
Dr Steven Partington (James Robinson Ltd.) is thanked for his
technical assistance in the evaluation the photochromic properties
of the photochromic compounds.
20 A. R. Katritzky, S. N. Denisenko, D. C. Oniciu and I. Ghiviriga, J. Org.
Chem., 1998, 63, 3450–3453.
21 J. D. Hepworth and B. M. Heron in Functional Dyes, ed. S.-H. Kim,
Elsevier, Amsterdam, 2006, 85–135.
22 J. D. Hepworth, C. D. Gabbutt and B. M. Heron in Comprehensive
Heterocyclic Chemistry II, ed. A. R. Katritzky, C. W. Rees and
E. F. V. Scriven, Pergamon (Elsevier) , Amsterdam, 1996, vol. 5,
pp. 301–350.
23 Crystallographic data for compound 14 (CCDC 777577): Formula =
C37H34N2O; Formula weight = 522.66; Size = 0.19 ¥ 0.11 ¥ 0.05 mm;
Crystal morphology = colourless fragment; T = 150 K, Wavelength =
References
˚
1 Colour and Constitution of Organic Molecules, ed. J. Griffiths, Academic
Press, London, 1976; Colour Chemistry (2nd Edition), ed. H. Zollinger,
VCH, Weinheim, 1991; Heterocyclic Polymethine Dyes (Topics in
Heterocyclic Chemistry 14), ed. L. Strekowski, Springer-Verlag, Berlin,
2008.
2 Infrared Absorbing Dyes, ed. M. Matsuoka, Plenum Press, New York,
1990; G. Bach, S. Daehne, in Second Supplements to the 2nd Edition of
Rodd’s Chemistry of Carbon Compounds, Vol. IV, B, ed. M. Sainsbury,
Elsevier, Amsterdam, 1997, pp. 383–481; A. Mishra, R. K. Behera,
P. K. Behera, B. K. Mishra and G. B. Behera, Chem. Rev., 2000, 100,
1973–2011.
0.71073 A [Mo-Ka]; Crystal system = orthorhombic; Space g◦roup =
˚
P212121;Unit cell dimensions, a = 10.9909(10) A, a = 90 , b =
◦
◦
˚
˚
13.0053(11) A, b = 90 , c = 20.0553(18) A, g = 90 ; Volume = 2866.7(4)
3
-3
˚
A ; Z = 4; Density (calculated) = 1.211 Mg m ; Absorption coefficient
0.072 mm-1; F(000) = 1112; Data collection range = 2.57 £ q £ 27.94◦;
Index ranges = -13 £ h £ 14, -14 £ k £ 17, -25 £ l £ 26; Reflections
collected = 27053; Independent reflections = 3842 [R(int) = 0.0786];
Observed reflections = 2744 [I > 2s(I)]; Absorption correction = multi-
scan; Max. and min. transmission = 0.9964 and 0.8278; Refinement
method = Full; Data/restraints/parameters = 3114/0/365; Goodness
of fit = 1.063; Final R indices [I > 2s(I)] R1 = 0.0431, wR2 = 0.0957;
R indices (all data): R1 = 0.0669, wR2 = 0.1087; Largest diff. peak and
3 G. Hallas and C. Yoon, Dyes Pigm., 2001, 48, 121–132.
4 J. D. Hepworth and B. M. Heron in Comprehensive Heterocyclic
Chemistry III, ed. D. StC. Black, Elsevier, Amsterdam, 2008, vol. 7,
pp. 931–932.
-3
˚
hole = 0.190 and -0.182e A .
24 M. F. Semmelhack, H. N. Weller and J. S. Foos, J. Am. Chem. Soc.,
1977, 99, 292–294; H. S. Chong, J. H. Seong and Y. S. Paik, J. Kor.
Chem. Soc., 1993, 37, 910–916.
5 M. Irie, Chem. Rev., 2000, 100, 1685–1716.
6 S. Akiyama, S. Nakatsuji, K. Nakashima, M. Watanabe and H.
Nakazumi, J. Chem. Soc., Perkin Trans. 1, 1988, 3155–3161; H.
Muramatsu, A. Okumura, K. Shibata and M. Matsui, Chem. Ber., 1994,
127, 1627–1632; S. G. R. Guinot, J. D. Hepworth and M. Wainwright,
Dyes Pigm., 2000, 47, 129–142.
7 J. D. Hepworth and B. M. Heron, in Progress in Heterocyclic Chemistry,
ed. G. W. Gribble and J. A. Joule, Elsevier, Amsterdam, 2005, vol. 17,
pp. 33–62; B. Van Gemert in Organic Photochromic and Thermochromic
Compounds, Volume 1 Main Photochromic Families, ed. J. C. Crano and
R. J. Guglielmetti, Plenum Press, New York, 1998, 111–140.
8 B Van Gemert, US Pat., 5 274 132, 1993.
25 B. Miller and M. R. Saidi, Tetrahedron Lett., 1972, 13, 4391–4393;
B. Miller and M. R. Saidi, J. Am. Chem. Soc., 1976, 98, 2227–
2238.
26 W. Zhao and E. M. Carreira, Org. Lett., 2003, 5, 4153–4154.
27 J. D. Hepworth, C. D. Gabbutt and B. M. Heron, in Colour Science
’98 Volume 1 Dye and Pigment Chemistry, ed. J. Griffiths, University of
Leeds, (Leeds, UK), 1999, 161–173.
28 O. A. Fedorova, F. Maurel, E. N. Ushakov, V. B. Nazarov, S. P. Gromov,
A. V. Chebunkova, A. V. Feofanov, I. S. Alaverdian, M. V. Alfimov and
F. Barigelletti, New J. Chem., 2003, 27, 1720–1730.
29 C. Fuganti and S. Serra, J. Chem. Res. (M), 1998, 2769–2782, (S) 638–
639; C. D. Gabbutt, J. D. Hepworth, B. M. Heron, D. A. Thomas, C.
Kilner and S. M. Partington, Heterocycles, 2004, 63, 567–582.
30 S. Akiyama, K. Yoshida, M. Hayashida, K. Nakashima, S. Nakatsuji
and M. Iyoda, Chem. Lett., 1981, 311–314; E. A. Dikusar, Russ. J. Gen.
Chem., 2003, 73, 1406–1409.
9 J. Momota, K. Omuro and H. Nago, Japanese Pat., JP2000229973,
2000.
10 A. Chopra, B.-K. Kim and B. Van Gemert, US Pat., 0 138 449, 2007.
11 C. D. Gabbutt, T. Gelbrich, J. D. Hepworth, B. M. Heron, M. B.
Hursthouse and S. M. Partington, Dyes Pigm., 2002, 54, 79–93; C. D.
Gabbutt, B. M. Heron and A. C. Instone, Heterocycles, 2003, 60, 843–
855; C. D. Gabbutt, B. M. Heron, A. C. Instone, P. N. Horton and M. B.
Hursthouse, Tetrahedron, 2005, 61, 463–471; D. Gabbutt, B. M. Heron
and A. C. Instone, Tetrahedron, 2006, 62, 737–745; C. D. Gabbutt,
B. M. Heron, S. B. Kolla, C. Kilner, S. J. Coles, P. N. Horton and M. B.
Hursthouse, Org. Biomol. Chem., 2008, 6, 3096–3104.
31 E. McDonald and P. Smith, J. Chem. Soc., Perkin Trans. 1, 1980, 837–
842.
32 I. A. Poletaeva and O. F. Ginzbergm, Zhur. Org. Khim., 1968, 4, 440–
445.
33 J. Rauss-Godineau, W. Chodkiewicz and P. Cadiot, Bull. Soc. Chim.
Fr., 1966, 2885–2892.
12 D. A. Engel and G. B. Dudley, Org. Biomol. Chem., 2009, 7, 4149–4158;
S. Swaminathan and K. V. Narayanan, Chem. Rev., 1971, 71, 429–438.
34 K. Tanaka, H. Aoki, H. Hosomi and S. Ohba, Org. Lett., 2000, 2,
2133–2134.
This journal is
The Royal Society of Chemistry 2010
Org. Biomol. Chem., 2010, 8, 4874–4883 | 4883
©