Diarylamino groups as photostable auxofluors in 2-benzoxazolylfluorene, 2,5-diphenyloxazoles, 1,3,5-hexatrienes, 1,4-distyrylbenzenes, and 2,7-distyrylfluorenes

Article abstract of DOI:10.1021/jo020333+

The relationship of structure to optical spectral properties was determined for five types of fluors in a search for an optimum-wavelength shifter to be used as part of the detection systems for high-energy particles from accelerators. In a search for photostable fluors to serve as waveshifters in plastic fibers it was found that the wavelengths of interest, absorption max 410 ± 10 nm and fluorescence emission max 480 ± 20 nm, along with other properties, such as high solubility and short fluorescence decay time, could be obtained from fluorophors composed of aromatic rings and vinyl groups only by using amino groups as auxochromes to give bathochromic shifts of wavelengths. Since primary, monoalkyl, and dialkylamino groups were not sufficiently photostable, a number of fluorophores bearing diarylamino groups were investigated. Syntheses of the fluors made use of the Buchwald amination, an improved version of the Emmons-Horner reaction, and other common reactions. The fluor types were the following: a 2-benzoxazolyl-7-(4-diarylamino)fluorene 7, 2-(4-cyanophenyl)-5-(4-aminophenyl)oxazoles 14 and 20, 1,3,5-hexatrienes 24a-d and 26a-c, 1,4-distyrylbenzenes 31d-g and 32a-e, and 2,7-distyrylfluorenes 40a,d-e. The unsymmetrical fluors 7, 14, and 20 were not as bright as the best hexatrienes, distyrylbenzenes, and distyrylfluorenes, which were all symmetrical. Where the 1,6-diaryl-1,3,5-hexatrienes 24a-d had high fluorescence quantum yield (Φ_f), the 1,1,6,6-tetraryl-1,3,5-hexatrienes 26a-c had both lower ε and Φ_f. Where the 1,4-distyrylbenzenes 31d-g had high Φ_f, the 1,4-bis(2-phenylstyryl)benzenes 32a-e had (Φ_f = 0. Diarylamino groups as auxofluors conferred higher photochemical stability than dialkylamino groups on similar fluorophores. The 1,4-distyrylbenzenes 31d,e and the 2,7-distyrylfluorenes 40d,e had the most desirable properties overall, which included fast decay times of 2 ns. Computer simulations predicted absorption and emission wavelengths fairly well, but were of little help for the prediction of brightness, stability, Φ_f, or decay time.

Full text of DOI:10.1021/jo020333+

Dia r yla m in o Gr ou p s a s P h otosta ble Au xoflu or s in
2-Ben zoxa zolylflu or en e, 2,5-Dip h en yloxa zoles, 1,3,5-Hexa tr ien es,
1,4-Distyr ylben zen es, a n d 2,7-Distyr ylflu or en es
J oel M. Kauffman* and Guillermo Moyna
Department of Chemistry & Biochemistry, University of the Sciences in Philadelphia,
600 South 43rd Street, Philadelphia, Pennsylvania 19104
kauffman@hslc.org; j.kauffm@usip.edu
Received May 13, 2002
The relationship of structure to optical spectral properties was determined for five types of fluors
in a search for an optimum-wavelength shifter to be used as part of the detection systems for high-
energy particles from accelerators. In a search for photostable fluors to serve as waveshifters in
plastic fibers it was found that the wavelengths of interest, absorption max 410 ( 10 nm and
fluorescence emission max 480 ( 20 nm, along with other properties, such as high solubility and
short fluorescence decay time, could be obtained from fluorophors composed of aromatic rings and
vinyl groups only by using amino groups as auxochromes to give bathochromic shifts of wavelengths.
Since primary, monoalkyl, and dialkylamino groups were not sufficiently photostable, a number of
fluorophores bearing diarylamino groups were investigated. Syntheses of the fluors made use of
the Buchwald amination, an improved version of the Emmons-Horner reaction, and other common
reactions. The fluor types were the following: a 2-benzoxazolyl-7-(4-diarylamino)fluorene 7, 2-(4-
cyanophenyl)-5-(4-aminophenyl)oxazoles 14 and 20, 1,3,5-hexatrienes 24a -d and 26a -c, 1,4-
distyrylbenzenes 31d -g and 32a -e, and 2,7-distyrylfluorenes 40a ,d -e. The unsymmetrical fluors
7, 14, and 20 were not as bright as the best hexatrienes, distyrylbenzenes, and distyrylfluorenes,
which were all symmetrical. Where the 1,6-diaryl-1,3,5-hexatrienes 24a -d had high fluorescence
quantum yield (Φf), the 1,1,6,6-tetraryl-1,3,5-hexatrienes 26a -c had both lower ꢀ and Φf. Where
the 1,4-distyrylbenzenes 31d -g had high Φf, the 1,4-bis(2-phenylstyryl)benzenes 32a -e had Φf )
0. Diarylamino groups as auxofluors conferred higher photochemical stability than dialkylamino
groups on similar fluorophores. The 1,4-distyrylbenzenes 31d ,e and the 2,7-distyrylfluorenes 40d ,e
had the most desirable properties overall, which included fast decay times of 2 ns. Computer
simulations predicted absorption and emission wavelengths fairly well, but were of little help for
the prediction of brightness, stability, Φf, or decay time.
In tr od u ction
disssolved in PS, which can be fabricated into large or
intricate shapes. While the wavelength maxima of ab-
sorption and fluorescence of potential fluors can be
calculated with fair accuracy,3 fluorescence quantum
yields (Φf) are not predictable. Radiation stability is
related to photochemical stability and is hard to predict,
but elements of Z > 10 can be avoided, as well as any
functional group that is susceptible to free-radical reac-
tions. Brightness is the product of Φf and the molar
extinction coefficient (ꢀ).2 The desirable fast response
times, called short fluorescence decay times (τf), have
been inversely correlated with ꢀ for ultraviolet absorption
in oligophenylenes;4 however, the longest practical emis-
sion wavelength obtainable from an oligophenylene, 390
nm, is from a sexiphenyl with no auxofluors (auxo-
For decades the U.S. Department of Energy has
supported research on accelerators, with which detectors
of relativistic particles are essential. The components of
detectors made of polystyrene (PS) tiles contain dissolved
fluors that emit violet-to-blue light pulses (scintillations)
derived from the impact of high-energy particles and
photons. Because of the destruction of the light transmis-
sion of PS at shorter wavelengths by high flux levels of
particles, the present approach is to change the wave-
length of the light emitted to green for detection with
green-sensitive photomultiplier tubes because the PS
retains its light transmission at longer wavelengths. This
is accomplished by the use of bent circular fibers, into
which a fluor with appropriate wavelengths of absorption
and emission is incorporated, which are imbedded in the
tiles.1 The many requirements for such waveshifting
fluors have been detailed.2 Organic fluors are used
because their decay time is the fastest, and they can be
(1) Gaillard, J .-M. In Proceedings Workshop on Scintillating Fiber
Detectors, University of Notre Dame, Oct 24-28, 1993; Bross, A. D.,
Ruchti, R. C., Wayne, M. R., Eds.; World Scientific: Singapore, 1995;
p 16.
(2) Kauffman, J . M. Radiat. Phys. Chem. 1993, 41, 365.
(3) Fabian, W. M. F.; Kauffman, J . M. J . Lumin. 1999, 85, 137.
(4) Berlman, I. B. Handbook of Fluorescence Spectra of Aromatic
Molecules, 2nd ed.; Academic Press: New York, 1971; pp 71, 322, 324.
* To whom correspondence should be addressed. Phone and FAX:
(610) 293-0594.
10.1021/jo020333+ CCC: $25.00 © 2003 American Chemical Society
Published on Web 12/18/2002
J . Org. Chem. 2003, 68, 839-853
839

Kauffman and Moyna
TABLE 1. Op tica l P r op er ties of (E)-1,6-Dia r yl- a n d (E)-1,1,6,6-Tetr a r yl-1,3,5-h exa tr ien es in Tolu en e
a
b
From ref 4. Fluorescence emission, RI ) relative intensity. c Vs 9,10-diphenylanthracene at φf ) 0.82 from refs 5 and 50. d4-
Biphenylyl.
chromes on fluors).5 Carbon bridging of some of the rings
as in an oligofluorene extends this wavelength only to
about 437 nm.5 A recent report on fluors which are
agglomerations of benzoxazoles (or benzothiazoles) and
phenylene groups gave fast fluors, but their solubilities
and Stokes’ shifts were too low.6 Our attempt to use
benzofuran-terminated oligofurans failed because these
materials had too much self-absorption and were only
moderately stable.7 While the τf for 1,6-diphenyl-1,3,5-
hexatriene (12 ns) is much too slow,4 its wavelengths
were promising (Table 1); thus we thought that incorpo-
ration of auxofluors might bathochromically shift the
wavelengths into the range desired, which are absorption
at 410 ( 10 nm and fluorescence emission at 480 ( 20
nm (blue-green), the difference being called the Stokes’
shift, and that these might serve as model compounds.
With τf ) 1.1 ns a 1,4-distyrylbenzene (BPSB, Table 2)
also seemed to be a promising fluorophore, but with even
more bathochromic shift required. It is easier to obtain
the large Stokes’ shifts desired in a fluor with an electron-
releasing auxofluor at one end and an electron-accepting
auxofluor at the other (“push-pull auxofluors”); however,
fluors with symmetrical auxofluors tend to have higher
Φf and ꢀ, and thus shorter τf, but at the cost of less Stokes’
shift and poorer solubility.5
the common groups.8 The magnitude of the shift is
inversely proportional to the Hammett σ constant, this
being most pronounced for the 9-julolidinyl group (see
31g) with σ ) -1.7.9 The dialkylamino group is photo-
chemically unstable on oligophenylenes,10 but is stable
on coumarins11,12 and rhodamines13 which absorb and
emit at longer wavelengths. We now report our findings
on 2,5-diphenyloxazoles, 1,3,5-hexatrienes, and 1,4-
distyrylbenzenes, many bearing dialkylamino groups as
auxofluors. On finding that such fluors were unstable,
we switched to diarylamino groups based on a report on
a benzothiazole analogue of fluor 7;14 these groups gave
better overall photochemical stability on all three fluor
types, and this finding then was applied to novel 2,7-
distyrylfluorenes.
During the course of this work reports appeared on
other photophysical properties of fluors 31d 15,16 and
(8) Saito, R.; Hirano, T.; Niwa, H.; Ohashi, M. J . Chem. Soc., Perkin
Trans. 2 1997, 1711.
(9) Kauffman, J . M.; Imbesi, S. J . Org. Prep. Proc. Intl. 2001, 33,
603.
(10) Kauffman, J . M.; Kelley, C. J .; Ghiorghis, A.; Neister, S. E.;
Armstrong, L. Laser Chem. 1988, 8, 335.
(11) Fletcher, A. N.; Bliss, D. E.; Kauffman, J . M. Opt. Commun.
1983, 47, 57.
(12) J ones, G., II; J ackson, W. R.; Choi, C.; Bergmark, W. R. J . Phys.
Chem. 1985, 89, 294.
(13) Sauer, M.; Han, K.-T.; Mu¨ller, R.; Nord, S.; Schulz, A.; Seeger,
S.; Wolfrum, J .; Arden-J acob, J .; Deltau, G.; Marx, N. J .; Zander, C.;
Drexhage, K.-H. J . Fluoresc. 1995, 5, 247.
The dialkylamino group as an electron-releasing aux-
ofluor provides the most extreme bathochromic shift of
(5) Kauffman, J . M.; Litak, P. T.; Novinski, J . A.; Kelley, C. J .;
Ghiorghis A.; Qin, Y. J . Fluoresc. 1995, 5, 295.
(6) So, Y.-H.; Zaleski, J . M.; Murlick, C.; Ellaboudy, A. Macromol-
ecules 1996, 29, 2783.
(14) Belfield, K. D.; Schafer, K. J .; Mourad, W.; Reinhardt, B. A. J .
Org. Chem. 2000, 65, 4475.
(15) Kretsch, K. P.; Belton, C.; Lipson, S.; Blau, W. J .; Henari, F.
Z.; Rost, H.; Pfeiffer, S.; Teuschel, A.; Tillmann, H.; Ho¨rhold, H.-H. J .
Appl. Phys. 1999, 86, 6155.
(7) Kauffman, J . M.; Moyna, G. J . Heterocycl. Chem. 2002, 39, 981.
840 J . Org. Chem., Vol. 68, No. 3, 2003

Diarylamino Groups as Photostable Auxofluors
TABLE 2. Op tica l P r op er ties of (E)-1,4-Distyr yl- a n d (E)-1,4-Bis(2-p h en ylstyr yl)ben zen es in Tolu en e
a
b
d
From ref 4. Fluorescence emission, RI ) relative intensity. c Vs 9,10-diphenylanthracene at φf ) 0.82 from refs 5 and 50. Relative
photochemical stability, see text. e 4-Methoxyphenyl. f Lit. 0.85 from ref 15.
31f16,17 or their homologues , which are of interest as laser
dyes, two-photon absorbers, components of electrolumi-
nescent flat panel displays, and light-emitting diodes.
Now there is keen interest in scintillation detection of γ
rays and neutrons for homeland security using PS
scintillators with dissolved fluors and waveshifters.
Known and reliable synthetic methods were deliber-
ately selected; nevetheless, we were able to simplify some
reported procedures for Buchwald-type N-arylations, and
to improve the Emmons-Horner reaction.
Discu ssion a n d Resu lts of Syn th eses
For fluor 7 (Scheme 1) the reported nitration of
fluorene 118 was improved to give nitrofluorene 2, in
which the iodo group was then replaced with cyano in
91% yield to give 3. Basic hydrolysis failed, but acid
hydrolysis utilizing propanoic acid as a cosolvent gave
(16) Rumi, M.; Ehrlich, J . E.; Heikal, A. A.; Perry, J . W.; Bar-
low, S.; Hu, Z.; McCord-Maughon, D.; Parker, T. C.; Ro¨ckel, H.;
Thayumanavan, S.; Marder, S. R.; Beljonne, D.; Bre´das, J .-L. J . Am.
Chem. Soc. 2000, 122, 9500.
(18) Kelley, C. J .; Ghiorghis A.; Kauffman, J . M. J . Chem. Res. (S)
1997, 446; J . Chem. Res. (M) 1997, 2701.
(17) Ip, J .; Rendu, P. L.; Tran, V. H. Synth. Met. 2001, 122, 45.
J . Org. Chem, Vol. 68, No. 3, 2003 841

Kauffman and Moyna
SCHEME 1. Syn th esis of 2-(6-Meth yl-2-ben zoxa zolyl)-7-[bis(4-m eth oxyp h en yl)a m in o]-9,9-d ip r op ylflu or en e
acid 4 in excellent yield. Formation of oxazole 5 in a 1-pot
reaction gave much lower yields than we obtained when
the intermediate amide was isolated in syntheses of
related fluors;19 we avoided the use of polyphosphoric acid
for this condensation because of the extreme insolubility
of 4 in it. Reduction of the nitro group in 5 by means of
iron in acetic acid gave 89% of aminofluorene 6. Diary-
lation to form 7 was carried out according to Belfield14
using triglyme as solvent rather than 1,2-dichloroben-
zene.
For fluor 14 (Scheme 2) we worked out a convenient
di-N-ethylation of 4′-aminoacetophenone 8 with diethyl
sulfate in dioxane with use of diisopropylethylamine as
the acid acceptor. The formation of the ammonium salt
of 9 allowed regiospecific bromination to give the phen-
acyl bromide 10, isolated as an oily free base. A Gabriel
synthesis was preferable to the De´le`pine reaction because
the diammonium salt 13 has the same solubility as
ammonium bromide, whose presence was avoided, while
the phthalic acid byproduct was easily removed from 13
with acetone. A 1-pot oxazole formation (not optimized)
gave 14.
methoxyphenyl)amine 1920 was prepared by Buchwald
conditions in which expensive resolved BINAP (the
racemic not being available at the time) was advanta-
geously replaced by dppf,21 and the workup was simpli-
fied. A second buchwald Reaction, this time between 18
and 19, gave 20 in good yield.
A simple Vilsmeier reaction on triphenylamine had
been reported to give the aldehyde 23d (Scheme 4) in
unreported yield after a difficult fractional crystalliza-
tion;22 we worked out a method to yield 85% after a single
recrystallization from ethanol, obviating the need for the
multistep method of Tew et al.21 A Buchwald amination
of 4-bromobenzonitrile with 19 gave triarylamine 27 in
good yield (Scheme 5). This was converted to the aldehyde
23e in the manner of Tew et al.21 with some modification
of conditions.
The known phosphonate esters 22 (Scheme 4) and 30
(Scheme 5) were prepared by either improved or simpli-
fied methods. The bis(chloromethyl)fluorene 38 (Scheme
6) had been reported by chloromethylation of 9,9-dipro-
pylfluorene;18 knowing how tedious this had been, we
took advantage of the availability of a number of fluorene
derivatives to develop an alternate route. First the
dicarboxylic acid 33 was esterified to form 34, but the
reduction with sodium bis(2-methoxyethoxy)aluminum
hydride in toluene, while destroying all carbonyl groups,
For fluor 20 (Scheme 3), oxazole 18 was an obvious
intermediate target, since the cyano group is compatible
with Buchwald conditions, so 2,4′-dibromoacetophenone
15 was converted via the De´le`pine reaction to the
phenacylammonium salt 16, which was amenable to
recrystallization from water, thus giving a complete
separation from ammonium bromide in this case; then a
1-pot oxazole formation gave 18. The known bis(4-
(20) Michinobu, T.; Tsuchida, E.; Nishide, H. Bull. Chem. Soc. J pn.
2000, 73, 1021.
(21) Tew, G. N.; Pralle, M. U.; Stupp, S. I. Angew. Chem., Int. Ed.
2000, 39, 517.
(22) Baker, T. N., III; Doherty, W. P., J r.; Kelley, W. S.; Newmeyer,
W.; Rogers, J . E., J r.; Spalding, R. E.; Walter, R. I. J . Org. Chem. 1965,
30, 3714.
(19) Hall, J . H.; Chien, J . Y.; Kauffman, J . M.; Litak P. T.; Adams,
J . K.; Henry, R. A.; Hollins, R. A. J . Heterocycl. Chem. 1992, 29, 1245.
842 J . Org. Chem., Vol. 68, No. 3, 2003

Diarylamino Groups as Photostable Auxofluors
SCHEME 2. Syn th esis of 2-(4-Cya n op h en yl)-5-
[4-(d ieth yla m in o)p h en yl]oxa zole
SCHEME 3. Syn th esis of 2-(4-Cya n op h en yl)-5-
{4-[bis(4-m eth oxyp h en yl)a m in o]p h en yl}oxa zole
typically 50-70%. We found that DMF will dissolve
potassium tert-butoxide at 7 mL/g, and that the solution
may be added to the diphosphonate and carbonyl com-
pound in a controlled manner so that the transitory
formation of the red carbanion may be observed. This
“indicator” showed that up to almost a 2-fold excess of
potassium tert-butoxide increased yields of crude alkenes
to 80-100% in several cases when benzaldehydes were
used, but such yields were not obtained when benzophe-
nones were used. Procedures for a number of alkenes
previously reported in the nonpatent literature are
included when our method of synthesis was different, or
no optical spectra were found, or where no NMR or no
high-field NMR data were found.
did not give a purifiable diol (35). The di-Grignard
reagent of 2,7-dibromo-9,9-dipropylfluorene 36 gave liq-
uid dialdehyde 37, whose reduction with sodium bis(2-
methoxyethoxy)aluminum hydride then gave clean diol
35. An easy 3-phase reaction with 12 M hydrochloric acid
and toluene gave 38, which was converted to crystalline
phosphonate ester 39 by an Arbuzov reaction.
The 1,3,5-hexatrienes 24a -d (Scheme 4), the 1,4-
distyrylbenzenes 31d -g and 32a -e (Scheme 5), and the
2,7-distyrylfluorenes 40a ,d ,e (Scheme 6) were all pre-
pared by a version of the Emmons-Horner reaction that
favors all (E) alkenes (except for 26a -c and 32a -e); this
involves the use of DMF as solvent and, in our version,
potassium tert-butoxide as the base. Many permutations
of reagent addition have been reported. With these, when
sodium methoxide is the base, yields of crude alkenes are
Discu ssion
P r op er ties
a n d
Resu lts
of
P h otop h ysica l
Belfield et al. had not given the absorption and
fluorescence maxima in toluene, which is of similar
J . Org. Chem, Vol. 68, No. 3, 2003 843

Kauffman and Moyna
SCHEME 4. Syn th eses of 1,6-Dia r yl- a n d 1,1,6,6-Tetr a a r yl-1,3,5-h exa tr ien es
polarity to PS, for a benzothiazole analogue of fluor 7;
they used THF as the solvent, which bathochromically
shifts the wavelengths of such solvatochromic fluors
bearing push-pull auxofluors. Also the Φf, ꢀ, and τf
values were not given.14 We found that the absorption
max of 7 at 401 nm (ꢀ ) 48 700) and the Φf ) 0.86 were
acceptable; but its emission max at 455 nm was too short
for our purposes (all determined in toluene), and the τf
) 4.55 ns was too slow in PS.
Earlier work on 2,5-diphenyloxazoles, including some
with dialkylamino groups, showed that they were ef-
ficient fluors with large Stokes’ shifts.23 Cyano group(s)
on terphenyl gave improved scintillation fluors,24 so we
decided to combine these two types of groups as push-
pull auxofluors as in fluor 14. The 80-nm Stokes’ shift
was excellent (Figure 1), along with a good Φf of 0.69;
but the absorption max was too short at 394 nm, and
the low ꢀ of 27 000 would have led to a slow τf.2
Determination of the radiation damage to fluors in PS
using γ rays is a slow and involved process, which will
be reported separately for 7, 31d ,e, and 40d ,e. We were
able to glean the relative photochemical stabilities (RPS)
of fluors by exposing 1-3 × 10-5 M solutions of them in
toluene to diffuse daylight and fluorescent light on a
diurnal basis, and noting the time for the fluorescence
to fade. Fluor 14 faded noticeably in 2 weeks and
completely in 5 weeks, a poor performance.
So the diaryl analogue 20 made use of 4-methoxyphe-
nyl instead of ethyl groups and 20 showed a 103-nm
Stokes shift, from 402 nm (ꢀ ) 29 100) to 505 nm with
Φf of 0.63, and did not fade for at least 5 weeks. The low
ꢀ would indicate low brightness as well as a slow τf;2 the
former is obvious to the naked eye vs the distyrylbenzene
31e, for example, which had ꢀ ) 72 000 and about the
same Φf 0.74.
In the 1,6-diaryl-1,3,5-hexatrienes (Table 1) extension
of conjugation by substitution of phenyl (24a ) by 4-bi-
phenylyl (24b) gave higher ꢀ but not much bathochromic
shift. The 2-phenylfluorenyl group (24c) gave still higher
ꢀ and about 33 nm of bathochromic shift, but the effective
Stokes’ shift (444 to 460 nm) was inadequate. The
diphenylamino group (24d ) displayed a larger Stokes’
shift (445 to 470 nm), had high ꢀ, and was as stable as
24b, each with an RPS of 5 months. The loss of fluores-
cence was probably governed by the rate of E/Z isomer-
ization.25 The 1,1,6,6-tetraaryl-1,3,5-hexatrienes 26a ,b
had lower ꢀ but high Φf, 0.69 for 26b; thus 26b is being
further tested for our purposes, partially because of its
ideal wavelengths (Figure 2). The fluorenylidenebutene
26c had high ꢀ, but Φf ) 0.
(23) Ott, D. G.; Hayes, F. N.; Hansbury, E.; Kerr, V. N. J . Am. Chem.
Soc. 1957, 79, 5448.
(24) Vela´zquez, C.; Castrillo´n, J . Intl. J . Appl. Radiat. Isotopes 1974,
26, 237.
(25) Magoon, E. F.; Zechmeister, L. J . Am. Chem. Soc. 1955, 77,
5642.
844 J . Org. Chem., Vol. 68, No. 3, 2003

Diarylamino Groups as Photostable Auxofluors
SCHEME 5. Syn th eses of 1,4-Distyr ylben zen es
The excellent properties of 1,4-distyrylbenzene “BPSB”
(Table 2), which included a τf of 1.1 ns,4 inspired our
extensive efforts to bathochromically shift its wave-
lengths by about 70 nm. The earliest derivatives we
prepared were the dialkylaminos 31f,g, whose photo-
physical properties we had reported;26 these displayed
both high ꢀ and Φf, but 31f had a very poor RPS of 0.1
month, so based on the findings for coumarins used as
laser dyes,27,28 we thought that the julolidinyl analogue
31g would be more stable; instead it had the poorest RPS
of any fluor made in this project, ≈ 0.01 month. Next the
2,2-diarylethenyl derivatives 32a -e were prepared, but
these also showed low ꢀ, apparently because of steric
hindrance to coplanarity in the S1 state; moreover all had
Φf ) 0. Finally the diarylamino fluors 31d ,e were
synthesized and found to have high Φf, high ꢀ, and an
(26) Kauffman, J . M.; Bajwa, G. S.; Litak, P. T. In SCIFI 97:
Conference on Scintillating Fiber Detectors, University of Notre Dame,
Nov 97; Bross, A. D., Ruchti, R. C., Wayne, M. R. Eds.; American
Institute of Physics Conf. Proc. 450, Woodbury, NY, 1998; p 3.
(27) Fletcher, A. N.; Bliss, D. E.; Kauffman, J . M. Opt. Commun.
1983, 47, 57.
(28) J ones, G., II; J ackson, W. R.; Choi, C.; Bergmark, W. R. J . Phys.
Chem. 1985, 89, 294.
J . Org. Chem, Vol. 68, No. 3, 2003 845

Kauffman and Moyna
SCHEME 6. Syn th eses of 2,7-Distyr ylflu or en es
RPS ) 7 months; these proved to have the best combina-
tion of properties for our purposes (see Figures 3 and 4),
including τf ) 1.86 (31d ) and 2.25 ns (31e).
varied from excellent to fair and Φf was not predictable.
For example, the predicted absorption maximum for 24c
was 382 nm vs actual triple maxima of 397, 419, and 444
nm, while the predicted emission maxima were 461, 488,
and 521 nm vs actual maxima of 460 and 488 nm. The
calculated absorption maximum for 26c was 392 nm vs
actual maxima of 415, 442, and 472 nm; while the
predicted emission max was 465 nm vs no emission.
According to Walter M. F. Fabian, these calculations fail
altogether when amino groups are present, and so they
had not been done for any of the amino compounds.
As a model compound the fluorene 40a 18 (Table 3)
proved to have a smaller Stokes’ shift and very little
bathochromic shift compared with BPSB, but the increase
in ꢀ was substantial and indicated likely benefits in
brightness and τf. Accordingly, fluors 40d ,e were syn-
thesized (Figures 5 and 6), which display τf ) 1.73 (40d )
and τf ) 2.05 ns (40e), the fastest green-emitting fluors
of which we are aware, but not as photostable as the
corresponding distyrylbenzenes (RPS ) 6 and 4.5 months
respectively).
Con clu sion s
Wavelengths of absorption and fluorescence had been
The Buchwald and Emmons-Horner reactions were
further developed for syntheses of di- and triarylamines
calculated for 24a -c, 26a -c, and 32a ;3 the accuracy
846 J . Org. Chem., Vol. 68, No. 3, 2003

Diarylamino Groups as Photostable Auxofluors
TABLE 3. Op tica l P r op er ties of (E)-2,7-Distyr ylflu or en es in Tolu en e
a
b
Fluorescence emission, RI ) relative intensity. Vs 9,10-diphenylanthracene at φf ) 0.82 from refs 5 and 50. c Relative photochemical
d
stability, see text. 4-Methoxyphenyl.
F IGURE 1. UV-vis and emission spectra of 5-(4-diethylami-
nophenyl)-2-(4-cyanophenyl)oxazole (14).
F IGURE 3. UV-vis and emission spectra of 1,4-bis[4′-
(diphenylamino)styryl]benzene (31d ).
F IGURE 2. UV-vis and emission spectra of 1,1,6,6-tetra-4-
biphenylyl-1,3,5-hexatriene (26b).
F IGURE 4. UV-vis and emission spectra of 1,4-bis[4′-bis(4-
methoxyphenyl)aminostyryl]benzene (31e).
and alkenes, respectively. The former is clearly superior
to Ullmann N-amination even with use of a phase-
transfer catalyst. The latter was improved by a novel
order of reagent addition and the use of excess base. A
2-benzoxazolyl-7-(4-diphenylamino)phenylfluorene (7) was
bright, but had an emission wavelength too short for this
project, and was too slow. Fluors bearing diarylamino
groups were more photochemically stable than those with
dialkylamino groups: compare 2-(cyanophenyl)-5-(4-ami-
nophenyl)oxazoles 14 and 20. This was true also in 1,4-
bis(4′-aminostyryl)benzenes: compare 31d ,e with 31f,g.
The 1,6-diaryl-1,3,5-hexatrienes 24a -d showed higher
ꢀ and Φf than the 1,1,6,6-tetraaryl-1,3,5-hexatrienes
26a-c. The 1,4-distyrylbenzenes 31d-g similarly showed
higher ꢀ and Φf than the 1,4-(2-phenylstyryl)benzenes
32a -e. The 2,7-distyrylfluorenes 40a ,d ,e had higher ꢀ
and Φf than the 1,4-distyrylbenzenes 31d -g and were
in fact visibly brighter and slightly faster. Thus several
new compounds were prepared that were promising as
waveshifting fluors for PS fibers, which would serve as
a key component of scintillation detectors of high-energy
particles from accelerators.
Exp er im en ta l Section
Gen er a l Meth od s. General procedures have been previ-
ously described.29 Air-sensitive reactions were conducted under
argon. Dibutyl Carbitol (DBC) was diethylene glycol dibutyl
ether, Aldrich 20,562-1. The potassium tert-butoxide (KOtBu)
J . Org. Chem, Vol. 68, No. 3, 2003 847

Kauffman and Moyna
received is averaged over the number of laser firings for each
clock delay, and these means are recorded to a text file of delay
times and intensities; then these files are transferred to
another computer for analysis with MS Excel, by which the
log of the intensity is plotted against the delay time, in which
2 linear portions of each curve are normally found. The τf is
the reciprocal of the slope of the first linear portion of each
curve.
Syn th esis of 9,9-Dip r op yl-2-iod o-7-n itr oflu or en e (2). A
mixture of 9,9-dipropyl-2-iodofluorene18 (1, 37.6 g, 0.1 mol),
300 mL of acetic acid, and 20 mL of 90% nitric acid was heated
slowly to reflux, which was maintained for 4 h. The mixture
turned dark, then light, and was allowed to cool to 20 °C before
being quenched in 1.2 L of water with propeller stirring. The
crude product was collected, washed with 700 mL of water and
a minimum of 50% methanol, dried at 60 °C/20 Torr/3 h to
give 45.4 g of crude 2. This was recrystallized from 300 mL of
2-propanol at -2 °C, decanted, and the damp solid recrystal-
lized from 250 mL of hexane at -2 °C to give huge yellow
prisms, mp 117-120 °C, 27.2 g (64%) (lit.18 46%, mp 121-122
°C).
F IGURE 5. UV-vis and emission spectra of 1,4-bis[4′-bis-
(diphenylamino)styryl]-9,9-dipropylfluorene (40d ).
Syn th esis of 2-Cya n o-9,9-d ip r op yl-7-n itr oflu or en e (3).
A suspension of 9,9-dipropyl-2-iodo-7-nitrofluorene (2, 50.0 g,
0.119 mol), copper(I) cyanide (12.75 g, 0.142 mol), and 85 mL
DMF was boiled under reflux overnight and allowed to cool to
about 50 °C, then poured into a solution of potassium cyanide
(29.4 g, 2.21 mol) in 210 mL of water with propeller stirring.
During the course of an hour the gummy solid turned hard
and was collected, washed with 100 mL of water, ground in a
mortar, slurried with 300 mL of 47.5% ethanol, re-filtered,
washed on the filter with 300 mL of 47.5% ethanol, and then
dried at 80 °C/25 Torr/2 h to give 42.3 g. This was extracted
from a glass thimble in a large Soxhlet with 600 mL of
cyclohexane and the extract was transferred to a beaker,
diluted with 250 mL of hexane, and allowed to stand at 20 °C
overnight to yield nice tan spars, mp 161-161.5 °C, 36.7 g
(97%). Anal. Calcd for C20H20N2O2: C, 74.98; H, 6.29; N, 8.75.
F IGURE 6. UV-vis and emission spectra of 1,4-bis[4′-bis(4-
methoxyphenyl)aminostyryl]-9,9-dipropylfluorene (40e).
was from Callery Chemical Co. Division of MSA, Inc. Solvents
used in moisture-sensitive reactions were dried over 3A
Molecular Sieve. All other solvents and reagents not given
citations were used as received from common commercial
sources; uncommon sources are named. Preparation of the
catalyst palladium(II) chloride 1,4-bis(diphenylphosphino)-
butane (PdCl2‚dppb) has been described.30 Florisil was Aldrich
22,074-4. Next to mp, pc means phase-change. Elemental
Assays were performed by Micro-Analysis, Inc., of Wilmington,
DE. For AA′XX′ spin systems (i.e., 4-substituted phenyl rings)
1
Found: C, 74.70; H, 6.30; N, 8.69. H NMR (90 MHz, CDCl3)
δ 0.69 (10H, m), 2.07 (4H, m), 7.80 (4H, m), 8.29 (1H, s), 8.33
(1H, dd, J ) 2.2, J ) 8.2).
Syn th esis of 9,9-Dip r op yl-7-n itr oflu or en e-2-ca r boxylic
Acid (4). A mixture of 2-cyano-9,9-dipropyl-7-nitrofluorene (3,
36.7 g, 0.115 mol) and 73.4 mL each of acetic acid, water, and
sulfuric acid was boiled under reflux for 2 days, allowed to
cool below 100 °C, and diluted with 425 mL of water; this
mixture was cooled in a water bath to 20 °C, and the product
was collected, washed with 700 mL of water, and air-dried for
1
3
in H NMR spectra, only the J HH coupling is reported. All UV
and fluorescence emission spectra were determined on 1-3 ×
10-5 M solutions in toluene. Corrected emission wavelengths
were found with a Farrand Mk. I spectrofluorimeter rebuilt
by Optical Technology Devices, Inc., or a Varian Cary Eclipse;
the latter was used to measure the Φf values on the solutions
used for UV spectra as described previously, using 9,10-
diphenylanthracene (Polysciences, Inc.) in toluene as a refer-
ence with Φf ) 0.82.5 The fluorescence decay times (τf) were
determined by means of front-face laser excitation of a solution
of the sample where the reciprocal of the log of emission
intensity vs time of the first linear section of the curve is used.
A Photon Technology International (PTI) GL-3300 Nitrogen
Laser with a tunable PTI photometer was interfaced with a
Windows NT PC operating the PTI TimeMaster Fluorescence
Lifetime software. The laser is fired into the face of the sample
and the photometer records the intensity emitted at right
angles to the laser beam at the wavelength determined
separately on a Hitachi spectrofluorimeter. The photometer
is stepped though a selected timing range and the intensity is
recorded. The laser is fired 5 to 10 times at each time delay
from the clock start, usually in steps of 0.1-0.3 ns. The light
2 days to give 36.6 g (94%), mp 255-265 °C. IR (CHCl3, cm-1
)
3400-2800 (v br, OH), 3015 (ArCH), 2980, 2930, 2872 (alCH),
1685 (CdO), 1518, 1348 (NO2), 1220, 1200 (CsO), 640 (ArCH).
The product of another earlier run, after recrystallization
of 0.4 g from 10 mL of 2-methoxyethanol with 4 mL of water,
gave pale yellow transparent spars, mp s. 245, 256-265 °C.
Anal. Calcd for C20H21NO4: C, 70.78; H, 6.24; N, 4.13. Found:
C, 70.90; H, 6.20; N, 4.40.
Syn th esis of 9,9-Dip r op yl-2-(6-m eth yl-2-ben zoxa zolyl)-
7-n itr oflu or en e (5). A mixture of 9,9-dipropyl-7-nitrofluorene-
2-carboxylic acid (4, 6.20 g, 0.0813 mol), 6-amino-m-cresol (2.25
g, 0.0813 mol), boric acid (1.13 g, 0.0813 mol), and 110 mL of
diglyme was boiled under reflux so as to extract 20 g of
indicating 4A Mol Sieve in a small Soxhlet for 20 h. At 20 °C
the mixture was poured into 300 mL of water and 50 mL of
95% ethanol. A tarry material separated. This was extracted
with 100 mL, then 50 mL of chloroform; the extracts were
washed with 300 mL of water and dried with 20 g of calcium
chloride for 1 h. The supernatant was poured through a 4 ×
10 cm column of neutral alumina (Aldrich 19,997-4) followed
by 350 mL of chloroform. The eluate was evaporated to deposit
2.5 g of orange oil which crystallized well from 12.5 mL of abs
ethanol. The orange prisms were collected, washed with
methanol, and air-dried to give 1.49 g (19%), mp 175-177 °C.
(29) Kauffman, J . M.; Khalaj, A.; Litak, P. T.; Bajwa, G. S.; Novinski,
J . A. J . Heterocycl. Chem. 1994, 31, 957.
(30) Kelley, C. J .; Ansu, K.; Budisusetyo, W.; Ghiorghis A.; Qin, Y.;
Kauffman, J . M. J . Heterocycl. Chem. 2001, 38, 11.
848 J . Org. Chem., Vol. 68, No. 3, 2003

Diarylamino Groups as Photostable Auxofluors
Anal. Calcd for C27H26N2O3: C, 76.03; H, 6.14; N, 6.57.
Found: C, 75.77; H, 5.90; N, 6.53.
This was taken up in 215 mL of dry DMF, treated with
potassium phthalimide (46.9 g, 0.253 mol), and held at 75 °C/
18 h. The suspension was quenched in 900 mL of water with
mechanical stirring, which was maintained for 40 min, and
the product was collected, washed with 500 mL of water, then
50 mL of 50% methanol, and dried 100 °C/30 Torr/1 h to give
70.5 g of crude brown pellets, which were recrystallized from
500 mL of acetonitrile at 0 °C overnite to give huge yellow
spars, mp 175-177.5 °C pc, 183-184 °C, 49.5 g (64%). Tlc on
Whatman MK6F Silica Gel, ethyl acetate, UV, gave a single
spot, Rf 0.72, 11.
Syn th esis of 7-[Bis(4-m eth oxyph en yl)am in o]-9,9-dipr o-
p yl-2-(6-m eth yl-2-ben zoxa zolyl)flu or en e (7). A suspension
of 9,9-dipropyl-2-(6-methyl-2-benzoxazolyl)-7-nitrofluorene (5,
1.41 g, 0.00331 mol), 1.9 g of iron powder (Lancaster 13237),
and 40 mL of acetic acid was heated to boiling. The heat was
turned off, and when boiling ceased, 0.39 g of iron (0.0231 mol
in all) was added. This mixture was boiled under reflux for 10
min, then was allowed to cool. The supernatant was decanted
into 80 mL of water, this mixture was stirred 1 h, and the
7-a m in o-9,9-d ip r op yl-2-(6-m et h yl-2-b en zoxa zolyl)flu o-
r en e (6) was collected, washed with 50 mL of 50% methanol,
and dried at 110 °C/20 Torr/1 h to give 3.23 g, mp s. 192, 230-
251 °C. This product was recrystallized from a mixture of 30
mL of 2-methoxyethanol and 10 mL of water to give 1.17 g
(89% crude), mp pc 203 °C, pc 236-246, 247-253 °C. The
product displayed a bright blue fluorescence under longwave
UV in toluene.
The product of an earlier run was recrystallized from 20
mL/g of 1:1 methanol:dibutyl ether. Anal. Calcd for C30H20
-
N2O3: C, 71.43; H, 5.95; N, 8.33. Found by Micro-Analysis:
C, 70.41; H, 5.70; N, 8.24. 1H NMR (90 MHz, CDCl3) δ 1.22
(6H, t, J ) 7.0), 3.45 (4H, q, 7.0), 5.06 (2H, s), 6.66 (2H, AA′XX′,
J ) 9.5), 7.91 (2H, AA′XX”, 9.5).
Syn t h esis of 4′-(Diet h yla m in o)p h en a cyla m m on iu m
Br om id e Hyd r obr om id e Hem ih yd r a te (13). The phthal-
imide (11, 16.0 g, 0.476 mol) and potassium hydroxide (3.3 g
of 85%, 2.80 g, 0.501 mol) in 135 mL of water and 30 mL of
1-propanol were boiled under reflux for 19 h, cooled in a water
bath to 20 °C, and made up to pH 4.6 with 6 M hydrochloric
acid. The liquid was decanted and the residual gum was
crystallized from 75 mL of 95% ethanol, diluting with 75 mL
of water, and keeping at 0 °C to give crystals, after drying
them at 100 °C/20 Torr/1 h, of N-[4′-(d ieth yla m in o)p h en -
a cyl]p h th a la m ic a cid (12), 11.75 g (73%), mp 144-145 °C
dec (loss of water).
This crude amine (6, 1.17 g, 0.00295 mol), 4-iodoanisole (3.00
g, 0.0118 mol), potassium carbonate (3.26 g, 0.0236 mol),
copper powder (1.0 g), 18-crown-6 (0.26 g), and 13 mL of
triglyme was heated to 192 °C for 29 h by controlling the
heating with
a Therm-O-Watch relay. The mixture was
allowed to cool to ≈60 °C and poured into 60 mL of methanol,
and the flask was rinsed with 10 mL of methanol, producing
a nice granular solid, which was collected, washed with 50%
methanol, and air-dried overnight to give 2.2 g with a second
crop of 0.26 g. Combined, these were extracted from a small
Soxhlet with 125 mL of heptane in 90 min, and the extract
kept at -20 °C overnight to give material, after decantation
and drying, of mp 149-151 °C. This product was recrystallized
from 10 mL of 1-propanol at -2 °C overnight, then from a
mixture of 20 mL each of abs ethanol and acetonitrile with 15
mL of heptane, decanting from some insoluble yellow stuff
before cooling to -20 °C overnight, to yield 0.59 g (33%) of 7,
mp 196.5-198.5 °C. Anal. Calcd for C41H40N2O3: C, 80.89; H,
This and 158 mL of 40% hydrobromic acid were boiled under
reflux overnight. The temperature was 120 °C at reflux to start
and 118 °C at the end. The mixture was cooled in ice to 10 °C,
the phthalic acid filtered off, and the filtrate evaporated at 5
Torr and 80 °C bath temp. To the solid residue was added 90
mL of abs ethanol with evaporation at 20 Torr, then 50 mL of
toluene was added with evaporation at 20 Torr, then the mush
was taken up in 60 mL of 2-propanol and diluted with 100
mL of ether. The product was collected and dried at 60 °C/20
Torr/18 h to get a crispy tan solid (13), mp 168-182 °C dec.
The product of an earlier run, purified by washing with
2-propanol, mp 177-180 °C dec, was assayed. Anal. Calcd for
1
6.62; N, 4.60. Found: C, 81.14; H, 6.57; N, 4.50. H NMR (90
MHz, CDCl3) δ 0.70 (10H, m), 1.86 (2H, m), 2.51 (3H, s), 3.82
(6H, s), 7.01 (12H, m), 7.54 (3H, m), 8.18 (2H, m). τf ) 4.55 ns.
Syn th esis of 4′-(Dieth yla m in o)a cetop h en on e (9). A
mixture of 4′-aminoacetophenone (8, 96.0 g, 0.710 mol), diethyl
sulfate (204 mL, 241 g, 1.562 mol), diisopropylethylamine (273
mL, 202 g, 1.562 mol), and 700 mL of dioxane was boiled under
reflux for 4 days, cooled to 20 °C in a water bath, and quenched
in 700 mL each ice and water; the crude was collected, washed
with 100 mL of water, then 100 mL of cold 25% methanol,
and the tarry solid was taken up in 300 mL of dichlo-
romethane; the solution was dried with 25 g of sodium sulfate
and evaporated in a tared 500 mL Bu¨chi flask to give 72 g of
dark brown oil, which was distilled under vacuum using a
spray trap. A single cut, bp 159-172 °C/0.25 Torr was taken
to yield 58 g (43%), which solidified on keeping, mp 41.5-44.5
°C (lit.31 mp 47-48 °C).
The product of an earlier run, mp 42-43.5 °C, was recrys-
tallized from 32 mL of methanol and 10 mL of water at -20
°C to give material of mp 43-44.5 °C. 1H NMR (60 MHz,
CDCl3) δ 1.20 (6H, t, J ) 8.0), 2.48 (3H, s), 3.45 (4H, q, J )
8.0), 6.65 (2H, AA′XX′, J ) 9.0), 7.90 (2H, AA′XX′, J ) 9.0).
Syn th esis of N-[4′-(Dieth yla m in o)p h en a cyl]p h th a lim -
id e (11). The 4′-(diethylamino)acetophenone (9, 43.9 g, 0.230
mol) was dissolved in 90 mL of 40% (yes, forty) hydrobromic
acid and treated with a solution of bromine (11.8 mL, 36.8 g,
0.230 mol) in 56 mL of 40% hydrobromic acid over about 40
min, and the mixture was kept overnight at 20 °C, diluted with
225 mL of water, and neutralized with a slight excess of solid
sodium bicarbonate, then extracted with 330 mL of chloroform.
The extract was dried over sodium sulfate and evaporated with
a bath temperature e20 °C to yield 83.5 g of crude 4′-
(diethylamino)phenacyl bromide 10.
C
12H20N2O‚1/2H2O: C, 38.22; H, 5.61; N, 7.43. Found: C, 37.99;
H, 5.30; N, 7.60.
Syn th esis of 5-(4-Dieth yla m in op h en yl)-2-(4-cya n op h e-
n yl)oxa zole (14). A mixture of 4′-(diethylamino)phenacylam-
monium bromide hydrobromide hemihydrate (13, 0.94 g,
0.0025 mol), 4-cyanobenzoic acid (0.37 g, 0.0025 mol), and 10
mL of phosphorus oxychloride was boiled under reflux for 16
h, allowed to cool to 60 °C, then quenched in 100 g of ice. Then
sodium carbonate monohydrate were added to obtain pH 6.2,
and the lot was filtered; the solid was washed with water, 50%
methanol, then a little methanol, and air-dried overnight to
give 0.60 g of crispy brown solid, which was then extracted
from 5 cm of Merck Silica Gel 60 in a small Ace-Kau with a
mixture of 30 mL of heptane and 10 mL of benzene; the extract
was kept at -20 °C. The benzene froze, so after a slight
warmup to melt it, the yellow solid was filtered as above,
washed with heptane, and dried to give 0.185 g (25%), mp
148-150 °C. IR (CHCl3, cm-1) 2970 & 2930 & 2900 & 2867
1
(alCH), 2230 (cyano), 1603 (CdN, CdC). H NMR (400 MHz,
CDCl3) δ 1.23 (6H, t, J ) 7.0), 3.43 (4H, q, J ) 7.0), 6.73 (2H,
d, J ) 8.7), 7.29 (1H, s), 7.58 (2H, d, J ) 8.7), 7.76 (2H, d, J )
8.2), 8.17 (2H, d, J ) 8.2). 13C NMR (100 MHz, CDCl3) δ 13.2,
44.8, 111.7, 113.1, 114.7, 119.0, 121.1, 126.2, 131.9, 132.7,
148.6, 154.1, 158.1. Fl Em: λmax ) 476 nm, Φf ) 0.69.
Further extraction of the column gave 41 mg which was
recrystallized from 1 mL of abs ethanol to give nice yellow
blades, mp 150-151 °C. Anal. Calcd for C20H19N3O: C, 75.68;
H, 6.03; N, 13.24. Found: C, 74.85; H, 6.13; N, 13.01.
Syn th esis of 4′-Br om op h en a cyla m m on iu m Br om id e
Dih yd r a te (16). Hexamethylene tetramine (49.2 g, 0.350 mol)
was dissolved in 750 mL of chloroform, then 2,4′-dibromo-
(31) Nineham, A. W. J . Chem. Soc. 1952, 635.
J . Org. Chem, Vol. 68, No. 3, 2003 849

Kauffman and Moyna
acetophenone (97.4 g, 0.350 mol) was added all at once; the
suspension was stirred overnight and the quaternary salt was
collected, washed with 750 mL of chloroform, and dried at 60
°C/20 Torr/4 h. The product was treated with 900 mL of
methanol and 120 mL of 48% hydrobromic acid at 20 °C for 2
days; solid was always present, so 600 mL of methanol was
added, and the suspension was heated at 50 °C overnight and
then at reflux for 1.5 h, cooled to 20 °C, and evaporated at a
bath temperature of 50 °C to obtain a mushy solid, which was
recrystallized from 700 mL of water to give 16, 84.4 g (73%),
mp 273-27 7C° dec (lit.19 mp 260 °C dec).
Syn th esis of 5-(4-Br om op h en yl)-2-(4-cya n op h en yl)ox-
a zole (18). A mixture of 4′-bromophenacylammonium bromide
dihydrate (16, 4.45 g, 0.0134 mol), 4-cyanobenzoyl chloride
(2.27 g, 0.0134 mol), pyridine (1.2 mL, 1.2 g, 0.015 mol), and
50 mL of THF were stirred overnight and the solid amide 17
was collected, then slurried in 100 mL of water to which excess
sodium bicarbonate was added, collected, and dried at 100 °C/
20 Torr/1 h to give 3.03 g (66%) of amide 17. This was boiled
under reflux with 30 mL of phosphorus oxychloride for 2 h,
allowed to cool to 20 °C, and quenched in 300 mL each of ice
and water. After a few minutes, 50 mL of 50% w/w sodium
acetate trihydrate was added. The organic solid was collected,
washed with water, then methanol, and then was dried at 80
°C/20 Torr/1 h to give crude 18, which was recrystallized from
30 mL of 2-methoxyethanol, again from 21 mL of xylenes, to
give 1.91 g (44%) of small yellow needles, mp 210-212 °C.
Anal. Calcd for C16H9BrN2O: C, 59.10; H, 2.79; N, 8.62.
Found: C, 58.82; H, 2.75; N, 8.54. 1H NMR (400 MHz, CDCl3)
δ 7.53 (1H, s), 7.62 (4H, s), 7.79 (2H, AA′XX′, J ) 8.6), 8.21
(2H, AA′XX′, J ) 8.6). 13C NMR (100 MHz, CDCl3) δ 114.1,
118.7, 123.5, 124.9, 126.3, 126.7, 127.1, 131.3, 132.7, 1331,
151.9, 159.8.
λ
max 302 nm (ꢀ ) 27 900), 402 (ꢀ ) 29 100). Fl Em: λmax ) 505
nm, Φf ) 0.63.
Syn th esis of Tetr a eth yl (E)-2-Bu ten e-1,4-d ip h osp h o-
n a te (22). (E)-1,4-Dichloro-2-butene (25.0 g, 0.200 mol) and
triethyl phosphite (79 mL, 76.31 g, 0.500 mol, Williams &
Wilkins Co.) were heated under an air-condenser whose
effluent led to an ice-cooled dewar condenser. Reaction began
at 150 °C, then, after an hour, a sudden exotherm to 193 °C
occurred, while about 20 mL of chloroethane collected in the
condenser. The residue was distilled thru a spray-trap/air
condenser to give, after discarding a fore-run, a colorless oil,
bp mostly 187-189 °C/0.55 Torr, 58.7 g (97%), d ) 1.1265 at
24 °C (lit. 65%, bp 226 °C/15 Torr;32 93.5%, bp 149-152 °C/
0.1-0.15 Torr33). H NMR (400 MHz, CDCl3) δ 1.09 (12H, dt,
1
4
J ) 7.2, J PH ) 1.8), 2.36 (4H, m), 3.87 (8H, m), 5.38 (2H, m).
13C NMR (100 MHz, CDCl3) δ 16.6 (3J PC ) 5.8), 30.7 (1J PC
)
137.6), 62.1 (2J PC ) 6.5), 124.5 (2J PC ) 3.7).
Syn th esis of Tetr a eth yl 1,4-Xylylen ed ip h osp h on a te
(30). Triethyl phosphite (722 mL, 700 g, 4.56 mol) and 1,4-
xylylene dichloride (100 g, 0.572 mol) were heated under a
plain column to allow byproduct chloroethane to distill, which
began at 147 °C and was complete after a few hours at 159
°C, 69 mL being captured by an ice-cooled dewar condenser.
Most of the excess triethyl phosphite was distilled up to 180
°C, and the residue, at 90 °C, was poured into 1400 mL of
hexane with stirring. Crystallization was complete at -2 °C
to give, after drying at 22 °C/0.5 Torr/18 h, 211 g (98%) of white
odorless plates, mp 75-77 °C. Recrystallization of an earlier
batch from 10 mL/g of hexane, after decantation from a lower
layer of polar impurity and keeping at -2 °C, gave 87% rec.
of mp 76-78.5 °C (best lit. 100%, mp 73-74 °C,34 73-74 °C;35
1HMR 60 MHz36,37).
Syn th esis of Dieth yl 9,9-Dip r op ylflu or en e-2,7-d ica r -
boxyla te (34). A mixture of 9,9-dipropylfluorene-2,7-dicar-
boxylic acid18 (33, 38.5 g, 0.1138 mol), 1 L of ethanol, and 10
mL of methanesulfonic acid was boiled under reflux for 44 h,
cooled to 20 °C, and diluted with 2 L of water. The resulting
suspension was made to pH ≈9 by addition of sodium carbon-
ate monohydrate. The collected product was air-dried for 2
weeks to give 41.3 g (92%), mp 148-152 °C. The analytical
sample was recrystallized from 20 mL/g of 95% ethanol, mp
149-152 °C. Calcd for C25H30O4: C, 76.11; H, 7.67. Found: C,
76.38; H, 7.71. IR (CHCl3, cm-1) 3013 (ArCH), 2980 & 2960 &
2906 & 2870 & 2840 (alCH), 1700 (vs, CdO), 1606 (Ar CdC),
1283 & 1260 & 1237 & 1207 (vs, CsO).
Syn th esis of 9,9-Dip r op ylflu or en e-2,7-d im eth a n ol (35).
The Grignard reagent of 2,7-dibromo-9,9-dipropylfluorene18
(36, 40.8 g, 0.100 mol) with magnesium (4.864 g, 0.200 mol,
Reade RMC-3, 99.98%) was prepared in 400 mL of THF, then
cooled in an ice bath. To the thick suspension was added DMF
(15.5 mL, 14.62 g, 0.200 mol), and this was held at 40 °C for
1 h, by which time all lumps had broken up. At 36 °C 200 mL
of 3 M hydrochloric acid was added with ice-cooling. The upper
organic layer was dried over calcium chloride, then further
with sodium sulfate, then evaporated to give 30.6 g (100%
crude) of orange oily 9,9-Dip r op ylflu or en e-2,7-d ica r boxa l-
d eh yd e (37). (A sample from an earlier run was chromato-
graphed on Silica Gel, eluting with toluene, and the residue
on evaporation crystallized from ethanol-water to give white
solid, mp 111-112 °C.) With mechanical stirring, the 0.100
mol of crude 36 in 100 mL of toluene was treated with 65%
sodium bis(2-methoxyethoxy)aluminum hydride in toluene
(Red-Al, 34 mL, 0.120 mol) in 200 mL of toluene, which caused
Syn th esis of Bis(4-m eth oxyp h en yl)a m in e (19). In order
of addition, p-anisidine (59.25 g, 0.481 mol), 4-bromoanisole
(62.2 mL, 92.9 g, 0.497 mol), 1200 mL of toluene, tris-
(dibenzylideneacetone)dipalladium(0) (3.18 g, 0.00347 mol),
1,1′-bis(diphenylphosphino)ferrocene (2.57 g, 0.00414 mol,
Norquay Technologies, Inc.), and sodium tert-butoxide (60.9
g, 0.634 mol) were stirred and heated rapidly to 70 °C, then
slowly to reflux (110-106 °C) for 24 h, and then cooled in a
water bath to 20 °C, when 250 mL more toluene was added.
The solids were filtered off and washed with 250 mL of toluene.
The filtrates were evaporated, and the residue recrystallized
from 750 mL of heptane to give 93 g (85% crude), which was
extracted from 7.5 cm of Merck 10181 Silica Gel in a large
Ace-kau with 1200 mL of cyclohexane. The extract was kept
at 20 °C for 3 days to give white plates, which were collected,
washed with 500 mL of hexane, and air-dried to yield 71.1 g
(64%), mp 103-104 °C (lit.20 mp 105 °C).
Syn t h esis of 2-(4-Cya n op h en yl)-5-{4-[b is(4-m et h oxy-
p h en yl)a m in o]p h en yl} oxa zole (20). A mixture of 5-(4-
bromophenyl)-2-(4-cyanophenyl)oxazole (18, 6.50 g, 0.0200
mol), bis(4-methoxyphenyl)amine (19, 4.82 g, 0.0210 mol), 200
mL of toluene, tris(dibenzylideneacetone)dipalladium(0) (0.23
g, 0.00025 mol), 1,1′-bis(diphenylphosphino)ferrocene (0.19 g,
0.00034 mol), and sodium tert-butoxide (2.50 g, 0.026 mol) was
treated as for 19 above. The toluene filtrates were chromato-
graphed on a 4 × 16 cm column of Merck 10181 Silica Gel,
with rejection of the toluene eluates. Dichloromethane eluates
were rejected, then THF eluted 20 as a dark yellow oil after
evaporation. This was crystallized from 100 mL of 1-butanol,
and recrystallized from 1-propanol to give 5.00 g (53%) of dark
yellow prisms, mp 165-167.5 °C. Calcd for C30H23N3O3: C,
(32) Pudovik, A. N. J . Gen. Chem. USSR 1949, 19, 1179; Chem.
Abstr. 1950, 44, 1006a.
(33) CIBA Ltd., French Patent 1,503,429 (Nov 24, 1967); Chem.
Abstr. 1968, 69, 96874.
(34) Stilz, W.; Pommer, H. German Patent 1,108,219 (J un 8, 1961);
Chem. Abstr. 1962, 57, P732f.
(35) Chantrell, P. G.; Pearce, C. A.; Toyer, C. R.; Twaits, R. J . Appl.
Chem. 1965, 15, 460.
1
76.09; H, 4.90; N, 8.88. Found: C, 75.60; H, 4.89; N, 8.69. H
NMR (400 MHz, CDCl3) δ 3.84 (6H, s), 6.88 (4H, AA′XX′, J )
9.0), 6.97 (2H, AA′XX′, J ) 9.0), 7.12 (4H, AA′XX′, J ) 8.9),
7.35 (1H, s), 7.52 (2H, AA′XX′, J ) 8.9), 7.77 (2H, AA′XX′, J )
8.7), 8.17 (2H, AA′XX′, J ) 8.7). 13C NMR (100 MHz, CDCl3)
δ 55.9, 113.4, 118.9, 119.1, 119.9, 122.7, 125.8, 126.7, 126.9,
127.5, 131.7, 133.0, 140.4, 149.9, 153.4, 156.9, 158.7. UV-vis:
(36) Khan, M. M. T.; Martell, A. E. Inorg. Chem. 1975, 14, 676.
(37) Ernst, L. Org. Magn. Reson. 1977, 9, 35.
850 J . Org. Chem., Vol. 68, No. 3, 2003

Diarylamino Groups as Photostable Auxofluors
an exotherm to 53 °C. An hour of stirring was followed by
addition of a mixture of 100 mL of water, 100 mL of ice, and
85 mL of 12 M hydrochloric acid, slowly at first. At 50 °C the
upper organic layer was separated and washed with 200 mL
of warm water, then kept at -2 °C to obtain 16.6 g of 35, mp
128-137 °C; this was recrystallized from 95 mL of toluene at
25 °C to obain, in two crops, 16.6 g (53%) of product, mp 135-
137 °C. Calcd for C21H26O2‚0.1H2O: C, 81.25; H, 8.44. Found:
C, 80.88; H, 8.46. IR (CHCl3, cm-1) 3600 (OH), 2935 (br, inter-
bonded OH), 3005 (ArCH), 2960 & 2930 & 2906 & 2875 & 2840
(alCH), 1202 & 1003 (CsO str).
was obtained by further dilution with 800 mL of water and
cooling at -20 °C to give 2 g. Combined, this was passed thru
a 4 × 15 cm column of Merck 10181 Silica Gel in dichlo-
romethane, followed by 1.5 L of this solvent. The eluate was
evaporated to give 28 g of crystals, which were recrystallized
from a mixture of 150 mL each of abs ethanol and methanol
at -2 °C for 2 days to give tan prisms, mp 128-130 °C, 20.1
g (69%). Anal. Calcd for C21H18N2O2: C, 76.34; H, 5.49; N, 8.48.
Found: C, 76.46; H, 5.35; N, 8.32. 1H NMR (400 MHz, CDCl3)
δ 3.83 (6H, s), 6.81 (2H, AA′XX′, J ) 8.9), 6.90 (4H, AA′XX′, J
) 9.1), 7.12 (4H, AA′XX′, J ) 9.1), 7.37 (2H, AA′XX′, J ) 8.9).
IR (CHCl3, cm-1) 3020 & 3000 (w, ArCH), 2980 & 2920 & 2870
& 2850 (alCH), 2218 (s, cyano), 1596 (s, C-N & CdC), 1235
& 1205 (vs, Ar-O & al-O), 1162, 1111, 1040 (s, C-O-C).
Syn th esis of Cr u d e 4-[Bis(4-m eth oxyp h en yl)a m in o]-
ben za ld eh yd e (23e). With cannulae and septa, diisobutyla-
luminum hydride (DIBALH, 20% w/w in toluene, 41 mL, 0.050
mol) was pushed into a pressure-equalized addition funnel.
Then 4-[bis(4-methoxyphenyl)amino]benzonitrile (27, 11.0 g,
0.0333 mol) was added to a flask in a bath below the funnel,
followed by 330 mL of ether, in which the nitrile was only
partially soluble. Dry ice and 1-propanol were placed in the
bath (temperature -56 °C), then the DIBALH was added
dropwise below -50 °C. The mixture was allowed to warm to
-30 °C during which time most solid dissolved. Protected by
Drierite tubes, the reaction flask was placed in a -20 °C
freezer overnite. In a 1-L flask a quench mixure of 125 mL
each of ice and water along with 25 mL of acetic acid was
purged with argon and the liquid portion of the reaction
mixture was pumped in using cannulae and septa. The
quenchate was stirred an hour and the organic layer was
evaporated to an oil, treated with 100 mL benzene, and
evaporated again to yield 10.6 g (96% crude) of yellow oil,
which would not crystallize, so it was made up to 50 mL with
dry DMF for use in Wadsworth-Emmons reactions below. IR
(CHCl3, cm-1) 3030 & 3010 (ArCH), 298 & 2960 & 2910 & 2840
(w, alCH), 2840 (w, ald. C-H), 1677 (s, br, CdO), 1590 (vs,
C-N & CdC), 1238 & 1212 (vs, Ar-O & al-O), 1159 vs & 1104
& 1031 (C-O-C).
Gen er a l P r oced u r e for Wa d sw or th -Em m on s Rea c-
tion s To F or m Hexa tr ien es 24a -d , 26a -c; Distyr ylben -
zen es 31d -g, 32a -e; a n d Distyr ylflu or en es 40a ,d ,e, All
(E). The aldehyde (0.0933 mol) and the diphosphonate (0.0444
mol) in 300 mL of DMF were treated with a solution of
potassium tert-butoxide (0.175 mol) in 100 mL of DMF at 20-
50 °C with cooling, if necessary. The yellow products usually
separated. After the reaction was kept at 20 °C overnight, it
was poured into 1 L of methanol and stirred 30 min, and the
product was collected, washed with methanol, and air-dried
to give 70-100% yields (except 32a ) of crude alkene, which
was extracted from adsorbent in a large Ace-Kau, and the
extract was cooled to give pure product, typically in 76-90%
yield. The adsorbent, solvent, yield when this exact method
was used, assays, and NMR spectra are given below. The
absorption and fluorescence data, as well as that of related
fluors, are given in Table 1 for the hexatrienes, Table 2 for
the distyrylbenzenes, and Table 3 for the distyrylfluorenes,
all in toluene unless otherwise indicated.
Syn th esis of 2,7-Bis(ch lor om eth yl)-9,9-Dip r op ylflu o-
r en e (38). A three-phase mixture of 250 mL of 12 M hydro-
chloric acid, 140 mL of toluene, and 9,9-dipropylfluorene-2,7-
dimethanol (35, 14.1 g, 0.0454 mol) was stirred rapidly at 23
°C for 19 h. The lower acid layer was sucked out and replaced
with 250 mL of acid. Two more hours of stirring seemed to
indicate completion of the reaction by TLC on Whatman MK6F
Silica Gel, CHCl3, UV: no mono-Cl at Rf 0.14, di-Cl Rf 0.79.
So 100 mL each of toluene and heptane were added, and the
upper layer was washed with 250 mL of water and dried briefly
with calcium chloride and evaporated to give a nice tan solid,
which was recyrstallized from a minimum of 2-propanol to give
white blades, mp 116-119.5 °C, 9.70 g (61%) (lit.18 64%, mp
115-117 °C).
Syn th esis of 2,7-Bis(d ieth ylp h osp h on o)-9,9-d ip r op y-
lflu or en e (39). Triethyl phosphite (16 mL, 0.112 mol) was
heated with 2,7-bis(chloromethyl)-9,9-dipropylfluorene (37,
9.70 g, 0.0279 mol) beyond a violent exotherm at 120 °C to
reflux, which was maintained for 1 h, during which time the
pot temperature went from 163 °C to 170 °C. This was allowed
to cool below 100 °C and 80 mL of 2,2,4-trimethylpentane was
added, while maintaining stirring, followed by an overnight
sit at 20 °C. The product was collected, washed with 75 mL of
2,2,4-trimethylpentane, and dried to give gleaming white
prisms, mp 125-127.5 °C, 13.59 g (88%) (lit. from di-Cl 90%,
mp 126-128 °C, from di-Br 43%, mp 126-128 °C18).
Syn t h esis of 4-(Dip h en yla m in o)b en za ld eh yd e (23d ).
With use of a motor-driven Teflon paddle stirrer, 1.00 L of dry
DMF in a water bath was treated below 15 °C with phosphorus
oxychloride (75 mL, 122.6 g, 0.800 mol) in 1/5 portions, each
in a thin stream. Warm water was then added to the bath to
attain 30 °C in the flask, then triphenylamine was added
rapidly (98.13 g, 0.400 mol) and the bath was heated to
maintain 85-88 °C for a total of 3 h. The dark mixture was
cooled in ice to 40 °C and quenched in 800 g each ice and water
with propeller stirring, to which was then added 800 mL of
50% sodium acetate trihydrate w/w, followed by a few minutes
of stirring and an overnight sit. The crude product was
collected and slurried with a propeller in 1600 mL of 47.5%
ethanol v/v for 15 min and re-filtered, and the damp solid was
recrystallized from 1800 mL of 95% ethanol, decanted hot, and
kept at 20 °C for 5 days, followed by 4 h at -2 °C. The brown
needles were collected, washed with 250 mL of cold 95%
ethanol, and dried 60 °C/20 Torr/20 h to give 92.8 g (85%) of
brown needles, mp 132-134 °C (lit. no yield, mp22 132-133.5
°C).
1,6-Di-4-bip h en ylyl-1,3,5-h exa tr ien e (24b). From 23b
and 24. Acidic alumina, toluene, mp 303-308 °C. Anal. Calcd
for C30H24: C, 93.71; H, 6.29. Found: C, 94.09; H, 6.04. Too
insoluble for NMR.
Syn th esis of Bis(4-m eth oxyp h en yl)a m in oben zon itr ile
(27). Added in the order given, bis(4-methoxyphenyl)amine
(19, 21.4 g, 0.0933 mol), 4-bromoacetonitrile (6.1 g, 0.0887 mol),
tris(dibenzylideneacetone)dipalladium(0) [Pd2(dba)3, 1.02 g,
0.00112 mol], 1,1′-bis(diphenylphosphino)ferrocene (dppf, 0.83
g, 0.00149 mol, Norquay Technology), and sodium tert-butoxide
(11.1 g, 0.116 mol) were heated to gentle reflux for 44 h at
111 °C. (Tlc on Whatman MK6F Silica Gel, ethyl acetate, UV,
showed 19 at Rf 0.44 and 27 at Rf )0.80; no change between
21 and 44 h.) The solids were filtered off and washed with 2
× 50 mL of toluene. The filtrates were evaporated to 33.5 g of
black oil which crystallized from 260 mL of 95% ethanol at
-20 °C ovenite. This was diluted with 260 mL of methanol
and the solid collected (24 g when air-dried) and a second crop
1,6-Bis[7-(4-ter t-bu tylph en yl)-9,9-dipr opyl-2-flu or en yl]-
1,3,5-h exa tr ien e (24c). From 23c and 24. Neutral alumina,
heptane, recryst. 2-butoxyethanol/2-propanol, mp 278-282 °C.
Anal. Calcd for C64H72: C, 91.37; H, 8.63. Found: C, 91.73; H,
1
8.40. H NMR (400 MHz, CDCl3) δ 0.73 (20H, m), 1.41 (18H,
s), 2.03 (8H, m), 6.64 (2H, dd, J ) 7.0, J ) 3.1), 6.73 (2H, d, J
) 15.4), 7.02 (2H, ddd, J ) 15.4, J ) 7.0, J ) 3.1), 7.60 (20H,
m). 13C NMR (100 MHz, CDCl3) δ 14.9, 17.6, 31.8, 35.0, 43.3,
55.7, 120.3, 120.9, 121.8, 126.1, 126.2, 129.1, 129.2, 133.6,
133.9, 136.8, 139.1, 140.2, 140.3, 141.0, 150.6, 151.9, 152.0.
J . Org. Chem, Vol. 68, No. 3, 2003 851

Kauffman and Moyna
1,6-Bis[4-(diph en ylam in o)ph en yl]-1,3,5-h exatr ien e (24d).
From 23d and 24. Silica Gel, toluene; evaporated, recrystal-
lized from 1-butanol/xylenes, mp 235-238 °C (lit.38). Anal.
Calcd for C42H34N2: C, 89.01; H, 6.05; N, 4.94. Found: C, 89.35;
1,4-Bis(2-p h en ylstyr yl)ben zen e (32a ). From 30 and 25a .
Neutral alumina, heptane:toluene 10:1 (27%, 0% by normal
method), mp 192-194 °C (lit. mp 193-194 °C,41 188-189 °C46).
1H NMR (400 MHz, CDCl3) δ 6.82 (4H, s), 6.90 (2H, s), 7.21
(4H, m), 7.32 (16H, m). 13C NMR (400 MHz, CDCl3) δ 127.8,
127.9, 128.0, 128.3, 128.6, 129.0, 129.6, 130.8, 136.3, 140.8,
142.9, 143.9.
1,4-Bis[4′-(d im e t h yla m in o)-2-p h e n ylst yr yl]b e n ze n e
(32b). From 30 and 25b. Recrystallized from 2-ethoxy-
ethanol, mesitylene twice, then DMA to obtain mp 247-248
°C pc, 249-252°. Anal. Calcd for C38H36N2: C, 87.99; H, 6.61;
N, 5.40. Found: C, 87.64; H, 6.94; N, 5.53. 1H NMR (400 MHz,
CDCl3; mixture of E and Z isomers in 3:1 ratio determined by
integration of methyl peaks; when signals for the same proton
in both isomers were resolved, both are listed with the major
component appearing first) δ 2.98 & 3.00 (12H, s), 6.67 (4H,
m), 6.74 & 6.95 (4H, s), 6.78 & 6.76 (2H, s), 7.19 & 7.07 (4H,
AA′XX′, J ) 9.2), 7.32 & 7.21 (10H, m).
1
H, 6.02; N, 5.32. H NMR (400 MHz, CDCl3) δ 6.50 (2H, dd, J
) 7.1, J ) 3.1), 6.54 (2H, d, J ) 15.4), 6.81 (2H, ddd, J ) 15.4,
J ) 7.1, J ) 3.1), 7.04 (8H, m), 7.13 (8H, m), 7.29 (12H, m).
13C NMR (100 MHz, CDCl3) δ 123.4, 123.9, 124.9, 127.6, 128.2,
129.7, 132.1, 132.2, 133.5, 147.5, 147.9.
1,1,6,6-Tetr a p h en yl-1,3,5-h exa tr ien e (26a ). From 25a
and 26. Acidic alumina, heptane, mp 194-195 °C pc, 200-
207 °C; best 206-207 °C (lit. 185 °C,39 208 °C,40 192-196 °C,41
202-203 °C,42 1H NMR 90 MHz43).
1,1,6,6-Tetr a -4-Bip h en ylyl-1,3,5-h exa tr ien e (26b). From
25b and 26. Neutral alumina, toluene, mp s. 317 °C, 324-
330 °C pc, 334-337 °C dec. Anal. Calcd for C30H24: C, 94.15;
H, 5.85. Found: C, 94.03; H, 5.58. 1H NMR (400 MHz,
pyridine-d5) δ 5.70 (4H, s), 7.45 (4H, t, J ) 8.1), 7.53 (8H, t, J
) 8.1), 7.79 (8H, d, J ) 8.1), 7.85 (8H, d, J ) 8.1), 8.07 (8H, d,
J ) 8.1). Too insoluble for 13C.
1,4-Bis{2,2-[b is(4-d im e t h yla m in o)p h e n yl]e t h e n yl}-
ben zen e (32c). From 30 and 25c. Recrystallized from 2-ethoxy-
ethanol, 2-butoxyethanol, then mesitylene to obtain mp 244-
247 °C pc, 249-253 °C. Anal. Calcd for C42H46N4: C, 83.26;
1,4-Bis[9-flu or en ylid en e]-2-b u t en e (26c). From fluo-
renone and 26. Mp 333-337 °C dec (lit. mp 331.5-333 °C,25
340 °C44). Too insoluble for NMR.
1
H, 7.49; N, 9.25. Found: C, 83.17; H, 7.66; N, 8.97. H NMR
(400 MHz, CDCl3) δ 2.98 (6H, s), 3.00 (6H, s), 6.67 (2H, s),
6.68 (8H, AA′XX′, J ) 8.8), 6.89 (4H, s), 7.10 (4H, AA′XX′, J )
8.8), 7.23 (4H, AA′XX′, J ) 8.8). 13C NMR (100 MHz, CDCl3)
δ 40.9, 41.0, 112.3, 112.6, 124.4, 129.1, 129.2, 131.8, 133.2,
136.6, 142.5, 150.0, 150.3.
1,4-Bis{2,2-[bis(4-methoxyphenyl)ethenyl]}benzene (32d).
From 30 and 25d . Recrystallized from dibutyl ether, mp
166.5-169.5 °C (90%). Anal. Calcd for C38H34O4: C, 82.28; H,
6.18. Found: C, 82.39; H, 6.14. 1HMR (400 MHz, CDCl3) δ 3.84
(6H, s), 3.86 (6H, s), 6.76 (2H, s), 6.84 (4H, s), 6.85 (4H, AA′XX′,
J ) 8.8), 6.87 (4H, AA′XX′, J ) 8.8), 7.12 (4H, AA′XX′, J )
8.8), 7.25 (4H, AA′XX′, J ) 8.8). 13C NMR (100 MHz, CDCl3)
δ 55.6, 55.7, 113.9, 114.3, 126.4, 129.3, 129.4, 133.2, 136.4,
137.0, 141.9, 159.3, 159.6.
1,4-Bis(flu or en ylid en em eth yl)ben zen e (32e). From 30
and fluorenone. Recrystallized from DMF, mp 215-217.5 °C
(lit. mp 205-206 °C,47 212-214 °C48). Mass spectrum.49 1H
NMR (400 MHz, CDCl3) δ 7.15 (2H, dt, J ) 1.3, J ) 7.3), 7.37
(2H, dt, J ) 7.6, J ) 1.0), 7.38 (2H, dt, J ) 7.3, J ) 1.3), 7.43
(2H, dt, J ) 7.3, J ) 1.0), 7.73 (4H, s), 7.76 (6H, m), 7.78 (2H,
s), 7.85 (2H, td, J ) 7.3, J ) 1.0). 13C NMR (100 MHz, CDCl3)
δ 120.1, 120.3, 120.7, 124.8, 127.1, 127.2, 127.5, 128.7, 129.1,
130.0, 136.9, 137.1, 137.3, 139.6, 139.9, 141.8.
1,4-Bis[4′-(d ip h en yla m in o)styr yl]ben zen e (31d ). From
30 and 23d . Florisil, 1-chlorobutane, recrystallized from 1-bu-
tanol, 87%, mp 198-199 °C pc, 203-205 °C. The product of
an earlier run was recrystalllized from 1-pentanol, Anal. Calcd
for C46H36N2‚0.25C5H12O: C, 88.83; H, 6.15; N, 4.39. Found:
1
C, 88.71; H, 6.36; N, 4.21. H NMR (400 MHz, CDCl3) δ 7.08
(20H, m), 7.28 (4H, AA′XX′, J ) 8.6), 7.30 (4H, AA′XX′, J )
8.5), 7.41 (4H, AA′XX′, J ) 8.6), 7.50 (4H, s). 13C NMR (100
MHz, CDCl3) δ 123.5, 124.0, 124.9, 127.0, 127.1, 127.8, 128.3,
129.7, 132.0, 137.1, 147.8, 148.0. τf ) 1.86 ns.
1,4-B is [4′-b is (4-m e t h o x y p h e n y l)a m in o s t y r y l]b e n -
zen e (31e). From 30 and 23e. Extracted from Soxhlet with
hexanes, recrystallized from dibutyl ether, then 1-pentanol,
mp 175 °C pc, 178-181 °C. Anal. Calcd for C50H44N2O4‚
0.25C5H12O: C, 81.49; H, 6.02; N, 3.80. Found: C, 81.18; H,
1
6.20; N, 3.71. UV-vis and Fl em, see Figure 4. H NMR (400
MHz, CDCl3) δ 3.82 (12H, s), 6.86 (8H, AA′XX′, J ) 9.0), 6.93
(4H, AA′XX′, J ) 8.7), 6.95 (2H, d, J ) 16.0), 7.06 (2H, d, J )
16.0), 7.09 (8H, AA′XX′, J ) 9.0), 7.34 (4H, AA′XX′, J ) 8.7),
7.47 (4H, s). Too insoluble for 13C. τf ) 2.25 ns.
1,4-Bis[4′-(d im eth yla m in o)styr yl]ben zen e (31f). From
30 and 23f. Recrystallized from diethylene glycol/diphenyl-
methane, 86%, mp 325-332 °C dec (lit.17,45). Anal. Calcd for
9,9-Dip r op yl-2,7-d istyr ylflu or en e (40a ).18 1H NMR (400
MHz, CDCl3) δ 0.74 (10H, m), 2.04 (4H, m), 7. 22 (4H, AB, J
) 16.4), 7.30 (2H, tt, J ) 1.1, J ) 7.4), 7.41 (4H, dd, J ) 7.4,
J ) 7.8), 7.53 (4H, m), 7.58 (4H, dd, J ) 1.1, J ) 7.8), 7.69
(2H, dd, J ) 1.5, J ) 7.0). 13C NMR (400 MHz, CDCl3) δ 14.9,
17.6, 43.3, 55.6, 120.3, 121.1, 126.2, 126.9, 127.9, 128.4, 129.1,
129.7, 136.7, 137.9, 141.0, 152.0.
C
26H28N2: C, 84.74; H, 7.66; N, 7.60. Found: C, 84.47; H, 7.38;
N, 7.50. 1HMR (400 MHz, CDCl3) δ 3.01 (12H, s), 6.75 (4H,
bd, J ) 8.3), 6.93 (2H, d, J ) 16.3), 7.07 (2H, d, J ) 16.3), 7.44
(4H, d, J ) 8.3), 7.46 (4H, s). Too insoluble for 13C.
1,4-Bis[2-(9-ju lolid in yl)eth en yl]ben zen e (31g). From 30
and 23d ,9 recrystallized from DMA, mesitylene, chromato-
graphed on Silica Gel with dichloromethane in dim light,
evaporated, mp 240-248 °C dec Anal. Calcd for C34H36N2‚0.25-
CH2Cl2: C, 81.55; H, 7.32; N, 5.53. Found: C, 81.88; H, 6.81;
N, 5.26. 1H NMR (400 MHz, CDCl3):δ 2.01 (8H, q, J ) 6.1),
2.80 (8H, t, J ) 6.1), 3.19 (8H, t, J ) 6.1), 6.86 (2H, d, J )
16.4), 6.97 (2H, d, J ) 16.4), 7.00 (4H, s), 7.42 (4H, s). 13C NMR
(100 MHz, CDCl3) δ 22.5, 28.1, 50.4, 121.8, 123.8, 125.5, 125.7,
126.5, 128.7, 137.1, 138.1, 143.1.
1,4-Bis[4′-bis(d ip h en yla m in o)styr yl]-9,9-d ip r op ylflu o-
r en e (40d ). From 23d and 39. Neutral alumina, methylcy-
clohexane, lemon-yellow solid, mp 262 °C pc, 266-268 °C
(83%). Anal. Calcd for C59H52N2: C, 89.81; H, 6.64; N, 3.55.
1
Found: C, 89.24, 89.26; H, 6.51, 6.55; N, 3.38, 3.35. H NMR
(400 MHz, CDCl3) δ 0.73 (10H, m), 2.03 (4H, m), 7.07 (4H, tt,
J ) 7.3, J ) 1.3), 7.10 (4H, AA′XX′, J ) 8.5), 7.14 (4H, AB, J
) 16.4), 7.15 (8H, dd, J ) 1.3, J ) 8.8), 7.30 (8H, dd, J ) 7.3,
J ) 8.3), 7.45 (4H, AA′XX′, J ) 8.5), 7.50 (4H, m), 7.67 (2H,
(38) Bunning, T. J .; Kirkpatrick, S. M.; Natarajan, L. V.; Tondiglia,
V. P.; Tomlin, D. W. Chem. Mater. 2000, 12, 2842.
(39) Bestmann, H.-J .; Armsen, R.; Wagner, H. Chem. Ber. 1969, 102,
2259.
(40) Kuhn, R.; Fischer, H. Chem. Ber. 1961, 94, 3060.
(41) Horner, L.; Hoffmann, H.; Klink, W.; Ertel, H.; Toscano, V. G.
Chem. Ber. 1962, 95, 581.
(46) Yang, Z.; Geise, H. J .; Nouwen, J .; Adriaensens, P.; Franco, D.;
Vanderzande, D.; Martens, H.; Gelan, J .; Mehbod, M. Synth. Met. 1992,
47, 111.
(47) Scho¨nberg, A.; Singer, E.; Schulze-Pannier, H. Chem. Ber. 1973,
106, 2663.
(48) Tewari, R. S.; Kumari, N.; Kendurkar, P. S. J . Indian Chem.
Soc. 1977, 54, 443.
(42) Du¨rr, H. Chem. Ber. 1970, 103, 369.
(43) de la Mata, F.; Grubbs, R. H. Organomatallics 1996, 15, 577.
(44) Severin, T.; Schnabel, I. Chem. Ber. 1969, 102, 1707.
(45) Malkes, L. Y.; Shubina, L. V.; Vinetskaya, Y. M. Monokrist.,
Stsintill. Org. Lyuminofory 1967, 78; Chem. Abstr. 1968, 69, 82035.
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Lucas, D.; Mugnier, Y.; Lessard, J . New J . Chem. 1997, 21, 929.
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80, 969.
852 J . Org. Chem., Vol. 68, No. 3, 2003

Diarylamino Groups as Photostable Auxofluors
dd, J ) 0.8, J ) 7.6). 13C NMR (400 MHz, CDCl3) δ 14.9, 17.6,
43.3, 55.6, 120.2, 120.9, 123.4, 124.0, 124.9, 125.9, 127.7, 127.9,
128.1, 129.7, 132.2, 136.9, 140.8, 147.6, 148.0, 151.9. τf ) 1.73
ns.
erties, Charles R. Hurlbut and P. I., Ludlum Measure-
ments, Inc., Sweetwater, TX 79556. Online literature
searches and editing of the manuscript were the effort
of Leslie Ann Bowman; some UV spectra were deter-
mined by Farzad Kobarfard and Chad Englert and some
fluorescence spactra by Dwight Crawford, and the Φf
values were determined by Robert T. Swoboda under
the direction of Michael Bruist, all at USP. Some of the
NMR spectra were run and/or interpreted by Matthew
R. Banghart and by Farzad Kobarfard at USP, and by
Walter J . Boyko, Department of Chemistry, Villanova
University. J ames Bishop determined the decay times
under the direction of Randall C. Ruchti, Department
of Physics, University of Notre Dame. Detailed synthetic
procedures were provided by Casey Kernag, Hiroyuki
Nishide, and Tsuyoshi Michinobu. Discussions with
Charles R. Hurlbut (who also prepared the figures),
Randall C. Ruchti, Walter M. F. Fabian, and Charles
J . Kelley (the latter pair as consultants in the program)
were very valuable.
1,4-Bis[4′-bis(4-m eth oxyph en yl)am in ostyr yl]-9,9-dipr o-
p ylflu or en e (40e). From 23e and 39, mp 236-238 °C (100%
crude). Extracted from a Soxhlet with 1-chlorobutane and kept
3 days at 20 °C, mp 225 °C pc, 239-240 °C (76%). Anal. Calcd
for C63H60N2O4: C, 83.23; H, 6.65; N, 3.08. Found: C, 83.71;
1
H, 6.43; N, 3.10. H NMR (400 MHz, CDCl3) δ 0.71 (10H, m),
2.01 (4H, m), 3.83 (12H, s), 6.87 (8H, AA′XX′, J ) 9.1), 6.94
(4H, AA′XX′, J ) 8.5), 7.08 (4H, AB, J ) 16.8), 7.10 (8H,
AA′XX′, J ) 9.1), 7.38 (4H, AA′XX′, J ) 8.5), 7.47 (4H, m),
7.64 (2H, dd, J ) 1.0, J ) 7.6). τf ) 2.05 ns.
Ack n ow led gm en t. Peter T. Litak brought the paper
by Belfield14 to our attention and was the first to
prepare dialdehyde 37. Distyrylbenzenes 31f,g and
32a -e were prepared under contract with Bicron Divi-
sion, Saint-Gobain/Norton Industrial Ceramics Corp.,
Newbury, OH. Major financial support for the remain-
der was provided under an SBIR Phase I contract from
the U.S. Department of Energy, #DE-FG03-97ER82419/
A000, Development of Scintillators and Waveshifters
for Detection of Ionizing Radiation, and Phase II,
#DE-FG03-97ER82419, Development of Scintillators
and Waveshifters for Detection of Ionizing Radiation
and of Manufacturing Methods to Improve Aging Prop-
Su p p or t in g In for m a t ion Ava ila b le: 1H and 13C NMR
data. This material is available free of charge via the Internet
at http://pubs.acs.org.
J O020333+
J . Org. Chem, Vol. 68, No. 3, 2003 853