Synthesis of an isophorone-based nonlinear optical chromophore

Article abstract of DOI:10.1081/SCC-200030646

The synthesis of a "CLD-type" nonlinear optical chromophore incorporating the isophorone unit to rigidize the polyene segment is described. The synthesis required seven steps with an overall yield of 17%.

Full text of DOI:10.1081/SCC-200030646

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Synthesis of an
Isophorone‐Based Nonlinear
Optical Chromophore
a
a
Matthew C. Davis , Andrew P. Chafin , Richard
a
a
A. Hollins , Lawrence C. Baldwin , Eric D.
a
a
a
Erickson , Peter Zarras & Elliott C. Drury
a
Chemistry & Materials Division (Code 4T4200D),
Research Department , Naval Air Warfare Center
Weapons Division , China Lake, California, 93555,
USA
Published online: 10 Jan 2011.
To cite this article: Matthew C. Davis , Andrew P. Chafin , Richard A. Hollins ,
Lawrence C. Baldwin , Eric D. Erickson , Peter Zarras & Elliott C. Drury (2004)
Synthesis of an Isophorone‐Based Nonlinear Optical Chromophore, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 34:18, 3419-3429, DOI: 10.1081/SCC-200030646
To link to this article: http://dx.doi.org/10.1081/SCC-200030646
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w
SYNTHETIC COMMUNICATIONS
Vol. 34, No. 18, pp. 3419–3429, 2004
Synthesis of an Isophorone-Based
Nonlinear Optical Chromophore
*
Matthew C. Davis, Andrew P. Chafin, Richard A. Hollins,
#
Lawrence C. Baldwin, Eric D. Erickson, Peter Zarras,
‡
and Elliott C. Drury
Chemistry & Materials Division (Code 4T4200D), Research Department,
Naval Air Warfare Center Weapons Division, China Lake, California, USA
ABSTRACT
The synthesis of a “CLD-type” nonlinear optical chromophore incorpor-
ating the isophorone unit to rigidize the polyene segment is described.
The synthesis required seven steps with an overall yield of 17%.
Key Words: Aldol; Dyes; Knoevenagel; Nonlinear optical; Vilsmeier.
*
Correspondence: Matthew C. Davis, Chemistry & Materials Division(Code4T4200D),
Research Department, Naval Air Warfare Center Weapons Division, China Lake, CA
3555, USA; E-mail: matthew.davis@navy.mil.
9
#
ASEE/ONR Postdoctoral Fellow.
Engineer & Scientist Development Program, NAWCWD.
‡
3
419
DOI: 10.1081/SCC-200030646
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

3
420
Davis et al.
As part of a project to develop a second-order nonlinear optical polymer for
[
1,2]
an optical modulator application, we required the chromophores 9a,9b
Fig. 1). Structurally similar isophorone-based nonlinear optical chromophores
(
[
3]
have been prepared; however, one free hydroxyl group on the dialkylamino
moiety was necessary for further transformations (to be published elsewhere).
To start out, commercially available 1 was esterified with acetic anhy-
dride catalyzed by base to give the acetate 2 quantitatively (Sch. 1). The
acetate protection is required for the subsequent Vilsmeier-Haack formyl-
[4]
ation, which proceeded smoothly to give 3 in good yield. Next, Knoevena-
gel reaction of 3 and isophorone was conducted in the presence of a cationic
[5–7]
surfactant.
The hydrolysis of the acetate occurs initially so an extra equiv-
alent of base was required. Although the reaction was slow with moderate
yield, compound 4 precipitates pure from the aqueous work-up, making
chromatography unnecessary.
Silyl ether protection gave 5 for subsequent Wittig directed-aldol
[10]
[
8,9]
reaction
give moderate yield of a mixture of Z and E aldehydes 6a,6b, respectively.
with the acetaldehyde equivalent, N-cyclohexyl-acetimine,
to
1
The Z : E ratio was 33 : 67 by H-nuclear magnetic resonance (NMR).
Performing this reaction at 21008C did not increase the amount of E
product. Separation of 6a,6b by silica gel chromatography could only be
E
Figure 1. Structure of the chromophores 9a,9b. Protons labelled H or H are NMR
Z
diagnostic.

Synthesis of Isophorone-Based Nonlinear Optical Chromophore
3421
Scheme 1. Reagents and conditions: (a) Ac O/pyridine; (b) DMF/POCl ; (c) isophor-
2
3
2
one/cetyltrimethylammonium chloride/NaOH/H O/508C; (d) TBDMSCl/imidazole/
dimethylformamide (DMF); (e) N-cyclohexyl-acetimine/lithium diisopropylamide
ꢀ
(
LDA)/Et O, 278 to 08C; (f) oxalic acid/H O; (g) (Et) N 3HF/MeCN/408C.
2
2
3
achieved on analytical scale; therefore, the mixture was used for the sub-
sequent reactions. Deprotection to the aldehyde-alcohols 7a,7b proceeded
fast, quantitatively, and without isomerization.
The last step was a Knoevenagel condensation between 7a,7b and the
[
11]
known tricyanodihydrofuran 8 to yield the chromophore mixture 9a,9b.
In our hands, the reported preparation of 8 failed to give any product on
[
12]
several attempts. Conditions similar to He et al.
and in good yield. As a catalyst for the condensation, we chose piperidinium
provided 8 consistently
[13,14]
acetate since it has been shown to work well for similar condensations.

3
422
Davis et al.
Investigations of this step with a series of NMR tube reactions demonstrated
that the reaction was extremely clean and fast. After scale-up and work-up, the
1
solid that remained appeared perfect by H NMR, although quantitative
1
H-integration experiments demonstrated purity of only ꢀ85%. Interestingly,
the Z : E ratio was 26 : 73, indicating partial isomerization toward the thermo-
dynamically favored trans olefin, a phenomenon seen in the preparation of
[
3,15]
other isophorone-based chromophores. After further experimentation, it
was found that triturating the solid with acetone gave chromophores 9a,9b
as a homogenous crystalline powder. Ignoring some residual CH Cl used
2
2
1
as solvent for the reaction, the powder had purity of .99% by H-NMR cor-
roborated by high-pressure liquid chromatography (HPLC). Combustion
analysis showed that 9a,9b cocrystallized with 15% CH Cl . After 2
2
2
months storage, combustion analysis revealed the CH Cl had evaporated
2
2
from the crystalline product.
In summary, we report the synthesis of the nonlinear optical chromophore
9
a,9b in seven steps with 17% overall yield.
EXPERIMENTAL
Reagents were purchased from Aldrich Chemical Co. (Milwaukee, WI,
USA) and used as received. Multinuclear NMR spectra were obtained on a
1
13
Bruker AC-200 spectrometer ( H at 200 MHz, C at 50 MHz) and referenced
to solvent or tetramethylsilane. Piperidinium acetate was prepared by the
addition of 1 equivalent glacial HOAc to a cold Et O solution of piperidine
2
and suction filtration of the product. N-Cyclohexyl-acetimine was prepared
10]
[
as previously described.
thermal capillary melting point apparatus and are not corrected.
Melting points were determined on an electro-
1
Quantitative H-integration experiments were conducted on CD Cl
2
2
0
solutions with 4,4 -dimethoxyoctafluoro-biphenyl as internal standard using
1
a Bruker AMX-400 (400 MHz H). Preparative HPLC was performed using
a Shimadzu LC-10AD pump equipped with a Waters 991 diode array detector,
an Alltech Econosphere column (250 ꢁ 10 mm, 10 mm particle size), and a
Gilson CPR fraction collector in order to obtain a purified reference material
of chromophore 9a,9b. The reference material was analyzed using a Finnigan
Surveyor HPLC, Prevail Silica column (50 ꢁ 2.1 mm, 3 mm particle size), and
both a diode array detector and a Finnigan LCQ DecaXP Plus mass spectro-
metric detector used in atmospheric pressure chemical ionization negative
ion mode. Quantitation in the visible spectrum was performed at 650 nm.
Quantitation by mass spectrum used the (M-1) ion at 519 Da. Burdick and
Jackson HPLC grade acetonitrile was used as the eluent for all HPLC
analyses.

Synthesis of Isophorone-Based Nonlinear Optical Chromophore
3423
N-Ethyl-N-(2-acetoxyethyl)-aniline (2)
A solution of 82.6 g (2-(N-ethylanilino)ethanol (1) (0.5 mol) and 39.5 g
pyridine (40 mL, 1 equiv) in 300 mL of Et O was stirred in an ice bath
2
while 53.6 g acetic anhydride (49.5 mL, 0.53 mol, 1.05 equiv) was slowly
added over 15 min. The ice bath was removed and the reaction mixture was
heated at reflux for 2 hr. The organic layer was washed with H O
2
(
3 ꢁ 300 mL) followed by 1% HCl (300 mL). The organic layer was dried
(
MgSO ), filtered, and evaporated at reduced pressure to provide 92 g (89%
4
yield) of the title compound as a pale yellow liquid. The product was suffi-
ciently pure to use in the subsequent reaction. The crude product can be dis-
tilled at reduced pressure, residual pyridine comes over at 758C 1 mm Hg,
product distills at 1258C 1 mm Hg to obtain a colorless liquid. NMR dH
(
CDCl ) 7.29–7.17 (m, 2H), 6.78–6.64 (m, 3H), 4.24 (t, J ¼ 6.6 Hz, 2H),
3
3
.56 (t, J ¼ 6.6 Hz, 2H), 3.41 (q, J ¼ 7.0 Hz, 2H), 2.06 (s, 3H), 1.18
C 3
(
t, J ¼ 6.9 Hz, 3H); d (CDCl ) 170.89, 147.62, 129.36, 116.24, 112.01,
1
03.51, 61.71, 48.82, 45.21, 20.85, 12.25.
4
-Formyl-N-ethyl-N-(2-acetoxyethyl)-aniline (3)
To 200 mL anhydrous DMF (188.8 g, 2.58 mol, 5.34 equiv) at room temp-
erature was added drop-wise 110 mL POCl (181.5 g, 1.18 mol, 2.44 equiv) and
3
then the mixture was stirred for 1.5 hr. Next, 100 g 2 (483 mmol) dissolved in
250 mL of 1,2-dichloroethane was added drop-wise, then the mixture was
stirred and heated at 858C for 8 hr. The reaction mixture was cooled to room
temperature and poured into 2 L H O and stirred 2 hr then neutralized with a satu-
rated aqueous K CO . The solution was extracted with CHCl (3 ꢁ 600 mL).
2
2
3
3
The combined extracts were washed with H O (5 ꢁ 500 mL), dried (MgSO ),
2
4
and evaporated to yield 95 g of the title compound as a yellow oil (84%). The
product was sufficiently pure to use in the subsequent reaction. NMR dH
(
CDCl3) 9.67 (s, 1H), 7.65 (d, J ¼ 9.0 Hz, 2H), 6.68 (d, J ¼ 9.0 Hz, 2H), 4.19
t, J ¼ 6.3 Hz, 2H), 3.58 (t, J ¼ 6.3 Hz, 2H), 3.42 (q, J ¼ 7.2 Hz, 2H), 1.97
s, 3H), 1.15 (t, J ¼ 7.2 Hz, 3H); d (CDCl ) 190.10, 170.89, 152.38, 132.24,
(
(
C
3
1
25.49, 111.05, 61.23, 48.70, 45.59, 20.89, 12.15.
3
-[4-[N-Ethyl-N-(2-hydroxyethyl)amino]styryl]-
,5-dimethylcyclohex-2-enone (4)
5
To a mixture of 50 g 3 (213 mmol), 71.3 g isophorone (512 mmol, 2.4
equiv), 330 g 25 wt% cetyltrimethylammonium chloride in H O (258 mmol,
2

3
424
Davis et al.
1
.2 equiv) was added in one portion a solution of 17 g NaOH in 1.7 L H O
2
(
2 equiv). This mixture was then magnetically stirred and heated to 608C for
6 hr. After 48 hr a yellowish oil had separated from the mixture. Then 2 L
ice water was poured into the reaction followed by 17.6 mL conc. HCl
1 equiv), and any excess acid was neutralized by addition of sodium bicar-
9
(
bonate. After stirring 2 d the yellow precipitated product was filtered, washed
with H O, and suction dried (32 g, 48%). The product was sufficiently pure to
2
use in the subsequent reaction. m.p. 958C (shrinks) 107–1108C; NMR dH
(
CDCl ) 7.33 (d, J ¼ 8.9 Hz, 2H), 6.76 (AB quart, 2H), 6.68 (d, J ¼ 8.5 Hz,
3
2
2
H), 5.95 (s, 1H), 3.85–3.73 (m, 2H), 3.52–3.36 (overlapping q and t, 4H),
.41 (s, 2H), 2.24 (s, 2H), 1.81 (bs, OH), 1.15 (t, J ¼ 7 Hz, 3H), 1.05 (s, 6H);
d (CDCl ) 200.49, 156.36, 149.16, 135.77, 129.15, 125.09, 124.82, 124.12,
C
3
1
12.27, 60.25, 52.50, 51.56, 45.69, 39.29, 33.45, 28.70, 12.19.
3
-[4-[N-Ethyl-N-(2-tert-butyldimethylsiloxyethyl)amino]-
styryl]-5,5-dimethylcyclohex-2-enone (5)
To a solution of 9.27 g 4 (29.6 mmol) and 5.37 g tert-butyldimethylsilyl
chloride (35.5 mmol, 1.2 equiv) in 60 mL anhydrous DMF was added 2.43 g
imidazole (35.6 mmol, 1.2 equiv), and the reaction was stirred overnight at
room temperature. The reaction was then poured into 500 mL ice water and
extracted with Et O (3 ꢁ 150 mL). The extracts were collected, washed
2
with dilute Na CO , followed by a wash with brine. The extracts were then
2
3
dried (MgSO ), filtered, and evaporated. The resulting oil was heated at
4
40 C8 for 18 hr under vacuum (0.1 mm Hg) to provide 11.76 g (93%) of the
title compound as a viscous red oil. The product was sufficiently pure to
use in the subsequent reaction. NMR (CDCl ) 7.36 (d, J ¼ 8.9 Hz, 2H),
3
6
.99–6.60 (m, 4H), 6.00 (s, 1H), 3.77 (t, J ¼ 6.1 Hz, 2H), 3.53–3.37
(
m, 4H), 2.46 (s, 2H), 2.89 (s, 2H), 1.18 (t, J ¼ 6.9 Hz, 3H), 1.10 (s, 6H),
0
1
3
.89 (s, 9H), 0.37 (s, 6H); dC (CDCl ) 200.09, 156.10, 148.83, 135.74,
3
29.08, 124.97, 124.40, 123.49, 111.67, 60.72, 52.51, 51.56, 45.64, 39.20,
3.38, 28.65, 26.02, 18.37, 12.32, 25.24.
2EZ-[3-[(1E)-2-[4-[N-Ethyl-N-(2-tert-
butyldimethylsiloxyethyl)amino]phenyl]-ethenyl]-5,5-
dimethyl-2-cyclohexen-1-ylidene]-acetaldehyde (6a(Z),6b(E))
To 400 mL dry Et O under N in a 3-L three-neck flask, cooled in an ice
2
2
bath, was added 141 mL 2M lithium diisopropylamide solution (282 mmol,
.5 equiv). Then 33 g N-cyclohexyl-acetimine (263 mmol, 1.4 equiv) was
1

Synthesis of Isophorone-Based Nonlinear Optical Chromophore
3425
added drop-wise, and the solution was stirred for 30 min 08C. Then the
mixture was cooled to 2788C and an addition funnel with a solution of
8
0.36 g 5 (188 mmol) in 200 mL Et O was equipped to the flask. The addition
2
was made in a gentle stream over a period of 30 min. Then the 2788C bath
was removed and the flask allowed to warm to room temperature and
stirred for 8 hr. The color of the reaction appears dark-greenish during the
addition of the ketone and then becomes red-orange after stirring at room temp-
erature. Then the reaction was cooled in an ice bath before 16.2 mL glacial
HOAc (282 mmol, 1 equiv relative to lithium amide) was added drop-wise,
resulting in a cloudy tomato-orange mixture. Then 26 g oxalic acid
(295 mmol) dissolved in 400 mL H O was added to the reaction and the
mixture was vigorously stirred for 8 hr. The deep-red Et O was separated
2
2
and the aqueous phase extracted again (2 ꢁ 200 mL) with Et O. The extracts
2
were combined, dried (MgSO ), and rotary evaporated (10 mm Hg, 408C),
4
leaving a viscous red oil. This oil was dry-column chromatographed (SiO2;
hexanes : EtOAc : MeOH; 9 : 0.8 : 0.2) to provide the title compounds as a red
glass (51 g, 60%) as well as some remaining starting ketone. The ratio of the
geometric isomers is 68% Z and 32% E found by integration of their respective
aldehydic proton resonances. NMR d (CDCl ) 10.18 (d, J ¼ 8.2 Hz, 1H, Z),
H
3
9
7
2
1
1
1
4
1
.99 (d, J ¼ 8.2 Hz, E), 7.30 (d, J ¼ 8.9 Hz, 2H), 7.29 (d, J ¼ 8.5 Hz, 2H),
.14 (s, 1H, E), 6.23 (s, 1H, Z), 5.87 (d, J ¼ 8.6 Hz, 1H), 2.64 (d, J ¼ 1.2 Hz,
H, E), 2.31 (s, 2H), 2.25 (s, 2H Z), 1.39 (s, 6H), 1.19 (t, J ¼ 7.1 Hz, 3H),
.02 (s, 6H, E), 0.99 (s, 6H, Z), 0.85 (s, 9H); d (CDCl ) 190.63, 189.69,
57.18, 156.79, 148.39, 146.90, 146.77, 132.69, 132.58, 128.58, 127.85,
26.17, 125.93, 125.66, 124.20, 124.16, 120.59, 111.77, 60.77, 52.57, 46.45,
5.67, 39.64, 39.33, 39.06, 31.32, 31.21, 28.55, 28.40, 26.07, 18.44,
2.39, 25.27.
C
3
2EZ-[3-[(1E)-2-[4-[N-Ethyl-N-(2-
hydroxyethyl)amino]phenyl]-ethenyl]-5,5-dimethyl-2-
cyclohexen-1-ylidene]-acetaldehyde (7a(Z),7b(E))
To a magnetically stirred solution of 81 g 6a,6b (179 mmol) in 1 L MeCN
was added 29 g triethylamine trihydrofluoride (1 equiv), and the solution was
stirred at 408C for 2 hr. At this time thin-layer chromatography analysis
showed no starting material remained. The MeCN was removed by rotary
evaporation (10 mm Hg, 408C) and the dark residue was partitioned
between 600 mL CH Cl and 200 mL H O. The organic phase was separated,
2
2
2
dried (MgSO ), and rotary evaporated (10 mm Hg, 408C). The resulting oil
4
was dry-column chromatographed (SiO ; hexanes : EtOAc) to provide the
title compounds as a deep-red oil (59.2 g, 97%). The ratio of the geometric
2

3
426
Davis et al.
isomers is 67% E: 33% Z found by integration of their respective aldehydic
proton resonances. NMR dH (CDCl ) 10.21 (d, J ¼ 7.9 Hz, Z), 10.05 (d,
3
J ¼ 8.6 Hz, E), 7.36 (d, J ¼ 9.1 Hz, 2H, Z), 7.35 (d, J ¼ 9.1 Hz, 2H, E),
7
.19 (s, 1H, E), 6.79–6.68 (m, 4H), 6.28 (s, 1H, E), 5.91 (d, J ¼ 8.4 Hz, E),
.71 (d, J ¼ 9.1 Hz, Z), 3.82 (t, J ¼ 5.5, 2H), 3.57–3.40 (m, 4H), 2.68
5
(
d, J ¼ 1.3 Hz, 2H, E), 2.35 (s, 2H), 2.29 (d, J ¼ 1.3 Hz, 2H, Z), 1.19
(
t, J ¼ 7 Hz, 3H), 1.06 (s, 6H, E), 1.03 (s, 6H, Z); d (CDCl ) 190.87,
C
3
1
1
5
89.91, 157.47, 157.11, 148.64, 146.97, 146.78, 132.56, 132.47, 128.61,
28.09, 126.36, 126.25, 126.08, 124.89, 124.23, 120.79, 112.41, 60.32,
2.51, 46.46, 45.70, 39.63, 39.36, 39.05, 31.34, 31.23, 28.54, 28.42, 12.18.
Elemental analysis calculated for C H NO : C, 77.83; H, 8.62; N, 4.13.
2
2
29
2
Found: C, 77.27; H, 8.77; N, 4.11.
2
-Dicyanomethylene-3-cyano-4,5,5-trimethyl
2,5-dihydrofuran (8)
-
To 900 mg of sodium ethoxide (13 mmol, 0.15 equiv) dissolved in 10 mL
of absolute EtOH in a room temperature water bath was added 9 g 3-hydroxy-
3
-methyl-2-butanone (88 mmol) and 12 g freshly distilled malononitrile
181 mmol, 2.05 equiv) with stirring. After 1 hr 30 mL of absolute EtOH
(
was added and heated at reflux for 1 additional hr. This is cooled in a refri-
gerator and the solid filter, washed with a minimal amount of cold EtOH,
and then air dryed giving a first crop of 11.6 g of off-white crystalline solid
(
65% yield). Concentration of the filtrate and cooling gave a second crop of
0
2
1
.48 g product (total yield 68%). m.p. 1998C–2008C; NMR dH (CDCl3)
.36 (s, 3H), 1.64 (s, 6H); d (DMSO-d ) 185.59, 177.09, 112.04, 111.32,
09.79, 103.52, 101.17, 54.73, 23.09, 14.06.
C
6
[4-[(1E,3EZ)-3-[3-[(1E)-2-[4-[N-Ethyl-N-(2-
hydroxyethyl)amino]phenyl]-ethenyl]-5,5-dimethyl-2-
cyclohexen-1-ylidene]-1-propenyl]-3-cyano-5,5-dimethyl-
2
(5H)-furanylidene]-propanedinitrile (9a(Z),9b(E))
A solution of 5.21 g 7a,7b (15.37 mmol) and 3.06 g 8 (1 equiv) in 150 mL
CH Cl under N was cooled to 08C with magnetic stirring in the dark. Then
2
2
2
2
.23 g piperidinium acetate (1 equiv) was added in a single portion to the dark-
orange solution and the cooling bath was removed. The mixture immediately
became dark with a viscous appearance. After 3 hr, thin-layer chromatography
(
SiO ; hexanes/EtOAc) showed no starting material remained. Water (50 mL)
2

Synthesis of Isophorone-Based Nonlinear Optical Chromophore
3427
was added and a portion of the product precipitated. The entire mixture was
filtered through a medium-porosity glass frit, leaving an initial crop of the
product as a fine-green crystalline powder. The solid was washed with
water, anhydrous acetone and then placed under high vacuum (0.1 mm Hg).
The CH Cl /water mixture was poured into a separatory funnel. After separ-
2
2
ating the organic layer, it was washed with saturated aqueous NaHCO3
followed by brine. The organic phase was collected, dried (MgSO ), and
4
rotary-evaporated (10 mm Hg, 408C) to leave a dark-purple, brittle solid.
The solid was broken up and slurried at room temperature for 2 hr with
1
00 mL anhydrous acetone, then filtered to leave the title second crop of
title compound as a dark-green, crystalline powder, which was then place
under high vacuum (0.1 mm Hg) for several hours. Both crops of product
were combined after spectroscopy showed them to be identical (6.7 g total,
8
5% yield). The ratio of the geometric isomers is 75% E: 25% Z found by
E
Z
NMR integration (of H or H , see Fig. 1). m.p. 231–2348C; NMR d
H
Z
(
CDCl ) 8.29 (dd, J ¼ 14.8 and 11.6 Hz, Z, H ), 7.99 (dd, J ¼ 14.8 and
3
E
1
1.6 Hz, E, H ), 7.37 (d, J ¼ 8.9 Hz, 2H), 6.85–6.77 (m, 2H), 6.73
(
(
(
d, J ¼ 8.9 Hz, 2H), 6.39–6.05 (m, 3H), 3.84 (t, J ¼ 5.5 Hz, 2H), 3.53
t, J ¼ 5.7 Hz, 2H), 3.49 (q, J ¼ 7 Hz, 2H), 2.47–2.32 (m, 4H), 1.72–1.66
m, 6H), 1.58 (bs, 1H, OH), 1.20 (t, J ¼ 7.0 Hz, 3H), 1.08–1.01 (m, 6H);
d
1
1
1
3
(CD Cl ) 176.99, 174.57, 174.12, 155.85, 155.29, 149.62, 149.33,
2 2
C
48.59, 144.63, 143.70, 134.46, 130.16, 129.43, 129.38, 128.36, 126.58,
26.43, 126.06, 125.16, 122.57, 116.19, 115.57, 113.30, 112.78, 112.65,
12.49, 97.75, 97.69, 94.69, 60.75, 55.04, 52.91, 47.49, 46.11, 40.37, 40.15,
9.93, 32.08, 31.85, 28.67, 28.47, 26.89, 12.40. Ignoring residual CH Cl ,
2
2
1
quantitative H NMR and HPLC analyses indicated purities of .98%
.
and 99.2%, respectively. Elemental analysis calculated for C H N O 0.15-
3
3 36 4 2
CH Cl (the title compounds cocrystallize with CH Cl ): C, 74.59; H, 6.81;
2
2
2
2
N, 10.5. Found: C, 74.34; H, 6.90; N, 10.46. After 2 months, elemental analy-
sis of this product showed that the CH Cl completely evaporated from the
2
2
crystals after storage at ambient conditions (theory: C, 74.59; H, 6.81; N,
0.5; found: C, 74.34; H, 7.10; N, 10.42).
1
ACKNOWLEDGMENT
Financial support from the Office of Naval Research is gratefully
acknowledged. We thank Dr. Peter V. Bedworth, Lockheed Martin Advanced
Technological Center, for valuable suggestions regarding the synthesis of
this class of compounds. We thank Dr. Geoffrey A. Lindsay, NAWCWD,
for advice and encouragement throughout the course of this work. And

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Davis et al.
we thank Mrs. Ruth Ann E. McIntire, NAWCWD, for assistance in the
preparation of this manuscript.
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Received in the USA June 2, 2004