The reaction of Wittig and Wittig-Horner reagents and alkyl phosphites with 1,2-naphthoquinone-1-benzimide

Article abstract of DOI:10.1007/PL00010273

Carbomethoxymethylene and carbethoxymethylene triphenylphosphoranes (Ia, b) react with 1,2-naphthoquinone-1-benzimide (8) to give the corresponding 1-benzoylimino-IH-naphthalen-2-ylidcne-acetic esters 9a,b and 2-(1-benzoylamino-naphthalen-2-yl)-but-2-ened

Full text of DOI:10.1007/PL00010273

Monatshefte fuÈr Chemie 130, 921±928 (1999)
The Reaction of Wittig and Wittig-Horner
Reagents and Alkyl Phosphites with 1,2-
Naphthoquinone-1-benzimide
Mona H. N. Arsanious
National Research Centre, Dokki, Cairo, Egypt
Summary. Carbomethoxymethylene and carbethoxymethylene triphenylphosphoranes (1a, b) react
with 1,2-naphthoquinone-1-benzimide (8) to give the corresponding 1-benzoylimino-1H-naphthalen-
2-ylidene-acetic esters 9a,b and 2-(1-benzoylamino-naphthalen-2-yl)-but-2-enedioic esters 10a,b
together with 1-benzamido-2-naphthol (11). Application of Wittig-Horner reagents 4a,b on 8 at
room temperature and in the presence of alcoholic sodium alkoxide renders 2-(1-benzoylamino-
naphthalen-2-yl)-3-phosphonylsuccinic esters 12a,b. Conducting the reaction in re¯uxing toluene
and in the presence of sodium hydride led to the formation of 2-benzamido-naphthol-1-ethyl ether
(13). 1-Benzamido-2-naphthol (11) was also isolated from both reaction media. Trimethyl and
dimethyl phosphites (7a,b) react with 8 to 14 as the sole product. Mechanisms accounting for the
formation of the new products are discussed, and the probable structures of the products are
presented based on analytical and spectroscopic data.
Keywords. Wittig; Wittig-Horner; Phosphites; Naphthoquinone; Naphthalene; Naphthoxazol
derivative.
Reaktionen von Wittig- und Wittig-Horner-Reagenzien sowie Alkylphosphiten mit
1,2-Naphthochinon-1-benzimid
Zusammenfassung. Carbomethoxymethylen- und Carbethoxymethylen-triphenylphosphorane
(1a,b) reagieren mit 1,2-Naphthochinon-1-benzimid (8) zu den entsprechenden 1-Benzoylimino-
È
1H-naphthalin-2-yliden-essigsaureestern 9a,b und zu den 2-(1-Benzoylamino-naphthalin-2-yl)-but-
2-endionestern 10a,b sowie zu 1-Benzamido-2-naphthol (11). Einwirkung der Wittig-Horner-
Reagenzien 4a,b auf 8 bei Raumtemperatur in Gegenwart von alkoholischem Natriumalkoxid ergibt
È
È
die 2-(1-Benzoylamino-naphthalin-2-yl)-3-phosphonyl-bernsteinsaureester 12a,b. Durchfuhrung der
Reaktion in Toluol am RuÈck¯uû in Gegenwart von Natriumhydrid fuÈhrte zur Bildung von
2-Benzamido-naphthol-1-ethylether (13). Aus derselben Reaktionsmischung konnte auch 1-Benza-
mido-2-naphthol (11) isoliert werden. Tri- und Dimethylphosphite (7a,b) reagieren mit 8 zu 14 als
einzigem Produkt. Mechanismen, die zur Bildung der neuen Verbindungen fuÈhren, werden
diskutiert, und die nach analytischen und spektroskopischen Befunden wahrscheinlichen Strukturen
werden vorgestellt.

922
M. H. N. Arsanious
Introduction
More than a decade ago, we have reported that Wittig reagents (1) react with
o-quinone diimines (2) to the corresponding ylide-phosphorane adducts 3 [1].
Moreover, it is known that Wittig-Horner reagents (4) give phosphonate adducts 5
and the alkylated product 6 when reacted with 2 (Scheme 1) [2]. As a continuation
of our work on the behavior of organophosphorus reagents towards quinone imines
[3±6], we have now investigated the action of phosphonium ylides, phosphonate
anions 4 and alkyl phosphites 7 on 1,2-naphthoquinone-1-benzimide (8). The
purpose of this study was to determine the preferential site of attack by these
reagents and to produce new phosphorane adducts.
Scheme 1
Results and Discussion
When 1,2-naphthoquinone-1-benzimide (8) was treated with one equivalent of
carbomethoxymethylene triphenylphosphorane (1a) in absolute benzene at room
temperature for 8 hours, adducts 9a and 10a, 1-benzamido-2-naphthol (11),
triphenylphosphine, and triphenylphosphine oxide were isolated. Carrying out the
reaction using two mol of phosphonium ylide 1a instead of one lead to the
formation of compounds 9a, 10a, and 11 in good yields (Scheme 2). In many
addition reactions of quinoneimines, reduction occurred at varying degree in the
presence of reagents which are normally not considered to have reducing properties
[7, 8]. It has also been observed that better yields are obtained when the reaction is
carried out in a 1:3 molar ratio.

Wittig Reactions of 1,2-Naphthoquinone-1-benzimide
923
Scheme 2
Compound 9a was chromatographically pure and exhibited a sharp melting
point. The IR spectrum of 9a revealed the presence of strong absorption bands at
1
1586 (C=N), 1736 (CO, ester), and 1617 (C=C, Ar)cmꢀ1 [9]. The H NMR
spectrum of 9a consisted of signals at 3.70 (s, 3H, COOCH3), 6.12 (s, 1H, =CH),
7.38, 7.72 (J ˆ 8 Hz), 7.79, 8.34, 8.80, and 7.49±7.60 (arom.H) ppm. The 13C NMR
spectrum of 9a showed signals ± among others ± at 123.5 (=CH), 156.9 (COOCH3),
‡
169.2 (COPh), and 134.4 (C=N) ppm. The mass spectrum of 9a had its M peak at
m/z ˆ 317, thus supporting the proposed structure.
The structure of the other isolated compound (10a) was deduced from its
analytical, IR, H NMR, and mass spectroscopic data. Elemental and mass
1
spectroscopic data of 10a pointed to an emperical formula of C23H19NO5. Its IR
spectrum (KBr) revealed the presence of strong NH absorption band at 3200 cmꢀ1.
The carbonyl and C=N absorption bands appearing in the IR spectrum of 8 at 1656
1
and 1586 cmꢀ1, respectively, are lacking. The H NMR spectrum of 10a showed
signals at 3.72 (s, 3H, COOCH3), 3.82 (s, 3H, COOCH3), 6.30 (s, 1H, =CH), 8.72
(s, 1H, NH), 7.38 (d, 1H, J ˆ 8 Hz), 7.76±7.94 (m, 4H, aromatic), 7.51±7.56 (m,
5H, COPh), and 8.02 (dd, 1H, J ˆ 8 and 1.6 Hz) ppm. The 13C NMR spectrum of
10a exhibits resonances at 132.5 (C=CH), 124.6 (C=CH), 167.2, 65.4 (COOCH3)
‡
and 170.5 (COPh) ppm. The mass spectrum of 10a yielded an M peak of m/z ˆ 389
(96%).
A possible explanation for the course of the reaction of the phosphonium ylides
1a,b with 8 is shown in Scheme 2. Formation of adducts 9a,b can be explained in

924
M. H. N. Arsanious
terms of carbonyl ole®nation [10] of 8 by the Wittig reagents 1a,b with expulsion
of triphenyl phosphine oxide. Another molecule of 9a,b reacts with phosphonium
ylide to give adducts 10a,b.
Similarly, carbethoxymethylenetriphenyl phosphorane (1b) reacts with 1,2-
naphthoquinone-1-benzimide (8) in benzene at room temperature (10 hours) to
give chromatographically pure adducts 9b and 10b, triphenylphosphine, triphe-
nylphosphine oxide, and the reduced form of 8. On the basis of spectroscopic and
analytical data the structures of 9b and 10b were deduced (cf. Experimental).
This study was further extended to include the reaction of Wittig-Horner
reagents 4a,b with quinone monoimine 8 to test whether it would behave in a
similar manner. We have found that the reaction of 8 with two molar equivalents of
methyl dimethyl phosphonoacetate 4a in the presence of alcoholic sodium
methoxide solution proceeds at room temperature to give adduct 12a and the
corresponding amide 11 (Scheme 3). The structure of 12a is based on the analytical
and spectroscopic evidences given in the Experimental, including 31P NMR
spectroscopy [11, 12].
Similarly, triethyl phosphonoacetate 4b reacts with quinone 8 at room
temperature in the presence of sodium ethoxide to give colorless a product which
was assigned structure 12b (Scheme 3).
When 8 was allowed to react with one equivalent of the carbanion reagents 4 in
re¯uxing toluene and in the presence of sodium hydride [13], the alkylated adduct
13 was isolated together with 1-benzamido-2-naphthol (11). The spectroscopic
data of compound 13 were in good agreement with the proposed structure (cf.
Experimental).
The reaction of 8 with alkyl phosphites was also investigated. We have found
that reaction with trimethyl and/or dimethyl phosphite in dry benzene at room
temperature gave naphthoxazol 14 as the sole product [14].
Scheme 3

Wittig Reactions of 1,2-Naphthoquinone-1-benzimide
925
Scheme 4
From the results of the present investigation it can be concluded that the
reaction of 8 with phosphonium ylides 1, phosphonate anions 4, and alkyl
phosphites 7 leads to different products, depending on the nature of the phosphorus
reagents as well as on the stability of the addition products. The signi®cance of
these ®ndings lies in the discovery of a new pattern of Wittig reagents and in the
establishment of a novel method for the synthesis of new phosphonate products
using Wittig-Horner reagents. It is noteworthy that 8 behaves towards alkyl
phosphites in a manner different from that of Wittig and Wittig-Horner reagents.
Experimental
All melting points are uncorrected. Benzene (thiophene-free) and petroleum ether (60±80ꢁC) were
dried over sodium. Carbomethoxymethylene and carbethoxymethylene triphenylphosphoranes were
prepared according to established methods [15]. Trimethyl and triethyl phosphonoacetates were
prepared by Michaelis-Arbuzov reactions [16, 17]. Alkyl phosphites were prepared according to
known procedures and puri®ed by fractional distillation [18, 19]. The IR spectra were measured in
1
KBr pellets on a Perkin-Elmer Infracord spectrophotometer Model 157 (Grating). The H and 13C
NMR spectra were recorded in CDCl3 on a Varian NMR spectrometer at 200 and 50 MHz,
respectively, using TMS as internal standard. The 13P NMR spectra were recorded in CDCl3 with a
JNM-PS-100Fa spectrometer at 81 MHz (ꢀ relative to external 85% H3PO4). The mass spectra were
run at 70 eV using Kratos MS equipment and/or a Varian MAT 311 A Spectrometer.

926
M. H. N. Arsanious
Reaction of phosphoranes 1a,b with 1,2-naphthoquinone-1-benzimide (8)
To a solution of 8 (0.26 g, 0.001 mol) [20] in dry benzene (20 cm3), a solution of 1a (0.99 g, 0.03 mol)
in benzene was added and the reaction mixture was left at room temperature under stirring for 8 h.
The volatile materials were evaporated under reduced pressure, and the residual substance was
chromatographed on a silica gel column using ethyl acetate/petroleum ether (5:95 v/v) as eluent to
give 9a as pale yellow crystals.
Yield: 55%; m.p.: 135±136ꢁC; C20H15NO3 (317.34); calcd.: C 75.70, H 4.76, N 4.41; found: C
75.67, H 4.70, N 4.43; 1H NMR: ꢀ ˆ 3.70 (s, 3H, COOCH3), 6.12 (s, 1H, =CH), 7.38 (d, 1H,
J ˆ 8 Hz), 7.72 (dd, 1H, J ˆ 8 Hz, 1.6 Hz), 7.79, 8.34, 8.80, 7.79±7.60 (arom. H) ppm; 13C NMR:
ꢀ ˆ 123.5 (=CH), 156.9 (COOCH3), 169.2 (COPh), 54.0 (CH3), 139.4 ppm; (C-1), 132.5 (C-2),
122.8 (C-3), 126.5 (C-4), 128.2, 126.7, 127.5, 128.7, 115.1, 128.9 (C6H4), 134.4, 129.5, 128.9, 132.3
‡
(C6H5) ppm; MS: m/z(%) ˆ 317 (M , 100), 266 (35); IR: ꢁ~ˆ 1586 (C=N), 1736 (C=O, ester), 1617
(C=C, Ar) cmꢀ1
.
Adduct 10a was separated (25:75) as colorless crystals; yield: 25%; m.p.: 206ꢁC; C23H19NO5
(389.41); calcd.: C 70.94, H 4.92, N 3.60; found: C 70.90, H 4.89, N 3.57; 1H NMR: ꢀ ˆ 3.72 (s, 3H,
COOCH3), 3.82 (s, 3H, COOCH3), 6.30 (s, 1H, =CH), 8.72 (s, 1H, NH), 7.38 (d, 1H, J ˆ 8 Hz),
7.76±7.94 (m, 4H, aromatic), 7.51±7.56 (m, 5H, COPh), 8.02 (dd, 1H, J ˆ 8 Hz, 1.6 Hz) ppm; 13C
NMR ꢀ ˆ 132.5 (C=CH), 124.6 (C=CH), 53.4 (CH3), 52.5 (CH3), 167.2 (CO, ester), 165.4 (CO,
ester), 170.5 (COPh), 134.3 (C-1), 128.8 (C-2), 127.7 (C-3), 124.9 (C-4), 128.1, 126.5, 126.4, 128.4,
‡
129.3, 134.2 (C6H4), 135.1, 130.3, 128.1, 132.7 (C6H5) ppm; MS: m/z(%) ˆ 389 (M , 100), 358 (35)
285 (55), 105 (90); IR: ꢁ~ˆ 1635 (C=O, ester), 1616 (C=C, Ar), 3200 (NH) cmꢀ1
.
Compound 11 was also isolated (10%) and proved to be the corresponding amide (mixed m.p.
and comparative IR spectra) [21]. Triphenylphosphine and triphenyl phosphine oxide were isolated
and identi®ed (mixed m.p. and comparative IR spectra).
Similarly, carbethoxymethylene triphenylphosphorane (1b) reacts with 8 in dry benzene at room
temperature for 10 h to give compound 9b (eluent: ethyl acetate/petroleum ether 10:90 (v/v)) as pale
yellow crystals.
Yield: 60%; m.p.: 112±113ꢁC; C21H17NO3 (331.371): calcd.: C 76.12, H 5.17, N 4.23; found: C
1
76.09, H 5.14, N 4.20; H NMR: ꢀ ˆ 1.20 (t, 3H, ethoxy-CH3), 4.20 (q, 2H, ethoxy-CH2), 6.15 (s,
1H, =CH), 7.41 (d, 1H, J ˆ 8 Hz), 7.71 (d, 1H, J ˆ 8 Hz, 1.6 Hz), 7.85 (br, 1H, aromatic), 7.51±7.62
(m, 5H, COPh), 8.36 (2H, aromatic), 8.81 (br, 1H, aromatic) ppm; 13C NMR: ꢀ ˆ 156.4 (CO, ester),
169.0 (COPh), 123.8 (=CH), 61.5 (OCH2CH3), 13.9 (OCH2CH3), 139.8 (C-1), 132.3 (C-2), 122.7
(C-3), 123.5 (C-4), 128.5, 126.7, 127.3, 126.4, 115.3, 128.9 (C6H4), 134.3, 129.3, 128.9, 131.6
(C6H5) ppm; IR: ꢁ~ˆ 1580 (C=N), 1740 (C=O, ester), 1617 (C=C, Ar) cmꢀ1; MS: m/z(%) ˆ 331
‡
(M , 55), 258 (100), 127 (40).
Compound 10b: eluent as above (15:85, v/v); colorless crystals; yield: 20%; m.p..: 172±173ꢁC;
C25H23NO5 (417.46); calcd.: C 71.93, H 5.55, N 3.36; found: C 71.90, H 5.50, N 3.33%; 1H NMR:
ꢀ ˆ 1.24 (t, 3H, CH3, J ˆ 7.2 Hz), 1.18 (t, 3H, CH3, J ˆ 7.2 Hz), 4.22 (m, 4H, 2(CH2)), 6.25 (s, 1H,
=CH), 8.73 (s, 1H, NH), 7.45 (d, 1H, J ˆ 8 Hz), 7.85±7.94 (m, 4H, aromatic), 7.51±7.56 (m, 5H,
COPh), 8.04 (dd, 1H, J ˆ 8 Hz, 1.6 Hz) ppm; 13C NMR: ꢀ ˆ 62.6, 61.4 (2(CH2)), 13.1 (CH3), 14.2
(CH3), 168.2 (CO, ester), 169.4 ppm (CO, ester), 123.7 (C=CH), 170.2 (COPh), 134.8 (C-1), 128.3
(C-2), 127.9 (C-3), 125.2 (C-4), 128.1, 126.5, 126.4, 128.4, 129.3, 133.2 (C6H4), 135.3, 130.3, 128.2,
‡
132.1 (C6H5) ppm; MS: m/z(%) ˆ 417 (M , 50), 312 (20), 372 (15), 193 (22); IR: ꢁ~ˆ 3250 (NH),
1730 (C=O, ester), 1745 (C=O, ester), 1600 (C=C, Ar) cmꢀ1
.
Reaction of phonoacetates 4a,b with 1,2-naphthoquinone-1-benzimide (8)
A solution of 2 mol of sodium methoxide in absolute methanol was treated with an equimolar
amount of phosphonoacetate anion 4a (0.42 g, 002 mol). After 5 min, 1 mol of 8 (0.26 g, 0.001 mol)
was added, and the resulting mixture was stirred at room temperature for 4 h. The reaction mixture

Wittig Reactions of 1,2-Naphthoquinone-1-benzimide
927
was extracted with ethyl acetate, and the extracts were evaporated under reduced pressure. The
residue was subjected to silica gel column chromatography using ethyl acetate/petroleum ether
(70:30 (v/v)) as eluent to give compound 12a as colorless crystals (cyclohexane).
Yield: 50%; m.p.: 123±124ꢁC; C25H26NO8P (499.46); calcd.: C 60.12, H 5.25, N 2.80, P 6.20;
found: C 60.08, H 5.23, N 2.82, P 6.18; 1H NMR: ꢀ ˆ 3.68 (s, 3H, OCH3), 3.71 (s, 3H, OCH3), 2.97
(dd, 1H, JHP ˆ 12 Hz, JHH ˆ 7.5 Hz), 3.13 (dd, 1H, JHP ˆ 10 Hz, JHH ˆ 7.5 Hz), 3.74, 3.82 (2s, 6H,
2COOCH3), 7.18 (d, 1H, J ˆ 8 Hz), 7.43±7.65 (m, 5H, COPh), 7.76±7.88 (m, 4H, aromatic), 8.04
(dd, 1H, J ˆ 8 Hz, 1.6 Hz), 8.75 (s, 1H, NH) ppm; 13C NMR: ꢀ ˆ 167.5, 165.0 (2(COOCH3)), 50.4,
1
2
52.3 (2(COOCH3)), 45.3 (d, JCP ˆ 140 Hz, HC-P(O)), 53.1, 55.1 (2d, JPC ˆ 7.0 Hz,
31
O ˆ P(OCH3)2) ppm; P NMR: ꢀ ˆ 20.7 ppm; MS: m/z(%) ˆ 499 (M , 12), 390 (20), 331 (18);
‡
IR: ꢁ~ˆ 3290 (NH), 1230 (P=O), 1056 (P±OCH3) cmꢀ1
.
Similarly, the anion of triethylphosphonoacetate 4b reacts with 8 in absolute ethanol to give
colorless adduct 12b, (acetone: petroleum ether, 70:30 (v/v)); yield: 60%; m.p.: 125±126ꢁC;
C29H34NO8P (555.56); calcd.: C 62.70, H 6.16, N 2.52, P 5.58; found: C 62.68, H 6.12, N 2.50, P
1
5.54; H NMR: ꢀ ˆ 1.15, 1.28 (2t, 6H, O=P(OCH2CH3)2), 0.85 (t, 3H, COOCH2CH3), 1.45 (t, 3H,
COOCH2CH3), 3.60 (dd, 1H, JHP ˆ 12 Hz, JHH ˆ 7.5 Hz), 3.73 (dd, 1H, JHP ˆ 10 Hz, JHH ˆ 7.5 Hz),
4.42 (m, 4H, P(OCH2CH3)), 4.20 (m, 4H, 2(COOCH2CH3)), 8.50 (s, 1H, NH), 7.05 (d, 1H,
J ˆ 8 Hz), 7.43±7.62 (m, 5H, COPh), 7.72±7.87 (m, 4H, aromatic), 8.09 (dd, 1H, J ˆ 8 Hz,
31
‡
1.6 Hz) ppm; P NMR: ꢀ ˆ 21.02 ppm; MS: m/z(%) ˆ 555 (M , 10), 465 (12), 328 (16), 246 (30);
IR: ꢁ~ˆ 3200 (NH), 1235 (P=O), 1752 (C=O, ester), 1740 (C=O, ester), 1620 (C=C, Ar) cmꢀ1
.
The reaction of 4b (0.001 mol) with 8 (0.001 mol) in re¯uxing toluene using sodium hydride
(0.001 mol) as a base instead of sodium ethoxide gave rise to the corresponding alkylated product 13
as colorless crystals; yield: 60%; m.p.: 220-221ꢁC; C19H17NO2 (291.35); calcd.: C 78.33, H 5.88, N
4.81; found: C 78.30, H 5.84, N 4.78; 1H NMR: ꢀ ˆ 1.47 (t, 3H, OCH2CH3 J ˆ 7.2 Hz), 4.75 (q, 2H,
OCH2CH3, J ˆ 7.2 Hz), 7.48±7.73 (m, 5H, CO, Ph), 7.81±7.84 (m, 6H, aromatic), 8.80 (s, 1H,
NH) ppm; 13C NMR: ꢀ ˆ 169.7 (COPh), 67.9 (CH2), 14.9 (CH3), 124.6 (C-1), 150.4 (C-2), 112.6 (C-
3), 123.5 (C-4), 128.1 126.2, 127.6, 128.7, 126.4 128.8 (C6H4), 133.3 129.2, 128.5, 132.2
(C6H5) ppm; MS: m/z(%) ˆ 291 (10), 245 (100); IR: ꢁ~ˆ 3262 (NH), 1671 (C=O) cmꢀ1
.
Reaction of alkyl phosphites 7 with 1,2-naphthoquinone-1-benzimide (8)
A mixture of freshly distilled trimethyl phosphite and/or dimethyl phosphite 7 (0.03 mol), 8, and dry
benzene (30 cm3) was stirred at room temperature for 4 h. The volatile materials were evaporated
under reduced pressure, and the residue was applied on a silica gel column using ethyl acetate/
petroleum ether (5:95, (v/v)) as eluent to give 14 as colorless crystals.
Yield: 80%; m.p.: 126ꢁC; C17H11NO (245.28); calcd.: C 83.25, H 4.52, N 5.71; found: C: 83.20,
1
H 4.50, N 5.67; H NMR: ꢀ ˆ 7.43±7.95 (m, 6H, aromatic), 8.32±8.60 (m, 5H, COPh) ppm; 13C
NMR: ꢀ ˆ 162.2 (N=C), 137.5 (C-1), 147.9 (C-2), 110.7 (C-3), 125.3 (C-4), 128.1, 126.9, 126.5,
127.4, 128.8, 131.0 (C6H4), 122.2, 127.2, 128.5, 131.1 (C6H5) ppm; MS: m/z(%) ˆ 245 (90).
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Received September 8, 1998. Accepted (revised) March 2, 1999