Reaction of dihydrodiazaphosphinines with acetylenic diesters: A direct synthesis of the λ5-diazaphosphaazulene skeleton

Article abstract of DOI:10.1002/(sici)1099-0690(199807)1998:7<1425::aid-ejoc1425>3.0.co;2-0

1,2-Duhydro-1,3,2-diazaphosphinine 2 reacts with acetylenedicarboxylic acid esters to give chemoselectively the adducts 5 or 6a, b, depending on the reaction conditions. Compound 6a is alternatively synthesized by treatment of equimolecular amounts of the

Full text of DOI:10.1002/(sici)1099-0690(199807)1998:7<1425::aid-ejoc1425>3.0.co;2-0

FULL PAPER
Reaction of Dihydrodiazaphosphinines with Acetylenic Diesters: A Direct
Synthesis of the λ5-Diazaphosphaazulene Skeleton
Jose Barluenga*a, Miguel Tomasa, Klaus Biegera, Santiago Garcıa-Grandab, and Rafael Santiago-Garcıab
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Instituto Universitario de Quımica Organometalica E. Moles, Universidad de Oviedoa,
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J. Claverıa s/n, E-33071 Oviedo, Spain
E-mail: barluenga@sauron.quimica.uniovi.es
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Departamento de Quımica Fısica y Analıtica (X-Ray Service), Universidad de Oviedob,
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J. Claverıa s/n, E-33071 Oviedo, Spain
E-mail: sgg@sauron.quimica.uniovi.es
Received February 12, 1998
Keywords: Phosphoris ylides / Iminophosphoranes / Phosphorus heterocycles / Rearrangements / Diazaphosphaazulene
1,2-Dihydro-1,3,2-diazaphosphinine 2 reacts with acetylene-
dicarboxylic acid esters to give chemoselectively the adducts
5 or 6a, b, depending on the reaction conditions. Compound
6a is alternatively synthesized by treatment of equimolecular
amounts of the previously described monoadduct 3(3Ј) and
dimethyl acetylenedicarboxylate. A reaction pathway is pro-
posed based primarily on i) the isolation and characterization
of intermediate 8(8Ј) and ii) the reactivity of 3(3Ј) towards
electrophiles, in particular with tetracyanoethylene (com-
pound 10).
Introduction
Results and Discussion
A few years ago we reported the synthesis of 1,2-dihydro-
First, 1,2-dihydro-1,3,2-diazaphosphinine 2 was formed
1,3,2-diazasilines and -germines and their potential as valu- by condensation of the corresponding 4-amino-1-azadiene
able precursors for 1,4-diazepine derivatives[1]. At that mo- 1 with dichloro(diisopropylamino)phosphane following a
ment we became intrigued by the particular behaviour of previously described procedure[5]. Then a solution of 2 in
trivalent phosphorus-containing substrates in heterocy- ether was stirred with excess of dimethyl acetylenedicarb-
cloaddition processes where the phosphanyl substituent can oxylate (DMAD) (molar ratio 1:3; Ϫ20°C to room tem-
act as a reactive peripherial functional group in cycload- perature) at Ϫ20°C for 12 h; removal of the solvent fol-
dition reactions. For instance, it has been shown that N- lowed by flash column chromatography and crystallization
phosphanyl imines[2] and N- and C-phosphanyl 1,3-di- from methylene chloride/hexane allowed to isolate the 1:2
poles[3] behave as 1,3- and 1,4-dipoles, respectively, leading adduct 5 as the major reaction product (yield 70%; 31P
to five- and six-membered rings.
NMR: δ ϭ 36.2) (Scheme 2).
Accordingly, we studied next the behaviour of the related
This result is in accordance with the reaction of tri-
1,2-dihydro-1,3,2-diazaphosphinines 2, readily available phenylphosphane with DMAD described by Tebby in 1969
from 4-amino-1-azadienes 1 and dichloro(diisopropyl- though the resulting adduct was never characterized crys-
amino)phosphane, and found that they displayed an inter- talographically[6]. Therefore, crystals of the λ5-diazaphos-
esting reactivity pattern towards dimethyl acetylenedicar- phinine derivative 5 were grown from diethyl ether/hexane
boxylate (DMAD) (Scheme 1)[4]. Thus, heterocycles 2 re- and an X-ray determination performed[7]
.
acted with DMAD in stoichiometric amounts to furnish
the complex heteropolycyclic structure 3(3Ј). Moreover, this
adduct was protonated and methylated through the valence
isomer 3Ј affording 4a, b by treatment with difluorochlo-
roacetic acid and methyl iodide, respectively. At this point
we thought about the possibility that a second equivalent of
DMAD would act as electrophile. The complex zwitterionic
species formed in this case could delineate new stabilization
pathways leading eventually to novel structures.
Therefore, reported herein is the formation of λ5-diaza- CO2Me, 31P NMR: δ ϭ 36.8; 6b: EϭCO2Et, 31P NMR:
phosphaazulene derivatives either by reaction of 2 with 2 δ ϭ 36.2), in yields of 89% (6a) and 85% (6b) of isolated
equivalents of dimethyl and diethyl acetylenedicarboxylate compounds (Scheme 3). It could be confirmed that 3(3Ј)
or by treatment of 3(3Ј) with an additional equivalent of was actually an intermediate in the process by treating it
Since the structure 5 unexpectedly does not arise from
the 1:1 adduct 3(3Ј) we turned our attention to the reaction
conditions. To our delight, we found that treatment at
Ϫ20°C of a diluted solution (c ca. 0.05 ) of diazaphosphi-
nine 2 with dimethyl and diethyl acetylenedicarboxylate
(molar ratio 1:2.4) in diethyl ether for 72 h and slowly rising
the temperature from Ϫ20°C to room temperature resulted
in the formation of a reaction product different from 5, na-
mely λ5-dihydrodiazaphosphaazulene derivative 6 (6a: Eϭ
DMAD.
with DMAD (molar ratio 1:1.1) under the same reaction
Eur. J. Org. Chem. 1998, 1425Ϫ1429
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
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J. Barluenga, M. Tomas, K. Bieger, S. Garcıa-Granda, R. Santiago-Garcıa
FULL PAPER
Scheme 1. Formation of heterocycles 3 by [5ϩ2] Cycloaddition of diazaphosphinines 2 with dimethyl acetylenedicarboxylate and their
reaction with electrophiles
Scheme 2. Formation of diazaphosphinine derivative 5 from 2 and
Figure 1. Crystal structure of 6a[a]
dimethyl acetylenedicarboxylate
conditions leading cleanly to compound 6a. This com-
pound exhibited an extraordinary thermal stability and
could be heated up to 300°C in air without appreciable
alteration. In addition, the yluric charge is well stabilized as
no protonation took place with weak acids (e.g. acetic acid).
Scheme 3. Formation of diazaphosphaazulene derivatives 6 from 2
or 3 and acetylenedicarboxylic acid esters
[a]
Selected bond lengths [pm] and bond angles [°]: N1ϪC2:
148.0(3); N1ϪP8a: 165.7(2); P8aϪN8: 156.1(3); P8aϪN9: 163.6(3);
P8aϪC3a: 178.1(3); N8ϪC7: 134.6(4); C2ϪC3: 152.9(4); C3ϪC3a:
134.0(4); C3aϪC4: 147.0(4); C4ϪC5: 136.6(4); C5ϪC6: 143.5(4);
C6ϪC7: 137.3(4); C2ϪN1ϪP8a: 113.8(2); N8ϪP8aϪN1: 117.5(2);
N8ϪP8aϪC3a: 110.9(1); N1ϪP8aϪC3a: 94.6(1); C7ϪN8ϪP8a:
129.8(2); N1ϪC2ϪC3: 105.7(2); C3aϪC3ϪC2: 116.1(2);
C3ϪC3aϪC4: 131.7(3); C3ϪC3aϪP8a: 109.5(2); C4ϪC3aϪP8a:
118.6(2); C5ϪC4ϪC3a: 120.5(2); C4ϪC5ϪC6: 127.8(3);
C7ϪC6ϪC5: 133.2(3); N8ϪC7ϪC6: 128.1(3).
found in concordance with the structural formula. All other
geometric parameters are in the range of expectation.
Concerning the mechanism involved in this complex
Because of the profound structural changes that had oc-
curred in this transformation and of the unique phos- transformation, we propose a reaction pathway which ac-
phorus-containing bicyclic framework, good quality crys- counts for the skeletal rearrangement and the [1,3]-CO2Me
tals of 6a were obtained from diethyl ether/THF and its shift (Scheme 4). First, nucleophilic attack of the yluric val-
structure unambiguously confirmed by an X-ray analysis ence isomer 3Ј onto the activated carbon-carbon triple
(Figure 1)[8]
.
bond would lead to the zwitterionic intermediate 7. Intra-
The bicyclic system is not flat but consists of two planar molecular nucleophilic attack from the alkenyl carbanion
subsystems. The first plane is formed by the phosphorus onto the ester function followed by a retroaldol-type car-
atom, N8, C7, C6, and C5 while the second is formed by bonϪcarbon bond cleavage would afford the intermediate 8
phosphorus, N1, C2, C3, C3A, and C4.
in equilibrium with its valence isomer 8Ј. Finally, the retro-
Endocyclic double- and single bonds are enlarged respec- Michael reaction of 8Ј leading to 9 followed by a formal
tively shortened by mesomeric effects, especially in the anionic [1,10]-electrocyclic ring closure can be invoked to
seven-membered ring moiety. Anyhow they still can be rationalize the last step of the reaction sequence.
1426
Eur. J. Org. Chem. 1998, 1425Ϫ1429

Direct Synthesis of the λ5-Diazaphosphaazulene Skeleton
FULL PAPER
Scheme 4. Mechanistic proposal for the formation of diazaphosphaazulene derivatives 6
Great mechanistic support stems from the isolation and Scheme 5. Formation of phosphonium salt 10 from 3 and tetracy-
anoethylene
spectroscopic characterization of intermediate 8(8Ј) (see Ex-
perimental Section). Thus, its 13C- and 31P-NMR spectra
perfectly match those of the analogous precursor 3(3Ј). For
instance, the 13C-NMR resonances of the seven-membered
ring carbon atoms of 8(8Ј) are found at δ ϭ 164.3, 142.1,
112.2, 87.0, and 62.2 [for 3(3Ј): δ ϭ 167.1, 137.5, 96.5, 84.6,
and 67.2] and the 31P-NMR signal of 8(8Ј) appears at δ ϭ
44.1 [for 3(3Ј): 48.2]. Left at room temperature in solution
8(8Ј) disappears within 12 h yielding 6 as the only product
according to NMR spectroscopy. The ring-opening of 8(8Ј)
leading to 9 has precedent in the room temperature re-
arrangement of bicyclo[3,2,1]-1-phospha-2,8-diaza-1,3,6-
octatriene 3(3Ј) into its isomer bicyclo[3,2,1]-1-phospha-7,8-
diaza-1,3,6-octatriene[4]
.
Moreover, support of the first step could be obtained by
using an appropriate substrate, instead of DMAD, so as
the first non-isolated intermediate could be stabilized, and
therefore isolable, without framework disruption. To verify
this hypotesis TCNE was chosen and found that its reaction
with 3(3Ј) (molar ratio 1:1.05) in diethyl ether (Ϫ20°C to
room temperature) led exclusively to the phosphonium cy-
anide salt 10 (Scheme 5). The formation of such a com-
pound should imply again an initial nucleophilic attack to
form 11, which is analogous to 7, followed by cyanide dis-
placement to give the final adduct.
In summary, it is shown that the readily available 1,2-
dihydro-1,3,2-diazaphosphinines 2 are excellent precursors
for the efficient synthesis of novel phosphorus heterocycles
which can be seen as heteroanalogues of biologically im-
portant systems by reaction with acetylenedicarboxylic acid
esters. The reaction involves a complex mechanism and un-
conventional intermediate structures. A mechanistic pro-
posal based on the reactivity of the monoadduct 3(3Ј) and
on the characterization of intermediate 8(8Ј) is outlined. It
should be pointed out that ester migrations are seemingly
rare processes, particularly the present [1,3]-shift that occurs
below room temperature and that has no precedent in the
trand and co-workers have noted a [1,2]-CO2Me shift at
80°C and have rationalized it by a similar pathway[2b]
.
This work was supported by DGICYT (Projects PB92-1005 and
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PB94-1313), the Ministerio de Educacion y Ciencia (Fellowship to
R. S.-G.) and the European Communities (Fellowship to K.B.; Con-
tract No. ERBCHBICT941732).
Experimental Section
General: All reactions were carried out under nitrogen. Solvents
were purified by standard methods[9]. Chemicals were of reagent
grade. Compounds 1 were prepared according to the literature re-
ports[10]. Ϫ Flash column chromatography was carried out on silica
gel 60 (230Ϫ400 mesh). Ϫ Melting points were obtained on a
Büchi-Tottoli apparatus using open capillary tubes and are uncor-
rected. Ϫ NMR spectra were run in CDCl3 on Bruker AC 200
and AC300 spectrometers. Ϫ Mass spectra were determined on HP
5987A (EIMS) spectrometer.
Synthesis of λ5-Diazaphosphinine 5: To a well stirred solution of
diazadihydrophosphinine 2 (0.57 g, 1.3 mmol) in 10 ml of CH2Cl2
at Ϫ20°C was added a solution of DMAD (0.84 g, 6 mmol) in 5
ml of CH2Cl2. The mixture was slowly warmed to room tempera-
ture and the solvent and excess of ester removed under reduced
pressure. The residue was subjected to flash chromatography (SiO2;
literature to the best of our knowledge. In this context, Ber- eluent: CH2Cl2 and then CH2Cl2/ether) to afford 5 ( 0.64 g, 70%),
Eur. J. Org. Chem. 1998, 1425Ϫ1429 1427

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J. Barluenga, M. Tomas, K. Bieger, S. Garcıa-Granda, R. Santiago-Garcıa
FULL PAPER
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yellow crystals, m.p. 240°C (dec.). Ϫ IR: νmax ϭ 1766 cmϪ1, 1751, CH2); 57.1 (s, CH); 54.9 (s, OCH3); 46.8 [b, CH(CH3)2]; 40.4 [d,
1689, 1631, 1605, 1548, 1492, 1344, 1255, 1236, 1207, 1176, 1159,
3J(P,C) ϭ 21.9 Hz, C(CH3)3]; 33.1 (s, CH3); 31.5 (b, CH2); 30.2 (s,
1120, 1103, 1012, 852, 831, 821. Ϫ 31P NMR: δ ϭ 36.2. Ϫ 1H
CH3); 27.0 (s, CH2); 26.4 (s, CH2); 25.3 (s, CH3); 23.2 (s, CH3);
NMR: δ ϭ 7.5 (b, 2 H), 6.9 (m, 2 H), 6.2 (s, 1 H), 3.8Ϫ3.3 (m, 14 13.9 (s, CH3); 13.7 (s, CH3). Ϫ MS (EI, 70 eV); m/z: 783 [Mϩ]; 740
H, 4 H), 3.0 (s, 3 H), 2.5 (m, 1 H), 1.4Ϫ1.1 (m, 31 H). Ϫ 13C NMR: [Mϩ Ϫ C3H7]; 710 [Mϩ Ϫ CO2C2H5]. Ϫ C42H62N3O9P (783.9):
3
2
δ ϭ 194.2 [d, J(P,C) ϭ 7.6 Hz, CN], 192.0 [d, J(P,C) ϭ 7.6 Hz, calcd. C 64.35, H 7.97, N 5.36; found C 63.95, H 7.93, N 5.09.
CCar], 168.3 (s), 166.2 (s), 162.2 [d, J(P,C) < 2 Hz, CO], 161.1 (s,
Intermediate 8(8Ј): To a well stirred mixture of 0.4 g (0.68 mmol)
CarO), 160.4 [d, J(P,C) ϭ 20.1 Hz, CO], 158.5 [d, J(P,C) ϭ 4.2 Hz,
of 3(3Ј) in 10 ml of CH2Cl2 were added 0.1 g (0.8 mmol) of DMAD
CO], 132.0 (b, CHar), 128.8 [d, 2J(P,C) ϭ 6.2 Hz], 113.8 [d,
in 10 ml of CH2Cl2 at Ϫ70°C. Then the mixture was left overnight
allowing it to warm up to Ϫ20°C. It was rapidly concentrated to
3
3J(P,C) ϭ 29.1 Hz, CH], 113.0 (s, CHar), 104.5 [d, J(P,C) ϭ 13.2
Hz, C(CO2CH3)ϭC-CO2CH3], 86.6 [d, 3J(P,C) ϭ 14.6 Hz, C-
3Ϫ4 ml at reduced pressure between Ϫ20 and 0°C and 5Ϫ10 ml
OCH3], 78.4 [d, 1J(P,C) ϭ 174.1 Hz, PC], 59.0 (s, CH), 55.0 (s,
of hexane added. Crystallization occurred on standing at Ϫ30°C
OCH3), 52.1 (s, OCH3), 51.9 (s, OCH3), 51.5 (s, OCH3), 50.6 (s,
affording 8(8Ј), orange solid (decomposes on warming). Ϫ 31P
OCH3), 48.5 [d, 2J(P,C) ϭ 6.2 Hz, CH], 40.4 [d, 3J(P,C) ϭ 20.1 Hz,
1
NMR: δ ϭ 44.4. Ϫ H NMR: δ ϭ 7.8Ϫ7.6 (m, 1 H); 7.3Ϫ7.1 (m,
C(CH3)3], 34.7 (s, CH2), 33.0 (s, CH2), 28.0 (s, CH3), 26.4 (s, CH2),
1 H); 7.0Ϫ6.8 (m, 2 H); 5.0 (s, 1 H); 4.5Ϫ4.3 (m, 1 H); 3.9 (s, 6
24.7 (s, CH2), 23.2 (s, CH2), 22.1 [d, 3J(P,C) ϭ 2.1 Hz, CH3]. Ϫ
H); 3.8 (s, 3 H); 3.6 (s, 3 H); 3.3 (s, 3 H); 3.7Ϫ3.3 (m, 2 H); 2.9Ϫ2.8
MS (EI, 70 eV); m/z: 727 [Mϩ]; 644 [Mϩ Ϫ C6H11].
(m, 1 H); 1.7Ϫ0.8 (m, 30 H). Ϫ 13C NMR: δ ϭ 164.7 (b, CO2CH3);
Synthesis of λ5-Diazaphosphaazulene 6a. Ϫ Method A: To a well
stirred solution of 2.2 g (5 mmol) of diazadihydrophosphinine 2 in
164.3 [d, J(P,C) ϭ 18.5 Hz, CN]; 163.6 [d, 3J(P,C) ϭ 18.5 Hz,
CO2CH3]; 162.3 (b, CO2CH3); 158.3 (s, CarO); 142.1 (b, PCC);
10 ml CH2Cl2 at Ϫ20°C were added 1.7 g (12 mmol) of dimethyl 133.2 [d, 3J(P,C) ϭ 9.8 Hz, CCar]; 131.3 (b, CϭC); 130.2 (s, CHar);
acetylenedicarboxylate (DMAD) in 5 ml of CH2Cl2. The mixture 129.7 (b, CϭC); 127.6 (s, CHar); 113.9 (s, CHar); 112.2 [d, 1J(P,C) ϭ
2
was left overnight allowing it to reach slowly room temperature.
Then it was left for an additional two days at room temperature,
the solution filtered through SiO2 and the solvent evaporated. Crys-
132.2 Hz, PC]; 87.0 [d, 3J(P,C) ϭ 17.6 Hz, CN]; 62.8 [d, J(P,C) ϭ
13.2 Hz, CN]; 55.0 (s, CN); 54.2 (s, OCH3); 52.9 (s, OCH3); 52.6
(s, OCH3); 51.3 (s, OCH3); 46.1 (s, NCH); 45.6 [d, 2J(P,C) ϭ 9.81
tallization from ether/CH2Cl2 afforded 3.1 g of 6a: 3.1 g (89%). Ϫ Hz, NCH]; 38.0 [d, 3J(P,C) ϭ 23.4 Hz, C(CH3)3]; 34.5 (b, CH2);
Method B: Compound 3(3Ј) (1.5 g, 2.5 mmol) was dissolved at
31.5 (s, CH2); 31.0 (s, CH2); 29,0 (s, CH3); 28.9 (s, CH2); 27.5 (s,
Ϫ20°C in 15 ml of CH2Cl2 and 0.38 g (2.7 mmol) of DMAD in 5 CH2); 27.1 (s, CH2); 26.7 (s, CH2); 25.1 (s, CH2); 25.0 (s, CH3);
ml of CH2Cl2 were added. The mixture was stirred overnight and
24.0 (s, CH3); 21.6 (s, CH3); 20.4 (s, CH3). Ϫ MS (EI, 70 eV); m/z:
allowed to warm slowly to room temperature. After filtration 727 (Mϩ); 684 (Mϩ Ϫ C3H7); 668 (Mϩ Ϫ CO2CH3).
through SiO2, the product was crystallized in CH2Cl2 and the sol-
Synthesis of the Phosphonium Cyanide 10: Compound 3(3Ј) (0.5
vent evaporated to furnish 1.7 g of 6a (90%), red crystals, m.p.
g, 0.85 mmol) was dissolved in 20 ml of CH2Cl2 at Ϫ20°C and 0.12
g (0.9 mmol) of tetracyanoethylene in 20 ml CH2Cl2 were added.
The well stirred mixture was left overnight allowing it to reach
room temperature. Then the solvent was removed under reduced
pressure and the residue crystallized from CH2Cl2/Et2O. Yield 0.55
g (90%), colorless crystals. Ϫ 31P NMR: δ ϭ 46.3. Ϫ 1H NMR:
δ ϭ 7.4Ϫ7.3 (m, 2 H); 7.0Ϫ6.8 (m, 2 H); 4.4 (s, 1H); 3.9Ϫ3.4 (m
and 3s, 11 H); 3.3Ϫ3.1 (m, 1 H); 1.8Ϫ0.9 (m and s, 31 H). Ϫ 13C
˜
235°C. Ϫ IR νmax: 1784 cmϪ1, 1765, 1767, 1729, 1703, 1605, 1506,
1478, 1407, 1243, 1175, 1120, 1040, 803. Ϫ 31P NMR: δ ϭ 36.8. Ϫ
1H NMR: δ ϭ 7.2Ϫ7.1 (m, 2 H); 6.9Ϫ6.8 (m, 2 H); 5.1 (m, 1 H);
4.0Ϫ3.5 (m, 3 H); 3.8 (s, 3 H); 3.8 (s, 3 H); 3.7 (2s, 6 H); 3.3 (s, 3
H); 2.2Ϫ0.9 (m, 25 H). Ϫ 13C NMR: δ ϭ 172.5 [d, 3J(P,C) ϭ
3
2.8 Hz, CO2CH3]; 167.5 [d, J(P,C) ϭ 3.5 Hz, CO2CH3]; 167.3 [d,
3J(P,C) ϭ 3.5 Hz, CO2CH3]; 164.0 [d, 2J(P,C) ϭ 20.1 Hz, CN];
158.2 (s, CarO); 154.8 (s, CCar); 139.2 (s, CCar); 134.5 [d, 1J(P,C) ϭ
2
3
NMR: δ ϭ 206.1 [d, J(P,C) ϭ 8.6 Hz, CϭN]; 164.0 [d, J(P,C) ϭ
11.0 Hz, CO2CH3]; 162.7 (s, CO2CH3); 160.5 (s, CarO); 134.9 (s);
132.6 (s); 130.5 (s, CHar); 121.7 (s); 120.5 [d, 3J(P,C) ϭ 8.6 Hz,
2
96.4 Hz, PC]; 128.4 (s, CHar); 126.1 [d, J(P,C) ϭ 22.8 Hz, PCC];
112.8 (s, CHar); 104.7 [d, 2J(P,C) ϭ 11.8 Hz, PCC]; 104.0 [d,
2
3J(P,C) ϭ 5.5 Hz; CH]; 73.1 [d, J(P,C) ϭ 22.2 Hz, C(CO2CH3)2];
2
CCar]; 116.1 (s); 115.0 (s); 113.3 (s, CHar); 113.2 [d, J(P,C) ϭ 10.2
56.7 [d, 2J(P,C) ϭ 2.1 Hz, CN]; 54.9 (s, ArOCH3); 52.8 (s, OCH3);
52.7 (s, OCH3); 51.8 (s, OCH3); 50.5 (s, OCH3); 46.9 [b, CH(CH3)2];
Hz, PCCϭC]; 110.4 (s); 108.3 (s); 57.2 [d, 2J(P,C) ϭ 2.4 Hz, CCar];
56.0 (s, NCH); 54.8 (s, OCH3); 53.4 (s, OCH3); 53.0 (s, OCH3);
48.2 (b, NCH); 44.0 [d, 3J(P,C) ϭ 19.6 Hz, C(CH3)3]; 35.9 (s, PCC);
2
40.5 [d, J(P,C) ϭ 22.2 Hz, C(CH3)3]; 32.9 (s, CH2); 30.8 (s, CH2);
30.2 (s, CH3); 26.9 (s, CH2); 26.4 (s, CH2); 25.2 (s, CH2); 23.1 (s,
CH3). Ϫ MS (EI, 70 eV); m/z: 727 [Mϩ], 685 [Mϩ Ϫ C3H7], 668
[Mϩ Ϫ CO2CH3]. Ϫ C38H54N3O9P (727.8): calcd. C 62.71, H 7.48,
N 5.77; found C 62.55, H 7.28, N 5.69.
3
33.0 [d, J(P,C) ϭ 18.8 Hz, CH]; 31.4 (s, CH2); 30.7 (s, CH2); 26.8
(s, CH3); 25.8 (s, CH2); 25.4 (s, CH2); 23.9 (s, CH2); 23.3 (b, CH3);
20.2 (b, CH3).
Synthesis of λ5-Diazaphosphaazulene 6b. Ϫ Method A: The above
procedure was followed using 2.2 g (5 mmol) of diazadihydrophos-
phinine 2 and 2.0 g (12 mmol) of diethyl acetylenedicarboxylate.
Yield 3.2 g (85%), red oil. Ϫ 31P NMR: δ ϭ 36.2. Ϫ 1H NMR:
δ ϭ 7.1 [d, 2 H, J(H,H) ϭ 8.9 Hz]; 6.8 [d, 2 H, J(H,H) ϭ 8.9 Hz];
5.1 [d, 1 H, 4J(P,H) ϭ 1.9 Hz]; 4.3Ϫ3.4 (m, 11 H); 3.77 (s, 3 H);
´
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´
3
2.1Ϫ0.9 (m, 37 H). Ϫ 13C NMR: δ ϭ 172.0 [d, J(P,C) < 2.5 Hz,
Reau, F. Dahan, G. Bertrand, J. Org. Chem. 1994, 59, 5927.
T. Facklam, O. Wagner, H. Heydt, M. Regitz, Angew. Chem.
[3]
CO2C2H5]; 167.0 [d, 3J(P,C) ϭ 3.1 Hz, CO2C2H5]; 166.8 [d,
3J(P,C) ϭ 3.1 Hz, CO2C2H5]; 165.7 [d, 3J(P,C) ϭ 9.4 Hz,
CO2C2H5]; 163.7 [d, 2J(P,C) ϭ 20.3 Hz, CN]; 158.1 (s, CarO); 154.9
1990, 102, 316; Angew. Chem. Int. Ed. Engl. 1990, 29, 314; J.
´
Tejeda, R.Reau, F. Dahan, G. Bertrand, J. Am. Chem. Soc.
1993, 115, 7880; M. Granier, A. Baceiredo, M. Nieger, G. Ber-
trand, Angew. Chem. 1990, 102, 1185; Angew. Chem. Int. Ed.
Engl. 1990, 29, 1123; F. Castan, M. Granier, T. A. Straw, A.
Baceiredo, K. B. Dillon, G. Bertrand, Chem. Ber. 1991, 124,
1739; T. Saito, M. Nagashima, T. Karakasa, S. Motoki, J.
Chem. Soc., Chem. Commun. 1992, 411.
1
(s, CCar); 139.6 (s, Car); 133.4 [d, J(P,C) ϭ 96.3 Hz, PC]; 128.4 (s,
CHar); 112.6 (s, CHar); 104.9 [d, 3J(P,C) ϭ 11.0 Hz, PCC]; 103.8
[d, 3J(P,C)
ϭ ϭ 21.9 Hz,
5.3 Hz, CH]; 74.5 [d, 2J(P,C)
C(CO2C2H5)2]; 61.8 (s, CH2); 61.8 (s, CH2); 60.6 (s, CH2); 59.1 (s,
1428
Eur. J. Org. Chem. 1998, 1425Ϫ1429

Direct Synthesis of the λ5-Diazaphosphaazulene Skeleton
FULL PAPER
˚
´
´
[4]
J. Barluenga, M. Tomas, K. Bieger, S. Garcıa-Granda, R. Santi-
´
group P1, a ϭ 10.781(6), b ϭ 11.173(5), c ϭ 17.008(8) A, α ϭ
˚
ago-Garcıa, Angew. Chem 1996, 108, 977; Angew. Chem. Int.
84.63 (4), β ϭ 77.25(4), γ ϭ 84.99(3) deg, V ϭ 1985(2) A3,
´
Ed. Engl. 1996, 35, 896; J. Barluenga, M. Tomas, K. Bieger, S.
Z ϭ 2, Dx ϭ 1.218 Mg mϪ3, Mo-Kα radiation (graphite crystal
˚
´
´
Garcıa-Granda, R. Santiago-Garcıa, J. Organomet. Chem.
Monochromator, λ ϭ 0.71073 A), µ ϭ 0.124 mmϪ1, F(000) ϭ
780, T ϭ 293(2) K. Final conventional R ϭ 0.063 and wR2 ϭ
0.199 for 4404 “observed” reflections and 461 variables.
D. D. Perrin, W. L. F. Armarego, D. P. Perrin, Purification of
Laboratory Chemicals, 2nd ed., Pergamon, Oxford, 1983.
H. Hoberg, J. Barluenga, Synthesis 1970, 142; G. Wittig, S.
Fischer, M. Tanaka, Liebigs Ann. Chem. 1973, 1075.
[98055]
1997, 529, 233.
´
[5]
[6]
[7]
[8]
J. Barluenga, J. Jardon, F. Palacios, V. Gotor, Synthesis 1985,
[9]
309.
N. E. Waite, J. C. Tebby, R. S. Ward, D. H. Williams, J. Chem.
Soc. C 1969, 1100.
[10]
´
´
S. Garcıa-Granda, R. Santiago-Garcıa, K. Bieger, Acta Cryst.
1996, C52, 2857.
Crystal data of 6a C38H54N3O9P, Mr ϭ 727.81, Triclinic, space
Eur. J. Org. Chem. 1998, 1425Ϫ1429
1429