Mechanism of the exchange reaction of halodiazirines with nucleophiles revisited. Synthesis of neutral, mono- or dicationic 4-16-membered phosphorus heterocycles

Article abstract of DOI:10.1021/ja9532143

Trimethyl-, diphenylmethyl-, triphenyl-, diphenylthienyl-, and bis(dimethylamino)(isopropylthio)phosphine react with bromophenyldiazirine (1) giving cationic N,N'-bis(phosphine) adducts 2a-c, 7, and 8 in 83-95% yields. Depending on the experimental condit

Full text of DOI:10.1021/ja9532143

1060
J. Am. Chem. Soc. 1996, 118, 1060-1065
Mechanism of the Exchange Reaction of Halodiazirines with
Nucleophiles Revisited. Synthesis of Neutral, Mono- or
Dicationic 4-16-Membered Phosphorus Heterocycles
Gilles Alcaraz,† Vale´rie Piquet,† Antoine Baceiredo,† Franc¸oise Dahan,†
Wolfgang W. Schoeller,*,‡ and Guy Bertrand*,†
Contribution from the Laboratoire de Chimie de Coordination du CNRS, 205, route de Narbonne,
31077 Toulouse, Ce´dex, France, and Fakulta¨t fu¨r Chemie der UniVersita¨t, Postfach 10 01 31,
D-33615 Bielefeld, Germany
ReceiVed September 20, 1995. ReVised Manuscript ReceiVed NoVember 20, 1995X
Abstract: Trimethyl-, diphenylmethyl-, triphenyl-, diphenylthienyl-, and bis(dimethylamino)(isopropylthio)phosphine
react with bromophenyldiazirine (1) giving cationic N,N′-bis(phosphine) adducts 2a-c, 7, and 8 in 83-95% yields.
Depending on the experimental conditions used, addition of 1,2-bis(diphenylphosphino)ethane to 1 leads to dicationic
14- and monocationic seven-membered heterocycles 3 (90% yield) and 4 (60% yield) or cationic N,N′-bis(diphosphine)
adduct 5 (86% yield); similarly, when diphenyl(isopropylthio)phosphine is used, competitive reactions occur, leading
to cationic five-membered heterocycle 9 (34% yield) and/or N,N′-Bis(diphosphine) adduct 10 (65% yield). 1,3-bis-
(diphenylphosphino)propane also reacts with 1, affording dicationic 16-membered heterocycle 6 (75% yield). Addition
of bis(diisopropylamino)(trimethylstannyl)phosphine to 1 gives rise to a mixture of N-[(trimethylstannyl)imino]bis-
(diisopropylamino)bromophosphorane (11) (32%), 2,2-bis(diisopropylamino)-4-phenyl-1,3,2λ5-diazaphosphete (12)
(26% yield), 1,3,5,2λ5-triazaphosphinine 13 (3% yield), benzonitrile (35%), and bromotrimethylstannane (60%). The
mechanisms involved in these reactions are studied.
Introduction
Scheme 1
The mechanism of the exchange reaction of nucleophiles with
halodiazirines has attracted considerable interest and has been
a highly controversial topic in the last few years.1 It was first
suggested that the halodiazirine was in equilibrium with a
diazirinium cation, which was captured by the nucleophile.1b,2
On the basis of kinetic studies, labeling experiments, and the
nature of the observed products, Creary1a,3 and Dailey4 inde-
pendently concluded that the first step of the exchange reaction
Here we report a detailed investigation9 of the mechanism
of the reaction of bromophenyldiazirine 1 with phosphines, and
we demonstrate the enormous synthetic potentiality of this three-
membered heterocycle.
-
with nucleophiles such as MeO-, F-, and N3 proceeds in an
SN2′ fashion. When the nucleophile was fluoride, a second SN2′
attack at carbon led to the C-fluoro-substituted diazirine, while
with azide a nitrile was formed. Lastly, Creary5a,b and Moss5c
showed that azide or acetate ions can also react with certain
halodiazirines Via an SRN1 substitution mechanism, while with
thiophenoxide a redox process can occur.6
On the other hand, diazirines are known to easily lose
dinitrogen and therefore are powerful precursors for a variety
of carbenes;1b,7 however, these CN2 rings8 by themselves have
never been used as building blocks.
Results
Bromophenyldiazirine (1)2a reacts, in dichloromethane solu-
tion, with 2 equiv of trimethyl-, diphenylmethyl-, and triphen-
ylphosphine, affording the bisadducts 2 in near quantitative
yields. According to 31P NMR spectroscopy the reaction was
complete within 5 min at -78 °C with trimethylphosphine, while
with Ph2MeP and Ph3P, the reaction at room temperature reached
completion after 10 and 18 h, respectively. The use of just 1
equiv of phosphine left 50% of the starting bromophenyldiaz-
irine 1 unreacted. The ionic structure of bisadducts 2 was
obvious from their poor solubility in nonpolar solvents and from
the mass spectra. In the 13C NMR spectra the ipso and imino
carbon atoms of the benzamidine fragment appeared as triplets,
indicating the presence of two magnetically equivalent phos-
phorus atoms (Scheme 1).
† Laboratoire de Chimie de Coordination du CNRS.
‡ Fakulta¨t fu¨r Chemie der Universita¨t.
X Abstract published in AdVance ACS Abstracts, January 15, 1996.
(1) For reviews, see: (a) Creary, X. Acc. Chem. Res. 1992, 25, 31. (b)
Moss, R. A. Acc. Chem. Res. 1989, 22, 15.
(2) (a) Graham, W. H. J. Am. Chem. Soc. 1965, 87, 4396. (b) Krogh-
Jespersen, K.; Young, C. M.; Moss, R. A.; Wostowski, M. Tetrahedron
Lett. 1982, 23, 2339. (c) Moss, R. A.; Terpinski, J.; Cox, D. P.; Denney,
D. Z.; Krogh-Jespersen, K. J. Am. Chem. Soc. 1985, 107, 2743. (d) Liu,
M. T. H.; Paike, N. Tetrahedron Lett. 1987, 28, 3763. (e) Liu, M. T. H.;
Doyle, M. P.; Loh, K.-L.; Anand, S. M. J. Org. Chem. 1987, 52, 323.
(3) Creary, X.; Sky, A. F. J. Am. Chem. Soc. 1990, 112, 368.
(4) (a) Bainbridge, K. E.; Dailey, W. P. Tetrahedron Lett. 1989, 30, 4901;
(b) Dailey, W. P. Tetrahedron Lett. 1987, 28, 5801.
(7) Moss, R. A.; Xue, S.; Liu, W. J. Am. Chem. Soc. 1994, 116, 1583.
(8) For reviews on diazirines, see: (a) Liu, M. T. H. Chem. Soc. ReV.
1982, 11, 127. (b) Heine, H. W. In The Chemistry of Heterocyclic
CompoundssSmall Ring Heterocycles; Wiley: New York, 1983; Vol. 42,
Part 2, pp 588. (c) Chemistry of Diazirines; Liu, M. T. H., Ed.; CRC Press,
Inc.: Boca Raton, FL, 1987; Vols. I and II.
(5) (a) Creary, X.; Sky, A. F.; Phillips, G. J. Org. Chem. 1990, 55, 2005;
(b) Creary, X. J. Org. Chem. 1993, 58, 7700. (c) Moss, R. A.; Xue, S.;
Liu, W. J. Am. Chem. Soc. 1994, 116, 10821.
(6) Creary, X.; Sky, A. F.; Phillips, G.; Alonso, D. E. J. Am. Chem.
Soc. 1993, 115, 7584.
(9) For a preliminary account of this work, see: Alcaraz, G.; Baceiredo,
A.; Nieger, M.; Bertrand, G. J. Am. Chem. Soc. 1994, 116, 2159.
0002-7863/96/1518-1060$12.00/0 © 1996 American Chemical Society

Exchange Reaction of Halodiazirines with Nucleophiles
J. Am. Chem. Soc., Vol. 118, No. 5, 1996 1061
Scheme 2
Scheme 3
Since 2 equiv of phosphine were necessary, we then studied
the reaction of 1 with diphosphines. Depending on the dilution,
different products were obtained. Addition at -78 °C of a
stoichiometric amount of 1,2-bis(diphenylphosphino)ethane to
a 0.1 M dichloromethane solution of 1 cleanly led to dicationic
14-membered ring 3, which was isolated in 90% yield (white
solid, mp 278 °C). The dimeric and dicationic nature of 3 was
proved by mass spectroscopy, and the high symmetry of the
molecule was evident from the 31P and 13C NMR data [δ31P
+22.5 (s); δ13C +180.2 (t, J(PC) ) 3.6 Hz, CdN)].
When the reaction was performed under the same experi-
mental conditions, but using a 0.01 M solution of 1, a 90/10
mixture (according to 31P NMR spectroscopy) of 7-membered
ring 4 and macrocycle 3 was obtained. Cationic heterocycle 4
was isolated after purification by liquid chromatography in 60%
yield as a white powder (mp 262 °C). The mass spectrum and
elemental analysis of 4 indicate the addition of only one
molecule of diphosphine. The presence of only one signal in
the 31P NMR spectrum (+20.8) and of a triplet for the amidine
carbon at +169.7 (J(PC) ) 5.3 Hz) in the 13C NMR spectrum
support the magnetic equivalence of the two phosphorus atoms
as expected for seven-membered ring 4.
When 2 equiv of bis(diphenylphosphino)ethane was added
at -78 °C to a 0.1 M dichloromethane solution of bromophen-
yldiazirine (1), the formation of bisadduct 5 was observed. The
reaction was complete after stirring one night at room temper-
ature, and 5 was isolated as a white solid (mp 134 °C) in 86%
yield. The mass spectrum indicates the presence of two bis-
(diphenylphosphino)ethane fragments for only one amidine. As
expected, the 31P NMR spectrum appears as an AX system
[-12.6 and +23.5, J(PP) ) 45.4 Hz], while in the 13C NMR
spectrum the amidine carbon appears as a triplet (+179.9, J(PC)
) 6.5 Hz). Moreover, addition at room temperature of a
stoichiometric amount of diazirine 1 to bisadduct 5 also led to
macrocycle 3 in 92% yield (Scheme 2).
In order to demonstrate the generality of the method for the
synthesis of dicationic macrocycles, a stoichiometric amount
of 1,3-bis(diphenylphosphino)propane was added at low tem-
perature to a 0.1 M solution of bromodiazirine 1, and indeed,
16-membered heterocycle 6 was obtained and isolated after
purification by liquid chromatography as a brown solid (mp
202 °C) in 75% yield (Scheme 2).
diazirine 1, leading to the cationic bisadducts 7 and 8, in 95
and 93% yield, respectively. However, when the diphenyliso-
propylthiophosphine was used, once again, the outcome of the
reaction was strongly dependent on the dilution. With a 0.01
M dichloromethane solution of 1 and diphenyl(isopropylthio)-
phosphine, a 50/50 mixture (according to 31P NMR spectros-
copy) of the cationic five-membered heterocycle 9 and the
bisadduct 10 was obtained. Compound 9 was isolated as a white
powder (mp 113 °C) in 34% yield, and its monoadduct structure
easily proved by mass and 13C NMR spectroscopies (+167.9,
d, J(PC) ) 10.3 Hz, NCN). Using a concentrated solution of
1 (0.2 M) and 1 equiv of thiophosphine, bisadduct 10 was
obtained in 65% yield with no trace of 9 being observed
-
(Scheme 3). The structure of 10 (with PF6 as counteranion)
was clearly established by an X-ray diffraction study (see
supporting information). As expected, the positive charge is
delocalized on the PNCNP backbone, the phosphine being in a
syn-anti arrangement with respect to the benzamidine fragment.
Lastly, the question arises as to what would be the outcome
of the reaction using a phosphine bearing a leaving group, which
could combine with the bromide anion and thus be eliminated.
The phosphorus-tin bond is reactive, and bromotrimethylstan-
nane easy to eliminate. Therefore, a stoichiometric amount of
bis(diisopropylamino)(trimethylstannyl)phosphine was added at
room temperature to a THF or dichloromethane solution of
bromophenyldiazirine 1. According to 31P NMR spectroscopy
and gas chromatographic analysis, the reaction mixture con-
tained benzonitrile (35%), bromotrimethylstannane (60%), [(tri-
methylstannyl)imino]bis(diisopropylamino)bromo-
phosphorane (11) (32%), 1,3,2λ5-diazaphosphete 12 (40%), and
1,3,5,2λ5triazaphosphinine 13 (5%). Benzonitrile, bromotri-
methylstannane, and iminophosphorane 11 were characterized
by comparison of their spectroscopic and physical data with
authentic samples. Four-π-electron four-membered ring 12 and
six-π-electron six-membered heterocycle 13 were isolated after
careful fractional crystallization as white crystals in 26 and 3%
yield, respectively (Scheme 4). Both heterocycles 12 and 13
have been fully characterized, and the X-ray crystal structures
will be published elsewhere.
When the reaction of 1 with bis(diisopropylamino)(trimeth-
ylstannyl)phosphine was performed in the presence of a large
excess of chlorotrimethylsilane, we observed (in addition to
diazaphosphete 12, benzonitrile, bromotrimethylstannane, and
a very small amount of iminophosphorane 11) the formation of
[(trimethylsilyl)imino]bis(diisopropylamino)chloro-
It was also of interest to investigate the reactivity of 1 toward
reagents featuring two different nucleophilic centers. Whatever
the experimental conditions, diphenylthienylphosphine and bis-
(dimethylamino)(isopropylthio)phosphine reacted with bromo-

1062 J. Am. Chem. Soc., Vol. 118, No. 5, 1996
Alcaraz et al.
Scheme 4
Scheme 6
Scheme 5
philicity of the phosphorus atom in the bis(dimethylamino)-
phosphine compared to the diphenylphosphine derivative. Note
that sulfides do not react with 1.
From these results, as a whole, it seems clear that only good
nucleophiles can react with bromodiazirine 1 and that the first
step of the reaction occurs through an SN2′ mechanism. When
phosphines are used, the resulting 1H-diazirines 16 have a
reasonable lifetime, probably due to the presence of the
phosphonio group, which decreases the effect of the destabilizing
anti-aromatic energy through negative hyperconjugation.13
Then, either an intermolecular SN2 reaction occurs with a second
molecule of phosphine or, in the case where a phosphine
substituent has a nucleophilic component, an intramolecular SN2
reaction can compete. Note that the formation of C-phosphonio-
3H-diazirine 19 (Scheme 5) is never observed, which is in
marked contrast with the results observed by Creary and Dailey
using small nucleophiles such as MeO- or F-.1a,4b A possible
explanation is that the cationic nature of the phosphorus
substituent of 1H-diazirines 16 strongly modifies the reactivity
of the three-membered ring. Alternatively, one could imagine
that the formation of the C-methoxy- or C-fluorodiazirine from
the 1H-diazirines does not involve an SN2′ reaction, as previ-
ously postulated,1a,4b but a 1,3-sigmatropic reaction. Such a
process would not occur in the case of 1H-diazirines 16 because
of the poor migrating ability of phosphines.
These results and, particularly, the formation of seven- and
five-membered heterocycles 4 and 9 allow us to postulate other
mechanisms rationalizing the observations by Creary and Dailey
in the reaction of 15N-labeled bromodiazirine 1* with azide
anion.1a,3,4a On the basis of the presence of 50% of 15N-labeled
benzonitrile, they independently concluded that an SN2′ attack
of azide upon the nitrogen atom led to N-azido-1H-diazirine
20, which rapidly eliminates N2 to give a transient 1,1-diazene
21 and then benzonitrile. Other possiblities are the following:
starting from N-azidodiazirine 20, an intramolecular attack of
the terminal nitrogen of the azido group at the second nitrogen
of the diazirine could give pentaazabenzene 23,14 or alternatively
the diazene 21 could undergo a ring expansion reaction to
triazacyclobutadiene 22. Both compounds 22 and 23 would
afford benzonitrile containing 50% 15N on decomposition
(Scheme 6). The latter possibility being rather fascinating, we
tried to model it by attempting to prepare a N-phosphino-1H-
diazirine 25 (Scheme 7) analogous with diazene 21, the
phosphorus atom of which possesses a lone pair of electrons
and vacant orbitals playing the role of the nitrene (1,1-diazenes
are nucleophilic nitrenes15).
phosphorane (14). Moreover, photolysis of bis(diisopropylami-
no)phosphine azide 1510 in the presence of bromotrimethyl-
stannane and chlorotrimethylsilane, cleanly led to 11 and 14,
respectively (Scheme 4).
Discussion
The rate of the reaction of bromodiazirine 1 increases with
the nucleophilicity of the phosphines, and the resulting products
2 featuring P-N bonds clearly demonstrate that the first step
is an SN2′ reaction leading to 1H-diazirine 16. These results
are in perfect agreement with the findings of Creary and Dailey
using other nucleophiles.1a,3,4 Two mechanisms could rational-
ize the formation of the second P-N bond: either an SN2
reaction of the phosphine with the second nitrogen atom of the
1H-diazirine 16 or the formation of an electrophilic imidoyl
nitrene 17, which would be trapped by phosphines (Scheme 5).
Note that Padwa reported that phenyllithium reacts with
phenylchlorodiazirine to give 18, a product resulting from N-N
bond cleavage11 and that the trapping of imidoyl nitrenes by
phosphines has been examplified.12
The results observed in the reaction of 1 with 1,2-bis-
(diphenylphosphino)ethane clearly indicate that the intermediate
has a reasonable lifetime, allowing an intermolecular reaction
(giving 3 or 5) to compete with the formation of the seven-
membered ring 4 (Scheme 2). Although, these results do not
totally rule out the possible transient formation of an imidoyl
nitrene of type 17, it is quite unlikely that such an intermediate
would afford the selectivity observed.
A similar conclusion can be drawn from the exclusive
formation of the bisadduct 7 since nitrenes are known to be
trapped by thiophene, although the difficulty of forming a seven-
membered ring cannot be neglected. A strong argument against
the transient formation of an imidoyl nitrene comes from
comparing the outcome of the reaction of 1 with bis(dimethyl-
amino)- and with diphenyl(isopropylthio)phosphine (Scheme 3).
The formation of five-membered rings is usually facile, and the
only difference between the two reactions is the higher nucleo-
We believe that the reaction of bis(diisopropylamino)-
(trimethylstannyl)phosphine with 1 gives the desired N-phos-
(10) (a) Sicard, G.; Baceiredo, A.; Bertrand, G.; Majoral, J. P. Angew.
Chem., Int. Ed. Engl. 1984, 23, 459. (b) Baceiredo, A.; Bertrand, G.; Majoral,
J. P.; El Anba, F.; Manuel, G. J. Am. Chem. Soc. 1985, 107, 3945.
(11) Padwa, A.; Eastman, D. J. Org. Chem. 1969, 34, 2728.
(12) (a) Haake, M. Tetrahedron Lett. 1972, 3405. (b) Smith, P. A. S. In
Azides and Nitrenes; Scriven, E. F. V., Ed.; Academic Press, London, 1984.
(13) Gilheany, D. G. Chem. ReV. 1994, 94, 1339.
(14) The possible involvement of pentaazabenzene 23 has been mentioned
by M. V. George, ref 24 in ref 1a.
(15) Dervan, P. B.; Sylwester, A. P. J. Am. Chem. Soc. 1984, 106, 4648.

Exchange Reaction of Halodiazirines with Nucleophiles
J. Am. Chem. Soc., Vol. 118, No. 5, 1996 1063
Table 1. Calculated Relative Energies (kcal mol-1) for the Parent
Diazaphosphete 12′, 1H-Diazirine 25′, Carbodiimide 28′, and
Transition State 29′
Scheme 7
level Aa
level Bb
12′
25′
28′
29′
-18.8
0
-61.3
+19.0
-23.7
0
-56.6
+24.7
a MP4SDTQ(fc)/6-31g**//RHF/6-31g** plus zero point vibrational
energy contribution at RHF level (unscaled). b MP4SDTQ(fc)/6-31g**/
/MP2(fc)/6-31g** plus zero point vibrational energy contribution at
MP2 level (unscaled).
Scheme 8
Table 2. Calculated Geometries for the Parent 1H-Diazirine 25′
and for Transition State 29′, Bond Lengths (Å), and Bond Angles
(deg)
PN1
PN2
N1N2
N2C
CN1
<PNNC
25′ a
25′ b
29′ a
29′ b
1.764
1.782
2.016
1.999
1.610
1.779
1.840
1.873
1.212
1.266
1.284
1.316
1.393
1.399
1.284
1.316
106.9
106.2
154.6
157.5
2.016
1.999
a RHF/6-31g** optimization. b MP2/6-31g** optimization.
Table 3. Experimental Conditions for the Reaction of 1 with
Phosphines
phino-1H-diazirine intermediate 25, Via the formation N-phos-
phoniodiazirine 24 with subsequent loss of trimethylbromo-
stannane. A ring expansion then occurs, explaining the forma-
tion of the 1,3,2λ5-diazaphosphete 12, which can be considered
as a stable analogue of triazacyclobutadiene 22 (Schemes 4 and
7).
The formation of benzonitrile and [(trimethylstannyl)imino]-
bis(diisopropylamino)bromophosphorane (11) strongly suggest
that N-phosphinodiazirine 25 can also be cleaved in a manner
analogous to that for nitrenodiazirine 21. Indeed, 11 probably
results from the trapping of phosphinonitrene 26 (“analogue”
of N2) by bromotrimethylstannane. This hypothesis is confirmed
by the formation of (i) [(trimethylsilyl)imino]bis(diisopropyl-
amino)chlorophosphorane (14) in the reaction of 1 with the
stannylphosphine in the presence of an excess of trimethylchlo-
rosilane and (ii) 11 and 14 in the photolysis of phosphine azide
15 in the presence of trimethylbromostannane and trimethyl-
chlorosilane, respectively (Schemes 2 and 4).10
In order to confirm the reaction mechanism, quantum
chemical calculations16 were performed on the parent 1,3,2λ5-
diazaphosphete 12′, N-phosphino-1H-diazirine 25′, and (N-
phosphino)imidoylnitrene 27′, as well as on the isomeric
carbodiimide 28′ (Scheme 8). The calculations were carried
out at RHF/6-31g** [A] and MP2(fc)/6-31g** [B] levels of
optimization. Subsequently the energies were refined by
MP4SDTQ(fc)17 electron correlation and zero point energy
corrections. At times the vibrational analyses of all stationary
points on the electronic hypersurface (within the harmonic
approximation) were performed at the same level as given by
the energy optimization of structures (levels A and B) (Table
1). Of particular interest, the nitrene 27′ is an unstable species
on the singlet hypersurface (at both levels of optimization) and
reaction
CH2Cl2 time (h) yield
1
(mmol)
R3P (mmol)
(mL)
(20 °C)
(%)
2a 2.18 Me3P (4.36)
6
5 min
85
(-78 °C)
2b 2.18 Ph2MeP (4.36)
2c 2.18 Ph3P (4.36)
6
6
25
250
50
25
10
18
18
18
36
18
36
88
83
90
60
86
75
95
3
4
5
6
7
2.49 Ph2P(CH2)2PPh2 (2.49)
2.49 Ph2P(CH2)2PPh2 (2.49)
5.02 Ph2P(CH2)2PPh2 (10.10)
2.49 Ph2P(CH2)3PPh2 (2.49)
2.18 (diphenyl)thienylphosphine 21
(4.36)
8
9
1.05 (Me2N)2P-S-iPr (2.16)
0.71 Ph2P-S-iPr (0.73)
10 0.71 Ph2P-S-iPr (0.73)
30
70
2.9
3
93
34
65
24
3
rearranges without activation energy to the corresponding
carbodiimide 28′. On the other hand, the diazaphosphete 12′
is more stable than the 1H-diazirine 25′ by -23.7 kcal/mol (level
B). The quantum chemical calculations indicate that the
phosphino group is almost perpendicular relative to the ring
plane and that there is a very long N-N distance for the strained
three-membered ring 25′ (1.610 Å at the RHF level and 1.779
Å after reoptimization at the MP2 level) (Table 2). A similar
elongation was experimentally observed for the C-N bond of
the C-phosphino-2H-azirine 30 (1.629 Å), which also easily
undergoes a ring expansion reaction affording the corresponding
four-π-electron four-membered heterocycle 3118 (Scheme 8).
The bond stretching is the consequence of the enormous ring
strain in three-membered rings possessing an endocyclic π-bond.19
The activation energy for the rearrangement of the 1H-diazirine
25′ into the diazaphosphete 12′ via the transition state 29′ was
found to be 24.7 kcal mol-1 (level B). Interestingly, the
(16) All quantum chemical calculations were performed with the
Gaussian-92 set of programs: Frisch, M. J.; Trucks, G. W.; Head-Gordon,
M.; Gill, P. M. W.; Wong, M. W.; Foresman, J. B.; Johnson, B. G.; Schlegel,
H. B.; Robb, M. A.; Replogle, E. S.; Gomperts, R.; Andres, J. L.;
Raghavachari, K.; Binkley, J. S.; Gonzalez, C.; Martin, R. L.; Fox, D. J.;
Defrees, D. J.; Baker, J.; Stewart, J. J. P.; Pople, J. A. Gaussian-92, Revision
A; Gaussian, Inc.: Pittsburgh, PA, 1992. For the 6-31g** basis set see:
Hariharan, P. C.; Pople, J. A. Chem. Phys. Lett. 1972, 66, 217. Francl, M.
M.; Pietro, W. J.; Hehre, W. J.; Binkley, J. S.; Gordon, M. S.; Defrees, D.
J.; Pople, J. A. J. Chem. Phys. 1982, 77, 3654.
+
transition state for this reaction refers to a PH2 cation which
interacts with an NCN- allylic anion with concomitant three-
center bonding between the phosphorus and the nitrogen atoms,
as witnessed by a corresponding charge density analysis.
(18) Alcaraz, G.; Wecker, U.; Baceiredo, A.; Dahan, F.; Bertrand, G.
Angew. Chem., Int. Ed. Engl. 1995, 34, 1246.
(19) The ring strain in the structurally related cyclopropene amounts to
53.8 kcal mol-1. Cox, J. D.; Pilcher, G. Thermochemistry of Organic and
Organometallic Compounds; Academic Press: New York, 1970.
(17) (a) Moeller, C.; Plesset, M. S. Phys. ReV. 1934, 46, 618. (b) Binkley,
J. S.; Pople, J. A. Int. J. Quantum Chem. 1975, 9, 229.

1064 J. Am. Chem. Soc., Vol. 118, No. 5, 1996
Alcaraz et al.
Conclusion
(M+ - Br). Anal. Calcd for C33H31N2P2Br: C, 66.33; H, 5.23;
N, 4.88. Found: C, 65.21; H, 4.97; N, 5.14.
These results clearly confirm that, in the 3H-bromophenyl-
diazirine 1 exchange reactions with phosphines, the first step
involves an SN2′ mechanism leading to transient N-phosphonio-
1H-diazirines 16. Then, inter- or/and intramolecular SN2
reactions at the unsubstituted nitrogen of 16 occur, inducing
N-N bond cleavage. The selectivity (intra- Versus intermo-
lecular reaction) observed, depending on the experimental
conditions used, suggests that the antiaromatic three-membered
heterocycles 16 have a reasonable lifetime. Since C-phospho-
nio-3H-diazirines 19 are not formed, it is quite likely that the
second step of the substitution reaction of 1 by small nucleo-
philes (MeO-, F-) does not involve an SN2′ mechanism but a
1,3-sigmatropic reaction.
The experimental results and the ab initio calculations strongly
suggest that N-phosphino-1H-diazirine 25 does not undergo a
ring-opening reaction to the corresponding imidoyl nitrene 27,
which appears not even as a minimum on the singlet hyper-
surface. The antiaromatic 1H-diazirine 25 undergoes a con-
certed ring expansion reaction, leading to the four-π-electron
four-membered heterocycle 12.
Bisadduct 2c. The residue was washed several times with
pentane to give 1.31 g (83% yield) of 2c as a pale yellow
powder: mp 100-101 °C; 31P NMR {1H} (CDCl3) +16.6; 13
C
NMR (CDCl3) 124.8 (d, J(PC) ) 101.5 Hz, Ci-P), 126.3 (s,
CmPh-C), 127.7 (s, CoPh-C), 129.1 (d, J(PC) ) 13.0 Hz, Cm-
Ph-P), 129.5 (s, CpPh-C), 132.3 (d, J(PC) ) 10.5 Hz, CoPh-P),
133.4 (s, CpPh-P), 139.3 (t, J(PC) ) 12.0 Hz, CiPh-C), 178.6
(t, J(PC) ) 6.2 Hz, NCN); mass spectrum m/z 641 (M+ - Br).
Anal. Calcd for C43H35N2P2Br: C, 71.57; H, 4.89; N, 3.88.
Found: C, 71.01; H, 4.67; N, 3.70.
14-Membered Heterocycle 3. The residue was purified by
flash chromatography on silica gel (MeOH) to give 1.33 g (90%
yield) of 3 as a white powder: mp 277-278 °C; 31P NMR {1H}
1
(CDCl3) +22.5; H NMR (CDCl3) 3.32 (s broad, 8 H, CH2),
6.70-7.80 (m, 50 H, Harom); 13C NMR (CDCl3) 19.0 (t, J(PC)
) 29.8 Hz, CH2), 123.5 (d, J(PC) ) 99.6 Hz, Ci-P), 126.2 (s,
CmPh-C), 126.7 (s, CoPh-C), 128.2 (s, CpPh-C), 129.0 (d, J(PC)
) 6.0 Hz, CmPh-P), 131.3 (d, J(PC) ) 4.5 Hz, CoPh-P), 132.9
(s, CpPh-P), 138.4 (t, J(PC) ) 6.6 Hz, CiPh-C), 180.2 (t, J(PC)
) 3.6 Hz, NCN); mass spectrum (FAB) m/z 1111 (M+ - Br),
515 (M2+ - 2Br). Anal. Calcd for C66H58N4P4Br2: C, 66.56;
H, 4.91; N, 4.70. Found: C, 66.08; H, 4.76; N, 4.55.
Lastly, it appears that 3H-diazirines are powerful building
blocks in heterocyclic chemistry; the high-yield synthesis of
dicationic macrocycles is of special interest.
Seven-Membered Ring 4. The residue was purified by flash
chromatography on silica gel (92:8 CHCl3-MeOH) to give 0.44
g (60% yield) of 4 as a white powder: mp 261-262 °C; 31P
Experimental Section
1
All experiments were performed under an atmosphere of dry
argon or nitrogen. Melting points were obtained on an
electrothermal capillary apparatus and were not corrected. 1H,
31P, and 13C NMR spectra were recorded on Bruker AC80,
AC200, WM250, or AMX400 spectrometers. 1H and 13C
chemical shifts are reported in parts per million relative to Me4-
Si as external standard. 31P downfield shifts are expressed with
a positive sign, in parts per million, relative to external 85%
H3PO4. Infrared spectra were recorded on a Perkin Elmer 1725
X. Mass spectra were obtained on a Ribermag R10 10E
instrument. Conventional glassware was used.
General Procedure for the Reactions of 1 with Phosphines.
To a dichloromethane solution of bromophenyldiazirine 1 was
added at -78 °C the corresponding phosphine. The reaction
was monitored by 31P NMR spectroscopy. After evaporation
of the solvent the products were purified as indicated below.
Further details concerning the reaction conditions are sum-
marized in Table 3.
Bisadduct 2a. The residue was washed several times with
pentane to give 0.65 g (85% yield) of 2a as a pale yellow
powder: mp 170-171 °C; 31P NMR {1H} (CDCl3) +30.1; 1H
NMR (CDCl3) 1.62 (d, J(PH) ) 13.4 Hz, 18 H, CH3), 7.08-
7.18 (m, 5 H, Harom); 13C NMR (CDCl3) 14.6 (d, J(PC) ) 66.4
Hz, CH3), 126.0 (s, Cp), 128.8 (s, Co), 130.0 (s, Cm), 140.7 (t,
J(PC) ) 12.7 Hz, Ci), 178.1 (t, J(PC) ) 7.2 Hz, NCN); mass
spectrum (DCI/NH3) m/z 269 (M+ - Br). Anal. Calcd for
C13H23N2P2Br: C, 44.71; H, 6.64; N, 8.02. Found: C, 43.97;
H, 7.00; N, 7.65.
Bisadduct 2b. The residue was washed several times with
pentane to give 1.1 g (88% yield) of 2b as a pale yellow
powder: mp 176-177 °C; 31P NMR {1H} (CDCl3) +20.1; 1H
NMR (CDCl3) 2.20 (d, J(PH) ) 13.0 Hz, 6 H, CH3), 7.13-
7.56 (m, 25 H, Harom); 13C NMR (CDCl3) 13.4 (d, J(PC) )
66.1 Hz, CH3), 124.9 (d, J(PC) ) 80.0 Hz, Ci-P), 126.4 (s, Cm-
Ph-C), 127.7 (s, CoPh-C), 129.3 (d, J(PC) ) 13.1 Hz, CmPh-
P), 130.0 (s, CpPh-C), 131.0 (d, J(PC) ) 10.4 Hz, CoPh-P),
133.0 (s, CpPh-P), 140.0 (t, J(PC) ) 11.6 Hz, CiPh-C), 179.4
(t, J(PC) ) 6.1 Hz, NCN); mass spectrum (DCI/NH3) m/z 517
NMR {1H} (CDCl3) +20.8; H NMR (CDCl3) 3.63 (d, J(PH)
) 14 Hz, 4 H, CH2), 7.25-8.57 (m, 25 H, Harom); 13C NMR
(CDCl3) 22.0 (dd, J(PC) ) 4.5 and 45.7 Hz, CH2), 125.0 (d,
J(PC) ) 111.5 Hz, Ci-P), 128.3 (s, CmPh-C), 129.6 (d, J(PC)
) 12.9 Hz, CmPh-P), 129.9 (s, CoPh-C), 131.1 (d, J(PC) ) 11.2
Hz, CoPh-P), 132.6 (s, CpPh-C), 133.4 (s, CpPh-P), 138.4 (t,
J(PC) ) 19.8 Hz, CiPh-C), 169.7 (t, J(PC) ) 5.3 Hz, NCN);
mass spectrum (DCI/NH3) m/z 515 (M+ - Br). Anal. Calcd
for C33H29N2P2Br: C, 66.56; H, 4.91; N, 4.70. Found: C,
66.38; H, 4.81; N, 4.52.
Bisadduct 5. The residue was washed several times with
ether-THF (8:2) to give 4.33 g (86% yield) of 5 as a white
powder: mp 133-134 °C; 31P NMR {1H} (CDCl3) -12.6 (d,
1
J(PP) ) 45.4 Hz, P-C), +23.5 (d, J(PP) ) 45.4 Hz, P-N); H
NMR (CDCl3) 1.81 (m, 4 H, CH2), 2.36 (m, 4 H, CH2), 6.86-
7.65 (m, 45 H, Harom); 13C NMR (CDCl3) 19.2 (dd, J(PC) )
28.8 and 5.0 Hz, CH2), 23.1 (dd, J(PC) ) 63.0 and 19.5 Hz,
CH2), 124.2 (d, J(PC) ) 97.2 Hz, CiP-N), 125.8 (s, CmPh-C),
128.7 (d, J(PC) ) 6.3 Hz, CoPh-PN), 129.2 (s, CoPh-C), 129.3
(d, J(PC) ) 5.8 Hz, CmPhP-C), 129.6 (s, CpPhP-C), 130.1 (s,
CpPh-C), 131.2 (d, J(PC) ) 9.6 Hz, CmPhP-N), 132.3 (d, J(PC)
) 18.9 Hz, CoPhP-C), 133.7 (s, CpPhP-N), 135.9 (d, J(PC) )
13.2 Hz, CiPhP-C), 139.9 (t, J(PC) ) 11.6 Hz, CiPh-C), 179.9
(t, J(PC) ) 6.5 Hz, NCN); mass spectrum (DCI/NH3) m/z 913
(M+ - Br). Anal. Calcd for C59H53N2P4Br: C, 71.30 ; H,
5.37 ; N, 2.82. Found: C, 70.86; H, 5.12; N, 2.80.
16-Membered Heterocycle 6. The residue was purified by
flash chromatography on silica gel (96:4 CHCl3-MeOH) to give
1.14 g (75% yield) of 6 as a white powder: mp 201-202 °C;
1
31P NMR {1H} (CDCl3) +21.3; H NMR (CDCl3) 1.25 (m, 4
H, CCH2C), 3.70 (m, 8 H, PCH2), 6.50-8.50 (m, 50 H, Harom);
13C NMR (CDCl3) 22.6-30.0 (m, PCH2CH2CH2), 123.5 (s, Cm-
Ph-C), 125.6 (d, J(PC) ) 86.8 Hz, Ci-P), 126.2 (s, CoPh-C),
128.5 (d, J(PC) ) 4.8 Hz, CmPh-P), 128.6 (s, CpPh-C), 128.7
(d, J(PC) ) 4.4 Hz, CmPh-P), 130.3 (d, J(PC) ) 6.1 Hz, Co-
Ph-P), 130.5 (d, J(PC) ) 4.9 Hz, CoPh-P), 132.5 (s, CpPh-P),
137.4 (t, J(PC) ) 12.8 Hz, CiPh-C), 179.7 (br. t, NCN); mass
spectrum (FAB) m/z 1139 (M+ - Br), 529 (M2+ - 2Br). Anal.

Exchange Reaction of Halodiazirines with Nucleophiles
J. Am. Chem. Soc., Vol. 118, No. 5, 1996 1065
Calcd for C68H62N4P4Br2: C, 67.00; H, 5.13; N, 4.60. Found:
C, 66.18; H, 4.97; N, 4.52.
1 (3.43 g, 17.4 mmol). The solution was stirred for 20 h at
room temperature and analyzed. Benzonitrile and bromotri-
methylstannane were characterized by gas chromatography and
11 by 31P NMR spectroscopy. The solvent was removed under
vacuum, and the oily residue was extracted with pentane (20
mL) leading to a mixture of 11, 12, and 13. Addition of an
ether/pentane solution precipitates 12 and 13. Careful recrys-
tallization at -20 °C from ether allowed first isolation of 13,
then of 12.
Bisadduct 7. The residue was washed several times with
pentane to give 1.52 g (95% yield) of 7 as a brown powder:
1
mp 110-111 °C, 31P NMR {1H} (CDCl3) +11.0; H NMR
(CDCl3) 6.90-7.90 (m, 31 H); 13C NMR (CDCl3) 124.2 (d,
J(PC) ) 111.7 Hz, PCS), 124.8 (d, J(PC) ) 72.5 Hz, Ci-P),
126.7 (d, J(PC) ) 5.8 Hz, PCCC), 128.1 (s, CmPh-C), 129.4
(d, J(PC) ) 12.5 Hz, CmPh-P), 130.0 (s, CoPh-C), 132.2 (s,
CpPh-C), 132.3 (d, J(PC) ) 11.6 Hz, CoPh-P), 133.8 (s, CpPh-
P), 137.5 (d, J(PC) ) 5.5 Hz, SCC), 139.4 (t, J(PC) ) 9.9 Hz,
CiPh-C), 139.8 (d, J(PC) ) 11.7 Hz, PCC), 178.3 (t, J(PC) )
6.5 Hz, NCN); mass spectrum m/z 653 (M+ - Br). Anal. Calcd
for C39H31N2P2S2Br: C, 63.84; H, 4.26; N, 3.82. Found: C,
63.50; H, 4.36; N, 3.87.
Diazaphosphete 12: colorless crystals (1.6 g, 26% yield);
1
mp 136-138 °C; 31P NMR {1H} (CDCl3) +54.2; H NMR
(CDCl3) 1.29 (d, J(HH) ) 6.8 Hz, 24 H, CH3), 3.70 (sept d,
J(HH) ) 6.8 Hz, J(PH) ) 18.3 Hz, 4 H, CH), 7.77 (m, 5 H,
Harom); 13C NMR (CDCl3) 22.1 (s, CH3), 47.2 (d, J(PC) ) 4.3
Hz, CH), 126.6 (s, Cm), 128.2 (s, Co), 130.8 (s, Cp), 136.1 (d,
J(PC) ) 22.4 Hz, Ci), 194.7 (d, J(PC) ) 48.4 Hz, NCN). Anal.
Calcd for C19H33N4P: C, 65.49; H, 9.54; N, 16.08. Found: C,
65.69; H, 9.64; N, 16.34.
Bisadduct 8. The residue was washed several times with
pentane to give 0.58 g (93% yield) of 8 as a yellow oil: 31P
NMR {1H} (CDCl3) +42.4; 1H NMR (CDCl3) 1.37 (dd, J(HH)
) 6.9 Hz, J(PH) ) 0.6 Hz, 12 H, CH3C), 2.64 (d, J(PH) )
10.3 Hz, 24 H, CH3N), 3.31 (sept.d, J(HH) ) 6.9 Hz, J(PH) )
12.8 Hz, 2 H, CHS), 7.33 (m, 5 H, Harom); 13C NMR (CDCl3)
25.3 (d, J(PC) ) 5.8 Hz, CH3C), 36.9 (d, J(PC) ) 3.9 Hz,
CH3N), 37.4 (d, J(PC) ) 2.9 Hz, CHS), 126.0 (s, Cm), 128.1(s,
Co), 129.6 (s, Cp), 141.2 (t, J(PC) ) 13.9 Hz, Ci), 173.3 (t,
J(PC) ) 4.0 Hz, NCN). Anal. Calcd for C21H43N6P2S2Br: C,
43.07; H, 7.40; N, 14.35. Found: C, 42.77; H, 7.15; N, 14.09.
Five-Membered Ring 9. The residue was washed several
times with ether to give 0.12 g (34% yield) of 9 as a white
powder: mp 112-113 °C; 31P NMR {1H} (CDCl3) +28.4; 1H
NMR (CDCl3) 1.34 (d, J(HH) ) 6.8 Hz, 6 H, CH3C), 3.27
(sept.d, J(HH) ) 6.8 Hz, J(PH) ) 9.8 Hz, 1 H, CHS), 7.11-
8.55 (m, 15 H, Harom); 13C NMR (CDCl3) 25.0 (d, J(PC) ) 4.4
Hz, CH3), 39.9 (d, J(PC) ) 2.9 Hz, CHS), 125.5 (d, J(PC) )
112.1 Hz, Ci-P), 128.7 (s, CmPh-C), 129.4 (d, J(PC) ) 39.4
Hz, CmPh-P), 130.0 (s, CoPh-C), 131.2 (d, J(PC) ) 10.3 Hz,
CoPh-P), 133.7 (s, CpPh-C), 133.9 (d, J(PC) ) 18.8 Hz, CiPh-
C), 134.4 (d, J(PC) ) 3.7 Hz, CpPh-P), 167.9 (d, J(PC) ) 10.3
Hz, NCN). Anal. Calcd for C22H22N2PSBr: C, 57.77; H, 4.85;
N, 6.12. Found: C, 58.03; H, 5.08; N, 5.80.
Triazaphosphinine 13: colorless crystals (3% yield); mp
213 °C; 31P NMR {1H} (CDCl3) +35.6; 1H NMR (CDCl3) 1.19
(d, J(HH) ) 6.8 Hz, 24 H, CH3), 3.68 (m, 4 H, CH), 7.00- 8.70
(m, 10 H, Harom); 13C NMR (CDCl3) 22.4 (d, J(PC) ) 1.9 Hz,
CH3), 46.0 (d, J(PC) ) 5.0 Hz, CH), 127.1 (s, Cm), 127.9 (d,
J(PC) ) 2.4 Hz, Co), 130.0 (s, Cp), 139.7 (d, J(PC) ) 16.9 Hz,
Ci), 171.1 (d, J(PC) ) 3.8 Hz, NCN). Anal. Calcd for
C26H38N5P: C, 75.14; H, 9.22; N, 16.85. Found: C, 75.39; H,
9.34; N, 16.80.
Photolysis of Phosphine Azide 15 with Bromotrimethyl-
stannane. A toluene solution (10 mL) of 15 (0.56 g, 2.05
mmol) and bromotrimethylstannane (0.5 g, 2.05 mmol) was
irradiated at 254 nm for 24 h at room temperature. After
evaporation of the solvent and several washings with pentane,
bromo(stannylimino)phosphorane 11 was obtained as a pale
yellow oil: (0.60 g, 60% yield); 31P NMR {1H} (CDCl3) -11.8;
1H NMR (CDCl3) 0.41 (s, J(119SnH) ) 57.6 Hz, J(117SnH) )
55.0 Hz, 9 H, CH3Sn), 1.24 (d, J(HH) ) 6.8 Hz, 12 H, CH3-
CH), 1.31 (d, J(HH) ) 6.8 Hz, 12 H, CH3CH), 3.59 (sept d,
J(HH) ) 6.8 Hz, J(PH) ) 21.0 Hz, 4 H, CH); 13C NMR
(CDCl3) -3.8 (d, J(PC) ) 4.3 Hz, J(119SnC) ) 394.8 Hz, CH3-
Sn), 22.6 (d, J(PC) ) 2.1 Hz, CH3CH), 23.1 (d, J(PC) ) 3.0
Hz, CH3CH), 48.6 (d, J(PC) ) 4.3 Hz, CH).
Bis Adduct 10. An acetonitrile solution of 10 (Br-) and a
stoichiometric amount of KPF6 was stirred for 24 h at room
temperature. After filtration of KBr and evaporation of the
solvent, 10 (PF6-) was recrystallized from a dichloromethane/
ether solution as colorless crystals (0.33 g, 65% yield): mp
163-165 °C; 31P NMR {1H} (CDCl3) +30.2; 1H NMR (CDCl3)
1.20 (d, J(HH) ) 6.9 Hz, 12 H, CH3), 3.00 (sept d, J(HH) )
Acknowledgment. Thanks are due to the CNRS and the
Deutsche Forschungsgemeinschaft for financial support of this
work.
6.9 Hz, J(PH) ) 7.0 Hz, 2 H, SCH), 7.24-7.70 (m, 25 H); 13
C
Supporting Information Available: ORTEP drawing and
tables of crystal and intensity collection data, positional and
thermal parameters, interatomic distances and angles, and least-
squares planes equations for compound 10 (10 pages). This
material is contained in many libraries on microfiche, im-
mediately follows this article in the microfilm version of the
journal, can be ordered from the ACS, and can be downloaded
from the Internet; see any current masthead page for ordering
information and Internet access instructions.
NMR (CDCl3) 25.3 (d, J(PC) ) 4.7 Hz, CH3), 39.4 (d, J(PC)
) 2.5 Hz, SCH), 127.2 (s, CmPh-C), 127.3 (d, J(PC) ) 107.6
Hz, Ci-P), 128.2 (s, CoPh-C), 129.5 (d, J(PC) ) 39.4 Hz, Cm-
Ph-P), 130.6 (s, CpPh-C), 131.7 (d, J(PC) ) 10.8 Hz, CoPh-P),
133.8 (d, J(PC) ) 2.6 Hz, CpPh-P), 139.5 (t, J(PC) ) 13.2 Hz,
CiPh-C), 179.0 (t, J(PC) ) 10.3 Hz, NCN). Anal. Calcd for
C37H39F6N2P3S2: C, 56.77; H, 5.02; N, 3.58. Found: C, 56.85;
H, 5.10; N, 3.50.
Reaction of Bromophenyldiazirine 1 with Bis(diisopro-
pylamino)(trimethylstannyl)phosphine. To a dichloromethane
solution (5 mL) of bis(diisopropylamino)(trimethylstannyl)-
phosphine20 (7.00 g, 17.7 mmol) was added at room temperature
a dichloromethane solution (20 mL) of bromophenyldiazirine
JA9532143
(20) Bender, H. R. G.; Niecke, E.; Nieger, M.; Westermann, W. Z. Anorg.
Allg. Chem. 1994, 620, 1194.