Persistent radical effect in the intramolecular addition of benzylic radicals onto ketenimines: Selective cross-coupling of α-(indol-2-yl)- benzyl radicals with the 1-cyano-1-methylethyl radical

Article abstract of DOI:10.1039/b312930f

The intramolecular addition of benzylic radicals, generated from benzyl phenyl selenides by the action of tris(trimethylsilyl)silane and AIBN or AIBMe, onto neighbouring ketenimine functions is studied. The persistent α-(indol-2-yl)benzyl radicals, resulting from such cyclization processes, undergo cross-coupling with the tert-alkyl radicals arising from the thermal decomposition of the AIBN or AIBMe initiators to give, respectively, 3-(1H-indol-2-yl)propiononitriles 10 or propanoates 14. A rare spiropentacyclic compound 17 containing two indole fragments also resulted from one of these radical reactions. The crystal and molecular structures of 10d and 17 have been solved by X-ray analysis.

Full text of DOI:10.1039/b312930f

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P A P E R
Persistent radical effect in the intramolecular addition of benzylic
radicals onto ketenimines: selective cross-coupling of a-(indol-2-yl)-
benzyl radicals with the 1-cyano-1-methylethyl radical
a
a
a
b
´ ´ ´
Mateo Alajarın, Angel Vidal,* Marıa-Mar Ortın and Delia Bautista
a
´
´
´
Departamento de Quımica Organica, Facultad de Quımica, Universidad de Murcia,
Campus de Espinardo, Espinardo 30100, Murcia, Spain. E-mail: alajarin@um.es,vidal@um.es;
Fax: þ34 968 364149; Tel: þ34 968 367418
b
´
´
Servicio Universitario de Instrumentacion Cientıfica, Universidad de Murcia,
Campus de Espinardo, E-30100, Murcia, Spain. E-mail: dbc@um.es
Received (in Durham, UK) 15th October 2003, Accepted 11th February 2004
First published as an Advance Article on the web 23rd March 2004
The intramolecular addition of benzylic radicals, generated from benzyl phenyl selenides by the action of
tris(trimethylsilyl)silane and AIBN or AIBMe, onto neighbouring ketenimine functions is studied. The
persistent a-(indol-2-yl)benzyl radicals, resulting from such cyclization processes, undergo cross-coupling with
the tert-alkyl radicals arising from the thermal decomposition of the AIBN or AIBMe initiators to give,
respectively, 3-(1H-indol-2-yl)propiononitriles 10 or propanoates 14. A rare spiropentacyclic compound 17
containing two indole fragments also resulted from one of these radical reactions. The crystal and molecular
structures of 10d and 17 have been solved by X-ray analysis.
Introduction
In chemical systems involving both persistent1 (Rꢀ) and
transient (Aꢀ) radical intermediates, formed from the same or
different precursors with equal or nearly equal rates, the
cross-coupling product (R–A) is formed with high selectivity
and usually becomes the main reaction product. These chemi-
cal systems are controlled by the so-called Persistent Radical
Effect (PRE).2 The formation of products such as R–H,
derived from a disproportionation process, or ions (and pro-
ducts arising from them) generated by a redox process between
(Rꢀ) and (Aꢀ) can be expected as well.
Most of the currently known examples of organic and
metal–organic reactions in which the PRE operates were dis-
covered accidentally. However, the selective formation of the
cross-coupling product (R–A) in the radical reactions gov-
erned by the PRE has captured the attention of organic che-
mists. Thus, Studer has recently reported several clever
organic syntheses based on this general principle.3 The PRE
Scheme 1 Intramolecular addition of benzylic radicals, generated
from xanthates, onto ketenimines.
has also found a number of applications in the field of stable
free-radical polymerization.4
We have recently reported the unprecedented addition of
benzylic radicals onto the central carbon atom of a ketenimine
function,5 a process that provided a novel radical-mediated
synthesis of 2-alkylindoles (Scheme 1). Following xanthate
based radical chemistry6 we generated benzylic radicals 2,
which by cyclization followed by a prototropic imine–enamine
equilibrium converted into the persistent tertiary triarylmethyl-
type radicals 3. These (indol-2-yl)(diphenyl)methyl radicals did
not sustain the radical chain sequence. Instead, depending on
the specific conditions used to generate the initial radicals 2,
they underwent reduction to indoles 4 or a redox process fol-
lowed by other transformations of the resulting ions to give
indoles 5, bearing alkoxy or acyloxy substituents on the lateral
chain at C2.
presence of 2,20-azobisisobutyronitrile (AIBN) as radical
initiator.7
Herein we disclose the results obtained in the study of the
intramolecular addition reaction of benzylic radicals onto
C,C-disubstituted ketenimine functions (linked by means of
its nitrogen atom to an ortho-position of the benzene ring),
when the benzylic radicals are generated from benzyl phenyl
selenides by treatment with tris(trimethylsilyl)silane in the pre-
sence of azoalkanes such as AIBN and AIBMe (dimethyl 2,20-
azobisisobutyrate). Under these reaction conditions the radical
cyclizations turned out to be controlled by the Persistent Radi-
cal Effect, giving rise to 3-(1H-indol-2-yl)propiononitriles and
propanoates, resulting from the selective cross-coupling of
persistent a-(indol-2-yl)benzyl radicals with the 1-cyano-1-
methylethyl and the 1-methoxycarbonyl-1-methylethyl radicals
arising from AIBN and AIBMe, respectively.
It is well known that a clean and efficient method for pro-
ducing carbon centered radicals consists on the treatment
of alkyl phenyl selenides with tris(trimethylsilyl)silane in the
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
570
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 5 7 0 – 5 7 7

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Table 1 Ketenimines 9
Results and discussion
R1
R2
R3
Yield (%)
Preparation of ketenimines
Compound
Ketenimines 9 were prepared from 2-azidobenzyl chlorides 6 in
three steps (Scheme 2). Treatment of a solution of diphenyl
diselenide in anhydrous ethanol with sodium borohydride pro-
vided sodium benzeneselenolate, which cleanly reacted with
2-azidobenzyl chlorides 6 leading to the formation of benzyl
phenyl selenides 7. Staudinger reaction8 of azidoselenides 7
with triphenylphosphane, in diethyl ether solution at room
temperature, yielded the triphenylphosphazenes 8. Aza-Wittig
reaction9 of 8 with diphenyl ketene or methyl phenyl ketene, in
dichloromethane solution at room temperature, gave C,C-
diphenyl ketenimines 9a–d or C-methyl-C-phenyl ketenimines
9e,f, respectively (Table 1). Ketenimines 9 are stable com-
pounds which were purified by column chromatography on
silica gel,10 and were fully characterized. Their IR spectra
9a
9b
9c
9d
9e
9f
H
H
Ph
Ph
78
74
59
90
58
57
H
Cl
CH3
H
Ph
Ph
CH3
H
H
H
CH3
CH3
CH3
H
d ¼ 1.50–1.55. Their 13C NMR spectra show the signals due
to the quaternary carbon atoms of the propiononitrile chain
C2 and C3 around d ¼ 38.5 and d ¼ 60.0, respectively. In
these spectra the two methyl groups at C2 also appeared as
diastereotopic d ¼ 26.1–26.4 and d ¼ 27.5–27.6, and the same
occurs for the two phenyl groups at C3. The diastereotopicity
observed at 25 ꢂC (the NMR spectra were recorded at room
temperature) for the methyl and phenyl groups placed on the
propiononitrile chain of 10a–d is presumably due to restricted
rotation around the single bond C2–C3. In the 1H NMR spec-
trum of the propiononitrile 10d, its two CH3–C2 methyl
groups become equivalent at 40 ꢂC.
=
showed the characteristic absorption of the N C C grouping
=
as a very strong band around 2000 cmꢁ1
.
C,C-Diphenyl ketenimines
In our first experiments, the radical cyclization of the C,C-
diphenyl ketenimines 9a–d was carried out by a four-portion
addition of a stoichiometric excess of tris(trimethylsilyl)silane
(3 equiv) and a molar amount11 of AIBN to a 0.01 M solution
of the ketenimines in boiling benzene (Method A, see Experi-
mental). Under these conditions ketenimines 9 were totally
consumed and column chromatography of the final reaction
mixtures allowed the isolation of the 3-(1H-indol-2-yl)propio-
nonitriles 10a–d in moderate yields (Scheme 3) (Table 2). Two
unidentified minor products (less than 10% each) were also
present in the reaction crudes, as evidenced by GC.
An X-ray structure determination of compound 10d
(R1 ¼ CH3 , R2 ¼ H) was definitive for unequivocally estab-
lishing the structure of compounds 10a–d (Fig. 1). The dihe-
dral angles between the mean planes defined by the indole
˚
ring (the mean deviation from plane is 0.0192 A) and the
two phenyl rings at C3 are 89.4ꢂ (C21 to C26) and 80.2ꢂ
(C31 to C36). The cyano group shows a slightly distorted
linear structure [C(4)–C(7)–N(2) 174.2(2)ꢂ].
In the asymmetric unit, molecules of 10d associate through
intermolecular N–Hꢃ ꢃ ꢃN hydrogen bonds [N1–N2 (x ꢁ 1, y, z)
Slight modifications of this experimental procedure for the
conversions 9a–d ! 10a–d, such as variations on the number
of equivalents of tris(trimethylsilyl)silane and AIBN added
to the reaction mixture in each portion (as in Method B, see
below), led us to invariable results, and compounds 10a–d were
always the main reaction products, with no significant varia-
tions of the yields in which these compounds were obtained.
The structural characterization of indoles 10a–d relies on
their analytical and spectroscopic data. In this respect, their
IR spectra display two strong absorptions at 3358–3460
˚
3.067 A], forming chains parallel to the x axis (Fig. 2).
A reasonable mechanistic explanation for the conversion
9 ! 10 is the following: the in situ formed [(CH3)3Si]3Siꢀ radical
should add to the selenium atom of ketenimines 9 to give
PhSeSi[Si(CH3)3]3 and the expected benzylic radical 11, which
then may undergo a 5-exo-dig addition of the radical moiety
onto the central carbon atom of the ketenimine function, fol-
lowed by a prototropic imine–enamine equilibrium favouring
the aromatic indole form 13. This cyclization step is a favour-
able process due to the formation of a stabilized tertiary
triarylmethyl-type radical. The (indol-2-yl)(diphenyl)methyl
radical 13 would finally undergo radical–radical cross-coupling
with the 1-cyano-1-methylethyl radical arising from AIBN to
yield 10 (Scheme 4). The (indol-2-yl)methyl radicals 13, in
which the radical center is attached to the C2 carbon atom
of an indole ring, are new examples of the scarce (heteroaryl)-
methyl type radicals.12
cmꢁ1 and 2224–2229 cmꢁ1 corresponding to the indolic N–H
1
and nitrile C N vibrations, respectively. In the H NMR spec-
=
=
tra of these compounds the indolic NH proton resonates as
a broad singlet at d ¼ 7.93–8.01, and the indole H3 proton
was observed at d ¼ 6.85–6.91. Notoriously, the two methyl
groups at C2 of the propiononitrile chain appeared as diaster-
eotopic at very close chemical shifts d ¼ 1.47–1.51 and
To further illustrate the synthetic potential of these PRE-
controlled radical cyclizations we decided to test the reaction
of ketenimines 9 with tris(trimethylsilyl)silane and some other
azoalkane different from AIBN. With this aim, we selected
dimethyl 2,20-azobisisobutyrate (AIBMe) which has a half-life
time (t1/2) at 80 ꢂC (boiling temperature of benzene) nearly
equal to that of AIBN,13 and accordingly the rate of forma-
tion of the 1-methoxycarbonyl-1-methylethyl radical resulting
Scheme 2 Reagents and conditions: (a) PhSeSePh, NaBH4 , ethanol,
0 ꢂC, then 2-azidobenzyl chloride 6, rt, 3 h; (b) PPh3 , diethyl ether,
Scheme 3 Reagents and conditions: (a) Tris(trimethylsilyl)silane (3
equiv), AIBN (1 equiv), benzene, reflux, 24 h (Method A).
3
rt, 6 h; (c) PhR C
=
C
=
O, dichloromethane, rt, 30 min.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 5 7 0 – 5 7 7
571

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Table 2 3-(1H-Indol-2-yl)propiononitriles 10 from ketenimines 9
Compound
Methoda
R1
R2
Yield (%)
10a
10b
10c
10d
10e
10f
A
A
A
A
B
H
H
40
42
45
54
43
59
H
Cl
CH3
H
CH3
H
H
H
B
CH3
H
a
See text and Experimental section.
from its thermal decomposition should be similar to the rate
of formation of the 1-cyano-1-methylethyl radical coming
from the decomposition of AIBN. Thus, gradual addition
of tris(trimethylsilyl)silane (3 equiv) and AIBMe (1 equiv)
to a 0.01 M solution of ketenimine 9b in boiling benzene
(Method A) afforded the methyl 3-(7-methyl-1H-indol-2-yl)
propanoate 14 in 45% yield (Scheme 5). In this reaction,
the reduced 2-diphenylmethyl-7-methylindole 15 was also
isolated in 21% yield.14
C-Methyl-C-phenyl ketenimines
Next, we submitted C-methyl-C-phenyl ketenimines 9e,f (see
Scheme 1) to reaction with tris(trimethylsilyl)silane in the pre-
sence of AIBN. We wondered if the putative 1-(1H-indol-2-yl)-
1-phenylethyl radicals 16, of the heteroaryl phenyl methyl type,
would be persistent enough to allow cross-coupling with the
transient radical derived from AIBN.
Fig. 2 View of the hydrogen bond interaction in the asymmetric unit
of 10d.
The initial experiments of treating ketenimines 9e,f with
the system tris(trimethylsilyl)silane–AIBN were conducted by
adding in three portions 1.5 equivalents of tris(trimethylsilyl)-
silane and 1.2 equivalents of AIBN to a 0.01 M solution of the
corresponding ketenimine in boiling benzene (Method B).
Under these conditions the reaction products were the
expected 3-(1H-indol-2-yl)-2,2,3-trimethyl-3-phenylpropiono-
nitriles 10e,f (Scheme 6), resulting from the cross-coupling of
the intermediate, persistent radicals 16 and the 1-cyano-1-
methylethyl radical.
The structural assignment of compound 17 was not straight-
forward following its analytical and spectroscopic data and an
X-ray structure determination was accomplished (Fig. 3). This
analysis revealed the spirocyclic nature of compound 17, a par-
ticular dimer of indolylmethyl radical 16e. The diastereoisomer
Compounds 10e,f were obtained in moderate yields after
purification by column chromatography (Table 2), and charac-
terized by their analytical and spectral data, which were essen-
tially similar to those of the analogous 10a–d.
The cyclization of ketenimine 9e was also attempted under
the experimental conditions of Method A. This variation led
to an unexpected result, furnishing the expected propiono-
nitrile 10e (26% yield) but accompanied by the cyclopenta[b]-
indole-1-spiro-20-indoline 17 as the major reaction product
(51%) (Scheme 7).
Fig. 1 Ellipsoid representation of compound 10d with 50% probabil-
ity ellipsoids and the crystallographic labelling scheme.
Scheme 4 Proposed mechanism for the conversion 9 ! 10.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
572
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 5 7 0 – 5 7 7

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Scheme 5 Reagents and conditions: (a) Tris(trimethylsilyl)silane (3
equiv), AIBMe (1 equiv), benzene, reflux, 24 h (Method A).
Scheme 7 Reagents and conditions: (a) Tris(trimethylsilyl)silane (3
equiv), AIBN (1 equiv), benzene, reflux, 24 h (Method A).
shown is the only one present in the crystals and should be also
the only one detected by H NMR analysis of the crude reac-
tion mixture. In consequence, spirocycle 17 was formed in
a highly diastereoselective manner, as only one out of four
possible diastereoisomers is obtained.
To the best of our knowledge, the preparation of the cyclo-
penta[b]indole-1-spiro-20-indoline skeleton has been previously
reported only once in the chemical literature.15
Conclusion
1
In summary, we have shown in this report how ketenimines
undergo intramolecular addition of free carbon-centered
radicals to afford new examples of persistent tertiary radicals
bearing an heteroaromatic ring (indole) at the carbon-
center radical: (indol-2-yl)(diphenyl)methyl and 1-(indol-2-yl)-
1-phenylethyl radicals. These radicals undergo selective
cross-coupling with 1-cyano-1-methylethyl and 1-methoxy-
carbonyl-1-methylethyl radicals, present in the reaction med-
ium, to give respectively 3-(1H-indol-2-yl)propiononitriles and
3-(1H-indol-2-yl)propanoates. The Persistent Radical Effect
controls these radical processes.
Apart from stereochemical considerations, the proposed
mechanism for explaining the conversion 9e ! 17 is depicted
in Scheme 8. The formation of the spiro compound 17 would
start with the coupling of radicals 16e and 19 to give the dimeric
species 20, an indole and an indoline ring linked by a two car-
bon chain via their respective C2 carbon atoms. The nucleophi-
lic attack of the indole moiety through its C3 carbon atom
on the C2 iminic carbon of the indoline fragment would pro-
vide the spiranic intermediate 21, which finally should convert
into the reaction product 17 by an imine–enamine prototropic
equilibrium.
The formation of 17 when ketenimine 9e is submitted to the
reaction conditions of Method A, but not under the conditions
of Method B, should be related to the differences between both
methods concerning the rate of addition of AIBN to the reac-
tion medium. Whereas in Method A only 0.3 equivalents of
AIBN were added after 6 h, in Method B this amount raised
to 0.8 equivalents for the same reaction time, thus increasing
the concentration of 1-cyano-1-methylethyl radical and, conse-
quently, the probability of cross-coupling between 16e and
that radical.
Experimental
All melting points were determined on a Kofler hot-plate melt-
ing point apparatus and are uncorrected. IR spectra were
obtained on a Nicolet Impact 400 spectrophotometer. NMR
spectra were recorded on a Bruker Avance 300 (300 MHz
and 75 MHz for 1H and 13C, respectively) or a Bruker Avance
400 (400 MHz and 100 MHz for H and 13C, respectively) in
CDCl3 as solvent, and the chemical shifts are expressed in
1
Scheme 6 Reagents and conditions: (a) Tris(trimethylsilyl)silane (1.5
equiv), AIBN (1.2 equiv), benzene, reflux, 24 h (Method B).
Fig. 3 Ellipsoid representation of compound 17 with 50% probability
ellipsoids and the crystallographic labelling scheme.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 5 7 0 – 5 7 7
573

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using rigid groups and other hydrogens were refined using a
riding method.
Materials
2-Azidobenzyl chloride 6a,16 2-azido-3-methylbenzyl chloride
6b,17 2-azido-5-chlorobenzyl chloride 6c,17 2-azido-5-methyl-
benzyl chloride 6d,18 methyl phenyl ketene,19 diphenyl ketene20
and dimethyl 2,20-azobisisobutyrate (AIBMe)21 were prepared
by literature procedures.
Preparation of 2-azidobenzyl phenyl selenides 7
An orange solution of diphenyl diselenide (1.56 g, 5 mmol) in
anhydrous ethanol (30 ml) was stirred at 0 ꢂC under an atmo-
sphere of nitrogen. Powdered sodium borohydride (0.47 g, 12.5
mmol) was added in five portions of 0.094 g each. The solution
became colourless when all sodium borohydride was added.
A solution of the corresponding 2-azidobenzyl chloride 6 (10
mmol) in anhydrous ethanol (15 ml) was then added dropwise
over 15 min. The mixture was stirred at room temperature for
3 h, cooled and quenched by addition of 10% hydrochloric
acid (50 ml). The resulting solution was extracted with hexanes
(3 ꢄ 50 ml), and the combined extracts were washed with 10%
hydrochloric acid (50 ml), saturated sodium hydrogen car-
bonate (50 ml) and water (50 ml), and dried over anhydrous
magnesium sulfate. The solvent was removed under reduced
pressure and the residue was purified by short column chroma-
tography (silica gel, using hexanes as eluent).
2-Azidobenzyl phenyl selenide (7a). (2.42 g, 84%); yellow oil
(Found: C, 54.3; H, 3.6; N, 14.3. C13H11N3Se requires C,
54.2; H, 3.85; N, 14.6%); nmax(neat)/cmꢁ1 2124, 1577, 1493,
1450, 1437, 1295, 1023, 756 and 693; dH 4.03 (2 H, s), 6.93
(1 H, td, J ¼ 7.0 and 1.2), 7.03 (1 H, dd, J ¼ 7.7 and 1.8),
7.07 (1 H, dd, J ¼ 7.7 and 1.2), 7.19–7.25 (4 H, m), 7.43–
7.47 (2 H, m); dC 27.4, 118.3, 124.6, 127.6, 128.4, 128.9,
130.1 (s), 130.4 (s), 130.7, 134.3, 138.0 (s).
2-Azido-3-methylbenzyl phenyl selenide (7b). (2.54 g, 84%);
yellow oil (Found: C, 55.3; H, 4.6; N, 14.1. C14H13N3Se
requires C, 55.6; H, 4.3; N, 13.9%); nmax(neat)/cmꢁ1 2103,
1475, 1462, 1437, 1301, 1023, 781, 738 and 692; dH 2.40
(3 H, s), 4.11 (2 H, s), 6.88 (1 H, dd, J ¼ 7.7 and 1.8), 6.93
(1 H, t, J ¼ 7.7), 7.00 (1 H, dd, J ¼ 7.7 and 1.8), 7.18–7.28
(3 H, m), 7.44–7.51 (2 H, m); dC 18.1, 28.7, 125.7, 127.6,
128.4, 129.0, 130.1 (s), 130.4, 132.8 (s), 133.0 (s), 134.2,
136.5 (s).
Scheme 8 Proposed mechanism for the conversion 9e ! 17.
ppm relative to Me4Si at d ¼ 0.00 for 1H and to CDCl3 at
d ¼ 77.1 for 13C. J values are given in Hz. Mass spectra were
recorded on a Hewlett-Packard 5993C spectrometer or on a
VG-Autospec spectrometer. Microanalyses were performed
on a Carlo Erba EA-1108 instrument.
2-Azido-5-chlorobenzyl phenyl selenide (7c). (2.84 g, 88%);
yellow oil (Found: C, 48.1; H, 3.3; N, 13.3. C13H10ClN3Se
requires C, 48.4; H, 3.1; N, 13.0%); nmax(neat)/cmꢁ1 2122,
2083, 1486, 1477, 1300, 1111, 1022, 810, 737 and 690; dH
3.93 (2 H, s), 6.91 (1 H, d, J ¼ 3.0), 6.97 (1 H, d, J ¼ 8.0),
7.17 (1 H, dd, J ¼ 8.0 and 3.0), 7.22–7.28 (3 H, m), 7.41–
7.46 (2 H, m); dC 26.9, 119.4, 128.0, 128.2, 129.0, 129.4 (s),
129.6 (s), 130.5, 132.1 (s), 134.7, 136.5 (s).
X-Ray structure determination
The crystal and molecular structures of compounds 10d and 17
have been determined by X-ray diffraction studies. Crystals
were mounted on glass fibres and transferred to the cold gas
stream of the diffractometer (10d Siemens P4 and 17 Bruker
Smart APEX). Data were recorded with Mo-Ka radiation
2-Azido-5-methylbenzyl phenyl selenide (7d). (2.66 g, 88%);
yellow oil (Found: C, 55.3; H, 4.1; N, 13.7. C14H13N3Se
requires C, 55.6; H, 4.3; N, 13.9%); nmax(neat)/cmꢁ1 2126,
2086, 1495, 1475, 1300, 1241, 1161, 1024, 738 and 694; dH
2.20 (3 H, s), 4.00 (2 H, s), 6.80–6.81 (1 H, m), 6.96 (1 H, d,
J ¼ 8.0), 7.03 (1 H, dd, J ¼ 8.0 and 1.5), 7.20–7.27 (3 H, m),
7.42–7.48 (2 H, m); dC 20.7, 27.4, 118.2, 127.6, 128.9, 129.0,
129.8 (s), 130.2 (s), 131.4, 134.3, 135.1 (s).
˚
(l ¼ 0.71073A) in o-scan mode. Structures were solved by
the direct method and refined anisotropically on F2 (program
SHELXL-97, G. M. Sheldrick, University of Go¨ttingen, Ger-
many). The hydrogens and N were located in the Fourier dif-
ference maps and refined freely. Methyl groups were refined
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
574
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 5 7 0 – 5 7 7

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Preparation of 2-(triphenylphosphoranylideneamino)benzyl
phenyl selenides 8
Preparation of ketenimines 9
To a solution of the corresponding 2-(triphenylphosphoranyli-
deneamino)benzyl phenyl selenide 8 (1.5 mmol) in anhydrous
dichloromethane (20 ml) a solution of methyl phenyl ketene
or diphenyl ketene (1.5 mmol) in the same solvent (5 ml) was
added. After stirring at room temperature for 30 min the sol-
vent was removed under reduced pressure and the resulting
material was chromatographed on a silica gel column, using
hexanes–diethyl ether (9 : 1) as eluent.
To a solution of the corresponding 2-azidobenzyl phenyl sele-
nide 7 (5 mmol) in anhydrous diethyl ether (15 ml) triphenyl-
phosphane (1.31 g, 5 mmol) was added. The reaction
mixture was stirred at room temperature under nitrogen for
6 h. Then, the precipitated compounds 8 were isolated by
filtration.
These compounds were used in the following step without
further purification. For analytical samples, compounds 8 were
recrystallized from diethyl ether.
Ketenimine 9a. (0.51 g, 78%); yellow oil (Found: C, 73.8; H,
4.5; N, 3.1. C27H21NSe requires C, 74.0; H, 4.8; N, 3.2%);
n
1023, 761, 738 and 693; dH 4.32 (2 H, s), 7.10–7.12 (3 H, m),
7.16–7.25 (5 H, m), 7.32–7.39 (9 H, m), 7.44–7.47 (2 H, m);
dC 27.9, 77.3 (s), 123.1, 126.5, 127.4, 127.6, 127.9, 128.3,
128.9, 130.3 (s), 130.6, 134.0, 134.7 (s), 138.7 (s), 189.9 (s).
max(neat)/cmꢁ1 2001, 1600, 1579, 1490, 1486, 1172, 1077,
2-(Triphenylphosphoranylideneamino)benzyl phenyl selenide
(8a). (2.43 g, 93%); mp 140–142 ꢂC; colourless prisms (Found:
C, 71.2; H, 4.8; N, 2.6. C31H26NPSe requires C, 71.3; H, 5.0;
N, 2.7%); nmax(Nujol)/cmꢁ1 1588, 1577, 1436, 1331, 1310,
1109, 1051, 1021, 757, 735, 718 and 691; dH 4.49 (2 H, s),
6.42 (1 H, d, J ¼ 8.0), 6.54 (1 H, td, J ¼ 7.6 and 1.0), 6.76
(1 H, td, J ¼ 7.6 and 1.8), 7.09–7.21 (4 H, m), 7.36–7.56 (11
H, m), 7.73–7.84 (6 H, m); dC 31.3, 117.0, 121.0 (d,
J ¼ 10.1), 126.2, 127.4, 128.6 (d, J ¼ 12.8), 128.7, 129.4 (d,
J ¼ 2.1), 131.2 (d, J ¼ 99.5), 131.6 (d, J ¼ 2.8), 132.5 (s),
132.6, 132.7 (d, J ¼ 9.9), 132.9 (s), 133.5 (s); dP (162.3 MHz;
CDCl3 ; H3PO4) 2.5; m/z (EI) 523 (Mþ, 7%), 366 (100).
Ketenimine 9b. (0.50 g, 74%); yellow oil (Found: C, 74.5; H,
4.9; N, 3.1. C28H23NSe requires C, 74.3; H, 5.1; N, 3.1%);
n
max(neat)/cmꢁ1 2017, 1593, 1495, 1172, 1075, 1023, 999,
760, 737, 694 and 645; dH 2.27 (3 H, s), 4.13 (2 H, s), 6.89
(1 H, dd, J ¼ 7.4 and 1.3), 6.96 (1 H, t, J ¼ 7.4), 7.06 (1 H,
dd, J ¼ 7.4 and 1.3), 7.14–7.22 (5 H, m) 7.28–7.42 (10 H,
m); dC 19.1, 28.9, 73.1 (s), 126.1, 126.2, 127.3, 128.0, 128.2,
128.8, 128.9, 130.0, 130.6 (s), 132.1 (s), 132.5 (s), 134.0, 134.7
(s), 137.5 (s), 185.9 (s).
3-Methyl-2-(triphenylphosphoranylideneamino)benzyl phenyl
selenide (8b). (2.01 g, 75%); mp 114–115 ꢂC; colourless prisms
(Found: C, 71.3; H, 5.2; N, 2.6. C32H28NPSe requires C,
71.6; H, 5.3; N, 2.6%); nmax(Nujol)/cmꢁ1 1588, 1576, 1434,
1186, 1111, 753, 743, 713 and 695; dH 1.86 (3 H, s), 4.04 (2
H, s), 6.56 (1 H, td, J ¼ 7.3 and 2.1), 6.84–6.88 (2 H, m),
7.13–7.17 (3 H, m), 7.27–7.38 (8 H, m), 7.43–7.46 (3 H, m),
7.59–7.66 (6 H, m); dC 21.4, 31.4, 118.6 (d, J ¼ 3.2), 126.2,
127.7 (d, J ¼ 1.9), 128.4 (d, J ¼ 12.1), 128.7, 129.3 (d,
J ¼ 2.8), 131.3 (d, J ¼ 2.9), 132.4 (d, J ¼ 9.6), 132.5, 132.6
(s), 132.7 (s), 132.9 (d, J ¼ 101.5), 133.1 (d, J ¼ 5.2), 147.0
(d, J ¼ 1.4); dP (162.3 MHz; CDCl3 ; H3PO4) 4.6; m/z (EI)
537 (Mþ, 5%), 380 (100).
Ketenimine 9c. (0.42 g, 59%); yellow oil (Found: C, 68.8; H,
4.5; N, 3.1. C27H20ClNSe requires C, 68.6; H, 4.3; N, 3.0%);
n
max(neat)/cmꢁ1 1995, 1596, 1578, 1495, 1476, 1173, 1137,
1103, 1075, 1023, 896 and 819; dH 4.21 (2 H, s), 7.03 (1 H,
d, J ¼ 2.3), 7.14 (1 H, dd, J ¼ 8.4 and 2.3), 7.17–7.25 (6 H,
m), 7.31–7.35 (8 H, m), 7.42–7.45 (2 H, m); dC 27.5, 78.2
(s), 124.2, 126.7, 127.8, 128.0, 128.2, 128.9, 129.0, 129.7 (s),
130.4, 133.0 (s), 133.7 (s), 134.4, 136.6 (s), 137.2 (s), 191.0 (s).
Ketenimine 9d. (0.61 g, 90%); yellow oil (Found: C, 74.6; H,
5.2; N, 3.0. C28H23NSe requires C, 74.3; H, 5.1; N, 3.1%);
n
1141, 1075, 820, 737, 693, 643 and 610; dH 2.23 (3 H, s), 4.27
(2 H, s), 6.92 (1 H, d, J ¼ 2.0), 6.98 (1 H, dd, J ¼ 8.0 and
2.0), 7.15–7.24 (6 H, m), 7.28–7.37 (8 H, m), 7.43–7.47 (2 H,
m); dC 21.1, 27.9, 77.6 (s), 123.0, 126.4, 127.3, 127.8, 128.9,
129.0, 130.4 (s), 131.2, 134.0, 134.2 (s), 134.5 (s), 135.7 (s),
137.7 (s), 189.3 (s).
5-Chloro-2-(triphenylphosphoranylideneamino)benzyl phenyl
selenide (8c). (2.53 g, 91%); mp 159–160 ꢂC; colourless prisms
(Found: C, 66.7; H, 4.8; N, 2.3. C31H25ClNPSe requires C,
66.85; H, 4.5; N, 2.5%); nmax(Nujol)/cmꢁ1 1582, 1436, 1333,
1141, 1111, 1019, 884, 757, 736, 721 and 692; dH 4.39 (2 H,
s), 6.29 (1 H, d, J ¼ 8.5), 6.69 (1 H, dd, J ¼ 8.5 and 2.5),
7.02 (1 H, t, J ¼ 2.1), 7.19–7.20 (3 H, m), 7.40–7.45 (6 H,
m), 7.50–7.53 (5 H, m), 7.73–7.78 (6 H, m); dC 30.8, 121.4
(s), 121.6 (d, J ¼ 10.0), 126.6, 127.0, 128.7 (d, J ¼ 12.1),
128.9, 129.0, 130.9 (d, J ¼ 100.0 Hz), 131.8 (d, J ¼ 2.7),
132.7 (d, J ¼ 9.7), 132.8 (s), 133.0, 134.5 (d, J ¼ 22.3), 148.3
(s); dP (162.3 MHz; CDCl3 ; H3PO4) 3.6; m/z (EI) 402 (48%),
400 (100), 183 (28).
max(neat)/cmꢁ1 1999, 1596, 1580, 1488, 1454, 1436, 1264,
Ketenimine 9e. (0.33 g, 58%); yellow oil (Found: C, 70.5; H,
5.2; N, 3.8. C22H19NSe requires C, 70.2; H, 5.1; N, 3.7%);
n
max(neat)/cmꢁ1 2004, 1600, 1580, 1486, 1437, 1373, 1190,
1065, 1021, 757, 737 and 692; dH 2.12 (3 H, s), 4.33 (2 H, s),
7.07–7.35 (12 H, m), 7.47–4.51 (2 H, m); dC 12.3, 28.1, 67.1
(s), 122.9, 124.5, 125.2, 127.2, 127.4, 128.2, 128.7, 129.0,
130.5, 134.0, 134.2 (s), 135.6 (s), 139.7 (s), 193.8 (s).
5-Methyl-2-(triphenylphosphoranylideneamino)benzyl phenyl
selenide (8d). (2.60 g, 97%); mp 142–144 ꢂC; colourless prisms
(Found: C, 71.7; H, 5.1; N, 2.5. C32H28NPSe requires C,
71.6; H, 5.3; N, 2.6%); nmax(Nujol)/cmꢁ1 1606, 1576, 1438,
1328, 1110, 811, 757, 735, 720 and 695; dH 2.13 (3 H, s), 4.48
(2 H, s), 6.33 (1 H, dd, J ¼ 8.0 and 1.0), 6.57 (1 H, dd,
J ¼ 8.0 and 1.8), 6.95 (1 H, t, J ¼ 2.2), 7.16–7.21 (3 H, m),
7.32–7.56 (11 H, m), 7.73–7.83 (6 H, m); dC 20.5, 31.1, 120.6
(d, J ¼ 9.8), 125.9, 126.0 (s), 127.9, 128.5 (d, J ¼ 12.0),
128.6, 130.1 (d, J ¼ 1.9), 131.3 (d, J ¼ 99.5), 131.5 (d,
J ¼ 2.8), 132.0 (s), 132.4, 132.6 (d, J ¼ 9.7), 133.6 (s), 146.7
(s); dP (162.3 MHz; CDCl3 ; H3PO4) 2.0; m/z (EI) 537 (Mþ,
5%), 380 (100).
Ketenimine 9f. (0.33 g, 57%); yellow oil (Found: C, 70.7; H,
5.1; N, 3.3. C23H21NSe requires C, 70.8; H, 5.4; N, 3.6%);
n
max(neat)/cmꢁ1 2000, 1599, 1579, 1492, 1446, 1380, 1242,
1067, 1026, 827, 758, 735 and 691; dH 2.10 (3 H, s), 2.23 (3
H, s), 4.30 (2 H, s), 6.91–7.00 (2 H, m), 7.07–7.14 (2 H, m),
7.21–7.34 (7 H, m), 7.47–7.51 (2 H, m); dC 12.3, 21.0, 28.0,
67.0 (s), 122.7, 124.4, 125.0, 127.3, 128.7, 128.8, 128.9, 130.6
(s), 131.1, 134.0, 135.8 (s), 136.9 (s), 137.2 (s), 193.1 (s).
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 5 7 0 – 5 7 7
575

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Reaction of ketenimines 9 with tris(trimethylsilyl)silane and
AIBN or AIBMe: preparation of 3-(1H-indol-2-yl)propiono-
nitriles 10 and methyl 3-(1H-indol-2-yl)propanoate 14
3-(5-Methyl-1H-indol-2-yl)-2,2-dimethyl-3,3-diphenylpropio-
nonitrile (10d). Method A (0.15 g, 54%); mp 181–183 ꢂC
(dichloromethane–diethyl ether); colourless prisms (Found: C,
85.9; H, 6.4; N, 7.5. C26H24N2 requires C, 85.7; H, 6.6; N,
7.7%); nmax(Nujol)/cmꢁ1 3460, 2229, 1601, 1585, 1496, 1448,
1315, 1266, 1165, 806, 742 and 710; dH 1.51 (3 H, s), 1.55 (3 H,
s), 2.47 (3 H, s), 6.85 (1 H, s), 7.00 (1 H, d, J ¼ 8.2), 7.13 (1 H, d,
J ¼ 8.2), 7.19–7.20 (1 H, m), 7.29–7.34 (6 H, m), 7.43 (1 H, s),
7.66–7.68 (3 H, m), 7.93 (1 H, br s); dC 21.5, 26.4, 27.6, 38.6
(s), 60.0 (s), 104.7, 110.7, 120.3, 124.0, 127.5, 127.6, 127.9,
128.5, 129.3 (s), 129.7, 131.2, 134.6 (s), 140.0 (s), 140.8 (s),
142.8 (s); m/z (EI) 364 (Mþ, 5%), 296 (100).
Method A. A solution of the corresponding ketenimine 9
(0.75 mmol) in anhydrous benzene (75 ml) was heated under
nitrogen at reflux temperature and tris(trimethylsilyl)silane
(0.28 g, 1.125 mmol) and AIBN (0.025 g, 0.15 mmol) were
added. Further additions of tris(trimethylsilyl)silane and
AIBN were made as follows: 1) after 3 h since the first addi-
tion, AIBN (0.012 g, 0.075 mmol), 2) after 6 h since the first
addition, tris(trimethylsilyl)silane (0.093 g, 0.375 mmol) and
AIBN (0.025 g, 0.15 mmol) and 3) after 9 h since the first addi-
tion, tris(trimethylsilyl)silane (0.19 g, 0.75 mmol) and AIBN
(0.061 g, 0.375 mmol). After 15 h since the last addition the
solvent was removed under reduced pressure and the crude
residue was chromatographed on a silica gel column, using
hexanes–diethyl ether (9 : 1) as eluent.
Crystal data: C26H24N2 , M ¼ 364.47, monoclinic,
˚
a ¼ 7.6460(10), b ¼ 21.303(2), c ¼ 12.5050(10) A, U ¼
3
˚
1968.6(4) A , T ¼ 173(2) K, space group P2(1)/n, Z ¼ 4,
absorption coefficient ¼ 0.071 mmꢁ1, 3892 reflections mea-
sured, 3457 unique (Rint ¼ 0.0219) which were used in all
calculations. The final wR(F2) was 0.0882 (all data).y
Method B. A solution of the corresponding ketenimine 9
(0.75 mmol) in anhydrous benzene (75 ml) was heated under
nitrogen at reflux temperature and tris(trimethylsilyl)silane
(0.23 g, 0.94 mmol) and AIBN (0.050 g, 0.3 mmol) were added.
Further additions of tris(trimethylsilyl)silane and AIBN were
made as follows: 1) after 3 h since the first addition, tris(tri-
methylsilyl)silane (0.047 g, 0.19 mmol) and AIBN (0.050 g,
0.3 mmol) and 2) after 6 h since the first addition, AIBN
(0.050 g, 0.3 mmol). After 15 h since the last addition the
solvent was removed under reduced pressure and the crude
residue was chromatographed on a silica gel column, using
hexanes–diethyl ether (9 : 1) as eluent.
3-(1H-Indol-2-yl)-2,2,3-trimethyl-3-phenylpropiononitrile (10e).
Method B (0.093 g, 43%); mp 133–135 ꢂC (from diethyl ether);
colourless prisms (Found: C, 83.6; H, 6.9; N, 9.4. C20H20N2
requires C, 83.3; H, 7.0; N, 9.7%); nmax(Nujol)/cmꢁ1 3348,
2239, 1446, 1400, 1350, 1294, 1101, 1031, 804, 740 and 705;
dH 1.46 (3 H, s), 1.48 (3 H, s), 1.91 (3 H, s), 6.80 (1 H, d,
J ¼ 2.0), 7.00–7.15 (2 H, m), 7.17–7.25 (1 H, m), 7.27–7.41
(5 H, m), 7.56–7.68 (1 H, m), 7.81 (1 H, br s); dC 23.4, 24.7,
24.8, 38.9 (s), 49.4 (s), 102.9, 110.7, 120.0, 120.5, 121.5 (s),
122.1, 125.8 (s), 127.6, 128.2, 129.0, 135.8 (s), 141.5 (s); m/z
(EI) 288 (Mþ, 12%), 220 (100).
3-(5-Methyl-1H-indol-2-yl)-2,2,3-trimethyl-3-phenylpropio-
nonitrile (10f). Method B (0.13 g, 59%); mp 150–152 ꢂC (from
diethyl ether); colourless prisms (Found: C, 83.6; H, 7.0; N,
9.2. C21H22N2 requires C, 83.4; H, 7.3; N, 9.3%);
3-(1H-Indol-2-yl)-2,2-dimethyl-3,3-diphenylpropiononitrile
(10a). Method A (0.11 g, 40%); mp 227–229 ꢂC (from dichloro-
methane); colourless prisms (Found: C, 85.9; H, 6.1; N, 7.8.
C25H22N2 requires C, 85.7; H, 6.3; N, 8.0%); nmax(Nujol)/
cmꢁ1 3376, 2224, 1600, 1298, 1161, 795, 751, 743 and 705;
dH 1.48 (3 H, s), 1.52 (3 H, s), 6.91 (1 H, s), 7.01–7.16 (4 H,
m), 7.21 (1 H, d, J ¼ 7.8), 7.30–7.34 (5 H, m), 7.60–7.65 (4
H, m), 7.97 (1 H, br s); dC 26.3, 27.6, 38.5 (s), 59.9 (s), 105.0,
111.0, 120.0, 120.7, 122.4, 127.3 (s), 127.5, 127.6, 128.0,
128.5, 129.6, 131.2, 136.2 (s), 139.8 (s), 140.7 (s), 142.7 (s);
m/z (EI) 350 (Mþ, 63%), 278 (100).
n
max(Nujol)/cmꢁ1 3393, 2240, 1586, 1460, 1411, 1315, 1295,
1176, 1031, 807, 734 and 704; dH 1.45 (3 H, s), 1.48 (3 H, s),
1.91 (3 H, s), 2.44 (3 H, s), 6.71 (1 H, d, J ¼ 1.8), 6.98 (1 H,
dd, J ¼ 8.1 and 1.3), 7.13 (1 H, d, J ¼ 8.1 Hz), 7.24–7.40 (6
H, m), 7.71 (1 H, br s); dC 21.5, 23.5, 24.7, 24.8, 38.9 (s),
49.5 (s), 102.6, 110.4, 120.2, 123.7, 125.8 (s), 127.6, 127.9 (s),
128.2, 129.0, 129.3 (s), 134.1 (s), 141.6 (s); m/z (EI) 302 (Mþ,
29%), 234 (100).
Methyl 3-(7-methyl-1H-indol-2-yl)-2,2-dimethyl-3,3-diphenyl-
propanoate (14). Method A (0.13 g, 45%); mp 187–189 ꢂC
(from chloroform–n-hexane); colourless prisms (Found: C,
81.4; H, 6.6; N, 3.6. C27H27NO2 requires C, 81.6; H, 6.85; N,
3.5%); nmax(Nujol)/cmꢁ1 3299, 1697, 1500, 1355, 1268, 1221,
1135, 807, 751 and 709; dH 1.30 (3 H, s), 1.56 (3 H, s), 2.50
(3 H, s), 3.66 (3 H, s), 6.15 (1 H, d, J ¼ 2.1), 6.96–7.01 (4 H,
m), 7.15–7.27 (8 H, m), 7.36–7.39 (1 H, m), 11.17 (1 H, s);
dC 16.8, 27.1, 28.0, 52.8, 53.0 (s), 61.2 (s), 108.2, 117.9,
119.4, 120.5 (s), 122.0, 126.4 (s), 126.9, 127.1, 127.3, 128.1,
128.7, 130.2, 136.1 (s), 142.2 (s), 144.4 (s), 145.4 (s), 180.9
(s); m/z (EI) 397 (Mþ, 6%), 296 (100).
3-(7-Methyl-1H-indol-2-yl)-2,2-dimethyl-3,3-diphenylpropio-
nonitrile (10b). Method A (0.11 g, 42%); mp 197–198 ꢂC (from
chloroform–n-hexane); colourless prisms (Found: C, 85.9; H,
6.3; N, 7.7. C26H24N2 requires C, 85.7; H, 6.6; N, 7.7%);
n
max(Nujol)/cmꢁ1 3452, 2229, 1598, 1441, 1289, 1161, 813,
745 and 703; dH 1.47 (3 H, s), 1.51 (3 H, s), 2.30 (3 H, s),
6.89–7.06 (3 H, m), 7.19–7.34 (8 H, m), 7.46 (1 H, d,
J ¼ 7.6), 7.63–7.67 (2 H, m), 7.98 (1 H, br s); dC 16.4, 26.1,
27.5, 38.4 (s), 59.9 (s), 105.5, 118.3, 120.1 (s), 120.3, 122.9,
126.7 (s), 127.5, 127.7 (s), 127.9, 128.4, 128.5, 129.6, 131.3,
135.9 (s), 139.9 (s), 140.4 (s), 142.7 (s); m/z (EI) 364 (Mþ,
5%), 296 (100).
Cyclopenta[b]indole-1-spiro-20-indoline 17. Method A (0.084
g, 51%); mp 264–265 ꢂC (chloroform–n-hexane); colourless
prisms (Found: C, 87.4; H, 6.3; N, 6.2. C32H28N2 requires C,
87.2; H, 6.4; N, 6.4%); nmax(Nujol)/cmꢁ1 3422, 1610, 1599,
1332, 1305, 1193, 1163, 1032, 967, 853, 777, 751 and 702; dH
1.34 (3 H, s), 1.39 (3 H, s), 3.22 (1 H, d, J ¼ 17.5), 3.31
(1 H, d, J ¼ 17.5), 4.20 (1 H, s), 6.27 (1 H, s), 6.39 (1 H, d,
J ¼ 7.7), 6.66 (1 H, t, J ¼ 7.4), 6.91 (1 H, d, J ¼ 7.4)
6.97–7.06 (3 H, m), 7.12–7.16 (2 H, m), 7.24–7.26 (9 H, m),
3-(5-Chloro-1H-indol-2-yl)-2,2-dimethyl-3,3-diphenylpropio-
nonitrile (10c). Method A (0.13 g, 45%); mp 198–200 ꢂC (from
chloroform–n-hexane); colourless prisms (Found: C, 78.3; H,
5.3; N, 7.2. C25H21ClN2 requires C, 78.0; H, 5.5; N, 7.3%);
n
max(Nujol)/cmꢁ1 3358, 2227, 1601, 1577, 1391, 1160, 1062,
877, 797, 736 and 698; dH 1.47 (3 H, s), 1.50 (3 H, s), 6.85 (1
H, s), 7.09–7.13 (3 H, m), 7.30–7.35 (6 H, m), 7.56–7.63 (4
H, m), 8.01 (1 H, br s); dC 26.3, 27.6, 38.5 (s), 60.0 (s), 104.7,
112.0, 120.1, 122.7, 125.7 (s), 127.4 (s), 127.7, 128.1, 128.4
(s), 128.6, 129.6, 131.1, 134.5 (s), 139.6 (s), 142.3 (s), 142.5
(s); m/z (EI) 386 (Mþ þ 2, 10%), 384 (Mþ, 27), 318 (45), 316
(100).
y CCDC reference numbers 223156 and 223157. See http://
www.rsc.org/suppdata/nj/b3/b312930f/ for crystallographic data in
.cif or other electronic format.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
576
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 5 7 0 – 5 7 7

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(b) S. Z. Zard, Angew. Chem., Int. Ed., 1997, 36, 672–685; (c) B.
Quiclet-Sire and S. Z. Zard, Phosphorus, Sulfur Silicon, 1999,
153–154, 137–154.
(a) For the generation of radicals from phenyl selenides and tris
(trimethylsilyl)silane–AIBN see: M. Ballestri, C. Chatgilialoglu,
K. B. Clark, D. Griller, B. Giese and B. Kopping, J. Org. Chem.,
1991, 56, 678–683; (b) C. Chatgilialoglu, Acc. Chem. Res., 1992,
25, 188–194.
H. Staudinger and J. Meyer, Helv. Chim. Acta, 1919, 2, 635–646.
(a) For examples of aza-Wittig reactions between phosphazenes
and ketenes see: P. Molina, M. Alajar´ın, A. Vidal, J. Fenau-
Dupont and J. P. Declerq, J. Org. Chem., 1991, 56, 4008–4016;
´
(b) P. Molina, M. Alajarın, A. Vidal and C. Foces-Foces, Tetra-
hedron, 1995, 51, 12 127–12 142; (c) P. Molina, A. Vidal and F.
7.67–7.79 (1 H, m); dC 19.3, 24.8, 41.0, 51.9 (s), 65.4 (s), 90.0
(s), 94.4, 107.6, 111.8, 118.6, 120.0, 121.0, 121.1, 123.9, 126.3
(s), 126.9, 127.4, 127.6, 127.7, 128.0, 128.6, 128.7, 130.5 (s),
133.4 (s), 142.3 (s), 146.2 (s), 147.9 (s), 148.9 (s); m/z (EI)
440 (Mþ, 7%), 220 (100).
7
Crystal data: C32H28N2 , M ¼ 440.56, triclinic, a ¼
˚
A,
10.1741(8),
b ¼ 10.6139(9),
c ¼ 11.3542(9)
U ¼
3
˚
¯
8
9
1137.81(16) A , T ¼ 100(2) K, space group P1, Z ¼ 2, absorp-
tion coefficient ¼ 0.075 mmꢁ1, 12 460 reflections measured,
4621 unique (Rint ¼ 0.0337) which were used in all calculations.
The final wR(F2) was 0.1065 (all data).y
´
Tovar, Synthesis, 1997, 963–966; (d ) M. Alajarın, P. Molina, A.
Vidal and F. Tovar, Tetrahedron, 1997, 53, 13 449–13 472; (e)
Acknowledgements
´
M. Alajarın, A. Vidal, F. Tovar, A. Arrieta, B. Lecea and F. P.
Cossıo, Chem. Eur. J., 1999, 5, 1106–1117; ( f ) F. P. Cossıo, A.
´
´
This work was supported by the MCYT and FEDER (Project
´
BQU2001-0010), and Fundacion Seneca-CARM (Project PI-
1/00749/FS/01). One of us (M.-M. O.) thanks the Fundacion
´
Arrieta, B. Lecea, M. Alajarın, A. Vidal and F. Tovar, J. Org.
Chem., 2000, 65, 3633–3643; (g) M. Alajarın, A. Vidal, F. Tovar,
´
´
´
M. C. Ramirez de Arellano, F. P. Cossıo, A. Arrieta and B. Lecea,
J. Org. Chem., 2000, 65, 7512–7515; (h) M. Alajarın, A. Vidal, F.
´
´
´
Seneca-CARM for a fellowship.
Tovar and C. Conesa, Tetrahedron Lett., 1999, 40, 6127–6130; (i)
M. Alajar´ın, A. Vidal and F. Tovar, Tetrahedron Lett., 2000, 41,
´
7029–7032; ( j) M. Alajarın, A. Vidal and M.-M. Ortın, Synthesis,
2002, 2393–2398; (k) M. Alajarın, A. Vidal, F. Tovar and P.
´
´
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T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 5 7 0 – 5 7 7
577