Phospha-Michael-type reactions between 1,2-diaza-1,3-dienes and bidentate nucleophiles: Formation of new mono- and diylides and their elaboration to heterocycles

Article abstract of DOI:10.1002/ejoc.201001453

Phospha-Michael additions of a series of methylene-bridged phosphorus bidentate nucleophiles to 1,2-diaza-1,3-dienes gave monoadducts and bisadducts in high yields under mild conditions. In particular, a series of new ylides and symmetrical diylides have been obtained from bis(diphenyl)phosphanes. The use of diphenylphosphanylamino derivatives gave, through phospha-Michael addition, ylide intermediates that underwent spontaneous intramolecular attack by the amino group belonging to the Michael donor reagent moiety, thus giving access to new heterocycles.

Full text of DOI:10.1002/ejoc.201001453

FULL PAPER
DOI: 10.1002/ejoc.201001453
Phospha-Michael-Type Reactions between 1,2-Diaza-1,3-dienes and Bidentate
Nucleophiles: Formation of New Mono- and Diylides and their Elaboration to
Heterocycles
Carla Boga,*[a] Nicola Zanna,[a] Orazio A. Attanasi,[b] Graziano Baccolini,[a]
Lucia De Crescentini,[b] Luciano Forlani,[a] Fabio Mantellini,[b] Simona Nicolini,[b]
Gabriele Micheletti,[a] and Silvia Tozzi[a]
Keywords: Phosphanes / Phosphorus heterocycles / Ylides / Michael addition
Phospha-Michael additions of a series of methylene-bridged
phosphorus bidentate nucleophiles to 1,2-diaza-1,3-dienes
gave monoadducts and bisadducts in high yields under mild
conditions. In particular, a series of new ylides and symmetri-
cal diylides have been obtained from bis(diphenyl)phos-
phanes. The use of diphenylphosphanylamino derivatives
gave, through phospha-Michael addition, ylide intermedi-
ates that underwent spontaneous intramolecular attack by
the amino group belonging to the Michael donor reagent
moiety, thus giving access to new heterocycles.
Regioselective nucleophilic attack at the terminal carbon
atom in the 4-position of the heterodiene system of a DD
occurs with a variety of carbon nucleophiles and hetero-
nucleophiles such as oxygen, nitrogen, sulfur, selenium and
phosphorus nucleophiles, giving the corresponding hydraz-
ones.[6] In particular, when electron-withdrawing groups are
present on the terminal carbon and/or nitrogen atoms,
Michael-like additions give highly functionalized hydraz-
ones, which are potential starting materials for further
structural modifications through controlled regioselective
reactions leading to new heterocyclic systems.[6]
Previously, some of us examined phospha-Michael reac-
tions between DDs and different phosphorus nucleophiles.
In particular, new pyrazoles or pyrazol-5-ones were ob-
tained from the reactions between DDs and triphenylphos-
phane[8] or trialkylphosphanes,[9] whereas with trialkyl
phosphites[10] or dialkylphenylphosphonites[11] under sol-
vent-free conditions the reactions gave new 1,2,3-diaza-
phospholes or (E)-hydrazono-phosphonates in high yields.
Furthermore, the use of phosphoramidites, phosphorodi-
amidites or tris(dimethylamino)phosphanes gave stable α-
phosphoranylidene-hydrazones, which were in turn trans-
formed into the corresponding phosphoranylidene pyrazole
derivatives.[12] All of these reactions occur under very mild
conditions and involve, as key step, the spontaneous forma-
tion of ylide intermediates from the zwitterionic adducts
formed by 1,4-Michael-type attack on DDs. This ease of
the preparation of such ylides under neutral and mild con-
ditions prompted us to explore the reactivity of DDs with
diphosphane derivatives. Such reactions are of interest for
several reasons. Diylides are a class of compounds useful in
various fields of chemistry,[13] and have attracted increasing
interest in coordination chemistry.[13,14] To the best of our
Introduction
The Michael addition is one of the most useful and ver-
satile methods in synthetic organic chemistry for the forma-
tion of C–C bonds under mild conditions.[1] Classical exam-
ples of this reaction are to be found in the 1,4-additions of
doubly stabilized carbon nucleophiles such as β-keto esters,
malonates or β-cyanoesters to α,β-unsaturated carbonyl
compounds. However, the importance of this class of conju-
gate additions in organic synthesis is not limited to the for-
mation of C–C bonds. In fact, a wide number of variants
both in the nucleophilic component (Michael donor) and
in the electrophilic one (Michael acceptor) allow the pro-
duction of a series of carbon-heteroatom bonds, such as
carbon–sulfur, carbon–nitrogen, carbon–oxygen or carbon–
phosphorus, through the so-called sulfa-,[2] aza-,[3] oxa-,[4]
or phospha-[5]Michael reactions, respectively. The last of
these is one of the most important tools for the formation
of the P–C bond, which is often present in a wide number
of compounds of great interest in synthetic, applied and
biological chemistry.
Of the non-classical Michael electrophilic partners, 1,2-
diaza-1,3-dienes (DDs) represent a very interesting class of
compounds in view of their particular reactivity due to the
electron-withdrawing effect of the azo group in the hetero-
diene system, which makes these compounds good Michael
acceptors.[6,7]
[a] Department of Organic Chemistry A. Mangini, Alma Mater
Studiorum – University of Bologna,
Viale del Risorgimento 4, 40136 Bologna, Italy
Fax: +39-051-2093654
E-mail: boga@ms.fci.unibo.it
[b] Istituto di Chimica Organica, Università degli Studi di Urbino
“Carlo Bo”,
Via I Maggetti 24, 61029 Urbino, Italy
1326
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Phospha-Michael-Type Reactions
knowledge, however, only a few examples of preparations appearance of the typical red colour of the starting DD
of diylides has been reported so far. In particular, the route indicated the completion of the reaction, which was also
1
to symmetrical diylides through the classical approach in- monitored through H and 31P NMR spectroscopy.
volving the deprotonation of bisphosphonium salts with
The reactions were carried out with different relative mo-
bases is often a crucial step[15] and sometimes alternative lar ratios of the reagents, as reported below.
procedures have been developed.[14c,15a,16]
i. Reactions Carried Out with Equimolar Amounts of the
DDs 1a or 1b and the Diphosphanes 2a–d
In view of these considerations, we investigated reactions
between a series of methylene-bridged diphosphanes and
DDs under neutral conditions. Here we report the results
obtained, which showed the efficiency of our approach as
a route to a new class of symmetrical diylide compounds.
In addition, we extended the investigation through the use
of methylene-bridged phosphanylamine derivatives with the
same DDs. This latter set of reactions produced new ylide
intermediates that could in turn be elaborated into new het-
erocycles.
The reaction between equimolar amounts of compound
1a and DPPM (2a) in ethyl acetate gave, after a few min-
utes, formation of a white solid. After filtration, this solid
was analysed and found to be pure compound 3a, recovered
in about 50% yield. When 1b was treated with 2a in ethyl
acetate, no solid was formed. In each of these two cases a
mixture of the starting reagent 2a, the monoylide (3a or 3e)
and the diylide (4a or 4e) was recovered from the solution.
The reactions between the DDs 1a or 1b and DPPM (2a)
were also carried out directly in NMR tubes in CDCl3 and
monitored through 1H and 31P NMR spectroscopy: in these
cases, no precipitate was formed and the corresponding
mono adducts 3a or 3e were obtained in nearly quantitative
yield.
White solids also precipitated from the reactions between
equimolar amounts of 1a or 1b and the higher homologous
diphosphanes 2b–d in ethyl acetate, but in these cases their
spectroscopic data agreed with the structures of the corre-
sponding diadducts 4. When the reactions between the DDs
1a or 1b and the phosphanes 2b–d were carried out in de-
uteriochloroform, no precipitates were formed and the
monoylides 3b–d and 3f–h were obtained in higher yields,
although in mixtures with the corresponding diadducts 4
(see Exp. Section).
Results and Discussion
We studied the reactivities of the DDs 1a and 1b towards
two kinds of bidentate donor reagents: bis(diphenyl)phos-
phanes [Scheme 1, namely bis(diphenylphosphanyl)meth-
ane (DPPM, 2a), bis(diphenylphosphanyl)ethane (DPPE,
2b), bis(diphenylphosphanyl)propane (DPPP, 2c) and bis-
(diphenylphosphanyl)butane (DPPB, 2d)], and (diphenyl-
phosphanyl)amines [Scheme 3, below, such as 2-(diphenyl-
phosphanyl)ethanamine (5a) and 3-(diphenylphosphanyl)-
propan-1-amine (5b)]. For purposes of clarity, the associ-
ated results are discussed separately under the subheadings
below.
From these data it can be deduced that the solubility of
the ylide 3a in ethyl acetate is lower than that of all the
other mono-ylides, it being, under the same experimental
Reactions between the 1,2-Diaza-1,3-dienes 1a and 1b and
the Bis(diphenylphosphanes) 2a–d
The reactions between the DDs 1a and 1b and the bis(di- conditions, the sole monoadduct recovered by precipitation
phenylphosphanes) 2a–d (Scheme 1) were carried out at from the reaction mixture. On the other hand, the poor
room temperature in ethyl acetate or in chloroform; the dis- solubility in ethyl acetate shown by the bis adducts 4b–h
Scheme 1. Reactions between the DDs 1a and 1b and the bis(diphenylphosphanes) 2a–d.
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C. Boga et al.
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(see the following section) causes their almost immediate of the nitrogen on the phosphorus of the phosphonium salt
precipitation from the solution, thus increasing the conver- through a pathway (route a) already hypothesized for sim-
sion from the monoadduct to the bis adduct. On the basis ilar reactions,[10] and the other derived from a 1,4-hydrogen
of these data, in an attempt to isolate the monoylide deriva- shift (route b) favoured by the high acidity of the hydrogen
tives 3b–h, we carried out the reactions in chloroform (in atom bound to the carbon in the α-position both to the
which the diylides are highly soluble) and we tried to sepa- phosphorus and to the ester group.
rate the products by column chromatography. In spite of
different attempts made with changes to the workup condi-
tions, we were not able to isolate compounds 3b–h, which
were instead characterized by 1H and 31P NMR by carrying
out the reaction directly in the NMR tube (see Exp. Sec-
tion).
ii. Reactions Carried Out with the DDs 1a or 1b and the
Diphosphanes 2a–d in a 2:1 Relative Molar Ratio
The reactions between the DDs 1a or 1b and the di-
phosphanes 2a–d in 2:1 relative molar ratio in ethyl acetate
gave, after about 15 min, the stable compounds 4a–h in al-
most quantitative yields. As might be expected on the basis
of the findings reported above (see subheading i), their low
solubilities in ethyl acetate permitted them to be obtained
as pure solids from the reaction mixtures by simple fil-
tration. In this context, it should be noted that on carrying
out the reactions in ethyl acetate under the same concentra-
tion conditions for each DD/diphosphane pair, the yields
of products 4a–d (see Exp. Section) recovered by filtration
were almost double those found for the corresponding
products 4e–h, thus suggesting that the presence of the
NHPh end group in the DDs moiety increases the solubili-
Scheme 2. Simplified possible reaction pathways for the first attack
of the diphosphanes on the DDs.
It is interesting to note that A-1 is a cyclic pentacoordi-
ties of these diylides. Compound 4a was also obtained by nate phosphorus species. Because it is known that such cy-
addition of DD 1a to an equimolar amount of pure 3a, clic species are more stable than acyclic ones by factors of
obtained as described in the above section.
about 106,[18] the formation of the intermediate A-1 could
The ylide structures of the Michael-like monoadducts not be excluded a priori. The absence, in the 1H NMR spec-
and bis adducts are supported by their IR, H, 13C and 31P trum (also when recorded at –70 °C) of the signal corre-
1
NMR and mass spectroscopic data. However, it is interest- sponding to the proton in the position α to the carboxy
ing to make some comments from both the structural and group, however, together with the 31P NMR chemical shifts
the mechanistic points of view. For simplicity, only the for- of the reaction products (which fall far from the range typi-
mation of the ylide 3a, chosen as an example, is discussed cal of pentacoordinate phosphorus species[19]), permitted
extensively.
easy discrimination between structures A-1 and 3 in favour
Zwitterionic forms such as Zw-1 (Scheme 1) are probably of the ylide structures 3. In particular, the 31P NMR spec-
formed first, through phospha-Michael addition of one trum of compound 3a in CDCl3 at 25 °C shows a pair of
phosphorus atom of the diphosphinic nucleophile 2 to one doublets at δ = 19.8 ppm (JP,P = 61.8 Hz) and δ =
molecule of the DD. With the aim of acquiring information –27.3 ppm (JP,P = 61.8 Hz), indicative of a PIVCPIII se-
on the involved intermediates, we carried out the reaction quence (the first signal belongs to a tetracoordinate phos-
between equimolar amounts of 1a and DPPM (3a) directly phorus atom whereas the second is due to a tricoordinate
in the NMR tube in CD2Cl2 at –70 °C. Although zwitter- phosphorus atom, with a δ value very close to that of the
ionic intermediates derived from the interaction of tertiary starting phosphane 2a). In the case of the formation of an
phosphanes with compounds containing activated C=C A-1-like species, the 31P NMR signal of the corresponding
bonds have sometimes been isolated,[17] under our experi- pentacoordinate phosphorus atom would be expected at
mental conditions no evidence of the species Zw-1, bearing higher field (negative δ values).
a hydrogen atom bound to the carbon in the α-position to
Analogous considerations can be made with regard to
the phosphorus, to the ester and to the hydrazone groups, the diadducts obtained from the diphosphanes 2a–d and
1
was obtained by H NMR spectroscopy.
two molecules of the DDs. Also in these cases, many inter-
An intermediate such as Zw-1, once formed, is very mediates might be expected. However, the presence in each
probably immediately converted into more stable neutral case of a single signal in the 31P NMR spectrum (δ values
structures. In principle, two different neutral structures around +20 ppm in CDCl3 at 25 °C) gives a clear indication
could reasonably be expected from Zw-1 (Scheme 2): one of the nature and the symmetry of the environment of each
of them (A-1) derived from an internal nucleophilic attack phosphorus atom. The significant shifts towards low-field
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Phospha-Michael-Type Reactions
frequencies relative to the free diphosphanes 2 indicate the
presence of the bis-ylides 4, and this was also confirmed by
1H and 13C NMR spectroscopy. Consequently, one can in-
fer that a Zw-like intermediate is a very short-lived species
that immediately undergoes a shift of the proton positioned
α to three electron-withdrawing groups, a shift furthermore
favoured by the presence of the negative charge on the ni-
trogen atom, as previously observed in analogous sys-
tems.[6,20]
Finally, we wish to focus attention on an interesting fea-
ture found during the NMR monitoring of the course of
the reaction between 1a and 2a in CD2Cl2 under variable-
temperature NMR conditions. Immediately after the ad-
dition of compound 2a to a solution of 1a, cooled to
–70 °C, the 31P NMR spectrum showed, together with a
small amount of 2a (δP = –23.5 ppm), two pairs of doublets,
at +22.8 and –28.8 ppm (JP,P ≈ 62 Hz) and +20.3 and
Scheme 3. Reaction between the aminophosphanes 5a or 5b and
the DD 1a.
–27.4 ppm (JP,P ≈ 61 Hz) indicating the presence of two spe- a new stable product, the spectroscopic data for which are
cies. The corresponding 1H NMR spectrum recorded at the consistent with structure 7a. When the reaction between 1a
same temperature (see the Exp. Section) confirmed the pres- and 5a in 2:1 relative molar ratio was carried out in CDCl3,
ence of two compounds in 65:35 relative ratio. On raising the 1H NMR spectrum of the crude reaction mixture
the temperature, both the 31P and the 1H NMR spectra showed only the presence of compound 6a and of the start-
remained unchanged until –50 °C. Above –50 °C the signals ing DD, thus suggesting that the expected aza-Michael ad-
showed line broadening and coalescence was reached at dition between 6a and 1a does not occur under our experi-
–35 °C. A further increase in the temperature caused a mental conditions; the formation of cyclic compound 7a
gradual sharpening of the signals until a final averaged situ- with time was also observed in this case.
ation, in which the spectra matched those of the ylide prod-
The cyclization of 6b to the cyclic seven-membered com-
uct 3a. It is noteworthy that the dynamic process observed pound 7b proved less selective than that observed for 6a. In
is reversible: after warming of the solution from –70 °C to fact, compound 6b, when kept in chloroform solution, was
1
room temperature and cooling again to –70 °C, 31P and H slowly converted into a mixture of products: among them
NMR spectra identical to the starting one were obtained, we were able to identify and to isolate compound 7b and
thus suggesting the existence of two rotamers at low tem- the pyrazole derivative 8. The structure of 8 was ascertained
peratures. By application of the Eyring equation,[21] these by comparison of its spectral properties with those of an
data permitted us to calculate an activation energy of ΔG# authentic sample prepared as already described.[8]
= (11.2Ϯ0.2) kcalmol–1 for the process, a value consis-
The new heterocycles 2,3-dihydro-1-aza-4-phosphinine
tent[20,22] with that of a rotational constraint due, in this (7a) and 5,6-dihydro-1-aza-4-phosphepine (7b) proved
case, to the bulky groups present on compound 3a, which stable and might be of interest in both synthetic and applied
make the molecule quite rigid. It is reasonable to suppose fields.[25] The spontaneous formation of these new heterocy-
that this phenomenon occurs in all compounds 3 and 4.
cles 7a and 7b from the precursors 6a and 6b is probably
due to an internal nucleophilic attack of the amine nitrogen
atom of 6 on the iminic carbon atom[26] with displacement
of a molecule of semicarbazide through a pathway analo-
gous to that recently reported.[27] Obviously, given that the
cyclization step from 6 to 7 implies the loss of the semicar-
Reactions between the 1,2-Diaza-1,3-dienes 1a or 1b and
the Diphenylphosphanylamines 5a or 5b
It is known that DDs react with amines to give aza- bazide terminal group of the starting reagent 6, the same
Michael-like addition,[23] and so different products might in product 7 can be obtained by starting from both 1a and 1b,
principle be expected from the reactions between the phos- thus making it profitless to carry out the reaction with the
phoamino derivatives 5a or 5b and the 1,2-diaza-1,3-diene DD 1b as starting reagent.
1a (Scheme 3). Besides the phospha-Michael-like addition,
an aza-Michael-like addition or even a tandem phospha- adducts 6a and 6b is different from that observed for the
aza-Michael[24] double addition might also occur.
ylides 3, derived from reactions of the diphosphanes 2a–d.
It is interesting to note that the behaviour of the ylide
In the current case, when the reactions between equi- In fact, whereas the adducts 3 each undergo addition of a
molar amount of 1a and 5a or 5b were carried out at room second molecule of the DD to give the diadducts 4, in the
temperature in ethyl acetate (or in chloroform), the only case of the ylides 6a and 6b obtained from the DD 1a and
products obtained were compounds 6a or 6b (Scheme 3). the aminophosphanes 5a and 5b, intramolecular attack by
The structures of these adducts were ascertained by 1H, 13C, the amino nitrogen atom to give new heterocyclic species is
31P and g-HSQC NMR analyses. Compound 6a, kept in preferred over the aza-Michael addition of this amino
CDCl3 solution, had quantitatively converted after 1 d into group with a second molecule of 1a or 1b.
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C. Boga et al.
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diphosphanes 2, the ylides 3 and the diylides 4 in about 40:40:20
relative molar ratios. When the reactions between compounds 2b–
d and 1a (or 1b) were carried out in chloroform, no solid precipi-
tates were observed and the ylides 3b–d and 3f–h were obtained in
higher yields than in the cases of the reactions carried out in ethyl
acetate, but always in mixtures with the starting phosphanes 2 and
the corresponding diylides 4 (about 60:40 molar ratios between 3
and 4). All attempts to isolate 3b–h by chromatography, even on
changing the elution solvents and the stationary phase (silica gel,
Conclusions
In conclusion, the reactions between 1,2-diaza-1,3-dienes
and bidentate nucleophiles gave new phospha-Michael ad-
ducts in high yields and under mild conditions. In particu-
lar, the use of a series of methylene-bridged bis(diphenyl-
phosphanyl) derivatives gave access to new ylides and sym-
metrical diylides whereas (diphenylphosphanyl)amino de-
rivatives produced ylide intermediates that were spontane-
ously converted into new six- and seven-membered hetero-
cycles.
1
aluminium oxide), failed. For these reasons the H and 31P NMR
spectroscopic data for compounds 3b–h were obtained by carrying
out the reactions between the DD (1a or 1b, 0.05 mmol) and the
diphosphane 2 (0.05 mmol), dissolved in CDCl3 (1 mL), directly in
the NMR tube.
Reactions Carried out under VT-NMR Conditions: The reaction be-
tween 1a (0.019 g, 0.1 mmol) and 2a (0.019 g, 0.05 mmol) was car-
ried out in CD2Cl2 (1.0 mL) in the NMR tube and monitored by
both 1H and 31P NMR spectroscopy from –70 °C to 25 °C. As
reported in the main text, at –70 °C two new species were detected
in about 65:35 relative % ratio; their spectroscopic data are as fol-
lows.
Experimental Section
1
General: H, 13C and 31P NMR spectra were recorded with Varian
Inova 600, Varian Mercury 400 or Varian Inova 300 instruments.
Chemical shifts are referenced to TMS for H NMR in CDCl3, to
1
the solvent for 13C NMR and for 1H NMR in CD2Cl2, and to
external standard 85% H3PO4 for 31P NMR spectroscopy. J values
are given in Hz. All signals assigned to NH protons disappeared
after addition of D2O. In some cases the signal corresponding to
CONH2 hydrogen atoms has not been described because of its
probable overlap with that of traces of water present in the CDCl3.
Multiplicity was assigned by means of DEPT experiments. ESI-MS
spectra were obtained with a WATERS 2Q 4000 instrument. IR
spectra were recorded in CHCl3 with a Perkin–Elmer mod. 1600
FT-IR spectrophotometer. IR spectra of compounds 3 and 4 con-
tain typical signals corresponding to ester (ca. 1830 cm–1) and
amido groups (ca. 1695 and 1599 cm–1) and to P=C bonds (ca.
1246 cm–1); melting points were determined with a Büchi 535 appa-
ratus in open capillary tubes and are uncorrected. Air- and moist-
ure-sensitive solutions and reagents were handled in dried appara-
tus under dry argon by standard Schlenk-type techniques. The
starting phosphanes 2a–d, 5a and 5b are commercially available
materials; ethyl 3-[(aminocarbonyl)diazenyl]but-2-enoate (1a) and
ethyl 3-[(anilinocarbonyl)diazenyl]but-2-enoate (1b) were synthe-
sized as previously reported[28] as E/Z mixtures in variable relative
ratio, depending on the structure.
1
Minor species: H NMR (600 MHz, CD2Cl2, –70 °C): δ = 0.43 (t,
J = 6.6 Hz, 3 H, OCH2CH3), 2.01 (s, 3 H, CH3C), 3.37 (br. s, 2
H), 3.43 (br. d, J = 12.5 Hz, 2 H, OCH2CH3), 4.76 (br. s, 1 H,
NH), 6.07 (br. s, 2 H, NNH), 7.14–7.70 (m, 20 H, Harom) ppm. 31P
2
NMR (162 MHz, CD2Cl2, –70 °C): δ = +22.8 (d, JP,P ≈ 62 Hz,
2
Ph2P=C), –28.8 [d, JP,P ≈ 62 Hz, CH2P(Ph)2] ppm.
1
Major species: H NMR (600 MHz, CD2Cl2, –70 °C): δ = 1.09 (t,
J = 6.7 Hz, 3 H, OCH2CH3), 1.98 (s, 3 H, CH3C), 3.58 (d, J =
12.0 Hz, 2 H), 3.73 (br. q, J = 6.3 Hz, 2 H, OCH2CH3), 4.65 (br.
s, 1 H, NH), 6.07 (br. s, 2 H, NNH), 7.14–7.70 (m, 20 H,
Harom) ppm. 31P NMR (162 MHz, CDCl3, 25 °C): δ = +20.3 (d,
2
2JP,P ≈ 61 Hz, Ph2P=C), –27.4 [d, JP,P ≈ 61 Hz, CH2P(Ph)2] ppm.
At –70 °C in the solution there was a small amount of starting
reagents that gradually decreased until disappearing at 25 °C,
showing only the presence of 3a in the solution. The recovery of
3a in quantitative yield under these conditions prompted us also to
carry out the reaction between 1a or 1b and the diphosphanes 2b–
d at low temperature, but in these cases mixtures of ylides and
diylides were obtained.
Synthesis of the Ylides 3a–h: A solution of 1a (0.092 g, 0.5 mmol)
in ethyl acetate (5 mL) was slowly added dropwise to a magnetically
stirred solution of the diphosphane 2a (0.19 g, 0.5 mmol) dissolved
in ethyl acetate. After about 15 min at room temperature, the red
colour of the DD had disappeared and a solid had precipitated.
This solid, collected by filtration and fully characterized, proved to
Ethyl 3-[(Aminocarbonyl)hydrazono]-2-[[(diphenylphosphanyl)meth-
yl](diphenyl)phosphoranylidene]butanoate (3a): White solid, m.p.
88–93 °C. 1H NMR (600 MHz, CDCl3, 25 °C): δ = 0.94 (t, J =
2
7.1 Hz, 3 H, OCH2CH3), 2.06 (s, 3 H, CH3C), 3.56 (d, JH,P
=
be the ylide 3a (0.142 g, 50%) in up to 98% purity. The filtrate 13.9 Hz, 2 H, PCH2P), 3.84 (q, J = 7.1 Hz, 2 H, OCH2CH3), 4.03–
contained a mixture of starting materials and compounds 3a and
4a. From compound 2a and the DD 1b in ethyl acetate, no solid
was formed and a mixture of the starting reagent 2a, the monoylide
3e and the diylide 4e was recovered in the solution. The same reac-
tions were carried out in CDCl3 directly in the NMR tube and
5.02 (br. s, 2 H, CONH2), 6.82 (br. s, 1 H, NH), 7.22–7.28 (m, 2
H, Harom), 7.28–7.30 (m, 2 H, Harom), 7.32–7.39 (m, 8 H, Harom),
7.41–7.48 (m, 4 H, Harom), 7.63–7.69 (m, 4 H, Harom) ppm. 13C
NMR (150 MHz, CDCl3, 25 °C): δ = 14.6 (s, OCH2CH3), 17.8 (d,
1
1
3JC,P = 6.6 Hz, CH3CN), 27.5 (dd, JC,P = 61.4, JC,P = 60.7 Hz,
1
1
3
monitored through H and 31P NMR spectroscopy: in these cases
PCH2P), 52.9 (dd, JC,P = 120.7, JC,P = 2.9 Hz, C=P), 58.2 (s,
1
2
no precipitate was formed and the only signals observed immedi-
ately after the addition of the reagents were those of the starting
reagents (1a, 1b and 2a) and of the mono adducts 3a and 3e in
about 40:60 relative % molar ratio; with time this ratio changed
until reaching, after about 60 min, 5:95. From the reactions be-
tween the diphosphanes 2b–d and the DDs 1a or 1b in ethyl acetate,
solids were separated from the solutions, but in these cases they
OCH2CH3), 127.9 (d, JC,P = 89.3 Hz, P=C), 128.5 (t, JC,P
=
3.8 Hz, PCCH), 131.5 (dd, 1JC,P = 94.3, 3JC,P = 1.9 Hz, P–C), 132.4
3
5
(dd, JC,P
= 9.3, JC,P = 3.5 Hz, PCCHCH), 132.8 (s,
PCCHCHCH), 132.9 (dd, 3JC,P = 20.2, 5JC,P = 4.0 Hz, PCCHCH),
2
133.0 (s, PCCHCHCHCH), 151.6 (d, JC,P = 5.1 Hz, C=N), 157.3
(s, CONH2), 169.6 (d, JC,P = 16.1 Hz, COOEt) ppm. 31P NMR
2
2
(162 MHz, CDCl3, 25 °C): δ = –27.3 [d, JP,P = 61.8 Hz, CH2P-
1
2
proved to be the diylides 4b–h. The H and 31P NMR analysis of
(Ph)2], +19.76 (d, JP,P = 61.80 Hz, Ph2P=C) ppm. MS (ES+): m/z
the contents of the solutions recovered after filtration of com-
pounds 4 showed the presence of mixtures containing the starting
= 570 [M + H]+. C32H33N3O3P2 (569.57): calcd. C 67.48, H 5.84,
N 7.38; found C 67.57, H 5.86, N 7.36.
1330
www.eurjoc.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 1326–1334

Phospha-Michael-Type Reactions
Ethyl 3-[(Aminocarbonyl)hydrazono]-2-{[2-(diphenylphosphanyl)eth- 1.97–2.06 (m, 2 H, CH2P), 2.54–2.70 (m, 2 H, CH2P=), 4.01 (q, J
yl](diphenyl)phosphoranylidene}butanoate (3b): 1H NMR (600
MHz, CDCl3, 25 °C): δ = 0.94 (t, J = 7.0 Hz, 3 H, OCH2CH3),
1.79 (s, 3 H, CH3C), 2.15–2.23 (m, 2 H, Ph2PCH2), 2.63–2.71 (m,
2 H, Ph2PCH2CH2P=C), 3.92 (q, J = 7.0 Hz, 2 H, OCH2CH3),
4.42–4.60 (br. s, 2 H, CONH2), 7.05 (br. s, 1 H, NH), 7.23–7.60
(m, 20 H, Harom) ppm. 31P NMR (162 MHz, CDCl3, 25 °C): δ =
= 7.0 Hz, 2 H, OCH2CH3), 6.80 (d, J = 7.8 Hz, 2 H, Harom), 6.91
(t, J = 8.3 Hz, 1 H, Harom), 7.13 (t, J = 7.8 Hz, 2 H, Harom), 7.27–
7.40 (m, 20 H, Harom) ppm. 31P NMR (242.8 MHz, CDCl3, 25 °C):
δ = –17.1 (s, CH2PPh2), 21.8 (s, P=C) ppm.
Synthesis of Diylides 4a–h – General Procedure: A solution of a DD
(1a or 1b, 1 mmol) in ethyl acetate (5 mL) was added dropwise to
a solution of a diphosphane 2 (0.5 mmol) dissolved in ethyl acetate
(5 mL for 2a, 15 mL for 2b and 2c, 25 mL for 2d). The solution
3
3
–11.5 [d, JP,P = 47.4 Hz, CH2P(Ph)2], 22.8 (d, JP,P = 47.4 Hz,
Ph2P=C) ppm.
Ethyl
3-[(Aminocarbonyl)hydrazono]-2-{[3-(diphenylphosphanyl)- was magnetically stirred at room temperature. After about 15 min
the red colour of the DD had disappeared and a solid had precipi-
propyl](diphenyl)phosphoranylidene}butanoate (3c): 1H NMR
(600 MHz, CDCl3, 25 °C): δ = 1.01 (t, J = 7.0 Hz, 3 H, OCH2CH3), tated. This solid, collected by filtration and fully characterized,
2.06 (s, 3 H, CH3C), 2.09 (t, J = 8.0 Hz, 2 H, PCH2CH2CH2P), proved to be the diylide 4 in about 100% purity. The remaining 4
2.17–2.21 (m, 2 H, Ph2PCH2CH2CH2P=C), 2.73–2.81 (m, 2 H, was recovered by concentration of the mother liquor. When the
PCH2CH2CH2P=C), 3.92 (q, J = 7.0 Hz, 2 H, OCH2CH3), 4.19–
4.81 (br. s, 2 H, CONH2), 6.95 (br. s, 1 H, NH), 7.27–7.61 (m, 20
reaction was carried out in CDCl3 in the NMR tube [the DD
(0.1 mmol
) and the diphosphane 2 (0.05 mmol) in CDCl3
H, Harom) ppm. 31P NMR (162 MHz, CDCl3, 25 °C): δ = –17.3 [d, (1.0 mL)], the only product detected in the solution was the diylide
4
4JP,P = 2.0 Hz, CH2P(Ph)2], 21.3 (d, JP,P = 2.0 Hz, Ph2P) ppm.
4.
Diethyl 1,13-Diamino-4,10-dimethyl-1,13-dioxo-6,6,8,8-tetraphenyl-
2,3,11,12-tetraaza-6λ5,8λ5-diphosphatrideca-3,5,8,10-tetraene-5,9-di-
carboxylate (4a): White solid, m.p. 149–152 °C, quantitative yield
Ethyl
3-[(Aminocarbonyl)hydrazono]-2-{[4-(diphenylphosphanyl)-
butyl](diphenyl)phosphoranylidene}butanoate (3d): 1H NMR
(600 MHz, CDCl3, 25 °C): δ = 1.02 (t, J = 7.0 Hz, 3 H, OCH2CH3),
1.61–1.70 (m, 4 H, PCH2CH2CH2CH2P), 1.99–2.04 (m, 2 H,
Ph2PCH2CH2CH2P=C), 2.14 (s, 3 H, CH3C), 2.53–2.63 (m, 2 H,
PCH2CH2CH2P=C), 3.97 (q, J = 7.0 Hz, 2 H, OCH2CH3), 4.29–
5.00 (br. s, 2 H, CONH2), 7.01 (br. s, 1 H, NH), 7.28–7.47 (m, 20
H, Harom) ppm. 31P NMR (162 MHz, CDCl3, 25 °C): δ = –15.8 (s,
Ph2PCH2CH2CH2P=C), 21.3 (s, Ph2PCH2CH2CH2P=C) ppm.
1
(0.20 g, 54% by filtration). H NMR (400 MHz, CDCl3, 25 °C): δ
= 1.02 (t, J = 7.0 Hz, 6 H, OCH2CH3), 1.84 (s, 6 H, CH3C), 3.64
(q, J = 7.0 Hz, 4 H, OCH2CH3), 4.03–4.50 (br. s, 4 H, CONH2),
5.07 (t, 2JH,P = 16.1 Hz, 2 H, PCH2P), 7.01 (br. s, 2 H, NH), 7.40–
7.48 (m, 8 H, Harom), 7.50–7.58 (m, 4 H, Harom), 7.66–7.75 (m, 8
H, Harom) ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ = 14.5 (s,
3
1
OCH2CH3), 18.5 (t, JC,P = 3.4 Hz, CH3CN), 21.7 (t, JC,P
=
Ethyl 3-[(Anilinocarbonyl)hydrazono]-2-{[(diphenylphosphanyl)meth-
yl](diphenyl)phosphoranylidene}butanoate
(600 MHz, CDCl3, 25 °C): δ = 0.98 (t, J = 7.0 Hz, 3 H, OCH2CH3),
2.12 (s, 3 H, CH3C), 3.60 (d, JH,P = 14.1 Hz, 2 H, PCH2P), 3.88
(q, J = 7.0 Hz, 2 H, OCH2CH3), 6.90 (br. s, 1 H, NNH), 6.91–6.95
(m, 2 H, Harom), 7.15 (t, J = 7.7 Hz, 2 H, Harom), 7.20–7.34 (m, 10
H, Harom), 7.35 (dt, J = 7.7, J = 2.8 Hz, 4 H, Harom), 7.41–7.56 (m,
3 H, Harom), 7.72 (dd, J = 7.4, J = 12.4 Hz, 4 H, Harom) ppm. 31P
NMR (242.8 MHz, CDCl3, 25 °C): δ = –27.4 (d, JP,P = 61.8 Hz,
CH2PPh2), 20.1 (d, JP,P = 61.8 Hz, P=C) ppm.
1
3
57.3 Hz, PCH2P), 50.72 (dd, JC,P = 124.7, JC,P = 2.4 Hz, C=P),
58.2 (s, OCH2CH3), 126.3 (d, JC,P = 94.8 Hz, PC), 128.5 (t, JC,P
= 6.5 Hz, PCCH), 132.0 (t, JC,P = 5.3 Hz, PCCHCH), 132.2 (s,
(3e):
1H
NMR
1
2
3
2
2
PCCHCHCH), 150.3 (t, JC,P = 2.3 Hz, C=N), 157.8 (s, CONH2),
169.6 (t, JC,P = 8.9 Hz, COOEt) ppm. 31P NMR (162 MHz,
2
CDCl3, 25 °C): δ = 17.67 ppm. MS (ES+): m/z = 755 [M + H]+,
777 [M + Na]+, 793 [M + K]+. C39H44N6O6P2 (754.75): calcd. C
62.06, H 5.88, N 11.13; found C 62.14, H 5.89, N 11.10.
2
2
Diethyl 1,14-Diamino-4,11-dimethyl-1,14-dioxo-6,6,9,9-tetraphenyl-
2,3,12,13-tetraaza-6λ5,9λ5-diphosphatetradeca-3,5,9,11-tetraene-
5,10-dicarboxylate (4b): White solid, m.p. 167–169 °C, 0.35 g (91%)
Ethyl 3-[(Anilinocarbonyl)hydrazono]-2-{[2-(diphenylphosphanyl)eth-
yl](diphenyl)phosphoranylidene}butanoate (3f): 1H NMR (600 MHz,
CDCl3, 25 °C): δ = 1.01 (t, J = 7.0 Hz, 3 H, OCH2CH3), 2.23 (s, 3
H, CH3C), 2.24–2.29 (m, 2 H, Ph2PCH2), 2.66–2.74 (m, 2 H,
CH2P=C), 3.98 (q, J = 7.0 Hz, 2 H, OCH2CH3), 6.78–6.83 (m, 2
H, Harom), 6.90–6.94 (m, 2 H, Harom and NH), 7.10–7.15 (m, 2 H,
Harom), 7.24–7.34 (m, 10 H, Harom), 7.36–7.55 (m, 6 H, Harom),
7.58–7.63 (m, 4 H, Harom) ppm. 31P NMR (242.8 MHz, CDCl3,
1
by filtration. H NMR (600 MHz, CDCl3, 25 °C): δ = 0.86 (t, J =
6.9 Hz, 6 H, OCH2CH3), 2.18 (s, 6 H, CH3C), 3.81 (q, J = 6.9 Hz,
4 H, OCH2CH3), 4.55–4.64 (m, 4 H, PCH2CH2P), 4.80–5.45 (br. s,
4 H, CONH2), 7.27 (br. s, 2 H, NH), 7.39–7.45 (m, 6 H, Harom),
7.45–7.51 (m, 6 H, Harom), 7.51–7.58 (m, 8 H, Harom) ppm. 13C
NMR (151 MHz, CDCl3, 25 °C): δ = 14.5 (s, OCH2CH3), 17.8 (t,
1
3JC,P = 2.9 Hz, CH3CN), 20.7 (t, JC,P = 31.3 Hz, PCH2CH2P),
3
3
25 °C): δ = –11.4 (d, JP,P = 49.1 Hz, CH2PPh2), 23.5 (d, JP,P
49.1 Hz, P=C) ppm.
=
50.3 (d, 1JC,P = 118.2 Hz, C=P), 58.2 (s, OCH2CH3), 127.4 (d, 1JC,P
2
3
= 89.7 Hz, PC), 129.3 (t, JC,P = 6.2 Hz, PCCH), 131.6 (t, JC,P
=
Ethyl
3-[(Anilinocarbonyl)hydrazono]-2-{[3-(diphenylphosphanyl)-
4.7 Hz, PCCHCH), 132.3 (s, PCCHCHCH), 151.7 (br. s, C=N),
propyl](diphenyl)phosphoranylidene}butanoate (3g): 1H NMR
(600 MHz, CDCl3, 25 °C): δ = 1.02 (t, J = 7.0 Hz, 3 H, OCH2CH3),
1.56–1.66 (m, 1 H, CHCH2P), 1.71–1.79 (m, 1 H, CHCH2P), 1.81
(s, 3 H, CH3C), 2.16–2.22 (m, 2 H, CH2P), 2.74–2.82 (m, 2 H,
CH2P=), 3.96 (q, J = 7.0 Hz, 2 H, OCH2CH3), 6.83 (d, J = 8.0 Hz,
2 H, Harom), 6.92 (t, J = 7.1 Hz, 1 H, Harom), 7.05 (br. s, 1 H, NH),
7.13 (t, J = 8.0 Hz, 2 H, Harom), 7.28–7.56 (m, 20 H, Harom) ppm.
31P NMR (242.8 MHz, CDCl3, 25 °C): δ = –17.4 (s, CH2PPh2),
21.9 (s, P=C) ppm.
2
157.6 (s, CONH2), 169.6 (t, JC,P = 7.9 Hz, COOEt) ppm. 31P
NMR (162 MHz, CDCl3, 25 °C): δ = 22.64 ppm. MS (ES+): m/z =
769 [M + H]+, 791 [M + Na]+, 807 [M + K]+. C40H46N6O6P2
(768.78): calcd. C 62.49, H 6.03, N 10.93; found C 62.53, H 6.04,
N 10.91.
Diethyl 1,15-Diamino-4,12-dimethyl-1,15-dioxo-6,6,10,10-tetraphen-
yl-2,3,13,14-tetraaza-6λ5,10λ5-diphosphapentadeca-3,5,10,12-tetra-
ene-5,11-dicarboxylate (4c): White solid, m.p. 166–168 °C, 0.365 g
1
(93%) by filtration. H NMR (400 MHz, CDCl3, 25 °C): δ = 0.96
Ethyl
3-[(Anilinocarbonyl)hydrazono]-2-{[4-(diphenylphosphanyl)- (t, J = 7.0 Hz, 6 H, OCH2CH3), 1.77 (d, J = 1.2 Hz, 2 H,
PCH2CH2CH2P), 2.05 (s, 6 H, CH3C), 2.68–2.75 (m, 4 H,
butyl](diphenyl)phosphoranylidene}butanoate (3h): 1H NMR
(600 MHz, CDCl3, 25 °C): δ = 1.07 (t, J = 7.0 Hz, 3 H, OCH2CH3), PCH2CH2CH2P), 3.89 (q, J = 7.0 Hz, 4 H, OCH2CH3), 4.20–4.70
1.47–1.78 (m, 4 H, PCH2CH2 CH2CH2P), 1.88 (s, 3 H, CH3C), (br. s, 4 H, CONH2), 7.02 (s, 2 H, NH), 7.43–7.47 (m, 8 H, Harom),
Eur. J. Org. Chem. 2011, 1326–1334
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1331

C. Boga et al.
FULL PAPER
7.49–7.57 (m, 12 H, Harom) ppm. 13C NMR (150 MHz, CDCl3,
PCCH) ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ = 14.7 (s,
2
3
1
25 °C):
δ
=
14.6 (s, OCH2CH3), 16.5 (d, JC,P
=
2.3 Hz,
OCH2CH3), 17.8 (t, JC,P = 3.6 Hz, CH3CN), 22.2 (d, JC,P =
3
1
1
PCH2CH2CH2P), 17.8 (d, JC,P = 6.9 Hz CH3CN), 28.2 (dd, JC,P 27.3 Hz, PCH2CH2P), 50.8 (d, JC,P = 118.0 Hz, C=P), 58.4 (s,
= 77.7, JC,P = 16.3 Hz, PCH2CH2CH2P), 50.9 (d, JC,P
118.6 Hz, C=P), 58.2 (s, OCH2CH3), 127.5 (d, JC,P = 88.8 Hz, P–
C), 129.0 (d, JC,P = 12.2 Hz, PCCH), 131.9 (d, JC,P = 9.3 Hz,
3
1
=
OCH2CH3), 118.5 (s, CONHCCH), 122.6 (s, CONHCCHCHCH),
1
1
127.0 (d, JC,P = 89.3 Hz, P–C), 128.8 (s, CONHCCHCH), 129.4
2
3
3
2
(t, JC,P = 6.1 Hz, PCCHCH), 131.9 (t, JC,P = 4.8 Hz, PCCH),
2
PCCHCH), 132.1 (s, PCCHCHCH), 151.6 (br. s, C=N), 157.7 (s, 132.6 (s, PCCHCHCH), 138.3 (s, CONHC), 151.2 (t, JC,P
=
2
CONH2), 169.5 (d, JC,P = 17.0 Hz, COOEt) ppm. 31P NMR 2.4 Hz, C=N), 153.0 (s, CONH), 171.3 (s, COOEt) ppm. 31P NMR
(162 MHz, CDCl3, 25 °C): δ = 21.3 ppm. MS (ES+): m/z = 783 [M (162 MHz, CDCl3, 25 °C): δ = 23.6 Hz ppm. MS (ES+): m/z = 921
+ H]+, 805 [M + Na]+. C41H48N6O6P2 (782.80): calcd. C 62.91, H [M + H]+, 943 [M + Na]+. C52H54N6O6P2 (920.97): calcd. C 67.82,
6.18, N 10.74; found C 62.88, H 6.16, N 10.71. H 5.91, N 9.13; found C 67.80, H 5.93, N 9.10.
Diethyl 1,16-Diamino-4,13-dimethyl-1,16-dioxo-6,6,11,11-tetraphen- Diethyl 1,15-Dianilino-4,12-dimethyl-1,15-dioxo-6,6,10,10-tetra-
yl-2,3,14,15-tetraaza-6λ5,11λ5-diphosphahexadeca-3,5,11,13-tetra- phenyl-2,3,13,14-tetraaza-6λ5,10λ5-diphosphapentadeca-3,5,10,12-
ene-5,12-dicarboxylate (4d): White solid, m.p. 184–186 °C, 0.37 g
(93%) by filtration, H NMR (600 MHz, CDCl3, 25 °C): δ = 0.91
tetraene-5,11-dicarboxylate (4g): White solid, m.p. 178 °C (dec.),
quantitative yield (0.21 g, 46% by filtration). H NMR (600 MHz,
1
1
(t,
J
=
7.0 Hz,
6
H, OCH2CH3), 1.45–1.53 (m,
4
H,
CDCl3, 25 °C): δ = 1.01 (t, J = 7.0 Hz, 6 H, OCH2CH3), 1.86–1.94
PCH2CH2CH2CH2P), 2.18 (s, 6 H, CH3C), 2.51–2.60 (m, 4 H, (m, 2 H, PCH2CH2CH2P), 2.12 (s, 6 H, CH3C), 2.73 (m, 4 H,
PCH2CH2CH2CH2P), 3.88 (q, J = 7.0 Hz, 4 H, OCH2CH3), 4.08–
5.05 (br. s, 4 H, CONH2), 7.45 (dt, JH,H = 7.4, JH,P = 2.7 Hz, 8
PCH2CH2CH2P), 3.94 (q, J = 7.0 Hz, 4 H, OCH2CH3), 6.80 (d, J
7.8 Hz, H, CONHCCH), 6.92 (t, 7.8 Hz, H,
4
=
4
J
=
2
H, PCCHCH), 7.53 (t, JH,H = 7.4 Hz, 4 H, PCCHCHCH), 7.59 CONHCCHCHCH), 7.04 (s, 2 H, NH), 7.13 (t, J = 7.8 Hz, 4 H,
3
(dd, JH,H = 7.4, JH,P = 12.1 Hz, 8 H, PCCH) ppm. 13C NMR CONHCCHCH), 7.45 (dt, J = 7.5, J = 2.5 Hz, 8 H, Harom), 7.56
3
1
2
(100 MHz, CDCl3, 25 °C): δ = 14.6 (s, OCH2CH3), 17.7 (d, JC,P (t, J = 7.5 Hz, 4 H, PCCHCHCH), 7.59 (dd, JH,H = 7.5, JP,H
=
= 6.5 Hz, CH3CN), 23.7 (d, 2JC,P = 14.7 Hz, PCH2CH2CH2CH2P), 12.0 Hz, 8 H, Harom) ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ
27.1 (d, JC,P = 62.6 Hz, PCH2CH2CH2CH2P), 50.8 (d, JC,P
1
1
2
=
= 14.6 (s, OCH2CH3), 16.5 (d, JC,P = 1.7 Hz, PCH2CH2CH2P),
18.0 (d, JC,P = 6.3 Hz, CH3CN), 28.8 (dd, JC,P = 77.5, JC,P =
1
3
1
3
118.2 Hz, C=P), 58.1 (s, OCH2CH3), 128.0 (d, JC,P = 87.9 Hz,
PC), 129.0 (d, JC,P = 12.1 Hz, PCCH), 131.9 (d, JC,P = 9.5 Hz, 16.4 Hz, PCH2CH2 CH2P), 50.9 (d, 1JC,P = 118.6 Hz, C=P), 58.3 (s,
2
3
4
PCCHCH), 132.0 (d, JC,P = 2.7 Hz, PCCHCHCH), 151.9 (s, OCH2CH3), 118.3 (s, CONHCCH), 122.4 (s, CONHCCHCHCH),
2
1
C=N), 157.9 (s, CONH2), 169.6 (d, JC,P = 16.2 Hz, COOEt) ppm. 127.3 (d, JC,P = 88.6 Hz, P–C), 128.7 (s, CONHCCHCH), 129.2
31P NMR (162 MHz, CDCl3, 25 °C): δ = 20.81 ppm. MS (ES+):
(d, JC,P = 11.6 Hz, PCCHCH), 132.0 (d, JC,P = 9.5 Hz, PCCH),
3
2
m/z = 797 [M + H]+, 819 [M + Na]+. C42H50N6O6P2 (796.83): 132.3 (d, JC,P = 2.2 Hz, PCCHCHCH), 138.4 (s, CONHC), 151.9
4
2
calcd. C 63.31, H 6.32, N 10.55; found C 63.28, H 6.31, N 10.56.
(br. s, C=N), 153.4 (s, CONH), 169.6 (d, JC,P = 17.9 Hz, CO-
OEt) ppm. 31P NMR: (162 MHz, CDCl3, 25 °C): δ = 20.1 ppm.
MS (ES+): m/z = 935 [M + H]+, 957 [M + Na]+. C53H56N6O6P2
(934.99): calcd. C 68.08, H 6.04, N 8.99; found C 68.24, H 6.06, N
8.96.
Diethyl 1,13-Dianilino-4,10-dimethyl-1,13-dioxo-6,6,8,8-tetraphenyl-
2,3,11,12-tetraaza-6λ5,8λ5-diphosphatrideca-3,5,8,10-tetraene-5,9-di-
carboxylate (4e): White solid, m.p. 168 °C (dec.), quantitative yield
1
(0.086 g, 19% by filtration). H NMR (600 MHz, CDCl3, 25 °C):
δ = 1.02 (t, J = 7.0 Hz, 6 H, OCH2CH3), 1.88 (s, 6 H, CH3CN),
3.65 (q, J = 7.0 Hz, 4 H, OCH2CH3), 5.16 (t, JH,P = 15.9 Hz, 2
Diethyl
1,16-Dianilino-4,13-dimethyl-1,16-dioxo-6,6,11,11-tetra-
2
phenyl-2,3,14,15-tetraaza-6λ5,11λ5-diphosphahexadeca-3,5,11,13-
H, PCH2P), 6.69 (d, J = 7.8 Hz, 4 H, CONHCCH), 6.84 (br. s, 2 tetraene-5,12-dicarboxylate (4h): White solid, m.p. 184 °C (dec.),
1
H, NH), 6.89 (t, J = 7.8 Hz, 2 H, Harom), 7.09 (t, J = 7.8 Hz, 4 H, quantitative yield (0.26 g, 54% by filtration). H NMR (600 MHz,
H
arom), 7.43 (t, J = 7.7 Hz, 8 H, Harom), 7.53 (t, J = 7.7 Hz, 4 H, CDCl3, 25 °C): δ = 0.91 (t, J = 7.0 Hz, 6 H, OCH2CH3), 1.57 (m,
Harom), 7.80 (dd, J = 12.4, J = 7.7 Hz, 8 H, PCCH) ppm. 13C NMR 4 H, PCH2CH2 CH2CH2P), 2.20 (s, 6 H, CH3CN), 2.58 (m, 4 H,
3
(150 MHz, CDCl3, 25 °C): δ = 14.5 (s, OCH2CH3), 18.4 (t, JC,P
=
PCH2CH2 CH2CH2P), 3.92 (q, J = 7.0 Hz, 4 H, OCH2CH3), 6.84
(d, J = 7.8 Hz, 4 H, CONHCCH), 6.93 (t, J = 7.8 Hz, 2 H,
3.5 Hz, CH3CN), 22.6 (d, JC,P = 53.9 Hz, PCH2P), 51.0 (dd, 1JC,P
1
3
= 122.5, JC,P = 2.3 Hz, C=P), 58.4 (s, OCH2CH3), 118.2 (s,
CONHCCCCH), 7.14 (t, J = 7.8 Hz, 4 H, CONHCCCH), 7.17 (s,
CONHCCH), 122.4 (s, CONHCCHCH), 126.3 (d, 1JC,P = 94.8 Hz, 2 H, NNH), 7.45 (dt, JH,P = 2.7, JH,H = 7.3 Hz, 8 H, PCCCH),
4
3
5
P=C), 128.7 (s, CONHCCHCH), 128.8 (t, JC,P
= 5.4 Hz, 7.55 (dt, JH,P = 1.6, JH,H = 7.3 Hz, 4 H, PCCCCH), 7.63 (dd,
PCCHCH), 132.4 (s, PCCHCHCH), 133.2 (t, JC,P = 5.4 Hz, 3JH,P = 2.0, JH,H = 7.3 Hz, 8 H, PCCH) ppm. 13C NMR (151 MHz,
2
2
3
PCCH), 138.3 (s, CONHC), 149.9 (t, JC,P = 2.3 Hz, C=N), 153.1 CDCl3, 25 °C): δ = 14.6 (s, OCH2CH3), 17.9 (t, JC,P = 5.9 Hz,
(s, CONH), 169.7 (d, JC,P = 19.5 Hz COOEt) ppm. 31P NMR CH3CN), 23.7 (d, JC,P = 5.0 Hz, PCH2CH2 CH2CH2P), 27.7 (d,
2
2
(162 MHz, CDCl3, 25 °C): δ = 18.2 Hz ppm. MS (ES+): m/z = 907 1JC,P = 63.7 Hz, PCH2CH2 CH2CH2P), 50.9 (d, JC,P = 119.8 Hz,
1
[M + H]+, 929 [M + Na]+. C51H52N6O6P2 (906.94): calcd. C 67.54, C=P), 58.2 (s, OCH2CH3), 118.3 (s, CONHCCH), 122.5 (s,
1
H 5.78, N 9.27; found C 67.59, H 5.79, N 9.24.
CONHCCHCHCH), 127.7 (d, JC,P = 87.7 Hz, P–C), 128.8 (s,
3
CONHCCHCH), 129.2 (d, JC,P = 12.0 Hz, PCCHCH), 132.0 (d,
Diethyl 1,14-Dianilino-4,11-dimethyl-1,14-dioxo-6,6,9,9-tetraphenyl-
2,3,12,13-tetraaza-6λ5,9λ5-diphosphatetradeca-3,5,9,11-tetraene-
5,10-dicarboxylate (4f): White solid, m.p. 172 °C (dec.), quantitative
yield (0.25 g, 54% by filtration). 1H NMR (600 MHz, CDCl3,
25 °C): δ = 0.92 (t, J = 7.1 Hz, 6 H, OCH2CH3), 2.14 (s, 6 H,
4
2JC,P = 9.8 Hz, PCC), 132.2 (d, JC,P = 2.5 Hz, PCCHCHCH),
138.5 (s, CONHC), 151.7 (s, C=N), 153.6 (s, CONHPh), 169.6 (d,
2JC,P = 17.1 Hz, COOEt) ppm. 31P NMR (162 MHz, CDCl3,
25 °C): δ = 20.8 ppm. MS (ES+): m/z = 972 [M + Na]+.
C54H58N6O6P2 (949.02): calcd. C 68.34, H 6.16, N 8.86; found C
68.37, H 6.15, N 8.83.
2
CH3CN), 2.99 (d, JH,P = 4.7 Hz, 4 H, P CH2CH2P), 3.85 (q, J =
7.1 Hz, 4 H, OCH2CH3), 6.81 (d, J = 7.5 Hz, 4 H, CONHCCH),
6.82 (br. s, 2 H, NH), 6.93 (t, J = 7.5 Hz, 2 H, Harom), 7.12 (t, J = Reactions Between the DD 1a and Compounds 5a or 5b: A solution
7.5 Hz, 4 H, Harom), 7.40 (t, J = 7.6 Hz, 8 H, PCCHCH), 7.49 (t, of 1a (0.092 g, 0.5 mmol) in ethyl acetate (5 mL) was added to a
1
2
J = 7.6 Hz, 4 H, PCCHCHCH), 7.60 (dd, J = J = 7.6 Hz, 8 H,
solution of a phosphaneamine 5 (0.5 mmol) dissolved in ethyl acet-
1332
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Phospha-Michael-Type Reactions
ate (5 mL). The solution was magnetically stirred at room tempera-
ture. After a few minutes, disappearance of the red colour of the
DD and precipitation of a pale yellow solid from the solution was
observed. All attempts to isolate this solid by filtration failed be-
cause, immediately after the filtration, an oil was recovered. This
might be due to high hygroscopicity of the product, but an oil with
spectroscopic data that agreed with those of 6a was obtained even
if the reaction was repeated under inert atmosphere and the
workup was carried out under anhydrous inert conditions. The re-
action was also carried out in the NMR tube [the two reagents
(0.2 mmol) dissolved in CDCl3 (1.0 mL)] and the only signals pres-
ent in the spectra agreed with those of the ylide adduct 6. In the
case of compound 6a the CDCl3 solution was monitored and after
1 d the 1H NMR spectrum revealed that compound 6a had been
quantitatively transformed into a new compound. The solvent was
removed and the residue was purified by flash chromatography on
silica gel (eluent: chloroform/methanol 9:1 to 1:1), giving com-
pound 7a in nearly quantitative yield. In the case of compound 6b,
monitored in CDCl3 solution through 1H NMR spectroscopy, slow
conversion into a mixture of products was detected. After removal
of the solvent, the residue was chromatographed on alumina (elu-
ent: CH3OH/AcOEt 1:9 to 10:0). The spectroscopic data for the
compounds separated in this manner agreed with those for com-
pound 7b and of the pyrazole derivative 8, calculated (1H NMR)
to be present in the crude reaction mixture in a 20:80 relative molar
ratio.
Na]+. C22H29N4O3P (428.46): calcd. C 61.67, H 6.82, N 13.08;
found C 61.75, H 6.83, N 13.10.
Ethyl
2-Methyl-4,4-diphenyl-5,6-dihydro-1,4λ5-azaphosphinine-3-
1
carboxylate (7a): H NMR (600 MHz, CDCl3, 25 °C): δ = 0.82 (t,
J = 7.0 Hz, 3 H, OCH2CH3), 2.56–2.61 (m, 2 H, PCH2), 2.71 (s, 3
H, CH3C), 3.58 (dm, JH,P = 22.9 Hz, 2 H, PCH2), 3.87 (q, J =
2
7.0 Hz, 2 H, OCH2CH3), 7.57–7.61 (m, 4 H, Harom), 7.67–7.72 (m,
4 H, Harom), 7.72–7.77 (m, 2 H, Harom) ppm. 13C NMR (151 MHz,
1
CDCl3, 25 °C): δ = 14.1 (s, OCH2CH3), 21.9 (d, JC,P = 55.6 Hz,
2
PCH2), 23.9 (3JC,P = 7.5 Hz, CH3C), 36.0 (d, JC,P = 7.2 Hz
NCH2), 60.2 (s, OCH2CH3), 66.0 (d, 1JC,P = 103.5 Hz, P=C), 123.8
1
3
(d, JC,P = 92.7 Hz, PC), 129.3 (d, JC,P = 12.8 Hz, PCHCHCH),
2
4
132.7 (d, JC,P = 10.4 Hz, PCCH), 133.2 (d, JC,P = 2.4 Hz,
PCCHCHCH), 165.8 (d, JC,P = 8.2 Hz, C=N), 171.6 (d, JC,P
2
2
=
4.7 Hz, COOEt) ppm. 31P NMR (162 MHz, CDCl3, 25 °C): δ =
7.0 ppm. MS (ES+): m/z = 340 [M + H]+, 362 [M + Na]+.
C20H22NO2P (339.38): calcd. C 70.78, H 6.53, N 4.13; found C
70.70, H 6.54, N 4.12.
Ethyl 2-Methyl-4,4-diphenyl-6,7-dihydro-5H-1,4λ5-azaphosphepine-
1
3-carboxylate (7b): H NMR (600 MHz, CDCl3, 25 °C): δ = 0.83
3
(t, J = 7.2 Hz, 3 H, OCH2CH3), 2.09 (dquint, JH,H = 6.8, JH,P
=
=
2
16.2 Hz, 2 H, PCH2CH2CH2N), 2.76 (dt, JH,H = 6.8, JH,P
12.0 Hz, 2 H, PCH2), 2.89 (s, 3 H, CH3C), 3.45 (t, JH,H = 6.8 Hz,
2 H, PCH2CH2CH2N), 3.82 (q, J = 7.2 Hz, 2 H, OCH2CH3), 7.60–
7.67 (m, 8 H, Harom), 7.69–7.73 (m, 2 H, Harom) ppm. 13C NMR
2
(151 MHz, CDCl3, 25 °C): δ = 14.0 (s, OCH2CH3), 23.3 (d, JC,P
1
= 5.2 Hz, PCH2CH2CH2N), 24.3 (d, JC,P = 55.3 Hz, PCH2), 25.6
Ethyl
3-[(Aminocarbonyl)hydrazono]-2-[(2-aminoethyl)(diphenyl)-
(d, 3JC,P = 8.0 Hz, CH3C), 45.7 (d, 3JC,P = 7.9 Hz, PCH2CH2CH2),
phosphoranylidene]butanoate (6a): 1H NMR (600 MHz, CDCl3,
25 °C): δ = 1.03 (t, J = 7.0 Hz, 3 H, OCH2CH3), 1.23 (br. s, 2 H,
PCH2CH2NH2), 2.13 (s, 3 H, CH3C), 2.78–2.84 (m, 2 H, PCH2),
2.93–2.98 (m, 2 H, NH2CH2), 3.96 (q, J = 7.0 Hz, 2 H, OCH2CH3),
60.2 (s, OCH2CH3), 64.5 (d, 1JC,P = 105.0 Hz, P=C), 124.5 (d, 1JC,P
3
= 90.3 Hz, PC), 129.9 (d, JC,P = 12.7 Hz, PCCHCH), 132.1 (d,
4
2JC,P = 10.4 Hz, PCCH), 133.7 (d, JC,P = 3.0 Hz, PCCHCHCH),
2
2
166.2 (d, JC,P = 8.9 Hz, C=N), 179.7 (d, JC,P = 6.4 Hz, CO-
OEt) ppm. 31P NMR (121 MHz, CDCl3, 25 °C): δ = 16.4 (s) ppm.
MS (ES+): m/z = 354 [M + H]+. C21H24NO2P (353.39): calcd. C
71.37, H 6.85, N 3.96; found C 71.43, H 6.87, N 3.95.
4.67 (br. s, 2 H, CONH2), 7.33 (br. s, 1 H, NH), 7.42 (dt, JH,H
=
=
4
5
7.7, JH,P = 3.0 Hz, 4 H, PCCCH), 7.49 (dt, JH,H = 7.7, JH,P
3
2.0 Hz, 2 H, PCCCCH), 7.59 (dd, JH,H = 7.7, JH,P = 12.2 Hz, 4
H, PCCH) ppm. 13C NMR (151 MHz, CDCl3, 25 °C): δ = 14.6 (s,
3
1
OCH2CH3), 18.0 (d, JC,P = 6.6 Hz, CH3C), 31.5 (d, JC,P
=
57.9 Hz, PCH2), 36.5 (s, PCH2CH2NH2), 51.0 (d, 1JC,P = 118.0 Hz,
Acknowledgments
1
P=C), 58.2 (s, OCH2CH3), 127.8 (d, JC,P = 88.6 Hz, PC), 129.0
(d, 3JC,P = 11.9 Hz, PCHCHCH), 131.9 (d, 2JC,P = 9.8 Hz, PCCH),
This work was supported by Università di Bologna [Fundamental
Oriented Research (RFO) funds] and the Italian Ministero
4
2
132.0 (d, JC,P = 2.9 Hz, PCCHCHCH), 151.6 (d, JC,P = 5.3 Hz,
2
C=N), 157.7 (s, CONH2), 169.7 (d, JC,P = 16.7 Hz, COOEt) ppm.
dell’Università
e
della Ricerca (MIUR) (Project PRIN
31P NMR (162 MHz, CDCl3, 25 °C): δ = 19.1 ppm. MS (ES+): m/z
= 415 [M + H]+, 437 [M + Na]+. C21H27N4O3P (414.44): calcd. C
60.86, H 6.57, N 13.52; found C 60.78, H 6.59, N 13.49.
20078J9L2A_005: New frontiers in the synthesis, reactions and appli-
cations of compounds containing heteroatoms).
[1] a) M. B. Smith, J. March, March’s Advanced Organic Chemis-
try, 6th ed., John Wiley & Sons, Hoboken, N.J., 2007, p. 1105,
and references cited therein; b) P. Perlmutter, in: Conjugate Ad-
dition Reactions in Organic Synthesis Pergamon Press, Oxford,
UK, 1992; c) C. Botteghi, S. Paganelli, A. Schionato, C. Boga,
A. Fava, J. Mol. Catal. 1991, 66, 7–21, and references cited
therein.
Ethyl 3-[(Aminocarbonyl)hydrazono]-2-[(3-aminopropyl)(diphenyl)-
phosphoranylidene]butanoate (6b): 1H NMR (600 MHz, CDCl3,
25 °C): δ = 1.00 (t, J = 7.0 Hz, 3 H, OCH2CH3), 1.40 (br. s, 2 H,
CH2NH2), 1.61–1.69 (m, 2 H, PCH2CH2CH2NH2), 2.15 (s, 3 H,
CH3C), 2.62–2.69 (m, 2 H, PCH2), 2.70 (t, J = 6.8 Hz, 2 H,
CH2NH2), 3.94 (q, J = 7.0 Hz, 2 H, OCH2CH3), 4.70 (br. s, 2 H,
CONH2), 7.33 (br. s, 1 H, NH), 7.42 (dt, 4JH,P = 3.0, JH,H = 7.6 Hz,
[2] D. Enders, K. Lüttgen, A. A. Narine, Synthesis 2007, 959–980
5
4 H, PCCHCH), 7.49 (dt, JH,P = 1.8, JH,H = 7.7 Hz, 2 H,
and refs. cit. therein.
PCCHCHCH), 7.60 (dd, J = 12.1; J = 7.7 Hz, 4 H, PCCH) ppm.
[3] For a recent review on aza-Michael reaction, see: D. Enders,
C. Wang, J. X. Liebich, Chem. Eur. J. 2009, 15, 11058–11076.
[4] C. F. Nising, S. Bräse, Chem. Soc. Rev. 2008, 37, 1218–1228.
[5] a) D. Enders, A. Saint-Dizier, M.-I. Lannou, A. Lenzen, Eur. J.
Org. Chem. 2006, 29–49; b) R. Engel, in: Synthesis of Carbon–
Phosphorus Bonds, CRC Press, Boca Raton, FL, 1988.
[6] For recent reviews, see: a) O. A. Attanasi, L. De Crescentini, P.
Filippone, F. Mantellini, S. Santeusanio, ARKIVOC 2002, 11,
274–292; b) O. A. Attanasi, L. De Crescentini, G. Favi, P. Filip-
pone, F. Mantellini, F. R. Perrulli, S. Santeusanio, Eur. J. Org.
Chem. 2009, 3109–3127.
13C NMR (151 MHz, CDCl3, 25 °C): δ = 14.6 (s, OCH2CH3), 18.0
3
1
(d, JC,P = 6.2 Hz, CH3C), 25.1 (d, JC,P = 62.0 Hz, PCH2), 26.3
2
3
(d, JC,P = 3.5 Hz, PCH2CH2CH2NH2), 43.0 (d, JC,P = 18.0 Hz,
1
CH2NH2), 51.0 (d, JC,P = 118.9 Hz, P=C), 58.0 (s, OCH2CH3),
127.9 (d, JC,P = 88.6 Hz, PC), 128.9 (d, JC,P = 12.1 Hz,
PCHCHCH), 131.9 (d, JC,P = 9.6 Hz, PCCH), 132.0 (d, JC,P
1
3
2
4
=
2.9 Hz, PCCHCHCH), 151.9 (s, C=N), 157.8 (s, CONH2), 169.6
2
(d, JC,P = 16.4 Hz, COOEt) ppm. 31P NMR (162 MHz, CDCl3,
25 °C): δ = 21.3 ppm. MS (ES+): m/z = 429 [M + H]+, 451 [M +
Eur. J. Org. Chem. 2011, 1326–1334
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1333

C. Boga et al.
FULL PAPER
[7] T. Kanzian, S. Nicolini, L. De Crescentini, O. A. Attanasi, A.
Ofial, H. Mayr, Chem. Eur. J. 2010, 16, 12008–12016.
[8] O. A. Attanasi, P. Filippone, A. Mei, Tetrahedron 1992, 48,
1707–1714.
[9] O. A. Attanasi, P. Filippone, S. Giovagnoli, Org. Prep. Proced.
Int. 1994, 26, 321–326.
[10] O. A. Attanasi, G. Baccolini, C. Boga, L. De Crescentini, P.
Filippone, F. Mantellini, J. Org. Chem. 2005, 70, 4033–4037.
[11] O. A. Attanasi, G. Baccolini, C. Boga, L. De Crescentini, P.
Filippone, F. Mantellini, Tetrahedron 2008, 64, 6724–6732.
[12] O. A. Attanasi, G. Baccolini, C. Boga, L. De Crescentini, G.
Giorgi, F. Mantellini, S. Nicolini, Eur. J. Org. Chem. 2008,
5965–5979.
ety, Washington, DC, 1980, vol. I and II; b) L. D. Quin, A. J.
Williams, Practical Interpretation of 31P NMR Spectra and
Computer-Assisted Structure Verification. Advanced Chemistry
Development, Inc., Toronto, 2004, chapter 12, pp. 83–85; c) E.
Fluck, G. Heckmann, Empirical Methods for Interpreting
Chemical Shifts of Phosphorus Compounds, in: Phosphorus-31
NMR Spectroscopy in Stereochemical Analysis, Organic Com-
pounds and Metal Complexes (Eds.: J. G. Verkade, L. D. Quin),
VCH Publishers, Deerfield Beach, FL, 1987, chapter 2; d) G.
Baccolini, C. Boga, R. A. Buscaroli, Eur. J. Org. Chem. 2001,
3421–3424; e) G. Baccolini, C. Boga, M. Mazzacurati, F. Sangi-
rardi, Org. Lett. 2006, 8, 1677–1680; f) G. Baccolini, C. Boga,
M. Mazzacurati, Eur. J. Org. Chem. 2007, 4529–4534.
[13] a) O. I. Kolodiazhnyi, in: Phosphorus Ylides, Chemistry and Ap-
plication in Organic Synthesis, Wiley-VCH, Weinheim, Ger-
many, 1999; b) G. Pohnert, W. Boland, Eur. J. Org. Chem. 2000,
1821–1826.
[14] a) D. E. Berry, J. Browning, K. R. Dixon, R. W. Hilts, Can. J.
Chem. 1988, 66, 1272–1282; b) A. Spannenberg, W. Baumann,
U. Rosenthal, Organometallics 2000, 19, 3991–3993; c) L. R.
Falvello, M. E. Margalejo, R. Navarro, E. P. Urriolabeitia, In-
org. Chim. Acta 2003, 347, 75–85; d) Y. Canac, C. Lepetit, M.
Abdalilah, C. Duhayon, R. Chauvin, J. Am. Chem. Soc. 2008,
130, 8406–8413.
[15] a) R. Appel, G. Haubrich, Angew. Chem. 1980, 92, 206–207;
Angew. Chem. Int. Ed. Engl. 1980, 19, 213–214; b) E. Vedejs,
J. P. Bershas, J. Org. Chem. 1972, 37, 2639–2640; c) H. Schmid-
bauer, A. W. Wohlleben-Hammer, Chem. Ber. 1979, 11, 510–
516; d) N. Holy, U. Deshler, H. Schmidbaur, Chem. Ber. 1982,
115, 1379–1388.
[16] a) R. Appel, G. Haubrich, F. Knoch, Chem. Ber. 1984, 117,
2063–2075; b) A. N. Hughes, S. W. S. Jafry, J. Heterocycl.
Chem. 1969, 6, 991–992; c) I. Shevchenko, V. Andrushko, E.
Lork, G.-V. Röschenthaler, Eur. J. Inorg. Chem. 2002, 2985–
2990.
[20]
L. Forlani, O. A. Attanasi, C. Boga, L. De Crescentini, E.
Del Vecchio, G. Favi, F. Mantellini, S. Tozzi, N. Zanna, Eur. J.
Org. Chem. 2008, 4357–4366.
a) H. S. Gutowsky, C. H. Holm, J. Chem. Phys. 1956, 25, 1228–
1234; b) H. Eyring, Chem. Rev. 1935, 17, 65–77.
L. Lunazzi, A. Mazzanti, A. Muñoz Álvarez, J. Org. Chem.
2000, 65, 3200–3206.
a) D. Aparicio, O. A. Attanasi, P. Filippone, R. Ignacio, S. Lil-
lini, F. Mantellini, F. Palacios, J. M. de los Santos, J. Org.
Chem. 2006, 71, 5897–5905; b) O. A. Attanasi, S. Berretta, L.
De Crescentini, G. Favi, G. Giorgi, F. Mantellini, Adv. Synth.
Catal. 2009, 351, 715–719.
[21]
[22]
[23]
[24]
P. Vicini, M. Incerti, R. Ferretti, F. Zanardi, Mol. Diversity
2006, 10, 251–253.
[25] a) G. Keglevich, Top. Heterocycl. Chem. 2009, 20, 65–98; b)
P. Le Floch, Top. Heterocycl. Chem. 2009, 20147–20184; c) L.
Kollar, G. Keglevich, Chem. Rev. 2010, 110, 4257–4302; d) J.
Barluenga, M. Tomfis, K. Bieger, S. G. Granda, R. S. Garcia,
J. Organomet. Chem. 1997, 529, 233–241.
[26] J. Vicario, D. Aparicio, F. Palacios, J. Org. Chem. 2009, 74,
452–455.
[17] a) Y. G. Gololobov, V. A. Pinchuk, H. Thönnessen, P. G. Jones,
R. Schmutzler, Phosphorus Sulfur Silicon Relat. Elem. 1996,
115, 19–37; b) I. Yavari, N. N. Arasi, H. R. Bijanzadeh, J. Flu-
orine Chem. 2000, 103, 155–157, and references cited therein.
[18] F. H. Westheimer, Acc. Chem. Res. 1968, 1, 70–78.
[19] a) R. R. Holmes, in Pentacoordinated Phosphorus Structure and
Spectroscopy, ACS Monograph 175, American Chemical Soci-
[27] O. A. Attanasi, S. Bartoccini, G. Giorgi, F. Mantellini, F. R.
Perrulli, S. Santeusanio, Tetrahedron 2010, 66, 5121–5129.
[28] O. A. Attanasi, P. Filippone, A. Mei, S. Santeusanio, Synthesis
1984, 671–672.
Received: October 26, 2010
Published Online: January 12, 2011
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Eur. J. Org. Chem. 2011, 1326–1334