A simple route to kinetically unstabilized phosphaalkynes

Full text of DOI:10.1021/jo010612h

7864
J . Org. Chem. 2001, 66, 7864-7868
Notes
example, a solution of Et-CtP can be kept several days
at room temperature without appreciable alteration.5 We
have shown several years ago that simple phosphaalkynes
can be synthesized in liquid phase by rearrangement at
low temperature of the corresponding 1-alkynylphos-
phines in the presence of catalytic amounts of Lewis
base.7 This efficient approach was however limited by the
small number of easily available primary 1-alkynylphos-
phines. Herein we report that phosphaalkynes, substi-
tuted as well by primary or secondary alkyl groups, can
be synthesized under classical conditions in a sequence
involving the chemoselective reduction of an ethereal
solution of R-dichlorophosphonates with AlHCl2 followed
by the bis-dehydrohalogenation of the resulting R-di-
chlorophosphines by a strong Lewis base. Scalability of
the process is demonstrated by the preparation of 0.4 mol
of CH3CtP.
A Sim p le Rou te to Kin etica lly Un sta bilized
P h osp h a a lk yn es
J ean-Claude Guillemin,*,† Tajdine J anati,‡ and
J ean-Marc Denis*,‡
Synthe`se et Electrosynthe`se Organiques, UMR CNRS 6510,
Universite´ de Rennes 1, 35042 Rennes, France, and
Synthe`se et Activation de Biomole´cules, UMR CNRS 6052,
ENSCR, 35700 Rennes, France.
jean-marc.denis@univ-rennes1.fr
Received J une 15, 2001
In tr od u ction
Kinetically stabilized phosphaalkynes R-CtP are
readily available by base-induced elimination of hexa-
methyldisiloxane from Me3SiO(R)CdPSiMe31 As a result
of the presence of both the triple bond and the phos-
phorus lone pair electrons, such compounds were inten-
sively used as partners and ligands for a variety of
transition metals and for the synthesis of numerous
oligomers of controlled structure.2,3 In organic chemistry,
they are interesting starting materials for addition and
cycloaddition reactions.3 By contrast, the development of
the chemistry of kinetically nonstabilized phosphaalkynes
remains dramatically poor. That is mainly due to their
relative instability and to the lack of simple and efficient
synthetic approaches.4 In 1991, we described the prepa-
ration of various phosphaalkynes by bis-dehydrohaloge-
nation of volatile R-dichlorophosphines under vacuum
gas-solid reactions conditions (VGSR technique).5,6 Thus,
simple derivatives such as HCtP, CH3-CtP, or TMS-
CtP and new compounds such as Cl-CtP have been
prepared. Nevertheless, this approach needs special
equipment and furthermore is rather restrictive, espe-
cially with regard to its analytical relevance. To consider
such phosphaalkynes as potentially useful synthons in
organophosphorus chemistry, more conventional ap-
proaches are required. The feasibility of a preparation
in solution under standard conditions was reinforced by
the unexpected stability of these compounds. As an
Resu lts a n d Discu ssion
r-Dich lor oph osph on ates. R-Dichlorophosphonic acid,
dialkyl esters 1b-f,h were prepared starting from the
easily available trichloromethylphosphonate 1a 8 by halo-
gen/metal exchange followed by reaction of the resulting
anion with the corresponding alkyl halide.9-11 Com-
pounds 1g,i were synthesized by a similar approach
starting from (2-bromoethyl)benzene and 4-bromobutene
respectively (eq 1).
The phenyl- and cyclohexyl derivatives 1j,k were
synthesized in a three-step sequence involving the con-
densation on alumina of the corresponding aldehyde with
diethyl phosphite,12 chlorination of the resulting hy-
droxydiethyl ester by thionyl chloride, and reaction of the
formed product with BuLi and then CCl4 (Scheme 1).10,13
Reduction of phosphonates 3 to phosphines 4 and
dehydrochlorination of the resulting R-chlorophosphines
4 to phosphalkynes 5 are presented in the following text.
For both steps, the choice of the solvent is critical and
† ENSCR.
‡ Universite´ de Rennes 1.
(1) (a) Becker, G.; Gresser, G.; Uhl, W. Z. Naturforsch. 1981, 36B,
16. (b) Regitz, M. Nachr. Chem. Technol. Lab. 1989, 37, 896 and
references therein. (c) Regitz, M.; Binger, P. Angew. Chem., Int. Ed.
Engl. 1988, 27, 1484 and reference therein.
(2) (a) Regitz, M. Chem. Rev. 1990, 90, 191. (b) Regitz, M. J .
Heterocycl. Chem. 1994, 31, 663.
(7) Guillemin, J .-C.; J anati, T.; Denis, J .-M. J . Chem. Soc., Chem.
Commun. 1992, 415.
(8) Arbusov, A. E. J . Russ. Phys. Chem. Soc. 1906, 38, 687.
(9) Marmor, R. S.; Seyferth, D. J . Organomet. Chem. 1973, 59, 237.
(10) Savignac, P.; Dreux, M.; Coutrot, P. Tetrahedron Lett. 1975, 9,
609. Coutrot, P.; Laurenc¸o, C.; Normant, J . F.; Perriot, P.; Savignac,
P.; Villieras, J . Synthesis 1977, 615.
(3) (a) Regitz, M.; Scherer, O. J . Multiple Bonds and Low Coordina-
tion in Phosphorus Chemistry; Georg Thieme Verlag: Stuttgart, 1990;
pp 59-111. (b) Nixon J . F.; Coord. Chem. Rev. 1995, 145, 201-258.
(c) Dillon, K. B.; Mathey, F.; Nixon, J . F. Phosphorus: The Carbon
Copy; J ohn Wiley & Sons: New York, 1998; pp 40-87.
(4) Gaumont, A.-C.; Denis, J .-M. Chem. Rev. 1994, 94, 1413.
(5) Guillemin, J .-C.; J anati, T.; Guenot, P.; Savignac, P.; Denis, J .-
M. Angew. Chem., Int. Ed. Engl. 1991, 30, 196.
(11) J ubault, P.; Feasson, C.; Collignon, N. Tetrahedron Lett. 1995,
36, 7073.
(6) For
a
review on the VGSR technique, see: Denis, J . M.;
(12) Texier-Boullet, F.; Foucaud, A. Synthesis 1982, 165.
(13) Benezra, C.; Nseic, S.; Ourisson, G. Bull. Soc. Chim. Fr. 1967,
1140.
Gaumont, A.-C. Gas-Phase Reactions in Organic Synthesis; Gordon &
Breach Science Publishers: U.K., 1997; pp 195-235.
10.1021/jo010612h CCC: $20.00 © 2001 American Chemical Society
Published on Web 10/20/2001

Notes
J . Org. Chem., Vol. 66, No. 23, 2001 7865
Ta ble 1. Yield s a n d 31P NMR Da ta of Dich lor op h osp h in es 4a -k a n d P h osp h a a lk yn es 5a -k
yield
[%]a
yield
[%]a
phosphonate
dichlorophosphine
Cl3CPH2, 4a
HCCl2PH2, 4b
MeCCl2PH2, 4c
EtCCl2PH2, 4d
n-BuCCl2PH2, 4e
TMSCCl2PH2, 4f
PhCH2CH2CCl2PH2, 4g
H2CdCHCH2CCl2PH2, 4h
H2CdCH(CH2)2CCl2PH2, 4i
PhCCl2PH2, 4j
δP [ppm] (1J PH) [Hz]
phosphaalkyne
ClCtP, 5a
HCtP, 5b
CH3CtP, 5c
EtCtP, 5d
n-BuCtP, 5e
TMSCtP, 5f
PhCH2CH2CtP, 5g
H2CdCHCH2CtP, 5h
H2CdCH(CH2)2CtP, 5i
PhCtP, 5j
δP [ppm] (3J PH) [Hz]
1a
1b
1c
1d
1e
1f
1g
1h
1i
-12 (200)
-78 (199)
-46 (196)
-56 (197)
-53 (198)
-79 (196)
-55 (197)
-57 (198)
-53 (198)
-30 (198)
-55 (201)
71
86
91
91
b
b
20
75
77
81
b
-32, (44.0)c
-61, (15.0)
-62, (15.0)
-59, (14.7)
b
94
85
85d
85
-56.8, (14.9)
-52, (15.3)
-57, (15.2)
b
60d
75
72
b
85
1j
1k
55d
84d
C6H11CCl2PH2, 4k
C6H11CtP, 5k
-62 (14.9)
73d
Determined by 1H or/and 31P NMR spectroscopy with an internal reference. Decomposition in the elimination step.
J
.
Crude
a
b
c 2
d
PH
product.
Sch em e 1
The crude nonvolatile phosphines 4g,j,k were obtained
by removing in vacuo (10-1 mbar) the volatile solvent at
low temperature (-40 °C). In the absence of solvent, the
dichlorophosphines 4a -k are not stable at room tem-
perature and consequently have to be used as formed.
Structures of phosphines 4a -k were determined by 1H,
31P, and 13C NMR spectroscopy. The phosphorus chemical
shift range from δP -12 (4a ) to -79 ppm (4f). All the
1
coupling constants J PH observed by 1H and 31P NMR
spectroscopy are of 198 ( 3 Hz (Table 1). The high-
resolution mass spectra (HRMS) of phosphines 4a -i,k
were also recorded and are in very good agreement with
the assigned structures. Attempts to get the mass
spectrum of 4j were unsuccessful, the product being too
unstable in the experimental conditions. Yields deter-
mined by 1H or by 31P NMR spectroscopy with an internal
reference range between 55% and 94% (Table 1).
depends on how the products (neat or in solution) have
to be obtained.
P h osp h a a lk yn es. For the elimination step, ethereal
solutions of R-chlorophosphines 4a -k are commonly
used. When other solvents such as toluene are employed,
they should be added to the neat phosphines 4a -k after
the reduction step (vide supra). The choice of the base
was critical. The use of weak Lewis bases such as
pyridine or triethylamine gave a complex mixture of
products probably resulting from a partial HCl-elimina-
tion and in situ oligomerization of the corresponding
transient phosphaalkene intermediates. The best results
were obtained with a strong Lewis base. Thus, the
phosphaalkynes 5b-e,g-i,k are formed by low-temper-
ature elimination (-60 °C) of 4b-e,g-i,k with DBU (2.1
equiv) (eq 3). A clear solution was obtained after precipi-
r-Dich lor op h osp h in es. The chemoselective reduction
of phosphonates 1a -k to the corresponding phosphines
4a -k was performed in a cooled ethereal solution of
dichloroalane (AlHCl2) (eq 2).14 Volatile solvents such as
diethyl ether or THF and high boiling diglymes having
a melting point lower than -60 °C such as diethylene
glycol dibutyl ether can be commonly used. Excess of the
reducing agent was then hydrolyzed with degassed water,
and the resulting solution was filtered off on Celite under
a nitrogen pressure. Ethereal solutions of the low boiling
phosphines 4a -f,h ,i, completely free of alane residues,
can be obtained by trap-to-trap distillation of both volatile
solvents and products from the crude mixture. In these
conditions, the solutions can be kept several weeks in a
freezer (-20 °C) in the presence of duroquinone as radical
inhibitor. If needed, volatile phosphines can also be
obtained in pure form by selective trapping on a vacuum
line. The best conditions for purification of 1b-c were
obtained by trapping the solvent of reduction (diglyme
for this purpose) at low temperature (-40 °C) and then
the pure phosphines on a trap cooled at -80 °C. For
1a ,d -f,h ,i, diethyl ether should be used as solvent, the
dichlorophosphines being selectively trapped at -70 °C.
tation of the salts with pentane followed by filtration on
Celite under a nitrogen pressure. The low boiling phos-
phaalkynes 5b-e,h ,i, free of Lewis base, were obtained
in solution by trap-to-trap distillation in vacuo and
condensation on a cold trap of both volatile solvents and
phosphaalkynes. Under these conditions, these solutions
can be kept several days at room temperature or several
months in a freezer (-20 °C) in the presence of a radical
inhibitor (duroquinone). The yields determined by 31P
NMR spectroscopy with internal reference range from
60% to 81%. Even the very unstable parent compound
5b (HCtP) was prepared by this way but in a lower yield
(20%). The syntheses of 3-butenylphosphaalkyne 5i and
(14) Cabioch, J .-L.; Denis, J .-M. J . Organomet. Chem. 1989, 377,
227. Guillemin, J .-C.; Savignac, P.; Denis, J .-M. Inorg. Chem. 1991,
30, 2170.

7866 J . Org. Chem., Vol. 66, No. 23, 2001
Notes
Ma ter ia ls. LAH, aluminum chloride, DBU, and triisopropyl
phosphite were purchased from Acros and used as received.
Diethyl ether and diethylene glycol dibutyl ether (diglyme) were
dried by distillation on Na/benzophenone.
Gen er a l. 1H (300 MHz), 13C (100 MHz), and 31P (121 MHz)
NMR spectra were recorded on a Bruker AC-300P spectrometer,
and HRMS (high-resolution mass spectrometry) experiments
were performed on a Varian MAT 311 instrument. To record
the mass spectra, dichlorophosphines 4 and phosphaalkynes 5
were directly introduced from a cell into the ionization chamber
of the spectrometer. All dichlorophosphines and phosphaalkynes
were kept at low temperature under neutral gas in the presence
of small amounts of duroquinone.
P r ep a r a t ion of Dich lor op h osp h in es (4a -k ). Gen er a l
P r oced u r e. A suspension of LiAlH4 (0.53 g, 14 mmol) in the
desired freshly distilled solvent (diethyl ether or diglyme, 30 mL)
was cooled to -70 °C, and AlCl3 (5.60 g, 42 mmol) was quickly
added. After warming up this suspension to -10 °C and then
cooling it to -80 °C, the phosphonate 1a -k (10 mmol) in diethyl
ether or diglyme (10 mL) was added dropwise at a rate to
maintain the temperature under -60 °C. The solution was
allowed to warm to -30 °C, and degassed water (5 mL) was
slowly added. The mixture was then heated to 0 °C, transferred
in a flask containing about 20 g of MgSO4, filtered on Celite
under a nitrogen pressure, and kept at low temperature (<-30
°C).
P u r ifica t ion of t h e E t h er ea l Solu t ion of Low Boilin g
Dich lor op h osp h in es (4a -f,h ,i). When diethyl ether was used
as solvent, the residual high boiling impurities contained in the
crude solution of the phosphines 4a -f,h ,i, such as aluminum
derivatives, were removing by trap-to-trap distillation in vacuo
(10-1 mbar) of both the solvent and product. Thus, the flask was
fitted on a vacuum line, and all of the low boiling compounds
were evaporated and then condensed in a cold trap (77 K). Under
these conditions, the solutions of dichlorophosphines 4a -f,h ,i
can be kept for several weeks in a freezer under nitrogen.
P r ep a r a tion of P u r e Low Boilin g Dich lor op h osp h in es
(4b,c). To obtain pure samples of phosphines 4b,c, diglyme
should be used as solvent. The filtrated mixture, prepared as
reported above, was fitted on a vacuum line equipped with two
cold traps. The first trap was cooled at -40 °C, and the second
one, equipped with two stopcocks, was immersed in a bath cooled
at -80 °C. The mixture was degassed, and the low boiling
compounds were distilled in vacuo (10-1 mbar). The phosphines
4b,c were selectively condensed in the second trap. At the end
of the distillation, this trap was disconnected from the vacuum
line, and the pure phosphines 4b,c thus obtained were kept at
low temperature (-20 °C)
P r ep a r a tion of P u r e Low Boilin g Dich lor op h osp h in es
(4a ,d -f,h ,i). To obtain pure samples of phosphines 4a ,d -f,h ,i,
diethyl ether should be used as solvent. The flask containing
the crude or the distilled ethereal solution was fitted on a
vacuum line equipped with two traps. The low boiling com-
pounds were distilled, and the phosphines 4a ,d -f,h ,i were
selectively condensed on the first trap cooled at -70 °C. To get
a very pure compound, the procedure was repeated by cooling
the second trap at -70 °C and removing the cold bath from the
first one. Pure phosphines 4a ,d -f,h ,i should be kept at low
temperature (-20 °C).
phenylethylphosphaalkyne 5g are unprecedented. The
presented process was extended to the preparation of the
phosphaalkyne 5k substituted by a secondary carbon, a
compound usually considered as kinetically stabilized.15
However, we failed in the attempts to prepare the more
unstable derivatives ClCtP 5a , TMSCtP 5f or PhCtP
5j, which are accessible by bis-dehydrochlorination of the
corresponding R-dichlorophosphines in gas-phase under
VGSR conditions.5
Volatile phosphaalkynes 5b-e,h ,i were easily purified
on the vacuum line, diglyme being in this case chosen as
solvent both in the reduction and elimination steps. The
boiling points of the phosphaalkynes 5g,k are too high
to allow their purification by distillation in good condi-
tions. Consequently, crude samples of these products
were obtained by removing the solvent at low tempera-
ture (-40 °C) in vacuo (10-1 mbar). In the absence of
solvent, the phosphaalkynes 5b-e,g-i,k are unstable at
room temperature (eq 3).
Structures of the phosphaalkynes 5b-e,h were deter-
1
mined by H, 13C, and 31P NMR spectroscopy and com-
pared with the reported data.4,5,7 The IR and mass spectra
of compounds 5b-e were also recorded. The structures
of compounds 5g,i,k were attributed on the basis of their
NMR data. On the 31P NMR spectra, the signals of
phosphaakynes 5b-e,g-i,k were observed between -32
3
(5b) and -62 (5c) ppm. The chemical shift and J PH
coupling constants for 5c-e,g-i,k (15.0 ( 0.3 Hz) are
characteristic of these compounds. The signals of the 13C
NMR chemical shifts of the sp carbon atoms were
observed at 158.0 ppm (HCtP) and at 176 ( 4 ppm for
all the substituted derivatives (Table 1).
The scalability of the process was demonstrated by the
preparation of CH3CtP 5c on a 0.4 molar scale starting
from the corresponding dichlorophosphonate 1c. The
general protocol was used without any modification. The
overall yield (66%) was on the same order as that
obtained on the analytical scale. The distilled ethereal
solution (concentration ≈8%) was kept for few months
in the freezer (-20 °C). Samples of this solution were
drawn from time to time for various experiments. After
3 months, the decomposition was estimated to be lower
than 10% (13P NMR analysis).
Con clu sion
A two-step sequence allowing the preparation of ki-
netically unstabilized phosphaalkynes under standard
synthetic conditions has been presented. This process can
be extended to the preparation of kinetically stabilized
phosphaalkynes. The scalability is well demonstrated.
This approach should contribute to the use of unstabilized
phosphaalkynes in organic and organometallic chemistry.
As a result of the intrinsic reactivity of these compounds,
the reactions that can be performed at room temperature
or below and in diluted concentration have the best
opportunity to work.
P r ep a r a tion of Cr u d e Dich lor op h osp h in es (4g,j,k ) in
th e Absen ce of Solven t. Dichlorophosphines 4g,j,k decompose
on heating. Consequently, their boiling points are too high to
allow their purification by distillation in good conditions.
Ethereal solutions were concentrated by cooling the solution at
-40 °C and removing the solvent in vacuo. These resulting crude
products should be kept at low temperature (< -50 °C).
Tr ich lor om eth ylp h osp h in e (4a ). Yield: 71%. 31P NMR
(CDCl3) δ: -12 (1J PH ) 200 Hz). 1H NMR (CDCl3) δ: 5.06 (d,
1
2H, J PH ) 200 Hz). 13C NMR (CDCl3) δ: 89.8 (1J CP ) 42.0 Hz).
Exp er im en ta l Section
HRMS calcd for CH2Cl3P: 149.8960; found 149.895.
Dich lor om eth ylp h osp h in e (4b). Yield: 86%. 31P NMR
Caution! Phosphines and phosphaalkynes are highly oxidiz-
able and potentially toxic molecules. All reactions should be
carried out under an inert atmosphere in a well-ventilated hood.
1
(CDCl3) δ: -78 (1J PH ) 199 Hz). H NMR (CDCl3) δ: 4.06 (dd,
1
2
2H, J PH ) 199 Hz, J ) 4.7 Hz), 6.18 (dt, 1H, J PH ) 7.3 Hz, J
) 4.7 Hz). 13C NMR (CDCl3) δ: 61.6 (1J CP ) 25.7 Hz). HRMS
calcd for CH3Cl2P: 115.9349; found 115.935. m/z (%): 118 (15.7),
116 (23.4), 103 (6.5), 101 (13.2), 85 (63.9), 83 (100), 80 (35.9), 45
(50.5).
(15) Ro¨sch, W.; Vogelbacher, U.; Allspach, T.; Regitz, M. J . Orga-
nomet. Chem. 1985, 306, 39.

Notes
1,1-Dich lor oeth ylp h osp h in e (4c). Yield: 91%. 31P NMR
J . Org. Chem., Vol. 66, No. 23, 2001 7867
mbar) of both the solvents and products. Thus, the flask cooled
at -10 °C was fitted on a vacuum line, the low boiling
compounds were evaporated and then condensed in a cold trap
(-196 °C). Thus prepared, the ethereal solutions of phos-
phaalkynes can be kept for several months in a freezer (-20
°C) under nitrogen.
P r ep a r a tion of P u r e Low Boilin g P h osp h a a lk yn es (5c-
e,h ,i). To obtain pure samples of phosphaalkynes 5c-e,h ,i,
diglyme should be used as solvent both in the reduction and
elimination steps. The filtered mixture was fitted on a vacuum
line equipped with two cold traps. The first one was cooled at
-40 °C to remove the solvent, and the second one cooled at -120
°C allowed the trapping of the phosphaalkynes 5c-e,h ,i selec-
tively. The mixture was degassed, and the low boiling compounds
were distilled in vacuo (10-1 mbar). At the end of the distillation,
this trap was disconnected from the vacuum line. In these
conditions, the pure phosphaalkynes 5c-e,h ,i should be kept
at low temperature (< -80 °C).
(CDCl3) δ: -46 (1J PH ) 196 Hz). 1H NMR (CDCl3) δ: 2.45 (dt,
3
1
3H, J PH ) 6.7 Hz, J ) 0.5 Hz), 4.33 (dq, 2H, J PH ) 196 Hz, J
) 0.5 Hz). 13C NMR (CDCl3) δ: 42.0 (2J CP ) 8.0 Hz), 80.3 (1J CP
) 25.3 Hz). HRMS calcd for C2H5Cl2P: 129.9506; found 129.951.
m/z (%): 132 (6.8), 131 (2.0), 130 (12.0), 129 (4.7), 128 (1.6), 99
(50.0), 97 (100), 95 (35.9), 79 (9.2), 67 (22.9).
1,1-Dich lor op r op ylp h osp h in e (4d ). Yield: 91%. 31P NMR
(CDCl3) δ: -56 (1J PH ) 197 Hz). 1H NMR (CDCl3) δ: 1.23 (t,
3
3H, J ) 7.1 Hz), 2.44 (qd, 2H, J ) 7.1 Hz, J PH ) 4.1 Hz), 4.20
(d, 2H, J PH ) 197 Hz). 13C NMR (CDCl3) δ: 10.9 (3J CP ) 3.7
1
Hz), 45.4 (2J CP ) 8.0 Hz), 86.2 (1J CP ) 26.0 Hz). HRMS calcd for
C3H7Cl2P: 143.9662; found 143.967. m/z (%): 146 (2.9), 144 (4.1),
143 (12.0), 131 (33.9), 129 (47.8), 113 (23.9), 11 (54.5), 83 (17.7),
81 (26.8), 77 (25.7), 70 (90.5).
1,1-Dich lor op en tylp h osp h in e (4e). Yield: 94%. 31P NMR
(CDCl3) δ: -53.5 (1J PH ) 198 Hz). H NMR (CDCl3) δ: 0.96 (t,
1
3H, J ) 7.3 Hz), 1.40 (qt, 2H, J ) 7.3, 7.3 Hz), 1.69 (tt, 2H, J )
7.2,7.3 Hz), 2.41 (m, 2H, J ) 7.2 Hz, 3J PH ) 5.4 Hz), 4.24 (d, 2H,
1J PH ) 198 Hz). 13C NMR (CDCl3) δ: 13.9, 22.0, 28.5, 51.7, 85.1
(1J CP ) 27.9 Hz). HRMS calcd for C5H11ClP (M - Cl)+: 137.0287;
found 137.028. m/z (%): 146 (2.9), 144 (4.1), 143 (12.0), 131 (33.9),
129 (47.8), 113 (23.9), 11 (54.5), 83 (17.7), 81 (26.8), 77 (25.7),
70 (90.5).
P r ep a r a tion of Cr u d e P h osp h a a lk yn es (5g,k ) in Ab-
sen ce of Solven t. Phosphaalkynes 5g,k decompose on heating,
their boiling point being too high to allow their purification by
distillation in good conditions. When diethyl ether or toluene
are used as solvent, solutions of dichlorophosphines 5g,k can
be concentrated by cooling the solution at -40 °C and removing
the solvent in vacuo. Crude products 5g,k should be kept at low
temperature (< -80 °C).
1,1-Dich lor o-1-t r im et h ylsilylm et h ylp h osp h in e
(4f).
Yield: 85%. 31P NMR (CDCl3) δ: -79 (1J PH ) 196 Hz). 1H NMR
Meth ylid yn ep h osp h in e (5b). Yield: 20%. 31P NMR (CDCl3)
1
(CDCl3) δ: 0.32 (s, 9H), 4.05 (d, 2H, J PH ) 196 Hz). 13C NMR
2
δ: -32 (2J PH ) 44.0 Hz). 1H NMR (CDCl3) δ: 2.90 (d, J PH
)
(CDCl3) δ: -3.62, 73.9 (1J CP ) 29.8 Hz). HRMS calcd for C4H11
-
44.0 Hz). 13C NMR (CDCl3) δ: 158.0 (1J PC ) 56.0 Hz). HRMS
calcd for CHP: 43.98159; found 43.9818. IR (neat, 77 K): 1267
cm-1 (νC≡P).
Cl2PSi: 187.9745; found 187.974. m/z (%): 147 (1.2), 115 (3.6),
113 (4.5), 101 (1.3), 95 (9.9), 93 (28.6), 65 (4.4), 45 (11.3).
1,1-Dich lor o-3-p h en ylp r op ylp h osp h in e (4g). Yield: 85%.
31P NMR (CDCl3) δ: -55 (1J PH ) 197 Hz). 1H NMR (CDCl3) δ:
2.65 (t, 2H, J ) 7.9 Hz), 3.06 (m, 2H, J ) 7.9 Hz), 4.30 (d, 2H,
1J PH ) 197 Hz), 7.16-7.21 (m, 2H), 7.24-7.28 (m, 3H). 13C NMR
(CDCl3) δ: 32.8 (3J CP ) 3.6 Hz), 53.8 (2J CP ) 6.5 Hz), 84.4 (1J CP
Eth ylid yn ep h osp h in e (5c). Yield: 75%. 31P NMR (CDCl3)
δ: -61 (3J PH ) 15.0 Hz). 1H NMR (CDCl3) δ: 2.44 (d, 3H, J PH
3
) 15.0 Hz). 13C NMR (CDCl3) δ: 15.6 (2J PC ) 20 Hz), 170.8 (1J PC
) 49.0 Hz). HRMS calcd for C2H3P: 57.99724; found 57.9972.
IR (neat, 77 K): 1559 cm-1 (νC≡P).
) 26.5 Hz), 126.5, 126.6, 126.6, 128.8. HRMS calcd for C9H11
-
P r op ylid yn ep h osp h in e (5d ). Yield: 77%. 31P NMR (CDCl3)
δ: -62 (3J PH ) 15.0 Hz). 1H NMR (CDCl3) δ: 1.17 (t, 3H, J )
Cl2P: 219.9975; found 219.997.
1,1-Dich lor o-1-bu t-3-en ylp h osp h in e (4h ). Yield: 85%. 31
P
7.5 Hz), 2.34 (dq, 2H, J PH ) 15.0 Hz, J ) 7.5 Hz). 13C NMR
3
NMR (CDCl3) δ: -57 (1J PH ) 198 Hz). H NMR (CDCl3) δ: 3.14
(tm, 2H, J ) 5.7 Hz), 4.28 (d, 2H, 1J PH ) 198 Hz), 5.30 (dm, 1H,
J ) 17.0 Hz), 5.32 (dm, 1H, J ) 9.3 Hz), 5.95 (ddt, 1H, J ) 17.0,
9.3, 5.7 Hz). 13C NMR (CDCl3) δ: 55.8 (2J CP ) 11.6 Hz), 83.1
(1J CP ) 25.3 Hz), 121.1 (3J CP ) 5.7 Hz), 131.6. HRMS calcd for
C4H7Cl2P: 155.9662; found 155.966.
1
(CDCl3) δ: 14.8 (3J PC ) 7.6 Hz), 19.4 (2J PC ) 19.4 Hz), 177.0
(1J PC ) 44.3 Hz). HRMS calcd for C3H5P: 72.01289; found
72.0131. IR (neat, 77 K): 1552 cm-1 (νC≡P).
P en tylid yn ep h osp h in e (5e). Yield: 81%. 31P NMR (CDCl3)
δ: -59 (3J PH ) 14.7 Hz). 1H NMR (CDCl3) δ: 0.91 (t, 3H, J )
7.3 Hz), 1.45 (tq, 2H, J ) 7.3, 7.3 Hz), 1.53 (tt, 2H, J ) 7.3, 6.8
Hz), 2.37 (td, 2H, 3J PH ) 14.7 Hz, J ) 6.8 Hz). 13C NMR (CDCl3)
δ: 13.6, 21.6, 29.3 (2J PC ) 19.6 Hz), 31.7 (3J PC ) 6.6 Hz), 176.4
(1J PC ) 43.0 Hz). HRMS calcd for C5H9P: 100.0442; found
100.044. IR (neat, 77 K): 1545 cm-1 (νC≡P).
1,1-Dich lor o-1-p en t-3-en ylp h osp h in e (4i). Yield: 85%. 31
P
1
NMR (CDCl3) δ: -53 (1J PH ) 198 Hz). H NMR (CDCl3) δ: 2.52
1
(m, 4H), 4.28 (d, 2H, J PH ) 198 Hz), 5.07 (d, 1H, J ) 10.2 Hz),
5.13 (d, 1H, J ) 17.5 Hz), 5.86 (ddt, 1H, J ) 17.5, 10.2, 5.9 Hz).
13C NMR (CDCl3) δ: 30.5 (3J PC ) 4.0 Hz), 50.9 (2J PC ) 7.2 Hz),
84.6 (1J PC ) 26.4 Hz), 116.0, 135.9. HRMS calcd for C5H8Cl2P
(M - H)+: 168.9741; found 168.975.
3-P h en ylp r op ylid yn ep h osp h in e (5g). Yield: 60%. 31P
NMR (CDCl3) δ: -56.8 (3J PH ) 14.9 Hz). 1H NMR (CDCl3) δ:
2.60 (m, 2H, J ) 6.6 Hz), 3.08 (m, 2H, J ) 6.6 Hz), 7.15-7.28
1,1-Dich lor o-1-p h en ylm eth ylp h osp h in e (4j). Yield: 55%.
(m, 5H). 13C NMR (CDCl3) δ: 29.9 (3J PC ) 7.0 Hz), 35.3 (2J PC
7.0 Hz), 126.4, 128.4, 128.6, 140.1, 174.0 (1J PC ) 45.3 Hz).
)
31P NMR (CDCl3) δ: -30 (1J PH ) 198 Hz). 1H NMR (CDCl3) δ:
1
4.59 (d, 2H, J PH ) 198 Hz), 7.04-7.21 (m, 3H), 7.80-7.84 (m,
2H). 13C NMR (CDCl3) δ: 83.0 (1J PC ) 27.6 Hz), 125.6 (3J PC
)
Bu t-3-en ylid yn ep h osp h in e (5h ). Yield: 75%. 31P NMR
6.9 Hz), 127.6 (2J PC ) 17.1 Hz) 128.4, 129.1.
(CDCl3) δ: -52 (3J PH ) 15.3 Hz). H NMR (CDCl3) δ: 2.73 (ddt,
1
2H, 3J PH ) 15.3 Hz, J ) 5.4, 1.7 Hz), 4.92 (ddt, 1H, J ) 9.9, 1.7,
1.7 Hz), 5.12 (ddt, 1H, J ) 17.0, 1.7, 1.7 Hz), 5.50 (ddtd, 1H, J
1,1-Dich lor o-1-cycloh exylm eth ylp h osp h in e (4k ). Yield:
84%. 31P NMR (CDCl3) δ: -55 (1J PH ) 201 Hz). 1H NMR (CDCl3)
) 17.0, 9.9, 5.4 Hz, J PH ) 0.9 Hz). 13C NMR (CDCl3) δ: 33.3
4
1
δ: 1.10-2.22 (m, 11H), 4.23 (d, 2H, J PH ) 201 Hz). 13C NMR
(2J PC ) 19.5 Hz), 116.4, 132.0 (3J PC ) 6.9 Hz), 170.2 (1J PC ) 46.3
Hz). HRMS calcd for C4H5P: 84.01289; found 84.0128.
P en t-4-en ylid yn ep h osp h in e (5i). Yield: 72%. 31P NMR
(CDCl3) δ: -57 (3J PH ) 15.2 Hz). 1H NMR (CDCl3) δ: 2.31 (m,
2H, J ) 6.5 Hz), 2.46 (m, 2H, J ) 6.5, 6.6 Hz), 5.03 (m, 1H, J )
10.3 Hz), 5.08 (m, 2H, J ) 17.0 Hz), 5.82 (m, 1H, J ) 6.6, 10.3,
17.0 Hz). 13C NMR (CDCl3) δ: 28.7 (2J PC ) 19.7 Hz), 33.0 (3J PC
) 7.2 Hz), 115.4, 135.6, 173.8 (1J PC ) 45.0 Hz). HRMS calcd for
C5H7P: 98.02854; found 98.0284.
(CDCl3) δ: 25.7, 25.9, 28.9 (3J PC ) 5.1 Hz), 54.7(2J PC ) 9.9 Hz),
90.4 (1J PC ) 31.7 Hz). HRMS calcd for C7H12Cl2P (M - H)+:
197.0054; found 197.006.
P r ep a r a tion of P h osp h a a lk yn es (5b-e,g-i,k ). Gen er a l
P r oced u r e. The solution of R-dichlorophosphines 5b-e,g-i,k
(50 mmol in Et2O, diglyme or toluene) cooled to -40 °C was
added dropwise through a flex needle to a cooled (-60 °C)
solution of DBU (1.2 10-1 mol) diluted in the desired solvent
(200 ml) at a rate to maintain the temperature under -60 °C.
A part of the DBU-HCl salt precipitated. At the end of the
addition, the mixture was allowed to warm to -10 °C. Dry and
degassed pentane (100 mL) was added to the solution to
precipitate all the ammonium salts. The mixture was filtrated
on Celite under nitrogen and kept at low temperature (-50 °C).
P u r ifica tion of th e Eth er ea l Solu tion s of Low Boilin g
P h osp h a a lk yn es (5b-e,h ,i). When diethyl ether was used as
solvent, the impurities contained in the crude ethereal solution
of the phosphaalkynes 5b-e,h ,i (excess of DBU and residual
salts) were removing by trap-to-trap distillation in vacuo (10-1
1-Cycloh exylm eth ylid yn ep h osp h in e (5k ). Yield: 73%. 31
P
NMR (CDCl3) δ: -62 (3J PH ) 14.9 Hz). 1H NMR (CDCl3) δ: 1.12-
1.67 (m, 10H), 2.25 (m, 1H). 13C NMR (CDCl3) δ: 24.4, 25.4,
33.1, 38.8 (2J PC ) 18.9 Hz), 129.1 (3J PC ) 6.6 Hz), 180.4 (1J PC
35.5 Hz).
)
P r ep a r a tive Syn th esis of (5c). A suspension of LiAlH4 (22.8
g, 0.6 mol) in freshly distilled diethyl ether (400 mL) was cooled
to -70 °C, and AlCl3 (240 g, 1.8 mol) was added in several
portions. After warming up to -10 °C, then cooling to -80 °C,
the phosphonate 1c (157.2 g, 0.6 mol) in diethyl ether (200 mL)

7868 J . Org. Chem., Vol. 66, No. 23, 2001
Notes
1
was added dropwise at a rate to maintain the temperature under
-70 °C. The mixture was then allowed to warm to -10 °C. To
remove the aluminum salts, purification of the ethereal solution
of 4c was performed by distillation in vacuo and condensation
of the low boiling compounds in a 1 L three-necked flask
immersed in a liquid nitrogen bath. This solution cooled to -
40 °C was then added dropwise through a flex needle to a cooled
(-90 °C) solution of DBU (192 g, 1.26 mol) in Et2O (200 mL) at
a rate to maintain the temperature under -60 °C. A salt (DBU-
HCl) precipitated. At the end of the addition, the mixture was
allowed to warm to -10 °C and purified by distillation in vacuo
and condensation of the volatile products at low temperature
(-196 °C). The overall yield was estimated to be 66% (0.4 mol
of CH3CtP) by H and 31P NMR spectroscopy with two 200 µL
samples of solution using respectively 5 µL of dichloromethane
and 5 µL of Bu3P as internal reference. Solutions of 5c were
kept several months in a freezer.
Su p p or tin g In for m a tion Ava ila ble: 400-MHz 1H, 100-
MHz 13C and 121-MHz 31P NMR spectral data of phosphonates
1g,i,k , 2k , 3k . Copies of 1H and 13C NMR spectra for
compounds 1g, 1i, 1k , 2k and 3k . This material is available
free of charges via the Internet at http://pubs.acs.org.
J O010612H