Regiocontrol in the palladium-catalyzed hydrophosphinylation of terminal alkynes

Article abstract of DOI:10.1016/j.jorganchem.2010.08.018

The regioselectivity of the palladium-catalyzed hydrophosphinylation of terminal alkynes was investigated. Complementary conditions to achieve the predominant formation of either the linear or the branched alkenyl-H-phosphinate products were identified. W

Full text of DOI:10.1016/j.jorganchem.2010.08.018

Journal of Organometallic Chemistry 696 (2011) 106e111
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Regiocontrol in the palladium-catalyzed hydrophosphinylation of terminal
alkynes
*
Yamina Belabassi, Karla Bravo-Altamirano, Jean-Luc Montchamp
Department of Chemistry, Box 298860, Texas Christian University, Fort Worth, Tx 76129, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
The regioselectivity of the palladium-catalyzed hydrophosphinylation of terminal alkynes was investi-
gated. Complementary conditions to achieve the predominant formation of either the linear or the
branched alkenyl-H-phosphinate products were identified. With Pd/xantphos in acetonitrile, the linear
isomer is generally obtained with good to excellent selectivity, and E-stereospecificity. On the other hand,
by using Pd/dppf in the non-polar solvent toluene, good selectivity for the branched alkenyl-H-phos-
phinate is typically observed. The role of various reaction parameters is studied.
Received 6 July 2010
Received in revised form
11 August 2010
Accepted 12 August 2010
Available online 20 August 2010
Ó 2010 Elsevier B.V. All rights reserved.
Keywords:
Hydrophosphinylation
Phosphorus
Palladium
Regioselectivity
Alkynes
1. Introduction
cross-coupling reactions [7], the limited availability of the starting
alkenyl electrophiles makes the regiocontrolled addition to alkyne
Hydrophosphinylation is defined as the addition of hypophos-
phorous compounds (or, less commonly, H-phosphinates) to
unsaturated hydrocarbons [1]. Some years ago, we discovered the
palladium-catalyzed hydrophosphinylation of alkenes and alkynes
with hypophosphorous compounds ROP(O)H2 [2]. Since that time,
we have reported a few related studies employing metal-catalysis
(Pd, Ni) [3] which are largely complementary to our free-radical
conditions [4]. Regiocontrol is of obvious interest since terminal
alkynes can, at least in principle, lead to both linear and branched
products (least- and most-substituted alkenyl products, respec-
tively). In terms of phosphorusecarbon bond-forming reactions,
the regioselective formation of alkenyl phosphonates from alkynes
has been studied, using various catalysts and additives [1,5]. Tanaka
recently reported the palladium-catalyzed branched-selective
addition of ethyl phenyl-H-phosphinate to terminal alkynes [6]. On
the other hand, and as far as we know, there has not been a study on
the regiocontrolled addition of alkyl phosphinates [ROP(O)H2] to
terminal alkynes. Although the corresponding alkenyl-H-phosphi-
nates can be obtained regiospecifically via palladium-catalyzed
more desirable.
Herein, we report a study of the regiocontrolled addition of alkyl
phosphinates ROP(O)H2 to terminal alkynes. In this hydro-
phosphinylation reaction, many factors are expected to come into
play, including catalyst (Pd/ligand combination), solvent, hypo-
phosphorous compound precursor, and alkyne. Whereas all these
parameters will be important, it would be desirable to find condi-
tions for which diverging regiochemical outcomes can be achieved
for a range of terminal alkynes.
2. Results and discussion
In order to study regioselectivity, 1-octyne was selected initially
as a representative terminal alkyne, relatively unbiased electroni-
cally. Since the reaction presents many variables, various conditions
were investigated. Table 1 summarizes the results of this investi-
gation. The reactions were conducted under comparable conditions
(catalyst loading, stoichiometry, and reaction time) in order to draw
some conclusions. Yields are determined by 31P NMR of homoge-
neous reaction mixtures. This method is appropriate to establish
intrinsic selectivities.
As we initially reported, various ligands can be employed
successfully in our palladium-catalyzed hydrophosphinylation [2].
However, standard conditions typically employ acetonitrile as the
solvent and xantphos as the ligand, so that entry 1 represents
Abbreviations: Xantphos, 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene;
dppf, 1,10-bis(diphenylphosphino)ferrocene; DPEphos, bis(2-diphenylphosphino-
phenyl)ether; DBFphos, 4,6-bis(diphenylphosphino)-dibenzofuran.
* Corresponding author. Tel.: þ1 817 257 6201; fax: þ1 817 257 5851.
E-mail address: j.montchamp@tcu.edu (J.-L. Montchamp).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.08.018

Y. Belabassi et al. / Journal of Organometallic Chemistry 696 (2011) 106e111
107
Table 1
for the preparation of alkyl phosphinates, [9] a different procedure
(method B) was tested in entries 17 and 18. The use of the ami-
nosilicate salt resulted in excellent and complementary regiose-
lectivities. However, the reasons for the improved linear selectivity
observed in entry 17 are not clear at this time. But in toluene, the
poor solubility of the aminosilicate salts could still explain the
dominance of the electronic effects. In each case, the resulting
product was isolated easily, in essentially quantitative yield. The
aminosilicate method presents the added advantage of straight-
forward removal of the silicate byproducts by a simple aque-
ouseorganic extraction (the silicates remain in the aqueous phase)
[3b,7b,9].
Regioselectivity study in the Pd-catalyzed hydrophosphinylation of 1-octyne.
Hex
(1 equiv)
O
P
O
P
H
H
O
P
+
RO
RO
Hex
H
H
RO
Pd/L(1-3 mol%)
3 equiv
Hex
(B)
Branched
CH3CN or Toluene (reflux)
(L)
Linear
Entry
R
Methoda Solvent Catalyst
B/Lb
Ratio
NMR yield, %
(Isolated yield,%)c
A possible rationalization for the results gathered in Table 1
might be as follows: 1) the electronic effect in 1-octyne is
1
2
3
4
5
6
7
8
Bu
Bu
Bu
Bu
Et
Bu
Bu
Bu
Et
Bu
Bu
Bu
Bu
Bu
Bu
Et
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
B
B
CH3CN Pd2dba3/xantphos
1/3.8
3/1
100
97
100
86
45
100
86
100
100
80
63
100
72
Toluene Pd2dba3/xantphos
CH3CN PdCl2/xantphos
Toluene PdCl2/xantphos
Toluene PdCl2/xantphos
CH3CN Pd2dba3/DPEphos
CH3CN Pd2dba3/dppf
1/7.2
2.5/1
2.8/1
1/2.3
1/1.75
13/1
16/1
1/1.5
14/1
drowned in the polar acetonitrile (
whereas the electronic effects favoring the branched isomer
become dominant in toluene (
3
¼ 36.6) in favor of steric effects,
3
¼ 2.4). 2) Steric effects favoring the
linear isomer are seen with Pd/xantphos (although a clear corre-
lation between ligand structure and regioselectivity is negated by
DBFphos), as well as in the small effect of BuOP(O)H2 versus EtOP
(O)H2.
Toluene Pd2dba3/dppf
9
Toluene Pd2dba3/dppf
CH3CN Pd2dba3/DBFphos
Toluene Pd2dba3/DBFphos
CH3CN PdCl2(PPh3)2$2MeLi 2/1
Toluene PdCl2(PPh3)2$2MeLi 4/1
10
11
12
13
14
15
16
17
18
With the conditions identified for 1-octyne, the scope of the
reaction was investigated on other terminal alkynes (Table 2). The
first compound tested was tert-butylacetylene (3,3-dimethyl-1-
butyne) as a test example of a bulky substituent. As expected,
regiocontrol for the linear alkenyl-H-phosphinate was easily ach-
ieved (entries 1a and c). On the other hand, regiocontrol for the
branched product was much lower than with 1-octyne (entries 1b
and d). Nonetheless, in spite of the significant steric bias, the
conditions identified in Table 1 could deliver the branched isomer
as the major product (2e2.6:1).
CH3CN PdCl2(PPh3)2
2/1
8/1
12/1
1/10
16/1
93
Toluene PdCl2dppf$CH2Cl2
Toluene PdCl2dppf$CH2Cl2
CH3CN Pd2dba3/xantphos
Toluene Pd2dba3/dppf
100
100
99 (99)
100 (100)
Et
Et
a
Method A: 3 equiv stock solution ROP(O)H2 (0.5 M), 1 equiv 1-octyne, 1e3 mol%
Pd-L; Method B: 3 equiv H3PO2, 3 equiv (RO)3Si(CH2)3NH2, 3 equiv TFA, 1 equiv 1-
octyne, 1 mol% Pd/L.
b
Ratio of branched/Linear of the crude reaction mixture.
c
Yields were determined by 31P NMR analysis of the crude reaction mixtures and
Cyclopropylacetylene was tried next (Table 2, entry 2). In this
case, erosion of the selectivity for the linear product was observed
(entries 2a and c), but the branched-selective reactions (entries 2b
and d) resulted in exclusive formation of the branched isomer.
This is consistent with the electron-donating effect of the
cyclopropyl group in combination with limited steric hindrance. A
similar increase in branched selectivity has been observed in
hydroboration [10]. Trimethylsilylacetylene (entry 3) gave excellent
regiocontrol consistent with the reaction conditions identified
earlier. Since the carbonesilicon bond is longer than a carbone
carbon bond (compare with entry 1), the steric hindrance is less
difficult to overcome, and in fact the branched product can be
obtained selectively. However, the yield is lowered significantly.
Other terminal acetylenes were tried. Phenylacetylene shows
the expected preference for the linear product (entry 4b) and the
associated lower selectivity under conditions favoring the branched
isomer (entry 4c). Once again, however, conditions were identified
to form either isomer preferentially. The lack of selectivity with the
butyl ester (entry 4a) is difficult to explain. Terminal alkynes con-
taining functional groups remote from the triple bond behave much
like 1-octyne (entries 5 and 6).
Overall, Table 2 shows that the conditions initially identified for
regiocontrolled hydrophosphinylation of 1-octyne are largely
successful and therefore general for other terminal alkynes. While
differences are observed depending on the alkyne substrate, the
predicted trends are holding in all cases. In spite of the mixtures
sometimes obtained, this method should be competitive with our
palladium-catalyzed cross-coupling of alkenyl halides (and tri-
flates) since the starting materials are more readily available and
the overall process is more atom-economical.
integration of all the resonance signals. Products were isolated by chromatography
over silica gel.
a most typical set of conditions. Reasonably good selectivity for the
linear isomer is observed, as we reported before. Switching the
solvent to toluene under otherwise identical conditions results in
a reversal of regioselectivity now favoring the branched isomer.
Entries 3 and 4 show the results when the palladium source is
changed from Pd2dba3 to PdCl2. In acetonitrile, better selectivity for
the linear isomer is achieved, but again this is reversed in toluene,
although the yield is slightly lower. Changing the alkyl phosphinate
from the butyl ester to the ethyl ester results in slightly better
selectivity for the branched isomer, but the yield is significantly
lower (entry 5 versus entry 4).
The influence of the ligand on the regioselectivity can be seen by
comparing entries 1, 6, and 7. The selectivity for the linear isomer
decreases from xantphos, to DPEphos, to dppf. Although this
seemingly correlates with the decreasing ligand’s bite angle
(111ꢀe102ꢀe99ꢀ, respectively), this clearly breaks down with
DBFphos (entry 10) which has a bite angle of 138ꢀ [8]. It should be
noted that the role of bite angle on various reactions, including
regioselectivity in alkene hydroformylation, has been studied [8].
As seen earlier, the solvent effect is similar with all the ligands
with a complete reversal in favor of the branched isomer in toluene.
However, with triphenylphosphine (entries 12e14), the branched
isomer is always favored regardless of the solvent, although once
again a higher selectivity for the branched H-phosphinate is
obtained in toluene.
In terms of experimental convenience and without sacrificing
the yield, these experiments identified dppf and toluene as two key
parameters to produce the branched isomer (entries 8 and 9),
whereas xantphos and acetonitrile deliver good selectivity for the
linear isomer (entries 1 and 3). Since we reported various methods
The results can once again be explained by electronic versus
steric effects. The more electron-donating substituents on the
terminal alkyne favor the formation of the branched isomer
whereas electron-withdrawing substituents favor the linear

108
Y. Belabassi et al. / Journal of Organometallic Chemistry 696 (2011) 106e111
Table 2
Reactivity of terminal alkynes in the hydrophosphinylation reaction.
R1
(1 equiv)
O
P
O
P
H
H
O
H
R1
+
RO
RO
RO
P
H
Pd/L(1 mol%)
R1
3 equiv
(B)
Branched
CH3CN or Toluene (reflux)
12 h
(L)
Linear
Ratio B/Lb
NMR yield, %
a
Entry
Alkyne
R
Method for ROP(O)H2
Solvent
Catalyst
(Isolated yield, %)c
1a
1b
1c
1d
Bu
Bu
Et
A
A
B
B
CH3CN
Toluene
CH3CN
Toluene
Pd2dba3/xantphos
Pd2dba3/dppf
Pd2dba3/xantphos
Pd2dba3/dppf
1/6.7
2.6/1
1/10
2/1
100 (87)
100 (95)
100
Et
100
2a
2b
2c
2d
Bu
Bu
Et
A
A
B
B
CH3CN
Toluene
CH3CN
Toluene
Pd2dba3/xantphos
Pd2dba3/dppf
Pd2dba3/xantphos
Pd2dba3/dppf
1/1
>98/2
1/4
77(66)
100 (81)
100
Et
1/0
100 (100)
3a
3b
Et
Et
B
A
CH3CN
Toluene
Pd2dba3/xantphos
Pd2dba3/dppf
<2/98
>98/2
100 (96)
41
4a
4b
4c
Bu
Et
Et
A
B
B
CH3CN
CH3CN
Toluene
Pd2dba3/xantphos
Pd2dba3/xantphos
Pd2dba3/dppf
1/1
0/1
6/1
56
100 (92)
100
5a
5b
5c
5d
Bu
Bu
Et
A
A
B
B
CH3CN
Toluene
CH3CN
Toluene
Pd2dba3/xantphos
Pd2dba3/dppf
Pd2dba3/xantphos
Pd2dba3/dppf
1/2
10/1
1/5
100 (67)
100 (87)
100
Et
11/1
100
6a
6b
Et
Et
B
A
CH3CN
Toluene
Pd2dba3/xantphos
Pd2dba3/dppf
1/7
9/1
100
100
a
Method A: 3 equiv stock solution ROP(O)H2 (0.5 M), 1 equiv alkyne, 1 mol% Pd/L. Method B: 3 equiv H3PO2, 3 equiv (RO)3Si(CH2)3NH2, 3 equiv TFA, 1 equiv alkyne, 1 mol% Pd/L.
Ratio of branched/Linear of the crude reaction mixture.
b
c
Yields were determined by 31P NMR analysis of the crude reaction mixtures and integration of all the resonance signals. Products were isolated by chromatography over
silica gel.
product. In fact, methyl propiolate is a Michael acceptor (electron-
withdrawing ester group) which can be hydrophosphinylated to
give the linear product, however, metal-catalysis is unnecessary in
this reaction because the alkyne is highly activated towards
conjugate addition. Steric effects have a mitigating role on the
overall regioselectivity: the larger substituents sterically direct the
reaction to the least substituted position, but associated donating
electronic effect can direct the addition to the more-substituted
position. For example the trimethylsilyl group (entries 3a and b) is
both bulky and electron-donating, and so either selectivity could be
achieved.
(2.5:1, entry 3c). The reasons for this slight improvement under
microwave heating are unclear.
Not surprisingly, free-radical additions are completely selective
for the linear product (Table 3, entries 1b and 5), however, the
yields are lower than in the metal-catalyzed processes, and inter-
estingly a mixture of E- and Z-alkenyl-H-phosphinates can often be
obtained [4b]. Nonetheless, our free-radical hydrophosphinylation
[4] can provide a complementary approach in some cases: for
example, propargyl acetate (entry 5) fails to give the desired
addition product in metal-catalyzed processes, because
metal species are involved instead.
p-allyl
Some palladium-free hydrophosphinylation reactions are
summarized in Table 3. The regioselectivities in the NiCl2-catalyzed
hydrophosphinylation of terminal alkynes we reported [3b] are
generally lower than in the comparable Pd-catalyzed reaction. This
is because both terminal and internal alkynes react more readily
with ROP(O)H2 under nickel catalysis than they do under palladium
catalysis [3b]. In the absence of significant steric or electronic bia-
ses, the nickel-catalyzed hydrophosphinylation leads to regioiso-
meric mixtures with poorer selectivities. For example, 1-octyne
gives a 3:1 mixture of linear versus branched product (entry 1a)
under conditions similar to Table 1, entry 17; and (trimethylsilyl)
acetylene gave only the linear isomer (entry 2). Phenylacetylene
gave a 1:1 mixture (entries 3a and b), but under microwave irra-
diation, a slightly better branched to linear ratio was obtained
Few reports of the addition of phenyl-H-phosphinates to
alkynes have appeared [5a,6,11]. In all cases, the reactions are
limited to PhP(O)(OR)H (Scheme 1). In Tanaka and Nume’s work [6]
with PhP(O)(OEt)H and 5 mol% Pd(OAc)2, the branched isomer is
always preferred, even on styrene derivatives, regardless of solvent
and ligand (even xantphos); with the exception of ethanol, or PR3 in
large excess over the amount of palladium (P/Pd > 1.5). Addition-
ally, in their work, trimethylsilylacetylene and internal alkynes did
not react. In one case, regiocontrol in a nickel-catalyzed reaction
could be achieved through the use of solvent and ligand choice, and
the presence or absence of an additive (Ph2P(O)(OH)) [5a]. Another
case reported the branched-selective palladium-catalyzed addition
of menthyl phenyl-H-phosphinate in the presence of an additive
[11a]. Finally, a single example of a copper-catalyzed addition to

Y. Belabassi et al. / Journal of Organometallic Chemistry 696 (2011) 106e111
109
Table 3
Palladium-free hydrophosphinylation conditions.
R1
(1 equiv)
O
P
O
P
H
H
O
P
R1
+
RO
RO
H
H
RO
catalyst or radical initiator
CH3CN (reflux)
R1
(B)
Branched
(L)
Linear
Entry Alkyne
R
Method for Conditions
ROP(O)H2
Ratio
B/L
NMR yield, %
(Isolated
a
yield, %)b
c
1a
1b
Et
Et
A
B
NiCl2
1/3
(100)
(68)
AIBNd
0/1e
c
2a
2b
Et
Et
B
B
NiCl2
0/1
0/1
(75)
72 (41)
NiCl2, MWc,f
c
3a
3b
3c
Et
Et
Et
A
B
B
NiCl2
NiCl2
1/1
1/1
(100)
(40)
c
NiCl2, MWc,f 2.5/1
97
c
4
Et
B
NiCl2
3/1
(42)
5a
5b
Et
Bu
B
B
AIBNd
AIBNd
0/1
0/1
(54)
(51)
a
Method A: 2 equiv H3PO2, 2 equiv (RO)3Si(CH2)3NH2, 2 equiv TFA, 1 equiv
alkyne. Method B: 2 equiv stock solution ROP(O)H2 (0.5 M), 1 equiv alkyne.
b
Yields were determined by 31P NMR analysis of the crude reaction mixtures and
integration of all the resonance signals. Ratios refer to reaction mixture prior to
purification. Products were isolated by chromatography over silica gel.
c
2e3 mol% NiCl2, see reference 3b.
d
0.1 equiv AIBN þ 0.1 equiv AIBN after 6 h, see reference 4b.
Scheme 1. Regiocontrolled additions of phenyl-H-phosphinates to terminal alkynes.
e
trans/cis ¼ 3/1.
f
MW ¼ microwave heating.
4. Experimental section
styrene produced the linear product regiospecifically [11b]. While
these reactions are obviously different from ours, highly polar
ethanol and DMSO might similarly overwhelm the intrinsic elec-
tronic effects to provide the linear products.
4.1. Preparation of a stock solution of AlkOP(O)H2
This was conducted as described in Ref. [9]. In a typical proce-
dure, a solution (or suspension) of concentrated H3PO2 (100 mmol),
alkoxysilane (70 mmol for (RO)4Si, or 200 mmol for (RO)2SiMe2) in
the appropriate volume of solvent (CH3CN, toluene) to create
a 0.5 M solution, is refluxed for 2 h under a N2 atmosphere. After
cooling to room temperature, the stock solution was kept at room
temperature under N2. Less than 10% decomposition was detected
after 2 months.
In the present study, a rare example of a regio-divergent (or
regio-complementary) outcome through the simple selection of
solvent and ligand is provided. Since the cross-coupling of
alkenyl-H-phosphinates with aryl halides is possible [3b], as well
as many other reactions to functionalize H-phosphinates, our
method also provides a significantly more flexible approach
towards alkenylearyl-phosphinates (and other compounds) than
the branched-selective Tanaka reaction (and the related addi-
tions of PhP(O)(OR)H), both in terms of substitution pattern and
amount of palladium used.
4.2. General procedure for the Pd-catalyzed hydrophosphinylation
of AlkOP(O)H2 to terminal alkynes. Table 1 e method A
To a mixture of the alkyne (2 mmol) and the catalyst (2 mol%
relative to the alkyne) was added a solution of ROP(O)H2 (6 mmol)
in CH3CN or toluene (10 mL, 0.5 M) at room temperature. The
mixture was stirred at reflux until completion of the reaction (NMR
monitoring on a sample of the crude reaction mixture). The mixture
was then concentrated in vacuo. The residue was diluted with
EtOAc and washed with 1 M aqueous NaHCO3, then brine. Drying
over MgSO4 and concentration afforded the crude compound,
which was purified by radial chromatography (hexanes, 100% v/v to
EtOAc, 100% v/v). The product was generally obtained as a light
yellow oil.
3. Conclusion
Straightforward and atom-economical reaction conditions have
been identified to achieve the regioselective hydrophosphinylation
of terminal alkynes. Whereas the interplay between electronic and
steric effects in the alkyne is obviously important, simple choice of
solvent and ligand can afford the formation of either linear or
branched alkyl-H-phosphinate, selectively. Toluene solvent and
dppf ligand favor the formation of the branched isomer, whereas
acetonitrile and xantphos favor the formation of the linear product.
Useful regioselectivities have been achieved. Although our palla-
dium-catalyzed cross-coupling can deliver alkenyl-H-phosphinates
products regiospecifically, the need for the appropriate alkenyl
electrophiles offsets its superior regiochemical outcome and makes
the present study quite competitive.
4.3. Representative procedure for Table 1 e method B
To a mixture of concentrated H3PO2 (0.396 g, 6 mmol, 3 equiv)
and 3-aminopropyltriethoxysilane (1.33 g, 6 mmol, 3 equiv) in

110
Y. Belabassi et al. / Journal of Organometallic Chemistry 696 (2011) 106e111
toluene (12 mL) were added 1-octyne (0.36 mL, 0.28 g, 2 mmol,
1 equiv) and trifluoroacetic acid (0.460 mL, 0.68 g, 6 mmol,
3 equiv), after stirring for 5 min at rt, Pd2dba3 (0.0092 g, 0.01 mmol,
1 mol% Pd) and dppf (1.2 mg, 0.02 mmol) were added and the
reaction mixture was heated at reflux for 12 h. At this point the
reaction is not homogeneous because the silicates get polymerized
forming sticky gels at the bottom of the flask. After cooling to rt, 31P
NMR of the reaction mixture revealed the formation of the products
at 28.9 ppm (branched isomer) and 24.2 ppm (linear isomer) in
a ratio of 16/1. The mixture was then diluted with EtOAc and
washed successively with 2 M aqueous HCl (1ꢁ). The aqueous
phase was extracted with EtOAc (2ꢁ) and the combined organic
fractions were washed with brine. Drying over MgSO4 and
concentration under reduced pressure afforded the products along
with 10e20% of diethyl phosphite (EtO)2P(O)H, which was elimi-
nated under reduced pressure (0.1 mm Hg, 40 ꢀC, 12 h). The pure
product was then obtained as a mixture of isomers in the form of
light yellow oil (0.464 g, 100%).
J ¼ 7 Hz, 1H), 0.64 (dm, J ¼ 9 Hz, 4H); 13C NMR (CDCl3, 75.45 MHz)
d
143.5 (d, JPC ¼ 127 Hz), 125.4 (d, JPCC ¼ 14 Hz), 65.7 (d, JPOC ¼ 7 Hz),
32.5, 18.8, 13.5, 11.2 (d, JPCC ¼ 5 Hz), 7.2, 6.6; 31P NMR (CDCl3,
36.441 MHz)
d
27.9 (dqq, JPH ¼ 553 Hz, J ¼ 25, 9 Hz).
4.3.6. Ethyl (1-cyclopropyl-vinyl) phosphinate (Table 2, entry 2d)
1H NMR (CDCl3, 300 MHz)
d
7.17 (d, JPH ¼ 554 Hz, 1H), 5.91 (d,
J ¼ 24 Hz, 1H), 5.65 (d, J ¼ 47 Hz, 1H), 4.22e4.08 (m, 2H), 1.65e1.52
(m, 1H), 1.39 (t, J ¼ 7 Hz, 3H), 0.85 (dm, J ¼ 7 Hz, 2H), 0.65 (dm,
J ¼ 7 Hz, 2H); 13C NMR (CDCl3, 75.45 MHz)
143.4 (d, JPC ¼ 120 Hz),
d
125.5 (d, JPCC ¼ 14 Hz), 62.0 (d, JPOC ¼ 6 Hz), 16.3 (d, JPOCC ¼ 6 Hz),
11.2 (d, JPCC ¼ 18 Hz), 7.2 (d, JPCCC ¼ 4 Hz), 6.6 (d, JPCCC ¼ 5 Hz); 31P
NMR (CDCl3, 36.441 MHz)
d
29.2 (dqq, JPH ¼ 554, 24, 9 Hz).
4.3.7. Ethyl (trans-2-trimethylsilyl-vinyl) phosphinate (Table 2,
entry 3a) [3b]
1H NMR (CDCl3, 300 MHz)
d
7.00 (d, JPH ¼ 551 Hz, 1H), 7.13 (dd,
J ¼ 37, 21 Hz, 1H), 6.28 (ddd, J ¼ 32, 21, 1.5 Hz, 1H), 4.01 (q, J ¼ 7 Hz,
2H), 1.23 (t, J ¼ 7 Hz, 3H), 0.02 (s, 9H); 13C NMR (CDCl3, 75.45 MHz)
4.3.1. Ethyl (trans-oct-1-enyl) phosphinate (major isomer, 91%
purity) (Table 1, entry 17) [2]
d
159.0 (d, JPCC ¼ 3 Hz), 136.9 (d, JPC ¼ 118 Hz), 64.2 (d, JPOC ¼ 6 Hz),
18.5 (d, JPOCC ¼ 6 Hz), 0.0 (s, 3C); 31P NMR (CDCl3, 36.441 MHz)
1H NMR (CDCl3, 300 MHz)
d
7.18 (d, JPH ¼ 554 Hz, 1H), 6.81 (ddt,
d
23.7 (dqt, JPH ¼ 551 Hz, J ¼ 30, 9 Hz).
J ¼ 24 Hz, J ¼ 17, 7 Hz, 1H), 5.79 (dd, J ¼ 24, 17 Hz, 1H), 4.3e4.24 (m,
2H), 2.19e2.33 (m, 2H), 1.4e1.55 (m, 2H), 1.38 (t, J ¼ 6 Hz, 3H),
1.18e1.4 (m, 6H), 0.89 (t, J ¼ 7 Hz, 3H); 13C NMR (CDCl3, 75.45 MHz)
4.3.8. Ethyl (trans-styryl) phosphinate (Table 2, entry 4b) [3b]
1H NMR (CDCl3, 300 MHz)
7.60e7.48 (m, 2H), 7.46e7.38 (m,
d
d
155.3 (d, JPCC ¼ 5 Hz), 119.7 (d, JPC ¼ 131 Hz), 61.9 (d, JPOC ¼ 6 Hz),
3H), 7.35 (d, JPH ¼ 562 Hz, 1H), 6.40 (d, J ¼ 22 Hz, 1H), 6.37 (d,
34.4 (d, JPCCC ¼ 20 Hz), 32.0, 29.4 (d, JPCCCCC ¼ 8 Hz), 27.8, 22.8, 16.4
J ¼ 5 Hz, 1H), 4.24e4.19 (m, 2H), 1.41 (t, J ¼ 7 Hz, 3H); 13C NMR
(d, JPOCC ¼ 7 Hz), 14.3; 31P NMR (CDCl3, 121.47 MHz)
JPH ¼ 554 Hz).
d
25.8 (dm,
(CDCl3, 75.45 MHz)
d
149.9 (d, JPCC ¼ 7 Hz), 134.7 (d, JPCCC ¼ 21 Hz),
130.9, 129.2 (2C), 128.1 (2C), 116.6 (d, JPC ¼ 133 Hz), 62.3 (d,
JPOC ¼ 6 Hz), 16.7 (d, JPOCC ¼ 7 Hz); 31P NMR (CDCl3, 36.441 MHz)
4.3.2. Ethyl (1-hexyl-vinyl) phosphinate (major isomer, 94% purity)
(Table 1, entry 18) [2]
d
25.6 (dm, JPH ¼ 561 Hz).
1H NMR (CDCl3, 300 MHz)
d
7.13 (d, JPH ¼ 553 Hz, 1H), 5.95 (d,
4.3.9. Butyl [1-(2-phthalimidoethyl)-vinyl] phosphinate (major
isomer, 91% purity) (Table 2, entry 5b)
JPH ¼ 5 Hz, 1H), 5.91 (d, JPH ¼ 71 Hz, 1H), 4.03e4.24 (m, 2H),
2.18e2.38 (m, 2H), 1.45e1.63 (m, 2H), 1.38 (td, J ¼ 6, 2 Hz, 3H),
1.17e1.4 (m, 6H), 0.89 (t, J ¼ 7 Hz, 3H); 13C NMR (CDCl3, 75.45 MHz)
1H NMR (CDCl3, 300 MHz)
d
7.85 (dd, J ¼ 5, 3 Hz, 2H), 7.72 (dd,
J ¼ 5, 3 Hz, 2H), 7.13 (d, JPH ¼ 561 Hz, 1H), 5.99 (d, J ¼ 26 Hz, 1H),
5.88 (d, J ¼ 49 Hz, 1H), 4.12e3.96 (m, 2H), 3.71 (t, J ¼ 7 Hz, 2H), 2.33
(dt, J ¼ 13, 8 Hz, 2H),1.80e1.56 (m, 2H),1.40 (sext, J ¼ 8 Hz, 2H), 0.93
d
141.8 (d, JPC ¼ 118 Hz), 128.9 (d, JPCC ¼ 14 Hz), 62.3 (d, JPOC ¼ 6 Hz),
31.9, 30.7 (d, JPCCC ¼ 12 Hz), 29.4 (d, JPCCCC ¼ 7 Hz), 28.0 (d,
JPCCCCC ¼ 5 Hz), 22.8, 16.4 (d, JPOCC ¼ 7 Hz), 14.2; 31P NMR (CDCl3,
(t, J ¼ 7 Hz, 3H); 13C NMR (CDCl3, 75.45 MHz)
d 168.5 (2C), 141.5 (d,
121.47 MHz)
d
30.62 (dm, JPH ¼ 553 Hz).
JPC ¼ 119 Hz), 134.1 (2C), 132.0 (2C), 129.4 (d, JPCCC ¼ 14 Hz), 123.3
(2C), 66.2 (d, JPOC ¼ 7 Hz), 37.6, 32.5 (d, JPOCC ¼ 6 Hz), 25.3 (d,
4.3.3. Butyl [(E)-3,3-dimethylbut-1-enyl] phosphinate (major
isomer, 87% purity) (Table 2, entry 1a)
JPCC ¼ 6 Hz), 18.9, 13.7; 31P NMR (CDCl3, 36.441 MHz)
JPH ¼ 563 Hz).
d 28.2 (dm,
1H NMR (CDCl3, 300 MHz)
d
7.18 (d, JPH ¼ 555 Hz, 1H), 6.84e6.62
(m, 1H), 5.78e5.56 (m, 1H), 4.14e4.01 (m, 2H), 1.70 (quint, J ¼ 7 Hz,
Acknowledgments
2H), 1.41 (sext, J ¼ 8 Hz, 2H), 1.08 (s, 9H), 0.94 (t, J ¼ 7 Hz, 3H); 13C
NMR (CDCl3, 75.45 MHz)
d
164.5 (d, JPCC ¼ 5 Hz), 114.8 (d,
We gratefully acknowledge the National Science Foundation
(CHE-0953368) for financial support.
JPC ¼ 131 Hz), 65.8 (d, JPOC ¼ 6 Hz), 32.6 (d, JPCCC ¼ 7 Hz), 28.7, 28.5
(3C), 18.9, 13.7; 31P NMR (CDCl3, 36.441 MHz)
d 25.3 (dm,
JPH ¼ 557 Hz).
Appendix A. Supplementary data
4.3.4. Butyl (1-tert-butyl-vinyl) phosphinate (major isomer, 72%
purity) (Table 2, entry 1b)
Supplementary information associated with this article can be
found in the online version at doi:10.1016/j.jorganchem.2010.08.
018.
1H NMR (CDCl3, 300 MHz)
d
7.20 (d, JPH ¼ 553 Hz, 1H), 5.98 (d,
J ¼ 54.1 Hz, 1H), 5.89 (d, J ¼ 26.9 Hz, 1H), 4.19e3.90 (m, 2H), 1.71
(quint, J ¼ 7 Hz, 2H), 1.42 (sext, J ¼ 8 Hz, 2H), 1.23 (s, 9H), 0.95 (t,
J ¼ 7 Hz, 3H); 13C NMR (CDCl3, 75.45 MHz)
d
151.1 (d, JPC ¼ 120 Hz),
References
126.8 (d, JPCC ¼ 13 Hz), 65.7 (d, JPOC ¼ 6 Hz), 32.6 (d, JPCCC ¼ 7 Hz),
29.8 (3C), 28.5, 19.5, 13.9; 31P NMR (CDCl3, 36.441 MHz)
d 32.2 (dm,
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