Bifunctionalized allenes, part XI: Competitive electrophilic cyclization and addition reactions of 4-phosphorylated allenecarboxylates

Article abstract of DOI:10.1002/hc.21136

The reaction of the 4-phosphorylated allenecarboxylates with different electrophilic reagents such as sulfuryl chloride, bromine, benzenesulfanyl, and benzeneselanyl chlorides takes place with a 5-endo-trig cyclization or 2,3-addition reaction depending on the kind of the substituents in the phosphoryl group. Treatment of the 4-(dimethoxyphosphopyl)-allenoates with electrophiles gives a mixture of 2,5-dihydro-1,2-oxaphospholes and furan-2(5H)-ones in the ratio of about 1.7:1 as a result of the neighboring group participation of phosphonate and carboxylate groups in the cyclization. On the other hand, (3E)-4-(diphenylphosphoryl)-alk-3-enoates were prepared, in moderate yields, by chemo-, regio, and stereoselective electrophilic addition to the C²i￡C³-double bond in the allenoate moiety. A possible mechanism involving cyclization and addition reactions of the 4-phosphorylated allenecarboxylates was proposed.

Full text of DOI:10.1002/hc.21136

Heteroatom Chemistry
Volume 25, Number 1, 2014
Bifunctionalized Allenes, Part XI: Competitive
Electrophilic Cyclization and Addition
Reactions of 4-Phosphorylated
Allenecarboxylates
Ivaylo K. Ivanov, Ivaylo D. Parushev, and Valerij Ch. Christov
Department of Organic Chemistry & Technology, Faculty of Natural Sciences, Konstantin
Preslavsky University of Shumen, BG-9712 Shumen, Bulgaria
Received 18 June 2013; revised 20 October 2013
Chem. 25:60–71, 2014; View this article online at wi-
ABSTRACT: The reaction of the 4-phosphorylated al-
leyonlinelibrary.com. DOI 10.1002/hc.21136
lenecarboxylates with different electrophilic reagents
such as sulfuryl chloride, bromine, benzenesulfanyl,
and benzeneselanyl chlorides takes place with a
5-endo-trig cyclization or 2,3-addition reaction de-
INTRODUCTION
pending on the kind of the substituents in the phospho-
ryl group. Treatment of the 4-(dimethoxyphosphopyl)-
allenoates with electrophiles gives a mixture of 2,5-
dihydro-1,2-oxaphospholes and furan-2(5H)-ones in
the ratio of about 1.7:1 as a result of the neighbor-
ing group participation of phosphonate and carboxy-
late groups in the cyclization. On the other hand,
(3E)-4-(diphenylphosphoryl)-alk-3-enoates were pre-
pared, in moderate yields, by chemo-, regio, and
stereoselective electrophilic addition to the C2 C3-
double bond in the allenoate moiety. A possible
mechanism involving cyclization and addition reac-
tions of the 4-phosphorylated allenecarboxylates was
In the past four decades, synthesis and use of al-
lene derivatives have been expanded in preparative
organic chemistry. The presence of two π electron
clouds separated by a single sp hybridized carbon
atom is the identifying structural characteristic of
allenes, and it is this unique structural and elec-
tronic arrangement that is responsible for the ex-
traordinary reactivity profile displayed by allenic
compounds [1].
Functionalized allenes have attracted a growing
attention because of their versatility as key build-
ing blocks for organic synthesis. The synthetic po-
tential of functionalized allenes has been explored
extensively in recent years, and this has led to the
development of novel methods for the construction
of a variety of functionalized heterocyclic and car-
bocyclic systems [2]. An impressive number of het-
erocyclic systems have been prepared from allenic
starting materials.
ꢀC
proposed. 2013 Wiley Periodicals, Inc. Heteroatom
Correspondence to: Valerij Ch. Christov; e-mail: vchristo@shu-
bg.net.
Dedicated to Professor Toru Minami from Kyushu Institute
of Technology, Kitakyushu, Japan, on the occasion of his 75th
anniversary.
Contract grant sponsor: Research Fund of the Konstantin
Preslavsky University of Shumen.
Contract grant number: RD-08-243/2013.
On the other hand, one of the characteristic reac-
tions of the allenes is the electrophilic addition reac-
tions in which the addition products of the reagent
to the one and/or other double bond of the allenic
system are usually obtained [3]. Functionalized al-
lenes are very interesting substrates as a material of
Contract grant sponsor: National Research Fund of Bulgaria.
Contract grant number: DRNF-02-13/2009.
Contract grant sponsor: Human Resources Development Oper-
ational Programme of the European Union.
Contract grant number: BG051PO001-3.3.06-0003/2012.
ꢀC
2013 Wiley Periodicals, Inc.
60

Competitive Electrophilic Cyclization and Addition Reactions of 4-Phosphorylated Allenecarboxylates 61
R
R1
•
Y2P
OR2
O
O
I
E-Nu
R
E
R
E
E
R1
R
E
R1
Y2(O)P
Nu
R1
CO2R2
R
O
Y
Y2P
R1
CO2R2
P
O
O
CO2R2
Y2P
O
O
Nu
IV
O
V
II
III
SCHEME 1
choice to study the electrophilic addition reactions
on the carbon–carbon double bonds [4–6]. Unlike
the allenic hydrocarbons, the presence of a func-
tional group linked to the allenic system consider-
ably changes the course of the reactions with elec-
trophilic reagents. It has been shown [4–6] that the
reactions proceeded with cyclization of the allenic
system bearing a functional group to give hetero-
cyclic compounds in most of cases. It makes the
investigations on the functionalized allenes, more
specifically in studying their reactions with elec-
trophilic reagents, quite an interesting and topical
task.
Furan-2(5H)-ones (γ -lactones) are important in-
termediates in organic synthesis due to the pres-
ence of the conjugated C C bond as well as the
five-membered lactone ring. Much attention has
been paid to the development of efficient and di-
verse synthetic methods for construction of this five-
membered ring system [7]. Among these, cyclization
involving allenecarboxylic acids and their deriva-
tives, the so-called lactonization reaction, is one of
the most efficient pathways [8]. α-Allenecarboxylic
acids and their esters, disubstituted on the γ -carbon
atom, underwent electrophilic attack on the cen-
tral atom and ring closure to furan-2(5H)-ones
(γ -lactones) when treated with electrophile [8].
On the other hand, literature data on the re-
actions of phosphorylated allenes (phosphonates,
phosphinates, and phosphine oxides) with elec-
trophilic reagents show that depending on the struc-
ture of the starting allenic compound as well as
the type of the electrophile, the reactions proceed
with cyclization of the allenic system bearing phos-
phoryl group (O P C C C) to give heterocyclic
compounds in most cases [4–6]. Thus, the reaction
of electrophilic reagents with dialkyl allenephos-
phonates [4–6] or allenyl phosphine oxides [9–11]
leads to 2,5-dihydro-1,2-oxaphospholes or/and 2,1-
or/and 2,3-adducts or a mixture of them, depend-
ing on the degree of substitution at the C1 and C3
atoms of the allenic system, the nature of these sub-
stituents, and the type of the reagents. Recently, it
was also observed by Ma and co-workers [12–14]
that the electrophilic iodohydroxylation [12], fluo-
rohydroxylation [13], and selenohydroxylation [14]
reactions of allenyl phosphine oxides with iodine,
Selectfluor, and benzeneselanyl chloride, affording
2-iodo(respectively, 2-fluoro or 2-phenylselanyl)-3-
hydroxy-1(E)-alkenyl phosphine oxides with high
regio- and stereoselectivities, which the authors [
12–14] believed to be determined by the neighboring
group participation effect of the diphenyl phosphine
oxide functionality. More recently, we have reported
the reactions of 1-vinyl- [15a] and 3-vinylallenyl
[15b] phosphine oxides with electrophiles leading to
formation of various heterocyclic or highly unsatu-
rated compounds.
As a part of our long-standing studies directed
toward the development of efficient electrophilic cy-
clization reactions of 1,1-bifunctionalized allenes [
16], we become interested in 1,3-bifunctionalized al-
lenes comprising a phosphoryl and an ester groups
such as I (Scheme 1). Of particular interest are the
applications of these groups as temporary trans-
formers of chemical reactivity of the allenic sys-
tem in the synthesis of eventually heterocyclic com-
pounds. This molecule can be considered as a
combination of an allenecarboxylate and an al-
lenephosphonate or allenyl phosphine oxide and
might have different reactivity profiles in elec-
trophilic reactions. Recently, we presented a conve-
nient and efficient method for regioselective synthe-
sis of 4-phosphorylated allenecarboxylates, derived
by an atom economical [2,3]-sigmatropic rearrange-
ment of the mediated alkoxycarbonyl-functionalized
Heteroatom Chemistry DOI 10.1002/hc

62 Ivanov, Parushev, and Christov
Br
Ph
(MeO)2P
Ph
Ph
Br
Ph
CO2Et
Ph
Ph
Br2
•
(MeO)2P
O
+
O
OEt
Solvent
O
P
O
O
MeO
O
O
3db
4db
1d
SCHEME 2
propargyl phosphites or phosphinites formed by a
reaction of the alkyl 2-hydroxy-alk-3-ynoates with
dimethylchlorophosphite or diphenylchlorophos-
phine, respectively, in the presence of a base [16i].
We initiated this study with the electrophilic
cyclization reaction of the ethyl 4-(dimethoxyphos-
phoryl)-2,4-diphenyl-buta-2,3-dienoate 1d with
bromine (Scheme 2). We established that the
reaction occurs with cyclization by neighboring
group participation of the phosphonate and the
carboxylate groups with formation of a mixture of
the ethyl 4-bromo-2-methoxy-2-oxo-3,5-diphenyl-
RESULTS AND DISCUSSION
It should be pointed out that conceptually there
exist two distinct modes of cyclization of the 4-
phosphorylated 2,3-alkadienoates if the electrophilic
atom forms a new bond with the central carbon of
the allenic system, which seems likely [4–8]. It is
evident that these pathways are closely connected
with the intramolecular neighboring group partici-
pation of the phosphoryl and/or the ester groups as
internal nucleophile(s) in the final step of the cy-
clization. Besides the 5-endo-trig cyclizations [17] to
the 2,5-dihydro-1,2-oxaphosphole II or to the furan-
2(5H)-one (butenolide, γ -lactone) III, electrophilic
addition might afford the 3,2-adduct IV and/or the
3,4-adduct V (Scheme 1).
2,5-dihydro-1,2-oxaphosphole-5-carboxylate
3db
and the dimethyl (3-bromo-5-oxo-2,4-diphenyl-2,5-
dihydrofuran-2-yl)phosphonate 4db. We tried to
optimize the reaction conditions to get a useful
selectivity and the best total yield for the mixture
of products by studying the electrophile equivalent,
reaction temperature, time, and solvent effect.
Note that when the reaction was conducted in
ClCH2CH2Cl at room temperature, thin-layer chro-
matography (TLC) showed that the two reactants
still interacted and the reaction was completed
within 4 h with the formation of the desired prod-
ucts. It is necessary to carry out this reaction under
argon atmosphere since the electrophilic reagents
are sensitive to the moisture in air. The desired
products 3db and 4db were obtained in 50% total
yield (see Table 1, entry 1). When the reaction was
carried out at reflux, it was complete within 3 h
This paper is a part of our general synthetic
strategy for investigation of the scope and limita-
tions of the electrophilic cyclization reactions of 1,3-
bifunctionalized allenes. Herein, we wish to report
our recent results of these investigations.
TABLE 1 Screening of the Reaction Conditions for the Electrophilic Cyclization Reaction of the Ethyl 4-(Dimethoxyphosphoryl)-
2,4-diphenyl-buta-2,3-dienoate 1d with Bromine
Yieldb(%)
Entry
Bromine (Equiv.)
Solventa
Reaction Temperature (◦C)
Reaction Time (h)
3db
4db
3db:4db
1
2
3
4
5
6
7
8
1.0
1.5
1.5
1.5
1.5
1.2
1.2
1.2
1.2
1.0
1.2
1.5
2.0
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
ClCH2CH2Cl
CHCl3
EtOH
MeCN
MeNO2
Benzene
CH2Cl2
CH2Cl2
CH2Cl2
rt
Reflux
–78
–20
–20
–30
–20
–20
rt
4
3
5
5
4
6
8
7
8
8
5
6
7
31
24
21
20
22
18
19
17
15
46
50c
45
39
19
15
12
11
13
10
11
10
9
25
28c
24
22
1.63:1
1.60:1
1.75:1
1.81:1
1.69:1
1.80:1
1.73:1
1.70:1
1.67:1
1.84:1
1.79:1
1.88:1
1.77:1
9
10
11
12
13
rt
–20
–20
–20
CH2Cl2
aReaction was carried out in the appropriate solvent (10 mL + 10 mL).
bYields determined by 1H and 31P NMR analysis.
cIsolated yields by chromatographical purification on silica gel.
Heteroatom Chemistry DOI 10.1002/hc

Competitive Electrophilic Cyclization and Addition Reactions of 4-Phosphorylated Allenecarboxylates 63
E
R1
R1
R
E
R
E-Nu
•
R
R1
CO2R2
+
O
(MeO)2P
OR2
CH2Cl2
O
P
(MeO)2P
O
O
O
MeO
O
O
1
3
4
E-Nu = Cl-Cl, Br-Br, PhS-Cl, PhSe-Cl
SCHEME 3
R1
and the yield was considerably lower (39%, entry
2). With 1.5 equiv. of bromine in ClCH2CH2Cl and
CHCl3, the yield is lower (entries 3–5). Polar solvents
such as ethanol, acetonitrile, and nitromethane gave
low yields, even with longer reaction times (6–8 h)
and mainly recovered starting materials (entries
6–8, respectively). Similar yield was obtained in
benzene as a solvent (entries 9). Fortunately, when
dichloromethane was used as a solvent at room
temperature and minus temperatures for 5–8 h
(entries 10–13), the yield improved to 78% when the
temperature was –20◦C for 5 h (entry 11). It should
be noted that temperature of –20oC is the best and
most convenient: When the temperature is higher
or lower, the yield is worse (compare entries 1, 2,
9, and 10 with entries 3 and 6). When 1.2 equiv. of
electrophilic reagent were used, the reaction was
high yielding (entry 11). We therefore, conducted
the remainder of the reactions in dichloromethane
at –20◦C using 1.0 equiv. of the 4-phosphorylated
allenoates 1a-d and 1.2 equiv. of the electrophilic
reagent for 5 h. The ratio of the products 3db
and 4db was 1.79:1, and the products were fully
characterized by means of NMR (1H, 13C, and 31P),
and IR spectroscopy.
R
E
R
R1
E-Nu
•
Ph2P
OR2
Ph2P
CH2Cl2
O
CO2R2
O
O
Nu
2
5
SCHEME 4
the reaction under this set of standard reaction
conditions in the favored 5-endo-trig mode affords
mixtures of the 5-ethoxycarbonyl-2,5-dihydro-1,2-
oxaphospholes 3 and the 5-(dimethoxyphosphoryl)-
furan-2(5H)-ones 4 in the ratio from 1.59:1 to 1.82:1
as a result of the neighboring group participation
of phosphonate and carboxylate groups in the
cyclization in good to excellent yields irrespective of
the nature of the substituents on the allenic system
and the ester group. The reaction scope is wide: R
can be propyl, butyl, or phenyl, R1 can be methyl or
phenyl, R2 can be methyl or ethyl, and E can be Cl,
Br, PhS, and PhSe.
To establish the generality of this methodol-
ogy, the reaction of the 4-(diphenylphosphoryl)-
allenecarboxylates 2a–d with different electrophilic
reagents such as sulfuryl chloride, bromine, ben-
zenesulfanyl chloride, and benzeneselanyl chlo-
ride was examined. To our surprise, when we
applied the current standard conditions to the
1,3-bifunctionalized allenes comprising a phos-
phine oxide and alkoxycarbonyl groups such as
2 (Scheme 4), instead of the mixture of the
Having determined the optimized reaction
conditions, we explored the scope of the elec-
trophilic cyclization reaction of the alkyl 4-
(dimethoxyphosphoryl)-alka-2,3-dienoates
1a–d
(Scheme 3), and the results that we obtained are
summarized in Table 2. It should be noted that
TABLE 2 Synthesis of the 5-Ethoxycarbonyl-2,5-dihydro-1,2-oxaphospholes 3 and the 5-(Dimethoxyphosphoryl)-furan-2(5H)-
ones 4 by Electrophilic Cyclization Reaction of the 4-(Dimethoxylphosphoryl)-allenecarboxylates 1a–d
Entry
Allene
R
R1
R2
E
Nu
Time (h)
3, Yielda (%)
4, Yielda (%)
Ratio
1
2
3
4
5
6
7
8
9
1a
1a
1b
1b
1c
1c
1d
1d
1d
1d
Pr
Pr
Pr
Me
Me
Ph
Ph
Me
Me
Ph
Ph
Ph
Ph
Et
Et
Me
Me
Et
Et
Et
Et
Et
Et
Cl
SePh
Br
SePh
Br
SePh
Cl
Br
SPh
SePh
Cl
Cl
Br
Cl
Br
Cl
Cl
Br
Cl
Cl
3
5
6
4
3.5
5
4
5
9
3aa, 50
3ad, 46
3bb, 45
3bd, 48
3cb, 51
3cd, 46
3da, 49
3db, 50
3dc, 45
3dd, 47
4aa, 28
4ad, 28
4bb, 28
4bd, 29
4cb, 28
4cd, 29
4da, 27
4db, 28
4dc, 28
4dd, 27
1.79:1
1.64:1
1.61:1
1.66:1
1.82:1
1.59:1
1.81:1
1.79:1
1.61:1
1.74:1
Pr
Bu
Bu
Ph
Ph
Ph
Ph
10
7.5
aIsolated yields by chromatographical purification on silica gel.
Heteroatom Chemistry DOI 10.1002/hc

64 Ivanov, Parushev, and Christov
TABLE 3 Synthesis of the (3E)-4-(Diphenylphosphoryl)alk-
3-enoates 4 by Electrophilic Addition Reaction of the 4-
(Diphenylphosphoryl)-allenecarboxylates 2a–d
leniranium) ion A after attack on the relatively more
electron-rich C2 C3-double bond or the ion B af-
ter attack on the relatively more electron-deficient
C3 C4-double bond. Subsequently, the ions A and
B are easily transformed into the more stable five-
membered cyclic ions C and D via the neighbor-
ing group participation of the oxygen atom of the
phosphonate (path a) and carboxylate functionali-
ties (path b), respectively. Furthermore, the interme-
diates C and D undergo nucleophilic attacks to MeO
or R2O groups and elimination of methyl (MeNu) or
alkyl halides (R2Nu) affording the final cyclic prod-
ucts 3 and 4 (path a and path b). On the other hand,
in the case of 4-(diphenylphosphoryl)-allenoates 2a–
d (Y is Ph) as starting materials, the formation of
the final (3E)-4-(diphenylphosphoryl)alk-3-enoates
5 can be considered in terms of the assumption
for the nucleophilic attack on the cyclic three-
membered onium ions A (path c) leading to the
formation of the (3E)-2,3-adduct 5. The stereoselec-
tivity observed may be explained by the favorable
trans arrangement of the electrophile and the phos-
phine oxide group and anti-attack of the external
nucleophile Nu in the onium ions A (path c). These
are presumed to arise from attack on the allenic
C2 C3 double bond anti to the functional groups,
which assisted in the two cyclizations by neighbor-
ing groups participation as an internal nucleophiles.
On the other hand, a possible explanation of the two
types cyclization observed consists of the following.
In the first case (Scheme 3), the reason for the pre-
dominant participation of the phosphonate group as
an internal nucleophile is the higher nucleophilicity
of the phosphoryl oxygen in comparison with car-
boxylic one, which is in connection with the more
polarization of the phosphoryl group. In the second
case (Scheme 4), this reaction pathway is probably
Time 5, Yielda
Entry Allene
R
R1 R2
E
Nu
Br
(h)
(%)
1
2
2a
2a
2b
2b
2c
2c
2d
2d
2d
2d
Bu Me Et Br
4
5ab, 70
5ad, 64
5bb, 73
5bd, 65
5cb, 72
5cd, 64
5da, 69
5db, 71
5dc, 66
5dd, 63
Bu Me Et SePh Cl
Bu Ph Me Br Br
Bu Ph Me SePh Cl
Ph Me Et Br Br
Ph Me Et SePh Cl
Ph Ph Et Cl
Ph Ph Et Br
Ph Ph Et SPh
6
5
7
6
3
4
5
6
6.5
5.5
7
7
8
Cl
Br
Cl
9
10
7.5
8
Ph Ph Et SePh Cl
aIsolated yields by chromatographical purification on silica gel.
2,5-dihydro-1,2-oxaphospholes 3 and the furan-
(5H)-ones 4, the acyclic compounds 5 were iso-
lated in 63–73% yield after stirring for several
hours at –20◦C and for 1 h to room temper-
ature. The results are summarized in Table 3.
Interestingly, this protocol can also be suc-
cessfully applied to the electrophilic reaction
of the 4-(diphenylphosphoryl)-allenoates 2a–d
which afforded the (3E)-4-(diphenylphosphoryl)alk-
3-enoates 4 highly regio- and stereoselectively, indi-
cating an addition reaction of electrophilic reagent
to the C2 C3-double bond of the allenic system
highly chemoselectively.
Thus, on the basis of the literature data [3–6, 8]
and our previous results [16], a rationale for this
reaction is depicted in Scheme 5. The initial act is
the attack of the electrophile (Cl+, Br+, S+, or Se+)
on the most nucleophilic atom of the allenic sys-
tem of π bonds (C3) with the formation of the cyclic
onium (chloronium, bromonium, thiiranium, or se-
R
E
Path a
3
Me
MeO
O
R1
CO2R2
R
E
Y = OMe
P
O
R1
CO2R2
Nu
MeNu
Y2P
C
a)
O
Path c
c)
(3E)-5
E-Nu
Y = Ph
Nu
1, 2
A
R1
E
R1
E
Path b
R
R
4
OR2
only Y = MeO
(MeO)2P
O
R2
O
O
Y2P
R2Nu
O
Nu
Nu
O
B
D
SCHEME 5
Heteroatom Chemistry DOI 10.1002/hc

Competitive Electrophilic Cyclization and Addition Reactions of 4-Phosphorylated Allenecarboxylates 65
R1
studies on the synthetic applications of this reac-
tion and the physiological activity of selected cyclic
and acyclic products are now under investigation in
our laboratory. Furthermore, a continuation of these
studies toward the synthesis and electrophilic cy-
clization reactions of other bifunctionalized allenes
is currently in progress in our laboratory.
R
E
E
R
Ph
Ph
R1
CO2R2
OR2
P
Ph
Ph
O
O
P
Nu
O
Nu
C1
B1
SCHEME 6
favorable from an energetic point of view. If the
phosphine oxide group takes place as an internal
nucleophile in the cyclization, the prepared cyclic
compounds should be phosphonium salts [9–11] C1
(Scheme 6), since in this case the stabilization by
the elimination of phenyl halide (second stage of
an Arbuzov-type rearrangement) and formation of
stable products with tetracoordinated phosphorus
is impossible. Moreover, the reason for the absence
of as the cyclic products as well as the adducts on
the C3 C4-double bond of the allenoate system ob-
viously consists of the fact that the corresponding
onium ions B1 (Scheme 6) is not formed in the reac-
tion of the 4-(diphenylphosphoryl)-allenoates 2a–d
with electrophiles.
The above-mentioned explanation should be cor-
roborated or refuted from the results on the study of
the reactions of other four-functionalized allenecar-
boxylates with electrophilic reagents and specially
their stereochemistry. Further work in this area is
being focused on exploiting and extending the syn-
thetic utility of the 1,3-bifunctionalized allenes for
the preparation of different heterocyclic systems us-
ing the electrophilic cyclization methodology.
EXPERIMENTAL
General
All new synthesized compounds were purified by col-
umn chromatography and characterized on the basis
of NMR, IR, and microanalytical data. NMR spectra
were recorded on DRX Brucker Avance-250 (Bruker
BioSpin, Karlsruhe, Germany) (1H at 250.1 MHz,
13C at 62.9 MHz, 31P at 101.2 MHz) and Brucker
Avance II+600 (Bruker BioSpin GmbH, Karlsruhe,
Germany) (1H at 600.1 MHz, 13C at 150.9 MHz, 31P
at 242.9 MHz) spectrometers for solutions in CDCl3.
Chemical shifts are in parts per million downfield
from internal TMS. J values are given in hertz.
IR spectra were recorded with an FT-IRAfinity-
1 Shimadzu spectrophotometer (Shimadzu, Tokyo,
Japan). Elemental analyses were carried out by the
Microanalytical Service Laboratory of Faculty of
Chemistry and Pharmacy, University of Sofia, Sofia,
Bulgaria, using Vario EL3 CHNS(O) (Elementar
Analysensysteme, Hanau, Germany). Column chro-
matography was performed on Kieselgel F25460 (70–
230 mesh ASTM, 0.063–0.200 nm; Merck). The melt-
ing points were measured in open capillary tubes and
are uncorrected. The solvents were purified by stan-
dard methods. Reactions were carried out in oven-
dried glassware under an argon atmosphere and ex-
clusion of moisture. All compounds were checked
for purity on TLC plates Kieselgel F25460 (Merck).
CONCLUSIONS
In conclusion, we have developed a simple and
convenient protocol for the reaction of the 4-
phosphorylated allenecarboxylates with different
electrophilic reagents, which takes place with 5-
endo-trig cyclization or 2,3-addition reaction de-
pending on the substituents on the phosphoryl
group. Treatment of the 4-(dimethoxyphosphopyl)-
allenoates with electrophiles gives the mixture of 2,5-
dihydro-1,2-oxaphospholes and furan-2(5H)-ones as
a result of the competitive neighboring group par-
ticipation of phosphonate and carboxylate groups
in the cyclization. On the other hand, (3E)-4-
(diphenylphosphoryl)-alk-3-enoates were prepared
by the chemo-, regio, and stereoselective elec-
trophilic addition to the C2 C3-double bond in
the allene moiety. Owing to the easy availability
of starting materials, the convenient operation and
the usefulness of the 1,2-oxaphosphole and buteno-
lide products, the reaction may show its potential
use and will be useful in organic synthesis. Further
Starting Materials
Benzenesulfanyl chloride was prepared from
diphenyl disulfide and sulfuryl chloride in
dichloromethane and distilled in vacuo (bp
80–81◦C/20 mmHg) before used [18]. Diphenyl
disulfide, sulfuryl chloride, and benzeneselanyl
chloride were commercially available and used
without purification.
General Procedure for the Reactions of the
4-Phosphorylated Allenecarboxylates 1 and 2
with Electrophilic Reagents
To a solution of 4-phosphorylated-2,3-alkadienoates
1 or 2 (3 mmol) in dry dichloromethane (10 mL) at
Heteroatom Chemistry DOI 10.1002/hc

66 Ivanov, Parushev, and Christov
–20◦C, a solution of electrophilic reagent (sulfuryl
chloride, bromine, benzenesulfanyl chloride, ben-
zeneselanyl chloride) (3.6 mmol) was added drop-
wise with stirring in the same solvent (10 mL). The
reaction mixture was stirred at the same tempera-
ture for several hours (see Tables 2 and 3) and 1 h at
room temperature. The solvent was removed using
a rotatory evaporator, and the residue was purified
by column chromatography on silica gel (Kieselgel
Merck 60 F254) with ethyl acetate/hexane. The pure
products 3 and 4 had the following properties.
45%). Eluent for TLC: ethyl acetate-hexane = 1:1,
Rf 0.79; IR (neat, cm−1): 1014 (C
P), 1260
O
(P O), 1441, 1486 (Ph), 1591 (C C), 1721 (C O).
1H NMR (CDCl3, 600.1 MHz, δ): 0.99 (t, J 7.4 Hz,
3H, Me-(CH2)2), 1.69 (m, 2H, Me-CH2-CH2), 2.43
(m, 2H, Me-CH2-CH2), 3.87 (d, J 11.4 Hz, 3H, MeO),
3.89 (s, 3H, MeO-C(O)), 7.39–7.53 (m, 5H, Ph). 13C
NMR (CDCl3, 150.9 MHz, δ): 13.9 (d, J 4.3 Hz, CH3),
20.7 (d, J 2.2 Hz, CH2), 29.9 (d, J 9.9 Hz, CH2), 53.6
(d, J 7.4 Hz, CH3), 54.1 (CH3), 88.8 (d, J 5.1 Hz, C),
126.8–134.8 (Ph), 131.4 (d, J 152.2 Hz, C), 134.1 (d, J
50.3 Hz, C), 167.2 (d, J 2.6 Hz, C). 31P NMR (CDCl3,
242.9 MHz, δ): 30.1. C15H18BrO5P (389.18). Calcd:
C 46.29, H 4.66; found: C 46.21, H 4.60.
Ethyl 4-chloro-2-methoxy-5-methyl-2-oxo-3-propyl-
2,5-dihydro-1,2-oxaphosphole-5-carboxylate (3aa).
Light orange oil, yield: 0.45 g (1.50 mmol, 50%).
Eluent for TLC: ethyl acetate-hexane = 1:1, Rf
Methyl
4-benzeneselanyl-2-methoxy-2-oxo-5-
phenyl-3-propyl-2,5-dihydro-1,2-oxaphosphole-5-car-
boxylate (3bd). Yellow oil, yield: 0.67 g (1.44 mmol,
48%). Eluent for TLC: ethyl acetate-hexane = 1:1,
0.80; IR (neat, cm−1): 1013 (C
O P), 1258 (P O),
1434, 1492 (Ph), 1589 (C C), 1718 (C O). 1H
NMR (CDCl3, 600.1 MHz, δ): 0.84 (t, J 7.4 Hz, 3H,
Me-(CH2)2), 1.29 (t, J 7.0 Hz, 3H, Me-CH2O), 1.57
(m, 2H, Me-CH2-CH2), 1.78 (s, 3H, Me), 2.11 (m,
2H, Me-CH2-CH2), 3.66 (d, J 11.5 Hz, 3H, MeO),
4.16 (m, 2H, Me-CH2O). 13C NMR (CDCl3, 150.9
MHz, δ): 14.2 (s, CH3), 14.9 (d, J 5.0 Hz, CH3), 20.5
(d, J 7.8 Hz, CH2), 22.1 (d, J 7.4 Hz, CH3), 30.8 (d,
J 5.6 Hz, CH2), 50.9 (d, J 7.0 Hz, CH3), 63.8 (CH2),
90.4 (d, J 8.9 Hz, C), 130.6 (d, J 98.4 Hz, C), 154.0
(d, J 39.3 Hz, C), 173.7 (d, J 2.8 Hz, C). 31P NMR
(CDCl3, 242.9 MHz, δ): 29.8. C11H18ClO5P (296.68).
Calcd: C 44.53, H 6.12; found: C 44.46, H 6.06.
Rf 0.75; IR (neat, cm−1): 1013 (C
O P), 1261
(P O), 1443, 1493 (Ph), 1588 (C C), 1720 (C O).
1H NMR (CDCl3, 600.1 MHz, δ): 0.74 (t, J 7.3 Hz,
3H, Me-(CH2)2), 1.36 (m, 2H, Me-CH2-CH2), 2.18
(m, 2H, Me-CH2-CH2), 3.83 (d, J 11.8 Hz, 3H, MeO),
3.88 (s, 3H, MeO-C(O)), 6.96–7.66 (m, 10H, 2Ph).
13C NMR (CDCl3, 150.9 MHz, δ): 14.1 (CH3), 20.3
(d, J 2.6 Hz, CH2), 30.5 (d, J 11.7 Hz, CH2), 53.5
(CH3), 53.8 (d, J 6.9 Hz, CH3), 90.3 (d, J 9.7 Hz, C),
126.7–135.9 (2Ph), 134.9 (d, J 145.4 Hz, C), 148.5
(d, J 26.5 Hz, C), 168.7 (d, J 2.9 Hz, C). 31P NMR
(CDCl3, 242.9 MHz, δ): 38.5. C21H23O5PSe (465.34).
Calcd: C 54.20, H 4.98; found: C 54.28, H 4.92.
Ethyl 4-benzeneselanyl-2-methoxy-5-methyl-2-oxo-
3-propyl-2,5-dihydro-1,2-oxaphosphole-5-carboxylate
(3ad). Light orange oil, yield: 0.58 g (1.38 mmol,
46%). Eluent for TLC: ethyl acetate-hexane = 1:1,
Ethyl 4-bromo-3-butyl-2-methoxy-5-methyl-2-oxo-
2,5-dihydro-1,2-oxaphosphole-5-carboxylate (3cb).
Light yellow oil, yield: 0.54 g (1.53 mmol, 51%).
Eluent for TLC: ethyl acetate-hexane = 1:1, Rf
Rf 0.79; IR (neat, cm−1): 1012 (C
O P), 1259
(P O), 1436, 1483 (Ph), 1585 (C C), 1719 (C O).
1H NMR (CDCl3, 600.1 MHz, δ): 0.85 (t, J 7.3 Hz,
3H, Me-(CH2)2), 1.22 (t, J 7.2 Hz, 3H, Me-CH2O),
1.50 (m, 2H, Me-CH2-CH2), 1.77 (s, 3H, Me), 2.32
(m, 2H, Me-CH2-CH2), 3.85 (d, J 11.6 Hz, 3H, MeO),
4.05 (m, 2H, Me-CH2O), 7.28–7.49 (m, 5H, Ph). 13C
NMR (CDCl3, 150.9 MHz, δ): 13.9 (s, CH3), 14.0
(d, J 4.5 Hz, CH3), 19.9 (d, J 7.7 Hz, CH2), 20.9 (d,
J 7.1 Hz, CH3), 30.5 (d, J 5.4 Hz, CH2), 53.9 (d,
J 6.9 Hz, CH3), 62.4 (CH2), 87.6 (d, J 8.7 Hz, C),
128.4–139.9 (Ph), 131.8 (d, J 106.5 Hz, C), 146.6 (d, J
29.2 Hz, C), 168.2 (d, J 2.9 Hz, C). 31P NMR (CDCl3,
242.9 MHz, δ): 34.4. C17H23O5PSe (417.30). Calcd: C
48.93, H 5.56; found: C 49.02, H 5.52.
0.77; IR (neat, cm−1): 1020 (C
O P), 1263 (P O),
1439, 1491 (Ph), 1584 (C C), 1720 (C O). 1H
NMR (CDCl3, 600.1 MHz, δ): 0.87 (t, J 7.2 Hz, 3H,
Me-(CH2)3), 1.28 (t, J 7.1 Hz, 3H, Me-CH2-O), 1.32
(m, 4H, Me-(CH2)2-CH2), 1.91 (s, 3H, Me), 2.18 (m,
2H, Me-(CH2)2CH2), 3.76 (d, J 11.4 Hz, 3H, MeO),
4.21 (m, 2H, Me-CH2-O). 13C NMR (CDCl3, 150.9
MHz, δ): 13.5 (CH3), 13.9 (CH3), 21.1 (d, J 4.2 Hz,
CH2), 22.0 (d, J 7.1 Hz, CH3), 29.1 (d, J 7.1 Hz, CH2),
29.6 (d, J 5.2 Hz, CH2), 52.3 (d, J 7.1 Hz, CH3), 62.4
(CH2), 87.6 (d, J 11.1 Hz, C), 128.3 (d, J 125.4 Hz, C),
135.2 (d, J 30.1 Hz, C), 174.1 (C). 31P NMR (CDCl3,
242.9 MHz, δ): 29.6. C12H20BrO5P (355.16). Calcd:
C 40.58, H 5.68; found: C 40.63, H 5.62.
Methyl
4-bromo-2-methoxy-2-oxo-5-phenyl-3-
Ethyl
4-benzeneselanyl-3-butyl-2-methoxy-5-
propyl-2,5-dihydro-1,2-oxaphosphole-5-carboxylate
methyl-2-oxo-2,5-dihydro-1,2-oxaphosphole-5-carbo-
(3bb). Light yellow oil, yield: 0.53 g (1.35 mmol,
xylate (3cd). Yellow oil, yield: 0.60 g (1.38 mmol,
Heteroatom Chemistry DOI 10.1002/hc

Competitive Electrophilic Cyclization and Addition Reactions of 4-Phosphorylated Allenecarboxylates 67
46%). Eluent for TLC: ethyl acetate-hexane
1:1, Rf 0.73; IR (neat, cm−1): 1020 (C
=
(P O), 1433, 1491 (Ph), 1594 (C C), 1722 (C O).
1H NMR (CDCl3, 600.1 MHz, δ): 1.39 (t, J 7.1 Hz,
3H, Me-CH2-O), 3.75 (d, J 12.2 Hz, 3H, MeO), 4.43
(m, 2H, Me-CH2-O), 6.51–7.77 (m, 15H, 3Ph). 13C
NMR (CDCl3, 150.9 MHz, δ): 14.2 (CH3), 54.3 (d,
J 6.9 Hz, CH3), 63.1 (CH2), 89.9 (d, J 7.7 Hz, C),
126.1–131.6 (3Ph), 131.4 (d, J 114.3 Hz, C), 152.2
(d, J 29.3 Hz, C), 167.8 (d, J 3.1 Hz, C). 31P NMR
(CDCl3, 242.9 MHz, δ): 36.4. C25H23O5PS (466.49).
Calcd: C 64.37, H 4.97; found: C 64.44, H 5.02.
O
P),
1264 (P O), 1441, 1485 (Ph), 1590 (C C), 1722
(C O). 1H NMR (CDCl3, 600.1 MHz, δ): 0.84 (t,
J 7.3 Hz, 3H, Me-(CH2)3), 1.23 (t, J 7.1 Hz, 3H,
Me-CH2-O), 1.41 (m, 2H, Me-CH2-(CH2)2), 1.49 (m,
2H, Me-CH2-CH2-CH2), 1.72 (s, 3H, Me), 2.34 (m,
2H, Me-(CH2)2-CH2), 3.84 (d, J 11.7 Hz, 3H, MeO),
4.07 (m, 2H, Me-CH2-O), 7.27–7.45 (m, 5H, Ph).
13C NMR (CDCl3, 150.9 MHz, δ): 13.7 (CH3), 13.9
(CH3), 22.5 (CH2), 22.7 (d, J 8.1 Hz, CH3), 28.4 (d,
J 6.8 Hz, CH2), 29.5 (d, J 5.0 Hz, CH2), 53.7 (d, J
7.0 Hz, CH3), 62.6 (CH2), 87.6 (d, J 12.3 Hz, C),
128.1–133.0 (Ph), 135.8 (d, J 119.4 Hz, C), 146.5 (d, J
27.6 Hz, C), 168.2 (C). 31P NMR (CDCl3, 242.9 MHz,
δ): 36.5. C18H25O5PSe (431.32). Calcd: C 50.12, H
5.84; found: C 50.20, H 5.77.
Ethyl
4-benzeneselanyl-2-methoxy-2-oxo-3,5-
diphenyl-2,5-dihydro-1,2-oxaphosphole-5-carboxylate
(3dd). Colourless oil, yield: 0.72 g (1.41 mmol,
47%). Eluent for TLC: ethyl acetate-hexane = 1:1,
Rf 0.75; IR (neat, cm−1): 1021 (C
O P), 1262
(P O), 1438, 1495 (Ph), 1589 (C C), 1723 (C O).
1H NMR (CDCl3, 600.1 MHz, δ): 1.41 (t, J 7.2 Hz,
3H, Me-CH2-O), 3.71 (d, J 12.1 Hz, 3H, MeO), 4.46
(m, 2H, Me-CH2-O), 6.59–7.72 (m, 15H, 3Ph). 13C
NMR (CDCl3, 150.9 MHz, δ): 14.5 (CH3), 54.5 (d, J
6.8 Hz, CH3), 63.1 (CH2), 126.5–133.7 (3Ph), 126.7
(d, J 105.6 Hz, C), 136.1 (d, J 7.4 Hz, C), 151.0 (d, J
25.6 Hz, C), 168.0 (d, J 2.6 Hz, C). 31P NMR (CDCl3,
242.9 MHz, δ): 35.3. C25H23O5PSe (513.38). Calcd: C
58.49, H 4.52; found: C 58.40, H 4.59.
Ethyl 4-chloro-2-methoxy-2-oxo-3,5-diphenyl-2,5-
dihydro-1,2-oxaphosphole-5-carboxylate
(3da).
Light yellow oil, yield: 0.58 g (1.47 mmol, 49%).
Eluent for TLC: ethyl acetate-hexane = 1:1, Rf
0.76; IR (neat, cm−1): 1015 (C
O P), 1259 (P O),
1438, 1485 (Ph), 1586 (C C), 1724 (C O). 1H
NMR (CDCl3, 250.1 MHz, δ): 1.39 (t, J 7.1 Hz, 3H,
Me-CH2-O), 3.86 (d, J 12.0 Hz, 3H, MeO), 4.34–4.45
(m, 2H, Me-CH2-O), 7.41–7.83 (m, 10H, 2Ph). 13C
NMR (CDCl3, 62.9 MHz, δ): 14.0 (CH3), 54.6 (d, J
6.9 Hz, CH3), 63.3 (CH2), 78.8 (d, J 13.9 Hz, C),
125.3 (d, J 122.4 Hz, C), 127.2–129.9 (2Ph), 146.5
(d, J 30.5 Hz, C), 166.9 (C). 31P NMR (CDCl3, 101.2
MHz, δ): 31.9. C19H18ClO5P (392.77). Calcd: C 58.10,
H 4.62; found: C 58.03, H 4.70.
Dimethyl (3-chloro-4-methyl-5-oxo-2-propyl-2,5-
dihydrofuran-2-yl)phosphonate (4aa). Light yellow
oil, yield: 0.24 g (0.84 mmol, 28%). Eluent for TLC:
ethyl acetate-hexane = 1:1, Rf 0.46; IR (neat, cm−1):
1124 (C–O–C), 1246 (P O), 1437, 1494 (Ph), 1619
1
(C C), 1751 (C O). H NMR (CDCl3, 600.1 MHz,
δ): 1.18 (t, J 7.1 Hz, 3H, Me-(CH2)2), 1.72 (m, 2H,
Me-CH2-CH2), 2.17 (s, 3H, Me), 2.32 (m, 2H, Me-
CH2-CH2), 3.82 (d, J 10.3 Hz, 6H, 2MeO). 13C NMR
(CDCl3, 150.9 MHz, δ): 15.2 (d, J 4.9 Hz, CH3), 15.5
(d, J 4.7 Hz, CH3), 19.4 (d, J 7.7 Hz, CH2), 35.3 (d,
J 5.7 Hz, CH2), 52.8 (d, J 14.7 Hz, CH3), 99.9 (d,
J 126.4 Hz, C), 131.8 (d, J 8.0 Hz, C), 159.4 (d, J
40.1 Hz, C), 171.8 (d, J 7.4 Hz, C). 31P NMR (CDCl3,
242.9 MHz, δ): 17.8. C10H16ClO5P (282.66). Calcd: C
42.49, H 5.71; found: C 42.58, H 5.66.
Ethyl 4-bromo-2-methoxy-2-oxo-3,5-diphenyl-2,5-
dihydro-1,2-oxaphosphole-5-carboxylate
(3db).
Light yellow oil, yield: 0.66 g (1.5 mmol, 50%).
Eluent for TLC: ethyl acetate-hexane = 1:1, Rf
0.79; IR (neat, cm−1): 1012 (C
O P), 1261 (P O),
1439, 1490 (Ph), 1592 (C C), 1724 (C O). 1H
NMR (CDCl3, 250.1 MHz, δ): 1.38 (t, J 7.0 Hz, 3H,
Me-CH2-O), 3.85 (d, J 11.8 Hz, 3H, MeO), 4.39–4.49
(m, 2H, Me-CH2-O), 7.42–7.83 (m, 10H, 2Ph). 13C
NMR (CDCl3, 62.9 MHz, δ): 13.9 (CH3), 54.5 (d, J
6.8 Hz, CH3), 63.2 (CH2), 82.8 (d, J 14.0 Hz, C),
127.1–129.7 (2Ph), 127.3 (d, J 32.4 Hz, C), 128.6
(d, J 117.1 Hz, C), 166.4 (C). 31P NMR (CDCl3,
101.2 MHz, δ): 32.3. C19H18BrO5P (437.22). Calcd:
C 52.19, H 4.15; found: C 52.23, H 4.22.
Dimethyl
(3-benzeneselanyl-4-methyl-5-oxo-2-
(4ad).
propyl-2,5-dihydrofuran-2-yl)phosphonate
Yellow oil, yield: 0.34 g (0.84 mmol, 28%). Eluent
for TLC: ethyl acetate-hexane = 1:1, Rf 0.44; IR
(neat, cm−1): 1123 (C–O–C), 1245 (P O), 1441, 1477
(Ph), 1622 (C C), 1748 (C O). 1H NMR (CDCl3,
600.1 MHz, δ): 0.96 (t, J 7.3 Hz, 3H, Me-(CH2)2), 1.58
(m, 2H, Me-CH2-CH2), 2.12 (s, 3H, Me), 2.38 (m,
2H, Me-CH2-CH2), 3.84 (d, J 10.2 Hz, 6H, 2MeO),
7.38–7.57 (m, 5H, Ph). 13C NMR (CDCl3, 150.9 MHz,
δ): 13.0 (d, J 5.2 Hz, CH3), 14.2 (d, J 4.7 Hz, CH3),
Ethyl
4-benzenesulfanyl-2-methoxy-2-oxo-3,5-
diphenyl-2,5-dihydro-1,2-oxaphosphole-5-carboxylate
(3dc). Light orange oil, yield: 0.63 g (1.35 mmol,
45%). Eluent for TLC: ethyl acetate-hexane = 1:1,
Rf 0.77; IR (neat, cm−1): 1017 (C
O P), 1257
Heteroatom Chemistry DOI 10.1002/hc

68 Ivanov, Parushev, and Christov
(d, J 7.8 Hz, C). 31P NMR (CDCl3, 242.9 MHz, δ):
18.8. C11H18BrO5P (341.14). Calcd: C 38.73, H 5.32;
found: C 38.82, H 5.26.
15.8 (d, J 7.4 Hz, CH2), 36.0 (d, J 5.3 Hz, CH2),
52.8 (d, J 15.2 Hz, CH3), 102.4 (d, J 127.3 Hz, C),
128.0 (d, J 7.8 Hz, C), 128.6–138.4 (Ph), 174.6 (d, J
7.6 Hz, C), 177.1 (d, J 50.8 Hz, C). 31P NMR (CDCl3,
242.9 MHz, δ): 20.2. C16H21O5PSe (403.27). Calcd: C
47.65, H 5.25; found: C 47.58, H 5.20.
Dimethyl
(3-benzeneselanyl-2-butyl-4-methyl-
(4cd).
5-oxo-2,5-dihydrofuran-2-yl)phosphonate
Pale yellow oil, yield: 0.36 g (0.87 mmol, 29%).
Eluent for TLC: ethyl acetate-hexane = 1:1, Rf
0.49; IR (neat, cm−1): 1125 (C–O–C), 1242 (P O),
1436, 1490 (Ph), 1619 (C C), 1748 (C O). 1H
NMR (CDCl3, 600.1 MHz, δ): 0.89 (t, J 7.3 Hz, 3H,
Me-(CH2)3), 1.46 (m, 2H, Me-CH2-(CH2)2), 1.51
(m, 2H, Me-CH2-CH2-CH2), 2.17 (s, 3H, Me), 2.49
(m, 2H, Me-(CH2)2-CH2), 3.85 (d, J 11.0 Hz, 6H,
2MeO), 7.38–7.51 (m, 5H, Ph). 13C NMR (CDCl3,
150.9 MHz, δ): 14.2 (CH3), 16.7 (CH3), 22.4 (d, J
4.7 Hz, CH2), 26.1 (d, J 7.2 Hz, CH3), 32.7 (d, J 6.0 Hz,
CH2), 53.9 (d, J 13.9 Hz, CH3), 100.4 (d, J 110.3 Hz,
C), 127.4 (d, J 7.7 Hz, C), 128.3–134.01 (Ph), 174.7
(d, J 7.6 Hz, C), 177.6 (d, J 51.2 Hz, C). 31P NMR
(CDCl3, 242.9 MHz, δ): 17.9. C17H23O5PSe (417.30).
Calcd: C 48.93, H 5.56; found: C 49.02, H 5.51.
Dimethyl (3-bromo-2-oxo-4-phenyl-2-propyl-2,5-
dihydrofuran-2-yl)phosphonate (4bb). Yellow oil,
yield: 0.33 g (0.84 mmol, 28%). Eluent for TLC: ethyl
acetate-hexane = 1:1, Rf 0.46; IR (neat, cm−1): 1122
(C–O–C), 1248 (P O), 1435, 1493 (Ph), 1616 (C C),
1
1752 (C O). H NMR (CDCl3, 600.1 MHz, δ): 1.09
(t, J 7.1 Hz, 3H, Me-(CH2)2), 1.64 (m, 2H, Me-CH2-
CH2), 2.26 (m, 2H, Me-CH2-CH2), 3.82 (d, J 10.3 Hz,
6H, 2MeO), 7.45–7.78 (m, 5H, Ph). 13C NMR (CDCl3,
150.9 MHz, δ): 15.9 (d, J 5.1 Hz, CH3), 17.8 (d, J
7.2 Hz, CH2), 35.2 (d, J 5.4 Hz, CH2), 53.1 (d, J
15.0 Hz, CH3), 101.7 (d, J 125.8 Hz, C), 126.8–129.0
(Ph), 141.5 (d, J 51.4 Hz, C), 146.7 (d, J 7.3 Hz, C),
170.5 (d, J 7.8 Hz, C). 31P NMR (CDCl3, 242.9 MHz,
δ): 18.2. C15H18BrO5P (389.18). Calcd: C 46.29, H
4.66; found: C 46.37, H 4.72.
Dimethyl (3-chloro-5-oxo-2,4-diphenyl-2,5-dihy-
drofuran-2-yl)phosphonate (4da). Colorless oil,
yield: 0.31 g (0.81 mmol, 27%). Eluent for TLC: ethyl
acetate-hexane = 1:1, Rf 0.47; IR (neat, cm−1): 1119
(C–O–C), 1243 (P O), 1438, 1487 (Ph), 1621 (C C),
Dimethyl
(3-benzeneselanyl-5-oxo-4-phenyl-2-
(4bd).
propyl-2,5-dihydrofuran-2-yl)phosphonate
Light orange oil, yield: 0.40 g (0.87 mmol, 29%).
Eluent for TLC: ethyl acetate-hexane = 1:1, Rf
0.41; IR (neat, cm−1): 1121 (C–O–C), 1246 (P O),
1440, 1488 (Ph), 1622 (C C), 1748 (C O). 1H
NMR (CDCl3, 600.1 MHz, δ): 1.14 (t, J 7.4 Hz, 3H,
Me-(CH2)2), 1.61 (m, 2H, Me-CH2-CH2), 2.35 (m,
2H, Me-CH2-CH2), 3.83 (d, J 10.7 Hz, 6H, 2MeO),
7.33–7.96 (m, 10H, 2Ph). 13C NMR (CDCl3, 150.9
MHz, δ): 14.9 (CH3), 16.8 (d, J 7.4 Hz, CH2), 34.7 (d,
J 5.6 Hz, CH2), 52.4 (CH3), 103.6 (d, J 127.0 Hz, C),
127.4–138.2 (2Ph), 137.1 (d, J 7.7 Hz, C), 170.4 (d, J
7.9 Hz, C), 177.4 (d, J 52.8 Hz, C). 31P NMR (CDCl3,
242.9 MHz, δ): 19.8. C21H23O5PSe (465.34). Calcd: C
54.20, H 4.98; found: C 54.13, H 5.02.
1
1749 (C O). H NMR (CDCl3, 250.1 MHz, δ): 3.71
(d, J 11.2 Hz, 6H, 2MeO), 7.41–7.97 (m, 10H, 2Ph).
13C NMR (CDCl3, 62.9 MHz, δ): 53.4 (d, J 15.2 Hz,
CH3), 95.3 (d, J 105.1 Hz, C), 122.4–131.9 (2Ph),
129.7 (d, J 8.0 Hz, C), 147.5 (d, J 45.2 Hz, C), 171.0
(d, J 7.4 Hz, C). 31P NMR (CDCl3, 101.2 MHz, δ):
16.5. C18H16ClO5P (378.74). Calcd: C 57.08, H 4.26;
found: C 57.13, H 4.22.
Dimethyl (3-bromo-5-oxo-2,4-diphenyl-2,5-dihy-
drofuran-2-yl)phosphonate (4db). Yellow oil, yield:
0.36 g (0.84 mmol, 28%). Eluent for TLC: ethyl
acetate-hexane = 1:1, Rf 0.45; IR (neat, cm−1): 1121
(C–O–C), 1245 (P O), 1443, 1492 (Ph), 1620 (C C),
Dimethyl (3-bromo-2-butyl-4-methyl-5-oxo-2,5-
dihydrofuran-2-yl)phosphonate (4cb). Yellow oil,
yield: 0.29 g (0.84 mmol, 28%). Eluent for TLC:
ethyl acetate-hexane = 1:1, Rf 0.47; IR (neat, cm−1):
1118 (C–O–C), 1239 (P O), 1434, 1487 (Ph), 1621
(C C), 1751 (C O). ). 1H NMR (CDCl3, 600.1 MHz,
δ): 0.90 (t, J 7.2 Hz, 3H, Me-(CH2)3), 1.49 (m, 2H,
Me-CH2-(CH2)2), 1.57 (m, 2H, Me-CH2-CH2-CH2),
2.29 (s, 3H, Me), 2.48 (m, 2H, Me-(CH2)2-CH2), 3.83
(d, J 10.8 Hz, 6H, 2MeO). 13C NMR (CDCl3, 150.9
MHz, δ): 14.0 (CH3), 16.2 (CH3), 21.9 (d, J 5.0 Hz,
CH2), 27.0 (d, J 7.4 Hz, CH2), 33.1 (d, J 6.2 Hz, CH2),
54.3 (d, J 14.1 Hz, CH3), 98.4 (d, J 107.4 Hz, C),
130.2 (d, J 7.8 Hz, C), 146.8 (d, J 50.7 Hz, C), 176.0
1
1752 (C O). H NMR (CDCl3, 250.1 MHz, δ): 3.80
(d, J 10.6 Hz, 6H, 2MeO), 7.45–7.98 (m, 10H, 2Ph).
13C NMR (CDCl3, 62.9 MHz, δ): 55.2 (d, J 14.0 Hz,
CH3), 91.4 (d, J 102.4 Hz, C), 126.4–129.8 (2Ph),
132.0 (d, J 7.7 Hz, C), 147.1 (d, J 49.4 Hz, C), 170.9
(d, J 7.1 Hz, C). 31P NMR (CDCl3, 101.2 MHz, δ):
14.3. C18H16BrO5P (423.19). Calcd: C 51.09, H 3.81;
found: C 51.15, H 3.72.
Dimethyl (3-benzenesulfanyl-5-oxo-2,4-diphenyl-
2,5-dihydrofuran-2-yl)phosphonate (4dc). Orange
oil, yield: 0.38 g (0.84 mmol, 28%). Eluent for TLC:
Heteroatom Chemistry DOI 10.1002/hc

Competitive Electrophilic Cyclization and Addition Reactions of 4-Phosphorylated Allenecarboxylates 69
CH2), 68.4 (CH2), 81.6 (d, J 6.1 Hz, C), 128.9–139.5
ethyl acetate-hexane = 1:1, Rf 0.45; IR (neat, cm−1):
(3Ph), 129.7 (d, J 92.2 Hz, C), 147.0 (d, J 34.8 Hz, C),
178.8 (d, J 4.6 Hz, C). 31P NMR (CDCl3, 242.9 MHz,
δ): 26.3. C29H32ClO3PSe (573.95). Calcd: C 60.69, H
5.62; found: C 60.75, H 5.66.
1114 (C–O–C), 1241 (P O), 1435, 1490 (Ph), 1617
(C C), 1750 (C O). 1H NMR (CDCl3, 600.1 MHz, δ):
3.77 (d, J 10.9 Hz, 6H, 2MeO), 6.62–7.98 (m, 15H,
3Ph). 13C NMR (CDCl3, 150.9 MHz, δ): 54.5 (d, J
11.4 Hz, CH3), 92.4 (d, J 110.5 Hz, C), 127.0–136.1
(3Ph), 128.7 (d, J 7.1 Hz, C), 168.1 (d, J 50.5 Hz, C),
170.6 (d, J 7.1 Hz, C). 31P NMR (CDCl3, 242.9 MHz,
δ): 16.5. C24H21O5PS (452.46). Calcd: C 63.71, H 4.68;
found: C 63.63, H 4.74.
Methyl (3E)-2,3-dibromo-4-(diphenylphosphor-
yl)-2-phenyloct-3-enoate (5bb). Colorless oil, yield:
1.29 g (2.19 mmol, 73%). Eluent for TLC: ethyl
acetate-hexane = 1:1, Rf 0.79; IR (neat, cm−1): 1134
(P O), 1440, 1488 (Ph), 1591 (C C), 1724 (C O).
1H NMR (CDCl3, 600.1 MHz, δ): 0.75 (t, J 7.0 Hz,
3H, Me-(CH2)3), 1.25 (m, 4H, Me-(CH2)2-CH2),
2.17 (m, 2H, Me-(CH2)2-CH2), 3.73 (s, 3H, MeO),
7.42–8.08 (m, 15H, 3Ph). 13C NMR (CDCl3, 150.9
MHz, δ): 13.4 (CH3), 22.6 (CH2), 28.1 (CH2), 38.2
(d, J 11.7 Hz, CH2), 52.9 (CH3), 84.4 (d, J 6.9 Hz,
C), 127.4–142.7 (3Ph), 133.4 (d, J 125.4 Hz, C),
137.0 (d, J 29.3 Hz, C), 169.1 (d, J 4.2 Hz, C). 31P
NMR (CDCl3, 242.9 MHz, δ): 27.6. C27H27Br2O3P
(590.28). Calcd: C 54.94, H 4.61; found: C 55.02,
H 4.55.
Dimethyl (3-benzeneselanyl-5-oxo-2,4-diphenyl-
2,5-dihydrofuran-2-yl)phosphonate (4dd). Yellow
oil, yield: 0.40 g (0.81 mmol, 27%). Eluent for TLC:
ethyl acetate-hexane = 1:1, Rf 0.48; IR (neat, cm−1):
1116 (C–O–C), 1244 (P O), 1436, 1482 (Ph), 1616
1
(C C), 1748 (C O). H NMR (CDCl3, 600.1 MHz,
δ): 3.75 (d, J 10.7 Hz, 6H, 2MeO), 6.79–7.93 (m,
15H, 3Ph). 13C NMR (CDCl3, 150.9 MHz, δ): 55.3 (d,
J 12.4 Hz, CH3), 89.4 (d, J 105.0 Hz, C), 126.1–134.4
(3Ph), 131.0 (d, J 6.9 Hz, C), 157.6 (d, J 7.4 Hz, C),
170.5 (d, J 51.5 Hz, C). 31P NMR (CDCl3, 242.9 MHz,
δ): 16.5. C24H21O5PSe (499.35). Calcd: C 57.73, H
4.24; found: C 57.81, H 4.19.
Methyl
(3E)-3-benzeneselanyl-2-chloro-4-(di-
(5bd).
phenylphosphoryl)-2-phenyl-oct-3-enoate
Yellow oil, yield: 1.21 g (1.95 mmol, 65%). Eluent
for TLC: ethyl acetate-hexane = 1:1, Rf 0.74; IR
(neat, cm−1): 1130 (P O), 1436, 1494 (Ph), 1585
Ethyl (3E)-2,3-dibromo-4-(diphenylphosphoryl)-
2-methyl-oct-3-enoate (5ab). Light orange oil, yield:
1.14 g (2.10 mmol, 70%). Eluent for TLC: ethyl
acetate-hexane = 1:1, Rf 0.73; IR (neat, cm−1): 1126
(P O), 1436, 1493 (Ph), 1593 (C C), 1719 (C O). 1H
NMR (CDCl3, 600.1 MHz, δ): 0.82 (t, J 7.0 Hz, 3H,
Me-(CH2)3), 1.21 (t, J 7.1 Hz, 3H, Me-CH2O), 1.27 (m,
4H, Me-(CH2)2-CH2), 2.16 (m, 2H, Me-(CH2)2-CH2),
2.38 (s, 3H, Me), 4.13 (m, 2H, Me-CH2O), 7.54–8.05
(m, 10H, 2Ph). 13C NMR (CDCl3, 150.9 MHz, δ): 13.7
(CH3), 14.3 (CH3), 21.7 (CH2), 30.5 (CH2), 33.1 (d, J
6.3 Hz, CH2), 35.3 (CH3), 52.8 (d, J 7.7 Hz, C), 80.0
(CH2), 129.3–135.6 (2Ph), 130.5 (d, J 126.8 Hz, C),
138.4 (d, J 30.4 Hz, C), 166.3 (d, J 4.1 Hz, C). 31P NMR
(CDCl3, 242.9 MHz, δ): 28.8. C23H27Br2O3P (542.24).
Calcd: C 50.95, H 5.02; found: C 51.04, H 4.97.
1
(C C), 1732 (C O). H NMR (CDCl3, 600.1 MHz,
δ): 0.79 (t, J 7.2 Hz, 3H, Me-(CH2)3), 1.18 (m, 2H,
Me-CH2-CH2-CH2), 1.27 (m, 2H, Me-CH2-(CH2)2),
2.32 (m, 2H, Me-(CH2)2-CH2), 3.76 (s, 3H, MeO),
7.26–7.75 (m, 20H, 4Ph). 13C NMR (CDCl3, 150.9
MHz, δ): 13.9 (CH3), 22.1 (CH2), 24.7 (CH2), 42.4 (d,
J 11.4 Hz, CH2), 52.4 (CH3), 92.1 (d, J 7.1 Hz, C),
125.5–139.7 (4Ph), 134.2 (d, J 112.8 Hz, C), 144.7 (d,
J 26.7 Hz, C), 169.4 (d, J 4.0 Hz, C). 31P NMR (CDCl3,
242.9 MHz, δ): 26.8. C33H32ClO3PSe (621.99). Calcd:
C 63.73, H 5.19; found: C 63.80, H 5.12.
Еthyl (3E)-2,3-dibromo-4-(diphenylphosphoryl)-
2-methyl-4-phenylbut-3-enoate (5cb). Yellow oil,
yield: 1.21 g (2.16 mmol, 72%). Eluent for TLC: ethyl
acetate-hexane = 1:1, Rf 0.78; IR (neat, cm−1): 1164
(P O), 1432, 1485 (Ph), 1587 (C C), 1719 (C O). 1H
NMR (CDCl3, 600.1 MHz, δ): 1.20 (t, J 7.1 Hz, 3H,
Me-CH2O), 2.39 (s, 3H, Me), 4.14 (m, 2H, Me-CH2O),
7.40–8.06 (m, 15H, 3Ph). 13C NMR (CDCl3, 150.9
MHz, δ): 14.0 (CH3), 35.1 (CH3), 55.6 (d, J 7.5 Hz, C),
61.3 (CH2), 129.1–135.7 (3Ph), 134.1 (d, J 128.4 Hz,
C), 139.8 (d, J 31.7 Hz, C), 167.2 (d, J 3.9 Hz, C).
31P NMR (CDCl3, 242.9 MHz, δ): 26.2. C25H23Br2O3P
(562.23). Calcd: C 53.41, H 4.12; found: C 53.50, H
4.05.
Ethyl (3E)-3-benzeneselanyl-2-chloro-4-(diphen-
ylphosphoryl)-2-methyl-oct-3-enoate (5ad). Orange
oil, yield: 1.10 g (1.92 mmol, 64%). Eluent for TLC:
ethyl acetate-hexane = 1:1, Rf 0.70; IR (neat, cm−1):
1117 (P O), 1435, 1490 (Ph), 1589 (C C), 1732
1
(C O). H NMR (CDCl3, 600.1 MHz, δ): 0.76 (t, J
7.4 Hz, 3H, Me-(CH2)3), 1.22 (m, 4H, Me-(CH2)2-
CH2), 1.26 (t, J 7.2 Hz, 3H, Me-CH2O), 1.95 (s, 3H,
Me), 2.28 (m, 2H, Me-(CH2)2-CH2), 4.15 (m, 2H, Me-
CH2O), 7.28–7.79 (m, 15H, 3Ph). 13C NMR (CDCl3,
150.9 MHz, δ): 14.3 (CH3), 14.8 (CH3), 23.6 (CH2),
28.0 (CH3), 29.7 (d, J 7.9 Hz, CH2), 37.6 (d, J 13.6 Hz,
Heteroatom Chemistry DOI 10.1002/hc

70 Ivanov, Parushev, and Christov
Еthyl (3E)-3-benzeneselanyl-2-chloro-4-(diphen-
ylphosphoryl)-2-methyl-4-phenyl-but-3-enoate (5cd).
Yellow oil, yield: 1.14 g (1.92 mmol, 64%). Eluent for
TLC: ethyl acetate-hexane = 1:1, Rf 0.73; IR (neat,
cm−1): 1161 (P O), 1439, 1477 (Ph), 1589 (C C),
δ): 24.8. C36H30ClO3PS (609.11). Calcd: C 70.99, H
4.96; found: C 71.05, H 4.91.
Еthyl (3E)-3-benzeneselanyl-2-chloro-4-(diphen-
ylphosphoryl)-2,4-diphenyl-but-3-enoate
(5dd).
1
1732 (C O). H NMR (CDCl3, 600.1 MHz, δ): 1.18
Light orange oil, yield: 1.24 g (1.89 mmol, 63%).
Eluent for TLC: ethyl acetate-hexane = 1:1, Rf 0.69;
IR (neat, cm−1): 1177 (P O), 1441, 1493 (Ph), 1599
(t, J 7.0 Hz, 3H, Me-CH2O), 1.97 (s, 3H, Me), 4.17
(m, 2H, Me-CH2O), 7.27–8.10 (m, 20H, 4Ph). 13C
NMR (CDCl3, 150.9 MHz, δ): 13.7 (CH3), 25.2 (CH3),
61.3 (CH2), 81.4 (d, J 7.3 Hz, C), 128.4–142.7 (4Ph),
131.9 (d, J 96.4 Hz, C), 154.0 (d, J 29.7 Hz, C),
180.4 (d, J 4.1 Hz, C). 31P NMR (CDCl3, 242.9 MHz,
δ): 27.2. C31H28ClO3PSe (593.94). Calcd: C 62.69, H
4.75; found: C 62.76, H 4.80.
1
(C C), 1725 (C O). H NMR (CDCl3, 600.1 MHz,
δ): 0.91 (t, J 7.1 Hz, 3H, Me-CH2O), 3.96 (m, 2H,
Me-CH2O), 6.97–7.75 (m, 25H, 5Ph). 13C NMR
(CDCl3, 150.9 MHz, δ): 13.5 (CH3), 61.8 (CH2),
70.5 (d, J 7.6 Hz, C), 125.4–138.7 (5Ph), 147.8 (d, J
122.4 Hz, C), 153.3 (d, J 32.0 Hz, C), 172.1 (C). 31P
NMR (CDCl3, 242.9 MHz, δ): 26.8. C36H30ClO3PSe
(656.01). Calcd: C 65.91, H 4.61; found: C 65.85, H
4.57.
Еthyl (3E)-2,3-dichloro-4-(diphenylphosphoryl)-
2,4-diphenylbut-3-enoate (5da). Colorless oil, yield:
1.11 g {2.07 mmol, 69%). Eluent for TLC: ethyl ac-
etate:hexane = 1:1, Rf 0.78; IR (neat, cm−1): 1136
(P O), 1439, 1483 (Ph), 1596 (C C), 1727 (C O).
1H NMR (CDCl3, 250.1 MHz, δ): 1.35 (t, J 7.0 Hz,
3H, Me-CH2O), 4.35 (m, 2H, Me-CH2O), 7.03–7.69
(m, 20H, 4Ph). 13C NMR (CDCl3, 62.9 MHz, δ): 14.1
(CH3), 62.3 (CH2), 65.0 (d, J 7.2 Hz, C), 127.5–
133.2 (4Ph), 137.1 (d, J 28.6 Hz, C), 140.1 (d, J
122.4 Hz, C), 171.2 (C). 31P NMR (CDCl3, 101.2 MHz,
δ): 24.3. C30H25Cl2O3P (535.40). Calcd: C 67.30, H
4.71; found: C 67.23, H 4.77.
REFERENCES
[1] (a) Patai, S. (Ed.): The Chemistry of Ketenes, Allenes
and Related Compounds; Wiley: New York, 1980; (b)
Landor, S. R. (Ed.): The Chemistry of the Allenes;
Academic Press: London, 1982, Vol. 1–3; (c) Pasto,
D. J. Tetrahedron 1984, 40, 2805–2827; (d) Schuster,
H. F.; Coppola, G. M. Allenes in Organic Synthe-
sis; Wiley: New York, 1988; (e) Zimmer, R. Syn-
thesis 1993, 165–178; (f) Elsevier, C. J. Methods
of Organic Chemistry (Houben-Weyl); Vol. E21a,
Helmchen, R. W.; Mulzer, J.; Schaumann, E., Eds.;
Thieme: Stuttgart, Germany, 1995; pp. 537–566; (g)
Krause, N.; Hashmi, A. S. K. (Eds.). Modern Allene
Chemistry; Wiley-VCH: Weinheim, Germany, 2004,
Vol. 1 and 2; (h) Brummond, K. M., DeForrest, J. E.
Synthesis 2007, 795–818.
Еthyl (3E)-2,3-dibromo-4-(diphenylphosphoryl)-
2,4-diphenylbut-3-enoate (5db). Orange oil, yield:
1.33 g ( 2.13 mmol, 71%). Eluent for TLC: ethyl
acetate-hexane = 1:1, Rf 0.76; IR (neat, cm−1): 1131
(P O), 1442, 1481 (Ph), 1598 (C C), 1731 (C O).
1H NMR (CDCl3, 250.1 MHz, δ): 1.25 (t, J 7.1 Hz,
3H, Me-CH2O), 4.30 (m, 2H, Me-CH2O), 7.06–7.99
(m, 20H, 4Ph). 13C NMR (CDCl3, 62.9 MHz, δ): 14.6
(CH3), 62.9 (CH2), 63.8 (d, J 7.4 Hz, C), 126.3–
132.3 (4Ph), 134.0 (d, J 30.0 Hz, C), 143.9 (d, J
119.5 Hz, C), 168.1 (C). 31P NMR (CDCl3, 101.2 MHz,
δ): 23.8. C30H25Br2O3P (624.30). Calcd: C 57.72, H
4.04; found: C 57.78, H 4.11.
[2] For reviews, see (a) Bates, R. W.; Satcharoen, V.
Chem Soc Rev 2002, 31, 12–21; (b) Ma, S. Aldrichim
Acta 2007, 40, 91–102; (c) Hassan, H. H. A. M. Curr
Org Synth 2007, 4, 413–439; (d) Back, T. G.; Clary, K.
N.; Gao, D. Chem Rev 2010, 110, 4498–4553.
[3] (a) de la Mare, P. B. D.; Bolton, R. Electrophilic
Addition to Unsaturated Systems; Elsevier: Amster-
dam, the Netherlands, 1966; pp. 250–266; (b) Case-
rio, M. C. Selectivity in Addition Reactions of Allenes
in Selective Organic Transformations; Thyagarajan,
B. S., Ed.; Wiley: New York; 1970; pp. 239–299; (c)
de la Mare, P. B. D.; Bolton, R. Electrophilic Addi-
tion to Unsaturated Systems; Elsevier: Amsterdam,
the Netherlands, 1982; pp. 317–325; (d) Jacobs, T. L.
Electrophilic Addition to Allenes in the Chemistry of
the Allenes; Landor, S. R., Ed.; Academic Press: New
York, 1982; Vol. 2, Ch. 5, pp. 417–510; (e) Smadja, W.
Chem Rev 1983, 83, 263–320; (f) Ma, S. Ionic Addi-
tion to Allenes in Modern Allene Chemistry; Krause,
N.; Hashmi, A. S. K., Eds.; Wiley-VCH: Weinheim,
Germany, 2004; Vol. 2, pp. 595–699.
Еthyl (3E)-3-benzenesulfanyl-2-chloro-4-(diphen-
ylphosphoryl)-2,4-diphenyl-but-3-enoate (5dc). Yel-
low oil, yield: 1.21 g (1.98 mmol, 66%). Eluent for
TLC: ethyl acetate-hexane = 1:1, Rf 0.71; IR (neat,
cm−1): 1177 (P O), 1441, 1491 (Ph), 1582 (C C),
1
1735 (C O). H NMR (CDCl3, 250.1 MHz, δ): 0.93
(t, J 7.2 Hz, 3H, Me-CH2O), 3.97 (m, 2H, Me-CH2O),
6.70–7.53 (m, 25H, 5Ph). 13C NMR (CDCl3, 62.9
MHz, δ): 18.3 (CH3), 60.8 (CH2), 68.4 (d, J 7.8 Hz, C),
123.4–133.6 (5Ph), 147.2 (d, J 123.5 Hz, C), 152.8 (d, J
31.4 Hz, C), 172.4 (C). 31P NMR (CDCl3, 101.2 MHz,
[4] For reviews, see (a) Angelov, C. M. Phosphorus Sulfur
1983, 15, 177–193; (b) Khusainova, N. G.; Pudovik, A.
N. Russ Chem Rev 1987, 56, 564–578; (c) Alabugin,
I. V.; Brel, V. K. Russ Chem Rev 1997, 66, 205–224.
Heteroatom Chemistry DOI 10.1002/hc

Competitive Electrophilic Cyclization and Addition Reactions of 4-Phosphorylated Allenecarboxylates 71
[5] For a review, see Ma, S. Acc Chem Res 2009, 42,
[11] Enchev, D. D.; Angelov, Ch. M.; Krawchik, E.;
Skowronska, A.; Michalski, J. Phosphorus Sulfur
Silicon 1991, 57, 249–253.
[12] Guo, H.; Qian, R.; Guo, Y.; Ma, S. J Org Chem 2008,
73, 7934–7938.
[13] He, G.; Fu, C.; Ma, S. Tetrahedron 2009, 65, 8035–
8042.
[14] He, G.; Guo, H.; Qian, R.; Guo, Y.; Fu, C.; Ma, S.
Tetrahedron 2009, 65, 4877–4889.
1679–1688.
[6] For a review, see Brel, V. K. Heteroatom Chem 2006,
17, 547–556.
[7] For reviews, see (a) Rao, Y. S. Chem Rev 1964, 64,
353–388; (b) Rao, Y. S. Chem Rev 1976, 76, 625–
994; (c) Knight, D. W. Contemp Org Synth 1994, 287–
315.
[8] (a) Kohler, E. P.; Whitcher, W. J. J Am Chem Soc
1940, 62, 1489–1490; (b) Asknes, G.; Froyen, P.
Acta Chem Stand 1968, 22, 2347–2352; (c) Kresze,
G.; Runge, W.; Ruth, E. Liebigs Ann Chem 1972,
756, 112–127; (d) Musierowicz, S.; Wroblewski, A.;
Krawczyk, H. Tetrahedron Lett 1975, 437–440; (e)
Kresze, G.; Kloimstein, L.; Runge, W. Liebigs Ann
Chem 1976, 979–986; (f) Gill, G. B.; Idris, M. S. H.
Tetrahedron Lett 1985, 26, 4811–4814; (g) Shingu, K.;
Hagishita, S.; Nakagawa, M. Tetrahedron Lett 1967,
4371–4374; (h) Ma, S.; Wu, S. J Org Chem 1999, 64,
9314–9317; (i) Ma, S.; Shi, Z.; Yu, Z. Tetrahedron
1999, 55, 12137–12148; (j) Ma, S.; Wu, S. Tetrahe-
dron Lett 2001, 42, 4075–4077; (k) Ma, S.; Pan, F.;
Hao, X.; Huang, X. Synlett 2004, 85–88; (l) Fu, C.;
Ma, S. Eur J Org Chem 2005, 3942–3945; (m) Chen,
G.; Fu, C.; Ma, S. Tetrahedron 2006, 62, 4444–4452;
(n) Zhou, C.; Ma, Z.; Gu, Z.; Fu, C.; Ma, S. J Org Chem
2008, 73, 772–774.
[15] (a) Ivanov, I. K.; Christov, V. Ch. Heteroatom Chem
2012, 23, 345–351; (b) Ivanov, I. K.; Christov, V. Ch.
Synth Commun. 2013, 43, 800–809.
[16] (a) Part I. Christov, V. Ch.; Nikolova, R., Prodanov,
B. Phosphorus Sulfur Silicon 2000, 166, 275–281; (b)
Part II. Christov, V. Ch.; Prodanov, B. Phosphorus
Sulfur Silicon 2000, 166, 265–273; (c) Part III. Chris-
tov, V. Ch.; Prodanov, B. Heterocyclic Commun 2002,
8, 349–354; (d) Part IV. Christov, V. Ch.; Prodanov,
B. Phosphorus Sulfur Silicon 2002, 177, 243–249; (e)
Part V. Christov, V. Ch.; Prodanov, B. Heterocycles
2002, 57, 1777–1780; (f) Part VI. Christov, V. Ch.; Pro-
danov, B. Synth Commun 2004, 34, 1577–1588; (g)
Part VII. Christov, V. Ch.; Ivanova, J. G. Synth Com-
mun 2006, 36, 2231–2244; (h) Part VIII. Ivanov, I.
K.; Christov, V. Ch. Phosphorus Sulfur Silicon 2013,
188, 913–919; (i) Part IX. Ivanov, I. K.; Parushev,
I. D.; Christov, V. Ch. Heteroatom Chem 2013, 24,
322–331; (j) Part X. Christov, V. Ch.; Ivanov, I. K.;
Ismailov, I. E. Heterocycles 2013, 87, 1903–1916.
[17] Baldwin, J. E. Chem Commun 1976, 734, 736, 738.
[18] Lecher, H.; Holschneider, F. Ber Dtsch Chem Ges
1924, 57, 755–758.
[9] Angelov, Ch. M.; Christov, Ch. Zh.; Ionin, B. I. Zh
Obshch Khim 1982, 52, 264–267.
[10] Khusainova, N. G.; Naumova, L. V.; Berdnikov, E.
A.; Pudovik, A. N. Zh Obshch Khim 1982, 52, 1040–
1046.
Heteroatom Chemistry DOI 10.1002/hc