Bifunctionalized allenes. Part XXIV. Competitive electrophilic cyclization of 5-(dimethoxyphosphoryl)-alka-3,4-dienoates leading to 2,5-dihydro-1, 2-oxaphospholes and 5,6-dihydro-2H-pyranes

Article abstract of DOI:10.1080/10426507.2020.1759063

We report herein a study on the competitive electrophilic cyclization of 5-(dimethoxyphosphoryl)-alka-3,4-dienoates involving 5-endo-trig and 6-endo-trig mode cyclizations. Reaction with electrophiles produces mixtures of the 2-(2-oxo-2,5-dihydro-1,2-oxaphosphol-5-yl)-alkanoates and (6-oxo-5,6-dihydro-2H-pyran-2-yl)-phosphonates by competitive electrophilic cyclization due to the participation of the neighboring phosphonate and carboxylate groups.

Full text of DOI:10.1080/10426507.2020.1759063

Phosphorus, Sulfur, and Silicon and the Related Elements
ISSN: 1042-6507 (Print) 1563-5325 (Online) Journal homepage: https://www.tandfonline.com/loi/gpss20
Bifunctionalized allenes. Part XXIV.
Competitive electrophilic cyclization of 5-
(dimethoxyphosphoryl)-alka-3,4-dienoates leading
to 2,5-dihydro-1, 2-oxaphospholes and 5,6-
dihydro-2H-pyranes
Hasan H. Hasanov, Ivaylo K. Ivanov & Valerij Ch. Christov
To cite this article: Hasan H. Hasanov, Ivaylo K. Ivanov & Valerij Ch. Christov
(2020): Bifunctionalized allenes. Part XXIV. Competitive electrophilic cyclization of 5-
(dimethoxyphosphoryl)-alka-3,4-dienoates leading to 2,5-dihydro-1, 2-oxaphospholes and
5,6-dihydro-2H-pyranes, Phosphorus, Sulfur, and Silicon and the Related Elements, DOI:
10.1080/10426507.2020.1759063
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PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
https://doi.org/10.1080/10426507.2020.1759063
Bifunctionalized allenes. Part XXIV. Competitive electrophilic cyclization of
5-(dimethoxyphosphoryl)-alka-3,4-dienoates leading to 2,5-dihydro-1,
2-oxaphospholes and 5,6-dihydro-2H-pyranes
Hasan H. Hasanov, Ivaylo K. Ivanov, and Valerij Ch. Christov
Department of Chemistry, Faculty of Natural Sciences, Konstantin Preslavsky University of Shumen, Shumen, Bulgaria
ABSTRACT
ARTICLE HISTORY
Received 18 March 2020
Accepted 17 April 2020
We report herein a study on the competitive electrophilic cyclization of 5-(dimethoxyphosphoryl)-
alka-3,4-dienoates involving 5-endo-trig and 6-endo-trig mode cyclizations. Reaction with electro-
philes produces mixtures of the 2-(2-oxo-2,5-dihydro-1,2-oxaphosphol-5-yl)-alkanoates and
(6-oxo-5,6-dihydro-2H-pyran-2-yl)-phosphonates by competitive electrophilic cyclization due to the
participation of the neighboring phosphonate and carboxylate groups.
KEYWORDS
5-(dimethoxyphosphoryl)-
alka-3,4-dienoates; electro-
philic cyclization; 2,5-
dihydro-1,2-oxaphospholes;
5,6-dihydro-2H-pyranes
GRAPHICAL ABSTRACT
Introduction
lead to 2,5-dihydro-1,2-oxaphospholes (Scheme 1, as products
I) or/and 4,3- (as products III) or/and 4,5-adducts (as products
IV) or a mixture of them, depending on the degree of substitu-
tion at the C1 and C3 atoms of the allenic system, the nature of
these substituents, and the type of the reagents.[6]
The electrophilic cyclization involving a-allenic acids and
their derivatives, disubstituted on the c-carbon atom, the so-
called lactonization reaction, leads through an electrophilic
attack on the central atom of the allenic structure and ring
closure to furan-2(5H)-ones (c-lactones).[7]
Dihydropyrans are important intermediates in organic
synthesis due to the presence of the C ¼ C bond as well as
the six-membered ring. Consequently, much attention has
been paid to the development of efficient and diverse syn-
thetic methods for the construction of this six-membered
ring system.[8] Dihydropyrans and their derivatives are
structural subunits frequently found in a wide variety of nat-
ural products which find application as flavor and fragrance
compounds and pharmaceuticals.[9] Dihydropyrans represent
an important structural motif featured in bioactive mole-
cules and natural products,[10] and they are also versatile
intermediates in organic synthesis.[11] It was observed by
Wan and Nelson[12a] that the Ag(I)-catalyzed cyclization of
a b-allenic acid, accelerated by a substoichiometric quantity
of amine base (iPr2NEt), resulted in rapid formation of
In recent years, allenes have atracted the interest of scientists
due to their unique cumulene structure and atypical bio-
logical activities. They are adaptable building blocks with
broad applications in modern synthetic chemistry.[1] Allenes
are key subunits in a variety of natural products and
pharmaceutical molecules.[1b,e,2] Allenyl phosphonates are an
important class of allene-containing, extremely versatile
reagents in organic chemistry, especially for the preparation
of structurally diverse organo-phosphorus compounds and
phosphorus containing heterocyclic compounds.[3]
Several recent articles on allenyl phosphonates and phos-
phine oxides concerning synthesis[4a–e] and various cycliza-
tion reactions[4e–o] have appeared and demonstrate, that the
resulting allenes are very attractive synthetic building blocks
due to their versatile reactivity. Acyclic analogs of nucleotides
containing an allenic skeleton were prepared by Brel and cow-
orkers[5] directly from alcohols by Horner-Mark [2,3]-sigma-
tropic rearrangement of unstable propargylic phosphites.
A literature survey on the reactions of allenyl phosphonates
with electrophilic reagents showed 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 phosphoryl group (O¼ P-C ¼ C¼C) to
give heterocyclic compounds in most cases.[6] The reactions d-lactone (Scheme 1, as products II). Related d-lactone was
CONTACT Valerij Ch. Christov
vchristo@shu.bg; gly73@abv.bg
Department of Chemistry, Faculty of Natural Sciences, Konstantin Preslavsky University of
Shumen, 115, Universitetska Str., BG-9712 Shumen, Bulgaria.
ß 2020 Taylor & Francis Group, LLC

2
H. H. HASANOV ET AL.
Scheme 1. Synthesis of the 5-(dimethoxyphosphoryl)-alka-3,4-dienoates 1a-e.[14]
5-(dimethoxyphosphoryl)-alka-3,4-dienoates 1a-e as 1,3-
bifunctionalized allenes, that comprise an 1-(a-phosphonate)
and a 3-(b-alkoxycarbonyl) group in the allenic system of
double bonds (Schemes 1 and 2). The applications of these
groups as temporary transformers of chemical reactivity of
the allenic system in the synthesis of heterocyclic compounds
are of particular interest. These molecules can be considered a
combination of an allenephosphonate and an allenecarboxy-
late and they are supposed to have different reactivity profiles
in cyclization reactions. In continuation of our communica-
tions[15] on the synthesis and cyclization reactions of the
bifunctionalized allenes, in this paper, we present recent
results of our studies dedicated toward the competitive elec-
trophilic cyclization reaction of a library of 5-(dimethoxy-
phosphoryl)-alka-3,4-dienoates, which improve the scope of
this method for the synthesis of heterocyclic compounds.
E
R
O
Me
I
P
CO2R2
R1
Me
R1
R1
MeO
O
E
R1
R
II
(MeO)2P
O
R
Me
O
O
R1
R1
•
E-Nu
(MeO)2P
R
E
O
O
OR2
Me
R1
(MeO)2P
III
R1
1a-e
O
E
Nu
Nu
CO2R2
1a, R=H, R1=Me, R2=Me
1b, R=H, R1=Et, R2=Et
1c, R=Pr, R1=Et, R2=Et
1d, R=Bu, R1=Et, R2=Et
1e, R=Ph, R1=Et, R2=Et
Me
R1
R
IV
R1
(MeO)2P
CO2R2
O
Results and discussion
Scheme 2. Possible products of the electrophilic reaction of the 5-(dimethoxy-
phosphoryl)-alka-3,4-dienoates 1a-e.[14]
Synthesis of the 5-(dimethoxyphosphoryl)-alka-3,4-
dienoates 1a-e
the product of bromination of 1-bromoallenyl ethyl ester
(b-allenic ester) the formation of which can be explained by
a reaction cascade, starting with the electrophilic addition to
the central allenic carbon atom followed by intramolecular
cyclization accompanied by elimination of ethyl bromi-
de.[12b] On the other hand, intramolecular cyclization of the
diethylphosphono-substituted a-allenic alcohols in the pres-
ence of AgNO3[13a] and CuCl2[13b] yielded 3,6-dihydro-2H-
pyran-4-yl-[5] and 4,5-dihydro-3-furanyl-phosphonates.
With this in mind, and in continuation of our long-stand-
ing program directed toward the synthesis[14] and the devel-
We applied a convenient, efficient, atom economical and
regioselective four-step method to prepare a range of the
5-(dimethoxyphosphoryl)-alka-3,4-dienoates 1a-e.[14] Our
strategy for the synthesis of 1a-e, using our experience on
the preparation of other bifunctionalized allenes,[16] relies
on the well-precedented 2,3-sigmatropic shift of propargylic
phosphites to allenephosphonates. In order to assess this
approach toward the target 5-phosphorylated allenecarboxy-
lates 1a-e, a range of propargylic alcohols was prepared by
the reaction of metallated acetylenes with commercialy avail-
able alkyl 3-oxoalkanoates (Scheme 2). With the required
opment of efficient protocols for the synthesis of heterocyclic alkyl 3-hydroxy-alk-4-ynoates in hand, we were then able to
compounds by electrophilic cyclization reactions[15] of investigate the proposed reaction with dimethyl chlorophos-
bifunctionalized allenes, our attention is drawn to the phite and subsequent atom economical [2,3]-sigmatropic

PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
3
MeS
(MeO)2P
Me
Me
Me
SMe
Me
Me
•
MeSCl
Me
Me
O
(MeO)2P
+
P
CO2Me
MeO
O
O
O
O
O
Me
2a, 44%
OMe
Me
O
1a
3a, 30%
Scheme 3. Synthesis of 2a and 3a by competitive electrophilic cyclization of 5-(dimethoxyphosphoryl)-2,2,3-trimethylpenta-3,4-dienoates 1a. Reagents and
Conditions: E ¼ MeSCl (1.2 eq.), CH2Cl2, ꢀ20 ꢁC, 2 h, rt, 3 h, stirring, column chromatography.
rearrangement of the mediated 5-(dimethoxyphosphany- by the treatment of 5,6-dihydro-2H-pyran-2-ylphosphonate
loxy)-alk-4-ynoates.[14]
3a with 2.2. eq. of NaH followed by reaction with PhCHO
in THF (Scheme 4). We established that the reaction under
these reaction conditions led to the formation of the 6-ben-
zylidene-3,6-dihydro-2H-pyran-2-one 4 as a mixture of
(6E)- and (6Z)-isomer in a ratio of E:Z ¼ 6.4:1 in overall
yield of 63%.
The allenylphosphonates 1a-e were isolated in preparative
amounts, which allowed us to study their chemical behavior
in the reaction with electrophilic reagents. The present paper
is a recent part of our long-term objective to investigate
both the scope and the limitations of the electrophilic cyc-
lization reaction of bifunctionalized allenes, namely the
5-(dimethoxyphosphoryl)-b-allenecarboxylates.
To outline the general terms of this methodology, the
reactions of other 5-(dimethoxyphosphoryl)-alka-3,4-dien-
oates 1b-e with different electrophilic reagents such as sul-
furyl chloride, bromine, methane- and benzene-sulfenyl
chloride, and benzeneselenenyl chloride were investigated.
In all cases (Scheme 5), the interaction afforded mixtures of
the 2-(2-oxo-2,5-dihydro-1,2-oxaphosphol-5-yl)-alkanoates
2b-l and (6-oxo-5,6-dihydro-2H-pyran-2-yl)-phosphonates
3b-l in overall yields of 66–81% in the ratio from 1.26:1 to
1.68:1. These reaction pathways may be interpreted as the
result of competitive electrophilic cyclization of the 5-(dime-
thoxyphosphoryl)-alka-3,4-dienoates 1a-e with participation
of the neighboring phosphonate and alkoxycarbonyl groups
as internal nucleophiles in the favored 5-endo-trig and 6-
endo-trig mode cyclizations.
Competitive electrophilic cyclization of 5-
(dimethoxyphosphoryl)-alka-3,4-dienoates 1a-e
It is necessary to draw the attention to the fact, that concep-
tually three distinct modes of cyclization of the 5-(dimethox-
yphosphoryl)-alka-3,4-dienoates 1a-e are possible. They
depend on the electrophilic atom that forms a new bond
with the central carbon atom of the allenic system, which
seems likely.[6,7,15,17] It is evident that these pathways are
closely connected with the participation of the competitive
intramolecular neighboring phosphonate and/or alkoxycar-
bonyl groups as internal nucleophiles in the final step of the
cyclization. Besides the 5-endo-trig cyclization[18] to the 2-
(2-oxo-2,5-dihydro-1,2-oxaphosphol-5-yl)-alkanoates I, and
the 6-endo-trig cyclization[18] to the (6-oxo-5,6-dihydro-2H-
pyran-2-yl)-phosphonates (d-lactones) II, the electrophilic
addition might afford the 4,3-adducts III and/or the 4,5-
adducts IV (Scheme 1).
We started the present study with the reaction of the
methyl 5-(dimethoxyphosphoryl)-2,2,3-trimethylpenta-3,4-
dienoate 1a with methanesulfenyl chloride (Scheme 3). We
conducted the reaction under the optimized reaction condi-
tions determined in similar reactions of bifunctionalized
allenes[15]—solvent CH2Cl2 at ꢀ20 ꢁC using 1.0 equiv. of the
allenephosphonate and 1.2 equiv. of the electrophilic
reagent. Using spectral methods we established that the reac-
tion under this set of standard reaction conditions in the
favored 5-endo-trig and 6-endo-trig mode afforded a mixture
of methyl 2-(2-methoxy-5-methyl-4-methylsulfenyl-2-oxo-
Thus, on the basis of the available literature data[6,7,17]
and our previous results,[15] a rationale for this reaction is
depicted in Scheme 6. The starting point is the attack of the
electrophile (Clþ, Brþ, Sþ, or Seþ) on both C3-C4- and C4-
C5-double bonds with formation of the cyclic onium
(chloronium, bromonium, thiiranium, or seleniranium) ions
A and B. Then, the ions A and B are easily transformed
into the more stable five-membered cyclic ions C and D via
the attachment of the oxygen atom of the phosphonate and
carboxylate functionality. Further, the intermediates
C
undergo nucleophilic attack on the MeO group of the
phosphonate group and elimination of methyl halide
(MeNu) affording the final cyclic products 2a-l. Similarly,
the ions D transform to the 5,6-dihydro-2H-pyrans 3a-l
after nucleophilic attack on the R2O group of the carboxyl-
ate group and elimination of alkyl halide (R2Nu). The elec-
tronic difference of the two double bonds due to the
presence of two electron-withdrawing groups at the terminal
carbon atoms as well as the steric effect resulting from the
substitutions may both contribute to the observed
regioselectivity.
2,5-dihydro-1,2-oxaphosphol-5-yl)-2-methylpropanoate
2a
and dimethyl (4,5,5-tri-methyl-3-methylsulfenyl-6-oxo-5,6-
dihydro-2H-pyran-2-yl)-phosphonate 3a (Scheme 3) in the
ratio of 1.47:1. Obviously the reaction proceeds by competi-
tive electrophilic cyclization of the allenephosphonate 1a
with the neighboring group participation of phosphonate
and carboxylate groups in the cyclization in very good over-
all isolated yield (74%).
Formation of the cyclic products 2a-l and 3a-l can be
considered in terms of the assumption of concurrent attacks
of the internal nucleophiles (phosphonate and carboxylate
groups) on the cyclic three-membered onium ion A and B.
Obviously, this mechanistic rationale could be explained by
the assumption of favorable trans arrangement of the elec-
In order to confirm the structure of the cyclic product 3a
we carried out a Horner–Wadsworth–Emmons reaction[19] trophile and the internal nucleophile (phosphonate or

4
H. H. HASANOV ET AL.
MeS
(MeO)2P
Me
Me
Me
MeS
Me
Me
Me
1) NaH (2.2 eq.)
Ph
2) PhCHO (1.4 eq.)
O
O
O
O
O
4, E:Z=6.4:1, 63%
3a
Scheme 4. Synthesis of the (6E)-4 and (6Z)-4 by Horner-Wadsworth-Emmons reaction of 3a. Reagents and Conditions: NaH (2.2 eq.), THF, rt, 30 min, PhCHO (1.4 eq.)
THF, 40–50 ꢁC, 120 min, column chromatography.
E
Me
R1
R1
E
R
R
Me
R1
R1
•
R
E-Nu
O
Me
(MeO)2P
+
P
CO2R2
R1
(MeO)2P
MeO
O
O
O
O
R1
OR2
O
O
1a-e
2a-l
3a-l
Entry
R
R1
R2
E
Nu 2, yield,a % 3, yield,a % Ratio 2:3
1
2
H
H
Me
Me
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Me
Me
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
MeS
Cl
Cl
Cl
Br
2a, 44
2b, 48
2c, 45
2d, 43
2e, 48
2f, 42
2g, 44
2h, 45
2i, 41
2j, 42
2k, 46
2l, 43
3a, 30
3b, 33
3c, 32
3d, 28
3e, 31
3f, 27
3g, 28
3h, 28
3i, 25
3j, 25
3k, 30
3l, 29
1.47
1.45
1.40
1.54
1.26
1.56
1.57
1.61
1.64
1.68
1.53
1.48
3
H
Br
4
H
PhSe Cl
Cl Cl
PhSe Cl
5
Pr
Pr
Pr
Bu
Bu
Bu
Ph
Ph
6
7
PhS
Br
Cl
Br
8
9
PhSe Cl
10
11
12
PhS
Br
Cl
Br
Cl
PhS
a Isolated yields.
Scheme 5. Synthesis of the 2-(2-oxo-2,5-dihydro-1,2-oxaphosphol-5-yl)-alkanoates 2a-l and (6-oxo-5,6-dihydro-2H-pyran-2-yl)-phosphonates 3a-l by competitive
electrophilic cyclization of the 5-(dimethoxyphosphoryl)-alka-3,4-dienoates 1a-e. Reagents and Conditions: E ¼ Cl, Br, MeS, PhS, PhSe; Nu ¼ Cl, Br (1.2 eq.), CH2Cl2,
ꢀ20 ꢁC, 2 h, rt, 3 h, stirring, column chromatography.
R
E
R
E
Me
CO2R2
R1
(MeO)2P
2a-l
MeNu
Me
O
Me
CO2R2
R1
P
O
R1
MeO
O
Nu
R1
Nu
E-Nu
C
A
1a-e
E
Me
E
Me
R1
R1
OR2
R
R1
R
3a-l
R2Nu
(MeO)2P
R1
R2
(MeO)2P
O
O
O
O
O
Nu
Nu
B
D
Scheme 6. A rationale for the reaction of the 5-(dimethoxyphosphoryl)-alka-3,4-dienoates 1a-e with electrophilic reagents.
carboxylate groups) and anti-attack of the internal nucleo- further transform to the non-cyclic allylic cations AB
philes on the onium ions A and B. This is supposed to arise (Scheme 7), the predominant formation of the 2,5-dihydro-
from attacks on the allenic C3-C4- and C4-C5-double bonds 1,2-oxaphospholes 2a-j could be explained by charge distri-
anti to the phosphonate and carboxylate groups, respect- bution in allylic resonance form. Larger positive charge
ively, which assisted in the two types cyclization by the should be located in this cation on the carbon atom, which
neighboring groups participation of the internal nucleo- is located far from the acceptor P ¼ O group:
philes. On the other hand, a possible explanation of the two
In the second case, another probable reason for the pre-
types cyclization observed consists of the following: In the dominant participation of the phosphonate group as an
first case, it is possible that the cyclic onium ions A and B internal nucleophile is the higher nucleophilicity of the

PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
5
ꢀ20 ꢁC was added dropwise with stirring a solution of elec-
trophilic reagent (sulfuryl chloride, bromine, methane- or
benzenesulfenyl chloride, or benzeneselenenyl chloride)
(3.6 mmol) in the same solvent (10 mL). The reaction mix-
ture was stirred at the same temperature for 2 h and then at
room temperature for 3 h (reactions were monitored by
TLC). After evaporation of the solvent, the residue was puri-
fied by column chromatography on a silica gel with ethyl
acetate/hexane. The pure products 2a-l and 3a-l had the fol-
lowing properties.
R
E
E
Me
R1
R1
OR2
Me
CO2R2
R
(MeO)2P
O
O
O
(MeO)2P
R1
R1
AB
Scheme 7. Non-cyclic allylic cations AB.
phosphonate oxygen atom in comparison with the carbox-
ylic one, which is in connection with the larger polarization
of the phosphoryl group.
The above mentioned explanation should account for the
results on the study of the reactions of other bifunctional-
ized allenes with electrophilic reagents. Further work in this
area shall focus on exploiting and extending the synthetic
utility of the bifunctionalized allenes for the preparation of
different heterocyclic systems by application of the electro-
philic cyclization methodology.
Methyl 2-(2-methoxy-5-methyl-4-methylsulfenyl-2-oxo-
2,5-dihydro-1,2-oxaphosphol-5-yl)-2-methyl-
propanoate 2a
Yellow oil, yield: 44%. Eluent for TLC: ethyl acetate:hexane
¼ 1:2, Rf 0.69; IR (neat, cmꢀ1): 1017 (C-O-P), 1251 (P ¼ O),
1
1586 (C ¼ C), 1731 (C ¼ O). H NMR (600.1 MHz): d ¼ 1.27
(s, 3H, MeCMe), 1.35 (s, 3H, MeCMe), 1.67 (s, 3H, MeC),
2.41 (s, 3H, MeS), 3.59 (s, 3H, MeOC(O)), 3.69 (d,
J ¼ 9.1 Hz, 3H, MeOP(O)), 5.88 (d, J ¼ 24.6 Hz, 1H, PCH¼).
13C NMR (150.9 MHz): d ¼ 16.7 (J ¼ 4.5 Hz, CH3), 19.4
(J ¼ 1.5 Hz, CH3), 20.8 (J ¼ 1.4 Hz, CH3), 23.3 (J ¼ 4.9 Hz,
CH3), 48.8 (J ¼ 7.8, C), 52.5 (CH3), 52.7 (J ¼ 15.0 Hz, CH3),
96.1 (J ¼ 10.5 Hz, C), 110.6 (J ¼ 71.9 Hz, CH), 164.7
(J ¼ 15.2 Hz, C), 178.1 (J ¼ 4.0 Hz, C). 31P NMR
(242.9 MHz): d ¼ 33.2. HRMS (ESI): m/z calcd for
C11H20O5PS [M þ H]þ 295.3133, found 295.3127. Anal.
Calcd for C11H19O5PS: C 44.89, H 6.51. Found: C 44.97,
H 6.55%.
Experimental
General information
All synthesized compounds were purified by column chro-
matography and characterized by NMR, IR, MS and micro-
analytical data. NMR spectra were recorded with Brucker
Avance II þ 600 (1H at 600.1 MHz, 13C at 150.9 MHz, 31P
1
at 242.9 MHz) spectrometer in CDCl3 solutions. All H and
13C NMR experiments were measured referring to the signal
of internal TMS and the 31P NMR experiments were meas-
ured referring to the signal of external 85% H3PO4. J values
are given in hertz. IR spectra were recorded with an FT-IR
Afinity-1 Shimadzu spectrophotometer. Elemental analyses
were carried out by the Microanalytical Service Laboratory
using Vario EL3 CHNS(O). HRMS were recorded with a
Thermo Scientific Q Exactive hybrid quadrupole-orbitrap
mass spectrometer. Column chromatography was performed
on Kieselgel F25460 (70–230 mesh ASTM, 0.063–0.200 nm,
Merck). CH2Cl2 was distilled over CaH2. Reactions were car-
ried out in oven dried glassware under an argon atmosphere
and exclusion of moisture. All compounds were checked for
purity on TLC plates Kieselgel F254 60 (Merck).
Dimethyl (4,5,5-trimethyl-3-methylsulfenyl-6-oxo-5,6-
dihydro-2H-pyran-2-yl)-phosphonate 3a
Yellow oil, yield: 30%. Eluent for TLC: ethyl acetate:hexane
¼ 1:2, Rf 0.40; IR (neat, cmꢀ1): 1118 (C–O–C), 1259
1
(P ¼ O), 1621 (C ¼ C), 1752 (C ¼ O). H NMR (600.1 MHz):
d ¼ 1.36 (s, 3H, MeCMe), 1.51 (s, 3H, MeCMe), 1.60 (s, 3H,
MeC¼) 2.00 (s, 3H, MeS), 3.92 (d, J ¼ 11.1 Hz, 6H, MeO),
6.01 (d, J ¼ 15.2 Hz, 1H, PCH¼). 13C NMR (150.9 MHz):
d ¼ 16.0 (J ¼ 4.4 Hz, CH3), 15.7 (J ¼ 4.6 Hz, CH3), 23.2
(CH3), 25.4 (CH3), 41.4 (J ¼ 5.0 Hz, C), 52.7 (J ¼ 14.6 Hz,
CH3), 76.1 (J ¼ 112.7 Hz, CH), 128.6 (J ¼ 15.0 Hz, C), 134.9
(J ¼ 8.1 Hz, C), 174.5 (J ¼ 7.8 Hz, C). 31P NMR (242.9 MHz):
d ¼ 25.3. HRMS (ESI): m/z calcd for C11H20O5PS [M þ H]þ
295.3133, found 295.3156. Anal. Calcd for C11H19O5PS: C
44.89, H 6.51. Found: C 44.83, H 6.43%.
Starting materials
Dimethyl and diphenyl disulfide and sulfuryl chloride in
dichloromethane were used to prepare methane- and ben-
zene-sulfenyl chloride. All other chemicals used in this study
were commercially available and were used without add-
itional purification unless otherwise noted. The starting 5-
(dimethoxyphosphoryl)-alka-3,4-dienoates 1a-e were pre-
pared according to earlier reported procedure.[14]
Methyl 2-(4-chloro-2-methoxy-5-methyl-2-oxo-2,5-
dihydro-1,2-oxaphosphol-5-yl)-2-methyl-propanoate 2b
Pale yellow oil, yield: 48%. Eluent for TLC: ethyl acetate:hex-
ane ¼ 1:2, Rf 0.75; IR (neat, cmꢀ1): 1023 (C-O-P), 1249
General procedure for the reactions of the alkyl 5-
(dimethoxyphosphoryl)-alka-3,4-dienoates 1a-e with
electrophilic reagents
1
(P ¼ O), 1580 (C ¼ C), 1730 (C ¼ O). H NMR (600.1 MHz):
d ¼ 1.22 (s, 3H, MeCMe), 1.41 (s, 3H, MeCMe), 1.66 (s, 3H,
MeC), 3.61 (s, 3H, MeOC(O)), 3.78 (d, J ¼ 11.4 Hz, 3H,
To a solution of the 5-(dimethoxyphosphoryl)-alka-3,4-dien- MeOP(O)), 6.14 (d, J ¼ 25.3 Hz, 1H, PCH¼). 13C NMR
oates 1a-e (3.0 mmol) in dry dichloromethane (10 mL) at (150.9 MHz): d ¼ 20.4 (J ¼ 7.9 Hz, CH3), 20.9 (J ¼ 4.8 Hz,

6
H. H. HASANOV ET AL.
CH3), 23.1 (J ¼ 4.9 Hz, CH3), 46.5 (J ¼ 8.1 Hz, C), 50.9 356.1706. Anal. Calcd for C12H20BrO5P: C 40.58, H 5.68.
(CH3), 52.8 (J ¼ 15.0 Hz, CH3), 98.1 (J ¼ 9.7 Hz, C), 112.9 Found: C 40.51, H 5.62%.
(J ¼ 75.0 Hz, CH), 162.7 (J ¼ 39.6 Hz, C), 173.5 (J ¼ 4.5 Hz,
C). 31P NMR (242.9 MHz): d ¼ 34.1. HRMS (ESI): m/z calcd
Ethyl 2-ethyl-2-(2-methoxy-5-methyl-2-oxo-4-
phenylselenenyl-2,5-dihydro-1,2-oxaphosphol-5-yl)-
butanoate 2d
for C10H17ClO5P [M þ H]þ 283.6654, found 283.6647. Anal.
Calcd for C10H16ClO5P: C 42.49, H 5.71. Found: C 42.56,
H 5.65%.
Yellow oil, yield: 43%. Eluent for TLC: ethyl acetate:hexane
¼ 1:2, Rf 0.73; IR (neat, cmꢀ1): 1024 (C-O-P), 1254 (P ¼ O),
Dimethyl (3-chloro-4,5,5-trimethyl-6-oxo-5,6-dihydro-2H-
pyran-2-yl)-phosphonate 3b
1437, 1489 (Ph), 1579 (C ¼ C), 1729 (C ¼ O). 1H NMR
(600.1 MHz): d ¼ 0.91 (t, J ¼ 6.8 Hz, 6H, MeCH2), 1.21 (t,
Yellow oil, yield: 33%. Eluent for TLC: ethyl acetate:hexane J ¼ 7.0 Hz, 3H, MeCH2O), 1.61 (s, 3H, MeC), 1.78 (m, 4H,
¼ 1:2, Rf 0.41; IR (neat, cmꢀ1): 1121 (C–O–C), 1257 MeCH2), 3.66 (d, J ¼ 11.5 Hz, 3H, MeO), 4.03 (m, 2H,
(P ¼ O), 1619 (C ¼ C), 1751 (C ¼ O). H NMR (600.1 MHz): MeCH2O), 6.39 (d, J ¼ 27.9 Hz, 1H, PCH¼). 13C NMR
1
d ¼ 1.41 (s, 3H, MeCMe), 1.56 (s, 3H, MeCMe), 2.11 (s, 3H, (150.9 MHz): d ¼ 10.5 (CH3), 14.4 (CH3), 18.1 (J ¼ 4.6 Hz,
Me-‘¼), 3.88 (d, J ¼ 10.5 Hz, 6H, MeO), 5.40 (d, CH2), 20.1 (J ¼ 4.7 Hz, CH2), 20.3 (J ¼ 7.9 Hz, CH3), 53.0
J ¼ 15.0 Hz, 1H, PCH¼). 13C NMR (150.9 MHz): d ¼ 12.0 (J ¼ 15.0 Hz, CH3), 58.1 (J ¼ 7.8 Hz, C), 61.8 (CH2), 96.2
(J ¼ 4.7 Hz, CH3), 23.4 (CH3), 25.0 (CH3), 40.9 (J ¼ 5.0 Hz, (J ¼ 9.8 Hz, C), 111.1 (J ¼ 72.4 Hz, CH), 129.1 (CH), 129.3
C), 52.8 (J ¼ 14.5 Hz, CH3), 80.5 (J ¼ 112.9 Hz, CH), 117.7 (CH), 131.1 (C), 138.1 (CH), 174.3 (J ¼ 4.6 Hz, C), 175.8
(J ¼ 39.2 Hz, C), 135.0 (J ¼ 8.2 Hz, C), 168.5 (J ¼ 8.1 Hz, C). (J ¼ 14.3 Hz, C). 31P NMR (242.9 MHz): d ¼ 36.0. HRMS
31P NMR (242.9 MHz): d ¼ 26.2. HRMS (ESI): m/z calcd for (ESI): m/z calcd for C19H28O5PSe [M þ H]þ 446.3564, found
C10H17ClO5P [M þ H]þ 283.6654, found 283.6661. Anal. 446.3571. Anal. Calcd for C19H27O5PSe: C 51.24, H 6.11.
Calcd for C10H16ClO5P: C 42.49, H 5.71. Found: C 42.42, Found: C 51.17, H 6.05%.
H 5.63%.
Dimethyl (5,5-diethyl-4-methyl-6-oxo-3-phenylselenenyl-
Ethyl 2-(4-bromo-2-methoxy-5-methyl-2-oxo-2,5-dihydro- 5,6-dihydro-2H-pyran-2-yl)-phosphonate 3d
1,2-oxaphosphol-5-yl)-2-ethyl-butanoate 2c
Yellow oil, yield: 28%. Eluent for TLC: ethyl acetate:hexane
Pale yellow oil, yield: 45%. Eluent for TLC: ethyl acetate:hex- ¼ 1:2, Rf 0.41; IR (neat, cmꢀ1): 1122 (C–O–C), 1261
ane ¼ 1:2, Rf 0.71; IR (neat, cmꢀ1): 1018 (C-O-P), 1260 (P ¼ O), 1439, 1492 (Ph), 1621 (C ¼ C), 1749 (C ¼ O). H
1
1
(P ¼ O), 1582 (C ¼ C), 1733 (C ¼ O). H NMR (600.1 MHz): NMR (600.1 MHz): d ¼ 0.78 (t, J ¼ 7.4 Hz, 6H, MeCH2), 1.48
d ¼ 0.91 (t, J ¼ 6.8 Hz, 6H, MeCH2), 1.21 (t, J ¼ 7.0 Hz, 3H, (m, 4H, MeCH2), 1.94 (s, 3H, Me-‘¼), 3.91 (d, J ¼ 10.5 Hz,
MeCH2O), 1.74 (s, 3H, MeC), 1.78 (m, 4H, MeCH2), 3.70 6H, MeO), 6.07 (d, J ¼ 15.0 Hz, 1H, PCH¼). 13C NMR
(d, J ¼ 11.4 Hz, 3H, MeO), 4.03 (m, 2H, MeCH2O), 6.51 (d, (150.9 MHz): d ¼ 11.2 (CH3), 15.4 (J ¼ 5.1, CH3), 17.8
J ¼ 25.4 Hz, 1H, PCH¼). 13C NMR (150.9 MHz): d ¼ 10.9 (CH2), 19.7 (CH2), 52.7 (J ¼ 14.4 Hz, CH3), 53.9 (J ¼ 5.0, C),
(CH3), 14.3 (CH3), 19.0 (J ¼ 4.6 Hz, CH2), 21.1 (J ¼ 4.6 Hz, 82.4 (J ¼ 114.1 Hz, CH), 105.1 (J ¼ 14.6 Hz, C), 128.4
CH2), 22.3 (J ¼ 4.7 Hz, CH3), 50.9 (J ¼ 7.9 Hz, C), 52.7 (J ¼ 43.2 Hz, C), 128.7 (J ¼ 9.9 Hz, CH), 129.4 (CH),
(J ¼ 14.4 Hz, CH3), 60.4 (CH2), 90.9 (J ¼ 9.8 Hz, C), 109.5 136.31 J ¼ 4.9 Hz, (CH), 138.4 (J ¼ 7.9 Hz, C), 171.9
(J ¼ 74.8 Hz, CH), 143.9 (J ¼ 32.8 Hz, C), 173.8 (J ¼ 5.0 Hz, (J ¼ 8.1 Hz, C). 31P NMR (242.9 MHz): d ¼ 24.4. HRMS
C). 31P NMR (242.9 MHz): d ¼ 35.2. HRMS (ESI): m/z calcd (ESI): m/z calcd for C18H26O5PSe [M þ H]þ 432.3298, found
for C13H23BrO5P [M þ H]þ 370.1965, found 370.1954. Anal. 632.3289. Anal. Calcd for C18H25O5PSe: C 50.12, H 5.84.
Calcd for C13H22BrO5P: C 42.29, H 6.01. Found: C 42.37, Found: C 50.20, H 5.89%.
H 5.96%.
Ethyl 2-(4-chloro-2-methoxy-5-methyl-2-oxo-3-propyl-
Dimethyl (3-bromo-5,5-diethyl-4-methyl-6-oxo-5,6-
dihydro-2H-pyran-2-yl)-phosphonate 3c
2,5-dihydro-1,2-oxaphosphol-5-yl)-2-ethyl-butanoate 2e
Pale yellow oil, yield: 48%. Eluent for TLC: ethyl acetate:hex-
Yellow oil, yield: 32%. Eluent for TLC: ethyl acetate:hexane ane ¼ 1:2, Rf 0.73; IR (neat, cmꢀ1): 1021 (C-O-P), 1260
¼ 1:2, Rf 0.38; IR (neat, cmꢀ1): 1123 (C–O–C), 1259 (P ¼ O), 1584 (C ¼ C), 1726 (C ¼ O). H NMR (600.1 MHz):
1
1
(P ¼ O), 1619 (C ¼ C), 1753 (C ¼ O). H NMR (600.1 MHz): d ¼ 0.81 (t, J ¼ 7.0 Hz, 3H, MeCH2CH2), 0.90 (t, J ¼ 6.8 Hz,
d ¼ 0.76 (t, J ¼ 7.4 Hz, 6H, MeCH2), 1.52 (m, 4H, MeCH2), 6H, MeCH2), 1.21 (t, J ¼ 7.0 Hz, 3H, MeCH2O), 1.54 (m,
2.18 (s, 3H, Me-‘¼), 3.89 (d, J ¼ 10.4 Hz, 6H, MeO), 6.03 2H, MeCH2CH2), 1.65 (s, 3H, MeC), 1.70–1.88 (m, 4H,
(d, J ¼ 15.5 Hz, 1H, PCH¼). 13C NMR (150.9 MHz): d ¼ 11.1 MeCH2), 1.96 (m, 2H, MeCH2CH2), 3.68 (d, J ¼ 11.3 Hz,
(CH3), 16.1 (J ¼ 5.1, CH3), 18.6 (CH2), 20.4 (CH2), 48.7 3H, MeO), 4.14 (m, 2H, MeCH2O). 13C NMR (150.9 MHz):
(J ¼ 4.9 Hz, C), 52.9 (J ¼ 14.5, CH3), 80.2 (J ¼ 114.8 Hz, CH), d ¼ 10.1 (CH3), 14.6 (CH3), 15.4 (J ¼ 4.6 Hz, CH3), 20.0
111.8 (J ¼ 48.8 Hz, C), 143.7 (J ¼ 8.0 Hz, C), 168.3 (J ¼ 4.9 Hz, CH2), 20.7 (J ¼ 8.2 Hz, CH2), 20.9 (J ¼ 7.8 Hz,
(J ¼ 7.8 Hz, C). 31P NMR (242.9 MHz): d ¼ 25.7. HRMS CH3), 21.7 (J ¼ 4.7 Hz, CH2), 31.5 (J ¼ 6.3 Hz, CH2), 49.9
(ESI): m/z calcd for C12H21BrO5P [M þ H]þ 356.1699, found (J ¼ 15.0 Hz, CH3), 51.3 (J ¼ 8.0 Hz, C), 61.7 (CH2), 94.9

PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
7
(J ¼ 10.2 Hz, C), 127.9 (J ¼ 98.8 Hz, C), 156.0 (J ¼ 39.3 Hz, (m, 2H, MeCH2CH2), 3.85 (d, J ¼ 10.5 Hz, 6H, MeO),
C), 176.1 (J ¼ 5.0 Hz, C). 31P NMR (242.9 MHz): d ¼ 22.8.
HRMS (ESI): m/z calcd for C16H29ClO5P [M þ H]þ
367.8249, found 367.8260. Anal. Calcd for C16H28ClO5P: C
52.39, H 7.69. Found: C 52.46, H 7.77%.
7.41–7.50 (m, 5H, Ph). 13C NMR (150.9 MHz): d ¼ 10.9
(CH3), 15.3 (J ¼ 4.8 Hz, CH3), 16.1 (J ¼ 4.8 Hz, CH3), 17.3
(J ¼ 8.1 Hz, CH2), 17.5 (CH2), 19.5 (CH2), 35.2 (J ¼ 5.7 Hz,
CH2), 53.1 (J ¼ 14.6 Hz, CH3), 53.4 (J ¼ 4.7, C), 90.5
(J ¼ 125.4 Hz, C), 110.5 (J ¼ 14.0 Hz, C), 128.5 (CH), 128.8
(C), 129.6 (CH), 138.6 (CH), 138.9 (J ¼ 8.1 Hz, C), 174.7
(J ¼ 7.8 Hz, C). 31P NMR (242.9 MHz): d ¼ 23.9. HRMS
(ESI): m/z calcd for C21H32O5PSe [M þ H]þ 374.4095, found
374.4089. Anal. Calcd for C21H31O5PSe: C 53.28, H 6.60.
Found: C 53.22, H 6.64%.
Dimethyl (3-chloro-5,5-diethyl-4-methyl-6-oxo-2-propyl-
5,6-dihydro-2H-pyran-2-yl)-phosphonate 3e
Yellow oil, yield: 31%. Eluent for TLC: ethyl acetate:hexane
¼ 1:2, Rf 0.42; IR (neat, cmꢀ1): 1119 (C–O–C), 1265
1
(P ¼ O), 1620 (C ¼ C), 1749 (C ¼ O). H NMR (600.1 MHz):
d ¼ 0.79 (t, J ¼ 7.4 Hz, 6H, MeCH2), 1.09 (t, J ¼ 7.1 Hz, 3H,
MeCH2CH2), 1.52–1.77 (m, 4H, MeCH2), 1.76 (m, 2H,
MeCH2CH2), 2.03 (s, 3H, Me-‘¼), 2.27 (m, 2H,
MeCH2CH2), 3.83 (d, J ¼ 10.5 Hz, 6H, MeO). 13C NMR
(150.9 MHz): d ¼ 10.9 (CH3), 11.8 (CH3), 15.2 (J ¼ 4.9 Hz,
CH3), 19.1 (J ¼ 8.1 Hz, CH2), 19.2 (CH2), 20.8 (CH2), 36.2
(J ¼ 6.2 Hz, CH2), 48.3 (J ¼ 4.5 Hz, C), 53.1 (J ¼ 14.7, CH3),
88.9 (J ¼ 124.6 Hz, C), 127.1 (J ¼ 40.2 Hz, C), 138.5
(J ¼ 7.7 Hz, C), 169.4 (J ¼ 7.8 Hz, C). 31P NMR (242.9 MHz):
d ¼ 23.1. HRMS (ESI): m/z calcd for C15H27ClO5P [M þ H]þ
353.7983, found 353.7989. Anal. Calcd for C15H26ClO5P: C
51.07, H 7.43. Found: C 51.12, H 7.50%.
Ethyl 2-ethyl-2-(2-methoxy-5-methyl-2-oxo-4-
phenylsulfenyl-3-propyl-2,5-dihydro-1,2-oxaphosphol-
5-yl)-butanoate 2g
Yellow oil, yield: 44%. Eluent for TLC: ethyl acetate:hexane
¼ 1:4, Rf 0.73; IR (neat, cmꢀ1): 1023 (C-O-P), 1256 (P ¼ O),
1438, 1492 (Ph), 1580 (C ¼ C), 1733 (C ¼ O). 1H NMR
(600.1 MHz): d ¼ 0.83 (t, J ¼ 7.0 Hz, 3H, MeCH2CH2), 0.90
(t, J ¼ 6.8 Hz, 6H, MeCH2), 1.22 (t, J ¼ 7.1 Hz, 3H,
MeCH2O), 1.66 (m, 2H, MeCH2CH2), 1.69 (s, 3H, MeC),
1.88–1.97 (m, 4H, MeCH2), 2.19 (m, 2H, MeCH2CH2), 3.74
(d, J ¼ 11.4 Hz, 3H, MeO), 4.11 (m, 2H, MeCH2O),
7.19–7.43 (m, 5H, Ph). 13C NMR (150.9 MHz): d ¼ 10.2
(CH3), 13.8 (CH3), 14.8 (J ¼ 4.6 Hz, CH3), 20.3 (J ¼ 5.1 Hz,
CH2), 21.4 (J ¼ 8.0 Hz, CH2), 22.6 (J ¼ 5.0 Hz, CH2), 24.9
(J ¼ 7.9 Hz, CH3), 32.4 (J ¼ 5.8 Hz, CH2), 51.8 (J ¼ 14.2 Hz,
CH3), 53.8 (J ¼ 7.8 Hz, C), 61.6 (CH2), 91.9 (J ¼ 9.8 Hz, C),
125.9 (CH), 127.0 (CH), 129.1 (CH), 130.7 (J ¼ 98.5 Hz, C),
Ethyl 2-ethyl-2-(2-methoxy-5-methyl-2-oxo-4-
phenylselenenyl-3-propyl-2,5-dihydro-1,2-oxaphosphol-
5-yl)-butanoate 2f
Yellow oil, yield: 42%. Eluent for TLC: ethyl acetate:hexane
¼ 1:2, Rf 0.70; IR (neat, cmꢀ1): 1020 (C-O-P), 1258 (P ¼ O),
1437, 1489 (Ph), 1582 (C ¼ C), 1730 (C ¼ O). 1H NMR 140.1 (J ¼ 5.0 Hz, C), 160.1 (J ¼ 15.0 Hz, C), 177.5
(J ¼ 4.8 Hz, C). 31P NMR (242.9 MHz): d ¼ 26.7. HRMS
(ESI): m/z calcd for C22H34O5PS [M þ H]þ 441.5421, found
441.5416. Anal. Calcd for C22H33O5PS: C 59.98, H 7.55.
Found: C 60.06, H 7.61%.
(600.1 MHz): d ¼ 0.82 (t, J ¼ 7.1 Hz, 3H, MeCH2CH2), 0.90
(t, J ¼ 6.8 Hz, 6H, MeCH2), 1.21 (t, J ¼ 7.0 Hz, 3H,
MeCH2O), 1.42 (m, 2H, MeCH2CH2), 1.60 (s, 3H, MeC),
1.66–1.77 (m, 4H, MeCH2), 2.09 (m, 2H, MeCH2CH2), 3.69
(d, J ¼ 11.0 Hz, 3H, MeO), 4.07 (m, 2H, MeCH2O),
7.32–7.45 (m, 5H, Ph). 13C NMR (150.9 MHz): d ¼ 10.0
(CH3), 14.6 (CH3), 15.0 (J ¼ 4.7 Hz, CH3), 17.9 (J ¼ 4.7 Hz, Dimethyl (5,5-diethyl-4-methyl-6-oxo-3-phenylsulfenyl-2-
CH2), 19.2 (J ¼ 8.1 Hz, CH2), 19.9 (J ¼ 7.9 Hz, CH3), 20.1
propyl-5,6-dihydro-2H-pyran-2-yl)-phosphonate 3g
(J ¼ 4.6 Hz, CH2), 32.0 (J ¼ 5.7 Hz, CH2), 51.2 (J ¼ 14.5 Hz,
Yellow oil, yield: 28%. Eluent for TLC: ethyl acetate:hexane
CH3), 57.4 (J ¼ 8.0 Hz, C), 61.5 (CH2), 96.1 (J ¼ 9.9 Hz, C),
¼ 1:4, Rf 0.39; IR (neat, cmꢀ1): 1117 (C–O–C), 1260
129.0 (CH), 129.2 (CH), 129.7 (C), 128.4 (J ¼ 97.7 Hz, C),
1
138.2 (CH), 171.7 (J ¼ 15.0 Hz, C), 176.9 (J ¼ 5.0 Hz, C). 31P
NMR (242.9 MHz): d ¼ 26.6. HRMS (ESI): m/z calcd for
C22H34O5PSe [M þ H]þ 488.4361, found 488.4369. Anal.
Calcd for C22H33O5PSe: C 54.21, H 6.82. Found: C 54.15,
H 6.75%.
(P ¼ O), 1439, 1493 (Ph), 1623 (C ¼ C), 1750 (C ¼ O). H
NMR (600.1 MHz): d ¼ 0.75 (t, J ¼ 7.3 Hz, 6H, MeCH2), 1.13
(t, J ¼ 7.2 Hz, 3H, MeCH2CH2), 1.66–1.87 (m, 4H, MeCH2),
1.90 (m, 2H, MeCH2CH2), 1.96 (s, 3H, Me-‘¼), 2.39–2.50
(m, 2H, MeCH2CH2), 3.86 (d, J ¼ 10.6 Hz, 6H, MeO),
7.22–7.47 (m, 5H, Ph). 13C NMR (150.9 MHz): d ¼ 10.7
(CH3), 15.2 (J ¼ 4.7 Hz, CH3), 19.4 (J ¼ 7.8 Hz, CH2), 20.0
(J ¼ 4.6 Hz, CH3), 20.3 (CH2), 21.6 (CH2), 36.4 (J ¼ 5.7 Hz,
CH2), 50.4 (J ¼ 5.0 Hz, C), 52.9 (J ¼ 5.1 Hz, CH3), 84.7
(J ¼ 125.5 Hz, C), 125.8 (CH), 127.3 (CH), 129.2 (CH), 129.5
(J ¼ 14.5 Hz, C), 135.0 (C), 141.7 (J ¼ 8.2 Hz, C), 174.7
(J ¼ 7.9 Hz, C). 31P NMR (242.9 MHz): d ¼ 23.9. HRMS
(ESI): m/z calcd for C21H32O5PS [M þ H]þ 427.5155, found
427.5149. Anal. Calcd for C21H31O5PS: C 59.14, H 7.33.
Dimethyl (5,5-diethyl-4-methyl-6-oxo-3-phenylselenenyl-
2-propyl-5,6-dihydro-2H-pyran-2-yl)-phosphonate 3f
Yellow oil, yield: 27%. Eluent for TLC: ethyl acetate:hexane
¼ 1:2, Rf 0.40; IR (neat, cmꢀ1): 1118 (C–O–C), 1262
1
(P ¼ O), 1440, 1488 (Ph), 1622 (C ¼ C), 1752 (C ¼ O). H
NMR (600.1 MHz): d ¼ 0.76 (t, J ¼ 7.3 Hz, 6H, MeCH2), 1.09
(t, J ¼ 7.1 Hz, 3H, MeCH2CH2), 1.46–1.68 (m, 4H, MeCH2),
1.61 (m, 2H, MeCH2CH2), 1.95 (s, 3H, Me-‘¼), 2.27–2.45 Found: C 59.20, H 7.37%.

8
H. H. HASANOV ET AL.
Ethyl 2-(4-bromo-3-butyl-2-methoxy-5-methyl-2-oxo-2,
5-dihydro-1,2-oxaphosphol-5-yl)-2-ethyl-butanoate 2h
C), 61.8 (CH2), 96.7 (J ¼ 10.1 Hz, C), 128.6 (J ¼ 100.1 Hz, C),
129.0 (J ¼ 4.7 Hz, C), 129.2 (CH), 129.4 (CH), 137.4 (CH),
172.6 (J ¼ 14.9 Hz, C), 176.8 (J ¼ 5.0 Hz, C). 31P NMR
(242.9 MHz): d ¼ 28.0. HRMS (ESI): m/z calcd for
C23H36O5PSe [M þ H]þ 502.4627, found 502.4641. Anal.
Calcd for C23H35O5PSe: C 55.09, H 7.04. Found: C 55.16,
H 6.99%.
Pale yellow oil, yield: 45%. Eluent for TLC: ethyl acetate:hex-
ane ¼ 1:2, Rf 0.76; IR (neat, cmꢀ1): 1017 (C-O-P), 1255
1
(P ¼ O), 1581 (C ¼ C), 1732 (C ¼ O). H NMR (600.1 MHz):
d ¼ 0.82 (m, 3H, Me(CH2)3, 0.93 (t, J ¼ 6.8 Hz, 6H, MeCH2),
1.22 (t, J ¼ 7.0 Hz, 3H, MeCH2O), 1.27–1.37 (m, 4H,
Me(CH2)2CH2), 1.71–1.90 (m, 4H, MeCH2), 1.74 (s, 3H,
MeC), 2.07–2.14 (m, 2H, Me(CH2)2CH2), 3.79 (d,
J ¼ 11.4 Hz, 3H, MeO), 4.06–4.13 (m, 2H, MeCH2O). 13C
NMR (150.9 MHz): d ¼ 10.0 (CH3), 14.2 (CH3), 14.4 (CH3),
19.1 (J ¼ 4.7 Hz, CH2), 20.9 (J ¼ 4.7 Hz, CH2), 22.0
(J ¼ 5.1 Hz, CH2), 22.5 (J ¼ 8.1 Hz, CH3), 29.7 (J ¼ 8.0 Hz,
Dimethyl (2-butyl-5,5-diethyl-4-methyl-6-oxo-3-
phenylselenenyl-5,6-dihydro-2H-pyran-2-yl)-
phosphonate 3i
CH2), 30.1 (J ¼ 5.8 Hz, CH2), 51.0 (J ¼ 7.8 Hz, C), 52.4 Yellow oil, yield: 25%. Eluent for TLC: ethyl acetate:hexane
¼ 1:2, Rf 0.44; IR (neat, cmꢀ1): 1117 (C–O–C), 1265
(J ¼ 15.0 Hz, CH3), 61.3 (CH2), 93.8 (J ¼ 9.7 Hz, C), 126.4
(J ¼ 147.4 Hz, C), 139.9 (J ¼ 50.5 Hz, C), 176.7 (J ¼ 5.0 Hz,
C). 31P NMR (242.9 MHz): d ¼ 27.2. HRMS (ESI): m/z calcd
for C17H31BrO5P [M þ H]þ 426.3028, found 426.3037. Anal.
Calcd for C17H30BrO5P: C 48.01, H 7.11. Found: C 47.94,
H 7.06%.
1
(P ¼ O), 1441, 1491 (Ph), 1624 (C ¼ C), 1748 (C ¼ O). H
NMR (600.1 MHz): d ¼ 0.76 (t, J ¼ 7.3 Hz, 6H, MeCH2), 0.89
(t, J ¼ 6.0 Hz, 3H, Me(CH2)3, 1.41–1.72 (m, 8H, MeCH2,
Me(CH2)2CH2), 1.93 (s, 3H, Me-‘¼), 2.36–2.60 (m, 2H,
Me(CH2)2CH2), 3.69 (d, J ¼ 11.1 Hz, 6H, MeO), 7.47–7.53
(m, 5H, Ph). 13C NMR (150.9 MHz): d ¼ 10.9 (CH3), 14.5
(CH3), 16.5 (J ¼ 5.1 Hz, CH3), 17.3 (CH2), 19.5 (CH2), 22.2
(J ¼ 4.8 Hz, CH2), 26.5 (J ¼ 7.9 Hz, CH2), 33.2 (J ¼ 5.8 Hz,
CH2), 53.4 (J ¼ 9.8 Hz, C), 53.9 (J ¼ 14.6 Hz, CH3), 90.4
(J ¼ 126.0 Hz, C), 110.6 (J ¼ 15.0 Hz, C), 128.0 (J ¼ 4.7 Hz,
C), 128.7 (CH), 129.0 (CH), 134.7 (J ¼ 7.9 Hz, C), 137.4
(CH), 174.5 (J ¼ 7.8 Hz, C). 31P NMR (242.9 MHz): d ¼ 25.9.
HRMS (ESI): m/z calcd for C22H34O5PSe [M þ H]þ
488.4361, found 488.4377. Anal. Calcd for C22H33O5PSe: C
54.21, H 6.82. Found: C 54.14, H 6.74%.
Dimethyl (3-bromo-2-butyl-5,5-diethyl-4-methyl-6-oxo-
5,6-dihydro-2H-pyran-2-yl)-phosphonate 3h
Yellow oil, yield: 28%. Eluent for TLC: ethyl acetate:hexane
¼ 1:2, Rf 0.44; IR (neat, cmꢀ1): 1121 (C–O–C), 1260
1
(P ¼ O), 1622 (C ¼ C), 1749 (C ¼ O). H NMR (600.1 MHz):
d ¼ 0.79 (t, J ¼ 7.3 Hz, 6H, MeCH2), 0.90 (m, 3H, Me(CH2)3,
1.42–1.78 (m, 8H, MeCH2, Me(CH2)2CH2), 2.15 (s, 3H, Me-
‘¼), 2.27–2.50 (m, 2H, Me(CH2)2CH2), 3.88 (d, J ¼ 10.6 Hz,
6H, MeO). 13C NMR (150.9 MHz): d ¼ 10.9 (CH3), 14.5
(CH3), 16.7 (J ¼ 5.0 Hz, CH3), 18.4 (CH2), 20.6 (CH2), 21.7
(J ¼ 5.0 Hz, CH2), 27.4 (J ¼ 7.7 Hz, CH2), 33.8 (J ¼ 5.7 Hz,
CH2), 49.2 (J ¼ 4.7 Hz, C), 53.5 (J ¼ 14.6 Hz, CH3), 87.4
(J ¼ 124.8 Hz, C), 115.8 (J ¼ 50.4 Hz, C), 141.9 (J ¼ 8.0 Hz,
C), 170.9 (J ¼ 7.8 Hz, C). 31P NMR (242.9 MHz): d ¼ 26.7.
HRMS (ESI): m/z calcd for C16H29BrO5P [M þ H]þ
412.2762, found 412.2748. Anal. Calcd for C16H28BrO5P: C
46.73, H 6.86. Found: C 46.78, H 6.90%.
Ethyl 2-(3-butyl-2-methoxy-5-methyl-2-oxo-4-
phenylsulfenyl-2,5-dihydro-1,2-oxaphosphol-5-yl)-
2-ethyl-butanoate 2j
Yellow oil, yield: 42%. Eluent for TLC: ethyl acetate:hexane
¼ 1:4, Rf 0.71; IR (neat, cmꢀ1): 1021 (C-O-P), 1254 (P ¼ O),
1439, 1490 (Ph), 1586 (C ¼ C), 1729 (C ¼ O). 1H NMR
(600.1 MHz): d ¼ 0.83 (t, J ¼ 6.7 Hz, 3H, Me(CH2)3, 0.91 (t,
J ¼ 7.0 Hz, 6H, MeCH2), 1.20 (t, J ¼ 7.2 Hz, 3H, MeCH2O),
1.25–1.50 (m, 4H, Me(CH2)2CH2), 1.64 (s, 3H, MeC),
1.83–2.00 (m, 4H, 2xMeCH2), 2.20–2.29 (m, 2H,
Me(CH2)2CH2), 3.75 (d, J ¼ 11.4 Hz, 3H, MeO), 4.07–4.12
(m, 2H, MeCH2O), 7.14–7.40 (m, 5H, Ph). 13C NMR
(150.9 MHz): d ¼ 10.0 (CH3), 14.1 (CH3), 14.4 (CH3), 20.2
(CH2), 21.3 (J ¼ 5.1 Hz, CH2), 22.5 (J ¼ 5.1 Hz, CH2), 25.3
(J ¼ 8.1 Hz, CH3), 30.2 (J ¼ 7.9 Hz, CH2), 30.6 (J ¼ 7.9 Hz,
CH2), 52.4 (J ¼ 15.1 Hz, CH3), 53.4 (J ¼ 7.8 Hz, C), 61.8
(CH2), 91.4 (J ¼ 10.1 Hz, C), 125.1 (J ¼ 5.1 Hz, C), 126.7
(CH), 129.2 (CH), 130.0 (J ¼ 99.4 Hz, C), 136.1 (CH), 160.2
(J ¼ 14.7 Hz, C), 177.5 (J ¼ 5.0 Hz, C). 31P NMR
(242.9 MHz): d ¼ 26.9. HRMS (ESI): m/z calcd for
C23H36O5PS [M þ H]þ 455.5687, found 455.5661. Anal.
Calcd for C23H35O5PS: C 60.77, H 7.76. Found: C 60.84,
Ethyl 2-(3-butyl-2-methoxy-5-methyl-2-oxo-4-
phenylselenenyl-2,5-dihydro-1,2-oxaphosphol-5-yl)-
2-ethyl-butanoate 2i
Yellow oil, yield: 41%. Eluent for TLC: ethyl acetate:hexane
¼ 1:2, Rf 0.72; IR (neat, cmꢀ1): 1022 (C-O-P), 1257 (P ¼ O),
1437, 1487 (Ph), 1580 (C ¼ C), 1727 (C ¼ O). 1H NMR
(600.1 MHz): d ¼ 0.79 (t, J ¼ 6.6 Hz, 3H, Me(CH2)3, 0.90 (t,
J ¼ 7.1 Hz, 6H, MeCH2), 1.21 (t, J ¼ 7.2 Hz, 3H, MeCH2O),
1.24–1.34 (m, 4H, Me(CH2)2CH2), 1.62 (s, 3H, MeC),
1.74–1.83 (m, 4H, MeCH2), 2.15–2.24 (m, 2H,
Me(CH2)2CH2), 3.73 (d, J ¼ 11.1 Hz, 3H, MeO), 4.03–4.10
(m, 2H, MeCH2O), 7.32–7.46 (m, 5H, Ph). 13C NMR
(150.9 MHz): d ¼ 10.2 (CH3), 14.0 (CH3), 14.4 (CH3), 18.0
(J ¼ 4.7 Hz, CH2), 20.1 (J ¼ 4.6 Hz, CH2), 20.7 (J ¼ 7.8 Hz,
CH3), 21.6 (J ¼ 4.6 Hz, CH2), 28.7 (J ¼ 7.6 Hz, CH2), 30.3
(J ¼ 8.0 Hz, CH2), 51.8 (J ¼ 14.6 Hz, CH3), 57.0 (J ¼ 7.8 Hz, H 7.82%.

PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
9
Dimethyl (2-butyl-5,5-diethyl-4-methyl-6-oxo-
3-phenylsulfenyl-5,6-dihydro-2H-pyran-2-yl)-
phosphonate 3j
(242.9 MHz): d ¼ 24.1. HRMS (ESI): m/z calcd for
C18H25BrO5P [M þ H]þ 432.2659, found 432.2644. Anal.
Calcd for C18H24BrO5P: C 50.13, H 5.61. Found: C 50.20,
H 5.57%.
Yellow oil, yield: 25%. Eluent for TLC: ethyl acetate:hexane
¼ 1:4, Rf 0.42; IR (neat, cmꢀ1): 1122 (C–O–C), 1266
1
(P ¼ O), 1438, 1486 (Ph), 1620 (C ¼ C), 1751 (C ¼ O). H Ethyl 2-ethyl-2-(2-methoxy-5-methyl-2-oxo-3-phenyl-4-
phenylsulfenyl-2,5-dihydro-1,2-oxaphosphol-5-yl)-
NMR (600.1 MHz): d ¼ 0.78 (t, J ¼ 7.5 Hz, 6H, MeCH2), 0.89
butanoate 2l
(t, J ¼ 6.1 Hz, 3H, Me(CH2)3, 1.44–1.55 (m, 2H,
MeCH2(CH2)2), 1.60–1.90 (m, 2H, MeCH2), 1.70–1.80 (m,
Yellow oil, yield: 43%. Eluent for TLC: ethyl acetate:hexane
2H, MeCH2CH2CH2), 1.96 (s, 3H, Me-‘¼), 2.40–2.63 (m,
¼ 1:2, Rf 0.75; IR (neat, cmꢀ1): 1021 (C-O-P), 1254 (P ¼ O),
2H, Me(CH2)2CH2), 3.87 (d, J ¼ 10.6 Hz, 6H, (MeO)2),
1441, 1492 (Ph), 1583 (C ¼ C), 1730 (C ¼ O). 1H NMR
7.15–7.47 (m, 5H, Ph). 13C NMR (150.9 MHz): d ¼ 10.7
(600.1 MHz): d ¼ 0.92 (t, J ¼ 6.9 Hz, 6H, MeCH2), 1.20 (t,
(CH3), 14.4 (CH3), 19.9 (CH2), 20.1 (J ¼ 4.7 Hz, CH3), 21.7
J ¼ 7.1 Hz, 3H, MeCH2O), 1.65 (s, 3H, MeC), 1.80–2.01 (m,
(CH2), 22.4 (J ¼ 5.0 Hz, CH2), 28.9 (J ¼ 7.8 Hz, CH2), 33.6
4H, MeCH2), 3.69 (d, J ¼ 11.4 Hz, 3H, MeO), 4.07–4.11 (m,
(J ¼ 5.8 Hz, CH2), 50.3 (J ¼ 5.0 Hz, C), 53.7 (J ¼ 15.2 Hz,
CH3), 84.9 (J ¼ 124.9 Hz, C), 125.9 (C), 127.1 (CH), 129.4
(CH), 129.7 (J ¼ 14.6 Hz, C), 134.8 (CH), 140.1 (J ¼ 8.0 Hz,
C), 175.5 (J ¼ 7.9 Hz, C). 31P NMR (242.9 MHz): d ¼ 24.8.
HRMS (ESI): m/z calcd for C22H34O5PS [M þ H]þ 441.5421,
found 441.5445. Anal. Calcd for C22H33O5PS: C 59.98, H
7.55. Found: C 59.92, H 7.62%.
2H, MeCH2O), 7.16–7.79 (m, 10H, Ph). 13C NMR
(150.9 MHz): d ¼ 10.3 (CH3), 14.4 (CH3), 20.4 (J ¼ 5.1 Hz,
CH2), 22.5 (J ¼ 5.0 Hz, CH2), 25.4 (J ¼ 7.8 Hz, CH3), 53.2
(J ¼ 15.0 Hz, CH3), 53.7 (J ¼ 7.7 Hz, C), 61.3 (CH2), 93.2
(J ¼ 10.1 Hz, C), 125.4 (J ¼ 7.7 Hz, CH), 125.9 (CH), 127.0
(CH), 128.9 (J ¼ 100.1 Hz, C), 129.1 (J ¼ 4.6 Hz, CH), 129.9
(CH), 130.0 (J ¼ 9.7 Hz, C), 130.2 (CH), 139.1 (J ¼ 5.0 Hz,
C), 161.0 (J ¼ 4.7 Hz, C), 177.3 (J ¼ 5.0 Hz, C). 31P NMR
(242.9 MHz): d ¼ 27.7. HRMS (ESI): m/z calcd for
C25H32O5PS [M þ H]þ 475.5583, found 475.5597. Anal.
Calcd for C25H31O5PS: C 63.27, H 6.58. Found: C 63.19,
H 6.66%.
Ethyl 2-(4-bromo-2-methoxy-5-methyl-2-oxo-3-phenyl-
2,5-dihydro-1,2-oxaphosphol-5-yl)-2-ethyl-butanoate 2k
Pale yellow oil, yield: 46%. Eluent for TLC: ethyl acetate:hex-
ane ¼ 1:2, Rf 0.74; IR (neat, cmꢀ1): 1019 (C-O-P), 1257
1
(P ¼ O), 1444, 1491 (Ph), 1586 (C ¼ C), 1728 (C ¼ O). H
Dimethyl (5,5-diethyl-4-methyl-6-oxo-2-phenyl-3-
phenylsulfenyl-5,6-dihydro-2H-pyran-2-yl)-
phosphonate 3l
NMR (600.1 MHz): d ¼ 0.92 (t, J ¼ 6.8 Hz, 6H, MeCH2), 1.22
(t, J ¼ 7.0 Hz, 3H, MeCH2O), 1.74 (s, 3H, MeC), 1.63–1.80
(m, 4H, MeCH2), 3.71 (d, J ¼ 11.4 Hz, 3H, MeO), 4.00–4.09
(m, 2H, MeCH2O), 7.38–7.88 (m, 5H, Ph). 13C NMR
(150.9 MHz): d ¼ 10.2 (CH3), 13.8 (CH3), 19.1 (J ¼ 4.6 Hz,
CH2), 21.1 (J ¼ 4.6 Hz, CH2), 22.6 (J ¼ 8.1 Hz, CH3), 51.4
(J ¼ 8.0 Hz, C), 52.9 (J ¼ 15.0 Hz, CH3), 61.2 (CH2), 95.1
(J ¼ 9.9 Hz, C), 125.2 (J ¼ 9.4 Hz, CH), 128.7 (J ¼ 153.9 Hz,
C), 129.6 (J ¼ 4.8 Hz, C), 130.4 (J ¼ 5.0 Hz, CH), 130.8 (CH),
140.5 (J ¼ 48.8 Hz, C), 174.9 (J ¼ 4.6 Hz, C). 31P NMR
(242.9 MHz): d ¼ 27.0. HRMS (ESI): m/z calcd for
C19H27BrO5P [M þ H]þ 446.2924, found 446.2908. Anal.
Calcd for C19H26BrO5P: C 51.25, H 5.89. Found: C 51.31,
H 5.93%.
Yellow oil, yield: 29%. Eluent for TLC: ethyl acetate:hexane
¼ 1:2, Rf 0.41; IR (neat, cmꢀ1): 1119 (C–O–C), 1266
1
(P ¼ O), 1439, 1490 (Ph), 1622 (C ¼ C), 1752 (C ¼ O). H
NMR (600.1 MHz): d ¼ 0.80 (t, J ¼ 7.5 Hz, 6H, MeCH2),
1.60–1.86 (m, 2H, MeCH2), 1.98 (s, 3H, Me-‘¼), 3.89 (d,
J ¼ 10.4 Hz, 6H, MeO), 7.13–7.75 (m, 10H, Ph). 13C NMR
(150.9 MHz): d ¼ 11.0 (CH3), 19.7 (CH2), 20.7 (J ¼ 4.7 Hz,
CH3), 21.9 (CH), 49.9 (J ¼ 4.8 Hz, C), 54.1 (J ¼ 5.0 Hz, CH3),
84.9 (J ¼ 126.6 Hz, C), 125.3 (CH), 126.7 (J ¼ 4.6 Hz, CH),
127.0 (CH), 127.5 (J ¼ 14.6 Hz, C), 129.9 (J ¼ 7.8 Hz, CH),
130.0 (CH), 131.3 (CH), 135.6 (J ¼ 5.0 Hz, C), 135.7
(J ¼ 9.9 Hz, C), 141.7 (J ¼ 9.8 Hz, C), 174.3 (J ¼ 4.8 Hz, C).
31P NMR (242.9 MHz): d ¼ 25.5. HRMS (ESI): m/z calcd for
C24H30O5PS [M þ H]þ 461.5318, found 461.5326. Anal.
Calcd for C24H29O5PS: C 62.59, H 6.35. Found: C 62.64,
H 6.42%.
Dimethyl (3-bromo-5,5-diethyl-4-methyl-6-oxo-2-phenyl-
5,6-dihydro-2H-pyran-2-yl)-phosphonate 3k
Yellow oil, yield: 30%. Eluent for TLC: ethyl acetate:hexane
¼ 1:2, Rf 0.43; IR (neat, cmꢀ1): 1122 (C–O–C), 1263
1
(P ¼ O), 1440, 1494 (Ph), 1618 (C ¼ C), 1750 (C ¼ O). H
Procedure for the synthesis of the (6E)- and (6Z)-
benzylidene-3,3,4-trimethyl-5-methylsulfenyl-3,6-
dihydro-2H-pyran-2-one 4 by the Horner-Wadsworth-
Emmons reaction of the dimethyl (4,5,5-trimethyl-3-
methylsulfenyl-6-oxo-5,6-dihydro-2H-pyran-2-yl)-
phosphonate 3a
NMR (600.1 MHz): d ¼ 0.79 (t, J ¼ 7.5 Hz, 6H, MeCH2),
1.40–1.69 (m, 2H, MeCH2), 2.09 (s, 3H, Me-‘¼), 3.81 (d,
J ¼ 10.5 Hz, 6H, MeO), 7.47–7.85 (m, 5H, Ph). 13C NMR
(150.9 MHz): d ¼ 10.7 (CH3), 16.9 (CH3), 18.3 (CH2), 20.4
(CH2), 48.6 (J ¼ 4.6 Hz, C), 53.9 (J ¼ 5.1 Hz, CH3), 86.6
(J ¼ 126.8 Hz, C), 114.8 (J ¼ 48.7 Hz, C), 122.9 (J ¼ 7.8 Hz,
CH), 127.9 (J ¼ 5.0 Hz, CH), 131.9 (CH), 135.3 (J ¼ 10.1 Hz,
To a suspension of sodium hydride (NaH) (60% dispersion
C), 143.7 (J ¼ 8.0 Hz, C), 171.4 (J ¼ 5.9 Hz, C). 31P NMR in mineral oil, 2.2 eq. 1.8 mmol) in THF (3 mL) was added a

10
H. H. HASANOV ET AL.
solution of the dimethyl 3a (460 mg, 0.8 mmol) in dry THF
(3 mL) at room temperature. The reaction mixture was
stirred at the same temperature for 30 min. After the add-
Acknowledgments
Dr. Hasanov thanks the Bulgarian Ministry of Education and Science
under the National Program for Research “Young Scientists and
ition of a solution of 1.4 eq. PhCHO (1.1 mmol) in 6 mL Postdoctoral Students” for support of this work. Special thanks to
Assoc. Prof. Dr. Petar Petrov from Department of Organic Chemistry
THF to the mixture, the reaction mixture was heated at
and Pharmacognosy, Faculty of Chemistry and Pharmacy, St. Kliment
40–50 ꢁC for 120 min (reaction was monitored by TLC).
Ohridski University of Sofia for the help in the experiment on the
After that the mixture was quenched with 2 N HCI,
Horner-Wadsworth-Emmons reaction.
extracted with ether, washed with saturated NaCl, and dried
over anhydrous sodium sulfate. After evaporation of the
solvent, the residue was purified by column chromatography
Funding
on a silica gel using hexane: ethylacetate (4:1) as an eluent
to give the pure product 4, which had the follow-
ing properties.
Financial support by the Research Fund of the Konstantin Preslavsky
University of Shumen under Projects Nos. RD-08-94/2019 and RD-08-
117/2020 is gratefully acknowledged.
ORCID
(6E)- and (6Z)-benzylidene-3,3,4-trimethyl-5-
methylsulfenyl-3,6-dihydro-2H-pyran-2-one 4
Valerij Ch. Christov
http://orcid.org/0000-0002-1609-2320
Pale yellow oil, yield: 63%. E:Z ¼ 6.4:1 (87:13). Eluent for
TLC: hexane:ethyl acetate ¼ 4:1, Rf 0.49; IR (neat, cmꢀ1):
1112 (C–O–C), 1443, 1487 (Ph), 1602, 1625 (C ¼ C), 1748
References
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(C ¼ O). H NMR (600.1 MHz): d ¼ 1.38 (s, 3H, Me2C), 1.59
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Conclusions
In conclusion, the reaction of the 5-(dimethoxyphosphoryl)-
alka-3,4-dienoates with electrophilic reagents occur via com-
petitive 5-endo-trig and 6-endo-trig cyclization giving mix-
tures of the 2,5-dihydro-1,2-oxaphosphol-2-ones and the
5,6-dihydro-2H-pyran-6-ones because of the participation of
the phosphonate and carboxylate neighboring group in the
cyclizations. Due to the easy availability of the starting mate-
rials, the convenient operation and mild conditions, the
good yields and the usefulness of the heterocyclic com-
pounds prepared, the cyclization reactions may show poten-
tial and will be useful in organic synthesis as well as in their
application in target-oriented synthesis. Further investigation
on the chemistry of other bifunctionalized allenes for the
synthesis of different heterocyclic systems is being inten-
sively carried out in our laboratory. Moreover, results of an
initial investigation of the biological activity of the com-
pounds prepared were encouraging, and the antibacterial
and antifungal activities of selected compounds as well as
potential precursors of effective anticancer drugs are now
under investigation in our university and the results will be
reported in due course.
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