Te(II)-induced heterocyclization of 1,2-alkadienephosphonates

Article abstract of DOI:10.3906/kim-1210-24

The reactivity of some 1,2-alkadienephosphonates towards phenyltelluryl halides was investigated. A plausible mechanism of the reaction is discussed. TUeBITAK.

Full text of DOI:10.3906/kim-1210-24

Turk J Chem
Turkish Journal of Chemistry
(2014) 38: 430 – 435
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http://journals.tubitak.gov.tr/chem/
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⃝ TUBITAK
doi:10.3906/kim-1210-24
Research Article
Te(II)-induced heterocyclization of 1,2-alkadienephosphonates
Dobromir Dimitrov ENCHEV∗
Department of Organic Chemistry and Technology, Faculty of Natural Sciences, “K. Preslavsky” University,
Shumen, Bulgaria
Received: 12.10.2012
•
Accepted: 26.10.2013
•
Published Online: 14.04.2014
•
Printed: 12.05.2014
Abstract: The reactivity of some 1,2-alkadienephosphonates towards phenyltelluryl halides was investigated. A plausible
mechanism of the reaction is discussed.
Key words: 1,2-Alkadienephosphonates, electrophilic addition, phosphorus heterocycles
1. Introduction
The applications of organophosphorus compounds as pharmaceutical, agricultural, and chemical agents are well
documented.1,2 Among them, oxaphosphole derivatives, which have structures similar to those of phospho-
sugars, have received particular interest.3,4 Consequently, many attempts for their synthesis have been made.
One of the easiest and most fruitful methods for the synthesis of these derivatives is electrophile-induced
heterocyclization of 1,2-alkadienephosphonates.5
Keeping in mind that the scope of applications of organotellurides has been known for years be-
cause of their ready transformation to other compounds via reactions with organometallic reagents,6−10 here
we wish to report the results of our study on the electrophilic addition of organotellurides to some 1,2-
alkadienephosphonates.
2. Experimental
2.1. Analytical methods
The 1 H NMR and 31 P NMR spectra were measured at normal probe temperature on a Bruker Avance DRX
250 MHz spectrometer using tetramethylsilane (TMS) (1 H) and 85% H3 PO4
(
31 P) as internal references in
CDCl3 solution.
Chemical shifts are given in parts per million (ppm) and are downfield from the internal standard. The
infrared (IR) spectra were run on a Shimadzu IRAffinity-1 spectrophotometer. Elemental analyses were carried
out by the University of Shumen Microanalytical Service Laboratory. Phenyltelluryl chloride was synthesized
as described previously.11−15
Compounds 1, 3, 4, 7, and 9 were synthesized according to the literature.16−18
The solvents were purified by standard methods. All reactions were carried out in oven-dried glassware
under an argon atmosphere and with exclusion of moisture. All compounds were checked for their purity on
TLC plates. Melting points are uncorrected.
∗Correspondence: enchev@shu-bg.net
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2.2. Synthesis of 2-alkoxy-5-alkyl-5-alkyl-4-phenyltellanyl-5H -[1,2]-oxaphosphole 2-oxides and of
2-alkoxy-4-phenyltellanyl-1-oxa-2-phospha-[4,5]-dec-3-ene 2-oxide 2a–d
2.2.1. General procedure
To a solution of 1 (5 mmol) in methylene chloride (10 mL) was added a solution of phenyltelluryl chloride
(1.24 g, 5.2 mmol) in 5 mL of methylene chloride under stirring and cooling (–10 to –12 ◦ C). After 1 h of
stirring at the same conditions, the reaction mixture stood overnight, and was concentrated and recrystallized
in heptane/benzene (2:1).
2a, cryst. colorless needles; 1.59 g (87%), mp ◦ C (147–149), IR (KBr) νmax /cm−1 2980, 2677, 1540,
1235, 960 cm−1 1 H NMR (250 MHz, CDCl3) ppm: 7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H), 6.46 (d, JHP 26.0
;
Hz, 1H), 3.70 (d, JHP 12.2 Hz, 3H), 1.59 (s, 3H), 1.55 (s, 3H). 31 P NMR (250 MHz, CDCl3) ppm: 33.09; Anal.,
Calcd. for C12 H15 O3 PTe (Mr = 365.81): P 8.47; Found P 8.43; 2b, cryst. colorless needles; 1.38 g (73%), mp
◦ C (150–152), IR (KBr) νmax /cm−1 2980, 2677, 1580, 1235, 1000 cm−1 1 H NMR (250 MHz, CDCl3) ppm:
;
7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H), 6.49 (d, JHP 26.1 Hz, 1H), 4.17 (m, JHP 10.0 Hz, 2H), 1.36 (t, JHH 7.0
Hz, 3H) 1.52 (s, 3H), 1.57 (s, 3H). 31 P NMR (250 MHz, CDCl3) ppm: 32.0; Anal., Calcd. for C13 H17 O3 PTe
(Mr = 379.836): P 8.15; Found P 8.11; 2c, cryst. colorless needles; 1.46 g (77%), mp ◦ C (149–150); IR (KBr)
νmax /cm−1 2980, 2677, 1545, 1235, 980 cm−1 ; 1 H NMR (250 MHz, CDCl3) ppm: 7.86–7.87 (m, 2H), 7.30–7.51
(m, 3H), 6.55, 6.59* (d, JHP 26.0 Hz, 1H), 3.80, 3.82* (d, JHP 11.6 Hz, 2H), 1.51, 154* (s, 3H), 1.89 (m, 2H),
0.92 (t, 3H). 31 P NMR (250 MHz, CDCl3) ppm: 33.12; Anal., Calcd. for C13 H17 O3 PTe (Mr = 379.836):
P 8.15; Found P 8.10; (*Additional signals for diastereomers); 2d, cryst. colorless needles; 1.44 g (71%), mp
◦ C (155–157); IR (KBr) νmax /cm−1 2980, 2677, 1540, 1235, 990 cm−1 1 H NMR (250 MHz, CDCl3) ppm:
;
7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H), 6.42 (d, JHP 25.8 Hz, 1H), 3.80 (d, JHP 11.2 Hz, 2H), 1.68 (m, 10H).
31 P NMR (250 MHz, CDCl3) ppm: 33.23; Anal., Calcd. for C15 H19 O3 PTe (Mr = 405.872): P 7.63; Found
P 7.60.
2.3. Synthesis of (5-alkyl-5-alkyl-2-oxo-4-phenyltellanyl-2,5-dihydro-2λ5 -[1,2]-oxaphosphol-2-yl)
dialkylamines 5a-c and of dialkyl-(2-oxo-4-phenyltellanyl-1-oxa-2λ5 phospha-spiro[4,5]-dec-3-
ene 2-yl)amines 6a–c
2.3.1. General procedure
To a solution of 3 or 4 (5 mmol) in methylene chloride (10 mL) was added a solution of phenyltelluryl chloride
(1.24 g, 5.2 mmol) in 5 mL of methylene chloride under stirring and cooling (–10 to –12 ◦ C). After 1 h of
stirring at the same conditions, the reaction mixture stood overnight, and was concentrated and recrystallized
in heptane/benzene (2:1).
5a, cryst. colorless needles; 1.67 g (82%), mp ◦ C (147–149); IR (KBr) νmax /cm−1 2980, 2677, 1589,
1225, 1004 cm−1 1 H NMR (250 MHz, CDCl3) ppm: 7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H), 5.88 (d, JHP 24.2
;
Hz, 1H), 1.40 (s, 3H), 1.58 (s, 3H), 1.00 (t, JHH 7.0 Hz, 3H), 2.93 (m, JHP 13.6 Hz, 2H). 31 P NMR (250 MHz,
CDCl3) ppm: 28.3; Anal., Calcd. for C15 H22 O2 NPTe (Mr = 406.896): P 7.61, N 3.44; Found P 7.59, N 3.41;
5b, cryst. colorless needles; 1.62 g (77%), mp ◦ C (149–150); IR (KBr) νmax /cm−1 2980, 2677, 1590, 1235,
980 cm−1 1 H NMR (250 MHz, CDCl3) ppm: 7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H), 6.55, 6.59* (d, JHP 22.4
;
Hz, 1H), 1.51, 154* (s, 3H), 1.89 (m, 2H), 0.92 (t, 3H), 1.04 (t, JHH 7.0 Hz, 3H), 3.00 (m, JHP 12.1 Hz, 2H).
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ENCHEV/Turk J Chem
31 P NMR (250 MHz, CDCl3) ppm: 27.9; Anal., Calcd. for C16 H24 O2 NPTe (Mr = 420.922): P 7.36, N 3.32;
Found P 7.33, N 3.29 (*Additional signals for diastereomers); 5c, cryst. colorless needles; 1.81 g (81%), mp
◦ C (155–157); IR (KBr) νmax /cm−1 2980, 2677, 1588, 1225, 1000 cm−1 1 H NMR (250 MHz, CDCl3) ppm:
;
7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H), 5.87 (d, JHP 23.5 Hz, 1H), 1.68 (m, 10H), 0.98 (t, JHH 7.0 Hz, 3H),
2.92 (m, JHP 12.4 Hz, 2H). 31 P NMR (250 MHz, CDCl3) ppm: 32.3; Anal., Calcd. for C18 H26 O2 NPTe (Mr
= 446.958): P 6.93, N 3.13; Found P 6.90, N 3.10.
6a, cryst. colorless needles; 1.89 g (87%), mp ◦ C (147–149); IR (KBr) νmax /cm−1 2980, 2677, 1580,
1230, 1000 cm−1 1 H NMR (250 MHz, CDCl3) ppm: 7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H), 6.08 (d, JHP 24.2
;
Hz, 1H), 1.40 (s, 3H), 1.58 (s, 3H), 1.24 (ss, 6H), 2.93 (m, 1H). 31 P NMR (250 MHz, CDCl3) ppm: 28.3; Anal.,
Calcd. for C17 H26 O2 NPTe (Mr = 434.948): P 7.12, N 3.22; Found P 7.10, N 3.19; 6b, cryst. colorless needles;
1.66 g (74%), mp ◦ C (147–149); IR (KBr) νmax /cm−1 2980, 2677, 1597, 1235, 900 cm−1 1 H NMR (250 MHz,
;
CDCl3) ppm: 7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H), 6.55, 6.59* (d, JHP 26.0 Hz, 1H), 1.51, 154* (s, 3H), 1.89
(m, 2H), 0.92 (t, 3H), 1.24 (ss, 6H), 2.93 (m, 1H). 31 P NMR (250 MHz, CDCl3) ppm: 28.3; Anal., Calcd. for
C18 H28 O2 NPTe (Mr = 450.974): P 6.89, N 3.12; Found P 6.86, N 3.10; 6c, cryst. colorless needles; 1.99 g
(84%), mp ◦ C (147–149); IR (KBr) νmax /cm−1 2980, 2677, 1590, 1228, 1004 cm−1
;
1 H NMR (250 MHz,
CDCl3) ppm: 7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H), 5.87 (d, JHP 23.5 Hz, 1H), 1.68 (m, 10H), 1.24 (s, 6H),
2.93 (m, 1H); 31 P NMR (250 MHz, CDCl3) ppm: 28.3; Anal., Calcd. for C20 H30 O2 NPTe (Mr = 475.01): P
6.52, N 2.95; Found P 6.50, N 2.91.
2.4. Synthesis of (5-alkyl-5-alkyl-2-oxo-4-phenyltellanyl-2,5-dihydro-2λ5 -[1,2]-oxaphosphol-2-yl)
alkylamines 8a,b and of alkyl-(2-oxo-4-phenyltellanyl-1-oxa-2λ5 phospha-spiro[4,5]-dec-3-ene
2-yl)amine 8c
2.4.1. General procedure
To a solution of 7 (5 mmol) in methylene chloride (10 mL) was added a solution of phenyltelluryl chloride
(1.24 g, 5.2 mmol) in 5 mL of the same solvent under stirring and cooling (–10 to –12 ◦ C). After 1 h of
stirring at the same conditions, the reaction mixture stood overnight, and was concentrated and recrystallized
in heptane/benzene (2:1).
8a, cryst. colorless needles; 1.61 g (82%), mp ◦ C (147–149); IR (KBr) νmax /cm−1 2980, 2677, 1580,
1245, 1004 cm−1 1 H NMR (250 MHz, CDCl3) ppm: 7.56–7.46 (m, 2H); 7.29–7.23 (m, 3H); 5.35 (d, JHP
;
27.75 Hz, 1H); 2.54 (m, 2H); 1.46 (s, 3H); 1.51 (s, 3H); 2.00 (d, JHP 10.00 Hz, 1H); 1.28–1.19 (m, 2H); 0.91 (t,
3H); 31 P NMR (250 MHz, CDCl3) ppm: 29.0; Anal., Calcd. for C14 H20 O2 NPTe (Mr = 392.87): P 7.88, N
3.56; Found P 7.83, N 3.51; 8b, cryst. colorless needles; 1.52 g (75%), mp ◦ C (147–149); IR (KBr) νmax /cm−1
2980, 2677, 1589, 1230, 960 cm−1 1 H NMR (250 MHz, CDCl3) ppm: 7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H),
;
6.55, 6.59* (d, JHP 26.0 Hz, 1H), 1.51, 154* (s, 3H), 1.89 (m, 2H), 0.92 (t, 3H), 2.54 (m, 2H), 2.00 (d, JHP
10.00 Hz, 1H); 1.28–1.19 (m, 2H); 0.91 (t, 3H). 31 P NMR (250 MHz, CDCl3) ppm: 28.3; Anal., Calcd. for
C15 H22 O2 NPTe (Mr = 406.896): P 7.61, N 3.44; Found P 7.58, N 3.40 (*Additional signals for diastereomers);
8c, cryst. colorless needles; 1.71 g (79%), mp ◦ C (147–149); IR (KBr) νmax /cm−1 2980, 2677, 1587, 1253,
1004 cm−1
;
1 H NMR (250 MHz, CDCl3) ppm: 7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H), 5.87 (d, JHP 23.5 Hz,
1H), 1.68 (m, 10H), 2.54 (m, 2H), 2.00 (d, JHP 10.00 Hz, 1H); 1.28–1.19 (m, 2H); 0.91 (t, 3H); 31 P NMR (250
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ENCHEV/Turk J Chem
MHz, CDCl3) ppm: 28.3; Anal., Calcd. for C17 H24 O2 NPTe (Mr = 432.932): P 7.15, N 3.23; Found P 7.11,
N 3.20.
2.5. Synthesis of 4-(5-alkyl-5-alkyl-2-oxo-4-phenyltellanyl-2,5-dihydro-2λ5 -[1,2]-oxaphosphol-2-yl)
morpholines 10a,b and of 4-(2-oxo-4-phenyltellanyl-1-oxa-2λ5 phospha-spiro[4,5]-dec-3-ene 2-
yl)morpholine 10c
2.5.1. General procedure
To a solution of 9 (5 mmol) in methylene chloride (10 mL) was added a solution of phenyltelluryl chloride
(1.24 g, 5.2 mmol) in 5 mL of methylene chloride under stirring and cooling (–10 to –12 ◦ C). After 1 h of
stirring at the same conditions, the reaction mixture stood overnight, and was concentrated and recrystallized
in heptane/benzene (2:1).
10a, cryst. colorless needles; 1.30 g (62%), mp ◦ C (147–149); IR (KBr) νmax /cm−1 2980, 2677, 1589,
1225, 1004 cm−1 1 H NMR (250 MHz, CDCl3) ppm: 7.56–7.46 (m, 2H); 7.29–7.23 (m, 3H); 6.34 (d, JHP
;
23.0 Hz, 1H); 1.46 (s, 3H); 1.51 (s, 3H), 2.87, 3.76 (m, 8H); 31 P NMR (250 MHz, CDCl3) ppm: 33.42; Anal.,
Calcd. for C15 H20 O3 NPTe (Mr = 420.88): P 7.36, N 3.33; Found P 7.32, N 3.30; 10b, cryst. colorless
needles; 1.45 g (67%), mp ◦ C (147–149); IR (KBr) νmax /cm−1 2980, 2677, 1595, 1225, 1000 cm−1 1 H NMR
;
(250 MHz, CDCl3) ppm: 7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H), 6.55, 6.59* (d, JHP 26.0 Hz, 1H), 1.51, 154*
(s, 3H), 1.89 (m, 2H), 0.92 (t, 3H), 2.87, 3.76 (m, 8H). 31 P NMR (250 MHz, CDCl3) ppm: 34.12; Anal.,
Calcd. for C16 H22 O3 NPTe (Mr = 434.906): P 7.12, N 3.22; Found P 7.09, N 3.18 (*Additional signals for
diastereomers); 10c, cryst. colorless needles; 1.40 g (61%), mp ◦ C (147–149); IR (KBr) νmax /cm−1 2980,
2677, 1589, 1273, 998 cm−1 1 H NMR (250 MHz, CDCl3) ppm: 7.86–7.87 (m, 2H), 7.30–7.51 (m, 3H), 5.87
;
(d, JHP 23.5 Hz, 1H), 1.68 (m, 10H), 2.87, 3.76 (m, 8H). 31 P NMR (250 MHz, CDCl3) ppm: 33.22; Anal.,
Calcd. for C18 H24 O3 NPTe (Mr = 460.942): P 6.72, N 3.04; Found P 6.69, N 2.99.
3. Results and discussion
In our first report on this subject19 we demonstrated that the reaction of dialkyl esters of 1,2-alkadienephosphonic
acids with phenyltelluryl chloride leads to the formation of 4-phenyltelluro-2,5-dihydro-1,2-oxaphosphole 2-oxide
derivatives (Figure 1).
TePh
R2
R2
PhTeCl
O
P
R1
-RCl
R1
O
(RO)2P
RO
O
1a-d
2a-d
1
2
1
2
1
2a,R,R ,R = Me,2b, R = Et, R1= R2= Me,2c,R = R = Me, R2= Et,2d, R = Me, R +R = cyclohexyl
Figure 1. Reaction of dialkyl esters of 1,2-alkadienephosphonic acids with phenyltelluryl chloride.
In 2007, Yuan and co-workers reported the same results using different synthetic conditions.20
Continuing our investigations on this reaction, we studied the reaction of N,N-dialkylamido-O-alkyl-1,2-
alkadienephosphonates previously described by us,17 with the same reagent, and established that in all cases
with good yields the oxaphosphole derivatives 5a–c and 6a–c were obtained (Figure 2):
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ENCHEV/Turk J Chem
TePh
R2
R2
R1
PhTeCl
O
RO
P
-RCl
R1
P
O
R32N
R32N
O
3a-d,4a-d
5a-c,6a-c
5a,R1= R2= Me, R3= Et;5b, R1= Me, R2= Et, R3= Et;5c,R1+R2= cyclohexyl, R3 =Et
6a,R1= R2= Me, R3= iPr;6b,R1= Me, R2= Et, R3= iPr;6c,R1+R2=cyclohexyl, R3= iPr
R = Me
Figure 2. Reaction of N,N-dialkylamido-O-alkyl-1,2-alkadienephosphonates with phenyltelluryl chloride.
The results reported above encourage us to investigate the reactivity of N-alkylamido-O-alkyl-1,2-
alkadienephosphonates as well as the reactivity of N-morpholino-O-alkyl-1,2-alkadienephosphonates also pre-
viously reported by us.18 We expected both substrates to react with phenyltelluryl chloride with formation of
the corresponding 2,5-dihydro-1,2-oxaphosphole 2-oxide derivatives (Figure 3).
TePh
R2
R2
PhTeCl
O
RO
P
-RCl
R1
R1
P
O
R3N
H
R3N
H
O
7a-d
8a-c
TePh
R2
R1
R2
R1
PhTeCl
-RCl
O
N
RO
N
P
P
O
O
O
9a-d
O
10a-c
O
8a,R1= R2= Me, R3= Pr;8b, R1= Me, R2=Rt, R3= Pr;8c,R1+R2= cyclohexyl, R3= Pr
10a,R1= R2= Me,10b,R1= Me, R2= Et;10c,R1+R2=cyclohexyl
R = Me
Figure 3. Reaction of N-alkylamido-O-alkyl-1,2-alkadienephosphonates and of N-morpholino-O-alkyl-1,2-alkadienephosp-
honates with phenyltelluryl chloride.
All the synthetic results obtained as well as our previous experience5 give us reason to suggest the
following plausible mechanism of the telluro-induced cyclization of 1,2-alkadienephosphonates (Figure 4):
The attack of the reagent affecting the C2 –C3 double bond of the allenephosphonate system leads to the
formation of “onium” intermediate A, which is in equilibrium with carbocation B. The latter can be transformed
to quaziphosphonium intermediate C, which undergoes dealkylation (Michalis–Arbuzov reaction – second stage)
to afford the final 2,5-dihydro-1,2-oxaphosphole 2-oxide derivatives 2, 5, 6, 8, and 10.
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ENCHEV/Turk J Chem
Cl
Ph
R2
R1
TePh
R2
PhTeCl
Te
R2
RO
P
RO
Y
RO
Cl
P
P
R1
R1
Y
O
O
Y
O
A
B
TePh
TePh
R2
R1
R
O
R2
R1
O
P
P
O
Y
-RCl
Cl
O
Y
C
Figure 4. Plausible mechanism of the telluro-induced cyclization of 1,2-alkadienephosphonates.
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