Introduction of a novel reaction of triacetylmethane: One-pot synthesis of dialkyl-2-(3,1-hydroxyethylidene-2,4-pentanedione-3-yl)-3-(triphenyl phosphoranylidene)-butanedioate

Article abstract of DOI:10.1080/10426500210676

Protonation of reactive 1:1 intermediates produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylate by 3-(1-hydroxyethylidene)-2,4-pentanedione leads to vinyl phosphonium salts, which undergo Michael addition with the conjugate base of CH-acid to produce the title compounds in high yield.

Full text of DOI:10.1080/10426500210676

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Phosphorus, Sulfur, and Silicon and the Related
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Introduction of a Novel Reaction of Triacetylmethane:
One-Pot Synthesis of Dialkyl-2-(3,1-
hydroxyethylidene-2,4-pentanedione-3-yl)-3-
(triphenylphosphoranylidene)-butanedioate
Ahmad Shaabani a , Ayoob Bazgir a , Mohammad Bagher Teimouri a & Hamid Reza Bijanzadeh
b
a Department of Chemistry , Shahid Beheshti University , Tehran, Iran
b Department of Chemistry , Tarbiat Modarres University , Tehran, Iran
Published online: 27 Oct 2010.
To cite this article: Ahmad Shaabani , Ayoob Bazgir , Mohammad Bagher Teimouri & Hamid Reza Bijanzadeh (2002)
Introduction of a Novel Reaction of Triacetylmethane: One-Pot Synthesis of Dialkyl-2-(3,1-hydroxyethylidene-2,4-
pentanedione-3-yl)-3-(triphenylphosphoranylidene)-butanedioate, Phosphorus, Sulfur, and Silicon and the Related Elements,
177:4, 833-839, DOI: 10.1080/10426500210676
To link to this article: http://dx.doi.org/10.1080/10426500210676
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Phosphorus, Sulfur and Silicon, 2002, Vol. 177:833–839
C
Copyright 2002 Taylor & Francis
1042-6507/02 $12.00 + .00
INTRODUCTION OF A NOVEL REACTION OF
TRIACETYLMETHANE: ONE-POT SYNTHESIS OF
DIALKYL-2-(3,1-HYDROXYETHYLIDENE-2,4-
PENTANEDIONE-3-YL)-3-
(TRIPHENYLPHOSPHORANYLIDENE)-
BUTANEDIOATE
Ahmad Shaabani,a Ayoob Bazgir,a Mohammad Bagher
Teimouri,a and Hamid Reza Bijanzadehb
Department of Chemistry, Shahid Beheshti University, Tehran,
Irana and Department of Chemistry, Tarbiat Modarres
University, Tehran, Iranb
(Received March 5, 2001; accepted October 11, 2001)
Protonation of reactive 1:1 intermediates produced in the reaction be-
tween triphenylphosphine and dialkyl acetylenedicarboxylate by 3-(1-
hydroxyethylidene)-2,4-pentanedione leads to vinyl phosphonium salts,
which undergo Michael addition with the conjugate base of CH-acid to
produce the title compounds in high yield.
Keywords: Acetylenic esters; dynamic NMR; triacetylmethane;
triphenylphosphine
We have recently described1 the synthesis of dialkyl-formyl-2H-pyran-
2,3-dicarboxylate (1) from the reaction of triformylmethane with di-
alkyl acetylenedicarboxylates and triphenylphosphine. With the pur-
pose of preparation of 2H-pyran ring with highly functionalized groups
such as (2), we performed the reaction of 3-(1-hydroxyethylidene)-
2,4-pentanedione (3) with triphenylphosphine and dialkyl acetylenedi-
carboxylates (4). This reaction did not afford the corresponding
4,6-dimethyl-2H-pyran-2,3-dicarboxylates (2), but as an unusual be-
havior of compound (3) yielded compounds 6a–c which were as two
rotamers 6-s-cis and 6-s-trans in an about 1:2 ratio in high yields.
We gratefully acknowledge financial support from the Research Council of Shahid
Beheshti University.
Address correspondence to A. Shaabani, Department of Chemistry, Shahid Beheshti
University, PO Box 19396-4716, Tehran, Iran. E-mail: a-shaabani@cc-sbu.ac.ir
833

834
A. Shaabani et al.
On the basis of the well established chemistry of trivalent phospho-
rus nucleophiles2 6 it is reasonable to assume that compound (5) results
from the initial addition of triphenylphosphine to the acetylenic ester
and a concomitant protonation of the 1:1 adduct by compound (3). Then,
the positively charged ion is attacked by the enolate anion of the CH
11
acid to form compound (5).7
Compound (5) is converted to the com-
pounds 6a–c probably by extraction of ketene following deprotonation
by triphenylphosphine.
SCHEME 1
All the compounds are stable solid powders whose structure is
1
fully supported by elemental analyses and IR, high-field H, 13C, and
31P NMR and mass spectrometry data. The mass spectra of these
compounds displayed molecular ion peaks at m/z of 504, 532, and
588 respectively. Initial fragmentation involved the loss of ester moi-
1
eties. The H NMR spectra of compounds 6a, 6b, and 6c showed the
s-trans rotamer is the major (about 68%) and s-cis rotamer is the minor
(about 32%).

Triacetylmethane
835
The 1H NMR spectra of 6a exhibited two sets of sharp lines at
1.41 and 0.96 for s-trans rotamer and 1.39 and 1.49 for s-cis rotamer
arising from tert-butyl protons. The shift at 0.96 of the tert-butyl group
of the s-trans rotamer is shielded because of anisotropy of phenyl groups
1
of triphenylphosphine. The H NMR spectra of rotamers 6a displayed
signals for CH protons of CHCO2R which appears as two sets of dou-
blet or doublet at 3.17 and 3.12 (3JPH 17.40 Hz and 3JHH 10.50 Hz) for
s-trans and s-cis rotamers, along with a characteristic two sets of dou-
blet of CH(CO) moiety at 5.53 and 5.12 (3JHH 10.50 Hz, 3JHH 10.90 Hz)
for s-trans and s-cis rotamers, respectively (Table I). The acetyl groups
1
are diastereotopic and show two separate signals in H and 13C NMR
spectra for each of the rotamers.
The 1H NMR spectra of 6b and 6c are similar to those of 6a except for
the ester groups, which exhibit characteristic signals with appropriate
chemical shifts.
The check whether the above conclusions regarding the nature of
compound 6 are reasonable, we measured the phosphorus-31 NMR
spectra of 6a–c. Two single 31P signal was observed at about 23 and
24 ppm (downfield from 85% H3PO4) for s-cis and s-trans isomer of these
compounds, respectively. These shifts are similar to those observed for
stable phosphorus ylides [(Ph)3P C].12,13
The variable temperature NMR spectra of compound 6a is studied
in CDCl3. The 1H NMR spectrum of 6a displays two isomers, which are
appreciably broadened by increasing temperature. At about 60 C in
CDCl3 the four tert-butyl signals coalesced and appeared as two fairly
broad bands. Also, the resonance of vicinal CH protons of CHCO2R and
CH(CO) which appears as two sets of doublet of doublet and two sets
of doublet for two s-cis and s-trans isomers have coalesced at 55 C. By
decreasing temperature, the two isomers are populated again in the
ratio about 2:1 at room temperature.
From the coalescence of the tert-butyl protons and using the
expression
√
k = 1 / 2
we calculate the first order rate constant (k) for C C bond rotation of
1
P C C O in 6a is 100.8 s at 60 C. Application of the absolute rate
1
theory14 with a transmission coefficient of 1 gives 1G of 69.1 kJmol
(Scheme 2).
EXPERIMENTAL
All melting points are uncorrected. Elemental analysis was performed
using a Heraeus CHN O rapid analyzer. Mass spectra were recorded on

836
A. Shaabani et al.
TABLE I 1H, 13C, and 31P NMR Data for Compounds 6a–c
Compound 1H/13C/31
P
(ppm) (CDCl3 Me4Si)
s-trans rotamer (68%)
6a
1H
0.95 and 1.40(18H, 2s, 2CMe3), 2.10 and 2.34(6H, 2s, 2MeC O),
3.17(1H, dd, 3JHP 17.4 Hz and 3JHH 10.5 Hz, CH
C P),
5.52(1H, d, 3JHH 10.5 Hz), 7.45–7.68(m, Ph3P).
13C
28.15 and 28.30(2CMe3), 30.20 and 33.34(2Me
1JPC 124.19 Hz, P C), 45.20(d, 2JPC 13.7 Hz, P
66.34(d, 3JPC 4.4 Hz, P
C), 76.97 and 77.26(2 CMe3),
128.14(d, 3JPC 12 Hz, meta-C), 131.76(bs, para-C), 134.11(d,
C
O), 38.64(d,
C
C),
C
C
2JPC 7.8 Hz, ortho-C), 168.87(d, 2JPC 13.1 Hz, P
C C O),
173.84(d, 3JPC 4.5 Hz, P
205.03(2MeC O).
C C C O), 201.87 and
31P
1H
22.99(1s, Ph3P C).
s-cis rotamer (32%)
1.39 and 1.48(18H, 2s, 2CMe3), 2.04 and 2.21(6H, 2s, 2MeC O),
3.12(1H, dd, 3JHP 17.8 Hz and 3JHH 10.9 Hz, CH
C P), 5.11
(1H, d, 3JHH 10.9 Hz), 7.45–7.68(m, Ph3P).
13C
28.15 and 28.95(2CMe3), 29.46 and 32.74(2Me
C
O), 40.47(d,
C),
C C C), 80.24 and 80.27(2CMe3),
1JPC 131.84 Hz, P C), 44.53(d, 2JPC 13.3 Hz, P
C
68.42(d, 3JPC 4.8 Hz, P
128.30(d, 3JPC 12.25 Hz, meta-C), 131.76(bs, para-C),
134.11(d, 2JPC 7.8 Hz, ortho-C), 170.57(d, 2JPC 19.3Hz,
P
C C C C C O), 202.40
O), 173.48(d, 3JPC 3.8 Hz, P
and 204.46 (2MeC O).
24.16(1s, Ph3P C).
31P
6b
s-trans rotamer (65%)
0.43 and 1.16(6H, 2t, 3JHH 7.1 Hz, 2Me CH2), 2.16 and 2.28
1H
(6H, 2s, 2MeC O), 3.34(1H, bm, CH
2ABX3, 2CH2), 5.51(1H, bs, CH CH
PPh3).
C
C
P), 3.52–4.12(4H, m,
P), 7.46–7.68(m,
13C
13.91 and 14.07(2O CH2 Me), 30.49 and 32.82(2MeC O),
39.07(d, 1JPC 123.9 Hz, C P), 44.42(d, 2JPC 13.4 Hz,
P
C C), 57.44 and 60.73(2CH2 O), 66.56(bs, P C C C),
126.50(d, 1JPC 85.0 Hz, ipso C), 128.33(d, 3JPC 12.25 Hz,
meta-C), 131.91(para-C), 134.01(d, 2JPC 9.25 Hz, ortho-C),
169.29(d, 2JPC 13.5 Hz, P
C
C
O), 174.59(d, 3JPC 3.75 Hz,
P
C C C O), 201.98 and 203.95 (2s, 2Me C O).
31P
1H
23.67(1s, Ph3P C).
s-cis rotamer (35%)
1.21 and 1.25(6H, 2t, 3JHH 6.9 Hz, 2Me CH2) 2.09 and
2.19(6H, 2s, 2MeC O), 3.34(1H, bm, CH P),
3.52–4.12(4H, m, 2ABX3, 2CH2), 5.12(1H, d, 3JHH 9.8 Hz,
CH CH P), 7.46–7.68(m, PPh3).
C
C
13C
14.17 and 15.23(2O CH2 Me), 29.83 and 30.49(2 MeC O),
39.07(d, 1JPC 123.9 Hz, C P), 43.64(d, 2JPC 13.1 Hz,
P
C C), 58.12 and 60.73(2CH2 O), 68.30(bs, P C C C),

Triacetylmethane
837
TABLE I 1H, 13C and 31P NMR Data for Compounds 6a–c (Continued)
Compound 1H/13C/31
P
(ppm) (CDCl3 Me4Si)
127.30(d, 1JPC 85.0 Hz, ipso C), 128.43(d, 3JPC 14.6 Hz,
meta-C), 131.91(para-C), 134.01(d, 2JPC 9.25 Hz, ortho-C),
170.30(d, 2JPC 14.6 Hz, P
C
C
O), 174.82(d, 3JPC 4.0 Hz,
O).
P
C
C
C
O), 201.98 and 203.95 (2s, 4Me C
31P
23.86(1s, Ph3P).
6c
s-trans rotamer (65%)
1H
2.17 and 2.27(6H, 2s, 2MeCO), 3.06, and 3.60(6H, 3s, 2OMe),
3.42(1H, bm, 2CH(COMe)2), 5.49(1H, bs, CH
7.21–7.73(m, P(Ph)3).
C P),
13C
29.81 and 30.46(2MeCO), 39.36(d, 1JPC 123.81 Hz, P C),
44.26(d, 2JPC 13.35 Hz, P
C C), 48.75 and 51.70(2OMe),
66.69( bs, P
C C
C), 126.33(d, 1JPC 83.25Hz, ipso-C),
128.42(d, 3JPC 12.0H meta-C), 131.97(d, 4JPC
2.1 Hz, para-C), 133.84(d, 2JPC 9.1 Hz, ortho-C), 169.61(d,
2JPC 13.25 Hz, P
C C
O), 174.96(d, 3JPC 3.75 Hz,
P
C C C O), 201.95 and 203.71(2MeC O).
31P
1H
23.81 (s, Ph3P C).
s-cis rotamer (35%)
2.04 and 2.19(6H, 2s, 2MeCO), 3.59 and 3.60(6H, 2s, 2OMe),
3.42(1H, bm, 2CH(COMe)2), 5.11(1H, bs, CH
7.21–7.73(m, P(Ph)3).
C P),
13C
30.46 and 32.74(2MeCO), 39.98(d, 1Jpc 127.87 Hz, P C),
43.16(d, 2JPC 12.99 Hz, P
68.01(bs, P C
C), 127.03(d, 1JPC 83.25 Hz, ipso-C),
C C), 50.07 and 51.70(3s, 4OMe),
C
128.52(d, 3JPC 11.90 Hz, meta-C), 131.97(d, 4Jpc 2.1 Hz,
para-C), 133.84(d, 2JPC 9.1 Hz, ortho-C), 170.68(d,
2JPC 15.0 Hz, P
C C
O), 175.18(d, 3JPC 4.0 Hz,
P
C
C
C
O), 201.95 and 203.89( 4MeC O).
31P
23.81 (s, Ph3P C).
SCHEME 2

838
A. Shaabani et al.
Finnigan-Matt 8430 mass spectrometer operating at an ionization po-
tential of 70 eV. IR spectra were measured on a Shimadzu IR-470 spec-
1
trometer. H, 13C, and 31P NMR spectra were recorded on a BRUKER
DRX-500 AVANCE spectrometer at 500, 125.77 and 202.46 MHz re-
spectively.
The typical procedure for the preparation of ditert-butyl-2-
(3,1-hydroxyethylidene-2,4-pentanedione-3-yl)-3-(triphenylphospho-
ranylidene)-butanedioate (6a). To a magnetically stirred solution of
3-(1-hydroxyethylidene)-2,4-pentanedione (0.28 g, 2 mmol) and triph-
enylphosphine (0.52 g, 2 mmol) in dichloromethane (10 ml) was added
dropwise a mixture of ditert-butyl acetylenedicarboxylate (0.45 g,
2 mmol) in dichloromethane (5 ml) at 5 C over 10 min. The reaction
mixture was then allowed to warm up to room temperature and stirred
for 24 h. The precipitate was filtered and washed with ethyl acetate
(10 ml). The product was recrystallized from 1:1 dichloromethane:
ethyl acetate to yield 6a as white powder (0.95 g, 81%). m.p. 144–146 C
1
(decom.); max/cm (KBr) 1715 and 1620(C O) (M/Z, %) 588(M, 2),
487(M CO2But, 16), 431(MH CO2But But, 22), 371(M 2CO2But Me,
15), 277(Ph3PO H, 11), 262(Ph3P, 97 183(C12H8P, 90), 108 (PhP, 46),
57(But, 100), 43(CHCO, 58). (Found: C, 71.30%; H, 7.03%. C35H41O6P
requires: C, 71.43%; H, 7.02%).
Selected data for 6b. White powders, 0.79 g, yield 74%, m.p. 165–
1
167 C (decom.), max/cm (KBr 1724 and 1624(C O). (M/Z, %): 532(M,
14), 459(M CO2Et, 32), 277(Ph3PO H, 15), 262(Ph3P, 96) 183(C12H8P,
67), 108(PhP, 40), 43(MeCO, 100). (Found: C, 69.46%; H, 6.20%;
C31H33O6P, requires: C 69.90%; H, 6.24%).
Selected data for 6c. White powders, 0.83g, yield 82%, m.p.
1
183–185 C (decom.), max/cm
(KBr 1725 and 1622 (C O); (M/Z,
%): 504(M+, 9), 445 (M+ CO2 Me, 23), 405(M+ (MeCO)2CH, 46),
333(M (MeCO)2CH CHCO2Me, 15), 277(Ph3PO H, 19), 262(Ph3P,
97), 183(C12H8P, 98), 108(Ph P, 51) 59(CO2Me, 14), 43(MeCO, 100).

Triacetylmethane
839
(Found: C, 68.65%; H, 5.70%. C29H29O6P requires C, 69.03%; H,
5.79%).
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