Synthesis of fused pyrimidone derivatives of 4-pyrones from the acetates of Baylis-Hillman adducts

Article abstract of DOI:10.1007/s10593-010-0466-5

A series of fused pyrimidone derivatives of 4-pyrones was synthesized by conversion of the acetates of Baylis-Hillman adducts obtained from 2-formyl-4-pyrones with 2-aminopyridine and 2-aminothiazole.

Full text of DOI:10.1007/s10593-010-0466-5

Chemistry of Heterocyclic Compounds, Vol. 46, No. 1, 2010
SYNTHESIS OF FUSED PYRIMIDONE
DERIVATIVES OF 4-PYRONES FROM
THE ACETATES OF BAYLIS–HILLMAN
ADDUCTS
A. Shahrisa1* and Z. Ghasemi1
A series of fused pyrimidone derivatives of 4-pyrones was synthesized by conversion of the acetates of
Baylis−Hillman adducts obtained from 2-formyl-4-pyrones with 2-aminopyridine and 2-aminothiazole.
Keywords: fused pyrimidines, heteroaryl-substituted 4-pyrones, Baylis–Hillman reaction.
The fused pyrimidine derivatives are of interest not only for their rich and varied synthetic chemistry but also
for their important medicinal and physiological properties [1-3]. Therefore the synthesis of such derivatives has been
an attractive area of a focus for synthetic organic and bioorganic chemists as well as numerous methods for the
preparation of these heterocyclic compounds have been developed [4-9].
The Baylis–Hillman reaction, a powerful tool for construction of a variety of cyclic and heterocyclic
frameworks, has been used for the synthesis of various fused heterocyclic systems [10, 11] such as fused
pyrimidines. The reaction of 2-aminopyridine with acetates of Baylis–Hillman adducts leading to the formation of
substituted fused pyrimidones has been reported [12]. Later the Baylis–Hillman products of acrylonitrile were used
for the synthesis of annelated pyrimidine derivatives [13]. The allyl amine derivatives generated from acetates of
Baylis–Hillman adducts have been also used as viable precursors for several fused pyrimidine derivatives [14-17].
Heterocyclic substituted 4-pyrones have also been found in a variety of natural and synthetic
biologically active compounds. Some of them are anticoagulants [18] or anti-HIV [19] agents. In continuation of
our attempts in preparing various N-hetaryl-substituted 4-pyrones [20], we turned our attention to the synthesis
of 4-pyrone derivatives containing a fused pyrimidone moiety. Since the Baylis–Hillman derivatives originating
from substituted heterocyclic aldehydes have been known as excellent synthons for the synthesis of polycyclic
ring systems, we first examined the Baylis–Hillman reactions of 2-formyl-4-pyrones that had not yet been
reported. We describe in this report the results of these reactions and the reaction of acetates of these new
adducts with 2-aminopyridine and 2-aminothiazole to afford fused pyrimidone derivatives in 4-pyrone
structures.
_______
* To whom correspondence should be addressed, e-mail: ashahrisa@yahoo.com.
1Department of Organic and Bioorganic Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz 51664,
Iran.
__________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, 37-43, January, 2010. Original article
received August 26, 2009.
30
0009-3122/10/4601-0030©2010 Springer Science+Business Media, Inc.

We initiated our studies from the Baylis–Hillman reaction of 2-formyl-4-pyrones 1a,b. For Baylis–
Hillman coupling of methyl and ethyl acrylates with aldehydes 1a,b, we used a 1,4-dioxane−water (1:1, v/v)
medium in the presence of a stoichiometric amount of 1,4-diazabicyclo[2.2.2]octane (DABCO) (100 mol/%),
and products 2a–d were obtained in short reaction times and excellent yields. These efficient conditions have
been employed for converting a variety of aliphatic and aromatic aldehydes to their corresponding Baylis–
Hillman products [21]. But the best results in the reaction of aldehydes 1a,b with acrylonitrile were achieved
when these reactions were carried out in THF as a solvent in the presence of 100 mol/% of DABCO. The use of
aqueous medium in the reaction with acrylonitrile resulted in a complex mixture of products.
EWG
O
O
R1
R
R1
R
H
DABCO
O
EWG
O
OH
O
2a–f
1a,b
1a, 2a,c,e R = H, R1 = OCH2Ph; 1b, 2b,d,f R = Ph, R1 = H;
2a,b EWG = CO2Me, c,d EWG = CO2Et, e,f EWG = CN
The Baylis–Hillman adducts 2a and 2b obtained by the reaction of aldehydes 1a and 1b with methyl
acrylate were acetylated with acetyl chloride in the presence of pyridine in dichloromethane to yield acetates 3a
and 3b in good yields.
O
R1
AcCl , Py
2a,b
CH2Cl2 , rt
R
O
EWG
OAc
3a,b
3 a R = H, R1 = OCH2Ph; b R = Ph, R1 = H; 3a,b EWG = CO2Me
We then treated acetates 3a,b with 2-aminopyridine in MeOH−H2O (1:1, v/v) at room temperature, and
products 4a,b were obtained by a simple work up in good yields. The mechanism of these reactions as described
before [12] includes Michael attack of ring nitrogen onto the acrylate moiety and subsequent attack of amino
group to ester. Since the reaction of Baylis−Hillman acetates as 1,3-dielectrophilic units with amidines and as
1,3-dinucleophiles for the synthesis of substituted pyrimidine derivatives, has also been reported [22], and
2-aminopyridine has an amidine-like moiety in its structure, we thought that other amidine type heterocycles
such as 2-aminothiazole and 2-aminopyrimidine may similarly react with acetates of Baylis−Hillman adducts to
produce other fused pyrimidone compounds. The treatment of acetates 3a,b with 2-aminothiazole under the same
conditions gave the 7H-thiazolo[3,2-a]pyrimidin-7-ones 5a,b, which were characterized by spectroscopic
methods.
Simultaneously with our studies, Weike et al. reported the reaction of Baylis−Hillman acetates with
2-aminothiazole under solvent-free conditions for the synthesis of 5H-thiazolo[3,2-a]pyrimidin-5-ones [23].
According to the literature [24], 2-aminothiazole is tautomerized to the imine form in solutions at room
temperature and this can cause the reaction pathway involving a conjugative attack of ring nitrogen of
2-aminothiazole to be predominant. The reaction of 2-aminothiazoline with methyl α-bromoacrylate in
methanol, as a similar system, proceeds by this regioselectivity and produces tetrahydroimidazothiazole
derivative [25].
31

We also examined the reaction of acetates 3a,b with 2-aminopyrimidine under these conditions, but we
have obtained only the nonreacted starting materials even for a longer reaction time.
O
R1
R
N
NH2
N
O
N
H2O / MeOH
rt , 7 h
O
3a,b
4a,b
5a,b
N
O
R1
R
S
NH2
N
S
N
H2O / MeOH
rt , 24 h
O
O
In conclusion, we have reported convenient conditions for Baylis–Hillman reaction of 2-formyl-
4-pyrones with alkyl acrylates and acrylonitrile. The acetates of Baylis–Hillman adducts of methyl acrylate,
under cyclization with 2-aminopyridine and 2-aminothiazole in aqueous media at room temperature, have been
converted to pyridopyrimidone and thiazolopyrimidone derivatives of 4-pyrones.
EXPERIMENTAL
Melting points were determined on an Electrothermal MEL-TEMP apparatus (model 1202D) and are
1
13
uncorrected. FT-IR spectra (KBr) were obtained on a Bruker Tensor 27 spectrometer. H and C NMR spectra
were recorded on a Bruker Spectrospin Avance 400 spectrometer operating at 400 and 100 MHz, respectively
(compound 2f − on a Bruker Spectrospin Avance 500 spectrometer) relative to TMS used as internal standards.
NMR spectra were recorded in CDCl3 (compounds 2a–f, 3a,b), CDCl3−CD3OD, 2:1 (v/v) (4a,b), and
CDCl3−CD3OD, 1:1 (v/v) (5a,b). Mass spectra were measured by a Shimadzu (70 eV) spectrometer, and
elemental analyses were measured by a Vario EL ΙΙΙ apparatus (Elementar Co.). Preparative layer chromato-
graphy (PLC) was done using silica gel (Merk Kieselgel 60 PF254+366).
Aldehyde 1a was obtained from commercially available kojic acid by benzylation of phenolic OH [26]
and then oxidation of the hydroxymethyl group with MnO2. Aldehyde 1b was synthesized from the
corresponding ethoxycarbonyl derivative according to the reported procedure [27]. The ethoxycarbonyl
derivative itself was prepared through cyclization of the related 1,3,5-triketone derivative under acidic
conditions, which is an important method for the synthesis of a variety of 4-pyrone structures [28–31].
5-Benzyloxy-2-formyl-4H-pyran-4-one (1a). To a mixture of commercial kojic acid (1.7 g, 12 mmol)
and NaOH (0.514 g, 12.8 mmol) in MeOH (17 ml) and H2O (1.7 ml), benzyl bromide (1.65 ml, 13.8 mmol) was
added and the mixture was heated at 56°C for 4 h. After cooling, water (50 ml) was added with stirring. The
precipitated product was filtered off, washed several times with H2O, and dried first on air and then in an oven at
55°C for 12 h to give 2.08 g (75% yield) of 5-benzyloxy-2-hydroxymethyl-4H-pyran-4-one (benzyl ether of
kojic acid) as a white solid (mp 128-130°C). A solution of benzyl ether of kojic acid (1.16 g, 5 mmol) in dry
CH2Cl2 (60 ml) was mixed with fresh prepared MnO2 (3.8 g, 43.7 mmol), and the suspension was stirred at room
temperature for 48 h. After filtering and removal of CH2Cl2 by a rotary evaporator 0.57 g (yield 50%) of
compound 1a (mp 118–120°C) was obtained as a white solid. FT-IR spectrum, ν, cm–1: 3087, 2923, 2860
1
(aldehyde CH), 1713 (aldehyde C=O), 1647 (pyrone C=O), 1615, 1211, 1139. H NMR, δ, ppm: 5.16 (2H, s,
OCH2Ph); 7.02 (1H, s, H-3 pyrone); 7.36–7.43 (5H, m, C6H5); 7.69 (1H, s, H-6 pyrone); 9.67 (1H, s, CHO).
32

Synthesis of Baylis–Hillman Adducts 2a-d (General Method). To a solution of aldehydes 1a or 1b
(2 mmol) and DABCO (0.224 g, 2 mmol) in dioxane−H2O, 1:1 (v/v) (10 ml), alkyl acrylate (8 mmol) was added
and the solution was stirred at room temperature for 45 min. After adding water (100 ml), the mixture was
extracted with ethyl acetate (4×30 ml). The combined ethyl acetate extract was washed with 100 ml H2O, dried
over Na2SO4, and concentrated to dryness. The residue was purified by preparative layer chromatography (silica
gel, acetone−chloroform−n-hexane, 1:1:2) to give products 2a-d.
2-[(5-Benzyloxy-4-oxo-4H-pyran-2-yl)hydroxymethyl]acrylic Acid Methyl Ester (2a). A white
solid, 75% yield; mp 106°C. FT-IR spectrum, ν, cm–1: 3302 (OH), 3093, 2952, 1717 (ester C=O), 1636 (pyrone
C=O), 1604, 1440, 1197, 1144. 1H NMR spectrum, δ, ppm: 3.74 (3H, s, CH3); 5.00 (2H, s, OCH2Ph); 5.28 (1H,
s, CH–O); 6.00 (1H, s, H-3 pyrone); 6.43 (1H, s, =CH2); 6.53 (1H, s, =CH2); 7.30-7.37 (5H, m, C6H5); 7.49 (1H,
s, H-6 pyrone). 13C NMR spectrum, δ, ppm: 51.2 (CH3); 69.2 (CH2O); 70.8 (CH–O); 111.8, 126.7, 127.3, 127.6,
127.9, 134.5, 136.5, 140.2, 146.0, 164.8, 165.5, 173.8. Mass spectrum, m/z (Irel, %): 316 [M]+ (25), 210
[M-PhCHO]+ (62), 181 [M-PhCHO–OCH3] (20), 91 [PhCH2]+ (100). Found, %: C 64.30; H 5.30. C17H16O6.
Calculated, %: C 64.55; H 5.06.
2-[Hydroxy(4-oxo-6-phenyl-4H-pyran-2-yl)methyl]acrylic Acid Methyl Ester (2b). A white solid,
74% yield; mp 96-98°C. FT-IR spectrum, ν, cm–1: 3166 (OH), 3070, 2958, 1734 (ester C=O), 1644 (pyrone
1
C=O), 1584, 1410, 1256, 1059. H NMR spectrum, δ, ppm (J, Hz): 3.78 (3H, s, CH3); 5.44 (1H, s, CH–O); 6.15
(1H, s, H pyrone); 6.53-6.54 (2H, m, =CH2); 6.69 (1H, d, J = 2.2, H pyrone); 7.42-7.51 (3H, m, C6H5); 7.66-7.68
13
(2H, m, C6H5). C NMR spectrum, δ, ppm: 51.3 (CH3), 69.3 (CH–O), 110.0, 111.8, 124.8, 127.9, 128.0, 129.8,
130.5, 136.8, 162.6, 164.9, 166.3, 179.4. Mass spectrum, m/z (Irel, %): 286 [M]+ (48), 226 [M-HCOOMe]+ (17), 173
{M-[CH2=C(CO2Me)CHO]–1}+ (75), 69 (100). Found, %: C 66.77; H 4.99. C16H14O5. Calculated, %: C 67.13;
H 4.89.
2-[(5-Benzyloxy-4-oxo-4H-pyran-2-yl)hydroxymethyl]acrylic Acid Ethyl Ester (2c). A white solid,
85% yield; mp 57°C. FT-IR spectrum, ν, cm–1: 3342 (OH), 3093, 2983, 1715 (ester C=O), 1643 (pyrone C=O),
1
1611, 1214, 1148, 1062. H NMR spectrum, δ, ppm (J, Hz): 1.26 (3H, t, J = 7.1, OCH2CH3); 3.85 (1H, br. s,
OH); 4.20 (2H, q, J = 7.1, OCH2Me); 5.03 (2H, s, OCH2Ph); 5.27 (1H, s, CH−O); 5.97 (1H, s, H-3 pyrone); 6.43
(1H, s, =CH2); 6.57 (1H, s, =CH2); 7.29–7.36 (5H, m, Ph); 7.51 (1H, s, H-6 pyrone). 13C NMR spectrum, δ, ppm:
13.0 (ester CH3), 60.4 (ester CH2), 69.3 (CH2O), 70.8 (CH–O), 111.7, 126.7, 127.4, 127.6, 127.7, 134.5, 136.7,
140.3, 146.0, 164.3, 165.8, 173.8. Mass spectrum, m/z (Irel, %): 330 [M]+ (25), 224 [M–PhCHO]+ (38), 201
[M-1–HOC–C(CO2Et)=CH2]+ (35), 130 [HOCH2C(CO2Et)=CH2]+ (30), 91 (100). Found, %: C 65.19; H 5.66.
C18H18O6. Calculated, %: C 65.45; H 5.45.
2-[Hydroxy(4-oxo-6-phenyl-4H-pyran-2-yl)methyl]acrylic Acid Ethyl Ester (2d). A white solid,
89% yield; mp 85-86°C. FT-IR spectrum, ν, cm–1: 3272 (OH), 3072, 2984, 1713 (ester C=O), 1659 (pyrone
C=O), 1599, 1405, 1257, 1095. 1H NMR spectrum, δ, ppm (J, Hz): 1.27 (3H, t, J = 7.1, OCH2CH3); 4.23 (2H, q,
J = 7.1, OCH2CH3); 4.91 (1H, d, J = 6.6, OH); 5.44 (1H, d, J = 5.8, CH–O); 6.16 (1H, s, H pyrone); 6.53 (2H,
s, =CH2); 6.67 (1H, d, J = 2.2, H pyrone); 7.41–7.48 (3H, m, C6H5); 7.66–7.68 (2H, m, C6H5). 13C NMR
spectrum, δ, ppm: 14.0 (ester CH3), 61.4 (ester CH2), 70.1 (CH–O), 110.9, 112.8, 125.8, 128.4, 129.0, 130.8,
131.5, 138.4, 163.7, 165.5, 167.8 (ester C=O), 180.6 (pyrone C=O). Mass spectrum, m/z (Irel, %): 300 [M]+ (30),
301 (65), 226 [M–HCO2Et]+ (18), 173 [M+1–HOC–C(CO2Et)=CH2] (75), 69 (100). Found, %: C 67.70; H 5.60.
C17H16O5. Calculated, %: C 68.00; H 5.33.
Synthesis of Baylis–Hillman Adducts 2e-f (General Method). To a solution of aldehydes 1a or 1b
(0.75 mmol) and DABCO (0.084 g, 0.75 mmol) in THF (7 ml), acrylonitrile (3 mmol) was added and the solution
was stirred at room temperature for 12 h. The mixture was concentrated by a rotary evaporator and the residue was
purified by PLC chromatography (silica gel, acetone−chloroform−n-hexane, 1:1:2) to give products 2e–f.
2-[(5-Benzyloxy-4-oxo-4H-pyran-2-yl)hydroxymethyl]acrylonitrile (2e). A white solid, 53% yield;
mp 130°C (decomp.). FT-IR spectrum, ν, cm–1: 3196 (OH), 3107, 2924, 2231 (C≡N), 1644 (pyrone C=O), 1603,
1
1457, 1256, 1204. H NMR spectrum, δ, ppm: 4.98 (2H, s, OCH2Ph); 5.02 (1H, s, CH–O); 6.13 (1H, s, =CH2);
33

13
6.21 (1H, s, =CH2); 6.63 (1H, s, H-3 pyrone); 7.32–7.37 (5H, m, C6H5); 7.58 (1H, s, H-6 pyrone). C NMR
spectrum, δ, ppm: 69.2 (CH2O); 70.8 (CH–O); 111.7, 114.9, 120.8, 126.7, 127.6, 127.7, 132.1, 134.1, 140.0,
146.2, 164.3, 174.0 (pyrone C=O). Mass spectrum, m/z (Irel, %): 283 [M]+ (25), 254 (20), 201
[M-HOCH2C(CN)=CH2–1]+ (20), 177 [M–PhCOH]+ (40), 91 (100). Found, %: C 67.57; H 4.66; N 4.83.
C16H13NO4. Calculated, %: C 67.84; H 4.59; N 4.94.
2-[Hydroxy(4-oxo-6-phenyl-4H-pyran-2-yl)methyl]acrylonitrile (2f). A white solid, 47% yield;
mp 128°C (decomp.). FT-IR spectrum, ν, cm–1: 3342 (OH), 3107, 2925, 2310 (C≡N), 1655 (pyrone C=O), 1596,
1411, 1219. 1H NMR spectrum (500 MHz), δ, ppm (J, Hz): 5.27 (1H, s, CH–O); 6.28 (1H, s, H pyrone); 6.39 (1H,
d, J = 0.7, H pyrone); 6.69 (1H, d, J = 1.5, =CH2); 6.78 (1H, d, J = 1.7, =CH2); 7.49–7.56 (3H, m, C6H5);
7.78-7.80 (2H, m, C6H5). 13C NMR spectrum (125 MHz), δ, ppm: 70.8 (CH–O), 112.7, 114.9, 121.1, 125.9,
127.3, 127.7, 131.9, 134.1, 140.0, 146.4, 164.7, 174.0 (pyrone C=O). Mass spectrum, m/z (Irel, %): 253 [M]+
(25), 69 (100). Found, %: C 70.77; H 4.56; N 5.83. C15H11NO3. Calculated, %: C 71.14; H 4.34; N 5.53.
Synthesis of Baylis-Hillman Acetates 3a,b (General Method). To a solution of alcohols 2a-b
(1 mmol) in dry CH2Cl2 (3 ml), acetyl chloride (0.3 ml, 4.2 mmol) and pyridine (0.06 ml) were added and the
solution was stirred at room temperature for 4 h. The mixture was concentrated by a rotary evaporator and the
residue was purified by PLC chromatography (silica gel, acetone–n-hexane, 1:3).
2-[Acetoxy(5-benzyloxy-4-oxo-4H-pyran-2-yl)methyl]acrylic Acid Methyl Ester (3a). A colorless
liquid, 67% yield. FT-IR spectrum, ν, cm–1: 3089, 2953, 1756 (ester C=O), 1725 (ester C=O), 1665 (pyrone
1
C=O), 1436, 1372, 1208. H NMR spectrum, δ, ppm: 2.14 (3H, s, CH3CO); 3.76 (3H, s, CO2CH3); 5.04 (2H, s,
OCH2Ph); 5.96 (1H, s, CH–O); 6.42 (1H, s, =CH2); 6.46 (1H, s, =CH2); 6.53 (1H, s, H-3 pyrone); 7.29–7.39
(5H, m, C6H5); 7.54 (1H, s, H-6 pyrone). 13C NMR spectrum, δ, ppm: 19.5 (CH3CO), 51.2 (OCH3), 67.8
(CHOAc), 70.7 (OCH2Ph), 113.0, 126.5, 127.3, 127.5, 128.0, 134.1, 134.4, 140.1, 146.2, 161.3, 163.3, 167.6
(ester C=O), 173.1 (pyrone C=O). Found, %: C 63.82; H 4.96. C19H18O7. Calculated, %: C 63.68; H 5.02.
2-[Acetoxy(4-oxo-6-phenyl-4H-pyran-2-yl)methyl]acrylic Acid Methyl Ester (3b). A white solid,
70% yield; mp 93°C. FT-IR spectrum, ν, cm–1: 3066, 2952, 1752 (ester C=O), 1725 (ester C=O), 1660 (pyrone
C=O), 1445, 1394, 1219. 1H NMR spectrum, δ, ppm (J, Hz): 2.19 (3H, s, CH3CO); 3.79 (3H, s, CO2CH3); 6.08
(1H, s, CH–O); 6.41 (1H, d, J = 2.0, H pyrone); 6.59 (2H, s, =CH2); 6.74 (1H, d, J = 2.1, H pyrone); 7.45-7.53
(3H, m, C6H5); 7.69-7.71 (2H, m, C6H5). 13C NMR spectrum, δ, ppm: 19.7 (CH3CO), 51.4 (OCH3), 68.0
(CHOAc), 110.3, 110.4, 113.1, 124.8, 128.0, 128.1, 129.8, 130.6, 134.5, 162.1, 162.6, 167.8 (ester C=O), 178.6
(pyrone C=O). Found, %: C 65.49; H 4.63. C18H16O6. Calculated, %: C 65.85; H 4.88.
Synthesis of fused pyrimidones 4, 5 (General Method). To a solution of acetates 3a,b (0.5 mmol) in
MeOH–H2O, 1:1 (v/v), (12 ml) a solution of 2-aminopyridine or 2-aminothiazole (0.5 mmol) in MeOH–H2O, 1:1
(v/v), (6 ml) was added and the mixture was stirred at room temperature for 7 h (for 2-aminopyridine) and for 24
h (for 2-aminothiazole). The resullting precipitate was collected by filtration. The precipitate obtained from the
reaction of compounds 3a,b with 2-aminopyridine was washed with acetone and dried in vacuo to give products
4a,b as white solids. The crude products obtained from the reaction of compounds 3a,b with 2-aminothiazole
were purified by PLC chromatography (silica gel, dichloromethane–methanol, 10:1) to give products 5a,b
as white solids.
3-[(5-Benzyloxy-4-oxo-4H-pyran-2-yl)methyl]-2H-pyrido[2,1-a]pyrimidin-2-one (4a). A white solid,
76% yield; mp 220-222°C (decomp.). FT-IR spectrum, ν, cm–1: 3080, 2940, 1637 (C=O), 1596, 1485, 1218. 1H
NMR spectrum, δ, ppm: 3.70 (2H, s, CH2 pyrimidone); 4.83 (2H, s, OCH2Ph); 6.32 (1H, s, H-3 pyrone); 6.88
(1H, t, J = 6.8, Py); 7.15-7.26 (6H, m, Ph (5H), Py (1H)); 7.62 (1H, t, J = 7.5, Py); 7.67 (1H, s, H-6 pyrone);
13
8.08 (1H, d, J = 6.6, Py); 8.21 (1H, s, H pyrimidone). C NMR spectrum, δ, ppm: 31.0 (CH2), 70.2 (OCH2),
113.1, 113.4, 121.8, 122.3, 126.8, 127.2, 127.6, 132.7, 133.7, 136.0, 136.6, 139.4, 145.9, 150.1, 163.8, 166.5,
173.7. Mass spectrum, m/z (Irel, %): 360 [M]+ (17), 269 (24), 213 (25), 184 (80), 91 (100). Found, %: C 69.82;
H 4.76; N 7.83. C21H16N2O4. Calculated, %: C 70.00; H 4.44; N 7.78.
34

3-[(4-Oxo-6-phenyl-4H-pyran-2-yl)methyl]-2H-pyrido[2,1-a]pyrimidin-2-one (4b). A white solid,
74% yield; mp 234–236°C (decomp.). FT-IR spectrum, ν, cm–1: 3067, 2996, 1654 (C=O), 1589, 1470, 1399,
1
1149. H NMR spectrum, δ, ppm: 4.01 (2H, s, CH2 pyrimidone); 6.36 (1H, s, H pyrone); 6.77 (1H, d, J = 0.9,
H pyrone); 7.06 (1H, t, J = 6.8, Py); 7.35 (1H, d, J = 9.0, Py); 7.47–7.56 (3H, m, C6H5); 7.75 (1H, t, J = 8.1,
13
Py); 7.82 (2H, d, J = 7.4, C6H5); 8.17 (1H, d, J = 6.6, Py); 8.50 (1H, s, H pyrimidone). C NMR spectrum, δ,
ppm: 31.1 (CH2), 108.9, 112.9, 113.4, 122.1, 122.2, 124.8, 127.9, 129.4, 130.6, 132.5, 136.2, 137.4, 150.7,
163.9, 165.3, 167.2, 180.2. Mass spectrum, m/z (Irel, %): 330 [M]+ (18), 210 (50), 184 (48), 105 (80), 77 (100).
Found, %: C 72.60; H 4.40; N 8.20. C20H14N2O3. Calculated, %: C 72.72; H 4.24; N 8.48.
6-[(5-Benzyloxy-4-oxo-4H-pyran-2-yl)methyl]-7H-thiazolo[3,2-a]pyrimidin-7-one (5a). A white
solid, 59% yield; mp 222–224°C (decomp.). FT-IR spectrum, ν, cm–1: 3082, 2932, 1642 (C=O), 1607, 1485,
1
1220. H NMR spectrum, δ, ppm: 3.74 (2H, s, CH2 pyrimidone); 4.98 (2H, s, OCH2Ph); 6.35 (1H, s, H-3
pyrone); 7.16 (1H, d, J = 4.7, H thiazole); 7.29–7.36 (5H, m, C6H5); 7.59 (1H, d, J = 4.5, H thiazole); 7.76 (1H, s,
13
H-6 pyrone); 8.34 (1H, s, H pyrimidone). C NMR spectrum, δ, ppm: 30.2 (CH2); 69.7 (OCH2); 110.6, 112.1,
117.1, 123.4, 126.1, 126.7, 126.8, 133.8, 134.8, 139.8, 145.3, 163.6, 163.9, 165.9, 173.7. Mass spectrum, m/z
(Irel, %): 366 [M]+ (18), 276 (25), 219 (45), 190 (100), 166 (100). Found, %: C 62.02; H 3.55; N 7.70.
C19H14N2O4S. Calculated, %: C 62.29; H 3.82; N 7.65.
6-[(4-Oxo-6-phenyl-4H-pyran-2-yl)methyl]-7H-thiazolo[3,2-a]pyrimidin-7-one (5b). A white solid,
55% yield; mp 235–236°C (decomp.). FT-IR spectrum, ν, cm–1: 3081, 2926, 1650 (C=O), 1607, 1483, 1261.
1H NMR spectrum, δ, ppm: 3.86 (2H, s, CH2 pyrimidone); 6.27 (1H, d, J = 2.1, H pyrone); 6.72 (1H, d, J = 2.1,
H pyrone); 7.08 (1H, d, J = 4.8, H thiazole); 7.42–7.51 (3H, m, C6H5); 7.53 (1H, d, J = 4.8, H thiazole);
13
7.74-7.77 (2H, m, C6H5); 8.34 (1H, s, H pyrimidone). C NMR spectrum, δ, ppm: 31.1 (CH2), 109.2, 110.5,
113.0, 118.2, 123.7, 125.0, 125.1, 128.2, 129.6, 130.8, 134.6, 164.0, 164.2, 165.4, 180.3. Mass spectrum, m/z
(Irel, %): 336 [M]+ (30), 237 (18), 210 (70), 190 (100), 77 (65). Found, %: C 64.50; H 3.21; N 8.37. C18H12N2O3S.
Calculated, %: C 64.28; H 3.57; N 8.33.
We thank research affairs of University of Tabriz for financial support.
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