Synthesis and reactions of pyrazole-4-carbaldehydes

Article abstract of DOI:10.1134/S1070428009070100

1-, 3-, and 5-Alkylpyrazoles, as well as linearly bridged bis-pyrazoles, were converted into the corresponding 4-formyl derivatives by Vilsmeier-Haak reaction both under standard conditions and under microwave activation in DMF over a period of 10 min. 1,1'-(Hexane-1,6-diyl)bis(3,5-dimethyl-1H-pyrazole) and 1,1'-(benzene-1,4-diyldimethylene)bis(3,5-dimethyl-1H-pyrazole) gave rise to 4-formyl derivatives at both pyrazole rings. 5-Chloro-1,3-dialkyl-1H-pyrazoles failed to undergo formylation according to Vilsmeier-Haak or under microwave activation. 1,1'-Bridged bis-3,5-dimethyl-1H-pyrazoles reacted with 2-sulfanylethanol on heating in the presence of chloro(trimethyl)silane to give the corresponding bridgedbis-4-(1,4,6-oxadithiocan-5-yl)-1H-pyrazoles.

Full text of DOI:10.1134/S1070428009070100

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2009, Vol. 45, No. 7, pp. 1040–1044. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © E.V. Rudyakova, V.A. Savosik, L.K. Papernaya, A.I. Albanov, I.T. Evstaf’eva, G.G. Levkovskaya, 2009, published in Zhurnal
Organicheskoi Khimii, 2009, Vol. 45, No. 7, pp. 1053–1057.
Synthesis and Reactions of Pyrazole-4-carbaldehydes
E. V. Rudyakova, V. A. Savosik, L. K. Papernaya, A. I. Albanov,
I. T. Evstaf’eva, and G. G. Levkovskaya
Favorskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
e-mail: ggl@irioch.irk.ru
Received July 28, 2008
Abstract—1-, 3-, and 5-Alkylpyrazoles, as well as linearly bridged bis-pyrazoles, were converted into the
corresponding 4-formyl derivatives by Vilsmeier–Haak reaction both under standard conditions and under
microwave activation in DMF over a period of 10 min. 1,1′-(Hexane-1,6-diyl)bis(3,5-dimethyl-1H-pyrazole)
and 1,1′-(benzene-1,4-diyldimethylene)bis(3,5-dimethyl-1H-pyrazole) gave rise to 4-formyl derivatives at both
pyrazole rings. 5-Chloro-1,3-dialkyl-1H-pyrazoles failed to undergo formylation according to Vilsmeier–Haak
or under microwave activation. 1,1′-Bridged bis-3,5-dimethyl-1H-pyrazoles reacted with 2-sulfanylethanol on
heating in the presence of chloro(trimethyl)silane to give the corresponding bridged bis-4-(1,4,6-oxadithiocan-
5-yl)-1H-pyrazoles.
DOI: 10.1134/S1070428009070100
Pyrazoles belong to one of the most important clas-
ses of heterocyclic compounds which are very signif-
icant for medicinal chemistry [1]. Molecules of many
modern drugs, e.g., antiphlogistic, antidiabetic, anal-
gesic, etc., as well as of insectoacaricides used in prac-
tice, contain pyrazole ring as structural fragment [1, 2].
In continuation of our studies on the synthesis and
properties of pyrazoles and halopyrazoles derived from
chloro enones [3, 4], in the present work we examined
formylation of 5-chloropyrazoles and linearly bridged
bis-pyrazoles according to Vilsmeier–Haak. Introduc-
tion of an aldehyde group into pyrazole molecule was
expected to ensure intramolecular heterocyclizations
with formation of fused or linearly linked heterocyclic
compounds [5]. From this viewpoint, the synthetic po-
tential of halogen-substituted pyrazolecarbaldehydes is
difficult to overestimate [6]. For example, various
linear and fused polyheterocyclic systems were synthe-
sized from 5-chloro-3-methyl-1-phenyl-1H-pyrazole-
4-carbaldehyde and typical reagents for carbonyl
group, such as hydrazines, hydroxylamine, and thio-
semicarbazide, as well as diamines of the aliphatic and
aromatic series [6].
It is known that 1-unsubstituted, 1-alkyl-, and
1-phenyl-3-alkyl-4-formyl-5-chloro(bromo)pyrazoles
are formed by reactions of the corresponding pyrazol-
5-ones with phosphoryl chloride or bromide in dimeth-
ylformamide (Vilsmeier–Haak reaction) [6–8]. Pre-
sumably, the initial step is introduction of a formyl
group into pyrazol-5-one (5-hydroxypyrazole), and
next follows halogenation of 4-formylpyrazol-5-one by
the action of POHlg3. This reaction scheme is support-
ed by the fact that pyrazol-5-ones are converted into
5-halopyrazoles by reaction with phosphoryl chloride
under severe conditions. For example, 5-chloro-
(bromo)pyrazoles were synthesized for the first time
by heating pyrazol-5-ones with phosphoryl chloride or
bromide for 9–12 h at 100–130°C in a sealed ampule
Scheme 1.
R1
R1
CHO
Cl
R2
R3
R1
Cl
H+ or base, Δ
POCl3, DMF
N
N
+
H2N
N
Cl
N
N
O
Cl
R2
R2
Ia–Ic
R1 = R2 = R3 = Me (a); R1 = Pr, R2 = Me, R3 = Me (b); R1 = Me, R2 = Et, R3 = H (c).
1040

SYNTHESIS AND REACTIONS OF PYRAZOLE-4-CARBALDEHYDES
1041
Scheme 2.
Me
Me
CHO
Me
POCl3, DMF
PhCH2Cl
N
N
Me
Me
N
N
CH2Ph
CH2Ph
Me
Id
IId
N
Me
OCH
CHO
N
Me
Me
Me
H
POCl3, DMF
ClCH2ZCH2Cl
Me
Me
Me
Me
N
N
Z
N
N
Z
N
N
N
N
Ie, If
IIe, IIf
Z = (CH2)4 (e), 1,4-C6H4 (f).
[9]. This procedure was then widely used for the pre-
paration of halopyrazoles from pyrazolones, and only
reaction conditions, halogenating agents, and solvents
were varied [10–12].
zoles Ie and If readily reacted with phosphoryl chlo-
ride in DMF under mild conditions to give the corre-
sponding 4-formyl derivatives in good yields. By car-
rying out these reactions under microwave irradiation
we succeeded in considerably shortening the reaction
time. The yields of pyrazole-4-carbaldehydes IId–IIf
were 52 to 84% (Scheme 2). The structure of com-
pounds Id–If and IId–IIf was confirmed by IR and
NMR spectra and elemental analyses.
However, we failed to obtain 1,3-dialkyl-5-chloro-
1H-pyrazole-4-carbaldehydes by Vilsmeier–Haak reac-
tion of 1,3-dialkyl-5-chloro-1H-pyrazoles Ia–Ic pre-
pared from alkyl 2,2-dichlorovinyl ketones and alkyl
or 1,1-dialkylhydrazines [3] (Scheme 1). The reactions
were carried under the conditions described in [6–8],
but neither raising the temperature nor increasing the
reaction time led to the formation of desired products.
5-Chloropyrazoles Ia–Ic also failed to react with phos-
phoryl chloride or bromide in DMF under microwave
activation.
We then tried to effect formylation of pyrazoles
Id–If which were synthesized by alkylation of 3,5-di-
methyl-1H-pyrazole with the corresponding halogen
derivatives in DMSO in the presence of alkali [13]
(Scheme 2). Unlike the procedure reported in [13], we
used considerably lesser amount of the solvent (by
a factor of more than 10), and heating of the reaction
mixture was avoided. The yields of N-substituted pyra-
zoles Id–If were 84–87%.
Bis-pyrazoles IIe and IIf were brought into reaction
with 2-sulfanylethanol in the presence of chloro(tri-
methyl)silane with a view to obtain new polyfunctional
pyrazole derivatives and develop new procedures for
the protection of aldehyde group. We previously
showed [14–16] that aldehydes of the thiophene series
react with alkanethiols and dithiols in the presence of
Me3SiCl under mild conditions to give the correspond-
ing acyclic and cyclic dithioacetals. The reactions of
pyrazolecarbaldehydes IIe and IIf with 2-sulfanyl-
ethanol were carried out using 10-fold excess of
Me3SiCl (reaction time 2–4 h). However, unlike alde-
hydes of the thiophene series [14–16], the reactions
with aldehydes IIe and IIf required elevated tempera-
ture (50–70°C), and the products were previously un-
known 1,4,6-oxadithiocane derivatives IIIe and IIIf
(Scheme 3). It is known that 2-sulfanylethanol and
Unlike chloropyrazoles Ia–Ic, 1-benzyl-3,5-dimeth-
yl-1H-pyrazole (Id) and newly synthesized bis-pyra-
Scheme 3.
O
O
S
N
S
N
OCH
CHO
S
S
Me
Me
Me
Me
4HO(CH2)2SH, Me3SiCl
Me
Me
Me
Me
N
Z
N
N
Z
N
N
N
IIe, IIf
IIIe, IIIf
Z = (CH2)4 (e), 1,4-C6H4 (f).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 7 2009

RUDYAKOVA et al.
1042
3-sulfanylpropan-1-ol react with aliphatic and aromatic
aldehydes in the presence of scandium trifluorometh-
anesulfonate [17], boron trifluoride [18], or p-toluene-
sulfonic acid [19] to afford the expected 1,3-oxathiol-
anes and 1,3-oxathianes. No corresponding pyrazolyl-
oxathiolanes were formed when the reactions were
performed in excess Me3SiCl at a pyrazolecarbalde-
hyde-to-2-sulfanylethanol ratio of 1:2; in this case we
isolated a mixture of unreacted pyrazole II and com-
pound III.
NMR spectra were measured on a Bruker DPX-400
instrument at 400.13 and 101.61 MHz, respectively,
using HMDS as internal reference. The chemical shifts
were determined with an accuracy of ±0.01 (1H) and
1
±0.02 ppm (13C), and the H–1H coupling constants
were determined with an accuracy of ±0.1 Hz. Micro-
wave-assisted reactions were performed in a Samsung
microwave furnace (800 W, 2450 MHz).
5-Chloro-1,3-dimethyl-1H-pyrazole (Ia) and
5-chloro-1-methyl-3-propyl-1H-pyrazole (Ib) were
synthesized by reactions of 1,1-dimethylhydrazine
with 1,1-dichlorobut-1-en-3-one and 1,1-dichlorohex-
1-en-3-one, respectively; 5-chloro-1-ethyl-3-methyl-
1H-pyrazole (Ic) was prepared from 1,1-dichlorobut-1-
en-3-one and ethylhydrazine according to the proce-
dure described in [3]. The physical constants of chloro-
pyrazoles Ia–Ic were consistent with published data.
According to our previous data [14, 16], chloro-
(trimethyl)silane facilitates protonation of the carbonyl
group in thiophenecarbaldehydes, thus favoring thio-
acetalization. In addition, Me3SiCl acts as dehydrating
agent which effectively binds liberated water and en-
sures selective formation of 1,3-dithiolanes and 1,3-di-
thianes. In the reactions with compounds IIe and IIf
each carbonyl group binds two molecules of 2-sul-
fanylethanol, and the subsequent heterocyclization
yields 1,4,6-oxadithiocane derivatives IIIe and IIIf.
The observed reaction direction may be determined by
electronic and steric effects of the neighboring methyl
groups in positions 3 and 5 of the pyrazole ring.
1-Benzyl-3,5-dimethyl-1H-pyrazole (Id). A mix-
ture of 11.20 g (0.2 mol) of potassium hydroxide and
10 ml of dimethyl sulfoxide was stirred for 10 min,
9.61 g (0.1 mol) of 3,5-dimethyl-1H-pyrazole was
added, and the mixture was stirred for 20 min at 20–
22°C. Benzyl chloride, 15.19 g (0.12 mol), was slowly
added at such a rate that the temperature did not
exceed 30°C, and the mixture was stirred for 3 h at 20–
22°C, poured into 100 ml of cold water, and extracted
with diethyl ether. The extract was dried over MgSO4
and evaporated, and the residue was distilled under
reduced pressure. Yield 16.20 g (87%), bp 191–193°C
(20 mm). IR spectrum, ν, cm–1: 3121 (=C–H, pyra-
zole), 3025 (=C–H, Ph), 2979, 2918, 2861 (C–H,
The structure of compounds IIIe and IIIf was
confirmed by spectral and analytical methods. The IR
spectra of IIIe and IIIf lacked carbonyl absorption
bands typical of initial bis-pyrazoles IIe and IIf,
but absorption bands appeared in the region 1020–
1043 cm–1 due to vibrations of the oxadithiocane frag-
ment. Unlike bis-pyrazoles IIe and IIf, no signal as-
signable to aldehyde proton was present in the 1H NMR
spectra of IIIe and IIIf.
1
aliph.), 1634 (C=C, C=N). H NMR spectrum (CCl4),
Taking into account that several simple and effec-
tive methods, including solvent-free procedures [20],
have been proposed for deprotection of carbonyl
groups, pyrazoles IIIe and IIIf may be used as inter-
mediate products for further transformations.
δ, ppm: 1.97 s (3H, CH3), 2.13 s (3H, CH3), 4.98 s
(2H, CH2), 5.62 s (1H, 4-H), 6.95 m and 7.19 m (5H,
C6H5). Found, %: C 77.58; H 7.57; N 14.99. C12H14N2.
Calculated, %: C 77.38; H 7.58; N 15.04.
1,1′-(Hexane-1,6-diyl)bis(3,5-dimethyl-1H-pyra-
zole) (Ie) was synthesized in a similar way from 9.61 g
(0.1 mol) of 3,5-dimethyl-1H-pyrazole and 9.30 g
(0.06 mol) of 1,6-dichlorohexane using 11.20 g
(0.2 mol) of potassium hydroxide. Yield 11.52 g
(84%), bp 192–196°C (15 mm). IR spectrum, ν, cm–1:
3125 (=C–H, pyrazole), 2928, 2862 (C–H, aliph.),
To conclude, we have developed convenient pre-
parative procedures for the synthesis of previously
unknown pyrazole- and bis-pyrazolecarbaldehydes and
2-(pyrazol-4-yl)-1,4,6-oxadithiocanes. The newly syn-
thesized compounds attract interest as potential bio-
logically active substances, as well as precursors and
reagents for the design of complex polyfunctional
structures.
1
1639, 1549 (C=C, C=N). H NMR spectrum (CDCl3),
δ, ppm: 1.29 br.s (4H, CH2), 1.74 br.s (4H, CH2),
2.17 br.s (12H, CH3), 3.88 t (4H, NCH2), 5.72 s (2H,
4-H). Found, %: C 70.12; H 9.52; N 20.44. C16H26N4.
Calculated, %: C 70.03; H 9.55; N 20.42.
EXPERIMENTAL
The IR spectra were recorded on a Varian-3100
spectrometer with Fourier transform using an ATR
1,1′-(Benzene-1,4-diyldimethylene)bis(3,5-di-
methyl-1H-pyrazole) (If) was synthesized in a similar
1
(attenuated total reflectance) adapter. The H and 13C
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 7 2009

SYNTHESIS AND REACTIONS OF PYRAZOLE-4-CARBALDEHYDES
1043
way from 9.61 g (0.1 mol) of 3,5-dimethyl-1H-pyra-
zole and 10.50 g (0.06 mol) of 1,4-bis(chloromethyl)-
benzene using 11.20 g (0.2 mol) of potassium hydrox-
ide. The reaction mixture was poured into 100 ml of
cold water, and the precipitate was filtered off and
dried in air. Yield 12.62 g (86%), mp 95–97°C. IR
spectrum, ν, cm–1: 3121 (=C–H, pyrazole), 3025 (=C–
Harom), 2979, 2918, 2861 (C–H, aliph.), 1634, 1547
(NCH2), 117.69, 143.41, 150.69 (pyrazole), 184.59
(C=O). Found, %: C 65.68; H 8.32; N 16.58.
C18H26N4O2. Calculated, %: C 65.41; H 7.94; N 16.96.
1,1′-(Benzene-1,4-diyldimethylene)bis(3,5-di-
methyl-1H-pyrazole-4-carbaldehyde) (IIf) was syn-
thesized from 14.72 g (0.05 mol) of compound If.
Yield 14.91 g (85%) (a), 14.20 g (81%) (b); mp 151–
153°C. IR spectrum, ν, cm–1: 3045 (=C–Harom), 2955,
2855, 2820, 2738 (C–H, aliph.), 1667 (C=O), 1540
1
(C=C, C=N). H NMR spectrum (CDCl3), δ, ppm:
1
2.10 s (6H, CH3), 2.20 s (6H, CH3), 5.14 s (4H,
NCH2), 5.80 s (2H, 4-H), 6.97 s (4H, C6H4). Found, %:
C 73.40; H 7.52; N 19.08. C18H22N4. Calculated, %:
C 73.44; H 7.53; N 19.03.
(C=C, C=N). H NMR spectrum (CDCl3), δ, ppm:
2.42 s (6H, CH3), 2.43 s (6H, CH3), 5.19 s (4H, NCH2),
7.07 s (4H, C6H4), 9.89 s (2H, CHO). 13C NMR spec-
trum, δC, ppm: 9.92, 12.25 (CH3), 51.87 (NCH2),
127.20, 135.32 (C6H4), 118.21, 144.15, 150.87 (pyra-
zole), 184.56 (C=O). Found, %: C 69.00; H 6.59;
N 16.43. C20H22N4O2. Calculated, %: C 68.54; H 6.33;
N 16.00.
1,3-Dimethyl-1H-pyrazole-4-carbaldehydes IId–
IIf (general procedure). a. 1-Substituted 3,5-dimethyl-
1H-pyrazole Id–If, 0.1 mol, was dissolved in 11 g
(0.15 mol) of dimethylformamide, 23 g of phosphoryl
chloride was added dropwise, and the mixture was
stirred for 5 h at 70–75°C, poured into 200 ml of cold
water, and neutralized with a saturated solution of
sodium hydrogen carbonate to pH 7–8. The precipitate
was filtered off and dried in air.
1,1′-(Hexane-1,6-diyl)bis[3,5-dimethyl-4-(1,4,6-
oxadithiocan-5-yl)-1H-pyrazole] (IIIe). 2-Sulfanyl-
ethanol, 0.63 g (8 mmol), was added dropwise under
stirring and heating to a mixture of 0.66 g (2 mmol) of
compound IIe and 2.5 ml of chloro(trimethyl)silane.
The mixture was vigorously stirred for 4 h at 50–70°C
and cooled, and the precipitate was filtered off, washed
with cold hexane, and dried under reduced pressure.
Yield 1.05 g (92%), white powder, mp 144–146°C. IR
spectrum, ν, cm–1: 2953, 2922, 2870, 2859 (C–H),
b. A mixture of 0.1 mol of dimethylpyrazole Id–If,
20 ml of DMF, and 23 g of POCl3, prepared in a one-
neck flask equipped with a reflux condenser, was
placed in a microwave furnace and irradiated over
a period of 10 min. The mixture was then treated as
described above in a.
1
1545 (C=C, C=N), 1041, 1020 (C–O–C). H NMR
spectrum (CD3OD), δ, ppm: 1.42 m (4H, CH2), 1.89 m
(4H, CH2), 2.53 s and 2.55 s (6H each, CH3), 2.71 d.t
and 2.83 d.t (4H each, SCH2, 2J = 13.69, 3J = 6.36 Hz),
3.73 d.t and 3.76, d.t (4H each, OCH2, 2J = 11.37, 3J =
1-Benzyl-3,5-dimethyl-1H-pyrazole-4-carbalde-
hyde (IId) was synthesized from 18.63 g (0.1 mol) of
pyrazole Id. Yield 11.60 g (54%) (a), 10.70 g (50%)
(b); mp 66–68°C. IR spectrum, ν, cm–1: 3045 (=C–H,
Ph), 2957, 2859, 2823, 2739 (C–H, aliph.), 1670
(C=O), 1547 (C=C, C=N). 1H NMR spectrum (CDCl3),
δ, ppm: 2.42 s (6H, CH3), 5.21 s (2H, NCH2), 7.11 d
and 7.28 m (5H, C6H5), 9.88 s (1H, CHO). 13C NMR
spectrum, δC, ppm: 10.27 and 12.59 (CH3), 52.74
(NCH2), 126.92, 128.12, 129.02, 135.71 (Ph), 118.59,
144.50, 151.13 (pyrazole), 184.92 (C=O). Found, %:
C 72.81; H 6.56; N 13.09. C13H14N2O. Calculated, %:
C 72.87; H 6.59; N 13.07.
3
6.6 Hz), 4.32 t (4H, NCH2, J = 7.09 Hz), 5.47 s (2H,
SCHS). 13C NMR spectrum, δC, ppm: 10.74, 10.38
(CH3), 26.72 (CH2), 30.09 (CH2), 36.24 (SCH2), 43.73
(SCHS), 49.78 (NCH2), 62.88 (OCH2), 119.99, 145.08,
144.97 (pyrazole). Found, %: C 54.41; H 7.35; N 9.91;
S 22.43. C26H42N4O2S4. Calculated, %: C 54.92;
H 7.04; N 9.85; S 22.69.
1,1′-(Benzene-1,4-diyldimethylene)bis[3,5-di-
methyl-4-(1,4,6-oxadithiocan-5-yl)-1H-pyrazole]
(IIIf) was synthesized in a similar way from 0.70 g
(2 mmol) of compound IIf and 0.63 g (8 mmol) of
2-sulfanylethanol in 2.5 ml of Me3SiCl. Excess
Me3SiCl was removed under reduced pressure, the
light yellow oily residue was treated with ethanol, and
the solvent was removed by decanting. The solution
was evaporated. Yield 1.0 g (86%), light yellow thick
waxy material. IR spectrum, ν, cm–1: 3059 (C–Harom),
2946, 2917, 2867, 2739 (C–Haliph), 1545 (C=C, C=N),
1043 (C–O–C). 1H NMR spectrum, δ, ppm: 2.44 s and
1,1′-(Hexane-1,6-diyl)bis(3,5-dimethyl-1H-pyra-
zole-4-carbaldehyde) (IIe) was synthesized from
13.72 g (0.05 mol) of compound Ie. Yield 8.60 g
(52%) (a), 8.92 g (54%) (b); mp 85–86°C. IR spec-
trum, ν, cm–1: 2939, 2858, 2814, 2734 (C–H, aliph.),
1
1665 (C=O), 1541 (C=C, C=N). H NMR spectrum
(CDCl3), δ, ppm: 1.32 br.s (2H, CH2), 1.79 br.s (2H,
CH2), 2.41 s (6H, CH3), 2.47 s (6H, CH3), 3.95 t (2H,
NCH2), 9.88 s (2H, CHO). 13C NMR spectrum, δC,
ppm: 9.83, 12.16 (CH3), 25.98, 29.34 (CH2), 48.11
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 7 2009

RUDYAKOVA et al.
1044
6. Pawer, A. and Patil, A.A., Indian J. Chem., 1994,
vol. 33, p. 156.
7. Malhotra, M., Falt-Hansen, B., and Becher, J.,
J. Heterocycl. Chem., 1991, vol. 28, p. 1837.
8. Wang, X.J., Tan, J., and Grozinger, K., Tetrahedron
Lett., 2000, vol. 41, p. 4713.
9. Michaelis, A. and Dorn, H., Chem. Ber., 1907, vol. 23,
p. 179;* Michaelis, A. and Dorn, H., Justus Liebigs Ann.
Chem., 1907, vol. 325, p. 163;* Auwers, K. and
Niemyer, F., J. Prakt. Chem., 1925, vol. 110, p. 153.
2.43 s (6H each, CH3), 2.65 m and 2.77 m (4H each,
SCH2), 3.66 m (8H, OCH2), 5.55 s (4H, NCH2), 5.41 s
(2H, SCHS), 7.28 s (4H, C6H4). 13C NMR spectrum,
δC, ppm: 10.62, 10.81 (CH3), 36.21 (SCH2), 43.49
(SCHS), 52.53 (NCH2), 62.75 (OCH2), 129.29, 135.43
(C6H4), 120.55, 145.60 (pyrazole). Found, %: C 57.33;
H 6.06; N 9.41; S 21.93. C28H38N4O2S4. Calculated, %:
C 57.14; H 6.12; N 9.52; S 21.76.
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 7 2009