Synthesis and conformational studies of tertiary alcohols derived from tetrahydro-4H-pyran-4-one and tetrahydrothiopyran-4-one

Article abstract of DOI:10.1080/104265090507641

A series of derivatives of tetrahydro-4H-pyran-4-one and tetrahydrothiopyran-4-one have been prepared by condensation with aryl Grignard reagents. IR spectra, ¹H and ¹³C NMR spectral analyses, and elemental analyses support the struc

Full text of DOI:10.1080/104265090507641

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Synthesis and Conformational
Studies of Tertiary
Alcohols Derived from
Tetrahydro-4H-pyran-4-one and
Tetrahydrothiopyran-4-one
Kevin Tran a , K. Darrell Berlin a , Elizabeth M.
Holt a , Randal Hallford b , Margaret A. Eastman c ,
Valentina K. Yu d & K. D. Praliev d
a Department of Chemistry, Oklahoma State
University , Stillwater, Oklahoma
b Department of Chemistry, Oklahoma State
University, Stillwater, Oklahoma Department of
Chemistry, Midwestern State University , Wichita
Falls, Texas
c Department of Chemistry, Oklahoma State
University , Stillwater, Oklahoma
d Institute of Chemical Sciences, Ministry of Science
and Education , Kazakhstan
Published online: 01 Feb 2007.
To cite this article: Kevin Tran , K. Darrell Berlin , Elizabeth M. Holt , Randal
Hallford , Margaret A. Eastman , Valentina K. Yu & K. D. Praliev (2005) Synthesis and
Conformational Studies of Tertiary Alcohols Derived from Tetrahydro-4H-pyran-4-
one and Tetrahydrothiopyran-4-one, Phosphorus, Sulfur, and Silicon and the Related
Elements, 180:1, 53-66, DOI: 10.1080/104265090507641
To link to this article: http://dx.doi.org/10.1080/104265090507641

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Phosphorus, Sulfur, and Silicon, 180:53–66, 2005
Copyright © Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/104265090507641
Synthesis and Conformational Studies of Tertiary
Alcohols Derived from Tetrahydro-4H-pyran-4-one
and Tetrahydrothiopyran-4-one
Kevin Tran
K. Darrell Berlin
Elizabeth M. Holt
Department of Chemistry, Oklahoma State University,
Stillwater, Oklahoma
Randal Hallford
Department of Chemistry, Oklahoma State University,
Stillwater, Oklahoma and Department of Chemistry,
Midwestern State University, Wichita Falls, Texas
Margaret A. Eastman
Department of Chemistry, Oklahoma State University,
Stillwater, Oklahoma
Valentina K. Yu
K. D. Praliev
Institute of Chemical Sciences, Ministry of Science and
Education, Kazakhstan
A series of derivatives of tetrahydro-4H-pyran-4-one and tetrahydrothiopyran-
4-one have been prepared by condensation with aryl Grignard reagents.
1
13
IR spectra, H and C NMR spectral analyses, and elemental analyses
support the structures. single-crystal X-ray diffraction analysis of 4-
A
(3,5-dimethylphenyl)tetrahydrothiopyran-4-ol [a = 9.729(10), b = 12.846(2), c =
˚
9.970(10) A; space group Pna2(1)] confirmed the aryl group is located in a pseudo
equatorial position, and the heterocyclic ring is slightly flattened near the sulfur
end of the molecule.
Keywords 1,2-Addition; Grignard reagents; NMR analysis; pyranols; thiopyranols;
X-ray data
Received April 18, 2004; accepted June 3, 2004.
Address correspondence to K. D. Berlin, Department of Chemistry, Oklahoma State
University, Stillwater, Oklahoma 74078, USA. E-mail: kdb@okstate.edu
53

54
K. Tran et al.
SCHEME 1
INTRODUCTION
A search of the literature revealed that tetrahydro-4H-pyranone (1) and
tetrahydrothiopyranone (2) have not been extensively investigated in
terms of 1,2-additions by organometallics. Ketone 1 has found use as a
synthon in the generation of part of the vitamin D3 ring A.1 Relatively
few tertiary alcohols 3 derived from ketones 1 and 2 have been recorded,
with the exception of 3g.2 The preparation of 4-t-butylthiopyran-4-ol
and 4-vinylthiopyran-4-ol have also been recently reported and appear
to possess analgesic and muscle-relaxing activities in mice.3 Herein
we report the general syntheses and conformational studies of alcohols
derivatives of ketones 1 and 2.
RESULTS AND DISCUSSION
Syntheses of alcohols 3 proceeded via condensation of ketone 1 and/or
2 with selected aryl Grignard reagents. The reactions occurred under
mild conditions in anhydrous ether or in dry THF. Workup was min-
imal, yields of alcohols 3 were good to excellent, and purification was
achieved by flash column chromatography over silica gel. Elemental
analyses and 1H and 13C NMR spectral data (Tables I and II) sup-
1
port the structures. Chemical shifts in the H and 13C NMR spectra
of compounds 3a–l were assigned partially on the basis of electroneg-
ativity effects of the heteroatoms on the protons and carbons at the
α positions. If a flattened chair is assumed for the heterocyclic ring,
the aryl group would be expected to occupy a pseudo-equatorial posi-
tion. The γ -shielding effects of groups larger than hydrogen, such as
the axial O-H group in 3, are known4 in six-member rings. Such steric
effects can induce conformational changes in such systems as reflected
in the NMR analysis.5 The configurations of the 4-pyranols were cor-
roborated by the 13C chemical shifts data (Table II). It was noted that
shielding at C4 only varied by slightly less than 2 ppm in the C-13

55

56

Alcohols Derived from Pyranones and Thiopyranones
57
FIGURE 1 The gHMQC spectra of 3j.
chemical shifts in 3. The implication is that all of the C4 carbons are
in the same environment. Similar carbons in epimeric alcohols vary
∼5 ppm.4
Alcohol 3j was selected for an in depth NMR analysis. A 2D Gradient
Heteronuclear Quantum Correlation (gHMQC) spectrum was obtained
for 3j to determine if the correlations existed between the protons and
carbons in the heterocyclic ring (Figure 1). Signal A shows a correla-
tion between C(3,5) and H(3,5)a, while B indicates a correlation of C(3,5)
and H(3,5)e. Signal C belongs to the CH3 groups. Signal D represents a
correlation between C(2,6)e and H(2,6)e while E exhibits a correlation of
C(2,6) and H(2,6)e. Both F and G are for carbons and the corresponding
hydrogens at the ortho and para positions of the aromatic ring.
1
Although the H and 13C analyses suggested a single conformer for
each alcohol with some long-range couplings being visible in individ-
1
ual patterns, a variable low-temperature H NMR analysis of 3j was
performed. The 1H spectra of 3j in CD2Cl2 were obtained at 28◦C,
0◦C, −60◦C, −78◦C, and −88◦C at 399.90 MHz. The spectra (Figure 2)
showed similar shifts and patterns at all temperatures with the ex-
ception that at −78 and −88◦C the signal for the hydroxyl proton was
shifted downfield from δ 1.45 to δ 2.62 and δ 3.82. It is well known that
the chemical shift of the OH proton is concentration dependent.6 The
possibility exists for the dimerization or trimerization of two or three
alcohol molecules in the solution at −78 and −88◦C. It was recently
reported7 that at low temperatures two or three molecules with NH
and/or OH groups may form a low-barrier hydrogen bond (Figure 3)

58
K. Tran et al.
FIGURE 2 The 1H NMR spectra of 3j at various temperatures.
which likely affects the chemical shift of the proton on the OH group.
At this time there does not appear to be another obvious argument that
is tenable to explain our result with 3j. Despite the 1H NMR analyses
suggesting a single conformer, it is not possible to eliminate a small
but dynamic equilibrium involving more than one conformer of 3j at
room temperature. It is tentatively assumed that the major conformer
FIGURE 3 The possible dimer and trimer of 3j.

Alcohols Derived from Pyranones and Thiopyranones
59
is that with the aryl group in a pseudo-equatorial position in solution.
In addition, to assure that a singlet at δ 1.45 belonged to the OH group,
a D2O-exchange experiment was conducted. The resulting spectrum
(Figure 4) shows the disappearance of a singlet peak at δ 1.45 and the
appearance of another singlet peak at δ 4.82. This proved that a singlet
at δ 1.45 belonged to OH group of 3j, and the new singlet at δ 4.82 was
for HOD.
The shape of a ring system can also be estimated from analysis of
1
vicinal H NMR coupling constants. A potentially mobile ring system
such as 3j permits the measurement of two average coupling con-
stants in a CH2 CH2 fragment, Jtrans = 0.5 (Jaa + Jee) and Jcis = 0.5
8
(Jae + Jea). The ratio R = Jtrans/Jcis was utilized to assess the nature
of the distortion present in the ring.9 In a distortion-free CH2 CH2
fragment4 of a ring, the ratio R of the average vicinal trans-coupling
constant to the average vicinal cis coupling constant is in the range
1.9–2.2.8,9 A flattening of this fragment (eclipsing of the substituents,5)
gives a lower R value while a puckered 6 increases R.8,9 The R value
is related directly to the internal dihedral angle ψ by Equation 1.8,9
Thus, an undistorted R value of 1.9–2.2 corresponds to a torsional
angle ψ of ≈56–58◦. The flattened geometry (R < 1.8) corresponds to
ψ < 55◦, and the puckered geometry (R> 2.3) corresponds to ψ > 59◦.
The calculation of distortion angles of system 3j using Equation 1 sug-
gested that the sulfur-containing ring is flattened, R (=1.07) <1.8 and
ψ = (46.3◦) <55◦.
Jtrans = J2a,3a = J2e,3e = 14.1 Hz
Jcis = J2a,3e = J2e,3a = 13.2 Hz
(1)
Jtrans
14.1 Hz
R =
=
= 1.07
Jcis
13.2 Hz
ꢀ
ꢁ
ꢀ
ꢁ
1/2
1/2
3
3
cos ψ =
=
= 0.69
2 + 4R
2 + 4(1.07)
Thereby
ψ = cos−1 0.69 = 46.3◦
For conformational purposes, an X-ray diffraction analysis was also
performed on a single crystal of 3j. The X-ray data demonstrated that
the aryl group was clearly attached to C4 at a pseudo-equatorial position
(Figure 5). The torsion angles and crystal data of heterocyclic ring 3j are
given in Tables III and IV. The sum of the theoretical torsion angles for
an alicyclic 6-member ring would be 360.0◦ if the ring were totally flat.
The total observed torsion angles in 3j is 350.1◦, indicating a flattening

60

Alcohols Derived from Pyranones and Thiopyranones
61
near the sulfur end of the molecule. From another point of view, the
plane of the base of the chair (C2-C3-C5-C6) subtends an angle of 51.8◦
with the S1-C2-C6 plane and an angle of 49.6◦ with the C3-C4-C6 plane.
The interplanar angles would each be 60◦ if the chair had theoretical
geometry. The angles are smaller, and thus the ends of the chair are
each flattened by about 10◦ from ideal.
In summary, we have prepared a series of the title compounds in
which the aryl group prefers a pseudo-equatorial position in the solid
state. NMR data implies this type of conformation may also predom-
inate in solution, perhaps due to intermolecular H-bonding involving
two or more molecules in CD2Cl2. The tertiary alcohols generated can
serve as useful synthons for a variety of heterocyclic systems. Moreover,
the physical and spectral properties of these alcohols can be important
standards for related systems.
EXPERIMENTAL
General Methods
Grignard reagents were purchased either from Rieke Metals, Inc. (1001
Kingbird Road, Lincoln, NE 68521) or from Aldrich Chemical Company
(P.O. Box 2060, Milwaukee, WI 53201). Melting points were taken on
Thomas-Hoover capillary apparatus and were uncorrected. IR spectra
TABLE III Torsion Angles of 3j
S1-C2-C3-C4
C2-C3-C4-C5
C3-C4-C5-C6
C4-C5-C6-S1
C5-C6-S1-C2
C6-S1-C2-C3
−61.3◦
−56.4◦
56.6◦
−61.4◦
57.3◦
−57.1◦
Total: 350.1◦; Theoretical: 360.0◦.

62
K. Tran et al.
FIGURE 5 Perspective view of 3j.
were recorded on a Perkin-Elmer 2000 FT-IR spectrometer as films.
1
Both H and 13C NMR spectral data were obtained on Varian Gemini
2000 High-Resolution NMR operating at 300.09 MHz and 75.46 MHz
and on a Varian Inova 400 NMR unit operating at 399.91 MHz and
100.01 MHz, respectively. The variable temperature NMR study and
2D work on 3j were performed on the Inova 400 unit. Chemical shifts
are reported as δ or ppm values. Elemental analyses were performed
by Alantic Microlab, Inc., Norcross, Georgia.
General Procedure to Obtain 3
To a solution of the appropriate Grignard reagent in a system under
N2 was added dropwise ketone 1 (0.5–5.0 g, 0.005–0.05 mol) and/or 2
(0.05–5.0 g, 0.0043–0.043 mol) in anhydrous THF (35 mL) for la,b,e,f
and/or 2g,h,k,l, respectively. The mmol ratio was 2:1 for the arylmag-
nesium bromide:monocyclic ketone. Ether was the solvent for reac-
tions involving 1c,d and 2i,j. The suspension was gently boiled (1–
3 h), was stirred overnight (RT), and was then decomposed cautiously
with aqueous 20% NH4Cl (ice bath). The mixture was extracted (ether,
3 × 100 mL), and the combined extracts were dried (K2CO3). Evapora-
tion of the solvent gave good yields of the solids all of which were purified
using “Baker” silica gel (40 µm) via flash column chromatography. The
proton and 13C NMR chemical shifts (DCCl3) are given for each alcohol
in Tables I and II (referenced to TMS).

63

64
K. Tran et al.
4-Phenyltetrahydropyran-4-ol (3a). [1 (5.0 g, 0.05 mol):PhMgBr
(0.1 mol)]. Yield: 7.83 g (88%); mp 100–100.5◦C. IR 3337 (O H), 687
and 780 (mono) cm−1. Eluant solvents: ether:hexanes (1:1). Anal. Calcd
for C11H14O2: C, 74.13; H, 7.92. Found: C, 73.89; H, 8.05.
4-(4-Chlorophenyl)tetrahydropyran-4-ol (3b). [1 (5.0 g, 0.05 mol):4-
Cl-C6H4-MgBr (0.1 mol)]. Yield: 9.96 g (94%); mp 77–78◦C. IR 3393
(O H), 828 (para) cm−1. Eluant solvents: ether:hexanes (1:1). Anal.
Calcd for C11H13ClO2: C, 62.12; H, 6.16; Cl, 16.67. Found: C, 62.37; H,
6.14; Cl, 16.71.
4-(4-N,N-Dimethylaminophenyl)tetrahydropyran-4-ol (3c). [1 (5.0
g, 0.05 mol):4-Me2N-C6H4-MgBr (0.1 mol)]. Yield: 8.50 g (77%); mp 102–
103◦C. IR 3437 (O H), 817 (para) cm−1. Eluant solvents: ether:hexanes
(1:1). Anal. Calcd for C13H19NO2: C, 70.56; H, 8.65; N, 6.33. Found: C,
70.73; H, 8.66; N, 6.21.
4-(3,5-Dimethylphenyl)tetrahydropyran-4-ol
(3d). [1 (5.0 g, 0.05
mol): 3,5-(Me)2-C6H3-MgBr (0.1 mol)]. Yield: 7.56 g (73.5%); mp
102–103◦C. IR 3387 (O H) cm−1. Eluant solvents: ether:hexanes (1:1).
Anal. Calcd for C13H18O2: C, 75.69; H, 8.80. Found: C, 75.69; H, 8.80.
4-p-Tolyltetrahydropyran-4-ol (3e). [1 (0.5 g, 0.005 mol):4-Me-C6H4-
MgBr (0.01 mol)]. Yield: 0.712 g (74%); mp 105–105.5◦C. IR 3378 (O H)
833 (para) cm−1. Recrystallization of the white solid was from ether
and petroleum ether (1:1). Anal. Calcd for C13H18O2: C, 74.97; H, 8.39.
Found: C, 74.95; H, 8.42.
4-(4-t-Butylphenyl)tetrahydropyran-4-ol (3f). [1 (0.5 g, 0.005 mol):4-
t-Bu-C6H4-MgBr (.0.01 mol)]. Yield: 0.737 g (67%); mp 285.5–286◦C.
IR 3372 (O H), 823 (para) cm−1. Recrystallization of the white solid
was from ether and petroleum ether (1:1). Anal. Calcd for C15H22O2:
C, 76.88; H, 9.46. Found: C, 76.90; H, 9.67.
4-Phenyltetrahydrothiopyran-4-ol (3g). [2 (5.0 g, 0.043 mol): Ph-
MgBr (0.086 mol)]. Yield: 6.04 g (72%) (Lit2,10 58%); mp 76–77◦C (Lit2,10
76–78◦C). IR 3337 (O H), 701 and 762 (mono) cm−1. The compound had
been recorded, but no IR and NMR data were reported.2,10 Eluant sol-
vents: ether:hexanes (1:1).
4-(4-Chlorophenyl)tetrahydrothiopyran-4-ol (3h). [2 (5.0 g, 0.043
mol):4-Cl-C6H4MgBr (0.086 mol)]. Yield: 8.89 g (91%); mp 86–87◦C. IR
3409 (O H), 862 (para) cm−1. Eluant solvents: ethyl acetate:hexanes
(1:1). Anal. Calcd for C11H13ClOS: C, 74.13; H, 7.92. Found: C, 73.89;
H, 8.05.

Alcohols Derived from Pyranones and Thiopyranones
65
4-(4-N,N-Dimethylaminophenyl)tetrahydrothiopyran-4-ol (3i). [2
(5.0 g, 0.043 mol): 4-Me2N-C6H4-MgBr (0.086 mol)]. Yield: 7.13 g (70%);
mp 110.5–112◦C. IR 3402 (O H), 813 (para) cm−1. Eluant solvents:
ethyl acetate:hexanes (3:1). Anal. Calcd for C13H19NOS: C, 65.78; H,
8.07; N, 5.90. Found: C, 65.86; H, 8.09; N, 5.82.
4-(3,5-Dimethylphenyl)tetrahydrothiopyran-4-ol (3j). [2 (5.0 g,
0.043 mol): 3,5-(Me)2-C6H3-MgBr (0.086 mol)]. Yield: 7.16 g (75%); mp
76–77.5◦C. IR 3402 (O H) cm−1. Eluant solvents: ethyl acetate:hexanes
(1:1). Anal. Calcd for C13H18OS: C, 70.22; H, 8.16. Found: C, 70.19; H,
8.22.
4-p-Tolyltetrahydrothiopyran-4-ol (3k). [2 (0.5 g, 0.0043 mol):4-Me-
C6H4-MgBr (0.0086 mol)]. Yield: 0.618 g (69%); mp 74.0–74.5◦C. IR 3413
(O H), 817 (para) cm−1. Anal. Calcd for C12H16OS: C, 69.19; H, 7.74.
Found: C, 69.20; H, 7.93.
4-(4-t-Butylphenyl)tetrahydrothiopyran-4-ol (3l). [2 (0.5 g 0.0043 mol):
4-t-Bu-C6H4-MgBr (0.0086 mol)]. Yield: 0.673 g (68%); mp 143–143.5◦C.
IR 3413 (O H), 823 (para) cm−1. Recrystallization of the white solid
was from ether and petroleum ether (1:1). Anal. Calcd for C15H22OS: C,
71.95; H, 8.86. Found: C, 71.89; H, 8.93.
Crystallographic Experimental Data for 3ja
A single crystal [orthorhombic, Pna2 (1)] of 3j (from ether:hexanes,
1:1) with dimensions 0.15 × 0.15 × 0.2 mm was mounted on a Bruker-
Siemens-Nicolet P4 diffractometer equipped with a molybdenum source
˚
(graphite monochromator, MoKα radiation, l = 0.71703 A) and a θ–2θ
data collection method (variable scan rate between 10 and 30 seconds
per degree, based upon the intensity observed per scan).a The unit
cell was determined by least squares refinement of the best angular
positions for 48 independent reflections. Data (1955 points) were col-
lected at 301 K (Table IV) and corrected for Lorentz, polarization, and
background effects.11 The intensities of three standard reflections were
monitored after every 97 reflections. Crystal decomposition was found
to be insignificant. After removal of redundant and space group forbid-
den data, atomic positions were determined with SHELXS,12 and 1150
observed data (I > 3.0 (I)) were refined using full matrix least squares
ꢂ
[function minimized, w(Fo2-Fc2)2] until convergence (SHELXL13). Hy-
drogen positions were calculated and included in the final cycles of re-
finement in constrained positions with fixed isotropic thermal param-
˚
eters and with a C H distance of 0.97 A. Absorption corrections were
aTables of all X-ray data have been deposited with the Cambridge Crystallographic
Data Centre (CCDC), United Kingdom. CCDC 242498.

66
K. Tran et al.
made using a semi-empirical method based on psi-scans. Extinction was
refined but was minimal. Molecular graphics were prepared using the
program, XP.14 The final cycle of refinement led to an agreement factor
of R = 5.39% and Rw = 9.15% with 137 parameters refined. The other
crystal data are in Table IV.
ACKNOWLEDGMENTS
We (KDB) thank the College of Arts and Sciences of the Oklahoma
State University for partial support of this work. We (VKY and KDB)
gratefully acknowledge and thank the U.S. Civilian R&D Foundation
(CRDF) for the Independent States of the Former Soviet Union for par-
tial support of this research (grant KC2-2288). We also thank the Na-
tional Science Foundation (BIR-9512269), the Oklahoma State Regents
for Higher Education, the W. M. Keck Foundation, and Conoco, Inc. for
funds to purchase the 300, 400, and 600 MHz NMR spectrometers. We
dedicate this work to the memory of Dr. Elizabeth M. Holt.
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