A concise, Novel Route to 1,3-benzoxathian derivatives

Article abstract of DOI:10.1055/s-0029-1217016

Novel 1,3-benzoxathian derivatives were successfully prepared in a one-pot process via a tandem ring-closure/β-elimination pathway from easily accessible o-thio-substituted phenols. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-0029-1217016

3848
PAPER
A Concise, Novel Route to 1,3-Benzoxathian Derivatives
Synthesis and Use of
1
i
, 3-Be
n
c
zoxathian D
h
erivatives èle Gerster,* Manuel Mihalic
Ciba Inc., CH-4002, Basel, Switzerland
Fax +41(61)6362969; E-mail: michele.gerster@ciba.com
Received 7 April 2009; revised 4 August 2009
followed by basic hydrolysis, resulted in the formation of
2-mercaptomethylphenol derivatives.4
Abstract: Novel 1,3-benzoxathian derivatives were successfully
prepared in a one-pot process via a tandem ring-closure/b-elimina-
tion pathway from easily accessible o-thio-substituted phenols.
Finally, the thiomethylation of phenols with N,N′-dicy-
clohexylcarbodiimide (DCC) and dimethyl sulfoxide
(DMSO), in the presence of acidic catalysts, yields a vari-
ety of product types, including trace amounts of 1,3-benz-
oxathians in addition to the expected o- and p-
thiomethoxymethyl-substituted phenols.5,6
Key words: 1,3-Benzoxathian, annulation, phenols, ring-closure,
elimination
Few direct synthetic routes are available for the synthesis
of 1,3-benzoxathian ring systems. Among the known
methods, cycloaddition and acetalization approaches suf-
fer because of the limited range of substituent diversity
that can be used. Eguchi used essentially thiobenzophe-
none as the heterodienophile partner for a [4+2] cyclo-
addition reaction with o-benzoquinone methanides,1
whereas, inversely, electron-deficient carbonyl com-
pounds were used to trap the diene formed in situ upon
thermal ring-opening of benzothiete to afford 1,3-benz-
oxathiins in low to high yields (Scheme 1).2
In the present paper we wish to report a novel and im-
proved synthetic approach to 1,3-benzoxathian deriva-
tives which converts the easily accessible o-thio-
substituted phenols to 1,3-benzoxathian derivatives in a
one-pot process (Scheme 2).7 The transformation of 1 into
3 when we applied the reaction conditions developed for
the synthesis of aromatic formal was unexpected.8 Indeed,
when 1 was allowed to react under optimized conditions
(five equivalents of diiodomethane and five equivalents of
NaOH, in sulfolane, at room temperature), 3 could be iso-
lated in high yields, selectively, in preference to the ex-
pected intermolecular O,O-acetals 4 provided a judicious
choice of the electron-withdrawing group X was made
(Table 1). When X was a butyl ester substituent, the 1,3-
benzoxathians were produced exclusively, whereas with
phenols containing the less strongly electron-withdrawing
perfluorinated alkyl chain, the b-elimination was less
favoured and additional steric hindrance was mandatory
in the o-position of the phenol in order to direct the reac-
tion preferentially towards formation of the 1,3-benz-
oxathian derivatives over 4.
S
O
OH
R1
R2
R1
R2
O
S
dry xylene
sealed tube
OH
S
180 °C, 20 h
argon
O
S
S
R1
R2
R1
R2
Δ
O
4–91%
Scheme 1 Synthesis of 1,3-benzoxathian and 1,3-benzoxathiin via
[4+2] cycloaddition
The key to the success of our synthetic approach relies on
the presence of the electron-withdrawing group in the b-
position to sulfur. This substitution is mandatory in the
starting material as it allows the sulfonium intermediate 2
to undergo deprotonation, which releases the activated vi-
The direct route to cyclic thioketals via acetalization of
ketones with suitable 2-mercaptomethylphenol deriva-
tives is limited due to the long reaction sequences neces-
sary to obtain the starting substrate. Arnoldi3 described Table 1 Synthesis of 1,3-Benzoxathian Derivatives 3
the preparation of 2-mercaptomethylphenol from 2-meth-
ylphenol by a sequence of acetylation, bromination of the
benzylic position, reaction under phase-transfer condi-
R1
X
1
3
Yield of 3 3:4a
(%)
tions with sodium hydrogen sulfide and hydrolysis under Me
CO2Bu
C4F9
a
b
c
d
e
f
a
a
b
b
c
78
35
73
67
66
–
100:0
37:63
100:0
82:18
100:0
68:32
alkaline conditions. Another sequence from an o-formyl
methylphenylether involves demethylation and reduction
Me
to afford the o-hydroxymethylphenol which, upon stan-
t-Bu
CO2Bu
C4F9
dard Mitsunobu reaction conditions with thioacetic acid
t-Bu
CH2S(CH2)2CO2Bu
CH2S(CH2)2C4F9
a GC ratio.
CO2Bu
C4F9
SYNTHESIS 2009, No. 22, pp 3848–3852
Advanced online publication: 23.09.2009
DOI: 10.1055/s-0029-1217016; Art ID: T07109SS
© Georg Thieme Verlag Stuttgart · New York
x
x.
x
x
.
2
0
0
9
d

PAPER
Synthesis and Use of 1,3-Benzoxathian Derivatives
3849
X
S
X
X
HS
X
I–
S+
O
OH
(HCHO)n
Me2NH
X
OH
S
CH2I2 (5 equiv)
NaOH (5 equiv)
O
S
R1
R1
O
R1
S
O
R1
R1
R1
+
DMF
sulfolane
r.t.
1a–f
2a–f
3a–d
4a–d
Scheme 2 Synthesis of 1,3-benzoxathian derivatives 3
nyl compounds, leading to the formation of the 1,3-benz- tivities in melt-processing of PP were characterized using
oxathian derivative 3. The concomitant formation of the MFI of multiple-extruded PP stabilized with the additive.
acrylate was detectable by 1H NMR spectroscopy. In the The smaller the MFI value of the corresponding extrusion
absence of an electron-withdrawing group, such as in 2,4- pass, the better is the antioxidant activity. The results,
dimethyl-6-octylsulfanylmethylphenol, the only product summarized in Table 3, show that the three compounds
formed was the intermolecular O,O-acetal in 88% yield.
examined function as highly efficient processing stabiliz-
ers.10
The method also proved suitable for the reaction of the
easily accessible thioarylated phenol starting materials 5,7 In conclusion, we have developed a novel route to the
which reacted with complete selectivity to give the 1,3- construction of the bicyclic framework of 1,3-benzoxa-
benzoxathian derivatives 7 (Scheme 3 and Table 2). The thian, via a tandem ring-closure/b-elimination pathway of
use of benzal chloride instead of diiodomethane led to the thiomethylated and thioarylated phenols in the presence
formation of a diastereoisomeric mixture of the 2,4-diphe- of a bis-halogenated reagent under base catalysis.
nyl-1,3-benzoxathian derivative 7c in 38% yield
(Table 2).
Table 3 Effect as Processing Stabilizer
Table 2 Synthesis of 1,3-Benzoxathian Derivatives 7
Additive (0.02%)
Mp (°C)
103–104
MFI of PPa
69.0
R1
X
R2
H
5
a
b
c
6
7
a
b
b
c
Yield of 7 (%)
–
Me
CO2Bu
CO2Bu
C4F9
CH2I2
CH2I2
CH2I2
PhCHCl2
86
58
52
38
7a
17.7
t-Bu
t-Bu
t-Bu
H
O
O
S
H
226–229
14.8
CO2Bu
Ph
b
As for the methylthiomethyl phenol derivatives,9 the
novel 1,3-benzoxathian derivative 7a and its correspond-
ing sulfoxide 8 and sulfone 9 derivatives obtained via so-
dium periodate and 3-chloroperoxybenzoic acid oxidation
of 7a, respectively, also possessed radical scavenging ac-
tivity. Used during polymer processing, such additives
provide stability to the polymers, against oxidative, ther-
mal or light-induced degradation. In the case of polypro-
pylene (PP), chain scission of the macromolecules results
in a decrease in the molecular weight of the PP and leads
to an increase in the melt flow index (MFI). So the
thermo-oxidative and thermo-mechanical antioxidant ac-
8
O
S
O
O
195–197
20.3
9
a PP (Moplen HF 500 N) after three extrusions.
R2
X
S
OH
O
S
OH
N
6 (5 equiv)
NaOH (5 equiv)
R1
R1
X
R1
HS
sulfolane
r.t.
toluene
140 °C
R1
R1
7a–c
R1
5a–c
Scheme 3 Synthesis of 1,3-benzoxathian derivatives 7
Synthesis 2009, No. 22, 3848–3852 © Thieme Stuttgart · New York

3850
M. Gerster, M. Mihalic
PAPER
13C NMR (100 MHz, CDCl3): d = 149.9 (C), 130.4 (CH), 129.2 (C),
127.5 (C), 127.2 (CH), 118.7 (C), 68.9 (CH2), 28.7 (CH2), 20.3
(CH3), 16.0 (CH3).
GCMS (EI): m/z (%) = 180 (75) [M+], 165 (6), 135 (9), 134 (81),
106 (47), 91 (100), 77 (11).
IR spectra were recorded on a Nicolet-Magna-IR™ spectrometer
750. The NMR spectra were recorded in CDCl3, with shifts (d) giv-
1
en relative to residual protonated solvent (d = 7.26 ppm) for H
NMR, and relative to CDCl3 (d = 77 ppm) for 13C NMR, on a Bruker
ACS 120 spectrometer at 300 MHz for 1H and 75 MHz for 13C, or
on a Bruker ACS 60 spectrometer at 400 MHz for 1H and 100 MHz
for 13C. The melting points were determined on a Büchi 540 capil-
lary apparatus and are not corrected. The EI mass spectra were mea-
sured by GC-MS (Thermo Electron Corporation TRACE GC
Ultra™ gas chromatograph with a Thermo Electron Corporation
PolarisQ ion-trap mass spectrometer) or by direct introduction
(DEP). The APCI mass spectra were measured by LC-MS (Waters-
Micromass ZQ). The ESI-HRMS were measured on a QSTAR XL
spectrometer operated in positive ion mode. Microanalyses were
obtained using a LECO-CHNS-932 element analyser und a LECO-
RO-478 element analyser.
Anal. Calcd for C10H12OS: C, 66.63; H, 6.71; O, 8.88; S, 17.79.
Found: C, 66.23; H, 6.72; O, 8.94; S, 17.85.
8-tert-Butyl-6-methyl-1,3-benzoxathian (3b)
Colourless liquid.
IR (neat): 2959, 2912, 1469, 1202, 1137, 1015, 874, 852, 794, 738,
714, 652 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.01 (s, 1 H, ArH), 6.76 (s, 1 H,
ArH), 5.27 (s, 2 H, OCH2S), 3.93 (s, 2 H, ArCH2), 2.28 (s, 3 H,
CH3), 1.39 (s, 9 H, t-Bu).
13C NMR (100 MHz, CDCl3): d = 150.9 (C), 139.2 (C), 129.2 (C),
127.9 (CH), 126.6 (CH), 119.5 (C), 68.1 (CH2), 34.9 (C), 30.0
(CH3), 28.8 (CH2), 20.8 (CH3).
GCMS (EI): m/z (%) = 222 (62) [M+], 207 (17), 176 (20), 161
(100), 143 (11), 133 (31), 91 (17), 77 (7).
Butyl 3-(2-Hydroxy-3,5-dimethylbenzylsulfanyl)propionate
(1a); Typical Procedure
2,4-Dimethylphenol (16.5 g, 135 mmol), butyl 3-mercaptopropio-
nate (21.9 g, 21.9 mL, 135 mmol), dimethylamine (33% in EtOH;
0.61 g, 0.80 mL, 0.14 mmol), paraformaldehyde (8.11 g, 270 mmol)
and DMF (5.00 mL) were mixed and heated under reflux for 2 h un-
der a nitrogen atmosphere. EtOAc (200 mL) was added and the or-
ganic phase was washed repeatedly with H2O and brine until neutral
pH. The organic phase was then dried over MgSO4, filtered and
concentrated using a vacuum rotary evaporator to give a pale-
yellow liquid (61.3 g). The crude product was purified by flash
chromatography (hexane–EtOAc, 9:1) to give 1a.
Anal. Calcd for C13H18OS: C, 70.22; H, 8.16; O, 7.20; S, 14.42.
Found: C, 70.01; H, 8.12; O, 7.50; S, 14.17.
Butyl 3-(6-Methyl-4H-1-oxa-3-thianaphthalen-8-ylmethylsulfa-
nyl)propionate (3c)
Colourless liquid.
IR (neat): 2957, 1929, 1728, 1474, 1244, 1199, 1136, 1013, 876,
845, 740, 706 cm–1.
Yield: 39.2 g (98%); colourless liquid.
IR (neat): 3459, 2958, 1731, 1485, 1241, 1192, 857 cm–1.
1H NMR (300 MHz, CDCl3): d = 6.91 (s, 1 H, ArH), 6.77 (s, 1 H,
ArH), 6.27 (s, 1 H, OH), 4.12 (t, J = 6.6 Hz, 2 H, CO2CH2), 3.80 (s,
2 H, ArCH2S), 2.78–2.55 (m, 4 H, SCH2CH2CO2), 2.24 (s, 6 H,
ArCH3), 1.70–1.55 (m, 2 H, CO2CH2CH2), 1.50–1.40 (m, 2 H,
CO2CH2CH2CH2), 0.96 (t, J = 7.2 Hz, 3 H, CH3).
1H NMR (300 MHz, CDCl3): d = 6.99 (s, 1 H, ArH), 6.78 (s, 1 H,
ArH), 5.28 (s, 2 H, OCH2S), 4.20–4.05 (t, J = 6.6 Hz, 2 H,
CO2CH2), 3.82 (s, 2 H, ArCH2S), 3.63 (s, 2 H, ArCH2S), 2.85–2.55
(m, 4 H, SCH2CH2CO2), 2.26 (s, 3 H, ArCH3), 1.80–1.55 (m, 2 H,
CO2CH2CH2), 1.50–1.30 (m, 2 H, CO2CH2CH2CH2), 0.95 (t,
J = 7.2 Hz, 3 H, CH3).
13C NMR (100 MHz, CDCl3): d = 172.0 (C), 151.1 (C), 131.2 (CH),
129.2 (C), 128.6 (CH), 125.6 (C), 121.5 (C), 64.7 (CH2), 34.4
(CH2), 32.9 (CH2), 30.6 (CH2), 25.9 (CH2), 20.4 (CH3), 19.1 (CH2),
15.8 (CH3), 13.7 (CH3).
GCMS (EI): m/z (%) = 296 (11) [M+], 222 (30), 168 (5), 135 (100),
134 (39), 106 (28), 91 (83), 79 (19).
13C NMR (100 MHz, CDCl3): d = 172.2 (C), 149.4 (C), 130.0 (CH),
129.6 (C), 128.9 (CH), 127.6 (C), 119.3 (C), 69.0 (CH2), 64.5
(CH2), 34.8 (CH2), 30.7 (CH2), 29.9 (CH2), 28.7 (CH2), 26.7 (CH2),
20.4 (CH3), 19.2 (CH2), 13.7 (CH3).
GCMS (EI): m/z (%) = 340 (7) [M+], 180 (44), 179 (63), 178 (100),
165 (50), 133 (77), 105 (25), 77 (15).
HRMS (ESI): m/z [M + Na+] calcd for C17H24O3S2Na: 363.1065;
found: 363.1101.
Anal. Calcd for C16H24O3S: C, 64.83; H, 8.16; O, 16.19; S, 10.82.
Found: C, 64.63; H, 7.80; O, 16.25; S, 11.16.
6,8-Dimethyl-1,3-benzoxathian (3a); Typical Procedure
Butyl 3-(2-hydroxy-3,5-dimethylbenzylsulfanyl)propionate (1a;
65.2 g, 0.22 mol) was dissolved in sulfolane (0.80 L) and CH2I2
(295 g, 88.7 mL, 1.10 mol) was added at 35 °C, followed by the ad-
dition of pulverized NaOH (22.0 g, 0.55 mol). The reaction was
stirred at r.t. for 3.5 h then at 40 °C for 2 h. Hexane (250 mL) was
added and the organic phase was washed repeatedly with H2O and
brine until neutral pH. The organic phase was dried over MgSO4,
filtered and concentrated using a vacuum rotary evaporator to give
a yellow liquid (250 g). The volatiles were distilled off through a
Vigreux column under vacuum (0.06 mbar; oil bath temperature:
90–110 °C) and then the product (0.06 mbar; oil bath temperature:
140–200 °C) to give 3a.
6-Methyl-8-(3,3,4,4,5,5,6,6,6-nonafluorohexylsulfanylmethyl)-
1,3-benzoxathian (3d)
Pale-yellow liquid.
IR (neat): 2924, 1475, 1351, 1214, 1130, 1009, 877, 845, 745, 706
cm–1.
1H NMR (300 MHz, CDCl3): d = 6.97 (s, 1 H, ArH), 6.81 (s, 1 H,
ArH), 5.27 (s, 2 H, OCH2S), 3.88 (s, 2 H, ArCH2S), 3.72 (s, 2 H,
ArCH2S), 2.75–2.55 (m, 2 H, SCH2CH2CF2), 2.45–2.20 (m, 2 H,
SCH2CH2CF2), 2.26 (s, 3 H, CH3).
13C NMR (100 MHz, CDCl3): d = 149.4 (C), 130.0 (CH), 129.7 (C),
129.1 (CH), 127.1 (C), 119.5 (C), 69.0 (CH2), 32.0 (t, 2JC,F = 22 Hz,
CH2CF2), 29.9 (CH2), 28.7 (CH2), 22.0 (CH2), 20.3 (CH3).
Yield: 31.2 g (78%); white solid; mp 46–48 °C.
GCMS (EI): m/z (%) = 458 (34) [M+], 179 (100), 165 (27), 133
IR (neat): 2948, 1481, 1202, 1146, 1012, 869, 855, 767, 743, 721,
703 cm–1.
1H NMR (400 MHz, CDCl3): d = 6.88 (s, 1 H, ArH), 6.73 (s, 1 H,
ArH), 5.29 (s, 2 H, OCH2S), 3.89 (s, 2 H, ArCH2), 2.25 (s, 3 H,
CH3), 2.18 (s, 3 H, CH3).
(77), 105 (27), 77 (16).
Anal. Calcd for C16H15F9OS2: C, 41.92; H, 3.30; O, 3.49; S, 13.99.
Found: C, 41.91; H, 3.42; O, 3.70; S, 14.29.
Synthesis 2009, No. 22, 3848–3852 © Thieme Stuttgart · New York

PAPER
Synthesis and Use of 1,3-Benzoxathian Derivatives
3851
Bis[4-methyl-2,6-bis-(3,3,4,4,5,5,6,6,6-nonafluorohexylsulfanyl-
methyl)phenoxy]methane (4d)
MS (EI): m/z (%) = 416 (3) [M+], 295 (22), 294 (100), 293 (88), 279
(39), 237 (9), 91 (9).
Yellow liquid.
Anal. Calcd for C28H32OS: C, 80.72; H, 7.74; O, 3.84; S, 7.70.
Found: C, 80.42; H, 7.66; O, 3.85; S, 7.44.
IR (neat): 2931, 1476, 1355, 1203, 1127, 1074, 965, 845, 749, 697
cm–1.
7c; Minor Diastereoisomer
Pale-yellow solid; mp 120–125 °C.
IR (neat): 2947, 2901, 1438, 1246, 1004, 882, 727, 709, 698 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.08 (s, 4 H, ArH), 5.52 (s, 2 H,
OCH2O), 3.80 (s, 8 H, ArCH2S), 2.75–2.60 (m, 8 H, SCH2CH2),
2.40–2.20 (m, 14 H, SCH2CH2 and CH3).
13C NMR (100 MHz, CDCl3): d = 150.7 (C), 135.2 (C), 131.5 (C),
1H NMR (300 MHz, CDCl3): d = 7.55–7.45 (m, 2 H, ArH), 7.45–
7.15 (m, 9 H, ArH), 6.93 (s, 1 H, ArH), 5.95 (s, 1 H, OCHS), 5.30
(s, 1 H, ArCHAr), 1.45 (s, 9 H, t-Bu), 1.29 (s, 9 H, t-Bu).
2
130.8 (CH), 101.2 (CH2), 31.7 (t, JC,F = 22 Hz, CH2CF2), 31.1
(CH2), 22.5 (CH2), 20.6 (CH3).
HPLCMS (APCI): m/z (%) = 1397 (40) [M + H+], 705 (100).
13C NMR (100 MHz, CDCl3): d = 151.7 (C), 145.2 (C), 142.4 (C),
138.7 (C), 138.0 (C), 128.61 (CH), 128.58 (CH), 128.4 (CH), 128.3
(CH), 126.9 (CH), 126.7 (CH), 125.5 (CH), 123.6 (CH), 119.6 (C),
77.5 (CH), 46.5 (CH), 35.4 (C), 34.3 (C), 31.5 (CH3), 30.2 (CH3).
+
HRMS (ESI): m/z [M + NH4 ] calcd for C43H40F36O2NS4:
1414.1367; found: 1414.1293.
6,8-Dimethyl-4-phenyl-1,3-benzoxathian (7a)
Pale-yellow solid; mp 103–104 °C.
MS (EI): m/z (%) = 416 (4) [M+], 295 (23), 294 (100), 293 (85), 279
(38), 237 (6), 91 (6).
IR (neat): 2971, 1479, 1203, 1146, 1008, 866, 791, 725, 700, 693
cm–1.
Anal. Calcd for C28H32OS: C, 80.72; H, 7.74; O, 3.84; S, 7.70.
Found: C, 80.61; H, 7.71; O, 3.90; S, 7.60.
1H NMR (400 MHz, CDCl3): d = 7.65–7.10 (m, 5 H, ArH), 6.97 (s,
1 H, ArH), 6.63 (s, 1 H, ArH), 5.31 (d, J = 11.2 Hz, 1 H, OCHHS),
5.24 (s, 1 H, ArCHAr), 5.12 (d, J = 11.2 Hz, 1 H, OCHHS), 2.28 (s,
3 H, CH3), 2.22 (s, 3 H, CH3).
13C NMR (100 MHz, CDCl3): d = 150.1 (C), 143.5 (C), 131.0 (CH),
129.1 (C), 128.8 (CH), 128.4 (CH), 128.3 (CH), 127.5 (C), 127.2
(CH), 120.7 (C), 65.3 (CH2), 44.0 (CH), 20.4 (CH3), 16.4 (CH3).
6,8-Dimethyl-4-phenyl-4H-1-oxa-3-thianaphthalene-3-oxide (8)
White solid; mp 226–229 °C.
IR (neat): 2947, 1479, 1452, 1209, 1148, 1029, 866, 799, 743, 715,
695, 665 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.45–7.30 (m, 3 H, ArH), 7.25–
7.15 (m, 2 H, ArH), 7.04 (s, 1 H, ArH), 6.71 (s, 1 H, ArH), 5.31 (s,
1 H, ArCHAr), 5.04 (d, J = 11.1 Hz, 1 H, OCHHSO), 4.66 (d,
J = 11.1 Hz, 1 H, OCHHSO), 2.34 (s, 3 H, CH3), 2.24 (s, 3 H, CH3).
13C NMR (100 MHz, CDCl3): d = 148.3 (C), 135.8 (C), 132.1 (CH),
131.7 (C), 130.3 (CH), 129.7 (CH), 129.2 (CH), 128.6 (CH), 127.0
(C), 114.2 (C), 72.5 (CH2), 63.8 (CH), 20.5 (CH3), 16.3 (CH3).
GCMS (EI): m/z (%) = 256 (11) [M+], 210 (49), 209 (100), 195
(12), 165 (13), 77 (2).
Anal. Calcd for C16H16OS: C, 74.96; H, 6.29; O, 6.24; S, 12.51.
Found: C, 74.77; H, 6.45; O, 6.29; S, 12.32.
6,8-Di-tert-butyl-4-phenyl-1,3-benzoxathian (7b)
White solid; mp 122–124 °C.
GCMS (EI): m/z (%) = 256 (4) [M+ – O], 210 (49), 209 (100), 195
(9), 165 (11).
IR (neat): 2952, 1491, 1475, 1130, 1021, 881, 795, 756, 747, 720,
696, 676 cm–1.
Anal. Calcd for C16H16O2S: C, 70.56; H, 5.92; O, 11.75; S, 11.77.
Found: C, 70.30; H, 6.15; O, 11.71; S, 11.81.
1H NMR (300 MHz, CDCl3): d = 7.30–7.10 (m, 6 H, ArH), 6.70 (d,
J = 2.4 Hz, 1 H, ArH), 5.20 (d, J = 10.8 Hz, 1 H, OCHHS), 5.18 (s,
1 H, ArCHAr), 4.97 (d, J = 10.8 Hz, 1 H, OCHHS), 1.35 (s, 9 H, t-
Bu), 1.14 (s, 9 H, t-Bu).
6,8-Dimethyl-4-phenyl-4H-1-oxa-3-thianaphthalene-3,3-di-
oxide (9)
White solid; mp 195–197 °C.
IR (neat): 2948, 1480, 1320, 1305, 1125, 1061, 928, 855, 763, 738,
703 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.50–7.40 (m, 3 H, ArH), 7.40–
7.30 (m, 2 H, ArH), 7.01 (s, 1 H, ArH), 6.54 (s, 1 H, ArH), 5.47 (s,
1 H, ArCHAr), 5.01 (d, J = 12.0 Hz, 1 H, OCHHSO2), 4.93 (d, J =
12.0 Hz, 1 H, OCHHSO2), 2.31 (s, 3 H, CH3), 2.20 (s, 3 H, CH3).
13C NMR (100 MHz, CDCl3): d = 148.5 (C), 133.1 (C), 132.3 (CH),
131.7 (C), 131.0 (CH), 129.4 (CH), 128.8 (CH), 128.8 (CH), 128.0
(C), 119.6 (C), 77.2 (CH2), 67.8 (CH), 20.5 (CH3), 16.2 (CH3).
13C NMR (100 MHz, CDCl3): d = 150.8 (C), 143.9 (C), 142.0 (C),
138.4 (C), 128.8 (CH), 128.3 (CH), 127.1 (CH), 125.4 (CH), 123.5
(CH), 120.6 (C), 64.5 (CH2), 44.5 (CH), 35.3 (C), 34.2 (C), 31.5
(CH3), 30.1 (CH3).
GCMS (EI): m/z (%) = 340 (12) [M+], 294 (100), 293 (95), 280
(12), 279 (51), 237 (9), 91 (13).
Anal. Calcd for C22H28OS: C, 77.60; H, 8.29; O, 4.70; S, 9.42.
Found: C, 77.54; H, 8.29; O, 4.66; S, 9.18.
6,8-Di-tert-butyl-2,4-diphenyl-1,3-benzoxathian (7c); Major
Diastereoisomer
Pale-yellow solid; mp 161–164 °C.
GCMS (EI): m/z (%) = 224 (100) [M+ – SO2], 223 (45), 209 (72),
195 (25), 181 (55), 166 (35), 165 (45), 152 (17), 115 (16), 91 (9), 77
(8).
IR (neat): 2959, 1436, 1262, 1225, 1020, 882, 703, 697 cm–1.
Anal. Calcd for C16H16O3S: C, 66.64; H, 5.59; O, 16.64; S, 11.12.
Found: C, 66.67; H, 5.51; O, 16.83; S, 11.03.
1H NMR (300 MHz, CDCl3): d = 7.65–7.50 (m, 2 H, ArH), 7.45–
7.00 (m, 9 H, ArH), 6.64 (s, 1 H, ArH), 6.30 (s, 1 H, OCHS), 5.69
(s, 1 H, ArCHAr), 1.33 (s, 9 H, t-Bu), 1.07 (s, 9 H, t-Bu).
13C NMR (100 MHz, CDCl3): d = 152.2 (C), 142.5 (C), 141.3 (C),
138.8 (C), 137.9 (C), 129.1 (CH), 128.8 (CH), 128.60 (CH), 128.58
(CH), 127.7 (CH), 126.5 (CH), 124.4 (CH), 123.5 (C), 122.9 (CH),
82.8 (CH), 48.9 (CH), 35.3 (C), 34.3 (C), 31.4 (CH3), 30.2 (CH3).
Acknowledgment
We wish to thank Dr B. Rotzinger for PP-stabilization measure-
ments and Dr A. W. Thomas for useful comments during the prepa-
ration of the manuscript.
Synthesis 2009, No. 22, 3848–3852 © Thieme Stuttgart · New York

3852
M. Gerster, M. Mihalic
PAPER
(6) For discussions on the mechanism, see: (a) Olofson, R. A.;
Marino, J. P. Tetrahedron 1971, 27, 4195. (b) Marino, J. P.;
Pfitzner, K. E.; Olofson, R. A. Tetrahedron 1971, 27, 4181.
(7) Pizzoli, F.; Luisoli, R.; Knobloch, G.; Meier, H.-R. EP
Patent 1116714A1, 2001; Chem. Abstr. 2001, 135, 95009.
(8) Heuer, H.-W.; Wehrmann, R.; Bruder, F.-K. US Patent
0090593, 2005; Chem. Abstr. 2005, 142, 280926.
(9) Moffat, J. G. US Patent 3457315, 1969; Chem. Abstr. 1970,
72, 90051.
(10) PP powder (1.3 kg) was blended with Irganox 1010 (0.05%),
calcium stearate (0.05%), Irgafos 168 (0.02%) and the 1,3-
benzoxathian derivative (0.02%). The blend was extruded in
an extruder having a cylinder diameter of 20 mm and a
length of 400 mm at 100 rpm. The three heating zones being
adjusted to the following temperatures: 260, 270 and 280 °C.
The extrudate was cooled down, granulated and extruded
again. After three extrusions, the MFI was measured at
230 °C/2.16 kg.
References
(1) Katada, T.; Eguchi, S.; Esaki, T.; Sasaki, T. J. Chem. Soc.,
Perkin Trans. 1 1984, 2649.
(2) Page, P. C. B.; Lund, A. Comprehensive Heterocyclic
Chemistry II, Vol. 6; Katrizky, A. R.; Rees, C. W.; Scriven,
E. F. V., Eds.; Pergamon: Oxford, 1996, 415–445.
(3) Arnoldi, A.; Bassoli, A.; Merlini, L.; Ragg, E. J. Chem. Soc.,
Perkin Trans. 1 1993, 1359.
(4) Magnus, P.; Mitchell, I. S. Tetrahedron Lett. 1998, 39, 9131.
(5) (a) Burdon, M. G.; Moffatt, J. G. J. Am. Chem. Soc. 1965, 87,
4656. (b) Burdon, M. G.; Moffatt, J. G. J. Am. Chem. Soc.
1965, 87, 4658. (c) Burdon, M. G.; Moffatt, J. G. J. Am.
Chem. Soc. 1966, 88, 5855. (d) Hayashi, Y.; Oda, R. J. Org.
Chem. 1967, 32, 457. (e) Burdon, M. G.; Moffatt, J. G.
J. Am. Chem. Soc. 1967, 89, 4725.
Synthesis 2009, No. 22, 3848–3852 © Thieme Stuttgart · New York