Structure and thermal reactivity of some 2-substituted 1,3-oxathiolane S-oxides

Article abstract of DOI:10.1080/17415993.2018.1449844

Isomerization of 2-benzylidene-1,3-dioxolane to 3-phenylbutyrolactone occurs readily under flash vacuum pyrolysis (FVP) conditions. 2-Diphenylmethyl-1,3-oxathiolane and 2-benzyl-1,3-oxathiolane have been prepared and the latter compound has been oxidized to the corresponding sulfoxide, whose structure and conformation are examined by ¹H NMR, and to the sulfone whose X-ray structure is determined. 2-Benzylidene-1,3-oxathiolane is also prepared and the behavior of the three S-oxidized oxathiolane derivatives upon FVP is examined. While extrusion of SO_n to give ethene and a carbonyl compound predominates in all three cases, the sulfoxide gives also bis(2-hydroxyethyl) disulfide, most likely formed via thiirane S-oxide and 1,2-oxathietane.

Full text of DOI:10.1080/17415993.2018.1449844

Journal of Sulfur Chemistry
ISSN: 1741-5993 (Print) 1741-6000 (Online) Journal homepage: http://www.tandfonline.com/loi/gsrp20
Structure and thermal reactivity of some 2-
substituted 1,3-oxathiolane S-oxides
R. Alan Aitken, Sarah Henderson & Alexandra M. Z. Slawin
To cite this article: R. Alan Aitken, Sarah Henderson & Alexandra M. Z. Slawin (2018): Structure
and thermal reactivity of some 2-substituted 1,3-oxathiolane S-oxides, Journal of Sulfur Chemistry,
DOI: 10.1080/17415993.2018.1449844
To link to this article: https://doi.org/10.1080/17415993.2018.1449844
View supplementary material
Published online: 20 Mar 2018.
Submit your article to this journal
Article views: 22
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at
http://www.tandfonline.com/action/journalInformation?journalCode=gsrp20

JOURNAL OF SULFUR CHEMISTRY, 2018
https://doi.org/10.1080/17415993.2018.1449844
Structure and thermal reactivity of some 2-substituted
1,3-oxathiolane S-oxides
R. Alan Aitken, Sarah Henderson and Alexandra M. Z. Slawin
EaStCHEM School of Chemistry, University of St Andrews, St Andrews, UK
ABSTRACT
ARTICLE HISTORY
Received 1 December 2017
Accepted 4 March 2018
Isomerization of 2-benzylidene-1,3-dioxolane to 3-phenylbutyrola-
ctoneoccursreadilyunderflashvacuumpyrolysis(FVP)conditions. 2-
Diphenylmethyl-1,3-oxathiolane and 2-benzyl-1,3-oxathiolane have
been prepared and the latter compound has been oxidized to
the corresponding sulfoxide, whose structure and conformation are
KEYWORDS
1,3-Oxathiolane; pyrolysis;
sulfoxide; sulphone; X-ray
structure
1
examined by H NMR, and to the sulfone whose X-ray structure is
determined. 2-Benzylidene-1,3-oxathiolane is also prepared and the
behavior of the three S-oxidized oxathiolane derivatives upon FVP
is examined. While extrusion of SOn to give ethene and a carbonyl
compound predominates in all three cases, the sulfoxide gives also
bis(2-hydroxyethyl) disulfide, most likely formed via thiirane S-oxide
and 1,2-oxathietane.
1. Introduction
There has recently been increased interest in the use of gas-phase pyrolysis methods in
the synthesis of heterocyclic compounds [1]. Sometime ago, Oda and coworkers described
the thermal conversion of 2-benzylidene-1,3-dioxolanes such as 1 and 2 (Scheme 1) into
the corresponding 3-phenylbutyrolactones 3 and 4 [2]. However, they used flow pyroly-
sis with the substrates introduced in benzene solution and carried through the furnace at
atmospheric pressure by a stream of nitrogen gas. We were interested to re-examine this
reaction under the more convenient and commonly used FVP conditions, and more impor-
tantly try to extend it to the 1,3-oxathiolane analogues (Scheme 2). We were aware of the
possibility of SO or SO2 extrusion intervening in these processes.
CONTACT R. Alan Aitken
raa@st-and.ac.uk
EaStCHEM School of Chemistry, University of St Andrews, St
Andrews, UK
Supplemental data for this article can be accessed here. https://doi.org/10.1080/17415993.2018.1449844
© 2018 Informa UK Limited, trading as Taylor & Francis Group

2
R. A. AITKEN ET AL.
Scheme 1. Thermal conversion of 2-benzylidene-1,3-dioxolanes into 2-phenylbutyrolactones [2].
Scheme 2. Possible thermal rearrangement of 1,3-oxathiolane systems.
2. Results and discussion
The synthesis of 1 was first carried out using the reported methods (Scheme 3) [3,4] and
gave excellent yields of products which showed the expected NMR data although, due
to the early date of the previous work, spectroscopic data were lacking for the interme-
diates in this pathway. Both α-bromophenylacetaldehyde dimethyl acetal [3] and 2-(α-
bromobenzyl-1,3-dioxolane [5] gave 1H NMR data in agreement with the previous reports,
while their 13C NMR data were recorded for the first time, and for the target product 1
neither 1H nor 13C NMR data appear to have been previously reported. When compound
1 was subjected to FVP in a conventional flow system at a pressure of 10–2 Torr with an
estimated contact time of 10 ms, complete reaction was observed with a furnace temper-
ature of 600°C to give as the main isolable product 2-phenylbutyrolactone 3. Compound
3 showed the 1H and 13C NMR data in good agreement with previous reports [6] and the
unexpectedly complex coupling pattern of the 1H NMR spectrum was in excellent agree-
ment with a previous detailed analysis of its spectrum [7] The product was obtained in 38%
Scheme 3. Synthesis and thermal rearrangement of 1 to give 3.

JOURNAL OF SULFUR CHEMISTRY
3
isolated yield which is double the yield obtained by Oda et al. [2] using benzene solution
flow pyrolysis and encouraged us to examine the extension to sulfur analogues.
We first prepared the 2-diphenylmethyl-1,3-oxathiolane 5 from diphenylacetaldehyde
(Scheme 4) and were able to fully characterize this previously unknown compound. The
significant chemical shift differentiation of the two CH2O protons (δ 4.39 vs. 3.87) pointed
to a high degree of steric hindrance and we were unable to effect bromination of this com-
pound under a range of conditions, so were unable to introduce the required exocyclic
double bond.
Attention therefore turned to the 2-benzyl-1,3-oxathiolane series (Scheme 5). The
oxathiolane 6 was readily prepared from phenylacetaldehyde dimethyl acetal and showed
good agreement with the previously reported properties including 1H and 13C NMR spec-
tra [8,9]. Oxidation using sodium periodate in aqueous methanol gave the previously
unknown S-oxide 7 in good yield while potassium permanganate oxidation in the presence
of benzoic acid [10] gave the known S,S-dioxide 8 in low yield. This also had properties
in agreement with the reported values [8]. Since there have been relatively few structural
studies of simple S-oxidized 1,3-oxathiolanes [11–13], we decided to examine the 1H NMR
spectrum of sulfoxide 7 in detail and to determine the X-ray structure of the sulfone 8.
At first sight the 1H NMR spectrum of 7 was unexpectedly complex (Figure 1, top) and
this is attributed to the existence of cis and trans-isomers. Fortunately, a detailed study by
Pihlaja et al. [14] succeeded in analyzing in detail the 1H and 13C NMR spectra of a range
Scheme 4. Synthesis of 2-diphenylmethyl-1,3-oxathiolane 5.
Scheme 5. Synthesis of 2-benzyl-1,3-oxathiolane derivatives 6–10.

4
R. A. AITKEN ET AL.
Figure 1. Aliphatic region of the 1H NMR spectrum of 7 showing (top) experimental spectrum for mix-
tureofcisandtrans-isomers,(middle)simulationfortrans-7,and(bottom)simulationforcis-7,bothusing
values given in Table 1.
Figure 2. Structure of previously investigated compound 11 [14].
of simple 1,3-oxathiolane S-oxides including the very similar example 2-(4-nitrophenyl)-
1,3-oxathiolane S-oxide 11 (Figure 2). By comparing our spectra for 7 with the published
values for 11 a remarkable degree of similarity was observed. In particular, the marked
difference between δ for C-2 (100.1 vs. 110.8 for 11, 100.2 vs. 110.4 for 7) allowed us to
C
unambiguously assign the isomer with the lower value as the cis and the higher as the trans
1
by analogy. This then allowed assignment of each H NMR signal for 7 to either cis or
trans isomers using an HSQC correlation (Figure 1, Table 1). Starting from the chemical
shift assignments and coupling constants reported for 11 [14], these parameters were opti-
mized using simulation to match the observed spectra for 7. The final values are shown
in Table 1 and the resulting simulated spectra for cis and trans isomers (Figure 1, middle
and bottom) are in almost perfect agreement with experiment. The very high degree of
similarity in the pattern of coupling constants between 7 and 11, and particularly the high
degree of difference between the values of JH4a–H5s and JH4s−H5a for the trans isomer as

JOURNAL OF SULFUR CHEMISTRY
5
Table 1. Observed 1H NMR chemical shifts (ppm) and coupling constants (Hz)
for the cis and trans isomers of sulfoxide 7.
trans-7
Coupling
H-5a
to
cis-7
Coupling
H-5a
to
δH
H-4s
13.6
H-5s
δH
H-4s
H-5s
H-4a
H-4s
H-5a
H-5s
2.464
2.95
4.54
4.30
7.0
1.0
11.7
4.3
10.0
2.986 13.0
3.35
4.64
7.5
5.3
6.8
7.9
9.8
3.868
CH2Ph-1 CH2Ph-2
CH2Ph-1 CH2Ph-2
H-2
CH2Ph-1
CH2Ph-2
4.68
3.23
3.29
5.6
6.4
14.0
4.406
3.23
3.29
6.8
6.0
14.0
Figure 3. Solution conformations of trans and cis-7 with protons labelled as syn (s) or anti (a) to the
sulfoxide oxygen.
compared to the almost equal magnitude of these values for the cis isomer, leads us to the
same conclusion as was reached for 11 [14]: that trans-7 exists overwhelmingly as a single
half-chair conformation while cis-7 is an almost equal mixture of two alternative half-chair
conformations labeled A and B (Figure 3).
A single-crystal X-ray diffraction study on the sulfone 8 gave a structure (Figure 4)
showing an obvious ‘envelope’ conformation with the ring oxygen out of the plane of the
remaining four essentially coplanar ring atoms and a ring angle of only 94.2° at sulfur. As
far as we are aware, there are only two previous X-ray structures of 1,3-oxathiolane S,S-
dioxides: the carbohydrate-derived compounds 12 [15,16] and 13 [17]. These both show
Figure 4. X-raystructureof8(ORTEPdiagram, 50%probabilitylevel). Selectedbondlengthsandangles:
O1-C2 1.403(2), C2-S3 1.824(2), S3-C4 1.773(2), C4-C5 1.522(3), C5-O1 1.444(2) Å; C2-O1-C5 107.60(14),
O1-C2-S3 102.97(13), C2-S3-C4 94.17(9), S3-C4-C5 103.78(14), C4-C5-O1 107.32(16)°.

6
R. A. AITKEN ET AL.
Figure 5. 1,3-Oxathiolane and 1,3-oxathiole S,S-dioxides previously characterized by X-ray crystallog-
raphy with CCDC Reference Codes.
very similar envelope conformations and the bond lengths and angles within the ring are
very similar to those observed for 8. For the previous structures, the envelope conforma-
tion was attributed to the conformationally constrained bicyclic nature of the compounds,
but it is interesting to observe that 8, although freed of any such constraints, still prefers
to adopt such a conformation. The values for the C(2)–S and S–C(4) bond lengths as
well as the C(2)–S–C(4) angle also agree well with those observed for the few unsatu-
rated 1,3-oxathiole S,S-dioxides 14 [18,19] and 15 and 16 [20] to be crystallographically
characterized although in all these cases the oxathiole ring is planar (Figure 5).
To obtain a sulfur-containing system more closely analogous to 1, we examined the
introduction of an exocyclic double bond at C-2. Attempted radical bromination of either
6 or 7 gave complex mixtures of products but the sulfone 8 was brominated in good yield
to give the previously unknown compound 9 (Scheme 5). This proved to be rather unsta-
ble but was characterized spectroscopically and showed a distinctive AB pattern (δ 5.17,
H
4.71 J = 9.6 Hz) for the PhCHBr–CH(O)SO2 function. There is some precedent for the
formation of 2-alkylidene-1,3-benzoxathiole S,S-dioxides in the study of griseofulvin ana-
logues such as 15 [20,21] and chlorination/dehydrochlorination was successful in some
cases. When a crude sample of 9 was treated with triethylamine in diethyl ether at 0°C, the
resulting product gave spectra which were dramatically simplified as compared to all the
earlier compounds 6–9 and consistent with the completely planar structure 10. In partic-
ular, there were two simple triplets for the ring CH2 groups (δ 4.76, 3.36) and distinctive
H
signals for PhCH = (δ 6.13; δ 103.6).
H
C
We now examined the pyrolysis behavior of the sulfur heterocycles prepared under FVP
conditions. Thermal extrusion of SO2 from five-membered ring heterocycles is well known
[22], but we are only aware of one report describing such extrusion from 1,3-oxathiolane
3,3-dioxides [23]. In this, 4,4-dimethyl-1,3-oxathiolane 3,3-dioxide was found to fragment
cleanly into SO2, isobutene and formaldehyde. This allowed Gokel and coworkers to use
the compound as a formyl anion equivalent [24], by deprotonation and alkylation with an
alkyl halide, RX, at C-2 followed by thermal fragmentation to generate the corresponding
aldehyde RCHO. However to our knowledge there have been no reports of thermal reac-
tivity for 1,3-oxathiolane 3-oxides. When compound 7 was subjected to FVP, complete
reaction was achieved at 500°C and the products in the cold trap were readily identified
as phenylacetaldehyde 17, ethene and acetaldehyde. At the furnace exit, there were several
minor less volatile products. By lowering the reaction temperature to 450°C, some starting
material was obtained but the proportion of one minor product was increased allowing it to
be isolated by preparative TLC and identified as bis(2-hydroxyethyl) disulfide 20. At both
450°C and at 400°C, the cold trap products were mainly phenylacetaldehyde 17, ethene

JOURNAL OF SULFUR CHEMISTRY
7
and acetaldehyde with increasing amounts of unreacted starting material recovered at the
furnace exit. We propose that the unexpected disulfide product 20 is derived from thiirane
S-oxide 18 (Scheme 6). Previous mechanistic studies have described formation of 20 from
18 in solution under acidic conditions [25,26] but under neutral gas-phase conditions a dif-
ferent explanation is required. We believe that ring expansion of 18 to give 1,2-oxathietane
19 may be followed either by loss of sulfur and isomerization, thus explaining the forma-
tion of acetaldehyde, or by homolysis of the O–S bond, dimerization of the diradicals and
hydrogen atom abstraction to give 20 as shown (Scheme 6).
Scheme 6. FVP behavior of sulfoxide 7.
Scheme 7. FVP behavior of sulfone 8.
Scheme 8. FVP behavior of unsaturated sulfone 10.

8
R. A. AITKEN ET AL.
The corresponding sulfone 8 showed a simpler pattern of behavior with clean reaction
upon FVP at 400°C to give phenylacetaldehyde 17, SO2 and ethene as the only products
(Scheme 7). This is entirely analogous to the behavior of the 4,4-dimethyl compounds
described by Gokel [23].
The unsaturated sulfone 10 was mainly unreacted at 400°C but underwent complete
reaction at 500°C to give phenylacetic acid 22 as well as ethene and SO2 (Scheme 8). Since
the sample 10 used contained some 8, there was also some phenylacetaldehyde present
from its pyrolysis. We interpret the formation of 22 as involving the expected extrusion to
form phenylketene 21 which is hydrolyzed by adventitious moisture in the cold trap.
3. Conclusion
The previously reported thermal isomerization of 2-benzylidene-1,3-dioxolane to 3-
phenylbutyrolactone proceeds well under FVP conditions. An analogous process was not
observed for S-oxidized sulfur analogues, which instead underwent SOn extrusion and
fragmentation to give acyclic carbonyl products. A minor process observed for the cyclic
sulfoxide 7 was the formation of bis(2-hydroxyethyl) disulfide, apparently via thermal ring-
1
expansion of thiirane S-oxide. Conformational analysis of 7 by H NMR showed it to
be remarkably similar to the 2-p-nitrophenyl analogue, while X-ray structure determina-
tion of 8 showed a similar envelope conformation to that observed in previous bicyclic
examples.
4. Experimental
4.1. General
Melting points were determined on a Reichert hot-stage microscope and are uncorrected.
NMR spectra were recorded for 1H at 300 or 400 MHz and for 13C at 75 or 100 MHz on
Bruker instruments. Spectra were obtained for solutions in CDCl3 with Me4Si as internal
reference and coupling constants are given in Hz. FVP was conducted using a conven-
tional flow system with the sample being volatilized from an electrically heated inlet tube
through a horizontal quartz reactor tube (30 × 2.5 cm) heated externally by a laboratory
tube furnace, and connected via a liquid nitrogen-cooled product collection trap to a rotary
vacuum pump. The system was maintained at pressures in the range 10–3–10–2 Torr corre-
sponding to a contact time in the hot zone of 1–10 ms. Full details of the procedure are given
in a recent publication [27]. CCDC 1570002 (8) contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
4.2. Synthesis and pyrolysis of 2-(phenylmethylene)-1,3-dioxolane 1
4.2.1. α-Bromophenylacetaldehyde dimethyl acetal
To a solution of β-methoxystyrene [5] (21.7 g, 161 mmol) in CH2Cl2 (100 mL) stirred at
–50°C, a solution of bromine (8.3 mL, 25.8 g, 161 mmol) in CH2Cl2 (30 mL) was added
dropwise over 30 min. Sodium (3.84 g, 167 mmol) was dissolved in methanol (50 mL) to
give a solution of sodium methoxide. To the cold reaction mixture, methanol (7.5 mL) was

JOURNAL OF SULFUR CHEMISTRY
9
slowly added followed by the sodium methoxide solution. After 30 min, the resulting white
suspension was added to water (200 mL) and the organic layer was separated, washed with
water (2 × 100 mL), dried and evaporated to give the title product (36.0 g, 98%) as a brown
oil. 1H NMR (300 MHz): 7.43–7.29 (5 H, m, Ph), 4.93 (1 H, d, J 6.9, CH(OMe)2), 4.74 (1 H,
d, J 6.9, CHBr), 3.48, (3 H, s, OMe), 3.27 (3 H, s, OMe). 13C NMR (100 MHz): 138.1 (C),
129.4 (CH), 128.51 (2CH), 128.47 (2CH), 105.9 (CH(OMe)2), 55.0 (OMe), 54.8 (OMe),
52.9 (CHBr).
4.2.2. 2-(α-Bromobenzyl)-1,3-dioxolane
A mixture of α-bromophenylacetaldehyde dimethyl acetal (10.0 g, 41 mmol), ethane-1,2-
diol (3.62 g, 58 mmol) and p-toluenesulfonic acid (20 mg) was distilled in a bath held at
180°C until evolution of methanol ceased. The residue was dissolved in CH2Cl2 (100 mL)
and the solution was washed with aqueous sodium carbonate, dried and evaporated to give
the title product (8.85 g, 89%) as a brown oil. 1H NMR (400 MHz): 7.50–7.46 (2 H, m, Ph),
7.38–7.25 (3 H, m, Ph), 5.32 (1 H, d, J 4.4, OCHO), 4.91 (1 H, d, J 4.4, CHBr), 4.00–3.87
(4 H, m, CH2). 13C NMR (100 MHz): 137.1 (C), 128.8 (2CH), 128.7 (CH), 128.4 (2CH),
104.6 (OCHO), 65.84 (CH2), 65.81 (CH2), 54.4 (CHBr).
4.2.3. 2-Benzylidene-1,3-dioxolane 1
A solution of potassium tert-butoxide (0.22 g, 2.0 mmol) in tert-butanol (1.5 mL) was
added to 2-(α-bromobenzyl)-1,3-dioxolane (0.50 g, 2.0 mmol) and the mixture was heated
under reflux for 2 h. A vacuum was applied and once all the tert-butanol was removed the
residue was extracted with diethyl ether (5 mL) which was washed with water, dried and
evaporated to afford the product (0.35 g, 96%) as a pale yellow oil. 1H NMR (400 MHz):
7.37 (2 H, d, J 8.0, Ph), 7.23 (2 H, t, J 8.0, Ph), 7.00 (1 H, t, J 8.0, Ph), 4.86 (1 H, s, PhCH=),
4.40 (2 H, t, J 7.2, CH2), 4.23 (2 H, t, J 7.2, CH2). 13C NMR (100 MHz): 159.7 (OCO), 136.3
(C), 128.2 (3CH), 125.8 (2CH), 123.4 (CH), 74.7 (PhCH=), 67.0 (CH2), 64.8 (CH2).
4.2.4. FVP of 1 to give 3-phenylbutyrolactone 3
FVP of 2-(phenylmethylene)-1,3-dioxolane (148 mg) at 600°C and 10–2 Torr gave at the
furnace exit 3-phenylbutyrolactone 2 (56 mg, 38%). 1H NMR (400 MHz): 7.38–7.25 (5 H,
m, Ph), 4.43 (1 H, ddd, J 9.2, 8.4, 3.2, OCH2), 4.30 (1 H, ddd, 9.2, 9.2, 6.8, OCH2), 3.78 (1
H, dd, J 10.4, 9.2, PhCH–), 2.67, (1 H, dddd, J 12.4, 9.2, 6.8, 3.2, CH2), 2.40 (1 H, dddd, J
12.4, 10.4, 9.2, 8.4, CH2). 13C NMR (100 MHz): 177.4 (CO), 136.6 (C), 128.7 (2CH), 127.8
(2CH), 127.5 (CH), 66.4 (CH2O), 45.3 (PhCH), 31.4 (CH2).
4.3. Synthesis of 2-(diphenylmethyl)-1,3-oxathiolane 5
A solution of diphenylacetaldehyde (2.19 g, 11.2 mmol), 2-mercaptoethanol (0.87 g,
11.1 mmol) and p-toluenesulfonic acid (0.02 g, 0.1 mmol) in toluene (35 mL) was heated
under reflux under Dean–Stark azeotropic distillation conditions. After heating for 3 h,
the solution was cooled to room temperature and most of the solvent was removed under
reduced pressure. The resulting solid was filtered off to give the product (1.24 g, 43%) as
a white solid, mp 75–78°C. HRMS (ESI) m/z calcd for C16H16OSNa: 279.0820, found:
1
279.0809 [M + Na]. H NMR (300 MHz): 7.34-7.21 (10 H, m, Ph), 5.83 (1 H, d, J 9.0,
OCHS), 4.39 (1 H, m, OCH2), 4.25 (1 H, d, J 9.0, Ph2CH), 3.87 (1 H, m, OCH2) and

10
R. A. AITKEN ET AL.
2.98 (2 H, m, SCH2). 13C NMR (75 MHz): 141.76 (C), 141.74 (C), 128.5 (2CH), 128.4
(2CH), 128.32 (2CH), 128.28 (2CH), 127.0 (CH), 126.7 (CH), 89.5 (OCS), 72.1 (CH2O),
58.0 (CH2S), 32.8 (Ph2CH).
4.4. Synthesis of 2-benzyl-1,3-oxathiolane and its S-oxides
4.4.1. Synthesis of 2-benzyl-1,3-oxathiolane 6
Phenylacetaldehyde dimethyl acetal (5.8 g, 34.9 mmol), 2-mercaptoethanol (3.9 g, 3.5 mL,
49.9 mmol) and p-toluenesulfonic acid (0.01 g) were heated to 100°C. Once the methanol
produced had boiled off, the residual oil was dissolved in CH2Cl2 (15 mL) and the solution
was washed with water, dried and evaporated to afford the product (5.64 g, 90%) as a brown
oil. 1H NMR (400 MHz): 7.32–7.22 (5 H, m, Ph), 5.28 (1 H, t, J 6.2, OCHS), 4.35 (1 H, m,
OCH2), 3.79 (1 H, m, OCH2), 3.23 (1 H, m, SCH2), 3.02 (3 H, m, SCH2 and CH2Ph). 13
C
NMR (100 MHz) 137.4 (C), 129.1 (2CH), 128.3 (2CH), 126.7 (CH), 87.3 (OCHS), 71.4
(CH2O), 42.9 (PhCH2), 32.7 (CH2S). The NMR data reported agree with the literature
values [8,9].
4.4.2. Synthesis of 2-benzyl-1,3-oxathiolane 3-oxide 7
To a stirred solution of 2-benzyl-1,3-oxathiolane (1.00 g, 5.6 mmol) in methanol (10 mL),
a solution of sodium metaperiodate (1.24 g, 5.8 mmol) in water (5 mL) was added drop-
wise. The reaction mixture was stirred overnight then filtered and the filtrate extracted with
CH2Cl2 (20 mL) which was dried and evaporated to yield the product (0.81 g, 74%) as an
orange oil. HRMS (ESI) m/z calcd for C10H12SO2Na: 219.0456, found: 219.0444 [M + Na].
max/cm–1 1213, 1055, 1030 (S O), 747, 540. m/z (ESI) 219.04 (M + Na, 100%).
=
ν
Trans diastereomer 1H NMR (400 MHz): 7.33–7.24 (5 H, m, Ph), 4.68 (1 H, dd, J 6.4, 5.6,
OCHS), 4.54 (1 H, m, OCH2), 4.30 (1 H, m, OCH2), 3.38–3.22 (2 H, m, PhCH2), 2.99–2.90
(1 H, m, SCH2), 2.46 (1 H, m, SCH2). 13C NMR (100 MHz): 135.3 (C), 128.6 (2CH), 128.5
(2CH), 127.1 (CH), 110.4 (OCS), 68.9 (CH2O), 52.5 (CH2S), 36.7 (PhCH2).
1
Cis diastereomer H NMR (400 MHz): 7.33–7.24 (5 H, m, Ph), 4.64 (1 H, m, OCH2),
4.41 (1 H, dd, J 6.8, 6.0, OCHS), 3.87 (1 H, m, OCH2), 3.38–3.22 (3 H, m, PhCH2 and
SCH2), 2.99–2.90 (1 H, m, SCH2); 13C NMR (100 MHz) 135.9 (C), 129.4 (2CH), 129.3
(2CH), 127.0 (CH), 100.2 (OCS), 67.8 (CH2O), 54.2 (CH2S), 32.8 (PhCH2).
4.4.3. Synthesis of 2-benzyl-1,3-oxathiolane 3,3-dioxide 8
2-Benzyl-1,3-oxathiolane (1.00 g, 5.6 mmol), benzoic acid (0.68 g, 5.6 mmol) and benzyl-
triethylammonium chloride (0.21 g, 0.94 mmol) were stirred in CH2Cl2 (30 mL). A solu-
tion of potassium permanganate (2.00 g, 12.7 mmol) in water (50 mL) was added and the
mixture was stirred vigorously overnight. Sodium metabisulfite was added until the reac-
tion mixture turned colorless and the suspension was filtered through celite. The CH2Cl2
layer was separated and the aqueous layer extracted with CH2Cl2 (30 mL). The com-
bined organic phase was washed with aqueous hydrazine dihydrochloride, aqueous sodium
hydroxide and then dried and evaporated to yield the product (0.36 g, 31%) as colorless
crystals, mp 98–99.5°C, (lit. [8] 95–96.5°C). HRMS (ESI) m/z calcd for C10H12SO3Na:
235.0405, found: 235.0398 [M + Na]. 1H NMR (400 MHz): 7.36–7.28 (5 H, m, Ph), 4.53 (1
H, ddd, J 10.4, 6.0, 4.0, OCH2), 4.30 (1 H, dd, J 8.4, 4.4, OCHS), 4.13 (1 H, ddd, J 10.4, 9.6,
7.2, OCH2), 3.27–3.21 (3 H, m, PhCH2 and SCH2), 3.05 (1 H, dd, J 14.8, 8.4, SCH2). 13
C

JOURNAL OF SULFUR CHEMISTRY
11
NMR (100 MHz): 134.6 (C), 129.3 (2CH), 128.7 (2CH), 127.3 (CH), 91.7 (OCHS), 64.6
(CH2O), 48.9 (CH2S), 34.1 (PhCH2). m/z (ESI) 235.04 (M + Na, 100%). The NMR data
reported are in agreement with those in the literature [8].
4.4.4. X-ray structure determination of 2-benzyl-1,3-oxathiolane 3,3-dioxide 8
Data were collected on a Rigaku Saturn 724 diffractometer using graphite monochromated
Mo–Kα radiation, λ = 0.71075 Å. Crystal data for C10H12O3S, M 212.26, colorless platelet
0.20 × 0.10 × 0.010 mm. Monoclinic, space group P21/n, a = 12.535(5), b = 5.7368(16),
c = 15.205(5) Å, β = 112.539(7)°, V = 1009.9(6) Å3, Z = 4, Dc = 1.396 g/cm3,
T = 125 K, R = 0.0344, Rw = 0.0780 for 1387 data with I > 2σ(I) and 127 parameters.
4.5. Preparation of 2-benzylidene-1,3-oxathiolane 3,3-dioxide
4.5.1. Synthesis of 2-(α-bromobenzyl)-1,3-oxathiolane 3,3-dioxide 9
A solution of 2-benzyl-1,3-oxathiolane 3,3-dioxide (0.10 g, 0.47 mmol), N-bromo-
succinimide (0.08 g, 0.47 mmol) and AIBN (0.008 g) in CH2Cl2 (5 mL) was heated under
reflux. After 4 hours the reaction mixture was filtered, washed with water, dried and evap-
orated to yield the product (0.10 g, 72%) as an unstable white solid which still contained
some starting material and succinimide but was used without further purification for the
next step. HRMS (ESI) m/z calcd for C10H11O379BrSNa: 312.9510 and C10H11O381BrSNa:
314.9490, found 312.9499 [79Br–M + Na] and 314.9477 [81Br–M + Na]. νmax/cm–1 1314
(S O), 1117 (S O), 1076 (C–O), 1055 (C–O), 754 (C–S), 692 (C–Br). 1H NMR
(400 MHz): 7.51–7.26 (5 H, m, Ph), 5.17 (1 H, d, J 9.6, OCHS), 4.71 (1 H, d, J 9.6, PhCHBr),
=
=
4.66–4.61 (1 H, m, OCH2), 4.30–4.23 (1 H, m, OCH2), 3.35-3.31 (2 H, m, SO2CH2). 13
C
NMR (100 MHz): 134.5 (C), 130.0 (CH), 129.0 (2CH), 128.6 (2CH), 92.7 (OCHS), 64.1
(CH2O), 50.6 (CH2S), 47.8 (PhCHBr). m/z (ESI) 314.95 (81Br-M + Na, 100%), 312.95
(79Br-M + Na, 98%).
4.5.2. Preparation of 2-benzylidene-1,3-oxathiolane 3,3-dioxide 10
A solution of 2-(α-bromobenzyl)-1,3-oxathiolane 3,3-dioxide (0.24 g, 0.82 mmol) in
diethyl ether (5 mL) was stirred at 0°C. Triethylamine (0.12 g, 1.20 mmol) was added slowly
and the reaction mixture left to stir for 1 h. Addition of CH2Cl2 (10 mL) gave a clear solu-
tion which washed with water (2 × 10 mL), dried and evaporated to yield the product.
This was then recrystallized from hexane/diethyl ether (3:1) to obtain the pure product
(22.5 mg, 13%) as colorless crystals. 1H NMR (400 MHz): 7.60–7.29 (5 H, m, Ph), 6.13 (1
H, s, PhCH=), 4.76 (2 H, t, J 6.6, OCH2), 3.35 (2 H, t, J 6.6, SO2CH2). 13C NMR (100 MHz)
(obtained from a mixture containing 8): 147.4 (OCS), 131.9 (C), 129.2 (2CH), 128.6 (2CH),
128.4 (CH), 103.6 (PhCH=), 65.9 (CH2O), 46.4 (CH2S).
4.6. FVP of 1,3-oxathiolane S-oxides
4.6.1. FVP of 2-benzyl-1,3-oxathiolane 3-oxide 7
FVP of 7 (49.5 mg) at 500°C gave, in the cold trap, a mixture of phenylacetaldehyde 17
1H NMR (300 MHz): 9.75 (1 H, t, J 2.4, CHO), 7.42–7.22 (5 H, m, ArH), 3.70 (2 H, d, J
2.4, CH2) (agrees with lit. [28]); ethene 1H NMR (300 MHz): 5.40 (s); and acetaldehyde 1H
NMR (400 MHz): 9.79 (1 H, q, J 2.8, CHO), 2.20 (3 H, d, J 2.8). At the furnace exit, there

12
R. A. AITKEN ET AL.
was a small amount of material consisting of bis(2-hydroxyethyl) disulfide 20 and other
unidentified components.
FVP of 7 (103 mg) at 450°C gave, in the cold trap, a mixture of phenylacetaldehyde,
ethene and acetaldehyde as described above. At the furnace exit, there was an oil consisting
of unchanged 7, bis(2-hydroxyethyl) disulfide and other unidentified components. Prepar-
1
ative TLC (SiO2, EtOAc) yielded bis(2-hydroxyethyl) disulfide 20 H NMR (400 MHz):
3.92 (2 H, t, J 5.8, CH2OH), 2.89 (2 H, t, J 5.8, SCH2), 1.25 (1H, br s, –OH). 13C NMR
(100 MHz): 60.3 (CH2O), 41.2 (CH2S) (agrees with lit. [29]).
4.6.2. FVP of 2-benzyl-1,3-oxathiolane 3,3-dioxide 8
FVP of 8 (38.1 mg) at 400°C gave, in the cold trap, a mixture of phenylacetaldehyde, 1H
NMR as above; 13C NMR (100 MHz) 199.5 (CO), 129.6 (2CH), 129.0 (2CH), 127.4 (CH),
50.6 (CH2) (agrees with lit. [28]) and ethene 1H NMR as above.
4.6.3. FVP of 2-benzylidene-1,3-oxathiolane 3,3-dioxide 10
FVP of 10 (46.8 mg, containing some 8) at 500°C gave, in the cold trap, a mixture of pheny-
lacetaldehyde 17, 1H NMR as above, ethene, 1H NMR as above, and phenylacetic acid 22
1H NMR (400 MHz) 7.40–7.22 (5 H, m, ArH), 3.72 (2 H, s, CH2); 13C NMR (100 MHz)
178.5 (CO), 134.5 (C), 129.3 (2CH), 128.6 (2CH), 127.3 (CH), 40.8 (CH2) (agrees with
lit. [30]).
Disclosure statement
No potential conflict of interest was reported by the authors.
References
[1] Aitken RA, Boubalouta Y. Recent advances in the synthesis of heterocyclic compounds using
flash vacuum pyrolysis. Adv Heterocycl Chem. 2015;115:93–150.
[2] Oda M, Morimoto K, Thanh NC, et al. Thermal rearrangement of phenyl-substituted ketene
ethylene acetals. Heterocycles. 2003;60:1673–1680.
[3] Baldwin JE, Walker LE. Syntheses of phenylketene acetals via α-bromophenylacetaldehyde
acetals. J Org Chem. 1966;31:3985–3989.
[4] McElvain SM, Curry MJ. Ketene acetals XIX. 2-methylene-1,3-dioxolanes and 1,3-dioxanes. J
Am Chem Soc. 1948;70:3781–3786.
[5] Blattner K, Schank K. Zum mechanismus einer α-bromoacetal/ester-umlagerung. Leibigs Ann
Chem. 1977:1109–1115.
[6] Rück-Braun K, Möller C. Novel intramolecular cyclocarbonylations involving π-alkene-
hydridoiron intermediates: from [η5-C5H5(CO)2Fe]-substituted (Z)-enals to α,β-butenolides
and γ -butyrolactones. Chem Eur J. 1999;5:1038–1044.
[7] Karlsson S, Hallberg A, Gronowitz S. Hydrozirconation of (E)-3-methoxy-1-phenyl-1-propene
and (E)-3-phenyl-2-propanol. J Organomet Chem. 1991;403:133–144.
[8] Gokel GW, Gerdes HM, Dishong DM. Sulfur heterocycles 3. heterogeneous, phase-transfer,
and acid-catalyzed potassium permanganate oxidation of sulfides to sulfones and a survey of
their carbon-13 nuclear magnetic resonance spectra. J Org Chem. 1980;45:3634–3639.
[9] Streinz L, Koutek B, Saman D. An effective synthesis of 1,3-oxathiolanes. Collect Czech Chem
Commun. 1997;62:665–671.
[10] Aitken RA, Mesher STE, Ross FC, et al. Effect of added benzoic acid on the phase-transfer
catalysed permanganate oxidation of organosulfur compounds. Synthesis. 1997:787–791.

JOURNAL OF SULFUR CHEMISTRY
13
[11] Aitken RA, Hill L. 1,3-Dioxoles and 1,3-oxathioles. Compr Heterocycl Chem II. 1996;3:
525–567.
[12] Aitken RA, Power LA. 1,3-Dioxoles and 1,3-oxathioles. Compr Heterocycl Chem III.
2008;4:841–891.
[13] Aitken RA, Power LA. Recent advances in the chemistry of 1,3-dioxoles and 1,3-oxathioles: an
update. Adv Heterocycl Chem. 2013;108:163–193.
[14] Pihlaja K, Sinkkonen J, Stájer G. 3-Oxo-1,3-oxathiolanes - synthesis and stereochemistry. Magn
Reson Chem. 2008;46:244–249.
[15] Skelton BW, Stick RV, Tilbrook DMG, et al. Investigations into the chemistry of some 1,6-
epithio and 1,6-episeleno β-d-glucopyranoses. Aust J Chem. 2000;53:389–397.
[16] Budesinsky M, Polakova J, Hamernikova M, et al. 1,6-Anhydro-1-thio-β-d-glucopyranose
(thiolevoglucosan) and the corresponding sulfoxides and sulfone. Collect Czech Chem Com-
mun. 2006;71:311–336.
[17] Sivapriya K, Hariharaputran S, Suhas VL, et al. Conformationally locked thiosugars as potent
α-mannosidase inhibitors: synthesis, biochemical and docking studies. Bioorg Med Chem.
2007;15:5659–5665.
[18] Block E, Aslam M, Iyer R, et al. α-Haloalkanesulfonyl bromides in organic synthesis 3. α-
alkylidene ketones and 1,3-oxathiole 3,3-dioxides from trimethylsilyl enol ethers. J Org Chem.
1984;49:3664–3666.
[19] Block E, Aslam M, Eswarakrishnan V, et al. α-Haloalkanesulfonyl bromides in organic syn-
thesis 5. Versatile reagents for the synthesis of conjugated polyenes, enones, and 1,3-oxathiol
1,1-dioxides. J Am Chem Soc. 1986;108:4568–4580.
[20] Friedrich M, Meichle W, Bernhard H, et al. Sulfogriseofulvin derivatives. Synthesis by
[4 + 2] cycloaddition, structure, properties, crystal structure analysis, and antifungal activity
of spiro[1,3-benzoxathiole-2,1’-cyclohex-2’-en]-4’-one 3,3-dioxides. Arch Pharm (Weinheim
Ger). 1996;329:361–370.
[21] Meichle W, Otto H-H. Darstellung und dehydratisierung von 2-(α-alkyl)- oder (α-aryl)-
substituierten hydroxymethyl-5-methoxy-1,3-benzoxathiol-3,3-dioxiden. Arch Pharm (Wein-
heim Ger). 1989;322:263–270.
[22] Aitken RA, Gosney I, Cadogan JIG. Extrusion of SO2 from heterocyclic compounds, part 2:
five-membered rings. Prog Heterocycl Chem. 1993;5:1–33.
[23] Gokel GW, Gerdes HM, Miles DE, et al. Sulfur heterocycles 1. Use of 4,4-dimethyl-1,3-
oxathiolane 3,3-dioxide as a carbonyl anion equivalent. Tetrahedron Lett. 1979;20:3375–3378.
[24] Aitken RA, Thomas AW. Heterocyclic acyl and formyl anion equivalents. Adv Heterocycl
Chem. 2001;79:89–114.
[25] Kondo K, Negishi A, Ojima I. Acid-catalyzed ring opening reactions of episulfoxides. J Am
Chem Soc. 1972;94:5786–5793.
[26] Saleh A, Tillett JG. The acid-catalysed hydrolysis of episulfoxides. J Chem Soc Perkin Trans 2.
1981:132–139.
[27] Aitken RA, Horsburgh CER. Flash vacuum pyrolysis of o-phenylene sulfite: formation and
purification of cyclopentadienone dimer. In: Afonso CAM, Candeias NR, Simao DP, Trinidade
AF, Coelho JAS, Tan B, Franzén R, editor. Comprehensive organic chemistry experiments for
the laboratory classroom. Cambridge: RSC; 2017. p. 690–693.
[28] Zhang L, Zha Z, Wang Z. An efficient electrochemical method for the paired synthe-
sis of carbonyl compounds and homoallylic alcohols in a simple home-made cell. Synlett.
2010:1915–1918.
[29] Christoforou A, Nicolaou G, Elemes Y. N-Phenyltriazolinedione as an efficient, selective, and
reusable reagent for the oxidation of thiols to disulfides. Tetrahedron Lett. 2006;47:9211–9213.
[30] León T, Correa A, Martin R. Ni-Catalyzed direct carboxylation of benzyl halides with CO2. J
Am Chem Soc. 2013;135:1221–1224.