Intramolecular Diels-Alder reactions of 1-phenylsulfonylalka-1,2,(ω - 3),(ω - 1)-tetraenes

Article abstract of DOI:10.1039/b005146m

Methods are described for conversion of a series of (E)-alka-(ω - 3),(ω - 1)-dienals 2, via ethynylation to the corresponding alkadienynols 3, followed by sequential [2,3] sigmatropic rearrangement of their derived phenylsulfenate esters and chemoselective oxidation, into 1-phenylsulfonylalka-1,2,(ω - 3),(ω - 1)-tetraenes 5, which are used to study the influence of tether length and peripheral substitution upon intramolecular cycloaddition reactivity and selectivity. It is demonstrated that (6E)-1-phenylsulfonylnona-1,2,6,8-tetraene 5c and substrates featuring an analogous ethylene linkage between the functional termini, display exceptionally high intramolecular Diels-Alder (IMDA) reactivity, accompanied by exo-diastereoselectivity. Comparative studies are described, which delineate structure-reactivity trends and demonstrate the unique capacity of the dienophilic allenyl terminus to impose reactivity-enhancing conformational constraints upon IMDA processes in favourable cases. Preliminary investigations into substrates incorporating cyclic dienyl substructures are reported, and a novel approach to spiro[4.5]decanoid ring systems is described. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b005146m

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Intramolecular Diels–Alder reactions of 1-phenylsulfonylalka-
1,2,(ꢀ ؊ 3),(ꢀ ؊ 1)-tetraenes
James R. Bull,* Richard Gordon and Roger Hunter
1
Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
Received (in Cambridge, UK) 27th June 2000, Accepted 25th July 2000
Published on the Web 1st September 2000
Methods are described for conversion of a series of (E)-alka-(ω Ϫ 3),(ω Ϫ 1)-dienals 2, via ethynylation to the
corresponding alkadienynols 3, followed by sequential [2,3] sigmatropic rearrangement of their derived
phenylsulfenate esters and chemoselective oxidation, into 1-phenylsulfonylalka-1,2,(ω Ϫ 3),(ω Ϫ 1)-tetraenes 5,
which are used to study the influence of tether length and peripheral substitution upon intramolecular cycloaddition
reactivity and selectivity. It is demonstrated that (6E)-1-phenylsulfonylnona-1,2,6,8-tetraene 5c and substrates
featuring an analogous ethylene linkage between the functional termini, display exceptionally high intramolecular
Diels–Alder (IMDA) reactivity, accompanied by exo-diastereoselectivity. Comparative studies are described, which
delineate structure–reactivity trends and demonstrate the unique capacity of the dienophilic allenyl terminus to
impose reactivity-enhancing conformational constraints upon IMDA processes in favourable cases. Preliminary
investigations into substrates incorporating cyclic dienyl substructures are reported, and a novel approach to
spiro[4.5]decanoid ring systems is described.
Introduction
Results and discussion
Intramolecular Diels–Alder (IMDA) reaction methodology
constitutes a key strategic step in the synthesis of many com-
plex polycyclic molecules, and continues to receive attention as
a vehicle for evaluating and applying emerging principles of
reactivity and selectivity.1 As part of our investigations into the
reactivity of allenyl dienophiles in cycloaddition methodology,2
we became interested in the scope for incorporating a phenyl-
sulfonylallenyl dienophilic terminus into substrates for IMDA
reactions. Phenylsulfonylallene is a useful reactant in inter-
molecular cycloaddition methodology,3 and we sought to
take advantage of the favourable reactivity associated with this
functionality and, most importantly, to prepare the way for
exploiting axial chirality as a tool for conducting IMDA
reactions leading to enantiocontrolled synthesis of cyclic
products.
A general synthetic approach to model substrates for this
investigation was envisaged through ethynylation of (E)-alka-
(ω Ϫ 3),(ω Ϫ 1)-dienals 2, and exploitation of the familiar [2,3]
sigmatropic rearrangement9 of derived propargylic phenyl-
sulfenate esters (propargyl = prop-2-ynyl) to the corresponding
terminal phenylsulfinylallenes 4, followed by chemoselective
oxidation to the 1-phenylsulfonylalka-1,2,(ω Ϫ 3),(ω Ϫ 1)-
tetraenes 5 (Scheme 1). An early objective was to synthesise
Allenyl functionality has featured in a limited number
of studies on intramolecular cycloaddition, both as the
dienophilic terminus4 and as part of the diene substructure.5 It
has been shown6 that certain thermally induced cycloadditions
involving 3-phenylsulfonylallenyl-terminated substrates are
characterised by competition between [2 ϩ 2] and [2 ϩ 4]
pathways, which are sensitive to peripheral structural features,
and do not necessarily engage the dienophilically activated
π-bond of the allenyl group. Additionally, evidence has
emerged for an ene pathway in reactions of a presumed
1-phenylsulfonylallenyl olefin,7 thus complementing the fore-
going cycloaddition modes of ring formation. The underlying
factors responsible for dictating alternative reaction outcomes
are not evident from these reports, suggesting much scope
for systematic exploration of IMDA reaction methodology in
this area. Accordingly, we set out to test structure–reactivity
trends associated with 1-phenylsulfonylallenyl-terminated
substrates, and to ascertain whether useful levels of diastereo-
selectivity and periselectivity could be achieved. The first
phase of this investigation addresses the question of the roles of
1-phenylsulfonyl substitution and of tether length on thermal
reactivity of alka-1,2,(ω Ϫ 3),(ω Ϫ 1)-tetraenyl templates.8
Scheme 1 Reagents and conditions: (i) Swern oxidation; (ii) PCC,
CH2Cl2, 20 ЊC; (iii) Dess–Martin periodinane, CH2Cl2, 20 ЊC; (iv)
᎐
᎐
HC᎐CMgBr, THF, 20 ЊC; (v) TBDPSO(CH2)3C᎐CH, n-BuLi, THF,
᎐
᎐
᎐
0 ЊC; (vi) TBDPSOCH2C᎐CH, n-BuLi, THF, 0 ЊC; (vii) PhSCl, NEt3,
᎐
CH2Cl2, Ϫ78 ЊC; (viii) MCPBA, CH2Cl2, 0–25 ЊC.
the parent tetraenes 5a–5c (R1 = R2 = H), distinguished respec-
tively by tetramethylene, trimethylene and ethylene linkages
between the functional termini, in order to ascertain the role
of tether length upon intramolecular reactivity and periselec-
tivity. Ensuing investigations were influenced by the outcome
of these preliminary experiments, and entailed synthesis of
ethylene-tethered tetraenes 5d–5f, incorporating chain exten-
sion at C-1 and/or alkyl substitution at C-6.
DOI: 10.1039/b005146m
J. Chem. Soc., Perkin Trans. 1, 2000, 3129–3139
This journal is © The Royal Society of Chemistry 2000
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Table 1 Summary of reaction conditions and cycloadduct distributions
Reaction conditions
Product(s)
Totala
Tetraene
% E
Temp./ЊC
Time/h
Distributionb
5a
5b
5cc
5d
5e
5f
88
97
95
100
95
100
180
80
≤30
150
50
24
20
0.5
2
2
2
34
73
71
58
79
0c
6 (100)
7 (25)
9 (21)
11 (22)
13 (100)
—
8 (75)
10 (79)
12 (78)
150
a ‘Total’ refers to % yield of IMDA product(s) corrected for exclusive participation by the (E)-isomer. b Distribution of isomers, showing relative
proportions of isolated products in parentheses. c Data based upon 4c as starting material (see text).
Synthesis of starting materials
reaction, which is discussed in the context of the IMDA reac-
tions. 4-Methylhepta-4,6-dien-1-ol 1d17 was similarly converted
into 1-phenylsulfinyl-6-methylnona-1,2,6,8-tetraene 4d which,
in contrast to 4c, furnished the isolable and readily character-
ised 1-phenylsulfonyl compound 5d upon oxidation with
MCPBA.
Finally, two further model substrates featuring attachment of
functionalised alkyl groups at C-1 of a 1-phenylsulfonylnona-
1,2,6,8-tetraenyl substructure, were synthesised via alkynylation
of 2c and 2d, followed by the standard rearrangement–
oxidation sequence, to give 5e and 5f respectively. These low-
yield procedures have not been optimised, but provided
sufficient material upon which to test the influence of these
substitution patterns on reactivity.
The starting (E)-alkadienols 1 were synthesised using routine
literature methodology, with some minor adaptations designed
to optimise yields and E-selectivity. For example, hexane-1,6-
diol was converted into nona-6,8-dien-1-ol 1a10 (88% E) over
five standard steps, and Swern oxidation gave aldehyde 2a,11
which was ethynylated to give dienynol 3a. The aldehyde 2a
(as well as the structural analogues 2b–2d) proved to be labile
and highly volatile, which necessitated immediate conversion
into the more tractable 3a, which displayed the expected
spectroscopic properties, most notably, distinctive 1H NMR
multiplets for the propargylic functionality at δ 2.47 (dd, J 2.3
and 0.8, 1-H) and δ 4.40 (td, J 2 × 6.3 and 2.3, 3-H).
Reaction of propargyl alcohol 3a with benzenesulfenyl
chloride12 and triethylamine at Ϫ78 ЊC gave the 1-phenyl-
sulfinylallene 4a in 77% yield, arising from the formation of the
intermediate phenylsulfenate ester and subsequent [2,3] sigma-
tropic rearrangement.9 Spectrosopic examination revealed that
4a occurs as the expected mixture of diastereomeric sulfoxides
and, although partial chromatographic separation was possible,
the mixture was preferably oxidised with m-chloroperbenzoic
acid (MCPBA) to give the derived 1-phenylsulfonylundeca-
1,2,8,10-tetraene 5a (66%), full characterisation of which con-
firmed the structure, and thereby also those of the precursors.
1H NMR spectroscopy of 5a displayed diagnostic signals for
the allenyl protons at δ 6.19 (dt, J 6.2 and 2 × 3.1, 1-H) and
δ 5.83 (td, J 2 × 7.0 and 6.2, 3-H), in addition to those of
the 8E,10-dienyl protons. Although MCPBA oxidation of 4a
displayed satisfactory chemoselectivity, attempts to force this
and related reactions to completion through use of excess
reagent and longer reaction times resulted in loss of material,
presumably through intrusion of competing olefinic bond
epoxidation.
Octa-5,7-dien-1-ol 1b (97% E; prepared from 2-allyltetra-
hydropyran according to a procedure described by Schlosser
et al.13) was similarly subjected to successive oxidation (to
2b) and ethynylation to give propargyl alcohol 3b in 67%
overall yield. Phenylsulfenylation–rearrangement followed by
oxidation afforded 1-phenylsulfonyldeca-1,2,7,9-tetraene 5b.
Orthoester Claisen rearrangement of penta-1,4-dien-3-ol,14
followed by reduction of the resultant ethyl hepta-4,6-dienoate
with diisobutylaluminium hydride (DIBAL-H) gave hepta-4,6-
dien-1-ol 1c (95% E) in an overall yield of 86%. An alternative
preparation of 1c entailed reaction of pent-4-yn-1-yl tert-
butyldiphenylsilyl (TBDPS) ether with zirconocene hydrogen
chloride (Schwartz’s reagent15), followed by treatment with
iodine. Stille coupling16 of the resulting vinyl iodide with vinyl-
tributyltin resulted in highly selective formation of essentially
pure (E)-dienol 1c. The latter reaction sequence, although
lower yielding than the former, provided a more versatile
general approach to structural variants (e.g. 1d, below) of the
ethylene-linked tetraene prototype. Conversion of 1c (via 2c
and 3c) into 1-phenylsulfinylnona-1,2,6,8-tetraene 4c proceeded
routinely, but MCPBA oxidation of 4c failed to furnish isolable
1-phenylsulfonyl derivative 5c, owing to an unavoidable further
IMDA reactions of 1-phenylsulfonylalka-1,2,(ꢀ ؊ 3),(ꢀ ؊ 1)-
tetraenes 5a–5f
With the selected range of 1-phenylsulfonylalkatetraenes 5 in
hand for evaluation of their cycloaddition behaviour, a solution
of each compound was heated under nitrogen in a sealed tube,
at a temperature chosen to promote the desired reaction course
whilst minimising adventitious decomposition as revealed by
TLC and/or NMR monitoring. As far as possible, the reported
reaction conditions represent minimum temperatures and times
for complete consumption of starting material. Although these
results were reproducible, no attempt was made to explore the
scope for optimisation of reaction duration and yields through
variations in solvent and concentration. The results of these
experiments are outlined in Scheme 2, and summarised for
comparison in Table 1.
Certain distinctive features of specific reactions warrant
comment. In the first place, the inefficiency of the IMDA
process for 1-phenylsulfonylundeca-1,2,8,10-tetraene 5a is note-
worthy. Experiments performed at 120 and 150 ЊC resulted only
in slow but progressive deterioration of substrate integrity,
without formation of discrete products. However, the elevated
temperature (180 ЊC) at which formation of product 6 was
observed, was also accompanied by extensive decomposition.
On the other hand, the IMDA reaction of 1-phenylsulfonyl-
deca-1,2,7,9-tetraene 5b proceeded cleanly at 80 ЊC. The
extraordinary IMDA reactivity of 1-phenylsulfonylnona-
1,2,6,8-tetraene 5c was inferred from the failure to isolate
the compound following oxidation of the precursor 4c at 0 ЊC.
As a consequence, the oxidation mixture was maintained at
30 ЊC for 20 min, which resulted in completion of the IMDA
process.
The latter result influenced the decision to extend the study,
by incorporating the core substructure of 5c into further-
substituted substrates. Introduction of a 6-methyl group
resulted in a significant suppression of the IMDA reactivity
of 5d (requiring 2 h at 150 ЊC for consumption of starting
material) as well as loss of yield, whereas chain extension at C-1
enabled the compound 5e to be prepared and characterised
with ease, but nevertheless to display impressive IMDA reac-
tivity in CDCl3 at 50 ЊC (solvent chosen to facilitate NMR
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J. Chem. Soc., Perkin Trans. 1, 2000, 3129–3139

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Table 2 Comparative 1H NMR data for the cycloadducts 7–13a
Olefinic proton signals
CHSO2Ph
Cpd
δ
Mult.
J/Hz
position
δ
Mult.
ddd
J/Hz
position
5-H
7
6.55
5.52
5.43
5.25
5.65
5.57
6.42
5.18
5.41
5.37
5.57
5.57
6.1
5.38
5.65
5.6
5.55
5.82
5.4
br d
ddt
br d
m
dddd
br d
t
ddt
br d
br d
ddt
dq
br d
ddd
dd
m
dt
br d
br s
ddd
br d
2
4-H
7-H
8-H
4-H
7-H
8-H
3-H
6-H
7-H
3-H
6-H
7-H
3-H
6-H
7-H
3-H
6-H
7-H
3-H
6-H
7-H
3.82
3.72
3.78
4.04
3.92
4.14
9.4, 3.5, 1.3
9.9, 7.7, 2.4. 2.4
9.9
₁
8
9
W 4.4
d
8.4
5-H
4-H
4-H
4-H
4-H
₂
10.4, 6.4, 4.8, 2.4
10.4
2.3, 2.3
9.8, 5.0, 2.4, 2.4
9.8
m
d
W 21.7
8.4
10
11
12
13
2.4
10.0, 4.4, 2.7, 2.7
10.0, 2.4, 2.4, 2.4
1.8
m
m
W 20.7
W 16
9.9, 5.3, 2.3
9.9, 2.7
₁
W 1.7
₂
10.0, 3.7, 3.7
10.0
5.63
5.7
9.9, 7.4, 2.5
9.9
a All spectra recorded at 400 MHz in CDCl3. See Experimental for details.
stereochemical assignments demanded interpretative analysis
of spectrosopic results, aided by mechanistic inferences.
The ensuing comments identify salient features of these
assignments. The bicyclo[4.4.0]decene substructure of 6 was
evident from a self-consistent pattern of COSY correlations,
supported by evidence for a phenylsulfonylmethylene group,
and a trans-ring junction was assigned owing to the diagnostic
width of the 4a-proton signal. The latter assignment conferred
obligatory Z-orientation on the 5-substituent. Differentiation
of the cycloadducts 7 and 8 followed from a comparison of the
5-H signals, which revealed the expected multiplicities and
coupling magnitudes associated with vicinal and allylic coup-
lings in the appropriate conformers of each epimer, supported
by orientationally sensitive anisotropic deshielding of 4-H by
the PhSO2 group in 8. Similar patterns of differentiation were
discerned in both pairs of bicyclo[4.3.0]nonadiene epimers 9/10
and 11/12, and the C-4 configuration of 13 was based on
analogy.
Finally, an X-ray crystal structure determination on a repre-
sentative cycloadduct 8 confirmed the assignment8 and, by
extension, those of the epimer 7 and of the cycloadducts
assigned by comparative NMR analysis. Notably, the conform-
ation of 8 was indeed revealed to confer a nearly orthogonal
torsion angle relationship (88.9Њ) on 5β-H and 6α-H, thereby
rationalising the absence of vicinal coupling observed in the
NMR spectra of this and similarly assigned cycloadducts.
Scheme 2 Reagents and conditions: (i) C6H5CH3, 180 ЊC, 24 h; (ii)
C6H5CH3, 80 ЊC, 20 h; (iii) (a) MCPBA, CH2Cl2, 0 ЊC, 30 min, then
quenched by aq. NaHCO3; (b) CH2Cl2, 30 ЊC, 20 min; (iv) C6H5CH3,
150 ЊC, 2 h; (v) CDCl3, 50 ЊC, 2 h.
Mechanism and selectivity
A common feature of the foregoing experiments was the
exclusive pattern of [4 ϩ 2] cycloaddition behaviour in all cases.
Although the sometimes moderate yields of characterisable
products suggest that alternative or competing modes of reac-
tion may intervene in certain cases, we have not found evidence
to support this. Secondly, the relationship between tether length
and reactivity is compellingly demonstrated in the comparison
of reaction outcomes for 5a, 5b and 5c.
monitoring, which showed complete reaction after 2 h). Com-
bination of the foregoing structural features, exemplified by the
1,6-disubstituted substrate 5f, resulted in loss of IMDA reac-
tivity comparable to that of 5d, and apparent loss of selectivity,
suggested by the conversion of substrate into an intractable
mixture after 2 h at 150 ЊC.
The structural assignments of the cycloadducts 6–13 were
The poor result for the undecatetraene 5a is instructive, since
it clearly illustrates limited IMDA reactivity associated with a
tetramethylene tether, and preference for generation of a 6,6-
rather than a 6,7-fused ring system, consistent with the richly
exemplified former pathway in aliphatic triene substrates.1
However, the extent to which IMDA reaction occurs, with
attendant participation of the unactivated ∆2-bond of the
1
based largely upon extensive H and 13C NMR spectroscopy,
supported by COSY techniques. In general, the gross structures
of the cycloadducts were readily discerned from the presence,
the chemical shifts and the coupling relationships of signals for
the olefinic protons and, where applicable, for those of the
methine proton α- to the PhSO2 group (Table 2). Aspects of the
J. Chem. Soc., Perkin Trans. 1, 2000, 3129–3139
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phenylsulfonylallenyl terminus, suggests that transition state
alignment of the reaction centres rather than nascent ring size
is decisive, even in the presence of the more reactive ∆1-bond.
Thus, the observed reaction course accommodates a chair-like
tether orientation, whereas engagement of the ∆1-bond can
only proceed syn to C(3)–C(4), and thus encounters sterically
demanding or orientationally improbable juxtapositions of
reaction centres (Scheme 3). The isolation of trans-fused
product only, is not readily prefigured by comparison of the
respective exo- and endo-transition state alignments, but this
may not be meaningful in the light of poor overall recovery of
product.
The IMDA reaction rate for the decatetraene 5b is consider-
ably higher than that reported for the structurally analogous
1-phenylsulfonyldeca-1,7,9-triene,18 which requires treatment
at 140 ЊC for 44 h to furnish a single product arising from
exo-oriented cycloaddition. It is evident that the additional
geometrical constraint imposed by the inner π-bond of the
phenylsulfonylallenyl group of 5b, not only necessitates bond
formation syn to C(3)–C(4), but also facilitates favourable
alignment of the reaction termini. This constraint also appears
to relieve steric interactions between the PhSO2 and dienyl
groups, or within the tether, to an extent that allows some com-
peting participation by an endo-transition state (Scheme 3),
although exo-selectivity remains preponderant (~3:1). The
dienophilic reactivity of the phenylsulfonylallenyl terminus is
most dramatically manifested by the facility with which the
nonatetraene 5c undergoes IMDA reaction. It is inferred that
the factors responsible for reactivity in the foregoing example
are amplified here through highly advantageous juxtaposition
of reaction termini (Scheme 3) and by conservation of those
steric features which favour the exo-transition state leading to a
similar diastereomer distribution (~4:1). This level of reactivity
and stereoselectivity contrasts even more sharply with that of
1-phenysulfonylnona-1,6,8-triene,18 which required treatment at
140 ЊC for 44 h to give a ~1:1 mixture of exo- and endo-derived
cycloadducts.
Not surprisingly, the exceptional reactivity of 5c is some-
what suppressed in the 6-methylnonatetraene 5d, owing to the
introduction of an additional steric impediment at one reaction
terminus. Nevertheless, the substrate must enjoy a similar
intramolecular alignment of reaction centres during IMDA
reaction, since the isomer distribution for 5d is similar to that of
5c, although overall yields are reduced. The IMDA reaction
rate of compound 5e, which features a 1-alkyl chain attached
to the nonatetraene substructure, is also diminished in com-
parison with 5c, but remarkably little for this level of substi-
tution at the dienophilic terminus. Furthermore, the reaction
is highly efficient and stereoselective, implying that the endo-
relationship between the 1-alkyl chain and the diene terminus
imposes no adverse steric effects upon the exo-transition state
[cf. conformational drawing C(ii), Scheme 3], but rather,
reinforces it. A practical implication of the latter IMDA reac-
tion is that it offers a superior strategy for synthesis of
4-alkylhydrindanes (hydrindane = hexahydroindane), since
attempted base-mediated alkylation of cycloadducts 9 or 10
proceeds with poor diastereoselectivity. The evident complexity
of the reaction outcome involving the 1,6-dialkylnonatetraene
5f, suggests that this level of substitution and attendant steric
crowding result in diminished reactivity and selectivity.
Further synthetic applications
The foregoing results invited exploration of reactants in which
the 1-phenylsulfonylallenyl terminus is linked via an ethylene
tether to more elaborate dienyl substructures. In particular,
it was of interest to examine the scope for achieving IMDA
closure onto cyclic dienyl systems, in order to prepare more
elaborate bridged polycyclic structures. The record of success-
ful IMDA reactions involving furanyl dienes (‘IMDAF’ reac-
tions) with appropriately linked dienophilic allenyl groups19
suggested that the synthesis and IMDAF reaction of 5-(2-
furyl)-1-phenylsulfonylpenta-1,2-diene 17 would be an instruc-
tive first objective (Scheme 4).
3-(2-Furyl)propan-1-ol 1420 was converted, via sequential
oxidation, ethynylation and rearrangement, into the 1-
phenylsulfinylpenta-1,2-dienyl intermediate 16, in an overall
yield of 42%. Treatment of the sulfoxide 16 with MCPBA at
Ϫ10 ЊC for 30 min revealed evidence (TLC) of the expected
oxidation accompanied by further reaction, and a low-
temperature quench and work-up procedure was adopted in
an attempt to intercept the intermediate as well as derived
Scheme 3 Conformational perspectives of IMDA alignments for
undecatetraene 5a (A), decatetraene 5b (B), and nonatetraene 5c (C)
(E = SO2Ph).
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Scheme 4 Reagents and conditions: (i) Dess–Martin periodinane,
᎐
CH2Cl2, 20 ЊC; (ii) HC᎐CMgBr, THF, 20 ЊC; (iii) PhSCl, NEt3, Ϫ78 ЊC;
᎐
(iv) MCPBA, CH2Cl2, Ϫ10 ЊC; work-up at 0 ЊC.
Scheme 5 Reagents and conditions: (i) Li, NH3, EtOH; (ii) (CH2OH)2,
BF3ؒOEt2, THF; (iii) Dess–Martin periodinane, CH2Cl2, 25 ЊC; (iv)
products. An 1H NMR spectrum of the isolate revealed a three-
component mixture (10:2:1), in which the major product 19
(see below) was accompanied by components displaying signals
tentatively assigned to the obligatory phenylsulfonyl inter-
mediate 17 [δ 5.87 (td, J 2 × 7.0 and 6.2, 3-H) and 6.20 (dt, J 6.2
and 2 × 3.1, 1-H)] and an endo-cycloadduct 18 [δ 5.45 (m, 3-H),
4.42 (d, J 3.6, 4-H), 5.30 (dd, J 3.6 and 1.7, 5-H), 6.57 (dd, J 5.6
and 1.7, 6-H) and 6.54 (d, J 5.6, 7-H)].
᎐
HC᎐CMgBr, THF, 25 ЊC; (v) PhSCl, NEt3, CH2Cl2, Ϫ78 ЊC; (vi)
᎐
MCPBA, CH2Cl2, 25 ЊC; (vii) (a) TFA, 25 ЊC; (b) NaHCO3, 0 ЊC; (viii)
LDA, TMSCl, Ϫ78 ЊC→25 ЊC; (ix) KOH, THF–H2O–MeOH, 25 ЊC.
alcohol 22 in good overall yield. Phenylsulfenylation–
rearrangement, and subsequent MCPBA oxidation, without
isolation of the intermediate, gave the expected phenylsulfonyl-
allene 23. The modest overall yield (41%) was ascribed to losses
through competitive epoxidation of the isolated olefinic bond.
Deprotection of 23 with TFA proceeded smoothly to give the
4-substituted cyclohexenone 24 (92%), but ensuing enolisation
(LDA–THF, Ϫ78 ЊC), followed by attempted trapping with
chlorotrimethylsilane resulted in formation of a complex
mixture, chromatography of which furnished a minor fraction
Chromatography of the crude reaction product resulted in
isolation of the pure major product only (63%), the structure of
which was assigned as the exo-cycloadduct 19, on the basis of
convincing 1H NMR evidence. In addition to the readily identi-
fied olefinic proton signals at δ 5.75 (dt J 3.3 and 2 × 1.9, 3-H),
6.41 (dd, J 5.7 and 2.1, 6-H) and 6.50 (d, J 5.7, 7-H), those at
δ 3.65 (dt, J 3.4 and 2 × 1.9, 4-H) and 5.38 (d, J 2.1, 5-H) were
assigned with the aid of COSY correlations, which also
revealed an absence of vicinal coupling between 4-H and 5-H,
thereby confirming the orthogonal relationship between the
bridgehead and neighbouring endo-proton in the 7-oxanor-
bornanoid substructure. Further supporting evidence for the
assignment stemmed from the unexpected complexity of the
signal for 4-H, which displayed long range coupling to 2-H2 and
to 3-H, as verified through COSY correlations. Homoallylic
coupling is known to occur between allylic protons separated
by a π-bond,21 and typically ranges between 1.9 and 3.5 Hz
for cyclic systems, maximised by orthogonality between the
coupling partners. The conformation of 19 is compatible with
the assignment of 4-H multiplicity to homoallylic couplings
1
(12%) displaying H NMR signals consistent with a diastereo-
meric mixture (~5:1) of desilylated cycloadducts 25. Evidence
for the structure of the major component included signals at
δ 4.90 (q, J 3 × 2.2, 3-H), 6.12 (d, J 8.6, 6-H) and 6.10 (d, J 8.6,
7-H) for the olefinic protons and at 4.05 (br s) for 4-H, whereas
the minor component displayed a similar pattern of signals at
δ 5.65 (q, J 3 × 2.0, 3-H), 6.12 (d, J 8.6, 6-H), 5.60 (d, J 8.6, 7-H)
and 4.15 (br s, 4-H).
Although isolation of this minor fraction implies that
the putative tetraenyl substrate is indeed formed and readily
undergoes IMDA reaction, several sources of interference
militate against a preparatively useful outcome. Inadequate
regiocontrol during deprotonation–trapping, competitive iso-
merisation, inefficient trapping and substrate lability may all be
contributory, and attempts to improve the reaction sequence
through variations in reaction conditions and trapping agents
have hitherto failed. Nevertheless, the validity of this overall
strategy for synthesis of the target spiro system was demon-
strated through treatment of 25 with aqueous alkali to give 1-
(phenylsulfonylmethyl)spiro[4.5]deca-1,6-dien-8-one 26 (70%),
the structure of which was fully supported by analytical and
spectrosopic data. This product proved to be identical to a
minor by-product, noted during the exploratory phase of the
deprotection of the ketal 23 into the cyclohexenone intermedi-
ate 24, and raised the intriguing possibility that an IMDA–
fragmentation mediated protocol might be superfluous. Indeed,
deprotection of the ketal 23 with TFA, followed by immediate
treatment of the reaction mixture with aqueous alkali furnished
the spiro compound 26 (85%), in a simple and efficient one-
pot process, via a dienolate-initiated intramolecular Michael
5
4
5J2β,4 3.4 and J2α,4 1.9, together with an allylic coupling, J3,4
1.9.
The outcome of this experiment further demonstrates the
exceptional IMDA reactivity associated with the nonatetraenyl
structural motif, and the synthetic potential of this approach to
assembly of polycyclic ring systems. A further application was
suggested by the known facility with which cycloadducts
derived from phenyl vinyl sulfone and terminally oxygenated
dienes undergo base-mediated fragmentation,22 and entailed
synthesis of a 1-oxy-4-(5-phenylsulfonylpenta-3,4-dienyl)cyclo-
hexa-1,3-dienyl derivative, upon which to test the potential for
exploiting an IMDA–fragmentation sequence to synthesise
functionalised spiro[4.5]decanes (Scheme 5).
3-(4-Anisyl)propan-1-ol 2023 (prepared routinely from 4-
allylanisole) was subjected to sequential Birch reduction and
hydrolysis–ketalisation. Dess–Martin oxidation of the resultant
alcohol 21, followed by ethynylation furnished the propargyl
J. Chem. Soc., Perkin Trans. 1, 2000, 3129–3139
3133

View Article Online
reaction. Although tangential to the thrust of the IMDA
investigation, this serendipitous finding not only circumvents
the troublesome features of the former process, but opens a new
synthetic route to spiro[4.5]decanoid systems.
ether (1.54 g, 4.78 mmol; prepared from the reaction of pent-4-
yn-1-ol and tert-butyldiphenylchlorosilane in the presence of
pyridine) was added to a slurry of zirconocene hydrogen chlor-
ide (1.23 g, 4.78 mmol) in dichloromethane (20 cm3) in a vessel
protected from sunlight. The resulting homogeneous solution
was stirred at room temperature for 4 h, then iodine (1.34 g, 5.3
mmol) in dichloromethane (15 cm3) was added and the mixture
was stirred for a further 1 h. Water was added and the mixture
was extracted (Et2O). The extract was washed (Na2S2O3, water,
brine), dried (MgSO4) and evaporated under reduced pressure
to yield crude 5-iodopent-4-en-1-yl TBDPS ether (2.05 g) as a
yellow oil, δH 1.05 (9H, s, But), 1.65 (2H, m, 2-H2), 2.20 (2H, m,
3-H2), 3.66 (2H, t, J 6.1, 1-H2), 5.97 (1H, br d, J 14.3, 5-H), 6.50
(1H, dt, J 14.3 and 2 × 7.1, 4-H) and 7.40–7.80 (10H, m,
2 × Ph), which was used directly in the next step.
In conclusion, this study has shown that IMDA processes
mediated by a dienophilic 1-phenylsulfonylallenyl terminus
display strong dependence upon tether length, and that an
ethylene linker to the dienyl moiety imposes an ideal conform-
ational constraint for extraordinarily facile reaction in which
exo-product formation predominates. Extension of the model
study, to substrates featuring substitution or skeletal modifica-
tion of the nonatetraenyl substructure, reveals much potential
for further development and synthetic applications. Further-
more, the 1-phenylsulfonylallenyl grouping offers scope for
exploiting axial chirality to perform diastereocontrolled IMDA
reactions, in a novel approach to enantiopure cyclic intermedi-
ates for synthesis. Indeed, preliminary investigations support
this contention, and will form the subject of a forthcoming
publication.
Vinyltributyltin (1.26 cm3, 4.3 mmol) was added to
bis(triphenylphosphine)palladium() chloride (170 mg, 0.24
mmol) in N,N-dimethylformamide (20 cm3) at 25 ЊC, followed
by the vinyl iodide (2.05 g), and the resulting solution was
stirred at room temperature for 72 h. Ammonium hydroxide
(10% v/v, 20 cm3) was added and the reaction mixture was
extracted (Et2O). The extract was washed (water, brine), dried
(MgSO4) and evaporated under reduced pressure. The residue
was chromatographed on silica gel using ethyl acetate–hexane
(1:19) as eluent to yield hepta-4,6-dien-1-yl TBDPS ether (1.16
g, 70%) as a pale-yellow oil, δH 1.05 (9H, s, But), 1.68 (2H, m,
2-H2), 2.20 (2H, m, 3-H2), 3.66 (2H, t, J 6.1, 1-H2), 4.95 (1H, br
d, J 10.3, 7-Hcis), 5.08 (1H, br d, J 17.0 , 7-Htrans), 5.65 (1H, dt, J
15.2 and 2 × 6.6, 4-H), 6.05 (1H, dd, J 15.2 and 10.3, 5-H), 6.30
(1H, dt, J 17.0 and 2 × 10.3, 6-H) and 7.40–7.80 (10H, m,
2 × Ph). Treatment of the TBDPS ether (1.10 g, 3.14 mmol)
in THF (10 cm3) with tetrabutylammonium fluoride (3.2 cm3,
1 M solution in THF, 3.2 mmol) at room temperature for 2 h,
followed by addition of brine and extraction (Et2O) gave
material which was chromatographed on silica gel [ethyl
acetate–hexane (1:3)] to give hepta-4,6-dien-1-ol 1c (147 mg,
42%; 100% E).
Experimental
Melting points were determined using
a Reichert-Jung
Thermovar hot-stage microscope and are uncorrected. Infrared
spectra were recorded as chloroform solutions on a Perkin-
1
Elmer Paragon 1000 FT-IR spectrometer. H and 13C NMR
were recorded on a Varian VXR-200 instrument at 200 MHz,
a Varian Mercury at 300 MHz or a Varian Unity spectrometer
1
at 400 MHz. All H NMR spectra were recorded at 200 MHz
and 13C at 50 MHz in deuteriochloroform, unless otherwise
stated, using CHCl3 (δ 7.26) as internal standard. Chemical
shifts are reported as δ/ppm from tetramethylsilane, and J
values are given in Hz, using conventional descriptors for
multiplicities. Elemental analyses were performed using a
Fison’s Instruments Elemental Analyser EA1108. Mass spectra
were recorded on a VG micromass 16F spectrometer and
accurate mass determinations were performed on a Kratos
Limited MS9/50 spectrometer. All mass spectra data were
obtained using electron impact techniques unless otherwise
stated. Silica gel refers to Merck Kieselgel 60, 63–200 µm
for gravity chromatography and 40–60 µm for flash chroma-
tography. Unless otherwise stated, column chromatography was
performed using a substrate–adsorbent ratio of ~1:100 and
indicated solvent mixtures as eluents.
Compound 1d. Pent-4-yn-1-ol was subjected to sequential
zirconocene chloride mediated coupling followed by Stille
coupling with vinyltributyltin, using a procedure of Wender
and Tebbe,17 to give 4-methylhepta-4,6-dien-1-ol 1d (68% over
2 steps; 100% E).
Synthesis of dienynols 3
Synthesis of dienols 1
Compound 3a. A mixture of oxalyl chloride (0.2 cm3, 1.0
mmol) and dimethyl sulfoxide (0.15 cm3, 2.0 mmol) in dichloro-
methane (5 cm3) was stirred at Ϫ78 ЊC for 30 min, then
alcohol 1a (250 mg, 1.0 mmol) was added. After 30 min at
Ϫ78 ЊC, triethylamine (1.5 cm3, 10 mmol) was added, and the
solution was warmed to room temperature, water was added
and the mixture was extracted (CH2Cl2). The organic phase was
washed (water, brine), dried (MgSO4) and evaporated under
reduced pressure to give nona-6,8-dienal 2a (206 mg, 83%) as
an oil, whose spectroscopic properties were in agreement with
reported data.11
Compound 1a. Hexane-1,6-diol was converted, via sequential
mono-benzoylation, Swern oxidation, allylidenation, isomerisa-
tion and deprotection, into nona-6,8-dien-1-ol, which displayed
analytical and spectroscopic properties consistent with the
(6E)-isomer 1a,10 containing 12% of the (6Z)-isomer.
Compound 1b. Octa-5,7-dien-1-ol 1b (97% E) was prepared
from 2-allyltetrahydropyran following the procedure of
Schlosser et al.13
Compound 1c. Method 1. Orthoester Claisen rearrangement
of penta-1,4-dien-3-ol with triethyl orthoacetate, following a
literature procedure,14 gave ethyl hepta-4,6-dienoate (95% E).
The ester (560 mg, 3.6 mmol) in THF (5 cm3) at 0 ЊC was treat-
ed with diisobutylaluminium hydride (4 cm3, 6 mmol, 1.5 M
solution in toluene) for 1 h, the reaction was quenched with
1 M HCl, and the resultant mixture was extracted (EtOAc). The
organic phase was washed (water, brine), dried (MgSO4) and
evaporated under reduced pressure to give hepta-4,6-dien-1-ol
1c (350 mg, 86%; 95% E) as a colourless oil whose physical and
spectroscopic properties were in agreement with reported
data.14,24
Dry acetylene was bubbled vigorously through THF (40
cm3). After 30 min, a solution of hot ethylmagnesium bromide
[prepared by refluxing a mixture of magnesium (166 mg, 7.2
mmol), bromoethane (0.53 cm3, 7.2 mmol) and iodine (cat.)
in THF (40 cm3) for 2 h] was added, whilst maintaining the
passage of acetylene. After 30 min, the aldehyde 2a (520 mg,
3.77 mmol) was added and the mixture was stirred at room
temperature for 2 h. Sat. aqueous NH4Cl was added and the
mixture was extracted (Et2O). The organic phase was washed
(dil. HCl, water, brine), dried (MgSO4) and evaporated under
reduced pressure to yield undeca-8,10-dien-1-yn-3-ol 3a (540
mg, 87%; 88% E), νmax/cmϪ1 3684 (OH) and 3305 (C᎐C); δ (400
᎐
᎐
H
Method 2. Pent-4-yn-1-yl tert-butyldiphenylsilyl (TBDPS)
MHz) 1.60–1.80 (6H, m, 4-, 5- and 6-H2), 2.15 (2H, m, 7-H2),
3134
J. Chem. Soc., Perkin Trans. 1, 2000, 3129–3139

View Article Online
2.47 (1H, dd, J 2.3 and 0.8, 1-H), 4.40 (1H, td, J 2 × 6.3 and 2.3,
3-H), 4.95 (1H, dd, J 10.2 and 2.7, 11-Hcis), 5.10 (1H, dd, J 17.0
and 2.7, 11-Htrans), 5.70 (1H, dt, J 15.1 and 2 × 6.8, 8-H), 6.05
(1H, br dd, J 15.1 and 10.3, 9-H) and 6.32 (1H, dt, J 17.0 and
2 × 10.3, 10-H); δC (100 MHz) 24.5 and 28.7 (C-5 and C-6), 32.3
(C-7), 37.4 (C-4), 62.1 (C-3), 72.8 (C-1), 84.9 (C-2), 114.7
(C-11), 131.1 (C-9), 134.9 (C-8) and 137.2 (C-10); m/z 164
(Mϩ).
2.6 mmol) in THF (5 cm3), in the presence of iodine (catalytic)
and stirring for 1 h], followed by hepta-4,6-dienal 2c (330 mg,
3 mmol), and the resulting solution was stirred at room temper-
ature for 30 min. Saturated aq. NH4Cl was added and the
mixture was extracted (Et2O). The extract was washed (dil.
HCl, water, brine), dried (MgSO4) and evaporated. The residue
was chromatographed on silica gel [ethyl acetate–hexane (1:9)]
to afford the starting material (730 mg, 81%) followed by
dodeca-9,11-dien-4-yne-1,6-diol 1-TBDPS ether 3e (149 mg,
14%; 95% E) as a colourless oil, νmax/cmϪ1 3674 (OH) and 2228
Compound 3b. Alcohol 1b (150 mg, 1.19 mmol) in dichloro-
methane (2 cm3) was added to a stirred solution of pyridinium
chlorochromate (384 mg, 1.78 mmol) in dichloromethane (2
cm3) and the resulting mixture was stirred at room temperature
for 16 h. The supernatant was poured into a separate flask and
the residue was washed repeatedly with ether. The washings
were combined and the solvent evaporated to give octa-5,7-
dienal 2b (140 mg, 95%) as a volatile oil whose spectroscopic
properties were in agreement to those reported in the
literature.10,14
(C᎐C); δ (400 MHz) 1.05 (9H, s, But), 1.60 (4H, m, 2-H2 and
᎐
᎐
H
7-H2), 2.24 (2H, q, J 6.6, 8-H2), 2.36 (1H, td, J 2 × 7.0 and 2.0,
3-H2), 3.74 (2H, t, J 6.0, 1-H2), 4.36 (1H, m, 6-H), 4.95 (1H, br
d, J 10.2, 12-Hcis), 5.10 (1H, dd, J 17.1 and 1.1, 12-Htrans), 5.70
(1H, dt, J 15.1 and 2 × 6.6, 9-H), 6.10 (1H, dd, J 15.1 and 10.2,
10-H), 6.32 (1H, dt, J 17.1 and 10.2, 11-H) and 7.40–7.70 (10H,
m, Ph); δC (100 MHz) 15.1 (C-2), 19.2 (CMe3), 26.8 (CMe3),
28.2 (C-8), 31.4 (C-3), 37.3 (C-7), 62.0, 62.3 (C-1 and C-6), 81.1
(C-4), 85.3 (C-5), 115.1 (C-12), 127.6 (Ph), 129.5 (Ph), 131.5
(C-10), 133.7 (C-9), 133.8 (Ph), 135.5 (Ph) and 137.0 (C-11);
m/z 375 (Mϩ Ϫ But).
Ethynylation of the crude aldehyde 2b (2.4 g, 19 mmol) as
described in the foregoing experiment gave deca-7,9-dien-1-yn-
3-ol 3b (1.92 g, 67%; 97% E) as a colourless oil, νmax/cmϪ1 3684
Compound 3f. n-BuLi (0.95 cm3, 2.4 mmol, 2.5 M solution in
hexanes) was added to prop-2-yn-1-yl TBDPS ether (705 mg,
2.4 mmol) in THF (20 cm3) at Ϫ78 ЊC, followed by 4-
methylhepta-4,6-dienal 2d (300 mg, 2.4 mmol). After 1 h at
Ϫ78 ЊC, 1 M HCl was added and the product was isolated by
extraction (Et2O) as above, and chromatographed on silica gel
[ethyl acetate–hexane (1:9)] to yield 7-methyldeca-7,9-dien-2-
᎐
(OH) and 3305 (C᎐C); δ 1.50–1.80 (4H, m, 4 and 5-H2), 2.15
᎐
H
(2H, q, J 6.7, 6-H2), 2.47 (1H, d, J 2.3, 1-H), 4.38 (1H, td, J
2 × 6.3 and 2.3, 3-H), 4.95 (1H, dd, J 10.2 and 2.7, 10-Hcis), 5.10
(1H, dd, J 17.0 and 2.7, 10-Htrans), 5.70 (1H, dt, J 15.2 and
2 × 6.7, 7-H), 6.05 (1H, dd, J 15.1 and 10.3, 8-H) and 6.32 (1H,
dt, J 17.0 and 2 × 10.2, 9-H); δC 24.6 (C-5), 32.1 (C-6), 37.1
(C-4), 62.1 (C-3), 73.0 (C-1), 84.8 (C-2), 115.0 (C-10), 131.9 (C-
8), 134.4 (C-7) and 137.0 (C-9); m/z 150 (Mϩ).
yne-1,4-diol 1-TBDPS ether 3f (420 mg, 42%; 100% E), νmax
/
cmϪ1 3603 (OH) and 2252 (C᎐C); δ (400 MHz) 1.05 (9H,
᎐
᎐
H
s, But), 1.72 (2H, m, 5-H2), 1.74 (3H, s, 7-Me), 2.18 (2H, t, J
7.8, 6-H2), 4.27 (1H, br, W 10, 4-H), 4.38 (2H, d, J 1.6, 1-H2),
4.98 (1H, br d, J 10.6, 10-Hcis), 5.09 (1H, dd, J 16.7 and 1.8,
10-Htrans), 5.85 (1H, br d, J 10.9, 8-H), 6.56 (1H, dt, J 16.7 and
2 × 10.6, 9-H) and 7.40–7.70 (10H, m, Ph); δC (100 MHz) 16.6
(Me), 19.2 (CMe3), 26.7 (CMe3), 35.0, 35.6 (C-5 and C-6), 52.7
(C-1), 62.0 (C-4), 83.6 (C-2), 86.0 (C-3), 115.1 (C-10), 126.0
(C-8), 127.7 (Ph), 129.8 (Ph), 133.0 (C-9), 133.3 (Ph), 135.7 (Ph)
and 138.3 (C-7); m/z 361 (Mϩ Ϫ But).
Compound 3c. A solution of the alcohol 1c (890 mg, 7.95
mmol) and Dess–Martin periodinane (4.45 g, 10.5 mmol) in
dichloromethane (25 cm3) was stirred at room temperature for
1 h. Saturated aq. NaHCO3–Na2S2O3 (5:1) was added and the
solution was stirred for a further 1 h. The mixture was extracted
(Et2O) and the organic phase was washed (NaHCO3, water,
brine), dried (MgSO4) and evaporated under reduced pressure
to yield hepta-4,6-dienal (800 mg, 92%) as a pungent volatile
oil, whose spectroscopic properties corresponded to those
reported.24 The aldehyde was used directly without further
purification. Ethynylation of the crude aldehyde 2c as described
previously, gave nona-6,8-dien-1-yn-3-ol 3c (900 mg, 91%;
Phenylsulfenylation–[2,3]sigmatropic rearrangement of
propargylic alcohols 3
95% E) as a colourless oil, νmax/cmϪ1 3684 (OH) and 3305
General method. Triethylamine (3.74 mmol) was added to a
stirred solution of dienynol 3 (3.29 mmol) in THF (5 cm3) at
Ϫ78 ЊC, followed by benzenesulfenyl chloride (3.74 mmol).
After 1 h at Ϫ78 ЊC the solution was allowed to warm to room
temperature, aq. NH4Cl was added and the mixture was
extracted (EtOAc). The extract was washed (brine), dried
(MgSO4) and evaporated under reduced pressure. The residue
was chromatographed on silica gel to give the phenylsulfinyl-
tetraene 4 as a mixture of S-diastereomers.
᎐
(C᎐C); δ (400 MHz) 1.60 (2H, m, 4-H2), 2.30 (2H, q, J 6.7,
᎐
H
5-H2), 2.48 (1H, d, J 1.8, 1-H), 4.40 (1H, br t, J 5.8, 3-H), 4.95
(1H, dd, J 10.2 and 2.7, 9-Hcis), 5.10 (1H, dd, J 17.0 and 2.7,
9-Htrans), 5.70 (1H, dt, J 15.2 and 2 × 6.7, 6-H), 6.10 (1H,
dd, J 15.5 and 10.2, 7-H) and 6.32 (1H, dt, J 17.0 and
2 × 10.3, 8-H); δC (100 MHz) 28.0 (C-5), 36.9 (C-4), 61.7
(C-3), 73.2 (C-1), 84.6 (C-2), 115.4 (C-9), 131.9 (C-7), 133.4
(C-6) and 136.9 (C-8); m/z 136.0868 (Mϩ. C9H12O requires M,
136.0888).
1-Phenylsulfinylundeca-1,2,8,10-tetraene 4a. (77%) Eluent
᎐ ᎐
Compound 3d. Sequential Dess–Martin oxidation of 1d,
followed by ethynylation, as described in the previous experi-
ment, gave 6-methylnona-6,8-dien-1-yn-3-ol 3d (74% over two
ethyl acetate–hexane (1:9); νmax/cmϪ1 1948 (C᎐C᎐C) and 1042
(SO); δH (400 MHz) 1.60–1.90 (4H, m, 5- and 6-H2), 2.15–2.25
(4H, m, 4- and 7-H2), 4.98 (1H, dd, J 10.2 and 2.7, 11-Hcis), 5.10
(1H, dd, J 17.0 and 2.7, 11-Htrans), 5.67 (1H, dt, J 15.1 and
2 × 6.7, 8-H), 5.68–5.73 (1H, m, 3-H), 6.05 (2H, m, 1-, and 9-
H), 6.30 (1H, dt, J 17.0 and 2 × 10.2, 10-H) and 7.52–7.90 (5H,
m, SOPh); δC (100 MHz) 27.9 and 28.1 (C-5 and C-6), 28.4
(C-4), 32.0 (C-7), 99.1 (C-1), 102.7 (C-3), 114.8 (C-11), 124.2
(SOPh), 129.1 (SOPh), 130.9 (SOPh), 131.2 (C-9), 134.7 (C-8),
137.1 (C-10), 144.8 (SOPh) and 203.7 (C-2); m/z 272.1140 (Mϩ.
C17H20OS requires M, 272.1130).
steps; 100% E), νmax/cmϪ1 3687 (OH) and 3305 (C᎐C); δ (400
᎐
᎐
H
MHz) 1.78 (3H, br s, 6-Me), 1.86 (2H, m, 4-H2), 2.26 (2H, t, J
7.8, 5-H2), 2.48 (1H, d, J 2.0, 1-H), 4.37 (1H, m, 3-H), 5.00 (1H,
br d, J 10.6, 9-Hcis), 5.12 (1H, dd, J 16.9 and 1.8, 9-Htrans), 5.90
(1H, dd, J 10.6 and 0.9, 7-H) and 6.58 (1H, dt, J 16.9 and
2 × 10.6, 8-H); δC (100 MHz) 16.6 (C-Me), 35.0, 35.6 (C-4 and
C-5), 61.8 (C-3), 73.2 (C-1), 84.6 (C-2), 115.2 (C-9), 126.1 (C-8),
133.0 (C-6) and 138.0 (C-7); m/z 150.1035 (Mϩ. C10H14O
requires M, 150.1044).
Compound 3e. Pent-4-yn-1-yl TBDPS ether (0.9 g, 2.8 mmol)
was added to ethylmagnesium bromide [prepared by treatment
of magnesium (62 mg, 2.6 mmol) with bromoethane (0.2 cm3,
1-Phenylsulfinyldeca-1,2,7,9-tetraene 4b. (65%) Eluent ethyl
᎐ ᎐
δH 1.65 (2H, m, 5-H2), 2.10–2.25 (4H, m, 4- and 6-H2), 4.96 (1H,
acetate–hexane (1:10); νmax/cmϪ1 1950 (C᎐C᎐C) and 1037 (SO);
J. Chem. Soc., Perkin Trans. 1, 2000, 3129–3139
3135

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dd, J 10.2 and 2.7, 10-Hcis), 5.10 (1H, dd, J 17.0 and 2.7,
10-Htrans), 5.70 (2H, m, 3-H and 7-H), 6.05 (2H, m, 1-H and
8-H), 6.30 (1H, dt, J 17.0 and 10.2, 9-H) and 7.50 (5H, m,
SOPh); δC (C-5), 28.5 (C-4), 31.7 (C-6), 98.9 (C-1), 102.8 (C-3),
115.2 (C-10), 124.2 (SOPh), 129.1 (SOPh), 130.9 (SOPh), 131.2
(C-8), 134.7 (C-7), 137.0 (C-9), 144.8 (SOPh) and 203.7 (C-2);
m/z 258.1070 (Mϩ. C16H18OS requires M, 258.1077).
(SO2Ph), 134.6 (C-8), 137.1 (C-10), 141.3 (SO2Ph) and 205.5
(C-2); m/z 288.1091 (Mϩ. C17H20O2S requires M, 288.1079).
1-Phenylsulfonyldeca-1,2,7,9-tetraene 5b. (53%) Eluent ethyl
᎐ ᎐
acetate–hexane (1:5); νmax/cmϪ1 1956 (C᎐C᎐C), 1307 and 1149
(SO); δH (400 MHz) 1.49 (2H, quintet, J 4 × 7.5, 5-H2), 2.10–
2.15 (4H, m, 4- and 6-H2), 4.96 (1H, dd, J 10.2 and 2.7, 10-Hcis),
5.10 (1H, dd, J 17.0 and 2.7, 10-Htrans), 5.60 (1H, dt, J 15.2 and
2 × 6.7, 7-H), 5.85 (1H, td, J 2 × 7.0 and 6.2, 3-H), 6.05 (1H,
dd, J 15.2 and 10.2, 8-H), 6.20 (1H, dt, J 6.2 and 2 × 3.1, 1-H),
6.28 (1H, dt, J 17.0 and 2 × 10.2, 9-H) and 7.56–7.90 (5H, m,
SO2Ph); δC (100 MHz) 27.0 (C-5), 27.7 (C-4), 31.6 (C-6), 100.9
(C-1), 101.2 (C-3), 115.2 (C-10), 127.6 (SO2Ph), 129.1 (SO2Ph),
131.7 (SO2Ph), 133.3 (C-8), 133.8 (C-7), 137.0 (C-9), 141.4
(SO2Ph) and 205.7 (C-2); m/z 275 (Mϩ ϩ H).
1-Phenylsulfinylnona-1,2,6,8-tetraene 4c. (69%) Eluent ethyl
᎐ ᎐
acetate–hexane (1:4); νmax/cmϪ1 1950 (C᎐C᎐C) and 1037 (SO);
δH (400 MHz) 2.25 (4H, m, 4- and 5-H2), 5.00 (1H, dd, J 10.2
and 2.7, 9-Hcis), 5.12 (1H, dd, J 17.0 and 2.7, 9-Htrans), 5.60–5.75
(2H, m, 3-H and 6-H), 6.05 (2H, m, 1-H and 7-H), 6.30 (1H, dt,
J 17.0 and 2 × 10.3, 8-H) and 7.50–7.65 (5H, m, SOPh); δC (100
MHz, CDCl3) 27.7 (C-4) 31.5 (C-5), 98.5 (C-1), 103.1 (C-3),
115.7 (C-9), 124.2 (SOPh), 129.1 (SOPh), 130.9 (SOPh), 132.3
(C-7), 132.7 (C-6), 136.9 (C-8), 144.8 (SOPh) and 203.6 (C-2),
m/z 245 (Mϩ ϩ H).
6-Methyl-1-phenylsulfonylnona-1,2,6,8-tetraene 5d. (50%)
᎐ ᎐
Eluent ethyl acetate–hexane (1:5); νmax/cmϪ1 1956 (C᎐C᎐C),
1320 and 1148 (SO); δH (400 MHz) 1.72 (3H, s, 6-Me), 2.16 (2H,
t, J 7.6, 5-H2), 2.28 (2H, m, 4-H2), 5.02 (1H, br d, J 10.5, 9-Hcis),
5.08 (1H, dd, J 16.9 and 2.0, 9-Htrans), 5.85 (2H, m, 7-H), 5.87
(1H, td, J 2 × 6.9 and 6.0, 3-H), 6.20 (1H, dt, J 6.0 and 2 × 3.0,
1-H), 6.54 (1H, dt, J 16.9 and 2 × 10.5, 8-H) and 7.50–7.95 (5H,
m, SO2Ph); δC (100 MHz) 16.5 (Me), 26.0 (C-4), 38.2 (C-5),
100.5 (C-1), 101.5 (C-3), 115.6 (C-9), 126.6 (C-7), 127.6
(SO2Ph), 129.1 (SO2Ph), 132.9 (C-8), 133.4 (SO2Ph), 137.1
(C-6), 141.4 (SO2Ph) and 205.6 (C-2); m/z 274 (Mϩ).
6-Methyl-1-phenylsulfinylnona-1,2,6,8-tetraene 4d. (57%)
᎐ ᎐
Eluent ethyl acetate–hexane (1:4); νmax/cmϪ1 1949 (C᎐C᎐C) and
1037 (SO); δH (400 MHz) 1.75 (3H, s, 6-Me), 2.15–2.30 (4H, m,
4-H2 and 5-H2), 5.02 (1H, br d, J 9.9, 9-Hcis), 5.12 (1H, m,
9-Htrans), 5.60 (1H, m, 3-H), 5.85 (1H, m, 7-H), 6.05 (1H, dt, J
5.7 and 2 × 2.7, 1-H), 6.30 (1H, m, 8-H) and 7.50–7.65 (5H, m,
SOPh); δC (100 MHz) 16.5 (Me), 26.5 (C-4), 38.5 (C-5), 98.6
(C-1), 103.0 (C-3), 115.4 and 115.6 (C-9), 124.2 and 124.3
(SOPh), 126.6 (C-7), 129.2 (SOPh), 130.9 and 131.0 (SOPh),
133.0 and 132.9 (C-8), 137.3 (C-6), 144.9 (SOPh) and 203.5
(C-2); m/z 258.1066 (Mϩ. C16H18OS requires M, 258.1078).
1-(tert-Butyldiphenylsilyloxy)-4-phenylsulfonyldodeca-
4,5,9,11-tetraene 5e. (70%) Eluent ethyl acetate–hexane (1:10);
νmax/cmϪ1 1960 (C᎐C᎐C), 1306 and 1149 (SO); δ (400 MHz)
᎐ ᎐
H
1-(tert-Butyldiphenylsilyloxy)-4-phenylsulfinyldodeca-
4,5,9,11-tetraene 4e. (68%) Eluent ethyl acetate–hexane (1:10);
νmax/cmϪ1 1956 (C᎐C᎐C) and 1045 (SO); δ (400 MHz) 0.95
1.10 (9H, s, But), 2.16 (2H, m, 8-H2), 2.18–2.36 obsc. (2H, m,
2-H2), 2.38 (2H, td, J 2 × 7.0 and 2.0, 3-H2), 3.60 (2H, t, J 6.2,
1-H2), 4.95 (1H, br d, J 10.2, 12-Hcis), 5.10 (1H, dd, J 17.1 and
1.1, 12-Htrans), 5.65 (1H, dt, J 15.1 and 2 × 7.0, 9-H), 5.70 (1H,
m, 6-H), 6.02 (1H, dd, J 15.1 and 10.2, 10-H), 6.28 (1H, dt, J
17.1 and 10.2, 11-H) and 7.30–7.70 (15H, m, Ph); δC (100 MHz)
19.1 (C-2), 23.3 (CMe3), 26.8 (CMe3), 27.7 (C-7), 30.5, 31.3 (C-3
and C-8), 62.5, (C-1), 100.7 (C-6), 113.7 (C-4), 115.6 (C-12),
122.8, 127.6, 128.0, 129.5 (Ph), 130.5 (C-10), 132.1 (Ph), 133.0,
133.2 (Ph), 133.7 (C-9), 135.5 (Ph), 136.7 (C-11), 140.4 (Ph) and
203.8 (C-5); m/z (Electrospray) 579 (Mϩ ϩ Na).
᎐ ᎐
H
(9H, s, But), 3.58 (2H, m, 1-H2), 4.95 (1H, m, 12-Hcis), 5.10 (1H,
m, 12-Htrans), 5.66 (2H, m, 6-H and 9-H), 6.07 (1H, m, 10-H),
6.28 (1H, m, 11-H) and 7.40–7.70 (15H, m, Ph) as a colourless
oil, which was used directly in the next step.
1-(tert-Butyldiphenylsilyloxy)-2-phenylsulfinyl-7-methyldeca-
2,3,7,9-tetraene 4f. (28%) Eluent ethyl acetate–hexane (1:5);
νmax/cmϪ1 1956 (C=C᎐C) and 1038 (SO); δ (400 MHz) 0.93
᎐
H
(9H, s, But), 1.71, 1.73 (3H, s, 7-Me), 4.20 (1H, m, 1-H), 4.43
(1H, m, 1-H), 4.98 (1H, br m, 10-Hcis), 5.09 (1H, br m,
10-Htrans), 5.65 (1H, m, 3-H), 5.85 (1H, br m, 8-H), 6.52 (1H, br
m, 9-H) and 7.30–7.60 (15H, m, Ph); m/z 469 (Mϩ Ϫ But).
1-(tert-Butyldiphenylsilyloxy)-2-phenylsulfonyl-7-methyldeca-
2,3,7,9-tetraene 5f. (48%) Eluent acetate–hexane (1:10); νmax
/
cmϪ1 1959 (C᎐C᎐C), 1307 and 1151 (SO); δ (400 MHz) 0.93
᎐ ᎐
H
(9H, s, But), 1.72 (3H, s, 7-Me), 2.12 (2H, t, J 7.8, 6-H2), 2.25
(2H, m, 5-H2), 4.48 (2H, m, 1-H2), 4.98 (1H, br d, J 10.6,
10-Hcis), 5.10 (1H, dd, J 16.7 and 1.8, 10-Htrans), 5.80 (2H, m, 4-
H and 8-H), 6.53 (1H, dt, J 16.7 and 2 × 10.6, 9-H) and 7.30–
7.90 (15H, m, Ph); δC (100 MHz) 16.5 (C-Me), 19.1 (CMe3),
26.2 (C-5), 26.6 (CMe3), 38.4 (C-6), 60.3 (C-1), 100.8 (C-4),
113.4 (C-2), 115.5 (C-10), 126.5 (C-8), 127.7, 127.8, 129.8, 132.7
(Ph), 132.9 (C-9), 133.1 (Ph), 133.3 (Ph), 135.4 (Ph), 137.4 (C-7)
and 205.3 (C-3); m/z 542 (Mϩ).
Oxidation of the phenylsulfinyltetraenes 4
General procedure. m-Chloroperbenzoic acid (MCPBA) (1.1
mmol) was added to a solution of the phenylsulfinyltetraene
4 (1.1 mmol) in dichloromethane (15 cm3) at 0 ЊC, and the
mixture was allowed to warm to room temperature. After 1 h at
room temperature, aq. NH4Cl was added and the mixture was
extracted (EtOAc). The organic phase was washed (dil. HCl,
water, brine), dried (MgSO4) and evaporated under reduced
pressure, and the residue was chromatographed on silica gel to
give the phenylsulfonyltetraene 5.
Intramolecular Diels–Alder reactions of the phenylsulfonyl-
tetraenes 5
1-Phenylsulfonylundeca-1,2,8,10-tetraene 5a. (66%) Eluent
᎐ ᎐
Compound 6. A solution of undecatetraene 5a (100 mg, 0.35
mmol) in toluene (2 cm3) was flushed with nitrogen and heated
at 180 ЊC (sealed tube) for 20 h. The solvent was evaporated and
the residue was chromatographed on silica gel [ethyl acetate–
toluene (1:50)] to yield (5Z,4aR*,8aR*)-5-(phenylsulfonyl)-
ethyl acetate–hexane (1:4); νmax/cmϪ1 1955 (C᎐C᎐C), 1319 and
1148 (SO); δH (400 MHz) 1.38–1.43 (4H, m, 5- and 6-H2), 2.15–
2.25 (4H, m, 4- and 7-H2), 4.96 (1H, dd, J 10.2 and 2.7, 11-
Hcis), 5.10 (1H, dd, J 17.0 and 2.7, 11-Htrans), 5.66 (1H, dt, J 15.1
and 2 × 6.7, 8-H), 5.83 (1H, td, J 2 × 7.0 and 6.2, 3-H), 6.05
(1H, br dd, J 15.1 and 10.2, 9-H), 6.19 (1H, dt, J 6.2 and
2 × 3.1, 1-H), 6.30 (1H, dt, J 17.0 and 2 × 10.2, 10-H) and 7.50–
7.90 (5H, m, SO2Ph); δC (100 MHz) 27.5 and 27.8 (C-5 and
C-6), 28.3 (C-4), 32.0 (C-7), 101.0 (C-1), 101.2 (C-3), 114.9
(C-11), 127.2 (SO2Ph), 129.1 (SO2Ph), 131.2 (C-9), 133.3
methylene-1,2,3,4,4a,5,6,8a-octahydronaphthalene
6 (30 mg,
30%) as a gum, νmax/cmϪ1 1321 and 1146 (SO); δH (400 MHz,
C6D6) 1.20–1.85 (8H, m, 1-, 2-, 3- and 4-H2), 2.12 (1H, dd, J
15.1 and 6.1, 6α-H), 2.27 (1H, ddt, J 15.1, 4.8 and 2 × 2.9,
6β-H), 2.70 (1H, br m, W 29, 4a-H), 5.43 (1H, dddd, J 8.8, 6.1,
4.8 and 2.9, 7-H), 5.52 (1H, dt, J 8.8 and 2.9, 8-H), 5.85 (1H, m,
3136
J. Chem. Soc., Perkin Trans. 1, 2000, 3129–3139

View Article Online
W 4.5, 1Ј-H) and 6.84–7.82 (5H, dd, J 7.6 and 1.3, SO2Ph);
δC (100 MHz, C6D6) 26.3, 26.8, 31.6, 33.4 (t, C-1, C-2, C-3 and
C-4), 36.5 (t, C-6), 42.3 (d, C-8a), 45.1 (d, C-4a), 124.0 (d, C-1Ј),
124.6 (d, C-8), 127.0 (d, SO2Ph), 128.6 (d, SO2Ph), 132.1
(d, SO2Ph), 135.9 (d, C-7), 143.7 (s, SO2Ph) and 160.7 (s, C-5);
m/z 288.1192 (Mϩ. C17H20O2S requires M, 288.1183).
133.0 (SO2Ph), 134.1 (C-3a) and 140.0 (SO2Ph), followed by
(4R*,7aR*)-4-phenylsulfonyl-2,4,5,7a-tetrahydro-1H-indene 10
(175 mg, 50%), mp 76–78 ЊC (from ethanol) (Found: C, 69.3; H,
6.2; S, 12.1%; Mϩ ϩ H, 261. C15H16O2S requires C, 69.2; H, 6.2;
S, 12.3%; M, 260); νmax/cmϪ1 1334 and 1148 (SO); δH (400 MHz)
1.40 (1H, dq, J 12.7 and 11.0, 1β-H), 2.20 (3H, m, 1α-H and
2-H2), 2.53 (1H, ddq, J 19.5, 8.4 and 3 × 2.7, 5β-H), 3.00 (1H,
₁
Compounds 7 and 8. A solution of decatetraene 5b (400 mg,
1.46 mmol) in toluene (30 cm3) was flushed with nitrogen and
heated at 80 ЊC (sealed tube) for 20 h. The solvent was evapor-
ated and the residue was chromatographed on silica gel [ethyl
acetate–toluene (1:50)] to give (5S*,8aR*)-5-phenylsulfonyl-
1,2,3,5,6,8a-hexahydronaphthalene 7 (70 mg, 18%), mp 110–
113 ЊC (from isopropyl alcohol) (Found: C, 70.0; H, 6.5; S,
11.6%; Mϩ, 274. C16H18O2S requires C, 70.1; H, 6.6; S, 11.7%;
M, 274); νmax/cmϪ1 1306 and 1142 (SO); δH (400 MHz) 1.18 (1H,
qd, J 3 × 12.9 and 2.8, 1β-H), 1.50 (1H, qdd, J 3 × 12.9, 6.3 and
2.8, 2α-H), 1.75 (1H, m, W 29, 2-H), 1.90 (1H, m, W 25, 5-H),
2.20 (3H, m, 6-H and 3-H2), 2.61 (1H, m, W 36, 6-H), 2.76 (1H,
ddq, J 19.5, 4.4 and 3 × 2.3, 5α-H), 3.38 (1H, m, W 10.5, 7a-H),
₂

4.04 (1H, d, J 8.4, 4β-H), 5.37 (1H, br d, J 2.4, 3-H), 5.57 (1H,
ddt, J 10.0, 4.4 and 2 × 2.7, 6-H), 5.73 (1H, dq, J 10.0 and
3 × 2.4, 7-H) and 7.57–7.82 (5H, m, SO2Ph); δC (100 MHz) 24.7
(t, C-5), 31.5 (t, C-1), 31.6 (t, C-2), 41.0 (d, C-7a), 62.0 (d, C-4),
121.7 (d, C-6), 128.7 (d, SO2Ph), 128.8 (d, SO2Ph), 131.3 (d,
C-7), 132.7 (d, C-3), 133.5 (d, SO2Ph), 135.0 (s, C-3a) and 137.7
(s, SO2Ph).
Compounds 11 and 12. A solution of the 6-methylnona-
tetraene 5d (60 mg, 0.21 mmol) in toluene (2 cm3) was flushed
with nitrogen and heated at 150 ЊC (sealed tube) for 2 h. The
solvent was evaporated and the residue was chromatographed
on silica gel [ethyl acetate–toluene (1:99)] to yield (4S*,7aR*)-
₁
br m, W 7.0, 8a-H), 3.82 (1H, ddd, J 9.4, 3.5 and 1.3, 5-H), 5.43
₂
(1H, br d, J 9.9, 8-H), 5.52 (1H, dddt, J 9.9, 7.7 and 2 × 2.4,
7-H), 6.55 (1H, br d, J 2.0, 4-H) and 7.55–7.90 (5H, m, SO2Ph);
δC (100 MHz) 21.4 (t, C-2), 25.5 (t, C-6), 28.8 (t, C-3), 30.2 (t,
C-1), 37.6 (d, C-8a), 64.5 (d, C-5), 122.4 (d, C-7), 125.1 (d, C-4),
128.6 (d, SO2Ph), 128.8 (s, C-4a), 128.9 (d, SO2Ph), 132.2 (d,
C-8), 133.5 (d, SO2Ph) and 139.1 (s, SO2Ph). Further elution
furnished (5R*,8aR*)-5-phenylsulfonyl-1,2,3,5,6,8a-hexahydro-
naphthalene 8 (214 mg, 54%), mp 123–125 ЊC (from ethanol)
(Found: C, 70.2; H, 6.7; S, 11.9%; Mϩ, 274. C16H18O2S requires
C, 70.1; H, 6.6; S, 11.7%; M, 274); νmax/cmϪ1 1302 and 1146
(SO); δH (400 MHz) 0.95 (1H, qd, J 3 × 12.4 and 2.4, 1β-H),
1.49 (1H, qdd, J 3 × 12.4, 5.6 and 2.8, 2α-H), 1.80–1.95 (4H, m,
1-H, 2-H and 3-H2), 2.55 (1H, dddd, J 19.8, 8.4, 6.4 and 2.4,
7a-methyl-4-phenylsulfonyl-2,4,5,7a-tetrahydro-1H-indene
11
(8 mg, 13%) as an oil, νmax/cmϪ1 1307 and 1146 (SO); δH (400
MHz) 1.60 (3H, s, 7a-Me), 1.69 (1H, td, J 2 × 12.3 and 9.6,
1β-H), 1.78 (1H, ddd, J 12.3, 7.1 and 1.4, 1α-H), 2.20 (1H, dtd,
J 16.4, 2 × 5.3 and 1.4, 5-H), 2.38 (1H, m, 2-H), 2.50–2.70 (2H,
m, 2-H and 5-H), 3.92 (1H, m, W 20.7, 4-H), 5.38 (1H, ddd,
J 9.9, 5.3 and 2.3, 6-H), 5.65 (1H, dd, J 9.9 and 2.7, 7-H), 6.10
(1H, br d, J 1.8, 3-H) and 7.40–7.80 (5H, m, SO2Ph); δC (100
MHz) 24.8 (Me), 28.5 (C-5), 30.3 (C-1), 37.7 (C-2), 49.4 (C-7a),
59.9 (C-4), 119.7 (C-6), 124.3 (SO2Ph), 128.5 (SO2Ph), 129.1
(SO2Ph), 133.6 (C-3), 137.6 (C-7), 138.7 (s, SO2Ph) and 138.7
(C-3a); m/z 274.1012 (Mϩ. C16H18O2S requires M, 274.1023).
Further
elution
furnished
(4R*,7aR*)-7a-methyl-4-
₁
6β-H), 3.00 (1H, dd, J 19.8 and 4.8, 6α-H), 3.06 (1H, m, W 7.0,
₂

phenylsulfonyl-2,4,5,7a-tetrahydro-1H-indene 12 (27 mg, 45%)
as a gum, νmax/cmϪ1 1306 and 1146 (SO); δH (400 MHz) 1.15
(3H, s, 7a-Me), 1.75 (1H, td, J 2 × 11.7 and 8.7, 1β-H), 1.83
(1H, dd, J 11.7 and 6.7, 1α-H), 2.18 (1H, ddd, J 16.5, 8.7 and
3.5, 2β-H), 2.45 (2H, m, 2α-H and 5-H), 2.75 (1H, br d, J 18.3,
5-H), 4.14 (1H, m, W 16, 4-H), 5.55 (1H, dt, J 10.0 and 2 × 3.7,
₁
8a-H), 3.72 (1H, d, J 8.4, 5-H), 5.25 (1H, m, W 4.4, 4-H), 5.57
₂

(1H, br d, J 10.4, 8-H), 5.65 (1H, dddd, J 10.4, 6.4, 4.8 and 2.4,
7-H) and 7.50–7.85 (5H, m, SO2Ph); δC (100 MHz) 21.0 (t, C-2),
24.5 (t, C-6), 26.0 (t, C-3), 29.8 (t, C-1), 33.7 (d, C-8a), 67.9
(d, C-5), 121.4 (d, C-7), 128.6 (d, SO2Ph), 128.9 (s, SO2Ph),
129.2 (s, C-4a), 130.9 (d, C-8), 132.2 (d, C-4), 133.3 (d, SO2Ph)
and 137.6 (s, SO2Ph).
₁
6-H), 5.60 (1H, m, W 1.7, 3-H), 5.82 (1H, br d, J 10.0, 7-H) and
₂

7.50–7.90 (5H, m, SO2Ph); δC (100 MHz) 23.5 (q, Me), 23.8 (t,
C-5), 29.6 (t, C-1), 40.9 (t, C-2), 46.0 (s, C-7a), 61.6 (d, C-4),
120.0 (d, C-6), 128.9 (d, SO2Ph), 129.2 (d, SO2Ph), 133.3 (d,
C-3), 133.5 (d, SO2Ph), 137.7 (s, C-3a), 138.0 (d, C-7) and 138.3
(s, SO2Ph); m/z 274.1008 (Mϩ. C16H18O2S requires M,
274.1023).
Compounds 9 and 10. The phenylsulfinyl nonatetraene 4c (350
mg, 1.43 mmol) in dichloromethane (50 cm3) at 0 ЊC was treated
with MCPBA (370 mg, 67%, 1.43 mmol). After 30 min at 0 ЊC,
aq. NaHCO3 was added, and the mixture was extracted
(CH2Cl2). The organic phase was washed (brine), dried
(MgSO4) and evaporated under reduced pressure, and the
residue was dissolved in dichloromethane (20 cm3) and kept at
30 ЊC for 20 min. Evaporation of the solvent and flash chroma-
tography of the residue on silica gel [ethyl acetate–hexane
(1:50)] yielded a fraction comprising a mixture of cycloadducts
(~4:1 by NMR), which was rechromatographed on silica gel
with ethyl acetate–toluene (1:49) as eluent to give (4S*,7aR*)-
4-phenylsulfonyl-2,4,5,7a-tetrahydro-1H-indene 9 (63 mg, 18%),
mp 114–116 ЊC (from ethanol) (Found: C, 69.1; H, 6.2; S,
12.1%; Mϩ Ϫ SO2Ph, 119. C15H16O2S requires C, 69.2; H, 6.2;
S, 12.3%; M, 260); νmax/cmϪ1 1307 and 1146 (SO); δH (400 MHz,
C6D6) 1.36 (1H, dq, J 19.5 and 3 × 9.8, 1β-H), 1.80 (1H, br m,
Compound 13. The dodecatetraene 5e (57 mg, 0.1 mmol) in
CDCl3 (2 cm3) was heated in a sealed NMR tube at 50 ЊC for
2 h, whereupon NMR monitoring revealed that reaction was
complete. The solvent was evaporated, and the residue was
chromatographed on silica gel [ethyl acetate–toluene (1:49)]
to yield (4ЈR*,7aЈR*)-3-(4-phenylsulfonyl-2,4,5,7a-tetrahydro-
1H-inden-4-yl)propan-1-yl TBDPS ether 13 (43 mg, 75%), νmax
/
cmϪ1 1308 and 1141 (SO); δH (400 MHz) 0.95 (9H, s, But), 1.00
(3H, m, 1Јβ-H and 3-H2), 1.40 (2H, m, 2-H2), 1.98 (1H, ddd, J
9.9, 6.5 and 3.0, 1Јα-H), 2.25 (3H, m, 2Ј-H2 and 5Ј-H), 3.00 (1H,
₁
dt, 18.7 and 2 × 2.5, 5Ј-H), 3.25 (1H, br, W 14, 7aЈ-H), 3.60
₂

(2H, m, 1-H2), 5.40 (1H, br s, 3Ј-H), 5.63 (1H, ddd, J 9.9, 7.4
and 2.5, 6Ј-H), 5.70 (1H, br d, J 9.9, 7Ј-H) and 7.35–7.80 (15H,
m, Ph); δC (100 MHz) 19.2 (s, CMe3), 26.6, (t, C-3), 26.8 (q,
C–C(Me3)3), 28.6 (t, C-5Ј), 31.2 (t, C-1Ј), 31.7 (t, C-2Ј), 31.9 (t,
C-2), 43.4 (d, C-7aЈ), 63.6 (t, C-1), 67.5 (s, C-4Ј), 122.9 (d, C-6Ј),
127.6, 128.2, 129.6 (d, Ph), 131.8 (d, C-7Ј), 132.0 (d, Ph), 133.4
(d, C-3Ј), 133.7 (s, Ph), 134.8 (d, Ph), 135.2 (s, C-3aЈ) and 135.5,
137.6 (s, Ph); m/z (Electrospray) 579 (Mϩ ϩ Na).
₁
W 29.5, 1α-H), 2.15 (3H, m, 2-H2 and 5-H), 2.60 (1H, m, W
₂

₁
36.7, 5α-H), 2.80 (1H, m, W 17.5, 7a-H), 3.78 (1H, m, W 21.7,
₂

4-H), 5.18 (1H, ddt, J 9.8, 5.0 and 2 × 2.4, 6-H), 5.41 (1H, br d,
J 9.8, 7-H), 6.42 (1H, t, J 2.3, 3-H) and 7.00–7.78 (5H, m,
SO2Ph); δH (400 MHz, CDCl3) 1.40 (1H, dq, J 19.5 and 3 × 9.8,
1β-H), 2.20–2.45 (5H, m, 1α-H, 2-H2 and 5-H2), 3.20 (1H, m,
₁
W 17.5, 7a-H), 4.00 (1H, m, W 21.7, 4-H), 5.45 (1H, ddt, J 9.8,
₂

5.0 and 2 × 2.4, 6-H), 5.41 (1H, br d, J 9.8, 7-H), 6.42 (1H, t, J
2.3, 3-H) and 7.00–7.78 (5H, m, SO2Ph); δC (100 MHz, C6D6)
28.4 (C-5), 30.7 (C-1), 32.5 (C-2), 46.5 (C-7a), 61.8 (C-4), 122.6
(C-6), 126.3 (SO2Ph), 127.9 (SO2Ph), 128.1 (C-7), 132.2 (C-3),
5-(2-Furyl)pent-1-yn-3-ol 15
Dess–Martin oxidation of 3-(2-furyl)propan-1-ol 1420 followed
J. Chem. Soc., Perkin Trans. 1, 2000, 3129–3139
3137

View Article Online
by ethynylation, as described in previous experiments, gave the
remaining solvent was evaporated under reduced pressure, the
pentynol 15 (85% over two steps) as a colourless oil, νmax/cmϪ1
residue was taken up with dichloromethane, and the organic
phase was washed (water), dried (MgSO4) and evaporated
under reduced pressure to yield an oily residue (783 mg, 93%), a
portion (700 mg, 4.06 mmol) of which was dissolved in THF
(20 cm3) and treated at 0 ЊC with ethylene glycol (0.66 cm3, 10
mmol) and BF3ؒOEt2 (0.2 cm3, 1.6 mmol) for 1 h. The mixture
was poured into aq. NaHCO3–ice, and the product was
extracted (CH2Cl2). The combined extract was washed (water,
brine), dried (MgSO4) and evaporated under reduced pressure,
and the residue was chromatographed on silica gel [ethyl
acetate–hexane (2:3)] to yield 3-(4,4-ethylenedioxycyclohex-1-
en-1-yl)propan-1-ol 21 (489 mg, 61%), νmax/cmϪ1 3621 (OH);
δH (400 MHz) 1.70 (2H, m, 2-H2), 1.74 (2H, t, J 6.7, 6Ј-H2),
2.07 (2H, t, J 7.2, 3-H2), 2.18 (2H, m, 5Ј-H2), 2.24 (2H, br s,
3Ј-H2), 3.62 (2H, t, J 6.4, 1-H2), 3.95 (4H, s, O-(CH2)2O)
and 5.35 (1H, br s, 2Ј-H); δC (100 MHz) 27.5 (t, C-5Ј), 30.6
(t, C-2), 31.1 (t, C-6Ј), 33.6 (t, C-3), 35.6 (t, C-3Ј), 62.8
(t, C-1), 64.4 (t, O(CH2)2O), 108.1 (s, C-4Ј), 118.5 (d, C-2Ј)
and 137.1 (s, C-1Ј); m/z 198.1250 (Mϩ. C11H18O3 requires
M, 198.1250).
᎐
3687 (OH) and 3305 (C᎐C); δH (400 MHz) 2.05 (2H, m, 4-H2),
᎐
2.48 (1H, d, J 2.1, 1-H), 2.80 (2H, t, J 7.6, 5-H2), 4.40 (H, br m,
3-H), 6.00 (1H, dd, 3.1 and 0.9, 5Ј-H), 6.28 (1H, dd, J 3.1 and
1.8, 4Ј-H) and 7.31 (1H, dd, J 1.8 and 0.9, 3Ј-H); δC (100 MHz)
23.5 (C-5), 35.8 (C-4), 61.4 (C-3), 73.3 (C-1), 84.3 (C-2), 105.3
(C-3Ј), 110.0 (C-4Ј), 141.0 (C-5Ј) and 154.7 (C-2Ј); m/z 150.0697
(Mϩ. C9H10O2 requires M, 150.0681).
5-(2-Furyl)-1-phenylsulfinylpenta-1,2-diene 16
Treatment of compound 15 (50 mg, 0.33 mmol) with triethyl-
amine (50 µl, 0.37 mmol) and benzenesulfenyl chloride (38 µl,
0.37 mmol) followed by work-up and chromatography on silica
gel [ethyl acetate–hexane (3:7)] gave the 1-phenylsulfinylallene
16 (42 mg, 49%) as a colourless oil, νmax/cmϪ1 1951 (C᎐C᎐C)
᎐ ᎐
₁
and 1036 (SO); δH (400 MHz) 2.45 (2H, m, W 10.8, 4-H2), 2.75
₂

(2H, t, J 7.5, 5-H2), 5.75 (1H, td, J 2 × 7.0 and 6.2, 3-H), 6.02
(1H, dq, 3.1 and 0.9, 5Ј-H), 6.05 (1H, dt, J 6.2 and 2 × 3.1,
1-H), 6.27 (1H, dd, J 3.1 and 1.8, 4Ј-H), 7.30 (1H, dd, J 1.8
and 0.9, 3Ј-H) and 7.52–7.62 (5H, m, SOPh); δC (100 MHz)
26.8 (C-4), 27.1 (C-5), 98.1 (C-1), 103.2 (C-3), 105.7 (C-3Ј),
110.2 (C-4Ј), 124.3 (SOPh), 129.2 (SOPh), 131.0 (SOPh), 141.2
(C-2Ј), 144.8 (SOPh), 154.2 (C-5Ј) and 203.6 (C-2); m/z 258
(Mϩ).
5-(4,4-Ethylenedioxycyclohex-1-en-1-yl)pent-1-yn-3-ol 22
Sequential Dess–Martin oxidation–ethynylation of 21, as
described in previous experiments, gave pentynol 22 (54% over
two steps), νmax/cmϪ1 3691 (OH) and 3305 (C᎐C); δ (400 MHz)
᎐
᎐
H
2.44 (1H, d, J 2.1, 1H), 3.95 (4H, s, O-(CH2)2O), 4.45 (1H, td,
J 2 × 6.4 and 2.1, 3-H) and 5.35 (1H, br, W 10.2, 2Ј-H); δC
(100 MHz) 27.5 (C-5Ј), 31.1 (C-6Ј), 32.4 (C-5), 35.4 (C-4), 35.6
(C-3Ј), 62.0 (C-3), 64.4 [O(CH2)2O], 73.0 (C-1), 84.7 (C-2),
108.1 (C-4Ј), 119.0 (C-2Ј) and 136.4 (C-1Ј); m/z 222.1257
(Mϩ. C13H18O3 requires M, 222.1256).
Oxidation–IMDA cyclisation of the furyl compound 16
The phenylsulfinylallene 16 (230 mg, 0.89 mmol) was treated
with MCPBA (230 mg, 67%, 0.89 mmol) in dichloromethane
(30 cm3) at Ϫ10 ЊC for 30 min. The reaction was quenched with
aq. NaHCO3–ice, and the mixture was extracted (CH2Cl2). The
organic phase was washed (brine), dried (MgSO4) and evapor-
ated under reduced pressure, maintaining the temperature
5-(4,4-Ethylenedioxycyclohex-1-en-1-yl)-1-phenylsulfonylpenta-
1,2-diene 23
1
~0 ЊC throughout the work-up. A H NMR spectrum of the
reaction mixture showed the presence of three species in the
ratio ~10:2:1. The major component 19 was isolated (see
below), whereas the minor components were characterised by
the following spectroscopic data of the mixture, δH (400 MHz)
17: 2.45 (2H, m, 4-H2), 2.70 (2H, t, J 7.5, 5-H2), 5.87 (1H, td,
J 2 × 7.0 and 6.2, 3-H), 6.00 (1H, dq, 3.1 and 0.9, 5Ј-H), 6.20
(1H, dt, J 6.2 and 2 × 3.1, 1-H), 6.27 (1H, dd, J 3.1 and 1.8,
4Ј-H), 7.30 (1H, dd, J 1.8 and 0.9, 3Ј-H) and 7.50–7.90 (5H, m,
SO2Ph); 18: 4.42 (1H, d, J 3.6, 4-H), 5.30 (1H, dd, J 3.6 and 1.7,
5-H), 5.45 (1H, m, 3-H), 6.54 (1H, d, J 5.6, 7-H) and 6.57 (1H,
dd, J 5.6 and 1.7, 6-H).
Flash chromatography of the mixture on silica gel [ether–
hexane (3:2)] furnished (4S*,5R*,7aS*)-4-phenylsulfonyl-5,7a-
epoxy-2,4,5,7a-tetrahydro-1H-indene 19 (150 mg, 63%), mp 87–
90 ЊC (from dichloromethane–ether) (Found: C, 66.1; H, 5.1; S,
11.4%; Mϩ, 274. C15H14O3S requires C, 65.7; H, 5.1; S, 11.7%;
M, 274); νmax/cmϪ1 1307 and 1141 (SO); δH (400 MHz) 1.85 (1H,
ddd, J 13.9, 9.6 and 8.2, 1β-H), 2.28 (1H, ddd, J 13.9, 7.4, and
1.6, 1α-H), 2.70–2.90 (2H, m, 2-H2), 3.65 (1H, dt, J 3.4 and
2 × 1.9, 4-H), 5.38 (1H, d, J 2.1, 5-H), 5.75 (1H, dt, J 3.3
and 2 × 1.9, 3-H), 6.41 (1H, dd, J 5.7 and 2.1, 6-H), 6.50 (1H, d,
J 5.7, 7-H) and 7.55–7.87 (5H, m, SO2Ph); δC (100 MHz) 26.3
(t, C-1), 37.1 (t, C-2), 66.7 (d, C-4), 83.8 (d, C-5), 101.1 (s,
C-7a), 124.4 (d, C-3), 128.7 (d, SO2Ph), 129.5 (d, SO2Ph), 133.8
(d, SO2Ph), 135.0 (d, C-6), 137.8 (s, C-3a) and 137.8 (SO2Ph)
and 140.3 (d, C-7).
Treatment of compound 22 (900 mg, 4.05 mmol) with triethyl-
amine (0.85 cm3, 6.08 mmol) and benzenesulfenyl chloride (0.58
cm3, 5 mmol) in dichloromethane (40 cm3) at Ϫ78 ЊC, followed
by oxidation of the resulting crude phenylsulfinylallene (1.07 g,
3.24 mmol) with MCPBA (912 mg, 3.24 mmol) in dichloro-
methane (40 cm3) at 0 ЊC, as described in previous experiments,
gave the phenylsulfonylallene 23 (461 mg, 41%), νmax/cmϪ1 1956
(C᎐C᎐C), 1308 and 1148 (SO); δ (400 MHz) 1.73 (2H, t, J 6.6,
᎐ ᎐
H
5Ј-H2), 2.03 (2H, br t, J 7.5, 5-H2), 3.94 (4H, s, O-(CH2)2O),
5.26 (1H, br s, W 8.2 Hz, 2Ј-H), 5.85 (1H, td, J 2 × 7.0 and 6.0,
3-H), 6.18 (1H, dt, J 6.0 and 2 × 3.0, 1-H) and 7.40–7.90 (5H,
m, SO2Ph); δC (100 MHz) 25.8 (t, C-6Ј), 27.5 (t, C-4), 31.0
(t, C-5), 35.5, 35.6 (t, C-3Ј and C-5Ј), 64.4 (t, O(CH2)2O), 100.6
(d, C-1), 101.3 (d, C-3), 107.9 (s, C-4Ј), 119.4 (d, C-2Ј), 127.6
(d, SO2Ph), 129.1 (d, SO2Ph), 133.4 (d, SO2Ph), 135.6 (s, C-1Ј),
141.4 (s, SO2Ph) and 205.5 (s, C-2); m/z 346.1234 (Mϩ.
C19H22O4S requires M, 346.1234).
4-(5-Phenylsulfonylpenta-3,4-dienyl)cyclohex-3-en-1-one 24
The ketal 23 (200 mg, 0.58 mmol) in trifluoroacetic acid (1.5
cm3) was stirred at room temperature for 30 min, then the
solution was cooled to 0 ЊC and neutralised with aq. NaHCO3.
The mixture was extracted (Et2O), and the extract was washed
(water, brine), dried (MgSO4) and evaporated under reduced
pressure. The residue was chromatographed on silica gel [ethyl
acetate–hexane (2:3)] to yield the ketone 24 (161 mg, 92%),
3-(4,4-Ethylenedioxycyclohex-1-en-1-yl)propan-1-ol 21
νmax/cmϪ1 1956 (C᎐C᎐C), 1713 (CO), 1308 and 1149 (SO);
᎐ ᎐
3-(4-Anisyl)propan-1-ol 2023 (830 mg, 5 mmol) in THF (10
mmol) was added to stirred liquid ammonia (30 cm3) and
ethanol (20 cm3), followed by sodium (1 g, 43 mmol, in small
portions). The solution was stirred for 30 min, then NH4Cl (s)
was added and the ammonia was allowed to evaporate. The
δH (400 MHz) 2.20 (2H, t, J 2 × 7.4, 1Ј-H2), 2.30 (2H, m, W 25,
2H2), 2.35 (2H, td, J 2 × 6.8 and 1.2, 5-H2), 2.50 (2H, td,
J 2 × 6.8 and 0.8, 6-H2), 2.82 (2H, m, 2Ј-H2), 5.46 (1H, m,
3-H), 5.85 (1H, td, J 2 × 6.8 and 5.9, 3Ј-H), 6.20 (1H, dt, J 5.9
and 2 × 2.9, 5Ј-H) and 7.56–7.62 (5H, m, SO2Ph); δC (100
3138
J. Chem. Soc., Perkin Trans. 1, 2000, 3129–3139

View Article Online
MHz) 25.7 (t, C-5), 27.8 (t, C-2Ј), 35.5 (t, C-1Ј), 38.4 (t, C-6),
39.5 (t, C-2), 100.4 (d, C-3Ј), 101.5 (d, C-5Ј), 119.3 (d, C-3),
127.6 (d, SO2Ph), 129.2 (d, SO2Ph), 133.4 (SO2Ph), 136.7
(d, SO2Ph), 141.3 (s, SO2Ph), 155.4 (s, C-4) and 205.6 (s, C-4Ј),
210.4 (s, C-1); m/z 302.0981 (Mϩ. C17H18O3S requires M,
302.0977).
Acknowledgements
We thank the National Research Foundation and AECI Ltd
for financial support.
References
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2 J. R. Bull, N. S. Desmond-Smith, S. J. Heggie, R. Hunter and
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3 N. S. Simpkins, Sulfones in Organic Synthesis, Pergamon, Oxford,
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9 S. Braverman and H. Mechoulam, Tetrahedron, 1974, 30, 3883;
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10 W. D. Wulff and T. S. Powers, J. Org. Chem., 1993, 58, 2381.
11 W. R. Roush and S. E. Hall, J. Am. Chem. Soc., 1981, 103, 5200.
12 P. B. Hopkins and P. L. Fuchs, J. Org. Chem., 1978, 43, 1208.
13 C. Margot, M. Rizzolio and M. Schlosser, Tetrahedron, 1990, 46,
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14 W. R. Roush, H. R. Gillis and A. J. Ako, J. Am. Chem. Soc., 1982,
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15, 333 and references cited therein.
1-(Phenylsulfonylmethyl)spiro[4.5]deca-1,6-dien-8-one 26
From compound 24. The ketone 24 (200 mg, 0.66 mmol)
was added to a solution of lithium diisopropylamide [from n-
BuLi (0.28 cm3, 0.7 mmol, 2.5 M solution in THF) and diiso-
propylamine (92 µl, 0.7 mmol)] in THF (5 cm3) at Ϫ78 ЊC
and the mixture was stirred for 15 min, then trimethylchloro-
silane (0.11 cm3, 0.55 mmol) was added. After a further 30 min
at Ϫ78 ЊC, the mixture was warmed to room temperature,
then stirred for 2 h. Pentane was added, the solution was
washed (NaHCO3), and the solvent was evaporated under
reduced pressure. Flash chromatography of the residue on
silica gel [ethyl acetate–hexane (3:7)] gave a fraction (23 mg,
12%) comprising a mixture of isomers 25 (~5:1 by NMR),
δH (400 MHz) major component: 4.05 (1H, br s, 4-H), 4.45
(1H, br s, OH), 4.90 (1H, q, J 3 × 2.2, 3-H), 6.10 (1H, d, J 8.6,
7-H), 6.12 (1H, d, J 8.6, 6-H), 7.60–7.95 (5H, m, SO2Ph);
minor component: 4.15 (1H, br s, 4-H), 4.95 (1H, br s, OH),
5.60 (1H, d, J 8.6, 7-H), 5.65 (1H, q, J 3 × 2.0, 3-H), 6.12
(1H, d, J 8.6, 6-H), 7.45–7.70 (5H, m, SO2Ph). A portion
(10 mg, 0.33 µmol) of this fraction in THF–EtOH (1 cm3, 1:1)
was treated with aq. 1 M KOH (1 cm3, 1 mmol) at room
temperature for 30 min, water was added, and extraction (Et2O)
of the mixture furnished the spiro compound 26 (7 mg, 70%) as
a colourless oil, νmax/cmϪ1 1674 (CO), 1309 and 1152 (SO);
δH (400 MHz) 1.70–1.90 (3H, 4-H and 10-H2), 2.85 (4H, m,
3-H2 and 9-H2), 3.68 (1H, dd, J 14.4 and 1.2, CH2S), 3.77 (1H,
dd, J 14.4 and 1.6, CH2S), 5.91 (1H, dd, J 10.0 and 0.8, 7-H),
6.19 (1H, m, 2-H), 6.50 (1H, dd, J 10.0 and 1.6, 6-H) and
7.56–7.90 (5H, m, SO2Ph); δC (100 MHz) 30.7, 30.9, 34.2
(t, C-3, C-4 and C-10), 35.1 (t, C-9), 52.5 (s, C-5), 54.6
(t, CSO2Ph), 128.5 (d, SO2Ph), 129.2 (d, SO2Ph), 129.3 (d, C-7),
133.9 (d, SO2Ph), 134.3 (s, SO2Ph), 136.5 (d, C-2), 139.3
(s, C-1), 154.9 (d, C-6) and 199.0 (s, C-8); m/z 302.0971
(Mϩ. C17H18O3S requires M, 302.0977).
16 J. K. Stille, Angew. Chem., Int. Ed. Engl., 1986, 25, 508.
17 P. D. Wender and M. J. Tebbe, Synthesis, 1991, 1089.
18 D. Craig, N. J. Geach, C. J. Pearson, A. M. Slawin, A. J. P. White and
D. J. Williams, Tetrahedron, 1995, 51, 6071.
19 C. O. Kappe, S. S. Murphree and A. Padwa, Tetrahedron, 1997, 53,
14179.
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Soc., 1988, 110, 1901.
21 H. Friebolin, Basic One- and Two-Dimensional NMR Spectroscopy,
2nd ed., VCH Publishers, Weinheim, 1993, ch. 3.
22 J. R. Bull, M. A. Sefton and R. I. Thomson, S. Afr. J. Chem., 1990,
43, 42.
From compound 23. The phenylsulfonylallene 23 (460 mg,
1.33 mmol) was stirred in trifluoroacetic acid (4 cm3) at room
temperature for 1 h, an excess of 1 M KOH was added, and the
solution was stirred for a further 1 h. Aq. NH4Cl was added and
the product was extracted (EtOAc). The extract was washed
(NH4Cl, brine), dried (MgSO4) and evaporated under reduced
pressure, and the residue was chromatographed on silica gel
[ethyl acetate–hexane (2:3)] to yield compound 26 (340 mg,
85%).
23 A. Goosen, C. F. Marais, C. W. McCleland and F. Rinaldi, J. Chem.
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J. Chem. Soc., Perkin Trans. 1, 2000, 3129–3139
3139