The photomediated reaction of alkynes with cycloalkanes

Article abstract of DOI:10.1039/b517631j

In the presence of a photomediator such as benzophenone, alkynes with electron-withdrawing groups react with cycloalkanes to give vinyl cycloalkanes. The reaction involves the regiospecific addition of a photochemically generated cycloalkyl radical to the β-carbon of the alkyne. The stereochemical outcome of the reaction depends on the nature of the photomediator and alkyne used. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b517631j

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
The photomediated reaction of alkynes with cycloalkanes†
Ro´ıs´ın A. Doohan, John J. Hannan and Niall W. A. Geraghty*
Received 13th December 2005, Accepted 20th January 2006
First published as an Advance Article on the web 6th February 2006
DOI: 10.1039/b517631j
In the presence of a photomediator such as benzophenone, alkynes with electron-withdrawing groups
react with cycloalkanes to give vinyl cycloalkanes. The reaction involves the regiospecific addition of a
photochemically generated cycloalkyl radical to the b-carbon of the alkyne. The stereochemical
outcome of the reaction depends on the nature of the photomediator and alkyne used.
a variety of photochemical methods,15 all of which involve the
Introduction
generation of a cyclopentyl radical by homolysis of a C–H bond.
Indeed, in the context of the discussion above, it was found
that the reactions of triflones13 and 2-chloroethylsulfonyl oxime
ethers14 were amenable to photoinitiation as well as initiation
using an AIBN-related compound. In experimental terms the
photoinduced hydrogen abstraction reactions of ketones are
particularly attractive as a method of producing alkyl radicals,
the process relying on the alkoxy radical character of carbonyl
groups in the (n → p*) triplet state.16 Thus, following absorption of
a photon and intersystem crossing, ketones such as benzophenone
are able to abstract a hydrogen atom from a substrate containing
an appropriate C–H bond. The resulting alkyl radicals can react
in a variety of ways including recombination, disproportionation
and further hydrogen abstraction. Most usefully and because
of their nucleophilic properties,17 they would be expected to
react with molecules containing electron deficient carbon–carbon
multiple bonds (Scheme 1). This approach has been used in
the reaction of enones with 1,3-dioxolanes,18 the reaction of
enals with dioxolanes and alcohols,19 and the functionalisation
of cycloalkanes with alkenyl nitriles20 and ketene dithioacetal S,S-
dioxides.21 The mechanistic framework for the process suggests
that the use of “catalytic” quantities of the carbonyl compound
functioning as the photomediator should be sufficient. However,
in practice there are many ways in which this molecule can be
diverted from performing the required role and so larger amounts
are in general required.
The introduction of a functional group at an unactivated carbon
atom, such as those of an alkane or an ether, or the involvement of
such an atom in carbon–carbon bond formation, are synthetic
problems of obvious importance and considerable difficulty.1
These problems have been addressed in a variety of ways,
many of which involve the generation of an alkyl radical from
an appropriate precursor and its subsequent reaction with the
precursor of the group that is to be introduced. This indirect
generation of the alkyl radical can be achieved in a wide variety
of ways, including the reaction of alkyl halides with tributyltin
hydride2 or tris(trimethyl)silane,3 the photolysis of nitrites4 or
alkylcobalt compounds,5 the thermal decomposition of thiohy-
droxamic esters,6 metal catalysis,7 etc. Most of these methods are
however limited by the fact that they involve toxic reagents or
require the synthesis of the appropriate radical precursor. The
direct generation of alkyl radicals by the homolytic cleavage
of a C–H bond has been used less frequently and generally
involves peroxides or photomediation.8 Once generated, these
radicals can participate in carbon–carbon bond forming reactions,
producing a variety of functionalised systems. Vinyl and allyl
groups can, for example, be introduced in this way by an addition–
elimination sequence involving the radical and the appropriate
stannane,9,10 sulfide or related derivatives.11,12 A chain transfer
reaction involving triflones13 has been used to carry out the
alkenylation, alknylation and allylation of alkane- and ether-
derived radicals. The reaction of these and related radicals with
2-chloroethylsulfonyl oxime ethers14 results in the introduction
of an oxime ether group, hydrolysis of which gives acylated
derivatives. Once again, an evaluation of a particular process has
to include a consideration of the nature of the reagents required,
the by-products produced – for example, the use of triflones13 and
chloroethylsulfonyl oxime ethers14 results in the formation of SO2 –
and the problems associated with the synthesis of any reactant.
Although often beset with problems of control and efficiency,
the potential of photochemically initiated processes for the
production of radicals is well established. In terms of unactivated
systems, cyclopentane for example has been functionalised using
Department of Chemistry, National University of Ireland, Galway, Ireland.
E-mail: niall.geraghty@nuigalway.ie; Fax: +00 353 91 525700; Tel: +00
353 91 524411
† Photomediated functionalisation and carbon–carbon bond formation in
unactivated molecules. Part 1.
Scheme 1
942 | Org. Biomol. Chem., 2006, 4, 942–952
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
Table 1 The benzophenone-mediated reaction of alkynes with
This paper describes the photochemical reaction of alkynes
with cycloalkanes such as cyclopentane (Scheme 2). Reactions of
this type were first reported in 1969 by Buchi, and independently
by Grovenstein, who noted that the irradiation of a cyclohexane
solution of ethyl propiolate22 or dimethyl acetylenedicarboxylate23
gave very small amounts of products resulting from alkyne
insertion into a C–H bond of the cycloalkane. In view of the
reaction times and yields involved – 24 h and 5%, and 14 days
and 10%, respectively – it is not surprising that the system has
not been revisited for over 30 years. The analogous reaction
of saturated ethers with DMAD has also been noted,24,25 with
yields of up to 80% being reported for THF. Although the
acetone initiation of the addition of DMAD to cyclic ethers was
reported,24 all of the other reactions of ethers and cycloalkanes
involved direct irradiation. The possible involvement of an anion–
cation radical pair as an intermediate in the reactions25 of ethers
under such conditions was also considered, but a radical chain
mechanism initiated by unidentified agents was in general the
preferred mechanistic framework.
cyclopentane
Alkyne 1 Timea/h Products (yield, %)
E/Zb
1a
1b
1d
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
1p
1q
1r–x
1y
1z
2.75
2.5
3.2
3.3
4.5
6.5
4.5
7.5
2.0
4.5
3.0
1.3
1.5
2a (37)
2b (40)
2d (42)
2f (30)c
2g (34)c
2h (40)
2i (35)
2j (34)
2ke
3a (22)
3b (30)
3d (27)
3f (20)
3g (15)
3h (25)
3i (17)
3j (29)
3k (27)
3l (22)
1.5 : 1
1.5 : 1
1.5 : 1
1.5 : 1d
1.6 : 1
1.4 : 1
1.5 : 1
1.4 : 1
1.7 : 1
1.8 : 1
2l (25)
Mixture of 2m, 3m, 2o and 3o (46 : 35 : 17 : 1)e
2ne
3n (16)
1 : 1.5
1.8 : 1
6.4 : 1
3.9 : 1
2o (24)
3oe
3.0
Mixture of 2p and 3p (56%)e
11.5
No reaction
2.5
2q (18)
3qe
2y (50)
2z (43)
2aa (46)
3ye
1 : 45
1 : 42
3.0
1.5
3ze
1aa
1bb
3aa (3)
1 : 30
3.15 (22f) 2bb (21f)
3bb (7f)
1 : 12 (1 : 4f)
a Complete reaction of alkyne (GC). b GC. c Product contains some
benzophenone. d 1H NMR. e Product could not be satisfactorily isolated.
f Results obtained using acetophenone as photomediator. Products co-
eluted from SiO2 with benzophenone.
as a mixture of E and Z isomers (Table 1). The reaction of
methyl propiolate 1a in the presence of benzophenone is typical
of those involving monosubstituted alkynes. This gave a 1.6 : 1
(GC) mixture of methyl (E)- and (Z)-3-cyclopentyl-2-propenoate,
2a and 3a, which following chromatography were obtained in
isolated yields of 32 and 36%, respectively (Table 1). The reaction
is regiospecific, with the structures of the products being consistent
with the concept that the reaction involves the conjugate addition
of a nucleophilic cycloalkyl radical to the electron-deficient alkyne.
The effectiveness of a range of potential photomediators in
promoting the reaction was investigated and it was found that
the reaction time and yield, and the product composition, were
relatively insensitive to the structure of the photomediator used
(Table 2). Exceptions to this pattern were 2-acetylnaphthalene,
the lowest triplet state of which is of the p,p* type, and 4-
methoxyacetophenone, the behaviour of which can again be
explained on the basis that most molecules on excitation end up
in the p,p* state.
Scheme 2
We have found that the use of a photomediator such as
benzophenone has a significant impact on the reaction of alkynes
with cycloalkanes in terms of yield and reaction time, and here
we report results relating to cycloalkanes of various sizes and to
alkynes carrying a wide variety of functional groups. The results
are important in that they relate to functionalisation and carbon–
carbon bond formation in an unactivated system, and also because
they suggest that photoinduced hydrogen abstraction in certain
circumstances may be a synthetically useful method of generating
radicals.20,21
A series of experiments involving benzophenone showed that
the photomediator concentration could be reduced by a factor
of six without affecting the reaction time or the yield (Table 3).
At lower concentrations the time taken to complete the reaction
increased dramatically. The only other low MW products formed
in these reactions were cyclopentenone and cyclopentanol (GC–
MS), the result of reaction between the cyclopentyl radicals and
O2 that had survived the degassing which preceded irradiation.
There is a strong correlation between reaction time and the
Results and discussion
Initial experiments were carried out with cyclopentane and
involved irradiating a solution of the alkyne 1 (0.15 M) and
photomediator (1 equiv.) in the cycloalkanes, through Pyrex
glass and using 350 nm lamps, until no alkyne remained (GC)
(Scheme 2). Evaporation of the cyclopentane and removal of
the photomediator by chromatography gave a substituted alkene
This journal is
The Royal Society of Chemistry 2006
Org. Biomol. Chem., 2006, 4, 942–952 | 943
©

View Article Online
Table 2 A comparison of the reaction of methyl propiolate 1a with cyclopentane using different photomediatorsa
d
Timeb/h
Yieldc (%)
Z/E
ROH/R2C O (%)
=
Photomediator
Ph2CO
PhCOMe
2.75
5.00
86
86
1 : 1.46
1 : 1.26
1.5/1
0.7/1
(2-Naphthyl)COMe
4-MeOC6H4COMe
4-F3CC6H4COMe
PhCHO
4-MeOC6H4COPh
(3-F3CC6H4)2CO
(4-MeOC6H4)2CO
No reaction
106 (86e)
1.75
1.25
3.50
2.00
5.00
70
97
84
92
96
88
1 : 1.44
1 : 1.30
1 : 1.32
1 : 1.33
1 : 1.34
1 : 1.27
5/4
1.3/0.6
0.4/0.2
4/2
2/1
3/1
a Cyclopentane solution of the alkyne (0.15 M) containing photomediator (1 equiv.), 350 nm. b Complete consumption (GC) of alkyne. c GC, decane as
IS. d ROH: cyclopentanol, R2C O: cyclopentanone. e Duplicate experiment: 79% of the alkyne had reacted after 86 h.
=
Table 3 The effect of benzophenone concentration on the reaction of methyl propiolate 1 with cyclopentanea
d
Time/hb
Yield (%)c
Z/E
ROH/R2C O (%)
=
[Benzophenone]/M
0.15
0.10
0.05
0.022
0.014
2.75
3.00
3.00
3.00
102e
86
93
92
95
91
1 : 1.46
1 : 1.30
1 : 1.33
1 : 1.32
1 : 1.27
1.5/1
2/1
3/1
3/2
5/4
a Cyclopentane solution of the alkyne (0.15 M) and photomediator, 350 nm. b Complete consumption (GC) of alkyne. c GC, decane as IS. d ROH:
cyclopentanol, R2C O: cyclopentanone. e 95% conversion of the alkyne had occurred after 5 h.
=
amount of these materials present in the product mixture (Tables 2
and 3). Interestingly, the normally efficient photoreduction of
benzophenone forming benzpinacol is not competitive with the
alkyne/cycloalkane reaction and the diol is formed in only very
small quantities, if at all. The stereochemistry of the products was
selectivity is displayed by alkynes containing other electron-
withdrawing groups such as a nitrile (1n), an acid (1o), or a sulfone
(1p). However, the crude product obtained from the reaction of
cyclopentane with 3-butyn-2-one 1q is more complex (GC) and the
one product successfully isolated, the E isomer 2q, was obtained
in only 18% yield. The failure of 1r and 1s to react underlines the
fact an electron-withdrawing group (EWG) on the alkyne is an
essential pre-requisite for reaction with cycloalkyl radicals. In the
same way, the failure of 1t to react presumably reflects the fact
that the influence of the nitro group is excessively attenuated by
the linking aromatic ring. The result helps to identify the level
of elecron-withdrawal that is required for these alkyne–cycloalkyl
radical reactions. Although the lack of an EWG may obviously be
responsible for the inertness of 1u and 1v, steric factors may also
play a role in these reactions, as the disubstituted alkynes 1w and
1x also fail to react despite the presence in both of an EWG.
Cyclopentane reacts with acetylenedicarboxylates 1y–bb
(Scheme 2) (Table 1) in a parallel but somewhat less efficient
manner, forming dialkyl 2-cyclopentyl-2-butenedioates. The stere-
ochemistry of the adducts was assigned on the basis that the
olefinic and cycloalkyl methine hydrogens of the E isomers 3y–
1
assigned on the basis of the H NMR coupling constants, 15.6
and 11.5 Hz, displayed by the a-H in 2a and 3a, respectively. In
common with all the reactions involving monosubstituted alkynes,
the secondary cis–trans photoisomerisation that is a feature of the
reactions of acetylenedicarboxylates (see below) does not occur
here. In this context it is worth noting that the rate of inversion of
vinyl radicals is much faster than the final hydrogen abstraction
step,26 and so the geometry of the product is not determined by
the stereochemistry of the addition of the cycloalkyl radical to the
alkyne (Scheme 1).
A GC analysis of the crude product indicated that the alkenes
2 and 3 were the only alkyne-derived low molecular weight
products formed in the reaction. It is assumed that the mass
balance for the reaction in terms of the alkyne is completed by
the formation of polyacetylene oligomers which are not detected
by GC and which are lost during chromatography. Compounds
of this type have been identified among the products formed in
reactions of propiolonitrile 1n and cycloalkanes that involved
higher concentrations of the alkyne and longer reaction times
than normal. Thus the dimeric species 4 was identified as a minor
product from the reaction of cyclopentane with 1n using GC–MS
on the basis of its molecular ion and fragmentation pattern. The
compounds 5 and 6 were isolated from the corresponding reaction
of cyclohexane with 1n and characterised spectroscopically.
The cyclopentyl radicals display chemoselectively to the extent
that they react exclusively with the alkyne in propiolate esters
containing benzyl (1f), ether (1g), alkenyl (1i and 1j), haloalkyl
(1k and 1l) and trimethylsilyl (1m) groups (Table 1). The same
1
bb, which are cis to ester groups, appear at lower field in the H
NMR spectrum relative to those of the Z isomers 2y–bb. The
reactions of acetylenedicarboxylates with cycloalkanes are highly
stereoselective, with the Z isomers predominating as a result of a
secondary photosensitised isomerisation of the initially formed
alkenes. As would be expected, the product ratio in this case
is photomediator dependent. Thus, whereas the benzophenone-
promoted reaction of DMAD 1y with cyclohexane gave a Z/E
ratio of 19 : 1 for 7y/8y, the use of acetophenone, which has
a higher triplet energy, resulted in a 4 : 1 mixture of 7y and
8y, as in this case both isomers are photoactive in terms of the
photosensitised isomerisation process; a 2.5 : 1 ratio was obtained
944 | Org. Biomol. Chem., 2006, 4, 942–952
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
Table 4 The photomediated reaction of alkynes with cyclohexane, cycloheptane and cyclooctanea
Cycloalkane
Alkyne
Timeb/h
Products (isolated yield, %)
E/Zc
Cyclohexane
Cyclohexane
Cyclohexane
Cyclohexane
Cyclohexane
Cyclohexane
Cyclohexane
Cyclohexane
Cyclohexane
Cyclohexane
Cyclohexaneh
Cyclohexanej
Cycloheptane
Cycloheptane
Cycloheptane
Cycloheptane
Cycloheptane
Cycloheptane
Cyclooctane
Cyclooctane
Cyclooctane
Cyclooctane
Cyclooctane
1a
1b
1c
1e
1k
1l
4.5
4.5
8.5
5.5
2.0
4.0
2.0
2.5
5.5
13.5
20.0
6.5
2.5
2.6
2.7
1.5
3.0
No reaction
3.0
7a (19)
8a (15)
1.5 : 1
1.5 : 1
1.4 : 1
1.5 : 1
1.5 : 1
1.5 : 1
7b (26)
8b (17)
7c/8c (27)d
7e/8e (37)d
7k (26)e
7l (18)
8k (14)
8l (15)
8n (15)f
1n
1o
1p
1y
1y
1y
1a
1b
1d
1n
1p
1y
1a
1b
1n
1p
1y
7n (11)f
1 : 1.5
7o/8o (28)d
7p/8p (30)d
7y (31)
2.5 : 1
6.8 : 1
1 : 19g
7y (12)
8y (3)
1 : 4i
7y (17)c
8y (7)c
1 : 2.5g
9a (21)
10a (17)
10b (20)
10d (16)
10n (37)e
1.3 : 1
9b (20)
1.3 : 1
1.4 : 1
1 : 2
9d (20)
9n (26)e
9p/10p (17)d,k
5.4 : 1
11a (18)
11b (24)
11n (9)
12a (24)
12b (22)
12n (23)l
1.4 : 1
1.3 : 1
1 : 2.4
4.6 : 1
3.5
1.0
1.5
No reaction
9p/10p (47)d
a Photomediator: benzophenone. b Complete reaction of alkyne (GC). c GC. d Chromatography gave a mixture of stereoisomers. e Contains a trace of
benzophenone. f Separated on AgNO3/SiO2. g Small amounts of cyclohexanol and cyclohexanone were also formed. h Photomediator: acetophenone.
i Isolated product. j Photomediator: benzaldehyde. k Traces of benzpinacol were also formed. l Contains a trace of 11n.
reactivity observed for the reaction of the cycloalkanes with
DMAD 1y was somewhat different, for although cyclopentane
again gave significantly higher yields than cyclohexane, the larger
ring systems did not react at all (Table 4). The observation
that cyclopentane is more reactive than cyclohexane in reactions
involving their respective radicals has also been made in relation
to the bromination of these systems, where the former reacts
7–8 times faster.27 The difference in reactivity in this case was
attributed to the larger amount of eclipsing strain relief that occurs
when a cyclopentyl radical is formed, essentially an I-strain28
effect. Although this would account for the relative reactivity
of cyclohexane and cyclopentane, it does not provide a basis
for understanding the behaviour of the other cycloalkanes. A
rationale based on the steric accessibility of the hydrogen atoms in
the cycloalkanes has some merit. It is reasonable to suggest that
the hydrogen atoms in cyclopentane are less sterically hindered
because of its smaller bond angle. The larger bond angles in the
other cycloalkanes would lead to any particular hydrogen in these
systems being subject to greater steric hindrance by the hydrogens
Scheme 3
on adjacent carbons. This would result in reduced reactivity for
C6–C8 with the propiolates, and a complete lack of reactivity
with benzaldehyde (Scheme 3, Table 4). The significantly reduced
stereoselectivity observed with di-t-butyl acetylenedicarboxylate
1bb in the presence of benzophenone (Table 1) presumably reflects
a steric preference for the E isomer. The use of acetophenone in
this case again results in a further reduction of stereoselectivity.
The effect of cycloalkane ring size on the outcome of the
reaction was considered in a series of experiments involving C5–C8
cycloalkanes. Reaction occurred in all cases with monosubstituted
alkynes. Cyclopentane, giving overall isolated yields of up to 70%
(Scheme 2, Table 1), was significantly more reactive than the C6–
C8 cycloalkanes, which gave yields varying in a non-systematic
way between 17 and 47% (Scheme 3, Table 4). The pattern of
for C7 and C8 when DMAD with its greater steric demand is
involved.
Such an analysis would suggest that cyclobutane should be
even more reactive than cyclopentane. Although no information
relating to the reaction of of cyclobutane with alkynes is currently
available, a study25 of the reaction of cyclic ethers with alkynes has
shown that four- and five-membered cyclic ethers add to DMAD
under direct radiation, whereas six- and seven-membered systems
are unreactive. A different effect may however be involved here, as
it has been suggested29 that there is a correlation between reactivity
and the torsion angle defined by the a-hydrogens and the p-type
non-bonded orbital on oxygen.
This journal is
The Royal Society of Chemistry 2006
Org. Biomol. Chem., 2006, 4, 942–952 | 945
©

View Article Online
A useful extension of this photochemical functionalisation of
cycloalkanes lies in the fact that the vinylcycloalkanes which are
the primary photoproducts at >300 nm undergo a photochemical
double bond migration at 254 nm. It has already been shown30
that ethyl b-cyclopentyl- and b-cyclohexylpropenoates react to
give b,c-unsaturated esters. In view of the ready availability of the
appropriate propenoates from the cycloalkane–alkyne reactions
discussed above we have been able to show that the reaction can
be extended to other propenoates including b-cycloheptyl and b-
cyclooctyl systems (Scheme 4).
The results reported here demonstrate that the photomedi-
ated reaction of electron-deficient alkynes with cycloalkanes,
particularly cyclopentane, is a genuine alternative to the other
available methods for carbon–carbon bond formation with, or
functionalisation of, such unactivated systems. The fact that the
reactions can be carried out31 using sunlight as a source of UV
radiation, and with supported photomediators, further enhances
the approach from the clean/green chemistry perspective.
Experimental
All starting materials were distilled before use. The alkynes
used, with the exception of those whose preparation is described
below, were commercially available or were prepared by literature
methods. The photochemical reactions between the cycloalkanes
and the alkynes were carried out in cylindrical Pyrex tubes using a
Rayonet Photochemical Reactor, RPR-100, equipped with sixteen
350 nm mercury lamps. IR spectra were measured on a Perkin–
Elmer Spectrum 1 FT-IR. 1H NMR and 13C NMR were measured
on a Jeol JNM-LA400 spectrometer at probe temperatures using
CDCl3 as solvent and TMS as internal standard. GC analyses
were carried out on an RTX-5 (Restek) column. GC–MS analyses
were carried out on a Micromass GCT spectrometer coupled to
an Agilent 6890 capillary gas chromatograph equipped with an
HP5 column.
Scheme 4
Of particular interest in this regard is the observation that
the double bond in dimethyl (Z)-2-cyclopentyl-2-butendioate 2y
undergoes a double migration, via the corresponding E isomer 3y,
forming initially the cyclopentylidene derivative 18 and ultimately
the cyclopentene 19 (Scheme 5, Fig. 1).
2-Methoxyethyl propiolate 1g
1g was prepared using a Mitsonobu reaction.32 A solution of
2-methoxyethanol (1.62 g, 21.4 mmol) and triphenylphosphine
(5.05 g, 19.2 mmol) in dry ether (25 ml) was added to a solution of
propynoic acid (1.50 g, 21.4 mmol) and diethyl azodicarboxylate
(3.50 g, 20 mmol), also in dry ether (15 ml). During the addition
there was a slight temperature rise followed by the precipitation
of a white solid. The mixture was stirred for 24 h at rt after
which the solid was removed by filtration and the solvent by
evaporation. The resulting pale yellow liquid was distilled and
chromatographed on SiO2 (ether–petroleum ether) to give 1g as a
colourless liquid (1.20 g, 42%): mmax(film)/cm−1 3258, 2118, 1717;
1H NMR (400 MHz, CDCl3) d 2.97 (1H, s, C≡CH), 3.40 (3H, s,
OMe), 3.64 (2H, t, J = 6.0 Hz, CH2OMe), 4.28 (2H, t, J = 6.0 Hz,
C(O)OCH2); 13C NMR (100 MHz, CDCl3) d 153.0, 75.6, 74.6,
70.0, 65.3, 59.2. C6H12O3 requires: C, 56.24; H, 6.29%; found: C,
56.59; H, 6.47%.
Fig. 1 The photodeconjugation reaction of dimethyl (Z)-cyclopentyl-
2-butenedioate 2y in the presence of triethylamine.
Cyclopentylmethyl propiolate 1h
1h was prepared as described above for 1g in 55% yield:
mmax(film)/cm−1 3262, 2119, 1714, 1230; 1H NMR (400 MHz,
CDCl3) d 1.61 (2H, m), 1.47–1.60 (4H, m), 1.67–1.72 (2H, m),
2.18 (1H, m, OCH2CH), 2.82 (1H, s, C≡CH), 4.02 (2H, d, J =
7.0 Hz, OCH2); 13C NMR (100 MHz, CDCl3) d 152.9, 75.4, 74.4,
70.2, 38.2, 29.2, 25.1. C9H12O2 requires: C, 71.03; H, 7.95%; found:
C, 70.69; H, 7.58%.
Methyl 4-cyclopentyl-2-butynoate 1w
A solution of n-BuLi (2.5 M in hexanes, 9.0 ml, 2.5 mmol)
was added, under N2, to a cold (−20 ◦C) stirred solution of
diisopropylamine (0.10 g, 1.0 mmol) and propynoic acid (0.70 g,
Scheme 5
946 | Org. Biomol. Chem., 2006, 4, 942–952
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
=
=
10.0 mmol) in dry THF. After 10 min HMPA (15 ml) was
NCCH CH), 6.57(1H, d, Jvic = 10.7 Hz, CHCH C), 7.22
◦
=
added slowly and the solution was stirred for 15 min at −20 C
(1H, d, Jtrans = 16.1 Hz, NCCH CH), 3.76 (3H, s, OCH3);
◦
and at −10 C for a further 1.5 h. Cyclopentymethyl bromide33
m/z (EI) 186 (M+, 7%), 185(5), 105(25), 103(9), 82(48), 67(100).
HRMS (EI): calcd. for C12H14N2 186.1157, found: 186.1155. 6:
(1.71 g, 10.5 mmol) was then added and the mixture was stirred
at room temperature for 24 h. After this period methyl iodide
(5.7 g, 40 mmol) was added and stirring was continued at room
temperature for a further 24 h. The mixture was then poured
into ice-cold water, ether was added and the aqueous layer
extracted with further ether. The combined organic extracts were
washed with water and brine, and after drying (MgSO4) and
filtering the solvent was evaporated to give a brown oil (0.9 g).
Chromatography on silica (4% ether in petroleum ether) gave 1w
mmax(film)/cm−1 2222, 1622, 965; H NMR (400 MHz, CDCl3) d
1
=
0.88–1.38 (5H, m), 1.58–1.77 (5H, m), 2.65 (1H, m, CHCH C),
5.72 (1H, d, Jtrans = 16.1 Hz, NCCH CH), 6.53(1H, d, Jvic
=
=
=
=
10.2 Hz, CHCH C), 6.89 (1H, d, Jtrans = 16.1 Hz, NCCH CH);
m/z (EI) 186 (M+, 8%), 185(1), 105(27), 103(11), 82(50), 67(100).
HRMS (EI): calcd. for C12H14N2 186.1157, found: 186.1173.
The reaction of propionitrile with cyclopentane under these
conditions resulted in the formation of two major products,
2n and 3n, and traces of a third, GCMS analysis of which
suggested it was a 4-(cyclopentylmethylene)-2-pentenedinitrile 4:
m/z (EI) 172 (M+, 12%), 171(19), 144(10), 130(9), 105(78), 103(30),
68(100), 67(14). HRMS (EI): calcd. for C11H12N2 172.1000, found:
172.0986.
1
(0.36 g, 21%) as a clear oil: mmax(film)/cm−1 2236, 1716, 1255; H
NMR (400 MHz, CDCl3) d 1.20–1.30 (2H, m), 1.50–1.68 (4H,
m), 1.80 (2H, m), 2.08 (1H, m, CH), 2.31 (2H, d, J = 6.8 Hz,
C≡CCH2), 3.73 (3H, s, OCH3); 13C NMR (100 MHz, CDCl3) d
154.3, 89.4, 72.8, 52.5, 38.0, 32.0, 25.0, 24.3. C10H14O2 requires: C,
72.26; H, 8.49%; found: C, 72.38; H, 8.15%.
Photodeconjugation reactions
Methyl 5-cyclohexyl-2-pentynoate 1x
Irradiation of isobutyl (E)-3-cyclopentyl-2-propenoate 2d.
Et3N (1 drop) was added to a degassed solution of 2d (0.16 g,
0.08 mmol) in cyclopentane in a quartz tube and this was
then irradiated in a Rayonet reactor using 254 nm lamps. The
reaction was monitored by GC, which indicated the formation
of two products. One of these, which was identified (GC) as
isobutyl (Z)-3-cyclopentyl-2-propenoate 3d, disappeared as the
reaction proceeded. Irradiation was discontinued after 10 h
when all of the 2d had reacted. Elution of the crude product
from silica (20 g) with ether–petroleum ether gave isobutyl 3-
cyclopentylidenepropanoate 13 (0.1 g, 59%) as a colourless liquid:
mmax(film)/cm−1 1735; 1H NMR (400 MHz, CDCl3) d 0.93 (6H, d,
J = 6.6 Hz, Me2CH), 1.60–1.75 (4H, m), 1.93 (1H, m, Me2CH),
1x was prepared as described above for 1w in 39% yield:
1
mmax(film)/cm−1 2237, 1716, 1252; H NMR (400 MHz, CDCl3)
d 0.89–0.90 (2H, m), 1.10–1.30 (2H, m), 1.35 (1H, m, CH), 1.47
(2H, q, J = 7.3 Hz, C≡CCH2CH2), 1.63–1.71 (6H, m), 2.34 (2H, t,
J = 7.3 Hz, C≡CCH2), 3.76 (3H, s, OCH3); 13C NMR (100 MHz,
CDCl3) d 154.2, 90.1, 72.6, 52.5, 36.6, 34.8, 32.6, 26.4, 26.0, 16.0.
C12H18O2 requires: C, 74.19; H, 9.34%; found: C, 74.07; H, 9.34%.
General procedure for photochemical reactions using benzophenone
as photomediator
A solution of benzophenone (0.08 g, 0.43 mmol), and when
required dodecane (0.37 g, 2 mmol), in cycloalkane (40 ml) was
degassed with N2 for 20 min. The alkyne (3 mmol) was added
and the stirred solution was irradiated until all the alkyne had
been consumed (GC). The crude product mixture contained the
cis and trans alkene products, and also trace amounts of the
cycloalkanol and cycloalkanone (GC–MS) corresponding to the
cycloalkane used. Subsequent to the removal of excess solvent
the products (Tables 1 and 4) were isolated by chromatography on
silica (50 g) using 5% ether–petroleum ether as eluant. All products
were obtained as clear sweet-smelling oils and were characterised
in the ususal way on the basis of IR and analytical data (Table 5),
and 1H and 13C NMR spectroscopy (Tables 6 and 7).
=
2.20 (2H, t, J = 7.0 Hz, CH2CH2C ), 2.25 (2H, t, J = 7.0 Hz,
=
CH2CH2C ), 3.00 (2H, d, J = 7.1 Hz, CH2CO), 3.80 (2H, d,
J = 6.6 Hz, OCH2), 5.40 (1H, t, J = 7.1 Hz, CH C); 13C NMR
=
(100 MHz, CDCl3) d 167.8, 142.6, 106.6, 65.9, 30.5, 28.7, 24.1,
23.0, 21.5, 14.3. C12H20O2 requires: C, 73.43; H, 10.27%; found: C,
73.20; H, 9.96%.
Irradiation of 2-methylbutyl (Z)-3-cyclohexyl-2-propenoate 3e.
Irradiation of 3e as indicated above for 18.5 h resulted in
the formation of 2-methylbutyl 3-cyclohexylidenepropanoate 14
(53%), which was obtained as a colourless liquid: mmax(film)/cm−1
1
1738; H NMR (400 MHz, CDCl3) d 0.81 (3H, t, J = 7.6 Hz,
MeCH2), 0.85 (3H, d, J = 7.3 Hz, MeCH), 1.07–2.04 (13H, m),
2.98 (2H, d, J = 7.3 Hz, CH2CO), 3.79 and 3.88 (2H, dds, Jvic
=
Isolation of (2E,4E)-4-(cyclohexylmethylene)-2-pentenedinitrile
5 and (2E,4Z)-4-(cyclohexylmethylene)-2-pentenedinitrile 6.
6.5, Jgem = 10.6 Hz, OCH2), 5.18 (1H, t, J = 7.3 Hz, CH C); 13C
NMR (100 MHz, CDCl3) d 173.4, 142.9, 112.4, 69.1, 36.8, 34.0,
32.9, 28.8, 28.3, 27.4, 26.6, 25.9, 16.2, 11.1. C14H24O2 requires: C,
75.00; H, 10.71%; found: C, 74.73; H, 10.49%.
=
A
solution of benzophenone (0.08 g, 0.43 mmol) in cyclohexane
(20 ml) was degassed with N2 for 20 min. Propionitrile (0.43 g,
8.4 mmol) was added and the solution was irradiated for 31 h,
at which point product formation had ceased (GC). The crude
product contained the expected alkenes 7n and 8n (GC, 1 : 1.4) and
a small amount of benzpinacol (1H NMR). Chromatography on
silica (40 g, 0–20% ether in petroleum ether) initially gave fractions
containing mixtures of 7n, 8n and benzophenone. Further elution
gave 5 (0.01 g) and 6 (0.02 g). 5: mmax(film)/cm−1 2222, 1622, 965;
1H NMR (400 MHz, CDCl3) d 0.88–1.36 (5H, m), 1.58–1.78
Irradiation of benzyl (Z)-3-cyclopentyl-2-propenoate 3f. In the
same way the irradiation of 3f for 5.5 h resulted in the formation
of benzyl 3-cyclopentylidenepropanoate 15 (70%), which was
obtained as a colourless liquid: mmax(film)/cm−1 1734, 736, 696;
1H NMR (400 MHz, CDCl3) d 1.45–1.80 (4H, m), 2.20 (2H, t,
=
=
J = 7.0 Hz, CH2CH2C ), 2.25 (2H, t, J = 7.0 Hz, CH2CH2C ),
=
(5H, m), 2.56 (1H, m, CHCH C), 5.84 (1H, d, Jtrans = 16.1 Hz,
3.00 (2H, d, J = 7.1 Hz, CH2CO), 5.04 (2H, s, OCH2), 5.36 (1H,
This journal is The Royal Society of Chemistry 2006
Org. Biomol. Chem., 2006, 4, 942–952 | 947
©

View Article Online
Table 5 IR and analytical data
mmax/cm−1
Analytical data
Alkenoate
CO
C
Other bands
C (Found (%) [Requires (%)])
H (Found (%) [Requires (%)]) HRMS CI, M+ + H: Found (Calculated)
=
C
2a (C9H14O2)34
3a (C9H14O2)
1724
1721
1724
1720
1720
1720
1718
1717
1720
1720
1720
1718
1719
1716
1721
1720
1719
1721
—
1658
1642
1656
1643
1652
1642
1639
1651
1642
1652
1641
1650
1641
1653
1642
1640
1649
1640
—
983
816
—
816
—
820
818, 736, 696
—
820
—
820
984, 929
986, 929
—
—
818
982-
819
—
—
2222, 971
2218
3100, 986
3100, 826
1597, 1315, 1140,
976, 815d
—
—
—
—
—
—
—
69.82 [70.10]
—
8.85 [9.15]
—
2b (C10H16O2)35
3b (C10H16O2)
2d (C12H20O2)
3d (C12H20O2)
3f (C15H18O2)
2g (C11H18O3)
3g (C11H18O3)
2h (C14H22O2)
3h (C14H22O2)
2i (C11H16O2)
3i (C11H16O2)a
2j (C13H20O2)
3j (C13H20O2)
3k (C10H15ClO2)
2l (C10H15BrO2)
3l (C10H15BrO2)
2m (C11H20O2Si)c
3m (C11H20O2Si)c
2n (C8H11N)a
71.21 [71.39]
73.06 [73.43]
73.20 [73.43]
78.54 [78.23]
66.65 [66.64]
66.65 [66.64]
75.42 [75.63]
75.35 [75.63]
—
9.36 [9.59]
10.17 [10.27]
9.96 [10.27]
8.20 [7.88]
8.73 [9.15]
8.50 [9.15]
9.75 [9.97]
9.64 [9.97]
—
—
—
—
—
—
—
—
—
—
—
74.85 [74.96]
74.65 [74.96]
—
48.89 [48.58]
48.75 [48.58]
—
—
—
—
—
9.75 [9.68]
9.65 [9.68]
—
6.08 [6.07]
6.19 [6.07]
—
—
—
—
—
202.0752b (202.0761)
—
—
212.1222b (212.1233)
212.1243b (212.1233)
121.0888b (121.0891)
121.0898b (121.0891)
140.0836b (140.0837)
140.0838b (140.0837)
250.1031b (250.1028)
—
—
—
1687
1693
—
—
1631
1621
1644
1634
1624d
3n (C8H11N)
2o (C8H12O2)36
3o (C8H12O2)36
2p (C14H18O2S)a
—
—
—
—
3p (C14H18O2S)a
2q (C9H14O)35
2y (C11H16O4)
2z (C13H20O4)
2aa (C17H28O4)
3aa (C17H28O4)
2bb (C17H28O4)
3bb (C17H28O4)
7a (C10H16O2)38
8a (C10H16O2)39
7b (C11H18O2)22
8b (C11H18O2)22
7c (C12H20O2)a,34
8e (C14H24O2)
—
—
—
—
—
250.1021b (250.1028)
—
—
—
—
—
—
—
1673
1722
1728
1727
1721
1721
1718
1724
1724
1724
1724
1719
1722
1623
1642
1646
1642
1638
1643
1630
1651
1644
1652
1644
1650
1638
1650
1637
1650
1638
1629
1624
1639d
—
—
—
—
—
838
842
983
820
983
820
—
816
892
818
982
62.44 [62.25]
64.78 [64.98]
69.24 [68.89]
68.54 [68.89]
68.82 [68.89]
68.89 [68.89]
—
—
7.29 [7.60]
8.51 [8.39]
9.35 [9.52]
9.38 [9.52]
9.41 [9.52]
9.28 [9.52]
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
74.84 [75.01]
10.39 [10.70]
7k (C11H17ClO2)a 1721
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
8k (C11H17ClO2)
7l (C11H17BrO2)
8l (C11H17BrO2)
7n (C9H13N)40
8n (C9H13N)41
7o (C9H14O2)a,38
8o (C9H14O2)a
7p (C15H20O2S)a
1720
1720
1720
—
217.0995e (217.0995)
260.0414b (260.0412)
818
—
967, 2222
2219
135.1049b (135.1048)
—
135.1047b (135.1048)
1689d
3100, 984, 827d
—
—
—
—
1624d
1597, 1316, 1142,
972, 811d
8p (C15H20O2S)a
7y (C12H18O4)37
8y (C12H18O4)37
9a (C11H18O2)
10a (C11H18O2)
9b (C12H20O2)42
10b (C12H20O2)
9d (C14H24O2)
10d (C14H24O2)
9n (C10H15N)a
10n (C10H15N)a
9p (C16H22O2S)a
—
—
—
—
—
—
264.1178b(264.1184)
—
—
—
—
—
—
—
1723
1723
1725
1724
1719
1720
1720
1721
—
1644
1635
1652
1642
1648
1641
1650
1641
1627d
—
—
—
816
—
818
—
72.25 [72.49]
72.11 [72.49]
—
73.48 [73.43]
74.95 [74.95]
74.72 [74.95]
—
9.80 [9.95]
9.73 [9.95]
—
10.06 [10.27]
10.43 [10.78]
10.61 [10.78]
—
816
—
2221d
150.1281e (150.1283)
150.1277e (150.1283)
278.1344b (278.1341)
—
—
—
—
—
1620d
1595, 1313, 1140,
970, 809d
10p (C16H22O2S)a
11a (C12H20O2)
12a (C12H20O2)
11b (C13H22O2)
12b (C13H22O2)
11n (C11H17N)a
12n (C11H17N)
11p (C17H24O2S)a
—
278.1341b (278.1341)
—
—
—
1725
1724
1721
1720
—
—
—
1653
1642
1651
1640
1627
1618
1620d
—
829
—
830
2221, 970,
2219
73.38 [73.43]
73.21 [73.43]
74.33 [74.24]
74.26 [74.24]
—
—
—
10.13 [10.27]
10.15 [10.27]
10.18 [10.54]
10.23 [10.54]
—
—
—
—
163.1277b (163.1283)
163.1278b (163.1283)
292.1497b (292.1497)
1597, 1315, 1142,
975, 811d
12p (C16H22O2S)a
—
—
—
292.1490b (292.1497)
a Obtained as a mixture with its stereoisomer. b EI. c Obtained as a mixture with its stereoisomer and the corresponding acids. d For mixtutre of
stereoisomers. e CI, M+ + H.
948 | Org. Biomol. Chem., 2006, 4, 942–952
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
Table 6 NMR data for photoproducts obtained from cyclopentane
Alkene
2a34
3a
dH/ppm
dC/ppm
1.38–1.50 (m, 2H), 1.58–1.78 (m, 4H), 1.80–1.90 (m, 2H), 2.59 (m, 1H, H4), 3.72 (s, 3H, OCH3), 5.80
(d, 1H, H2, J 15.6), 6.95 (dd, 1H, H3, J 15.6, J 8.0).
0.82–0.90 (m, 2H), 1.20–1.38 (m, 2H), 1.58–1.78 (m, 2H), 1.87–1.96 (m, 2H), 3.65 (m, 1H, H4), 3.70
(s, 3H, OCH3), 5.68 (d, 1H, H2, J 11.5), 6.12 (dd, 1H, H3, J 11.5, J 10.0).
1.30 (t, 3H, CH3CH2, J 7.0Hz), 1.36–1.41 (m, 2H), 1.59–1.80 (m, 4H), 1.81–1.88 (m, 2H), 2.60 (m,
1H, H4), 4.18 (q, 2H, OCH2, J 7.0), 5.80 (dd, 1H, H2, J 15.6, J 1.0), 6.95 (dd, 1H, H3, J 15.6, J 8.0).
1.28 (t, 3H, CH3CH2, J 7.0 Hz), 1.59–1.70 (m, 6H), 1.91–1.99 (m, 2H), 3.69 (m, 1H, H4), 4.16 (q,
2H, OCH2, J 7.0), 5.67 (dd, 1H, H2, J 11.3, J 1.1), 6.10 (dd, 1H, H3, J 11.3, J 9.8).
0.90 (d, 6H, (CH3)2CH, J 6.7), 1.33–1.38 (m, 2H), 1.57–1.78 (m, 4H), 1.88–1.95 (m, 2H), 1.92 (m,
1H, (CH3)2CH), 2.54 (m, 1H, H4), 3.86 (d, 2H, OCH2, J 6.7), 5.76 (d, 1H, H2, J 15.4), 6.90 (dd, 1H,
H3, J 15.4, J 7.6).
0.95 (d, 6H, (CH3)2CH, J 6.7), 1.23–1.28 (m, 2H), 1.59–1.71 (m, 4H), 1.93–1.98 (m, 3H), 3.68 (m,
1H, H4), 3.89 (d, 2H, OCH2, J 6.7), 5.68 (d, 1H, H2, J 11.5), 6.11 (dd, 1H, H3, J 11.5, J 10.0)
5.86 (dd, 1H, H2, J 15.6, J 0.98), 6.14 (dd, 1H, H3, J 15.6, J 8.0).
1.20–1.35 (m, 2H), 1.58–1.80 (m, 4H), 1.87–1.99 (m, 2H), 3.72 (m, 1H, H4), 5.15 (s, 2H, Ph–CH2),
5.73 (dd, 1H, H2, J 11.5, J 0.98), 6.14 (dd, 1H, H3, J 11.5, J 10.0), 7.10–7.40 (m, 5H, Ph).
1.36–1.43 (m, 2H), 1.58–1.73 (m, 4H), 1.81–1.84 (m, 2H), 3.40 (s, 3H, OCH3), 3.63 (t, 2H,
CH2OCH3, J 6.0), 4.28 (t, 2H, COOCH2, J 6.0), 5.84 (d, 1H, H2, J 15.6), 6.98 (dd, 1H, H3, J 15.6,
J 7.8).
0.85 (m, 1H), 1.16–1.25 (m, 2H), 1.61–1.69 (m, 4H), 1.92 (m, 1H), 3.38 (s, 3H, OCH3), 3.62 (t, 2H,
CH2OCH3, J 6.0), 4.26 (t, 2H, COOCH2, J 6.0), 5.73 (d, 1H, H2, J 11.7), 6.14 (dd, 1H, H3, J 11.7,
J 10.2).
167.2, 153.6, 118.7, 51.1, 42.6, 32.2, 25.0
166.9,155.6, 117.4, 50.8, 39.0, 33.3, 25.5
—
2b35
3b
167.0, 155.3, 117.9, 59.7, 39.1, 33.3, 26.0, 14.2
2d
167.1, 153.2, 118.9, 70.2, 42.8, 32.1, 27.7, 25.1,
19.2.
3d
166.7, 155.1, 118.0, 70.0, 39.2, 33.4, 27.7, 25.5,
19.2.
—
166.2, 155.9, 136.0, 128.5, 128.3, 128.1, 117.6,
65.6, 39.2, 33.6, 25.5.
166.9, 154.2, 118.9, 70.5, 63.2, 58.9, 42.7, 32.2,
25.1.
2fa
3f
2g
3g
167.1, 156.0, 118.3, 71.2, 63.5, 59.6, 39.9, 34.0,
26.2.
2h
3h
2i
1.26–1.36 (m, 2H), 1.37–1.46 (m, 2H), 1.50–1.82 (m, 12H), 2.22 (m, 1H, OCH2CH), 2.58 (m,1H,
H4), 4.00 (d, 2H, OCH2, J 6.8), 5.80 (d, 1H, H2, J 15.6), 6.94 (dd, 1H, H3, J 15.6, J 7.8).
1.20–1.32 (m, 2H), 1.55–1.90 (m, 12H), 2.22 (m, 1H, OCH2CH), 3.69 (m,1H, H4), 3.99 (d, 2H,
OCH2, J 6.8), 5.67 (d, 1H, H2, J 11.7), 6.10 (dd, 1H, H3, J 11.7, J 9.75).
167.5, 153.7, 119.6, 68.5, 43.1, 38.8, 38.7, 29.7,
25.5.
167.1, 155.4, 118.4, 68.2, 39.5, 38.8, 33.7, 29.7,
25.8, 25.6.
166.5, 154.0, 132.3, 118.9, 118.0, 64.8, 42.8,
32.2, 25.1.
1.37 (m, 2H), 1.59–1.69 (m, 4H), 1.83 (m, 2H), 2.58 (m, 1H, H4), 4.63 (d, 2H, OCH2, J 5.8), 5.23 and
=
=
5.31 (ds, 2H, CH CH2, J 10.2, J 15.6), 5.80 (d, 1H, H2, J 15.6), 5.96 (m, 1H, CH CH2), 6.00 (dd,
=
1H, CHCH CH, J 8.3, J 15.6).
3ia
2j
1.18 (m, 2H), 1.57–1.62 (m, 4H), 1.83 (m, 2H), 3.62 (m, 1H, H4), 4.53 (d, 2H, OCH2, J 5.8), 5.15 and
166.1, 155.9, 132.6, 117.9, 117.5, 64.5, 39.1,
33.3, 25.5.
=
=
5.23 (ds, 2H, CH CH2, J 10.2, J 17.0), 5.63 (d, 1H, H2, J 11.7), 5.85 (m, 1H, CH CH2), 6.07 (t,
1H, H3, J 11.7)
1.34–1.39 (m, 2H), 1.51–1.57 (m, 4H), 1.65–1.80 (m, 2H), 1.68 (s, 3H, CH3C), 1.72 (s, 3H, CH3C),
167.0, 153.6, 138.0, 119.2, 118.7, 61.0, 42.8,
32.3, 25.7, 25.2, 18.0.
=
2.54 (m, 1H, H4), 4.58 (d, 2H, OCH2, J 7.3), 5.32 (t, 1H, (C CHCH2, J 7.3), 5.75 (d, 1H, H2,
J 15.7), 6.92 (dd, 1H, H3, J 15.7, J 7.7).
3j
1.14–1.20 (m, 2H), 1.47–1.61 (m, 4H), 1.65 (s, 3H, CH3C), 1.70 (s, 3H, CH3C), 1.83–1.87 (m, 2H),
166.5, 155.5, 137.8, 118.9, 117.9, 60.7, 39.1,
33.4, 25.7, 25.5, 18.02.
=
3.60 (m, 1H, H4), 4.53 (d, 2H, OCH2, J 7.3), 5.30 (t, 1H, (C CHCH2, J 7.3), 5.62 (dd, 1H, H2,
J 11.3, J 1.01), 6.04 (dd, 1H, H3, J 11.3, J 9.9).
3k
1.25 (m, 2H), 1.60–1.72 (m, 4H), 1.91 (m, 2H), 3.67 (m, 1H, H4), 3.71 (t, 2H, CH2Cl, J 5.8), 4.36 (t,
2H, OCH2, J 5.8), 5.73 (d, 1H, H2, J 11.7), 6.18 (t, 1H, H3, J 11.7).
1.37 (m, 2H), 1.52–1.70 (m, 4H), 1.83 (m, 2H), 2.59 (m, 1H, H4), 3.54 (t, 2H, CH2Br, J 6.3),4.43 (t,
2H, OCH2, J 6.3), 5.80 (d, 1H, H2, J 15.6), 7.01 (dd, 1H, H3, J 8.3, J 15.6).
1.22 (m, 2H), 1.62–1.72 (m, 4H), 1.91 (m, 2H), 3.54 (t, 2H, CH2Br, J 6.3), 3.68 (m, 1H, H4), 4.42 (t,
2H, OCH2, J 6.3), 5.70 (d, 1H, H2, J 11.7), 6.19 (t, 1H, H3, J 11.7).
0.28 (s, 9H, CH3), 1.19–1.82 (m, 8H), 2.52 (m, 1H, H4), 5.67 (d, 1H, H2, J 15.6), 6.83 (dd, 1H, H3,
J 7.8, J 15.6).
166.0, 156.6, 117.0, 63.3, 41.5, 39.1, 33.2, 25.4.
167.0, 155.0, 118.5, 63.6, 42.9, 32.3, 28.9, 25.3.
165.9, 156.8, 117.2, 63.3, 39.4, 33.4, 28.9, 25.6.
—
2l
3l
2mb
3mb
2na
3n
0.28 (s, 9H, CH3), 1.19–1.82 (m, 8H), 3.59 (m, 1H, H4), 5.57 (d, 1H, H2, J 11.2), 6.04 (t, 1H, H3,
J 11.2).
1.30 (m, 2H), 1.55–1.77 (m, 4H), 1.88 (m, 2H), 2.51 (m, 1H, H4), 5.20 (d, 1H, H2, J 15.6), 6.63 (dd,
1H, H3, J 8.3, J 15.6).
1.35 (m, 2H), 1.63–1.74 (m, 4H), 1.94 (m, 2H), 3.00 (m, 1H, H4), 5.19 (d, 1H, H2, J 10.7), 6.38 (t, 1H,
H3, J 10.7).
1.38 (m, 2H), 1.43–1.70 (m, 4H), 1.86 (m, 2H), 2.56 (m, 1H, H4), 5.78 (d, 1H, H2, J 15.1), 7.03 (t, 1H,
H3, J 8.3, J 15.1), 10.32 (br s, 1H, OH)
1.26 (m, 2H), 1.51–1.70 (m, 4H), 1.88 (m, 2H), 3.66 (m, 1H, H4), 5.68 (d, 1H, H2, J 11.2), 6.21 (t, 1H,
H3, J 11.2), 10.31 (br s, 1H, OH)
1.35 (m, 2H), 1.59–1.67 (m, 4H), 1.84 (m, 2H), 2.42 (s, 3H, CH3), 2.61 (m, 1H, H3), 6.29 (d, 1H, H1,
J 15.1), 6.93 (dd, 1H, H2, J 7.8, J 15.1), 7.31 and 7.74 (d, 2H, J 8.3).
—
160.0, 117.6, 97.6, 43.8, 32.0, 25.0.
159.7, 116.2, 97.3, 42.5, 32.8, 25.4.
172.4, 156.5, 118.6, 42.9, 32.2, 25.2.
172.3, 158.0, 117.1, 39.1, 33.2, 25.4.
2o36
3o36
2pa
151.3, 151.0, 143.8, 139.1, 137.5, 129.6, 128.6,
128.5, 127.4, 127.2, 41.7, 37.6, 33.0, 31.7, 25.2,
24.8, 21.2c
.
3pa
2q35
2y
1.35 (m, 2H), 1.59–1.67 (4H, m), 1.84 (2H, m,), 2.42 (s, 3H, CH3), 3.71 (m, 1H, H3), 6.11 (t, 1H, H2,
J 10.7), 6.19 (d, 1H, H1, J 10.7), 7.31 and 7.77 (d, 2H, J 8.3).
1.40 (m, 2H), 1.64–1.78 (m, 4H), 1.86 (m 2H), 2.42 (s, 3H, COCH3), 2.60 (1H, H4), 6.05 (d, 1H, H2,
Jt.ans = 14.9), 6.77 (dd, 1H, H3, J 10.2, J 14.9).
—
=
1.52–1.58 (m, 8H), 2.68 (m, 1H, HCC C), 3.65 (s, 3H, OCH3), 3.77 (s, 3H, OCH3), 5.74 (d, 1H,
169.3, 165.4, 155.0, 117.0, 52.0, 51.6, 44.3,
30.0, 24.6.
168.9, 165.0, 155.0, 117.0, 61.1, 60.5, 44.3,
30.7, 24.7, 14.0.
168.9, 164.9, 154.5, 116.9, 71.3, 70.6, 44.3,
30.8, 27.5, 24.6, 19.1, 19.0.
168.9, 164.9, 154.5, 125.2, 71.2, 70.7, 38.7,
31.5, 27.6, 26.4, 19.1, 18.8.
168.2, 164.5, 153.3, 118.2, 82.0, 80.5, 44.3,
30.5, 28.0, 27.9, 24.7.
167.0, 164.9, 152.0, 125.9, 81.7, 81.0, 38.8,
31.4, 28.0, 27.8, 26.4.
=
C
CH, J 1.46).
2z
1.27 (t, 3H, CH3CH2, J 7.1), 1.33 (t, 3H, CH3CH2, J 7.1), 1.52–1.58 (m, 8H), 2.75 (m, 1H,
=
=
HCC C), 4.10 (q, 2H, CH3CH2, J 7.1), 4.30 (q, 2H, CH3CH2, J 7.1), 5.77 (d, 1H, C CH, J 1.47).
0.85 (d, 6H, Me, J 6.3), 0.87 (d, 6H, Me, J 6.3), 1.53–1.91 (m, 8H, CH2), 1.93 (m, 2H, CHMe), 2.67
2aa
3aa
2bb
3bb
=
=
(m, 1H, HCC C), 3.80 and 3.92 (ds, 4H, OCH2, J 6.8), 5.71 (s, 1H, C CH).
0.96 (d, 6H, Me, J 6.3), 0.97 (d, 6H, Me, J 6.3), 1.58–1.95 (m, 8H, CH2), 1.98(m, 2H, CHMe), 2.79
=
=
(m, 1H, CHC C), 3.94 and 4.00 (ds, 4H, OCH2, J 6.8), 6.49 (s, 1H, C CH).
=
1.34–1.80 (m, 8H), 1.38 (s, 9H, C(CH3)3), 1.52 (s, 9H, C(CH3)3), 2.66 (m, 1H, HCC C), 5.59 (s, 1H,
=
CH).
C
=
1.45 (s, 9H, C(CH3)3), 1.46 (s, 9H, C(CH3)3), 1.40–1.80 (m, 8H), 3.70 (m, 1H, HCC C), 6.25 (s, 1H,
=
CH).
C
a Obtained as a mixture with its stereoisomer. b Obtained as a mixture with its stereoisomer and the corresponding acids. c For mixture of stereoisomers.
This journal is The Royal Society of Chemistry 2006 Org. Biomol. Chem., 2006, 4, 942–952 | 949
©

View Article Online
Table 7 NMR data for photoproducts obtained from cyclohexane, cycloheptane and cyclooctane
dH/ppm
dC/ppm
7a38
8a39
7b22
8b22
7ca,34
8c
1.12–1.34 (m, 5H), 1.65–1.77 (m, 5H), 2.13 (m, 1H, H4), 3.72 (s, 3H, OMe), 5.78 (d, 1H, H2,
J 15.7), 6.91 (dd, 1H, H3, J 6.9, J 15.7).
0.99–1.30 (m, 5H), 1.54–1.72 (m, 5H), 3.24 (m, 1H, H4), 3.63 (s, 3H, OMe), 5.58 (d, 1H, H2,
J 11.3), 5.96 (t, 1H, H3, J 11.3).
167.4, 154.4, 118.3, 51.2, 40.3, 32.2, 25.7, 25.5.
166.7, 155.9, 117.1, 50.9, 37.3, 32.2, 25.8, 25.4.
167.0, 154.1, 118.7, 60.0, 40.3, 31.6, 25.8 25.6, 14.1
166.4, 155.5, 117.6, 59.7, 37.3, 32.3, 25.8, 25.4, 14.2.
1.12–1.30 (m, 4H), 1.28 (t, 3H, Me, J 6.9), 1.65–1.83 (m, 6H), 2.13 (m, 1H, H4), 4.17 (q, 2H,
CH2O, J 6.9), 5.74 (d, 1H, H2, J 15.7), 6.90 (dd, 1H, H3, J 6.9, J 15.7)
1.12–1.39 (m, 4H), 1.33 (t, 3H, Me, J 6.9), 1.65–1.73 (m, 6H), 3.27 (m, 1H, H4), 4.15 (q, 2H,
CH2O, J 6.9), 5.66 (d, 1H, H2, J 11.7), 6.02 (dd, 1H, H3, J 9.8, J 11.7)
0.86–1.28 (m, 5H), 0.88 (t, 3H, Me, J 7.3), 1.57–1.69 (m, 5H), 1.58 (m, 3H, MeCH2), 2.04 (m, 1H,
H4), 3.99 (t, 2H, CH2O, J 6.9), 5.71 (d, 1H, H2, J 15.7), 6.82 (dd, 1H, H3, J 6.5, J 15.7).
0.87–1.29 (m, 5H), 0.89 (t, 3H, Me, J 7.3), 1.56–1.69 (m, 5H), 1.58 (m, 3H, MeCH2), 3.22 (m, 1H,
H4), 3.99 (t, 2H, CH2O, J 6.9), 5.57 (d, 1H, H2, J 11.7), 5.95 (t, 1H, H3, J 11.7).
0.80 (d, 3H, MeCH, J 6.5), 0.86 (t, 3H, MeCH2, J 6.5), 0.99–1.66 (m, 13H), 2.07 (m, 1H, H4), 3.86
and 3.96 (dd, 1H, CH2O, J 6.5, J 10.9), 5.70 (d, 1H, H2, J 15.7), 6.87 (dd, 1H, H3, J 6.5, J 15.7).
0.80 (d, 3H, MeCH, J 6.5), 0.86 (t, 3H, MeCH2, J 6.5), 0.99–1.66 (m, 13H), 3.21 (m, 1H, H4),
3.84 and 3.94 (dd, 1H, CH2O, J 6.5, J 10.9), 5.60 (d, 1H, H2, J 11.7), 5.94 (t, 1H, H3, J 11.7).
1.03–1.48 (m, 5H), 1.54–1.71 (m, 5H), 2.03 (m, 1H, H4), 3.63 (t, 2H, CH2Cl, J 5.8), 4.30 (t, 2H,
OCH2, J 5.8), 5.70 (d, 1H, H2, J 15.6), 6.91 (dd, 1H, H3, J 6.3, J 15.6).
0.85–1.37 (m, 5H), 1.59–1.66 (m, 5H), 3.19 (m, 1H, H4), 3.63 (t, 2H, CH2Cl, J 5.8), 4.27 (t, 2H,
OCH2, J 5.8), 5.60 (d, 1H, H2, J 11.2), 6.02 (t, 1H, H3, J 11.2).
0.84–1.34 (m, 5H), 1.66–1.78 (m, 5H), 2.15 (m, 1H, H4), 3.54 (t, 2H, CH2Br, J 6.3), 4.43 (t, 2H,
OCH2, J 6.3), 5.81 (dd, 1H, H2, JLR 0.9, J 15.6), 6.99 (dd, 1H, H3, J 6.3, J 15.6).
0.83–1.41 (m, 5H), 1.64–1.73 (m, 5H), 3.27 (m, 1H, H4), 3.54 (t, 2H, CH2Br, J 6.3), 4.42 (t, 2H,
OCH2, J 6.3), 5.70 (dd, 1H, H2, JLR 0.9, J 11.7), 6.10 (t, 1H, H3, J 11.7).
0.88–1.39 (m, 5H), 1.62–1.77 (m, 5H), 2.13 (m, 1H, H4), 5.24 (d, 1H, H2, J 16.6), 6.66 (dd, 1H,
H3, J 6.8, J 16.6).
0.88–1.39 (m, 5H), 1.62–1.76 (m, 5H), 2.60 (m, 1H, H4), 5.22 (d, 1H, H2, J 10.7), 6.29 (t, 1H, H3,
J 10.7).
0.88–1.38 (m, 5H), 1.66–1.78 (m, 5H), 2.18 (m, 1H, H4), 5.76 (d, 1H, H2, J 15.6), 7.02 (dd, 1H,
H3, J 6.8, J 15.6), 10.83 (br s, OH).
167.1, 154.1, 118.7, 65.3, 40.2, 32.2, 25.6, 25.4, 22.0,
10.3.
166.8, 155.4, 117.6, 65.8, 37.3, 31.5, 25.8, 25.3, 21.9,
10.4.
167.1, 154.1, 118.7, 68.7, 40.3, 32.2, 30.5, 26.2, 25.8,
25.6, 16.3, 11.1.
166.7, 155.2, 117.6, 68.5, 37.3, 30.6, 30.0, 26.0, 25.8,
25.4, 16.4, 11.1.
7ea
8e
7ka
8k
166.5, 155.6, 118.0, 63.8, 41.6, 40.4, 31.5, 25.7, 25.6.
165.7, 156.8, 116.7, 63.4, 41.5, 37.4, 32.2, 25.7, 25.3.
7l
166.3, 155.5, 117.9, 63.4, 40.3, 31.4, 28.7, 25.7, 25.5.
8l
165.0, 156.9, 116.7, 63.2, 37.4, 32.2, 28.8, 25.8, 25.4.
7n40
8n41
7oa,38
8oa
7pa
8pa
7y37
8y37
9a
—
—
172.6, 172.1, 158.1, 157.1, 118.2, 117.0, 40.3, 37.3, 32.0,
31.3, 25.7, 25.5, 25.2b.
0.88–1.38 (m, 5H), 1.66–1.78 (m, 5H), 3.28 (m, 1H, H4), 5.66 (dd, 1H, H2, J 11.2), 6.15 (t, 1H,
H3, J 11.2), 10.83 (br s, OH).
1.10–1.28 (m, 5H), 1.64–1.73 (m, 5H), 2.15 (m, 1H, H3), 6.25 (d, 1H, H1, J 15.1), 2.42 (s, 3H,
Me), 6.90 (dd, 1H, H2, J 6.3, J 15.1), 7.31 and 7.73 (d, 2H, J 8.3).
1.10–1.28 (m, 5H), 1.64–1.73 (m, 5H), 2.42 (s, 3H, Me), 3.31 (m, 1H, H3), 6.00 (t, 1H, H2, J 10.7),
6.19 (d, 1H, H1, J 10.7), 7.31 and 7.78 (d, 2H, J 8.3).
151.3, 151.0, 144.0, 137.6, 129.7, 128.5, 127.2, 126.8,
39.7, 36.3, 31.8, 31.1, 25.6, 25.4, 25.0, 21.5b.
=
1.10–1.40 (m, 5H), 1.70–1.90 (m, 5H), 2.30 (m, 1H, HCC C), 3.71 (s, 3H, OMe), 3.84 (s, 3H,
OMe), 5.76 (d, 1H, C CH, JLR 1.2)
169.3, 165.6, 156.2, 116.8, 52.0, 51.6, 42.2, 31.0, 26.0,
25.7.
—
=
=
1.10–1.40 (m, 5H), 1.70–1.90 (m, 5H), 3.30 (m, 1H, HCC C), 3.68 (s, 3H, OMe), 3.70 (s, 3H,
=
OMe), 6.31 (s, 1H, C CH)
1.38–1.82 (m, 12H), 2.30 (m, 1H, H4), 3.72 (s, 3H, OMe), 5.74 (dd, 1H, H2, JLR 1.46, J 15.6), 6.97
168.0, 155.0, 118.0, 51.3, 42.3, 33.4, 28.3, 26.0.
166.7, 156.6, 116.0, 51.0, 38.5, 34.1, 28.3, 26.4.
167.2, 154.1, 117.9, 60.1, 42.3, 33.3, 28.3, 26.0, 14.3.
166.0, 156.6, 116.0, 59.7, 38.5, 34.2, 28.4, 26.4, 14.3.
(dd, 1H, H3, J 7.6, J 15.6,).
10a
9b42
10b
9d
1.25–1.80 (m, 12H), 3.40 (m, 1H, H4), 3.72 (s, 3H, OMe), 5.61 (d, 1H, H2, J 11.5), 6.12 (dd, 1H,
H3, J 10.5, J 11.5).
1.33 (t, 3H, MeCH2, J 7.1), 1.60–1.80 (m, 12H), 2.30 (m, 1H, H4), 4.15 (q, 2H, OCH2, J 7.1),
5.74 (dd, 1H, H2, JLR 1.2, J 15.8), 6.95 (dd, 1H, H3, J 7.6, J 15.8)
1.28 (t, 3H, MeCH2, J 7.1), 1.60–1.80 (m, 12H), 3.46 (m, 1H, H4), 4.15 (q, 2H, OCH2, J 7.1),
5.60 (dd, 1H, H2, JLR 1.0, J 11.5), 6.10 (dd, 1H, H3, J 10.0, J 11.5).
0.95 (d, 6H, Me2CH, J 6.6), 1.38–1.80 (m, 12H), 1.95 (m, 1H, Me2CH), 2.34 (m, 1H, H4), 3.90
(d, 2H, OCH2, J 6.6), 5.75 (dd, 1H, H2, JLR 1.2, J 15.6,), 6.95 (dd, 1H, H3, J 7.6, J 15.6).
0.95 (d, 6H, Me2CH, J 6.6), 1.25–1.31 (m, 2H), 1.34–1.76 (m, 10H), 1.95 (m, 1H, Me2CH), 3.45
(m, 1H, H4), 3.89 (d, 2H, OCH2, J 6.6), 5.62 (d, 1H, H2, J 11.5), 6.10 (dd, 1H, H3, J 10.0, J 11.5).
1.34–1.76 (m, 12H), 2.32 (m, 1H, H4), 5.23 (d, 1H, H2, J 16.6), 6.69 (dd, 1H, H3, J 7.8, J 16.6).
1.37–1.75 (m, 12H), 2.75 (m, 1H, H4), 5.17 (d, 1H, H2, J 10.7), 6.38 (t, 1H, H3, J 10.7).
1.22–1.72 (m, 12H), 2.29 (m, 1H, H3), 2.35 (s, 3H, Me), 6.12 (d, 1H, H1, J 15.1), 6.88 (dd, 1H, H2,
J 7.3, J 15.1), 7.23 and 7.66 (d, 2H, J 8.3).
167.2, 155.2, 118.1, 70.2, 42.2, 33.3, 28.2, 27.7, 26.0,
19.0.
166.1, 156.0, 116.2, 70.0, 38.6, 34.3, 28.3, 27.7, 23.6,
19.2.
161.5, 117.9, 96.9, 43.4, 32.9, 28.0, 26.1.
160.6, 116.2, 95.9, 42.5, 33.6, 28.2, 26.2.
151.8, 145.1, 137.8, 129.7, 127.9, 127.4, 41.6, 32.9, 28.0,
26.0, 21.5.
10d
9nc
10nc
9pa
10pd
11a
12a
11b
12b
1.22–1.72 (m, 12H), 2.35 (s, 3H, Me), 3.37 (m, 1H, H3), 6.00 (t, 1H, H2, J 10.7), 6.04 (d, 1H, H1,
151.9, 145.1, 137.8, 129.7, 127.9, 127.4, 37.2, 33.4, 28.0,
25.9, 21.5.
168.1, 156.0, 118.0, 51.0, 40.6, 30.4, 27.2, 24.8, 26.3.
J 10.7), 7.23 and 7.72 (d, 2H, J 8.3).
1.40–1.80 (m, 14H), 2.20 (m, 1H, H4), 3.72 (s, 3H, OMe), 5.75 (dd, 1H, H2, JLR 1.46, J 15.5), 6.95
(dd, 1H, H3, J 7.6, J 15.5).
1.30–1.80 (m, 14H), 3.60 (m, 1H, H4), 3.70 (s, 3H, OMe), 5.62 (dd, 1H, H2, JLR 1.2, J 11.5), 6.13
(dd, 1H, H3, J 10.0, J 11.5,).
1.26 (t, 3H, MeCH2, J 7.0), 1.49–1.66 (m, 10H), 1.69–1.72 (m, 4H), 2.35 (m, 1H, H4), 4.15 (q, 2H,
OCH2, J 7.0), 5.72 (dd, 1H, H2, JLR 1.0, J 15.7), 6.92 (dd, 1H, H3, J 7.3, J 15.7)
1.22 (t, 3H, MeCH2, J 7.3), 1.30–1.35 (m, 2H), 1.45–1.60 (m, 12H), 3.49 (m, 1H, H4), 4.10 (q, 2H,
OCH2, J 7.3), 5.52 (dd, 1H, H2, JLR 1.0, J 11.4), 6.03 (dd, 1H, H3, J 10.3, J 11.4).
1.45–1.70 (m, 14H), 2.38 (m, 1H, H4), 5.23 (d, 1H, H2, J 16.6), 6.68 (dd, 1H, H3, J 7.3, J 16.6).
1.49–1.75 (m, 12H), 2.82 (m, 1H, H4), 5.15 (d, 1H, H2, J 10.7), 6.40 (t, 1H, H3, J 10.7).
1.27–1.74 (m, 14H), 2.43 (s, 3H, Me), 2.45 (m, 1H, H3), 6.20 (d, 1H, H1, J 15.1), 6.93 (dd, 1H, H2,
J 7.3, J 15.1). 7.23 and 7.65 (d, 2H, J 8.3).
165.1, 157.2, 115.6, 51.0, 36.2, 32.0, 26.9, 25.1, 26.3.
167.2, 155.3, 118.5, 60.1, 40.6, 30.5, 27.2, 25.9, 24.8,
14.3.
166.5, 156.6, 116.0, 59.7, 36.3, 32.1, 26.9, 26.4, 25.1,
14.3.
161.8, 117.8, 97.0, 41.6, 31.9, 26.9, 25.8, 24.6.
160.9, 116.1, 96.0, 40.7, 31.2, 26.8, 25.9, 24.8.
152.3, 152.1, 144.0, 138.0, 129.8, 128.0, 127.4, 127.1,
39.8, 36.1, 31.3, 30.2, 26.9, 26.6, 26.1, 25.6, 24.6, 21.5b.
11na
12n
11pa
12pa
1.27–1.74 (m, 14H), 2.43 (s, 3H, Me), 3.54 (m, 1H, H3), 6.05 (t, 1H, H2, J 10.7), 6.13 (d, 1H, H1,
J 10.7), 7.23 and 7.72 (d, J 8.3).
a Obtained as a mixture with its stereoisomer. b For mixture of stereoisomers. c Obtained as a mixture with benzophenone. d Obtained as a mixture with
benzopinacol.
950 | Org. Biomol. Chem., 2006, 4, 942–952
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
t, J = 7.1 Hz, CH C), 7.20–7.40 (5H; m); 13C NMR (100 MHz,
therein; (b) A. F. Shilov and G. B. Shul’pin, Chem. Rev., 1997,
97, 2879–2932; (c) G. Dyker, Angew. Chem., Int. Ed. Engl., 1999,
38, 1698–1712; (d) W. D. Jones, in Topics in Current Chemistry,
vol. 3: Activation of Unactivated Bonds and Organic Synthesis, ed.
S. Murai, Springer-Verlag, 1999, pp. 9–46; F. Kakiuchi and S. Murai,
in Topics in Current Chemistry, vol. 3: Activation of Unactivated
Bonds and Organic Synthesis, ed. S. Murai, Springer-Verlag, 1999,
pp. 47–79.
=
CDCl3) d 172.3, 147.5, 136.0, 128.5, 128.3, 128.1, 111.1, 66.2, 35.0,
33.6, 36.3. C15H18O2 requires: C, 78.23; H, 7.88%; found: C, 78.32;
H, 8.05%.
Irradiation of methyl (Z)-3-cycloheptyl-2-propenoate 10a. Irra-
diation of 10a in the standard way for 5 h resulted in the formation
of methyl 3-cycloheptylidenepropanoate 16 (70%), which was
2 D. P. Curran, Synthesis, 1988, 417–439.
3 P. Dowd and W. Zhang, Chem. Rev., 1993, 93, 2091–2115.
4 H. Suginome, in CRC Handbook of Organic Photochemistry and
Photobiology (2nd edn), ed. W. Horspool and F. Lenci, CRC Press LLC,
Florida, 2003, pp. 102/1–102/16.
1
obtained as a colourless liquid: mmax(film)/cm−1 1741; H NMR
(400 MHz, CDCl3) d 1.49–1.57 (8H, m), 2.21–2.36 (4H, m,
=
(H2C)C CH)), 3.03 (2H, d, J = 6.8 Hz, CH2CO), 3.60 (3H, s,
5 G. Pattenden, Chem. Soc. Rev., 1988, 17, 361–382.
6 M. Ramaiah, Tetrahedron, 1987, 43, 3541–3676.
7 B. Giese, P. Erdmann, T. Gobel and R. Springer, Tetrahedron Lett.,
1992, 33, 4545–4548.
8 A. F. Parsons, An Introduction to Free Radical Chemistry, Blackwell
Science, Oxford, 2000.
OCH3), 5.33 (1H, t, J = 6.8 Hz, CH C); 13C NMR (100 MHz,
=
CDCl3) d 173.0, 145.0, 116.0, 52.2, 37.6, 33.2, 30.2, 29.0, 26.0.
C11H18O2 requires: C, 72.49; H, 9.95%; found: C, 72.22; H, 10.27%.
9 (a) J. E. Baldwin and D. R. Kelly, J. Chem. Soc., Chem. Commun.,
1985, 682–684; (b) G. A. Russell and P. Ngoviwatchai, Tetrahedron
Lett., 1985, 26, 4975–4978.
10 G. E. Keck, E. J. Enholm, J. B. Yates and M. R. Wiley, Tetrahedron,
1985, 41, 4079–4094.
11 (a) G. A. Russell, H. Tashtoush and P. Ngoviwatchi, J. Am. Chem.
Soc., 1984, 106, 4622–4623; (b) G. A. Russell and P. Ngoviwatchai,
Tetrahedron Lett., 1986, 27, 3479–3482.
12 (a) G. E. Keck and J. H. Byers, J. Org. Chem., 1985, 50, 5442–5444;
(b) G. A. Russell, Acc. Chem. Res., 1989, 22, 1–8; (c) G. A. Russell,
P. Ngoviwatchi and Y. W. Wu, J. Am. Chem. Soc., 1989, 111, 4921–
4927; (d) C. C. Huval and D. A. Singleton, Tetrahedron Lett., 1993, 34,
3041–3042.
Irradiation of methyl (Z)-3-cyclooctyl-2-propenoate 12a. Ir-
radiation of 12a as described above for 6.5 h resulted in the
formation of methyl 3-cyclooctylidenepropanoate 17 (67%), which
was obtained as a colourless liquid: mmax(film)/cm−1 1742; 1H NMR
(400 MHz, CDCl3) d 1.43–1.54 (6H, m), 1.56–1.68 (6H, m), 2.14–
=
2.23 (4H, m, (H2C)C CH), 3.07 (2H, d, J = 7.0 Hz, CH2CO),
3.68 (3H, s, OCH3), 5.36 (1H, t, J = 7.0 Hz, CH C); 13C NMR
=
(100 MHz, CDCl3) d 173.0, 145.1, 116.0, 51.6, 37.5, 33.4, 29.0,
27.2, 26.9, 26.1, 25.9, 25.8. C11H18O2 requires: C, 73.43; H, 10.27%;
found: C, 73.34; H, 10.19%.
13 (a) J. Gong and P. L. Fuchs, J. Am. Chem. Soc., 1996, 118, 4486–
4487; (b) J. Xiang and P. L. Fuchs, J. Am. Chem. Soc., 1996, 118,
11986–11987; (c) J. Xiang, W. Jiang, J. Gong and P. L. Fuchs, J. Am.
Chem. Soc., 1997, 119, 4123–4129; (d) J. Xiang, W. Jiang and P. L.
Fuchs, Tetrahedron Lett., 1997, 38, 6635–6638; (e) J. Xiang, J. Evarts,
A. Rivkin, D. P. Curran and P. L. Fuchs, Tetrahedron Lett., 1998, 39,
4163–4166.
Irradiation of dimethyl (Z)-2-cyclopentyl-2-butendioate 2y.
A
solution of 2y (0.22 g, 1.00 mmol) in cyclopentane (20 ml)
containing 3 drops of NEt3 was irradiated in a quartz tubes
using 254 nm lamps for 25 h. At this point no 2y remained and
two products had formed in a 1 : 1 ratio. The crude product
was chromatographed on silica gel (ether–petroleum ether, 0–
20%), the first product eluting being dimethyl 2-cyclopent-1-en-
14 S. Kim, N. Kim, W. Chung and C. H. Cho, Synlett, 2001, 937–
940.
15 (a) A. Horowitz and L. A. Rajbenback, J. Am. Chem. Soc., 1969, 91,
4626–4631; (b) M. Zupan, J. Org. Chem., 1978, 43, 2297–2299; (c) P. J.
Wagner, R. J. Truman and J. C. Scaiano, J. Am. Chem. Soc., 1985, 107,
7093–7097; (d) S. H. Brown and R. H. Crabtree, J. Am. Chem. Soc.,
1989, 111, 2935–2946; (e) J. A. Balan and B. P. Roberts, J. Chem. Soc.,
Perkin Trans. 2, 1981, 161–166; (f) Ref. 12a.
16 C. Walling and M. J. Gibian, J. Am. Chem. Soc., 1965, 87, 3361–3364.
17 (a) Ref. 15e; (b) B. Giese and S. Lachhein, Angew. Chem., Int. Ed. Engl.,
1982, 21, 768–775.
18 C. Manfrotto, M. Mella, M. Freccero, M. Fagnoni and A. Albini,
J. Org. Chem., 1999, 64, 5024–5028; R. Mosca, M. Fagnoni, M. Mella
and A. Albini, Tetrahedron, 2001, 57, 10319–10328.
19 D. Dondi, I. Caprioli, M. Fagnoni, M. Mella and A. Albini, Tetrahe-
dron, 2003, 59, 947–957.
20 A. M. Cardarelli, M. Fagnoni, M. Mella and A. Albini, J. Org. Chem.,
2001, 66, 7320–7327.
21 A. M. Gonzalez-Cameno, M. Mella, M. Fagnoni and A. Albini, J. Org.
Chem., 2000, 65, 297–303.
22 G. Buchi and S. H. Feairheller, J. Org. Chem., 1969, 34, 609–
612.
23 E. Grovenstein, T. C. Campbell and T. Shibata, J. Org. Chem., 1969,
34, 2418–2428.
24 P. Singh, J. Org. Chem., 1972, 37, 836–841.
1
1-ylsuccinate 19 (0.07 g, 30%): mmax(film)/cm−1 1738; H NMR
(400 MHz, CDCl3) d 1.88 (2H, m), 2.26–2.34 (4H, m), 2.55
(1H, dd, Jgem = 16.5, Jvic = 5.5 Hz, HCHCO), 2.94 (1H, dd,
Jgem = 16.5, Jvic = 9.8 Hz, HCHCO), 3.65 (1H, m, CHCO), 3.68
=
(3H, s, OCH3), 3.71 (3H, s, OCH3), 5.55 (1H, broad s, CH C);
13C NMR (100 MHz, CDCl3) d 173.2, 172.3, 139.6, 127.8, 52.7,
51.2, 43.2, 35.0, 33.3, 32.4, 22.9. C11H16O4 requires: C, 62.25; H,
7.60%; found: C, 62.36; H, 7.81%. Further elution gave dimethyl 2-
cyclopentylidenesuccinate 18 (0,06 g, 26%): mmax(film)/cm−1 1740,
1719; 1H NMR (400 MHz, CDCl3) d 1.67–1.76 (4H, m), 2.40 (2H,
=
=
t, J = 7.0 Hz, CH2C C), 2.82 (2H, t, J = 7.0 Hz, CH2C C),
3.35 (2H, s, CH2CO), 3.68 (3H, s, OCH3), 3.72 (3H, s, OCH3); 13
C
NMR (100 MHz, CDCl3) d 171.9, 167.5, 165.3, 116.6, 51.8, 51.4,
35.8, 34.5, 34.1, 26.9, 25.5. C11H16O4 requires: C, 62.25; H, 7.60%;
found: C, 62.23; H, 7.74%.
Acknowledgements
25 G. Ahlgren, J. Org. Chem., 1973, 38, 1369–1374.
26 D. K. Wedegaertner, R. M. Kopchik and J. A. Kampmeir, J. Am. Chem.
Soc., 1971, 93, 6890–6895, and references therein.
The funding provided to R.A.D. and J.J.H. by Enterprise Ireland,
Donegal County Council, Limerick Corporation and the IHP
programme of EU-DGXII is gratefully acknowledged.
27 J. G. Traynham and Y.-S. Lee, J. Am. Chem. Soc., 1974, 96, 3590–
3594.
28 E. L. Eliel and S. H. Wilen, Stereochemistry of Organic Compounds,
Wiley, New York, 1993, p. 679.
29 V. Malatesta and K. U. Ingold, J. Am. Chem. Soc., 1981, 103, 609–
References
614.
30 P. S. Engel and A. M. Culotta, J. Am. Chem. Soc., 1991, 113, 2686–
2696.
1 (a) P. A. MacFaul, I. W. C. E. Arends, K. U. Ingold and D. D. M.
Wagner, J. Chem. Soc., Perkin Trans. 2, 1997, 135–145, and references
This journal is
The Royal Society of Chemistry 2006
Org. Biomol. Chem., 2006, 4, 942–952 | 951
©

View Article Online
31 R. A. Doohan and N. W. A. Geraghty, Green Chem., 2005, 7, 91–96.
32 A. Padwa and G. S. K. Wong, J. Org. Chem., 1986, 51, 3125–3133.
33 C. L. Jenkins and J. K. Kochi, J. Org. Chem., 1971, 36, 3103–3111.
34 R. D. Hubbard and B. L. Miller, J. Org. Chem., 1998, 63, 4143–
4146.
37 H. Alper, B. Despeyroux and J. B. Woell, Tetrahedron Lett., 1983, 24,
5691–5694.
38 R. C. Larock, J. Org. Chem., 1975, 40, 3237–3242.
39 V. J. Patil and U. Mavers, Tetrahedron Lett., 1996, 37, 1281–1284.
40 G. Zweifel, J. T. Snow and C. C. Whiting, J. Am. Chem. Soc., 1968, 90,
7139–7141.
41 Y. Sato and Y. Niinomi, J. Chem. Soc., Chem. Commun., 1982, 56–57.
42 K. Itoh, M. Kori, Y. Inada, K. Nishihara, Y. Kawamatsu and H.
Sugihara, Chem. Pharm. Bull., 1986, 34, 1128–1147.
35 H. Bhandal, A. R. Howell, V. F. Patel and G. Pattenden, J. Chem. Soc.,
Perkin Trans. 1, 1990, 2709–2714.
36 R. Roth and H. Erlenmeyer, Helv. Chim. Acta, 1955, 63, 1276–
1279.
952 | Org. Biomol. Chem., 2006, 4, 942–952
This journal is
The Royal Society of Chemistry 2006
©