Synthesis of α-hydroxyallenes by copper-catalyzed S N2′substitution of propargylic dioxolanones

Article abstract of DOI:10.1002/ejoc.200900226

A new catalytic method for the synthesis of α-hydroxyallenes is described. Efficient S_N2′ substitution of propargylic dioxolanones has been achieved with a copper(I)/P(OBu)₃ catalyst: using Grignard reagents as the nucleophiles. The

Full text of DOI:10.1002/ejoc.200900226

FULL PAPER
DOI: 10.1002/ejoc.200900226
Synthesis of α-Hydroxyallenes by Copper-Catalyzed SN2Ј Substitution of
Propargylic Dioxolanones
Xiaoping Tang,[a] Simon Woodward,*[a] and Norbert Krause*[b]
Keywords: Allenes / Copper / Homogeneous catalysis / Nucleophilic substitution / Grignard reaction
A new catalytic method for the synthesis of α-hydroxyallenes
is described. Efficient SN2Ј substitution of propargylic dioxol-
anones has been achieved with a copper(I)/P(OBu)3 catalyst
using Grignard reagents as the nucleophiles. The reaction
tolerates a wide variety of propargylic dioxolanones, the cor-
responding primary and secondary α-hydroxyallenes are ob-
tained in good to excellent yields and excellent diastereo-
selectivity.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
but few other complimentary approaches have been re-
ported.[15] α-Hydroxyallenes are valuable synthetic interme-
diates in organic synthesis, which readily undergo further
transformations often with good to complete transfer of the
allenic chirality.[16] Recently, gold-catalyzed cycloisomeriza-
tion of α-hydroxyallenes and α-allenic ketones has been de-
veloped.[17] In connection with this chemistry it is beneficial
to develop new and versatile methods for the synthesis of
α-hydroxyallenes.
Propargylic dioxolanones are very promising alternatives
to propargylic epoxides in the synthesis of α-hydroxyallene
for three reasons: i) under a SN2Ј pathways, the release of
CO2 is expected to facilitate the formation of the α-hy-
droxyallene (Scheme 2); ii) dioxolanones can be easily pre-
pared from an enyne via a dihydroxylation and lactoni-
zation sequence; iii) asymmetric dihydroxylation[18] can be
used to prepare the diol precursor, which can provide a
route for the synthesis of enantiomerically enriched α-hy-
droxyallenes.
Introduction
Allenes are highly valuable synthetic precursors in or-
ganic chemistry. Their unique structure is an essential pre-
requisite for the synthesis of many structurally interesting
and biologically active compounds.[1] Over the past 30
years, the use of organometallic reagents for the synthesis
of allenes has been highly developed.[2] In particular, the
metal-mediated SN2Ј nucleophilic substitution of propar-
gylic electrophiles proved to be one of the most general
methods for the preparation of various allenes. The electro-
philic propargylic moiety can bear an epoxide,[3] an ether,[4]
a halide,[5] an acetate,[6] an acetal,[7] or a sulfonate,[8,9] as
the leaving group, the complimentary organometallic nu-
cleophile can either be an organocopper,[10] a Grignard rea-
gent,[11] an organozinc[12] or an organoboronate[13] deriva-
tive (Scheme 1).
Scheme 1. SN2Ј nucleophile substitution of propargylic electro-
philes.
A large number of methods have been developed for the
synthesis of allenes. α-Hydroxyallenes are typically ob-
tained from the corresponding propargylic epoxide,[3,12,14]
Scheme 2. Formation of α-hydroxyallenes from propargylic dioxol-
anones.
Herein, we report an efficient copper-catalyzed SN2Ј sub-
stitution of propargylic dioxolanones for the synthesis of
α-hydroxyallenes (Scheme 3). The inexpensive and readily
available copper salt [Cu(MeCN)4][BF4][19] together with
tributyl phosphite are used as the catalyst, while a Grignard
reagent acts as the nucleophile. A range of primary and
secondary α-hydroxyallenes has been synthesized in good
to excellent yields and excellent diastereoselectivity.
[a] School of Chemistry, The University of Nottingham,
University Park, Nottingham, NG7 2RD, UK
Fax: +44-115-951-3564
E-mail: simon.woodward@nottingham.ac.uk
[b] Organic Chemistry, Dortmund University of Technology,
Otto-Hahn-Straβe 6, 44227 Dortmund, Germany
Fax: +49-231-755-3884
E-mail: norbert.krause@tu-dortmund.de
Supporting information for this article is available on the
WWW under http://www.eurjoc.org/ or from the author.
2836
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 2836–2844

Hydroxyallenes from Propargylic Dioxolanones
Initial studies towards developing an efficient copper-cat-
alyzed SN2Ј substitution of 3 showed that several possible
byproducts can be formed in the catalytic reaction (Fig-
ure 1). The SN2 product was observed together with the de-
sired SN2Ј adduct. Diol 2 was also obtained as a byproduct,
formed by nucleophilic attack at the carbonyl group. More-
over, a small amount of enyne 1 was observed as well due
to an electron transfer reaction.
Scheme 3. Copper-catalyzed SN2Ј substitution of propargylic diox-
olanones.
Results and Discussion
Synthesis of Propargylic Dioxolanones
Propargylic dioxolanones 3 were easily prepared from en-
ynes 1 in two steps. The latter are either commercially avail-
able or easily obtained by Sonogashira coupling between a
terminal alkyne and a vinyl halide or other methods.[20] The
diol intermediates 2 were prepared in good yields by subse-
quent dihydroxylation of enynes 1. Several conditions are
compatible in this step. The Sharpless asymmetric dihydrox-
ylation[21] was applied for the synthesis of enantiomerically
enriched diols, or quinuclidine can be used as ligand for
osmium in racemic approaches. Ruthenium-catalyzed dihy-
droxylation also provided efficient access to diols when aro-
matic enynes are involved.[22] The diols 2 when treated with
triphosgene in the presence of pyridine allow convenient in-
stallation of the carbonyl group. These reactions all pro-
ceeded efficiently and gave the propargylic dioxolanones in
good yields (Scheme 4).
Figure 1. Byproducts of the SN2Ј substitution of propargylic diox-
olanones.
Fortunately, all of these back-ground reactions were sup-
pressed after optimizing the reaction conditions. Selected
results are shown in Table 1. Propargylic dioxolanone 3a
was chosen as a model substrate for system optimization
while RMgX (R = Me, Et, iPr) were used as the nucleo-
philes.
A number of copper salts were tested (9 examples), of
which a selection is shown (Entries 1–6). The reactivity of
the catalyst varied with the copper source. Both CuBr·SMe2
(Entry 4) and Cu(OTf)2 (Entry 5) gave very low conversion.
Surprisingly, CuCN (Entry 1), which was used in the stoi-
chiometric trial reaction (Scheme 5), showed only moderate
activity. Among all the copper salts tested, [Cu(MeCN)4]-
[BF4] showed superior reactivity and provided Ͼ99% con-
version in only 2 h. The salt [Cu(MeCN)4][BF4] is attractive
as it is readily available, easy to handle and air stable.[19]
Further studies also revealed that the reaction is ligand ac-
celerated, the reactivity of the catalyst decreased signifi-
cantly in the absence of a P-ligand (Entry 2 vs. Entry 3).
Therefore, a range of phosphorus ligands were tested in the
reaction (17 examples). The results showed that the ligand
choice has a dramatic influence on the chemoselectivity of
the reaction (Entries 6–11). When JohnPhos [2-(di-tert-bu-
tylphosphanyl)biphenyl] was used as ligand (Entry 9), only
12% of the desired SN2Ј product was obtained, but 61% of
the enyne byproduct formed by electron transfer. The ini-
tially used ligand P(nBu)3 gave the desired substitution
product together with 27% of diol byproduct (Entry 6). The
other phosphane ligand PCy3 (Entry 8) showed similar
chemoselectivity as P(nBu)3. However, phosphite ligands
(Entries 10–11) gave excellent chemoselectivity, only the
SN2Ј/SN2 products were observed. Moreover, P(OBu)3 (En-
try 11) gave the best regioselectivity between SN2Ј and SN2
adduct, and was used as ligand in the following studies. The
investigation of the solvent effect in the reaction was then
carried out. The catalyst showed no reactivity in the pres-
ence of THF (Entry 12), which might be due to the strong
coordinating properties of the THF. Another interesting
observation was the success of CH2Cl2 when used as solvent
(Entries 13, 16, 17), which is in agreement with the results
obtained with copper catalyzed conjugate addition.[23] In
Scheme 4. Synthesis of propargylic dioxolanones.
Studies on the SN2Ј Substitution of Propargylic
Dioxolanones
To show the viability of propargylic dioxolanones 3 for
the formation of α-hydroxyallenes the SN2Ј reaction was
first carried out following a literature procedure,[1c] using a
stoichiometric amount of cuprate (Scheme 5). Satisfyingly,
the corresponding allene 4 was isolated in 90% yield.
Scheme 5. SN2Ј substitution of 3a with stoichiometric cuprate.
Eur. J. Org. Chem. 2009, 2836–2844
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2837

X. Tang, S. Woodward, N. Krause
FULL PAPER
Table 1. Optimization of the SN2Ј substitution of propargylic dioxolanone 3a.
Entry
Cu salt[a]
R
Ligand
Solvent
% Conversion[b] SN2Ј/SN2; diol/enyne[c]
1
2
3
4
5
6
7
8
CuCN
CuSCN
CuSCN
CuBr·SMe2
Cu(OTf)2
[Cu(MeCN)4][BF4]
[Cu(MeCN)4][BF4]
[Cu(MeCN)4][BF4]
Me
Me
Me
Me
Me
Me
Me
Me
P(nBu)3
P(nBu)3
–
P(nBu)3
P(nBu)3
P(nBu)3
O=PBu3
PCy3
Et2O
Et2O
Et2O
Et2O
Et2O
Et2O
Et2O
Et2O
46
61
20
27
n.d.[d]
n.d.
n.d.
n.d.
8
n.d.
100
100
100
30:43; 27/–
20:49; 18/13
28:37; 14/11
9
[Cu(MeCN)4][BF4]
Me
Et2O
100
12:27; –/61
10
11
12
13
14
15
16
17
[Cu(MeCN)4][BF4]
[Cu(MeCN)4][BF4]
[Cu(MeCN)4][BF4]
[Cu(MeCN)4][BF4]
[Cu(MeCN)4][BF4]
[Cu(MeCN)4][BF4]
[Cu(MeCN)4][BF4]
[Cu(MeCN)4][BF4]
Me
Me
Me
Me
Et
Et
Et
P(OEt)3
P(OBu)3
P(OBu)3
P(OBu)3
P(OBu)3
P(OBu)3
P(OBu)3
P(OBu)3
Et2O
Et2O
THF
CH2Cl2
Et2O
toluene
CH2Cl2
CH2Cl2
100
100
45:55; –/–
50:50; –/–
n.d.
59:41; –/–
80:20; –/–
86:14; –/–
90:10; –/–
100:0; –/–
Ͻ 10
100
80[e]
52[e]
80[e]
82[e]
iPr
1
[a] Ratio of 3a/RMgX/[Cu]/ligand = 1:2:0.1:0.2, solvent (3 mL), –10 °C, 2 h. [b] Conversion of 3a is based on H NMR analysis of the
1
crude product. [c] Ratio between the SN2Ј, SN2, diol and enyne product is based on H NMR analysis of the crude product. [d] n.d.: not
determined. [e] Isolated yield of allene.
comparison to use of Et2O, CH2Cl2 gave better regioselec- Grignard reagent, both aliphatic (Et, iPr, tBu) and aromatic
tivity between SN2Ј and SN2 substitution while identical re- (Ph) nucleophiles were successfully utilized in the reaction.
activity was maintained (Entries 11 vs. 13, 14 vs. 16). Most Functionalized Grignard reagents,[24] generated by halo-
importantly however, the studies of Table 1 showed that the gen–metal exchange between iPrMgCl and aromatic
regioselectivity between SN2Ј and SN2 mainly depends on iodides, also gave very promising results. The corresponding
the steric properties of the nucleophile (Entries 13–17). α-hydroxyallenes 13–14, 18–20 and 23, bearing function-
When the least sterically demanding nucleophile MeMgBr alized aryl groups, were isolated in moderate to good yields.
was used, a mixture of SN2Ј and SN2 products was obtained
A series of secondary α-hydroxyallenes 8–14 were also
in a 59:41 ratio (Entry 13). When the relatively larger nu- synthesized in excellent diastereoselectivity, where only one
cleophile EtMgBr was employed in the reaction (Entry 16), diastereoisomer was observed. Indeed, in most of the cop-
good regioselectivity was observed, with a 90:10 ratio in per-mediated SN2Ј substitution of propargylic electrophiles,
favor of the desired SN2Ј products. When the steric demand the corresponding allenes are formed by an overall anti-
of the nucleophile was increased further to iPrMgCl (Entry substitution.[25] In order to determine if our results are in
17), only the desired SN2Ј product was obtained.
agreement with the literature observation, we carried out a
Through the above study of the reaction conditions, a gold-catalyzed cycloisomerization on allene 9 to form the
highly efficient copper catalyst for the SN2Ј substitution of dihydrofuran 24 (Scheme 6).[17] NOE experiments of the di-
propargylic dioxolanone with Grignard reagent was found. hydrofuran 24 revealed a cis configuration between H and
The desired α-hydroxyallene was obtained in excellent yield tBu group, therefore confirming the anti-selectivity of the
leaving only for the reaction to be generalized.
SN2Ј substitution.
The optimized reaction conditions were then applied to
Pleasingly, the new copper-catalyzed SN2Ј substitution of
a small library of propargylic dioxolanones with a collec- propargylic dioxolanones showed a great versatility for the
tion of Grignard reagents (Table 2). Both aromatic (R1 = synthesis of α-hydroxyallenes. A range of primary and sec-
Ph) and aliphatic [R1 = Me, Et, -(CH2)4-] propargylic diox- ondary α-hydroxyallenes bearing various functional groups
olanones showed similar reactivity and gave the corre- were synthesized in good to excellent yields regard to this
sponding α-hydroxyallene in good to excellent yields (all- protocol.
enes 5–20). The terminal propargylic dioxolanone 3e (R1 =
In addition, we studied the potential of applying this
H) gave the α-hydroxyallenes 21–23 in relatively lower method to the synthesis of enantiomerically enriched all-
yields, due to a competing deprotonation of terminal alkyne enes. The enantiomerically enriched propargylic dioxol-
in the presence of the Grignard reagent. Regarding to the anone (S)-3a was synthesized by the Sharpless asymmetric
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Eur. J. Org. Chem. 2009, 2836–2844

Hydroxyallenes from Propargylic Dioxolanones
Table 2. Scope of the copper-catalyzed SN2Ј substitution of propargylic dioxolanones.
Allene
Substrate
Grignard
R1
R2
R3
R4
% Yield[a]
5
3a
3a
3a
3b
3b
3c
3c
3c
3c
3c
3d
3d
3d
3d
3d
3d
3e
3e
3e
EtMgBr
iPrMgCl
tBuMgCl
iPrMgCl
iBuMgCl
iPrMgCl
iBuMgCl
PhMgCl
2-FC6H4MgCl
4-MeO2CC6H4MgCl
iPrMgCl
iBuMgCl
PhMgCl
2-FC6H4MgCl
3-MeOC6H4MgCl
4-MeO2CC6H4MgCl
tBuMgCl
PhMgCl
2-FC6H4MgCl
Ph
Ph
Ph
Ph
Ph
Me
Me
Me
Me
Me
Et
Et
Et
Et
Et
Et
H
H
H
H
H
H
H
H
H
H
H
Me
Me
Et
iPr
tBu
iPr
tBu
iPr
tBu
Ph
80[b]
82
78
89
92
78
81
83
76
62
90
90
88
85
57
61
62
58
39
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
–(CH2)4–
–(CH2)4–
–(CH2)4–
–(CH2)4–
–(CH2)4–
2-FC6H4
4-MeO2CC6H4
iPr
tBu
Ph
2-FC6H4
3-MeOC6H4
4-MeO2CC6H4
tBu
Ph
2-FC6H4
Me
Me
Me
Me
Me
Me
Me
Me
Me
H
H
H
H
H
H
H
H
H
1
[a] Isolated yield. [b] SN2Ј/SN2: 90:10, based on H NMR of the purified product.
a highly anti-selective pathway. The application of this
method to the synthesis of natural products is currently un-
der progress.
Experimental Section
Scheme 6. Gold-catalyzed cycloisomerization of allene 9.
General: Infrared spectra were recorded using Perkin–Elmer 983 G
infrared, Perkin–Elmer 882 infrared spectrophotometers or a
Bruker IFS 66 spectrometer. Proton and 13C NMR spectra were
recorded with Bruker (AM400, AV400 or DRX 400) spectrometers
using CHCl3 (δ = 7.27 ppm) tetramethylsilane (δ = 0.00 ppm) as
standard; J values are given in Hz. All spectra were recorded at
ambient temperature unless otherwise noted. Mass spectra were
obtained with a Finnigan-MAT 1020 or Autospec VG (electron
impact ionisation, EI), Finnigan-QMS (electrospray ionisation,
ESI), VG-ZAB, or Finnigan MAT 8200 (EI, 70 eV). All reactions
involving air sensitive materials were carried out under argon using
standard Schlenk techniques. Reaction solvents were distilled under
argon from appropriate agent immediately prior to use. Data of
known compound is in agreement with the literature report.
dihydroxylation. The copper-catalyzed SN2Ј substitution
was then performed, and the desired enantiomerically en-
riched allene (S)-5 was isolated with complete chirality
transfer (Scheme 7). However, the propargylic dioxolanone
(S)-3a only had 58% enantiomeric excess due to unfortu-
nately low enantioselectivity in the dihydroxylation step.
(But-3-en-1-ynyl)benzene (1a):[26] A mixture of Pd(PPh3)4 (55 mg,
0.048 mmol, 0.32 mol-%) and CuI (57 mg, 0.3 mmol, 2 mol-%)
were dissolved in Et2NH (7.5 mL) under argon. After cooling to
–10 °C, phenylacetylene (1.6 mL, 15 mmol) and vinyl bromide
(20 mL, 1.0  in THF, 20 mmol) were added. The reaction mixture
was kept stirring at room temp. for 20 h. The reaction mixture was
poured on H2O, and extracted into Et2O. The organic phase was
washed with HCl (1 ), dried with MgSO4 and concentrated to
give crude compound. The crude was purified by column
chromatography (light petroleum) over silica gel to give pure prod-
Scheme 7. Synthesis of enantiomerically enriched allene (S)-5.
Conclusions
A new copper-catalyzed SN2Ј substitution of propargylic
dioxolanones has been developed. This protocol provides
an efficient and versatile access to α-hydroxyallenes. It also
shows potential in the synthesis of enantiomerically en-
riched allenes. A variety of primary and secondary α-hy-
1
uct 1a as colorless oil (1.72 g, 89%). H NMR (400 MHz, CDCl3,
25 °C, TMS): δ = 7.49–7.45 (m, 2 H), 7.36–7.32 (m, 3 H), 6.09–
droxyallenes were obtained with good to excellent yields via 6.01 (dd, J = 11.2 and 17.6 Hz, 1 H), 5.79 (d, J = 17.6 Hz, 1 H),
Eur. J. Org. Chem. 2009, 2836–2844
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2839

X. Tang, S. Woodward, N. Krause
5.59 (d, J = 11.2 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3, 690 cm–1. HRMS: [M]+ C11H12O2, theoretical mass 176.0832;
FULL PAPER
25 °C, TMS): δ = 131.6, 128.3, 126.9, 123.1, 117.2, 89.9, 88.1 ppm.
found 176.0824.
IR (CHCl solution): ν = 2925, 2875, 2223, 1756, 1600 cm–1.
˜
1-(Prop-1-ynyl)cyclohexane-1,2-diol (2c):[30] Compound 1c (1.20 g,
10 mmol) and K3Fe(CN)6 (9.8 g), K2CO3 (4.1 g), quinuclidine
(178 mg), K2OsO2(OH)4 (180 mg), methanesulfonamide (928 mg)
were suspended in tBuOH/H2O (50 mL each) and stirred at room
temp. for 2 d. Na2SO3 (15 g) was added, the mixture was extracted
with EtOAc, the combined organic layers were dried with MgSO4
and concentrated under reduced pressure. The crude was purified
by flash column chromatography (Et2O/light petroleum: 9:1) over
silica gel afforded pure compound 2c (0.61 g, 40% yield) as yellow
3
(Z)-(Pent-3-en-1-ynyl)benzene
(1b):[27]
Pd(PPh3)4
(55 mg,
0.048 mmol, 0.32 mol-%), CuI (57 mg, 0.3 mmol, 2 mol-%), phen-
ylacetylene (1.6 mL, 15 mmol) and 1-bromoprop-1-ene (1.7 mL,
20 mmol, E/Z mixture) were treated the same procedure as 1a. Af-
ter purification, pure product 1b was obtained as yellow oil (1.93 g,
1
91%, Z/E: 77:23). H NMR (400 MHz, CDCl3, 25 °C, TMS): δ =
7.46–7.40 (m, 2 H), 7.31–7.28 (m, 3 H), 6.09–5.99 (m, 1 H), 5.70
(d, J = 10.8 Hz, 1 H), 1.96 (d, J = 6.8 Hz, 3 H) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C, TMS): δ = 139.6, 131.2, 128.1, 127.9,
1
oil. H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 3.65–3.63 (m,
1 H), 2.42–2.33 (m, 1 H), 2.33–2.25 (m, 1 H), 2.11–1.91 (m, 2 H),
1.83 (s, 3 H), 1.78–1.69 (m, 1 H), 1.68–1.50 (m, 5 H) ppm. 13C
NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 81.6, 80.6, 74.2, 70.1,
123.5, 109.9, 93.8, 86.1, 16.0 ppm. IR (KBr): ν = 3468, 3027, 2912,
˜
1714, 1489, 1384, 755 cm–1.
1-(Prop-1-ynyl)cyclohexene (1c):[28] 1-Ethynylcyclohexene (1.18 mL,
10 mmol) was dissolved in THF (10 mL) under argon. The solution
was cooled to – 78 °C. nBuLi (8 mL, 2.5  in hexane, 20 mmol)
was added, the mixture was stirred for 2 h while allowing the tem-
perature to raise. MeI (1.24 mL, 20 mmol) was then added. The
reaction mixture was kept stirring overnight while warm to room
temp. The reaction mixture was quenched with NH4Cl (saturated
solution), and extracted with Et2O. The organic phase was washed
with brine, dried with MgSO4 and concentrated to give crude com-
pound. The crude was purified by column chromatography (cyclo-
hexane) over silica gel to give pure product 1c as yellow oil (0.98 g,
35.6, 28.3, 21.9, 21.0, 3.5 ppm. IR (KBr): ν = 3398, 2936, 2359,
˜
1445, 1064, 998 cm–1.
2-Methylhex-3-yne-1,2-diol (2d): 2-Methyl-1-hexen-3-yne (1.24 mL,
10 mmol) and K3Fe(CN)6 (9.8 g), K2CO3 (4.1 g), quinuclidine
(178 mg), K2OsO2(OH)4 (180 mg) and methanesulfonamide
(928 mg) were treated the same procedure as 2c. After purification
2d (900 mg, 70%) was obtained as colourless oil. 1H NMR
(400 MHz, CDCl3, 25 °C, TMS): δ = 3.64 (d, J = 11.2 Hz, 1 H),
3.49 (d, J = 11.2 Hz, 1 H), 2.72 (br., 1 H, OH), 2.25 (br., 1 H, OH),
2.26–2.20 (q, J = 7.6 Hz, 2 H), 1.45 (s, 3 H), 1.17 (t, J = 7.6 Hz, 3
H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 86.6, 80.9,
1
82%). H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 5.99 (br. s,
70.9, 68.6, 25.6, 13.8, 12.3 ppm. IR (CHCl3 solution): ν = 3585,
˜
1 H), 2.12–2.02 (m, 4 H), 1.93 (s, 3 H), 1.65–1.52 (m, 4 H) ppm.
2981, 2927, 2878, 2360, 1456, 1378, 1319, 1049, 975 cm–1. HRMS:
13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 133.1, 120.8, 82.6,
[M – CH2OH]+ C6H9O, theoretical mass 97.0648; found 97.0651.
81.4, 29.4, 25.4, 22.3, 21.5, 4.0 ppm. IR (KBr): ν = 2928, 2857,
˜
2360, 2341, 1436, 1384 cm–1.
2-Methylbut-3-yne-1,2-diol (2e): 2-Methylbut-1-en-3-yne (0.93 mL,
10 mmol) and K3Fe(CN)6 (9.8 g), K2CO3 (4.1 g), quinuclidine
(178 mg), K2OsO2(OH)4 (180 mg) and methyanesulfonamide
(928 mg) were treated the same procedure as 2c. After purification
2e (650 mg, 65%) was obtained as yellow oil. 1H NMR (400 MHz,
CDCl3, 25 °C, TMS): δ = 3.69 (d, J = 8.4 Hz, 1 H), 3.55 (d, J =
8.4 Hz, 1 H), 2.70 (br., 1 H, OH), 2.50 (s, 1 H), 2.15–2.09 (br., 1
H, OH), 1.51 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C,
TMS): δ = 85.5, 72.5, 70.6, 68.4, 25.1 ppm. IR (CHCl3 solution):
4-Phenylbut-3-yne-1,2-diol (2a): To a flask was added NaIO4
(1.28 g, 6 mmol), H2O (3 mL) and H2SO4 (0.8 mL, 0.8 mmol, 1 ).
After all the solids were dissolved the solution was cooled to 0 °C.
RuCl3 (0.2 mL, 0.02 mmol, 0.1  in H2O) was added and the mix-
ture was stirred until the color turned bright yellow. Ethyl acetate
(12 mL) was added, followed by acetonitrile (12 mL) after 5 min.
After further 5 min, compound 1a (4 mmol, 512 mg) was added in
one portion and the resulting slurry was stirred until all starting
material was consumed. The mixture was poured onto NaHCO3
(15 mL, satd.) and Na2S2O3 (20 mL, satd.) solution. The mixture
was extracted with EtOAc, the combined organic phase was dried
with MgSO4 and concentrated to give crude compound. The crude
was purified by flash column chromatography (Et2O/light petro-
leum: 9:1) over silica gel to give pure product 2a (528 mg, 81%
ν = 3586, 3304, 2986, 2935, 2876, 2112, 1602, 1455, 1380, 1352,
˜
1321, 1082, 1049, 976, 948, 886, 643 cm–1.
General Procedure for the Formation of Dioxolanones: To diol
(4.81 mmol) in CH2Cl2 (14 mL) in an argon flashed flask in an
ice bath was added pyridine (24 mmol). Solution of triphosgene
(5.29 mmol) in CH2Cl2 was added and the reaction was allowed to
stir for 10 min when determined complete by TLC. The reaction
was diluted with Et2O. The crude mixture, including salts, was
washed vigorously with a CuSO4 (satd.) solution until all salts dis-
solved. The layers were then separated and the organic layer was
washed with brine. After separation, the organic layer was dried
with MgSO4 and concentrated. The crude mixture was then puri-
fied by flash column chromatography over silica gel to give pure
product.
1
yield) as yellow oil. H NMR (400 MHz, CDCl3, 25 °C, TMS): δ
= 7.44 (m, 2 H), 7.36–7.29 (m, 3 H), 4.73 (dd, J = 6.6 and 3.8 Hz,
1 H), 3.88–3.79 (m, 2 H), 3.07 (br., 1 H, OH), 2.74 (br., 1 H, OH)
ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 131.8, 128.4,
128.3, 122.1, 86.5, 86.2, 66.6, 63.8 ppm. IR (CHCl solution): ν =
˜
3
3606, 2932, 2223, 1600, 1490, 1373, 1069, 991, 916, 863 cm–1.
HRMS: [M]+ C10H10O2, theoretical mass 162.0681; found
162.0684.
5-Phenylpent-4-yne-2,3-diol (2b):[29] Compound 1b (1.42 g, 4-(Phenylethynyl)-1,3-dioxolan-2-one (3a): Compound 2a (890 mg,
10 mmol), NaIO4 (3.2 g, 15 mmol), RuCl3 (0.5 mL, 0.1  in H2O), 5.5 mmol), triphosgene (2 g, 6.6 mmol) and pyridine (2.23 mL,
H2SO4 (2 mL, 1 ) and NaOAc/MeCN/H2O (30 mL:30 mL/
7.5 mL) were treated the same procedure as 2a. After purification,
27 mmol) were treated according to the general procedure. After
purification, compound 3a (940 mg, 91% yield) was obtained as
yellow oil. 1H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 7.46–
compound 2b (1.12 g, 64% yield, dr = 77:23) was obtained as yel-
1
low oil. H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 7.47–7.44 7.44 (m, 2 H), 7.40–7.31 (m, 3 H), 5.53 (dd, J = 8.2 and 6.9 Hz, 1
(m, 2 H), 7.35–7.31 (m, 3 H), 4.54 (d, J = 3.6 Hz, 1 H), 4.01–3.95 H), 4.69 (t, J = 8.2 Hz, 1 H), 4.48 (dd, J = 8.2 and 6.9 Hz, 1 H)
(m, 1 H), 1.35 (d, J = 6.4 Hz, 3 H) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C, TMS): δ = 131.7, 128.6, 128.2, 122.0, 86.8, 86.0,
ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 153.9, 131.9,
129.7, 128.5, 120.6, 89.8, 81.7, 69.7, 66.6 ppm. IR (CHCl3 solu-
70.2, 67.5, 18.3 ppm. IR (KBr): ν = 3317, 1490, 1384, 1083, 755,
tion): ν = 2922, 2238, 1818, 1599, 1490, 1386, 1297, 1149, 1070,
˜
˜
2840
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 2836–2844

Hydroxyallenes from Propargylic Dioxolanones
997 cm–1. HRMS: [M + Na+] C11H8NaO3, theoretical mass was then added, and the reaction was kept at –10 °C for 2 h. The
211.0371; found 211.0368.
reaction mixture was quenched with NH4Cl saturated solution and
the crude mixture was extracted with Et2O. The combined organic
phase was washed with H2O2 (3%) and brine, dried with MgSO4
and concentrated. The crude was purified by flash column
chromatography over silica gel to give pure product.
4-(But-1-ynyl)-4-methyl-1,3-dioxolan-2-one (3b): Compound 2b
(1.05 g, 6 mmol), triphosgene (2.0 g, 6.6 mmol) and pyridine
(2.4 mL, 30 mmol) were treated according to the general procedure.
After purification, compound 3b (803 mg, 66% yield, only one dia-
stereomer) was obtained as yellow oil. 1H NMR (400 MHz, CDCl3,
25 °C, TMS): δ = 7.48–7.46 (m, 3 H), 7.40–7.33 (m, 2 H), 5.04 (d,
J = 7.1 Hz, 1 H), 4.83–4.76 (m, 1 H), 1.59 (d, J = 6.3 Hz, 3 H)
ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 153.4, 131.9,
General Procedure B of SN2Ј Substitution. Using Functionalized
Grignard Reagent: The iodobenzene (2.5 mmol) was dissolved in
THF (1 mL) in a dry argon-flashed Schlenk flask and cooled to
–40 °C, iPrMgCl (2.5 mmol) was then added. After 1 h at –40 °C,
the Grignard reagent was added to the freshly prepared solution of
[Cu(MeCN)4][BF4] (0.1 mmol, 10 mol-%) and (BuO)3P (0.2 mmol,
20 mol-%) in CH2Cl2 (2 mL) at –10 °C. After stirring for 30 min at
–10 °C, a solution of the dioxolanone (1 mmol) in CH2Cl2 (1 mL)
was added, and the reaction was kept at –10 °C for 2 h. The reac-
tion mixture was quenched with NH4Cl saturated solution and the
crude mixture was extracted with Et2O. The combined organic
phase was washed with H2O2 (3%) and brine, dried with MgSO4
and concentrated. The crude was purified by flash column
chromatography over silica gel to give pure product.
129.6, 128.4, 120.6, 89.9, 81.0, 79.2, 72.8, 18.5 ppm. IR (KBr): ν =
˜
3441, 2233, 1802, 1384, 1354, 1179, 1065, 1022, 758 cm–1. HRMS:
[M]+ C12H10O3, theoretical mass 202.0624; found 202.0615.
3a-(Prop-1-ynyl)hexahydrobenzo[d][1,3]dioxol-2-one (3c): Com-
pound 2c (1.6 g, 10 mmol), triphosgene (3.3 g, 11 mmol) and pyr-
idine (4.0 mL, 50 mmol) were treated according to the general pro-
cedure. After purification, compound 3c (1.31 g, 72% yield) was
1
obtained as yellow oil. H NMR (400 MHz, CDCl3, 25 °C, TMS):
δ = 4.57 (t, J = 3.8 Hz, 1 H), 2.21–2.02 (m, 2 H), 1.88 (s, 3 H),
1.87–1.74 (m, 2 H), 1.73–1.32 (m, 4 H) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C, TMS): δ = 154.0, 85.5, 80.3, 78.1, 74.9, 34.3, 25.3,
4-Phenylhexa-2,3-dien-1-ol (5): Compound 3a (188 mg, 1 mmol),
[Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-%), (BuO)3P
(54 µL, 0.2 mmol, 20 mol-%) and EtMgBr (3.0  in Et2O, 0.67 mL,
2 mmol) were treated according to the general procedure A. After
purification, compound 5 (140 mg, 80% yield) was obtained as yel-
20.1, 18.7, 3.7 ppm. IR (KBr): ν = 2945, 2866, 2253, 1806, 1297,
˜
1228, 1196, 1015 cm–1. HRMS: [M]+ C10H12O3, theoretical mass
180.0781; found 180.0784.
4-(But-1-ynyl)-4-methyl-1,3-dioxolan-2-one (3d): Compound 2d
(730 mg, 5.7 mmol), triphosgene (1.90 g, 6.3 mmol) and pyridine
(2.3 mL, 28.5 mmol) were treated according to the general pro-
cedure. After purification, compound 3d (812 mg, 92% yield) was
1
low oil. H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 7.43 (d, J
= 7.4 Hz, 2 H), 7.35 (t, J = 7.4 Hz, 2 H), 7.24 (t, J = 7.4 Hz, 1 H),
5.82–5.78 (m, 1 H), 4.27 (t, J = 5.1 Hz, 2 H), 2.52–2.48 (m, 2 H),
1.18 (t, J = 7.3 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C,
TMS): δ = 202.5, 136.4, 128.4, 126.9, 126.0, 110.7, 95.9, 60.7, 22.9,
1
obtained as yellow oil. H NMR (400 MHz, CDCl3, 25 °C, TMS):
δ = 4.44 (d, J = 8.2 Hz, 1 H), 4.18 (d, J = 8.2 Hz, 1 H), 2.22 (q, J
= 7.5 Hz, 2 H), 1.70 (s, 3 H), 1.12 (t, J = 7.5 Hz, 3 H) ppm. 13C
NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 153.8, 90.7, 76.5, 76.0,
12.6 ppm. IR (CHCl solution): ν = 3610, 2970, 2932, 2876, 1946,
˜
3
1741, 1598, 1493, 1456, 1379, 1141, 1078, 994, 912 cm–1. HRMS:
[M]+ C12H14O, theoretical mass 174.1045; found 174.1040. HPLC:
Daicel Chiralpak OJ-H, iPrOH/hexanes, 90:10, UV: 254 nm, flow
rate: 1.0 mLmin–1. TS = 21.4 min, TR = 25.7 min.
75.6, 26.9, 13.1, 12.2 ppm. IR (KBr): ν = 2983, 2253, 1809, 1385,
˜
1237, 1060 cm–1. HRMS: [M]+ C8H10O3, theoretical mass
154.0624; found 154.0617.
5-Methyl-4-phenylhexa-2,3-dien-1-ol (6): Compound 3a (188 mg,
1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-%),
(BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and iPrMgCl (1.0  in Et2O,
2 mL, 2 mmol) were treated according to the general procedure A.
After purification, compound 6 (154 mg, 82% yield) was obtained
Ethynyl-4-methyl-1,3-dioxolan-2-one (3e): Compound 2e (440 mg,
4.4 mmol), triphosgene (1.47 g, 4.8 mmol) and pyridine (1.82 mL,
22 mmol) were treated according to the general procedure. After
purification, compound 3e (490 mg, 88% yield) was obtained as
1
1
yellow oil. H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 4.53 (d,
as yellow oil. H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 7.39
J = 8.4 Hz, 1 H), 4.25 (d, J = 8.4 Hz, 1 H), 2.76 (s, 1 H), 1.78 (s,
(d, J = 7.3 Hz, 2 H), 7.32 (t, J = 7.3 Hz, 2 H), 7.22 (t, J = 7.3 Hz,
1 H), 5.76 (dt, J = 5.6 and 2.3 Hz, 1 H), 4.23 (t, J = 5.6 Hz, 2 H),
2.90–2.82 (m, 1 H), 1.14 (t, J = 6.9 Hz, 6 H) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C, TMS): δ = 201.8, 136.3, 128.4, 126.9,
3 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 153.3,
125.7, 80.3, 76.3, 75.1, 26.3 ppm. IR (KBr): ν = 3289, 1802, 1387,
˜
1236, 1099, 1061 cm–1. HRMS: [M]+ C6H6O3, theoretical mass
126.0317; found 126.0324.
126.6, 116.3, 96.2, 60.9, 28.1, 22.6, 22.1 ppm. IR (KBr): ν = 3335,
˜
2963, 2870, 2360, 1384, 1011, 760, 694 cm–1. HRMS: [M]+
C13H16O, theoretical mass 188.1201; found 188.1200.
Preparation of [Cu(MeCN)4][BF4]: A mixture of Cu2O (1 g), MeCN
(25 mL) and HBF4 (5 mL, 47% solution) were added to a flask
fitted with a reflux condenser, and heated to 50–60 °C until all the
solids dissolve. The hot solution was filtered and the filtrate was
left to cool to room temperature then 4 °C. A large crop of colorless
crystal was formed, filtrate the crystal and wash with dry Et2O gave
[Cu(MeCN)4][BF4] salt, which can be stored under air for months.
The decomposition can be simple detected by color change from
colorless to blue.
5,5-Dimethyl-4-phenylhexa-2,3-dien-1-ol (7): Compound 3a
(188 mg, 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-
%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and tBuMgCl (2.0  in
Et2O, 1 mL, 2 mmol) were treated according to the general pro-
cedure A. After purification, compound 7 (158 mg, 78% yield) was
1
obtained as yellow oil. H NMR (400 MHz, CDCl3, 25 °C, TMS):
δ = 7.31–7.24 (m, 3 H), 7.23–7.19 (m, 2 H), 5.41 (t, J = 5.8 Hz, 1
H), 4.11 (d, J = 5.8 Hz, 2 H), 1.12 (s, 9 H) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C, TMS): δ = 200.4, 137.2, 129.2, 127.7,
General Procedure A of SN2Ј Substitution. Using Commercial Avail-
able Grignard Reagent: To a dry argon flashed Schlenk was added
[Cu(MeCN)4][BF4] (0.1 mmol, 10 mol-%), (BuO)3P (0.2 mmol,
20 mol-%) and CH2Cl2 (2 mL), the mixture was stirred at room
temp. for 1 h. After cooling the reaction to – 10 °C, the Grignard
reagent (2 mmol) was added, the reaction was stirred for 30 min
at –10 °C, a solution of the dioxolanone (1 mmol) in CH2Cl2 (1 mL)
126.7, 118.7, 92.3, 61.1, 34.2, 29.7 ppm. IR (KBr): ν = 3344, 2963,
˜
2866, 1441, 1381, 1012, 758, 700 cm–1. HRMS: [M]+ C14H18O,
theoretical mass 202.1352; found 202.1342.
6-Methyl-5-phenylhepta-3,4-dien-2-ol (8): Compound 3b (202 mg,
1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-%),
Eur. J. Org. Chem. 2009, 2836–2844
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2841

X. Tang, S. Woodward, N. Krause
FULL PAPER
(BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and iPrMgCl (2.0  in Et2O,
1 mL, 2 mmol) were treated according to the general procedure A.
After purification, compound 8 (192 mg, 89% yield) was obtained
29.6, 26.9, 23.5, 17.9 ppm. IR (KBr): ν = 3217, 2938, 1445, 1075,
˜
995, 970, 761, 694 cm–1. HRMS: [M]+ C15H18O, theoretical mass
214.1352; found 214.1350.
1
as yellow oil. H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 7.40
2-[2-(2-Fluorophenyl)prop-1-enylidene]cyclohexanol (13): Com-
pound 3c (180 mg, 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg,
0.1 mmol, 10 mol-%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and
iPrMgBr (2.0  in Et2O, 1.25 mL, 2.5 mmol) and 1-fluoro-2-iodo-
benzene (0.29 mL, 2.5 mmol) were treated according to the general
procedure B. After purification, compound 13 (176 mg, 76% yield)
was obtained as white solid; m.p. 76 °C. 1H NMR (400 MHz,
CDCl3, 25 °C, TMS): δ = 7.27 (dt, J = 7.7 and 1.7 Hz, 1 H), 7.19–
7.13 (m, 1 H), 7.07 (dt, J = 7.7 and 1.2 Hz, 1 H), 7.02–6.96 (m, 1
H), 4.11–4.06 (m, 1 H), 2.46–2.41 (m, 1 H), 2.12 (d, J = 1.4 Hz, 3
H), 2.09–2.04 (m, 2 H), 1.86–1.65 (m, 3 H), 1.46–1.37 (m, 3 H)
ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 196.8, 161.2,
158.8, 128.7, 128.0, 123.8, 115.7, 107.4, 99.0, 69.2, 35.5, 29.6, 26.6,
(d, J = 7.9 Hz, 2 H), 7.32 (t, J = 7.7 Hz, 2 H), 7.22 (t, J = 7.3 Hz,
1 H), 5.72–5.71 (m, 1 H), 4.45 (br. s, 1 H), 2.90–2.82 (m, 1 H), 1.37
(d, J = 6.7 Hz, 3 H), 1.16 (d, J = 6.7 Hz, 3 H), 1.14 (d, J = 6.7 Hz,
3 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 200.4,
136.3, 128.4, 126.8, 126.4, 116.6, 101.3, 66.2, 28.0, 23.6, 22.6,
22.1 ppm. IR (KBr): ν = 3436, 2966, 2928, 1713, 1384, 1365, 1121,
˜
1077, 761, 694 cm–1. HRMS: [M]+ C14H18O, theoretical mass
202.1352; found 202.1345.
6,6-Dimethyl-5-phenylhepta-3,4-dien-2-ol (9): Compound 3b
(202 mg, 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-
%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and tBuMgBr (2.0  in
Et2O, 1 mL, 2 mmol) were treated according to the general pro-
cedure A. After purification, compound 9 (199 mg, 92% yield) was
23.5, 19.9 ppm. IR (KBr): ν = 3397, 2933, 1490, 1446, 1213, 997,
˜
756 cm–1. HRMS: [M]+ C15H17OF, theoretical mass 232.1258;
found 232.1258.
1
obtained as white solid; m.p. 42 °C. H NMR (400 MHz, CDCl3,
25 °C, TMS): δ = 7.33–7.27 (m, 3 H), 7.25–7.22 (m, 2 H), 5.40 (d,
J = 5.2 Hz, 1 H), 4.39–4.30 (m, 1 H), 1.32 (d, J = 6.3 Hz, 3 H),
1.14 (s, 9 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ =
199.0, 137.2, 129.2, 127.7, 126.7, 119.1, 97.3, 65.9, 34.3, 29.7,
Methyl
4-[1-(2-Hydroxycyclohexylidene)prop-1-en-2-yl]benzoate
(14): Compound 3c (180 mg, 1 mmol), [Cu(MeCN)4][BF4]
(31.4 mg, 0.1 mmol, 10 mol-%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-
%) and iPrMgBr (2.0  in Et2O, 1.25 mL, 2.5 mmol) and methyl
4-iodobenzoate (654 mg, 2.5 mmol) were treated according to the
general procedure B. After purification, compound 14 (168 mg,
62% yield) was obtained as white solid; m.p. 86 °C. 1H NMR
(400 MHz, CDCl3, 25 °C, TMS): δ = 7.94 (d, J = 8.5 Hz, 2 H),
7.41 (d, J = 8.5 Hz, 2 H), 4.20–4.13 (m, 1 H), 3.88 (s, 3 H), 2.51–
2.43 (m, 1 H), 2.13 (s, 3 H), 2.13–2.05 (m, 2 H), 1.89–1.82 (m, 1 H),
1.81–1.72 (m, 2 H), 1.53–1.43 (m, 3 H) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C, TMS): δ = 196.4, 166.9, 142.5, 129.5, 128.0, 125.4,
110.1, 103.7, 69.3, 51.9, 36.1, 29.4, 26.8, 23.4, 17.7 ppm. IR (KBr):
23.1 ppm. IR (KBr): ν = 3348, 2966, 1442, 1361, 1075, 701 cm–1.
˜
HRMS: [M]+ C15H20O, theoretical mass 216.1509; found 216.1505.
2-(2,3-Dimethylbut-1-enylidene)cyclohexanol (10):[31] Compound 3c
(180 mg, 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-
%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and iPrMgBr (2.0  in
Et2O, 1 mL, 2 mmol) were treated according to the general pro-
cedure A. After purification, compound 10 (140 mg, 78% yield)
was obtained as white solid; m.p. 36 °C. 1H NMR (400 MHz,
CDCl3, 25 °C, TMS): δ = 3.96–3.90 (m, 1 H), 2.35–2.29 (m, 1 H),
2.14–2.07 (m, 1 H), 2.07–1.89 (m, 2 H), 1.85–1.75 (m, 2 H), 1.72
(s, 3 H), 1.69–1.61 (m, 1 H), 1.43–1.27 (m, 3 H), 0.98 (dd, J = 6.7
and 1.5 Hz, 6 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS):
δ = 190.2, 111.3, 108.0, 68.9, 36.2, 32.5, 30.1, 26.9, 23.7, 21.7,
ν = 3435, 2934, 1720, 1606, 1436, 1279, 1113, 773 cm–1. HRMS:
˜
[M]+ C17H20O3, theoretical mass 272.1407; found 272.1406.
4-Ethyl-2,5-dimethylhexa-2,3-dien-1-ol
(15):
Compound
3d
18.2 ppm. IR (KBr): ν = 3418, 2931, 2856, 2360, 1446, 1384, 1075,
˜
(154 mg, 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-
%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and iPrMgCl (2.0  in
Et2O, 1 mL, 2 mmol) were treated according to the general pro-
cedure A. After purification, compound 15 (138 mg, 90% yield)
was obtained as yellow oil. 1H NMR (400 MHz, CDCl3, 25 °C,
TMS): δ = 3.93 (s, 2 H), 2.16–2.06 (m, 1 H), 1.98 (q, J = 7.3 Hz, 2
H), 1.68 (s, 3 H), 0.98 (d, J = 6.7 Hz, 6 H), 0.94 (t, J = 7.3 Hz, 3
H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 193.7,
117.9, 103.5, 63.7, 31.5, 24.0, 22.1, 21.9, 15.9, 12.5 ppm. IR (KBr):
999 cm–1. HRMS: [M]+ C12H20O, theoretical mass 180.1509; found
180.1509.
2-(2,3,3-Trimethylbut-1-enylidene)cyclohexanol (11):[31] Compound
3c (180 mg, 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol,
10 mol-%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and tBuMgCl
(2.0  in Et2O, 1 mL, 2 mmol) were treated according to the gene-
ral procedure A. After purification, compound 11 (158 mg, 81%
yield) was obtained as white solid; m.p. 83 °C. 1H NMR (400 MHz,
CDCl3, 25 °C, TMS): δ = 3.97–3.90 (m, 1 H), 2.35–2.29 (m, 1 H),
2.05–1.90 (m, 2 H), 1.83–1.74 (m, 2 H), 1.71 (s, 3 H), 1.68–1.60 (m,
1 H), 1.39–1.27 (m, 3 H), 1.01 (s, 9 H) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C, TMS): δ = 190.5, 113.8, 107.0, 68.9, 36.0, 34.1, 29.9,
ν = 3436, 2962, 2931, 2870, 1713, 1461, 1384, 1013 cm–1. HRMS:
˜
[M]+ C10H8O, theoretical mass 154.1352; found 154.1350.
4-Ethyl-2,5,5-trimethylhexa-2,3-dien-1-ol (16): Compound 3d
(154 mg, 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-
%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and tBuMgCl (2.0  in
Et2O, 1 mL, 2 mmol) were treated according to the general pro-
cedure A. After purification, compound 16 (152 mg, 90% yield)
was obtained as yellow oil. 1H NMR (400 MHz, CDCl3, 25 °C,
TMS): δ = 3.96 (d, J = 5.6 Hz, 2 H), 2.00 (q, J = 7.3 Hz, 2 H),
1.70 (s, 3 H), 1.04 (s, 9 H), 0.94 (t, J = 7.3 Hz, 3 H) ppm. 13C
NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 193.9, 120.6, 103.1,
29.2, 26.8, 23.6, 15.7 ppm. IR (KBr): ν = 3232, 2930, 2360, 1433,
˜
1385, 1358, 1114, 993, 973 cm–1. HRMS: [M]+ C13H22O, theoretical
mass 194.1665; found 194.1669.
2-(2-Phenylprop-1-enylidene)cyclohexanol (12):[31] Compound 3c
(180 mg, 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-
%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and PhMgCl (1.8  in
THF, 1.1 mL, 2 mmol) were treated according to the general pro-
cedure A. After purification, compound 12 (177 mg, 83% yield)
was obtained as white solid; m.p. 101 °C. 1H NMR (400 MHz,
CDCl3, 25 °C, TMS): δ = 7.38 (d, J = 7.5 Hz, 2 H), 7.31 (t, J =
7.6 Hz, 2 H), 7.20 (d, J = 7.3 Hz, 1 H), 4.20–4.10 (m, 1 H), 2.50–
63.7, 34.1, 29.4, 20.3, 15.9, 12.8 ppm. IR (KBr): ν = 3342, 2963,
˜
2360, 2341, 1456, 1384, 1009 cm–1. HRMS: [M]+ C11H20O, theoret-
ical mass 168.1509; found 168.1511.
2-Methyl-4-phenylhexa-2,3-dien-1-ol (17): Compound 3d (154 mg,
2.43 (m, 1 H), 2.14 (s, 3 H), 2.13–2.05 (m, 2 H), 1.90–1.70 (m, 3 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-%),
H), 1.51–1.40 (m, 3 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, (BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and PhMgCl (1.8  in THF,
TMS): δ = 194.9, 137.5, 128.2, 126.6, 125.6, 109.7, 104.4, 69.3, 36.1,
2842
1.1 mL, 2 mmol) were treated according to the general procedure
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 2836–2844

Hydroxyallenes from Propargylic Dioxolanones
A. After purification, compound 17 (165 mg, 88% yield) was ob-
tained as yellow oil. H NMR (400 MHz, CDCl3, 25 °C, TMS): δ
3338, 2959, 1384, 1020, 970 cm–1. HRMS: [M]+ C9H16O, theoreti-
cal mass 140.1196; found 140.1195.
1
= 7.39 (d, J = 7.8 Hz, 2 H), 7.32 (t, J = 7.6 Hz, 2 H), 7.21 (t, J =
7.3 Hz, 1 H), 4.17–4.10 (d, 2 H), 2.47 (q, J = 7.3 Hz, 2 H), 1.85 (s,
3 H), 1.13 (t, J = 7.3 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3,
25 °C, TMS): δ = 199.3, 137.7, 128.7, 127.1, 126.4, 111.3, 105.2,
2-Methyl-4-phenylbuta-2,3-dien-1-ol (22): Compound 3e (126 mg,
1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-%),
(BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and PhMgBr (1.8  in THF,
1.1 mL, 2 mmol) were treated according to the general procedure
A. After purification, compound 22 (93 mg, 58% yield) was ob-
tained as yellow solid; m.p. 68 °C. 1H NMR (400 MHz, CDCl3,
25 °C, TMS): δ = 7.33–7.27 (m, 4 H), 7.23–7.18 (m, 1 H), 6.30–
6.26 (m, 1 H), 4.20–4.11 (m, 2 H), 1.86 (d, J = 2.8 Hz, 3 H) ppm.
13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 200.6, 134.6, 128.5,
64.5, 23.7, 16.0, 13.1 ppm. IR (KBr): ν = 3436, 2964, 2930, 1714,
˜
1384, 1222, 1012, 755, 694 cm–1. HRMS: [M]+ C13H16O, theoretical
mass 188.1196; found 188.1197.
4-(2-Fluorophenyl)-2-methylhexa-2,3-dien-1-ol (18): Compound 3d
(154 mg, 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-
%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-%), iPrMgCl (2.0  in Et2O, 126.9, 126.6, 104.7, 97.1, 63.7, 15.3 ppm. IR (KBr): ν = 3401, 2359,
˜
1.25 mL, 2.5 mmol) and 1-fluoro-2-iodobenzene (0.29 mL,
2.5 mmol) were treated according to the general procedure B. After
purification, compound 18 (175 mg, 85% yield) was obtained as
yellow oil. 1H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 7.28 (m,
1 H), 7.23–7.16 (m, 1 H), 7.09 (m, 1 H), 7.05–6.99 (m, 1 H), 4.09
(s, 2 H), 2.49–2.38 (m, 2 H), 1.79 (s, 3 H), 1.08 (t, J = 7.3 Hz, 3 H)
ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 199.7, 161.1,
158.6, 129.0, 128.1, 123.8, 115.7, 105.2, 102.5, 63.9, 25.3, 15.5,
1712, 1439, 1384, 1012, 693 cm–1. HRMS: [M]+ C11H12O, theoreti-
cal mass 160.0888; found 160.0891.
4-(2-Fluorophenyl)-2-methylbuta-2,3-dien-1-ol (23): Compound 3e
(126 mg, 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-
%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-%), iPrMgCl (2.0  in Et2O,
1.25 mL, 2.5 mmol) and 1-fluoro-2-iodobenzene (0.29 mL,
2.5 mmol) were treated according to the general procedure B. After
purification, compound 23 (70 mg, 39% yield) was obtained as yel-
12.6 ppm. IR (KBr): ν = 3408, 2966, 1711, 1445, 1384, 1011, 754
˜
1
low oil. H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 7.34–7.30
cm–1. HRMS: [M]+ C13H15OF, theoretical mass 206.1101; found
206.1092. C13H15OF (206.110): calcd. C 75.7, H 7.3; found C 75.7,
H 7.5.
(m, 1 H), 7.17–7.11 (m, 1 H), 7.07–6.97 (m, 2 H), 6.46–6.43 (m, 1
H), 4.18–4.09 (m, 2 H), 1.83 (d, J = 2.9 Hz, 3 H) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C, TMS): δ = 201.7, 160.8, 158.4, 128.2,
123.9, 115.6, 115.4, 104.4, 89.3, 63.7, 15.2 ppm. IR (KBr): ν = 3349,
4-(3-Methoxyphenyl)-2-methylhexa-2,3-dien-1-ol (19): Compound
3d (154 mg, 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol,
10 mol-%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-%), iPrMgCl (2.0 
in Et2O, 1.25 mL, 2.5 mmol) and 3-iodoanisole (0.3 mL, 2.5 mmol)
were treated according to the general procedure B. After purifica-
tion, compound 19 (125 mg, 57% yield) was obtained as yellow oil.
1H NMR (400 MHz, CDCl3, 25 °C, TMS): δ = 7.21 (t, J = 7.8 Hz,
1 H), 6.97 (d, J = 7.8 Hz, 1 H), 6.91 (s, 1 H), 6.74 (m, 1 H), 4.12–
4.09 (m, 2 H), 3.79 (s, 3 H), 2.43 (q, J = 7.3 Hz, 2 H), 1.82 (s, 3
H), 1.09 (t, J = 7.3 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3,
25 °C, TMS): δ = 198.7, 159.5, 138.8, 129.1, 118.5, 112.0, 111.5,
˜
2923, 2360, 1494, 1456, 1384, 1233, 1092, 1031, 753 cm–1. HRMS:
[M]+ C11H11OF, theoretical mass 178.0788; found 178.0781.
2-tert-Butyl-5-methyl-2-phenyl-2,5-dihydrofuran (24): Compound 9
(108 mg, 0.5 mmol) was dissolved in THF (5 mL) under argon.
AuCl3 (3 mg, 0.01 mmol, 2 mol-%) was added. The mixture was
kept stirring under argon for 24 h. The solvent was removed under
reduced pressure. The crude was purified by flash column
chromatography (Et2O/cyclohexane: 1:9) over silica gel to give pure
product 24 (72 mg, 67%) as white solid; m.p. 62 °C. 1H NMR
(400 MHz, CDCl3, 25 °C, TMS): δ = 7.34 (d, J = 7.2 Hz, 2 H),
7.25 (t, J = 7.2 Hz, 2 H), 7.19 (d, J = 7.2 Hz, 1 H), 6.28 (dd, J =
6.0 and 2.5 Hz, 1 H), 5.71 (dd, J = 6.0 and 1.2 Hz, 1 H), 4.72–4.65
(m, 1 H), 1.31 (d, J = 6.5 Hz, 3 H), 0.89 (s, 9 H) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C, TMS): δ = 143.6, 131.3, 130.5, 127.2,
110.6, 104.8, 63.9, 55.1, 23.2, 15.5, 12.6 ppm. IR (KBr): ν = 3365,
˜
2963, 2931, 2359, 1603, 1455, 1285, 1042, 777, 693 cm–1. HRMS:
[M]+ C14H18O2, theoretical mass 218.1301; found 218.1302.
Methyl 4-(6-Hydroxy-5-methylhexa-3,4-dien-3-yl)benzoate (20):
Compound 3d (154 mg, 1 mmol), [Cu(MeCN)4][BF4] (31.4 mg,
0.1 mmol, 10 mol-%), (BuO)3P (54 µL, 0.2 mmol, 20 mol-%),
iPrMgCl (2.0  in Et2O, 1.25 mL, 2.5 mmol) and methyl 4-iodo-
benzoate (654 mg, 2.5 mmol) were treated according to the general
procedure B. After purification, compound 20 (150 mg, 61% yield)
was obtained as white solid; m.p. 89 °C. 1H NMR (400 MHz,
CDCl3, 25 °C, TMS): δ = 7.94 (d, J = 8.5 Hz, 2 H), 7.41 (d, J =
8.5 Hz, 2 H), 4.18–4.10 (m, 2 H), 3.88 (s, 3 H), 2.45 (q, J = 7.3 Hz,
2 H), 1.84 (s, 3 H), 1.10 (t, J = 7.3 Hz, 3 H) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C, TMS): δ = 199.9, 166.9, 142.2, 129.5,
128.1, 125.7, 110.0, 105.3, 63.9, 51.9, 23.0, 15.4, 12.5 ppm. IR
126.8, 126.0, 97.4, 79.7, 36.7, 26.0, 20.4 ppm. IR (KBr): ν = 2976,
˜
1443, 1384, 1095, 1048, 909, 700 cm–1. HRMS: [M]+ C15H20O,
theoretical mass 216.1509; found 216.1504.
Supporting Information (see also the footnote on the first page of
this article): 1H and 13C NMR spectra of all the propargylic dioxol-
anones and allenes.
Acknowledgments
One of us (X. T.) is grateful to the Framework Programme 6 of the
European Union for providing a Marie Curie Early Stage Fellow-
ship under Contract MEST-CT-2005-019780 (INDAC-CHEM: An
Industrial-Academic Chemistry Nursery for Economic Growth).
Financial and other support from COST (European Cooperation
in Science and Technology) through its Action “D40 Innovative
Catalysis” is acknowledged by S. W. and N. K. and from the UK
government, Engineering and Physical Sciences Research Council
(EPSRC) (Grant EP/F033478/1) to S. W.
(KBr): ν = 3427, 2967, 2359, 1715, 1605, 1435, 1384, 1279, 1112,
˜
1016 cm–1. HRMS: [M]+ C15H18O3, theoretical mass 246.1250;
found 246.1257.
2,5,5-Trimethylhexa-2,3-dien-1-ol (21): Compound 3e (126 mg,
1 mmol), [Cu(MeCN)4][BF4] (31.4 mg, 0.1 mmol, 10 mol-%),
(BuO)3P (54 µL, 0.2 mmol, 20 mol-%) and tBuMgCl (2.0  in
Et2O, 1 mL, 2 mmol) were treated according to the general pro-
cedure A. After purification, compound 21 (87 mg, 62% yield) was
1
obtained as yellow oil. H NMR (400 MHz, CDCl3, 25 °C, TMS):
δ = 5.29–5.25 (m, 1 H), 3.99–3.94 (m, 2 H), 1.69 (d, J = 2.8 Hz, 3
[1] a) N. Krause, A. S. K. Hashmi (Eds.), Modern Allenes Chemis-
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Krause, Angew. Chem. Int. Ed. 2002, 41, 2933–2935; c) N.
H), 1.01 (s, 9 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS):
δ = 195.9, 106.6, 102.3, 63.7, 32.1, 30.1, 15.7 ppm. IR (KBr): ν =
˜
Eur. J. Org. Chem. 2009, 2836–2844
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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2843

X. Tang, S. Woodward, N. Krause
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Received: March 3, 2009
Published Online: April 24, 2009
2844
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 2836–2844