Palladium-Catalyzed Cyclocarbonylation of Terminal and Internal Alkynols to 2(5H)-Furanones

Article abstract of DOI:10.1021/jo9703663

A series of substituted alkynols, containing alkyl, phenyl, and vinyl groups at the acetylenic terminal, were found to undergo direct carbonylation to the corresponding substituted 2(5H)-furanones in 67-98% yield. This reaction requires catalytic quantiti

Full text of DOI:10.1021/jo9703663

5684
J . Org. Chem. 1997, 62, 5684-5687
Articles
P a lla d iu m -Ca ta lyzed Cycloca r bon yla tion of Ter m in a l a n d In ter n a l
Alk yn ols to 2(5H)-F u r a n on es
Wing-Yiu Yu and Howard Alper*
Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada
Received February 26, 1997X
A series of substituted alkynols, containing alkyl, phenyl, and vinyl groups at the acetylenic terminal,
were found to undergo direct carbonylation to the corresponding substituted 2(5H)-furanones in
67-98% yield. This reaction requires catalytic quantities of Pd2(dba)3‚CHCl3 (4 mol %) and 1,4-
bis(diphenylphosphino)butane (dppb) (8 mol %) in dichloromethane under an atmosphere of CO
(600 psi) and H2 (200 psi) at 95 °C for 36 h. Hydrogen is required for this reaction. Another
bidentate ligand such as 1,3-bis(diphenylphosphino)propane, and a monodentate ligand such as
PPh3 or PCy3, are equally effective for this reaction. Conjugated ene-ynols can also be carbonylated
affording 3-alkenyl-2(5H)-furanones in good yield. However, double bond isomerization (cis-trans)
occurred if an ene-ynol containing a cis olefinic substituent was used as the substrate. The
cyclocarbonylation reaction is believed to proceed via an allenylpalladium intermediate, which is
formed by initial insertion of Pd(0) into the C-O bond of the alkynol followed by a rearrangement.
The transition metal catalyzed carbonylation of prop-
subject it to Pd(PPh3)4-catalyzed carbonylation in the
presence of methanol to give the methyl ester of 2,3-
dienoic acid. The ester was then hydrolyzed to the
corresponding 2,3-dienoic acid which was subsequently
transformed to butenolide with the use of either protonic
acid (H+)7 or a Lewis acid such as Ag+ ion.8
argyl alcohols and their derivatives has attracted con-
siderable attention in recent years. The carbonylation
of propargyl esters, halides, and phosphonates in the
presence of various nucleophiles, such as alcohols, amines,
and compounds containing activated methylene groups,
has been extensively reviewed.1 Previously we reported
that the nickel-catalyzed carbonylation of alkynols can
selectively furnish alkenoic acids under phase-transfer
catalysis conditions,2a,b or dienoic acids using a hydri-
do(aqua)palladium complex.3
2(5H)-Furanone, or butenolide, comprises a structural
moiety frequently present in biologically active natural
products.4 For instance Annonaceous acetogenin, isolated
from a family of the tropical plant Annonaceous, displays
interesting cytoytoxic activities against several cell lines.5
It is known that butenolide can be prepared from
propargyl alcohol via a sequence of transformations
involving palladium-catalyzed carbonylation as one of the
principal steps (Scheme 1). First reported by Stille and
co-workers,6a propargyl alcohol was converted to iodoallyl
alcohol by treatment with LiAlH4/I2, which was then
cyclocarbonylated to butenolide using Pd(PPh3)2Cl2/
K2CO3 under 2 atm of carbon monoxide. Another ap-
proach is to first derivatize the propargyl alcohol as its
ester, phosphonate ester, or other derivatives,1 and then
Thus far, there are few examples for the preparation
of butenolides by direct incorporation of carbon monoxide
into alkynols.9 Indeed, an attempt to carbonylate inter-
nal alkynols to butenolides with [Pd(CH3CN)2(P-
Ph3)2](BF4)2 as the catalyst led to the formation of 2,3-
dienoic acids as the major product in most cases.10 In
1991, we reported the cyclocarbonylation reaction of
terminal propargyl alcohols to 5,5-disubstituted 2(5H)-
furanonessa direct synthesis of butenolide from prop-
argyl alcoholsusing Pd(dba)2 and 1,4-bis(diphenylphos-
phino)butane (dppb) in DME at 150 °C for 48 h.11 The
reaction was not applicable to internal alkynols. We now
report a modified procedure for this reaction which
substantially extends its utility to internal alkynols with
alkyl, phenyl, and vinyl units attached to one acetylenic
carbon atom (eq 1).
Treatment of 2-methyl-4-butyn-2-ol (1a ) with carbon
monoxide (600 psi) and hydrogen (200 psi) in dichlo-
(7) For acid (H+)-induced cyclization of 2,3-dienoic acids to buteno-
lides, see: (a) Kresze, G.; Kloimstein, L.; Runge, W. Liebigs Ann. Chem.
1976, 979. (b) Musierowicz, S.; Wroblewski, A. E. Tetrahedron 1977,
1753.
(8) Marshall, J . A.; Wolf, M. A.; Wallace, E. M. J . Org. Chem. 1997,
62, 367.
(9) An example of PdI2/KI-catalyzed oxidative cyclocarbonylation of
propargyl alcohols to R-methylene-â-lactone has been reported: Bonar-
di, A.; Costa, M.; Gabriele, B.; Salerno, G.; Chiusoli, G. P. J . Chem.
Soc., Chem. Commun. 1994, 1429. (b) Another study reported that
acetylenes can be carbonylated under water-gas shift conditions to form
butenolides using rhodium catalyst: J oh, T.; Doyama, K.; Onitsuka,
K.; Shiohara, T.; Takahashi, S. Organometallics 1991, 10, 2493. (c)
Alkynols were also reported to react with carbon monoxide and
iodobenzene in the presence of transition-metal complex and carbon
dioxide, affording 3(2H)-furanones: Inoue, Y.; Ohuchi, K.; Yen, I. F.;
Imaizumi, S. Bull. Chem. Soc. J pn. 1989, 62, 3518.
X Abstract published in Advance ACS Abstracts, August 1, 1997.
(1) Tsuji, J .; Mandai, T. Angew. Chem., Int. Ed. Engl. 1995, 34, 2589.
(2) (a) Satyanarayana, N.; Alper, H. Organometallics 1991, 10, 804.
(b) Zhou, Z. Z.; Alper, H. Organometallics 1996, 15, 3282.
(3) Huh, K. T.; Orita, A.; Alper, H. J . Org. Chem. 1993, 58, 6956.
(4) For review concerning the synthesis of butenolides, see: (a)
Nagao, Y.; Dai, W.; Ochiai, M.; Shiro, M. J . Org. Chem. 1989, 54, 5211
and references cited therein. (b) Corey, E. J .; Cheng, X. M. In The Logic
of Chemical Synthesis; J ohn Wiley & Sons Inc: New York, 1989. (c)
Knight, D. W. Contemp. Org. Synth. 1994, 1, 287.
(5) For review, see: Figadere, D. Acc. Chem. Res. 1995, 28, 359 and
references cited therein.
(6) (a) Stille, J . K.; Cowell, A. Tetrahedron Lett. 1979, 133. (b)
Recently, the R,â-unsaturated iodo ketones were found to undergo
carbonylation, affording γ-alkylidene butenolides: Coperet, C.; Sugi-
hara, T.; Wu, G.; Shimoyama, I.; Negishi, E.-I. J . Am. Chem. Soc. 1995,
117, 3422 and references cited therein.
(10) Matsushita, K.; Komori, T.; Oi, S.; Inoue, Y. Tetrahedron Lett.
1994, 35, 5889.
(11) El-Ali, B.; Alper, H. J . Org. Chem. 1991, 56, 4099.
S0022-3263(97)00366-6 CCC: $14.00 © 1997 American Chemical Society

Cyclocarbonylation of Alkynols to 2(5H)-Furanones
J . Org. Chem., Vol. 62, No. 17, 1997 5685
Sch em e 1a
a
(a) LiAlH4, then I2; (b) Pd(PPh3)2Cl2/K2CO3, CO (2 atm); (c) mesyl chloride or diethyl chlorophosphate, base; (d) Pd(PPh3)4, CO, MeOH;
(e) LiOH or BCl3; (f) H+ or Ag+.
Ta ble 1. P a lla d iu m -Ca ta lyzed Cycloca r bon yla tion of
Alk yn ols to 2(5H)-F u r a n on es
H
romethane in the presence of catalytic quantities of
Pd2(dba)3‚CHCl3 (4 mol %) and dppb (8 mol %) for 36 h
at 95 °C afforded 5,5-dimethyl-2(5H)-furanone (2a ) in
nearly quantitative yield. Unlike the previously pub-
lished procedure, this reaction requires a hydrogen
atmosphere in order to obtain the butenolide in reason-
able yield, as no butenolide was obtained without H2 even
at higher temperature (150 °C), and the substrate was
recovered. The requirement for hydrogen was also
encountered in the palladium-catalyzed cyclocarbonyla-
tion of allylphenols, anilines, and alcohols.12 It is note-
worthy that alkynols containing both terminal and
internal CtC bonds with alkyl, phenyl, and vinyl sub-
stituents attached to one of the acetylenic carbon atoms
reacted with similar efficiency, affording 2(5H)-furanones
in good to excellent yield (Table 1). By adopting the
previous procedure, i.e. Pd(dba)2/dppb, DME at 150 °C,
no butenolide was obtained if 2-methyl-3-octyn-2-ol (1e)
was used as the substrate, and partial decomposition of
the alkynol was revealed by the GLC analysis of the
crude reaction mixture. Other bidentate ligands such as
1,3-bis(diphenylphosphino)propane (dppp), or monoden-
tate ligands like PPh3 and PCy3, can be used for this
reaction, but 1,2-bis(diphenylphosphino)ethane is com-
pletely ineffective. This can be explained by the fact that
CO insertion into a Pd-C bond occurs faster for those
alkylpalladium diphosphine complexes containing a more
flexible metal-ligand chelate ring.13 Tertiary as well as
secondary propargyl alcohols can be converted to the
corresponding butenolides, but a primary alkynol, such
as 2-butyn-1-ol, was unreactive under the typical carbo-
nylation conditions. The choice of solvent was important
as only dichloromethane or chloroform were useful for
attaining the butenolide. The use of tetrahydrofuran,
dimethoxyethane, benzene, or dimethylformamide as the
solvent resulted in complete inhibition of the reaction or
reduced butenolide production, or in case of DME as the
solvent, substantial substrate decomposition was ob-
served.
a
b
Isolated yield. Typical reaction condition: alcohol (1 mmol),
Pd2(dba)3‚CHCl3 (0.04 mmol), dppb (0.08 mmol), dry CH2Cl2 (10
mL), CO/H2 ) 600/200 psi at 95 °C, 36 h. c Sample contained R-n-
butylidene-γ-lactone isomer; ratio of butenolide:γ-lactone ) 4-4.5:1
1
as determined by H NMR. The combined yield of the butenolide
and the lactone was 97%. Reaction was run for 48 h. e The trans
d
isomer 2f was formed as the major product, trans:cis ratio ) 79:
21 determined by 1H NMR.
The Pd2(dba)3/dppb-catalyzed cyclocarbonylation of
2-methyl-3-octyn-2-ol (1e) to 3-n-butyl-5,5-dimethyl-
2(5H)-furanone (2e) was accompanied by the formation
of R-n-butylidene-γ-butyrolactone, probably via a CdC
bond shift. Using 1H NMR spectroscopy, the ratio of
butenolide-to-γ-lactone was found to be 4-4.5:1 (deter-
mined by the integration ratio of the olefinic protons: [δ
6.95 (t, J ) 1.5 Hz) for butenolide; δ 6.24 (t, J ) 8 Hz)
for γ-lactone]). The butenolide-to-γ-lactone isomerization
became more pronounced when the reaction mixture was
completely devoid of solvent. If the reaction mixture,
with solvent completely evaporated, was left overnight
at room temperature, the butenolide and γ-lactone were
1
(12) (a) El-Ali, B.; Okuro, K.; Vasapollo, G.; Alper, H. J . Am. Chem.
Soc. 1996, 118, 4264. (b) Yu, W.-Y.; Bensimon, C.; Alper, H. Chem.
Eur. J . 1997, in press. (c) Brunner, M.; Alper, H. J . Org. Chem. 1997,
submitted for publication.
(13) (a) Dekker, G. P. C. M.; Elsevier, C. J .; Vrieze, K.; van Leeuwen,
P. W. N. M. Organometallics 1992, 11, 1598. (b) Dekker, G. P. C. M.;
Elsevier, C. J .; Vrieze, K.; van Leeuwen, P. W. N. M. J . Organomet.
Chem. 1992, 430, 357.
isolated in a 1:1 ratio as determined by H NMR. The
conjugated ene-ynol 1f reacted with carbon monoxide
to give 3-alkenyl-5-methyl-2(5H)-furanone 2f in 85%
isolated yield. If the isomeric ene-ynol 1g, bearing a cis
CdC linkage, was subjected to the carbonylation condi-
tions, the butenolide 2f containing a trans olefinic unit

5686 J . Org. Chem., Vol. 62, No. 17, 1997
Yu and Alper
Sch em e 2
Sch em e 3
was formed as the major product with the trans:cis ratio
being 79:21.
A possible mechanism for the cyclocarbonylation of
alkynols is outlined in Scheme 2. Palladium(0) can
undergo insertion into the C-O bond of the substrate
followed by rearrangement to the allenylpalladium in-
termediate 3 (as proposed for allyl systems)14. Insertion
of carbon monoxide and subsequent reductive elimination
may lead to the 2,3-dienoic acid 4. Trace quantities of
acid present in the solvent can result in cyclization of 4
to give 2(5H)-furanone. Since only freshly dried CH2Cl2
was used for all reactions, and no transformation of
substrate to butenolide was observed without the ap-
plication of hydrogen gas, we assume that the protonic
acid might have originated from the interaction between
Pd(0), H2, and CH2Cl2 under the reaction conditions, but
the mechanism is unclear. Nevertheless, it is known that
CHCl3 reacts with H2 and Pd(0) to generate H+ as
reported in the Pd/C-catalyzed hydrogenation of nitriles
to amine hydrochlorides.15 A control experiment per-
formed under the standard carbonylation conditions, i.e.
a CO/H2 ) 600/200 psi mixture, Pd2(dba)3/dppb in
CH2Cl2, with added HCl (1 equiv vs Pd) using 1e as the
substrate resulted in complete consumption of the reac-
tant in 8 h. However, only 38% (compared with 69% in
the absence of HCl) of pure 2e was isolated, and when
the latter reaction was repeated in the absence of
hydrogen, the yield of 2e was 30%. These results indicate
that hydrogen has several different roles in this reaction.
The cis f trans double bond isomerization in the
cyclocarbonylation of the cis ene-ynol 1g to 2f may
proceed via the π-allylpalladium complex 5 (Scheme 3).
A similar intermediate has been proposed for the pal-
ladium-catalyzed reactions of 2,3-dienyl alcohols,16
amines,17 and esters.18 The trans CdC bond could arise
by η3-η1 isomerization of the π-allylpalladium complex
5 to the σ-allenylpalladium complex 6, which then
6
undergoes intramolecular cyclocarbonylation, affording
the 2(5H)-furanone 2f. Alternatively, the CdC bond
isomerization might occur via a hydridopalladium inter-
mediate involving a sequence of hydropalladation, C-C
bond rotation, and then reductive elimination.
In conclusion, Pd2(dba)3‚CHCl3 together with dppb is
an excellent carbonylation system for the synthesis of
2(5H)-furanones from alkynols by reaction with carbon
monoxide and hydrogen. This reaction represents an
atom economical approach19 to this class of synthetically
useful compounds.
(18) (a) Kleijin, H.; Westmijze, H.; Meijer, J .; Vermeer, P. Recl. Trav.
Chim. Pays-Bas 1983, 102, 378. (b) Djahanbini, D.; Cazes, B.; Gore, J .
Tetrahedron Lett. 1984, 25, 203. (c) Nokami, J .; Maihara, A.; Tsuji, J .
Tetrahedron Lett. 1990, 31, 5629.
(19) Recent examples of atom economical metal-catalyzed synthesis
of butenolides include the following. (a) Ruthenium catalyzed Alder-
ene reaction: Trost, B. M.; Muller, T. J . J . J . Am. Chem. Soc. 1994,
116, 4985. (b) Titanocene-catalyzed Pauson-Khand reaction of acety-
lenic ketones: Kablaoui, N. M.; Hicks, F. A.; Buchwald, S. L. J . Am.
Chem. Soc. 1996, 118, 5818.
(14) (a) Osakada, K.; Chiba, T.; Nakamura, Y.; Yamamoto, T.;
Yamamoto, A. J . Chem. Soc., Chem. Commun. 1986, 1589. (b) Mura-
hashi, S.-I.; Imada, I.; Taniguchi, Y.; Higashimura, S. J . Org. Chem.
1993, 58, 1538 and references cited therein.
(15) Serist, J . A. III; Logue, M. W. J . Org. Chem. 1972, 37, 335.
(16) Piotti, E. M.; Alper, H. J . Org. Chem. 1994, 59, 1956.
(17) Imada, Y.; Vasapollo, G.; Alper, H. J . Org. Chem. 1996, 61,
7982.

Cyclocarbonylation of Alkynols to 2(5H)-Furanones
J . Org. Chem., Vol. 62, No. 17, 1997 5687
for C12H20O [M+] 180.151 41, found, 180.154 94. Anal. Calcd
for C12H20O: C, 79.93; H, 11.19. Found: C, 80.15; H, 11.51.
Exp er im en ta l Section
Ma ter ia ls. Alkynols obtained from commercial source were
used as received, or purified by vacuum distillation, if neces-
sary, prior to use. Benzene, THF, 1,2-dimethoxyethane, and
diethyl ether were dried and distilled from sodium/benzophe-
none ketyl under nitrogen before use. Dichloromethane for
the cyclocarbonylation reaction was freshly distilled from CaH2
under nitrogen. All other common solvents were used without
purification. All chemicals were used as received. The acetone
used for akynyllithium quenching was distilled from anhy-
drous K2CO3 prior to use. The vinyl bromide leading to the
cis-5-Dod ecen -3-yn -2-ol (1g): colorless oil; 1H NMR (200
MHz, CDCl3/TMS) δ 0.89 (br t, J ) 6.6 Hz, 3H), 1.1-1.7 (m,
8H), 1.48 (d, J ) 6.5 Hz, 3H), 2.12 (m, 1H), 2.32 (m, 2H), 4.68
(m, 1H), 5.48 (br d, J ) 10.8 Hz, 1H), 5.91 (dt, J ) 10.8, 7.3
Hz, 1H); 13C NMR (50.3 MHz, CDCl3/TMS) δ 14.1, 22.6, 24.4,
28.7, 30.2, 31.6, 58.8, 81.4, 95.6, 108.8, 121.8, 145.2; HRMS
(EI, 70 eV) calcd for C12H20O [M+] 180.151 41, found 180.151 10.
Anal. Calcd for C12H20O: C, 79.93; H, 11.19. Found: C, 80.07;
H, 11.07.
Typ ica l P r oced u r e for th e P a lla d iu m -Ca ta lyzed Cy-
cloca r bon yla tion of Alk yn ols. A mixture of the alkynol (1
mmol), Pd2(dba)3‚CHCl3 (0.04 mmol), dppb (0.08 mmol), and
anhydrous CH2Cl2 was reacted with carbon monoxide (600 psi)
and hydrogen (200 psi) at 95 °C in a stainless steel autoclave
for 36 h. After the autoclave was cooled to room temperature,
the gases were released, and the crude reaction mixture was
eluted through a plug of Florisil using CH2Cl2 as the eluant.
The light yellow solution was evaporated to dryness using a
rotary evaporator. The residue was then purified by chroma-
tography with a short silica gel column using hexanes as the
initial eluant, then with hexanes/ethyl acetate ) 1:1 to elute
the product from the column. The butenolide was further
purified using Kugelrohr distillation.
22
alkynols 1f20 and 1g21 and Pd2(dba)3‚CHCl3 were prepared
according to literature procedures.
Gen er a l P r oced u r e for th e P r ep a r a tion of Alk yn ols
1d a n d 1e. To a THF solution (15 mL) of phenylacetylene
(10 mmol) [for 1d ]/1-hexyne (10 mmol) [for 1e] was added
n-BuLi (2.5 M in hexanes, 4.0 mL) at ice-cold temperature.
The yellow solution was stirred at this temperature for at least
20 min. Acetone (ca. 0.8 mL) was then added, resulting in
immediate decoloration. The solution was stirred for an
additional 20 min, and then water (10 mL) was added. The
product was then extracted with diethyl ether (3 × 20 mL).
The combined organic extracts were washed with brine (2 ×
20 mL) and dried over MgSO4. The solvent was removed by
rotary evaporation, and the light yellow oily residue was
purified by flash column chromatography using hexanes/
diethyl ether ) 2:1 as the eluant. The alcohols were further
purified by vacuum distillation before use.
2(5H)-Furanones 2a , 2b,24 and 2c6a are known compounds
and had spectral data in accord with that of the literature.
The following butenolides are new.
5,5-Dim eth yl-3-p h en yl-2(5H)-fu r a n on e (2d ): colorless
2-Meth yl-4-p h en yl-3-bu tyn -2-ol (1d ): 83% yield; colorless
oil; 1H NMR (200 MHz, CDCl3/TMS) δ 1.60 (s, 6H), 3.01 (s,
1H), 7.24-7.30 (m, 3H), 7.27-7.45 (m, 2H); 13C NMR (50.3
MHz, CDCl3/TMS) δ 31.3, 65.4, 82.1, 93.9, 122.3, 128.0, 128.1,
131.5; HRMS (EI, 70 eV) calcd for C11H12O [M+] 160.088 82,
found 160.089 21. Anal. Calcd for C11H12O: C, 82.45; H, 7.55.
Found: C, 82.79; H, 7.69.
1
crystals; mp 68.5-69.0 °C; νCdO ) 1741 cm-1; H NMR (200
MHz, CDCl3/TMS) δ 1.56 (s, 6H), 7.38-7.42 (m, 3H), 7.51 (s,
1H), 7.83-7.88 (m, 2H); 13C NMR (50.3 MHz, CDCl3/TMS) δ
25.7, 83.4, 112.3, 127.1, 128.6, 129.2, 130.1, 152.9, 171.1;
HRMS (EI, 70 eV) calcd for C12H12O2 [M+] 188.0837, found
188.081 94. Anal. Calcd for C12H12O2: C, 76.56; H, 6.43.
Found: C, 76.57; H, 6.58.
3-n -Bu t yl-5,5-d im et h yl-2(5H)-fu r a n on e (2e): colorless
oil; νCdO ) 1735 cm-1; 1H NMR (200 MHz, CDCl3/TMS) δ 0.93
(t, J ) 7.3 Hz, 3H), 1.26-1.65 (m, 4H), 2.24 (t, J ) 7.2 Hz,
2H), 6.95 (t, J ) 1.5 Hz, 1H); 13C NMR (CDCl3/TMS) δ 13.7,
22.2, 24.7, 25.7, 29.5, 84.2, 132.4, 153.0, 173.3; HRMS (EI, 70
eV) calcd for C10H16O2[M+] 168.115 03, found 168.116 31.
Anal. Calcd for C10H16O2: C, 71.38; H, 9.59. Found, C, 71.73;
H, 9.64.
tr a n s-3-(1-Octen yl)-5-m eth yl-2(5H)-fu r a n on e (2f): col-
orless oil; νCdO ) 1739 cm-1; 1H NMR (200 MHz, CDCl3/TMS)
δ 0.88 (br t, J ) 6.6 Hz, 3H), 1.2-1.6 (m, 8H), 1.44 (d, J ) 6.8
Hz, 3H), 2.15 (m, 2H), 5.05 (br q, J ≈ 6.9 Hz, 1H), 6.09 (dd, J
) 15.9, 0.6 Hz, 1H), 6.81 (dt, J ) 15.9, 8 Hz, 1H), 7.05 (d, J )
1.3 Hz, 1H); 13C NMR (50.3 MHz, CDCl3/TMS) δ 14.0, 19.1,
22.5, 28.7, 31.6, 33.4, 76.7, 118.2, 129.3, 138.7, 146.9, 172.1;
HRMS (EI, 70 eV) calcd for C13H20O2 [M+] 208.146 33, found
208.146 62. Anal. Calcd for C13H20O2: C, 74.95; H, 9.68.
Found: C, 74.72; H, 9.88.
2-Meth yl-3-octyn -2-ol (1e): 76% yield; colorless oil; 1H
NMR (200 MHz, CDCl3/TMS) δ 0.91 (t, J ) 7.2 Hz, 3H), 1.41-
1.57 (m, 4H), 1.5 (s, 6H), 1.85 (s, 1H), 2.18 (t, J ) 7.0 Hz, 2H);
13C NMR (50.3 MHz, CDCl3/TMS) δ 14.0, 22.5, 24.7, 28.5, 31.3,
58.5, 82.2, 84.7; HRMS (EI, 70 eV) calcd for C8H13O [M+
CH3] 125.0966, found 125.095 33. Anal. Calcd for C9H16O:
C, 77.08; H, 11.51. Found: C, 77.13; H, 11.63.
-
Gen er a l P r oced u r e for th e P r ep a r a tion of Alk yn ols
1f a n d 1g.23 To a mixture of vinyl bromide (3 mmol), 3-butyn-
2-ol (3 mmol), and NEt3 (5 mL) were added Pd(PPh3)4 (0.15
mmol) and CuCl (0.3 mmol) under an inert atmosphere. The
mixture was stirred overnight at room temperature. The
reaction mixture was then diluted with diethyl ether (20 mL)
and filtered through Celite. The filter cake was washed with
diethyl ether (ca. 30 mL), and the solvent was removed in
vacuo. The oily residue was purified by chromatography using
silica gel (eluant, hexanes/diethyl ether ) 2:1). The alcohols
were further purified by vacuum distillation.
tr a n s-5-Dod ecen -3-yn -2-ol (1f): colorless oil; 1H NMR
(200 MHz, CDCl3/TMS) δ 0.88 (br t, J ) 7.1 Hz, 3H), 1.1-1.6
(m, 8H), 1.46 (d, J ) 6.5 Hz, 3H), 2.13 (m, 3H), 4.63 (m, 1H),
5.45 (dd, J ) 15.6, 1.5 Hz, 1H), 6.14 (dt J ) 15.6, 7 Hz, 1H);
13C NMR (50.3 MHz, CDCl3/TMS) δ 14.0, 22.5, 24.3, 28.7, 31.5,
33.0, 58.7, 82.8, 89.3, 108.7, 145.5; HRMS (EI, 70 eV) calcd
Ack n ow led gm en t. We are indebted to the Natural
Sciences and Engineering Research Council of Canada
for financial assistance and the Croucher Foundation
(Hong Kong) for a postdoctoral fellowship (W.Y.Y.). We
greatly appreciate the time taken by Mr. Wen-J ing Xiao
to carry out several experiments.
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