Neighboring heteroatom effect unique to aqueous aldol reactions of water-insoluble substrates

Article abstract of DOI:10.1021/jo500213b

The reactions of ketones and aldehydes in the presence of Li⁺ and in the presence or absence of PTC mediated by water were performed to produce aldol products. Several advantages of the aqueous reactions over organic solvent-mediated ones have been demonstrated including higher yields, shorter reaction times, simpler purifications, and better functional group tolerance. Some reactions that do not take place in organic solvents have been realized in water. The successes are attributed to the neighboring heteroatom effect. In the aqueous aldol condensations, Li₂CO₃ was an efficient catalyst, and therefore base-liable groups such as epoxides, esters, and silyl groups could survive. For heteroaromatic ethanones, the aqueous aldol reactions were accomplished without PTC to give β-hydroxyketones in good yields. The water-mediated condensations of aldosyl hemiacetals with aromatic ketones led to a new carbohydrate-derived skeleton in quantitative yields. To some extent, this research has expanded the applicablities of aldol condensations and reactions.

Full text of DOI:10.1021/jo500213b

Article
pubs.acs.org/joc
Neighboring Heteroatom Effect Unique to Aqueous Aldol
Reactions of Water-Insoluble Substrates
Bo Li and Chunbao Li*
Department of Chemistry, School of Science, Tianjin University, Tianjin 300072, China
S
* Supporting Information
ABSTRACT: The reactions of ketones and aldehydes in the
presence of Li+ and in the presence or absence of PTC
mediated by water were performed to produce aldol products.
Several advantages of the aqueous reactions over organic
solvent-mediated ones have been demonstrated including
higher yields, shorter reaction times, simpler purifications,
and better functional group tolerance. Some reactions that do
not take place in organic solvents have been realized in water.
The successes are attributed to the neighboring heteroatom
effect. In the aqueous aldol condensations, Li2CO3 was an efficient catalyst, and therefore base-liable groups such as epoxides,
esters, and silyl groups could survive. For heteroaromatic ethanones, the aqueous aldol reactions were accomplished without
PTC to give β-hydroxyketones in good yields. The water-mediated condensations of aldosyl hemiacetals with aromatic ketones
led to a new carbohydrate-derived skeleton in quantitative yields. To some extent, this research has expanded the applicablities of
aldol condensations and reactions.
with a diameter of about 1 mm in the middle and 2 mm along
the rest of the wire) between the two blades (Supporting
Information). This design effectively expands the reach of the
stirring rod and worked well for reactions in a 100 mL flask.
The modified stirring rod was used in the following reactions.
VSSHMP ketone 1a was stirred at 80 °C with PTFE sand,
Aliquat 336 (8 mol %), benzaldehydes (1.05 equiv), NaOH
(20 mol %), and water for 2−5.5 h to yield 1aa−1ac quantitatively
(Table 1, entries 1−3). The substitution of Aliquat 336 with
solid benzyltriethylamonium chloride, solid tetraethylamonium
chloride, liquid N-butyl-N-methyl imidazolium chloride, solid
sodium dodecyl sulfate, or liquid PEG 400 all ended in failure.
This indicates that Aliquat 336 functions as both a phase
transfer catalyst (PTC) and a reaction medium for the
VSSHMP ketone. The PTFE sand functions as hundreds of
stirrers to efficiently promote the dissolution of the VSSHMP
substrate in Aliquat 336. Similarly, VSSHMP ketones 1b−1d
reacted with aromatic aldehydes to yield the corresponding
α,β-unsaturated ketones 1ba−1db in quantitative yields (Table 1,
entries 4−10). Because products 1aa−1db are VSSHMP, they
were collected simply by filtration and washing with a small
amount of aqueous acetone. The base, water, Aliquat 336, and
sand were all recyclable for eight cycles for the condensation of
1c with p-methoxybenzaldehyde to yield 1cc. For comparison, a
single wire-modified stirring rod (Supporting Information,
page S4) was used instead of the double wire-modified one
(Supporting Information, page S5) in the preparations of 1aa
and 1ac with the reaction yields and times. The reason that the
INTRODUCTION
■
Aldol reaction is a powerful means of forming carbon−carbon
bonds in organic chemistry. Classically, the reaction is
performed by treating aldehydes and ketones in ethanol or
methanol with bases or acids. One problem is the substrates
bearing base-labile groups like ester, halide, epoxide, and
sulfonate cannot survive such conditions. Another problem is
the severe self-condensations of alkyl aldehydes bearing
α-hydrogen atoms, which consume excess aldehydes, leading
to substantial amounts of side products. The modifications of
aldol reaction such as antibody-catalyzed and enzyme-catalyzed
aldol reactions and the Mukaiyama aldol reaction have greatly
expanded its applicabilities.1 However, the problems associated
with these modifications are the high costs for enzymes and
antibodys and the substrate ketone has to be converted to boron
or silicon enolates. In our continuing research on aqueous
reactions, we have discovered that some aldol reactions could only
be accomplished in water and not in organic solvents. The
neighboring heteroatom effect (NHE) on these reactions was also
investigated. Herein, we wish to report these results.
RESULTS AND DISCUSSION
■
In our previous work, the aqueous reactions of very sparing
soluble high-melting-point (VSSHMP) substrates were accel-
erated by polytetrafluoroethylene (PTFE) sand (70 pieces/g)
and agitated by a standard two-blade stirring rod.2 In that work,
it was noted that occasionally small amounts of the sticky
reactant adhered to the reaction flask, and this reactant could
not be reached by the standard stirring rod. This can lead to
incomplete reactions. To solve this problem, the stirring rod
was modified by inserting two PTFE wires (about 25 cm long
Received: January 28, 2014
Published: February 17, 2014
© 2014 American Chemical Society
2242
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254

The Journal of Organic Chemistry
Article
a
Table 1. Quantitative Aqueous Aldol Condensations of VSSHMP Ketones with Aromatic Aldehydes
a
Reaction conditions: ketone (1 g), aromatic aldehyde (1.05 equiv), base (20 mol %), Aliquat 336 (8 mol %), PTFE sand (5 g), and water (8 mL),
b
c
mechanical stirring (400 rmp) at 80 °C. NaOH as the base. Na2CO3 as the base.
double wire-modified stirring rod was selected is that the wire is
handmade and not always robust. In the preparation of 1cc, the
reaction time was 6.5 h at a stirring rate of 100 rmp, much
longer than that in Table 1, entry 7 (3 h, 400 rmp). The
reaction time was 3.0 h at 600 rmp, the same as in Table 1,
entry 7. Stirring rate 400 rmp was appropriate.
Scheme 1. The NHE That Is Unique to the Aqueous Systems
and Not Effective in Organic Solvents
The aqueous reaction of 1b with p-nitrobenzaldehyde (Table 1,
entry 4) catalyzed by NaOH was much faster than that of 1a
(Table 1, entry 1). It is speculated that the α-oxygen atom in 1b
chelated with the enolate M+, which stabilized the intermediate
and accelerated the reaction (Scheme 1). To verify this
speculation, experiments (reactions A-D) were carried out in
water versus in methanol, and the results are summarized in
Table 2. The condensations of 1a and p-nitrobenzaldehyde
were performed in the presence of water, Aliquat 336, and
PTEF sand and catalyzed by Li2CO3, Na2CO3, K2CO3, or
Cs2CO3. The strongest base, Cs2CO3, gave a 29% yield of 1aa;
the other ones did not give any products or led to trace
products (Table 2, entries 2−4). The methanol-mediated
reactions for 1a catalyzed by these carbonates were successful
in 90−96% yields of 1aa (entries 1−4). For 1a, the catalytic
efficiency orders of the carbonates and their basicities were
the same in water or in methanol. When 1b which bears an
α-oxygen atom was also subjected to the same aqueous reaction
2243
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254

The Journal of Organic Chemistry
Article
Table 2. Comparison of Carbonate-Catalyzed Condensations of Ketones and Heteroatom-Bearing Ketones with Aldehydes in
a
Methanol versus in Water
water
methanol
b
entry
reaction
M
t (h)
yield
t (h)
yield
c
1
2
A
A
A
A
B
B
B
B
C
C
D
D
Li
Na
K
9
9
NR
20
5.8
2
90%
96%
93%
93%
92%
93%
94%
94%
trace
trace
3
9
4
Cs
Li
9
29%
1
5
0.5
0.7
2
>99%
>99%
>99%
>99%
>99%
>99%
>99%
>99%
20
6
6
Na
K
7
2
8
Cs
Li
6
1
c
9
36
23
9
10
10
10
10
65%
73%
c
10
11
12
Na
Li
d
NR
NR
d
Na
14
a
Reaction conditions in water:ketone (1a, 1b, 2a, or 2b, 0.5 g), aldehyde (1.05 equiv), M2CO3 (20 mol %), Aliquat 336 (8 mol %), PTFE sand (5 g),
and H2O (4 mL), mechanical stirring (400 rmp); reaction conditions in methanol:ketone (1a, 1b, 2a, or 2b, 0.5 g), aldehyde (1.05 equiv), M2CO3
b
c
(20 mol %), and methanol (4 mL), reflux. Reaction temperatures in water: 80 °C for A and B, 70 °C for C and D. The yield of 1-(4-
hydroxyphenyl)ethanone. NR, no reaction.
d
conditions as for 1a, a quantitative yield of 1ba was produced
(Table 2, entries 5−8). The aqueous catalytic efficiency order
of the carbonates for 1b was Li2CO3 (0.5 h) > Na2CO3 (0.7 h) >
K2CO3 (2 h) > Cs2CO3 (6 h), which is opposite to their basicity
order and in accordance with their hardness order of M+. When
methanol was used instead of water as the solvent, the most
efficient catalyst was Cs2CO3 (entry 8). However, the yield in
this case was not quantitative (94%). In the case of 2a, the
aqueous condensation catalyzed by Na2CO3 was faster than
that catalyzed by Li2CO3 (entries 9 and 10). For ketone 2b
with a β-oxygen atom (entries 11 and 12), the aqueous reaction
catalyzed by Li2CO3 was faster than that by catalyzed Na2CO3,
both in quantitative yields. In contrary, a methanol-mediated
aldol condensation for 2a or 2b did not occur. These
extraordinary performances of the aqueous reactions for 1b
and 2b are attributed to the NHE. Although this effect has been
documented in other organic solvent-mediated reactions,3 it is
unique to the aqueous systems in this report. In the control
experiments (1a vs 1b), this effect was not observed in other
organic solvent-mediated reactions: in N,N-dimethylformamide
(DMF) and tetrahydrofuran-water. The aqueous reaction is
heterogeneous and the methanol-mediated one homogeneous.
It is therefore believed that in the aqueous systems, Li+ can be
efficiently transferred into the phase of the substrate dissolved
in Aliquat 336 to chelate with the α- or β-oxygen atom and the
carbonyl group of 1b or 2b without competition. Another
possible explanation is that these “on-water” reactions are
catalyzed by the small intense Li+ ions which can congregate at
the water−organic interface and can complex with both
neighboring oxygen atoms and the carbonyl groups of reactants
which approach the barrier under vigorous stirring.4 However,
in polar solvents such as methanol, the oxygen atoms of the
2244
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254

The Journal of Organic Chemistry
Article
a
Table 3. Aqueous Aldol Condensations of Neighboring Heteroatom-Bearing Ketones with Aldehydes
2245
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254

The Journal of Organic Chemistry
Article
Table 3. continued
a
Reaction conditions: ketone (1b or 3b−3j, 1 g), aldehyde (2.0 equiv for entries 15 and 19; 1.05 equiv for the others), Li2CO3 (20 mol %), Aliquat
b
336 (5 mol % for 3g−3i; 8 mol % for the others), PTFE sand (5 g), and water (8 mL), mechanical stirring (400 rmp). 1.0 equiv LiOH was used as
catalyst. The flask was covered with aluminum foil. Yield after chromatographic purification.
c
d
solvent are in excess and are predominately associated with Li+
which prevents the chelation of Li+ with the α- or β-oxygen
atom and the carbonyl group.
have been prepared twice with the same outcomes (the same
reaction rates and quantitative yields), demonstrating that these
reactions are reproducible.
The aldol reactions of a series of neighboring heteroatom-
bearing ketones with aldehydes catalyzed by Li2CO3 were
carried out in the presence of Aliquat 336 and PTFE sand
(Table 3). As most of the substrates used in “on-water” reactions
are liquid or liquid plus solid, the aqueous reactions of very sparing
soluble high-melting-point substrates are not common and
challenging.2,5 Most of the ketones (1b, 3b−3g, 3i, and 3j) are
VSSHMP (mp: 81−210 °C; solubility: 6.6 × 10−3 to 1.1 ×
10−7 mol L−1; data from SciFinder). The condensation yields were
up to quantitative, and the products were simply collected by
filtration except for entries 15 and 19. The advantage of using
Li2CO3 as the catalyst is that base-liable groups such as epoxides
(entries 1−15), esters (entries 3−6, 9, and 10), and silyl groups
(entries 7 and 8) can survive the reaction. However, it is well
documented that in the organic solvent-mediated aldol reactions,
substrate ketones bearing these base-liable groups either partially
or completely decomposed in the presence of NaOH or MeONa
or do not condense with the aldehydes catalyzed by Li2CO3 or
Na2CO3.6 Although the epoxide, ketal, heteroaromatic ketones,
and carbohydrates (Table 5) were successful in aqueous aldol
reactions, the aqueous reactions of 2-methoxycyclohenanone and
3-methoxybutanone with benzaldehyde led to decomposition of
the former and rather low reaction rate for the latter. Diacetyl
(unprotected) and pyruvatesters could not survive the basic
conditions. In the control experiments, treating 3g and benzal-
dehyde or isovaleraldehyde with NaOH or LiOH or Na2CO3 in
methanol did not furnish any desired products (3gb or 3gc)
because stronger bases NaOH and LiOH decomposed the
α,β-epoxy carbonyl group and weak base Na2CO3 was not capable
of catalyzing the reaction. Although the aldol condensation
between aromatic ethanone 3i and aromatic aldehydes is known,
the aldol condensation using aliphatic aldehydes leading to 3ia
type of skeleton has never been reported. Ketones 3ga and 3gb
The NHE was also successfully applied to heteroaromatic
ethanones (Scheme 1). For 4a−4c, the aqueous direct aldol
reactions in the presence of LiOH were accomplished without
PTC, to give β-hydroxyketones 4aa−4cb in good yields
(Table 4, entries 1−7). Further this reaction was easily scaled
up to 20 g. In the literature, these reactions have often been
conducted in the presence of BuLi or LDA at a low temperature
(−78 °C) in anhydrous solvents (ether or tetrahydrofuran).7 In
the control experiments, these aldol reactions in methanol or
DMF catalyzed by NaOH, Cs2CO3, or DBU failed completely.
The direct aqueous aldol reaction between 3i and isovaler-
aldehyde in the presence of LiOH in the presence of Aliquat 336
was realized in a 41% yield of 4da at 0 °C. The yield of 4da was
improved to 93% at −18 °C. There is only one known
compound with the skeleton represented by 4da, which was
synthesized via the Mukaiyama aldol reaction starting from the
corresponding silyl enol ether in 75% yield.8
Carbohydrates play an essential role in life and chemistry and
are versatile intermediates in organic synthesis.9 However,
utilizing protected aldosyl hemiacetals in aldol reactions
remains challenging. The only example is the condensation of
O-benzyl-protected aldosyl hemiacetals with excess acetone to
yield (3E,5Z,7S,8R)-5,7,9-tribenzyloxy-8-hydroxynona-3,5-dien-
2-one and two other analogs in 68−70% yields.10 The open-
chain form of carbohydrates contains a neighboring oxygen
atom for the carbonyl group; although it is only found in
minute amounts because of the equilibrium with the cyclic
hemiacetal form. It would be interesting to test if the NHE can
be used for carbohydrates (Scheme 1). A series of ketones was
found to react well with O-benzyl-protected D-glucosyl and
D-xylosyl hemiacetals, in the presence of LiOH and tetra-
butylammonium bromide (TBAB) in water (Table 5). All the
reactions only took 15 min and gave good to quantitative
2246
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254

The Journal of Organic Chemistry
Article
a
Table 4. Aqueous Aldol Reaction of Heteroaromatic Ethanones with Aliphatic Aldehydes
a
Reaction conditions (entries 1−7): ketone (4a−4c, 1 g), aldehyde (1.5 equiv for entries 1, 3, and 6; 2.0 equiv for entries 2, 4, and 7; 5.0 equiv for
b
entry 5), LiOH (0.5 equiv), water (3 mL), magnetic stirring (400 rmp). Reaction conditions (entry 8): 3i (1.0 g), aldehyde (2.0 equiv), LiOH (2.0
equiv), Aliquat 336 (5 mol %), water (8 mL), and PTFE sand (5 g), mechanical stirring (400 rmp).
yields. The reactions of O-benzyl-protected D-glucosyl and D-
xylosyl hemiacetals with liquid aliphatic ketones 5a and 5b and
VSSHMP steroidal ketones 1c and 5d all produced chiral
conjugated dienones 5aa−5db containing a free hydroxyl
group. The reactions with aromatic ketones 5e and 5f produced
chiral diketones 5ea−5fb with an enolether and a free hydroxyl
group. Two sequential reactions, the aldol condensation and a
BnOH elimination, took place in one pot for 5aa−5db, and the
two sequential reactions plus a Michael addition took place for
5ea−5fb. The possible reason is that aromatic methyl ketones
are less hindered and more acidic than steroidal and aliphatic
ones and are capable of adding to the dienones to form 5ea−
5fb. The reactions for products 5aa−5bb and 5ea−5fb were so
clean that chromatography was not necessary. In the control
experiments, the preparation of 5eb in refluxing organic solvent
(methanol or CHCl3) catalyzed by M2CO3 or MOH (M: Li,
Na, and K) or DBU for 8 h ended in failure. These aqueous
condensations provide a facile method for the synthesis of
carbohydrate derivatives with a new type of skeleton (5ea−5fb)
containing enolether, carbonyl, and free hydroxyl groups. It is
easily to envisage the usefulness of this new type of skeleton.
For example, the free hydroxyl groups could be transformed
into tosylate or halide and substituted with amine or azide,
which after a reductive ring closure would give deoxy miglitol
derivatives. Miglitol is widely used clinically in treating
diabetes.11 The carbohydrate diketones could also lead to
heterocyclic compounds bearing chiral hydroxyl groups. This
research is currently underway in our laboratory.
substrates; some of these results are unachievable via organic
solvent-mediated reactions. In addition, the aqueous reactions
have advantages of higher yields, shorter reaction times, simpler
purifications, and better functional group tolerance. Especially,
the condensation reactions between aldosyl hemiacetals and
ketones gave multifunctionalized compounds, among which the
carbohydrate diketones with a new type of skeleton were
formed. This methodology is also useful in endeavors to replace
organic solvents with water in organic synthesis.
EXPERIMENTAL SECTION
General Information. All of the chemicals were obtained from
commercial sources or prepared according to standard methods. NMR
spectra were recorded with a 400 or 600 MHz spectrometer for H
■
1
NMR and NOESY and 100 or 151 MHz for 13C{1H} NMR using
TMS as an internal standard. Chemical shifts (δ) are reported relative
to TMS (1H) or CDCl3 (13C). Multiplicities are reported as follows:
singlet (s), doublet (d), triplet (t), quartet (q), and multiplet (m).
Melting points were recorded with a micromelting-point apparatus.
Infrared analyses (KBr pellet) were performed by FT-IR. Elemental
analyses for C, H, N, and Si were performed on an elemental analyzer.
High-resolution spectra (HRMS) were recorded on a QTOF mass
analyzer with electrospray ionization (ESI). All the aqueous reactions
except for the preparations of 4aa−4cb were conducted in 100 mL
flasks and agitated by the modified stirring rod. The size of PTFE sand
is 70 pieces/g.
General Procedures for the Aqueous Aldol Reactions
(Procedures A−D). Procedure A: A mixture of ketone (1.000 g),
Aliquat 336, PTFE sand (5 g), aldehyde, water (8 mL), and base was
mechanically stirred (400 rmp). After TLC indicated completion of
the reaction, it was stopped, and the crude product was suspended in
water, while the PTFE sand precipitated on the bottom. The
In summary, the NHE has been proven, and this effect is
uniquely applicable to the aqueous reactions for a series of
2247
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254

The Journal of Organic Chemistry
Article
a
Table 5. Aqueous Aldol Reactions of Ketones and Protected Aldosyl Hemiacetals
a
Reaction conditions: aldosyl hemiacetal (1 mmol), TBAB (1.0 equiv), ketone (1.0 equiv for 1c and 5d; 6.0 equiv for the others), LiOH (2.0 equiv),
PTFE sand (5 g), and water (2.5 mL), mechanical stirring (400 rmp) at 60 °C for 15 min.
2248
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254

The Journal of Organic Chemistry
Article
suspension was filtrated and washed with cold aqueous acetone (3 mL,
75% v/v) to give the corresponding products, leaving the PTFE sand
to be recovered.
2.07−2.00 (m, 1H), 0.99 (d, J = 6.8 Hz, 3H), 0.82 (s, 3H), 0.80 (d, J =
6.3 Hz, 3H), 0.78 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 201.1,
160.0, 137.3, 133.1, 132.3, 128.3, 113.9, 109.2, 80.8, 66.9, 62.2, 56.2,
55.3, 53.7, 42.6, 42.1, 41.6, 40.4, 40.0, 35.9, 35.0, 31.8, 31.7, 31.4, 30.3,
28.8, 28.6, 21.3, 17.1, 16.4, 14.5, 12.0; IR (KBr): v 3060, 2944, 1681,
1588, 1567, 1511, 1255, 1178, 1052, 983, 834, 534 cm−1; elemental
analysis calcd (%) for C35H48O4: C 78.91, H 9.08, O 12.01; found: C
78.71, H 9.10.
(E)-3-Phenyl-1-(4-(trityloxy)phenyl)prop-2-en-1-one (2aa). Proce-
dure A: 500 mg of 2a was used; 615 mg, quantitative yield; white solid;
mp 191−192 °C; 1H NMR (400 MHz, CDCl3): δ 7.79−7.74 (m, 3H),
7.63−7.60 (m, 2H), 7.50−7.40 (m, 10H), 7.34−7.25 (m, 9H), 6.84 (d,
J = 8.8 Hz, 2H); 13C NMR (100 MHz, CDCl3): δ 193.8, 154.7, 143.5,
143.4, 135.0, 130.8, 130.2, 130.0, 128.9, 128.5, 127.9, 127.6, 127.4,
121.1, 120.5, 91.9; IR (KBr): v 3059, 3027, 1662, 1596, 1474, 1446,
1221, 975, 751, 700 cm−1; elemental analysis calcd (%) for C34H26O2:
C 87.52, H 5.62, O 6.86; found, C 87.71, H 5.68.
Procedure B: After magnetically stirring (400 rmp) a mixture of
heteroaromatic ethanone, LiOH (0.5 equiv), and water (3 mL per
gram of ketone) for 15 min, aldehyde was added dropwisely within
20 min. The mixture was stirred for an additional period of time and
then extracted with ethyl acetate three times, washed with water, and
dried over Na2SO4. The unreacted heteroaromatic ethanone was
recovered using bulb to bulb distillation, leaving the desired product to
be collected.
Procedure C: A mixture of ketone (6 mmol), aldosyl hemiacetal
(1 mmol), TBAB (322 mg), LiOH (48 mg), PTFE sand (5 g), and
water (2.5 mL) was mechanically stirred (400 rmp) at 60 °C for
15 min. The crude product was extracted with ethyl acetate (3 × 8 mL),
washed with water (2 × 10 mL), and dried over Na2SO4. The starting
material (ketone) and byproduct (BnOH) were removed by bulb-to-
bulb distillation under reduced pressure at about 60 °C.
(E)-3-Phenyl-1-(2-(trityloxy)phenyl)prop-2-en-1-one (2ba). Proce-
Procedure D: A mixture of 1c or 5d (1 mmol), aldosyl hemiacetal
(1 mmol), TBAB (322 mg), LiOH (48 mg), PTFE sand (5 g), and
water (2.5 mL) was mechanically stirred (400 rmp) at 60 °C for 15 min.
The reaction was stopped and extracted with ethyl acetate (3 × 8 mL),
dried over Na2SO4, and purified by flash chromatograph on silica gel to
afford the corresponding product.
dure A: 500 mg of 2b was used; 613 mg, quantitative yield; white
solid; mp 120−121 °C; H NMR (400 MHz, CDCl3): δ 7.61−7.46
1
(m, 9H), 7.40−7.31 (m, 5H), 7.25−7.19 (m, 9H), 6.99 (t, J = 7.2 Hz,
1H), 6.89 (t, J = 7.4 Hz, 1H), 6.60 (d, J = 8.4 Hz, 1H); 13C NMR (100
MHz, CDCl3): δ 188.8, 160.8, 143.8, 143.6, 135.1, 131.2, 130.4, 129.7,
129.0, 128.8, 128.7, 128.4, 128.0, 127.8, 127.5, 121.9, 120.1, 91.1; IR
(KBr): v 3058, 3028, 1662, 1598, 1494, 1447, 1218, 977, 751, 699
cm−1; elemental analysis calcd (%) for C34H26O2: C 87.52, H 5.62, O
6.86; found, C 87.45, H 5.65.
Products 1ab,12 1ac,12 1ca,13 1cb,14 1cc,14 1 cd,15 3aa,16 and 3bb16
are known compounds and were synthesized quantitatively according
to procedure A.
(E)-3β-Hydroxy-21-(4-nitrobenzal)pregn-5-en-20-one (1aa). Pro-
cedure A: 1.425 g, quantitative yield; white solid; mp 213−216 °C; 1H
NMR (400 MHz, CDCl3): δ 8.26 (d, J = 8.5 Hz, 2H), 7.71 (d, J = 8.5
Hz, 2H), 7.58 (d, J = 15.9 Hz, 1H), 6.88 (d, J = 15.9 Hz, 1H), 5.38 (d,
J = 3.9 Hz, 1H), 3.60−3.50 (m, 1H), 2.90−2.86 (m, 1H), 2.41−2.23
(m, 3H), 1.02 (s, 3H), 0.67 (s, 3H); 13C NMR (100 MHz, CDCl3): δ
199.8, 148.5, 141.1, 140.8, 138.4, 130.2, 128.8, 124.1, 121.3, 71.6, 62.6,
57.2, 50.0, 45.2, 42.2, 39.2, 37.3, 36.5, 32.0, 31.8, 31.6, 24.6, 22.7, 21.1,
19.4, 13.5; IR (KBr): v 3611, 2940, 1677, 1608, 1518, 1344, 1112,
1056, 849, 756 cm−1; elemental analysis calcd (%) for C28H35NO4: C
74.80, H 7.85, O 14.23, N 3.12; found: C 75.23, H 7.79, N 3.07.
(E)-3β-Hydroxy-16α,17α-epoxy-21-(4-nitrobenzal)pregn-5-en-20-
one (1ba). Procedure A: 1.400 g, quantitative yield; white solid; mp
202−204 °C; 1H NMR (400 MHz, CDCl3): δ 8.25 (d, J = 8.4 Hz, 2 H),
7.72−7.68 (m, 3H), 6.92 (d, J = 15.9 Hz, 1H), 5.36 (d, J = 3.7 Hz, 1H),
3.80 (s, 1H), 3.60−3.50 (m, 1H), 2.35−2.22 (m, 2H), 2.19 (s, 1H),
2.12−2.03 (m, 2H), 1.98 (d, J = 12.9 Hz, 1H), 1.86 (d, J = 10.9 Hz,
2H), 1.15 (s, 3H), 1.06 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 194.5,
148.6, 141.2, 140.9, 140.4, 129.0, 124.6, 124.1, 120.9, 71.6, 71.3, 60.4,
50.3, 45.6, 42.2, 42.1, 37.2, 36.7, 31.6, 31.5, 29.8, 27.8, 20.5, 19.3, 15.2;
IR (KBr): v 3626, 3409, 3104, 3075, 2938, 1681, 1615, 1595, 1516,
1342, 1055, 1001, 979, 833, 755 cm−1; elemental analysis calcd (%) for
C28H33NO5: C 72.55, H 7.18, N 3.02, O 17.26; found: C 72.37, H 7.11,
N 3.07.
(E)-3β-Hydroxy-16α,17α-epoxy-21-(4-methoxybenzal)pregn-5-
en-20-one (3ab). Procedure A: 1.364 g, quantitative yield; white solid;
1
mp 187−189 °C; H NMR (400 MHz, CDCl3): δ 7.68 (d, J = 15.8
Hz, 1H), 7.52 (d, J = 8.6 Hz, 2H), 6.90 (d, J = 8.6 Hz, 2H), 6.72
(d, J = 15.8 Hz, 1H), 5.36 (d, J = 4.6 Hz, 1H), 3.85 (s, 3H), 3.75 (s,
1H), 3.59−3.49 (m, 1H), 2.34−2.21 (m, 2H), 2.10 (d, J = 10.6 Hz,
1H), 2.03−1.95 (m, 2H), 1.13 (s, 3H), 1.05 (s, 3H); 13C NMR (100
MHz, CDCl3): δ 194.9, 161.7, 143.5, 141.2, 130.3, 127.4, 121.0, 118.9,
114.4, 71.6, 71.3, 60.2, 55.4, 50.4, 45.7, 42.2, 42.0, 37.2, 36.7, 31.6,
31.6, 31.5, 29.9, 27.7, 20.6, 19.3, 15.3; IR (KBr): v 3550, 2939, 1675,
1602, 1577, 1513, 1247, 1178, 997, 810 cm−1; elemental analysis calcd
(%) for C29H36O4: C 77.64, H 8.09, O 14.27; found, C 77.77, H 8.16.
(E)-3β-Acetoxy-16α,17α-epoxy-21-(4-nitrobenzal)pregn-5-en-20-
one (3ba). Procedure A: 1.349 g, quantitative yield; white solid; mp
1
226−228 °C; H NMR (400 MHz, CDCl3): δ 8.25 (d, J = 8.1 Hz,
2H), 7.72−7.69 (m, 3H), 6.92 (d, J = 15.9 Hz, 1H), 5.39 (d, J = 2.8
Hz, 1H), 4.66−4.57 (m, 1H), 3.80 (s, 1H), 2.41−2.29 (m, 2H), 2.05
(s, 3H), 1.15 (s, 3H), 1.07 (s, 3H); 13C NMR (100 MHz, CDCl3): δ
194.5, 170.4, 148.5, 140.9, 140.3, 140.1, 129.0, 124.6, 124.1, 121.9, 73.7,
71.2, 60.3, 50.2, 45.6, 42.1, 38.1, 36.9, 36.8, 31.5, 29.7, 27.73, 27.68, 21.4,
20.4, 19.2, 15.2; IR (KBr): v 2941, 1728, 1685, 1613, 1519, 1345, 1245,
1030, 984, 755 cm−1; elemental analysis calcd for C30H35NO6: C 71.27, H
6.98, N 2.77, O 18.99; found, C 71.07, H 6.90, N 2.80.
(E)-3β-Benzoyloxy-16α,17α-epoxy-21-(4-nitrobenzal)pregn-5en-
(E)-2-Benzaltigogenone (1da). Procedure A: 1.218 g, quantitative
20-one (3ca). Procedure A: 1.314 g, quantitative yield; white solid; mp
1
1
yield; white solid; mp 228−230 °C; H NMR (400 MHz, CDCl3): δ
249−251 °C; H NMR (400 MHz, CDCl3): δ 8.25 (d, J = 8.7 Hz,
7.58 (d, J = 1.5 Hz, 1H), 7.43−7.34 (m, 5H), 4.43 (dd, J = 14.8, 7.4
Hz, 1H), 3.50 (dd, J = 10.4, 3.0 Hz, 1H), 3.39 (t, J = 10.9 Hz, 1H),
3.12 (d, J = 15.7 Hz, 1H), 2.48 (dd, J = 18.7, 5.2 Hz, 1H), 2.30−2.18
(m, 2H), 2.06−2.00 (m, 1H), 0.99 (d, J = 6.9 Hz, 3H), 0.82 (s, 3H),
0.81 (d, J = 6.4 Hz, 3H), 0.78 (s, 3H); 13C NMR (100 MHz, CDCl3):
δ 201.2, 137.2, 135.7, 135.3, 130.3, 128.5, 128.4, 109.2, 80.7, 66.9, 62.3,
56.2, 53.6, 42.8, 42.4, 41.8, 41.6, 40.4, 39.9, 36.0, 35.0, 31.8, 31.7, 31.4,
30.3, 28.8, 28.6, 21.2, 17.2, 16.4, 14.5, 11.9; IR (KBr): v 2945, 1679,
1591, 1450, 1242, 1184, 1060, 981, 900, 699, 521 cm−1; elemental
analysis calcd (%) for C34H46O3: C 81.23, H 9.22, O 9.55; found: C
81.43, H 9.17.
(E)-2-(4-Methoxybenzal)tigogenone (1db). Procedure A: 1.279 g,
quantitative yield; white solid; mp 215−217 °C; 1H NMR (400 MHz,
CDCl3): δ 7.57 (d, J = 1.2 Hz, 1H), 7.40 (d, J = 8.5 Hz, 2H), 6.94
(d, J = 8.5 Hz, 2H), 4.43 (dd, J = 14.7, 7.3 Hz, 1H), 3.86 (s, 3H), 3.50
(dd, J = 10.1, 3.2 Hz, 1H), 3.40 (t, J = 10.9 Hz, 1H), 3.08 (d, J = 15.7
Hz, 1H), 2.46 (dd, J = 18.7, 5.2 Hz, 1H), 2.27−2.19 (m, 2H),
2H), 8.06 (d, J = 7.3 Hz, 2H), 7.73−7.69 (m, 3H), 7.57 (t, J = 7.4 Hz,
1H), 7.45 (t, J = 7.6 Hz, 2H), 6.93 (d, J = 16.0 Hz, 1H), 5.44 (d, J =
4.8 Hz, 1H), 4.92−4.84 (m, 1H), 3.81 (s, 1H), 2.54−2.45 (m, 2H),
2.14−1.92 (m, 5H), 1.17 (s, 3H), 1.13 (s, 3H); 13C NMR (100 MHz,
CDCl3): δ 194.5, 165.9, 148.5, 140.9, 140.3, 140.1, 132.8, 130.8, 129.5,
129.0, 128.3, 124.6, 124.1, 122.0, 74.4, 71.2, 60.3, 50.2, 45.6, 42.1, 38.2,
36.9, 36.8, 31.5, 29.8, 27.81, 27.78, 20.5, 19.3, 15.2; IR (KBr): v 3086,
2940, 1705, 1614, 1526, 1345, 1274, 1115, 985, 716 cm−1; elemental
analysis calcd for C35H37NO6: C 74.05, H 6.57, N 2.47, O 16.91;
found, C 74.25, H 6.62, N 2.42.
(E)-3β-Benzoyloxy-16α,17α-epoxy-21-benzalpregn-5-en-20-one
(3cb). Procedure A: 1.207 g, quantitative yield; white solid; mp 252−
254 °C; 1H NMR (400 MHz, CDCl3): δ 8.07 (d, J = 7.5 Hz, 2H), 7.72
(d, J = 15.9 Hz, 1H), 7.58−7.55 (m, 3H), 7.45 (t, J = 7.6 Hz, 2H), 7.41−
7.39 (m, 3H), 6.85 (d, J = 15.9 Hz, 1H), 5.44 (d, J = 4.4 Hz, 1H), 4.93−
4.84 (m, 1H), 3.78 (s, 1H), 2.51−2.49 (m, 2H), 2.13 (d, J = 10.4 Hz,
1H), 1.16 (s, 3H), 1.12 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 194.9,
2249
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254

The Journal of Organic Chemistry
Article
165.9, 143.5, 140.0, 134.7, 132.7, 130.8, 130.5, 129.5, 128.9, 128.5, 128.3,
122.1, 121.0, 74.4, 71.2, 60.2, 50.3, 45.6, 42.0, 38.2, 36.9, 36.8, 31.6, 31.5,
29.8, 27.8, 27.7, 20.5, 19.3, 15.3; IR (KBr): v 2943, 1712, 1679, 1604,
1276, 1115, 985, 758, 714 cm−1. elemental analysis calcd for C35H38O4: C
80.43, H 7.33, O 12.24; found, C 80.19, H 7.34.
(E)-2-Benzal-4β,5β-epoxytigogenone (3fb). Procedure A: 1.198 g,
quantitative yield; white solid; mp 209−211 °C; 1H NMR (400 MHz,
CDCl3): δ 7.74 (d, J = 2.3 Hz, 1H), 7.42−7.33 (m, 5H), 4.38 (dd, J =
14.9, 7.5 Hz, 1H), 3.50−3.46 (m, 1H), 3.36 (t, J = 10.9 Hz, 1H), 3.24
(s, 1H), 2.81 (d, J = 15.9 Hz, 1H), 2.56 (dd, J = 15.9, 2.9 Hz, 1H), 2.29
(td, J = 13.2, 4.1 Hz, 1H), 1.21 (s, 3H), 0.92 (d, J = 6.9 Hz, 3H), 0.79
(d, J = 6.3 Hz, 3H), 0.71 (s, 3H); 13C NMR (100 MHz, CDCl3): δ
196.0, 137.9, 135.0, 130.7, 129.9, 128.8, 128.4, 109.1, 80.5, 70.2, 66.8,
62.6, 62.0, 55.4, 47.9, 41.5, 40.5, 39.1, 38.4, 34.8, 31.7, 31.4, 31.3, 30.6,
30.2, 29.6, 28.8, 21.2, 19.0, 17.1, 16.3, 14.4; IR (KBr): v 2943, 2903,
1686, 1616, 1449, 1377, 1175, 1052, 983, 901, 868, 697 cm−1;
elemental analysis calcd (%) for C34H44O4: C 79.03, H 8.58, O 12.39;
found, C 79.41, H 8.74.
(E)-2-Phenyl-5-(4-nitrobenzal)-1-oxaspiro⟨2,5⟩octan-4-one
(3ga). Procedure A: 1.658 g, quantitative yield; yellow solid; mp 159−
160 °C; 1H NMR (400 MHz, CDCl3): δ 8.28 (d, J = 8.7 Hz, 2H), 7.70
(s, 1H), 7.59 (d, J = 8.6 Hz, 2H), 7.43−7.34 (m, 5H), 4.32 (s, 1H),
3.02−2.98 (m, 1H), 2.83−2.76 (m, 1H), 2.17−2.09 (m, 1H), 1.92−
1.84 (m, 1H), 1.76−1.71 (m, 1H), 1.62−1.51 (m, 1H); 13C NMR
(100 MHz, CDCl3): δ 196.6, 147.4, 141.7, 138.9, 134.6, 133.8, 131.0,
128.5, 128.3, 126.8, 123.6, 65.5, 64.9, 28.5, 25.7, 21.4; IR (KBr): v
3033, 2938, 1680, 1597, 1515, 1342, 1155, 1111, 929, 852, 712, 690
cm−1; HRMS calcd for C20H17NO4Na [M + Na+]: 358.1055; found:
358.1055.
(E)-3β-(Tert-butyldimethylsilyloxy)-16α,17α-epoxy-21-(4-
nitrobenzal)pregn-5-en-20-one (3da). Procedure A: 1.298 g,
quantitative yield; white solid; mp 255−257 °C; 1H NMR (400
MHz, CDCl3): δ 8.25 (d, J = 8.6 Hz, 2H), 7.72−7.68 (m, 3H), 6.92 (d,
J = 16.0 Hz, 1H), 5.33 (d, J = 4.7 Hz, 1H), 3.79 (s, 1H), 3.54−3.45
(m, 1H), 2.29 (t, J = 12.1 Hz, 1H), 2.19 (dd, J = 13.3, 3.3 Hz, 1H),
2.12−1.96 (m, 3H), 1.74 (d, J = 12.8 Hz, 1H), 1.15 (s, 3H), 1.05 (s,
3H), 0.91 (s, 9H), 0.08 (s, 6H); 13C NMR (100 MHz, CDCl3): δ
194.4, 148.5, 141.9, 140.9, 140.3, 129.0, 124.6, 124.1, 120.4, 72.5, 71.3,
60.3, 50.4, 45.6, 42.8, 42.1, 37.3, 36.8, 32.0, 31.5, 29.8, 27.8, 25.9, 20.5,
19.4, 18.2, 15.2, −4.6; IR (KBr): v 3117, 2931, 2856, 1682, 1602, 1516,
1344, 1251, 1099, 996, 834, 773 cm−1; elemental analysis calcd (%) for
C34H47NSiO5: C 70.67, H 8.20, N 2.42, Si 4.86, O 13.84; found, C
70.79, H 8.25, N 2.45, Si 4.79.
(E)-3β-(Tert-butyldimethylsilyloxy)-16α,17α-epoxy-21-benzal-
pregn-5-en-20-one (3db). Procedure A: 1.206 g, quantitative yield;
white solid; mp 173−175 °C; 1H NMR (400 MHz, CDCl3): δ 7.72 (d,
J = 15.9 Hz, 1H), 7.58−7.56 (m, 2H), 7.40−7.39 (m, 3H), 6.85 (d, J =
15.9 Hz, 1H), 5.33 (d, J = 4.7 Hz, 1H), 3.76 (s, 1H), 3.54−3.46 (m,
1H), 2.29 (t, J = 12.1 Hz, 1H), 2.20 (dd, J = 12.1, 4.1 Hz, 1H), 2.05−
1.95 (m, 2H), 1.82 (d, J = 13.3 Hz, 1H), 1.74 (d, J = 12.4 Hz, 1H),
1.14 (s, 3H), 1.05 (s, 3H), 0.91 (s, 9H), 0.08 (s, 6H); 13C NMR (100
MHz, CDCl3): δ 194.7, 143.4, 141.8, 134.7, 130.5, 128.9, 128.5, 121.0,
120.6, 72.5, 71.2, 60.1, 50.4, 45.7, 42.9, 42.0, 37.3, 36.8, 32.1, 31.6,
31.6, 29.8, 27.8, 26.0, 20.5, 19.4, 18.2, 15.3, −4.5; IR (KBr): v 3036,
2940, 2854, 1682, 1611, 1461, 1375, 1334, 1250, 1200, 1088, 981, 836,
761 cm−1; elemental analysis calcd (%) for C34H48SiO3: C 76.64, H
9.08, Si 5.27, O 9.01; found, C 76.57, H 9.15, Si 5.20.
(E)-2-Phenyl-5-benzal-1-oxaspiro⟨2,5⟩octan-4-one (3gb). Proce-
1
dure A: 1.429 g, quantitative yield; white solid; mp 112−114 °C; H
NMR (400 MHz, CDCl3): δ 7.74 (s, 1H), 7.48−7.34 (m, 10H), 4.33
(s, 1H), 3.05 (d, J = 16.4 Hz, 1H), 2.85−2.77 (m, 1H), 2.15−2.07 (m,
1H), 1.89−1.81 (m, 1H), 1.73−1.69 (m, 1H), 1.60−1.49 (m, 1H); 13C
NMR (100 MHz, CDCl3): δ 196.8, 137.8, 135.8, 135.3, 134.2, 130.6,
129.2, 128.5, 128.3, 126.8, 65.2, 64.8, 28.5, 25.9, 21.6; IR (KBr): v
3058, 3030, 2930, 2856, 1679, 1588, 1450, 1397, 1277, 1157, 934, 860,
762, 694 cm−1; HRMS calcd for C20H18O2Na [M + Na+]: 313.1204;
found: 313.1205.
(E)-2-(4-Nitrobenzal)-4β,5β-epoxy-17α-methyl-17β-acetoxy-an-
drostan-3-one (3ea). Procedure A: 1.368 g, quantitative yield; white
(E)-2-phenyl-5-(3-methyl-butylidene)-1-oxaspiro⟨2,5⟩octan-4-
one (3gc). A mixture of 3g (1.00 g), Aliquat 336 (100 mg, 5 mol %),
isovaleraldehyde (640 mg, 2.0 equiv), Li2CO3 (73 mg, 20 mol %),
PTFE sand (5 g), and water (8 mL) was mechanically stirred (400
rmp) at room temperature for 6 h. After TLC indicated completion of
the reaction, it was stopped and extracted with ethyl acetate (3 × 8
mL), dried over Na2SO4 and purified by flash chromatograph on silica
1
solid; mp 197−199 °C; H NMR (400 MHz, CDCl3): δ 8.28 (d, J =
8.7 Hz, 2H), 7.74 (d, J = 2.1 Hz, 1H), 7.52 (d, J = 8.6 Hz, 1H), 3.28 (s,
1H), 2.71 (d, J = 16.0 Hz, 1H), 2.66 (dd, J = 16.0, 2.9 Hz, 2H), 2.29
(td, J = 13.3, 4.2 Hz, 1H), 1.94 (s, 3H), 1.36 (s, 3H), 1.22 (s, 3H), 0.77
(s, 3H); 13C NMR (100 MHz, CDCl3): δ 195.5, 170.3, 147.5, 141.5,
135.0, 133.7, 130.5, 123.7, 90.3, 70.7, 62.5, 48.3, 48.1, 46.4, 38.5, 36.3,
35.7, 31.6, 31.3, 30.1, 29.6, 23.5, 21.9, 21.3, 21.2, 18.9, 14.2; IR (KBr):
v 2923, 1735, 1685, 1515, 1449, 1368, 1257, 1151, 1093, 940, 875
cm−1; elemental analysis calcd (%) for C29H35NO6: C 70.57, H 7.15, N
2.84, O 19.45; found, C 70.95, H 7.03, N 2.78.
1
gel to afford 1.107 g of 3gc: 83% yield; oil; H NMR (600 MHz,
CDCl3): δ 7.38−7.30 (m, 5H), 6.89 (tt, J = 7.6, 1.8 Hz, 1H), 4.25 (s,
1H), 2.67 (d, J = 16.2 Hz, 1H), 2.40 (t, J = 12.7 Hz, 1H), 2.07−1.96
(m, 3H), 1.85−1.77 (m, 2H), 1.63−1.60 (m, 1H), 1.52−1.45 (m, 1H),
0.95 (d, J = 6.7 Hz, 6H); 13C NMR (151 MHz, CDCl3): δ 196.2,
141.6, 136.3, 134.2, 128.2, 126.7, 65.0, 64.6, 37.4, 28.2, 26.3, 25.7, 22.6,
21.1; IR (KBr): v 2958, 2872, 1729, 1608, 1454, 1387, 1277, 1172,
761, 702 cm−1; HRMS calcd for C18H22O2Na [M + Na+]: 293.1517;
found: 293.1519.
(E)-2-Benzal-4β,5β-epoxy-17α-methyl-17β-acetoxy-androstan-3-
one (3eb). Procedure A: 1.241 g, quantitative yield; white solid; mp
1
162−164 °C; H NMR (400 MHz, CDCl3): δ 7.76 (d, J = 2.4 Hz,
1H), 7.43−7.34 (m, 5H), 3.25 (s, 1H), 2.83 (d, J = 15.9 Hz, 1H), 2.58
(dd, J = 15.9, 2.9 Hz, 1H), 2.28 (td, J = 13.2, 4.2 Hz, 1H), 1.94 (s,
3H), 1.36 (s, 3H), 1.22 (s, 3H), 0.77 (s, 3H); 13C NMR (100 MHz,
CDCl3): δ 196.2, 170.4, 138.0, 134.9, 130.7, 129.9, 128.8, 128.4, 90.5,
70.3, 62.7, 48.4, 47.9, 46.5, 38.4, 36.4, 35.7, 31.5, 31.4, 30.2, 29.6, 23.6,
22.0, 21.3, 21.0, 18.9, 14.2; IR (KBr): v 2982, 2943, 1725, 1681, 1607,
1449, 1372, 1262, 1154, 1092, 1022, 761, 695, 547 cm−1; elemental
analysis calcd (%) for C29H36O4: C 77.64, H 8.09, O 14.27; found, C
77.36, H 8.09.
(E)-1-(2-Methyl-1,3-dioxan-2-yl)-3-(4-nitrophenyl)prop-2-en-1-
one (3ha). Procedure A: 1.931 g, quantitative yield; yellow solid; mp
1
138−140 °C; H NMR (600 MHz, CDCl3): δ 8.27 (d, J = 8.7 Hz,
2H), 7.85 (d, J = 16.0 Hz, 1H), 7.78 (d, J = 8.7 Hz, 2H), 7.31 (d, J =
16.0 Hz, 1H), 4.02 (ddd, J = 12.5, 4.6, 1.9 Hz, 2H), 3.84 (td, J = 12.2,
2.5 Hz, 2H), 2.16−2.08 (m, 1H), 1.48 (s, 3H), 1.42 (d, J = 13.4 Hz,
1H); 13C NMR (151 MHz, CDCl3): δ 198.5, 148.7, 142.1, 140.6,
129.2, 124.2, 123.9, 101.0, 62.9, 24.9, 24.6; IR (KBr): v 2983, 2933,
1702, 1615, 1524, 1347, 1197, 1069, 1043, 837 cm−1; HRMS calcd for
C14H15NO5Na [M + Na+]: 300.0842, found: 300.0843.
(E)-2-(4-Nitrobenzal)-4β,5β-epoxytigogenone (3fa). Procedure A:
1
1.306 g, quantitative yield; white solid; mp 220−223 °C; H NMR
(400 MHz, CDCl3): δ 8.26 (d, J = 8.4 Hz, 2H), 7.72 (s, 1H), 7.50
(d, J = 8.4 Hz, 2H), 4.37 (dd, J = 14.7, 7.3 Hz, 1H), 3.47−3.45 (m,
1H), 3.34 (t, J = 10.9 Hz, 1H), 3.26 (s, 1H), 2.70−2.59 (m, 2H),
2.33−2.26 (m, 1H), 1.21 (s, 3H), 0.91 (d, J = 6.7 Hz, 3H), 0.78 (d, J =
6.1 Hz, 3H), 0.71 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 195.4,
147.5, 141.6, 134.9, 133.8, 130.4, 123.7, 109.2, 80.4, 70.6, 66.8, 62.5,
62.0, 55.3, 48.2, 41.5, 40.5, 39.0, 38.5, 34.8, 31.7, 31.6, 31.3, 30.5, 30.2,
29.6, 28.8, 21.4, 19.0, 17.1, 16.3, 14.4; IR (KBr): v 2947, 1711, 1686,
1599, 1517, 1454, 1343, 1243, 1055, 982, 861 cm−1; elemental analysis
calcd (%) for C34H43NO6: C 72.70, H 7.72, N 2.49, O 17.09; found, C
72.56, H 7.83, N 2.49.
(E)-1-(2-Methyl-1,3-dioxan-2-yl)-3-phenylprop-2-en-1-one (3hb).
Procedure A: 1.466 g, 91% yield; white solid; mp 81−82 °C; 1H NMR
(600 MHz, CDCl3): δ 7.86 (d, J = 16.0 Hz, 1H), 7.63 (dd, J = 6.9, 2.2
Hz, 2H), 7.42−7.40 (m, 3H), 7.22 (d, J = 15.9 Hz, 1H), 3.99 (ddd, J =
11.0, 4.8, 1.4 Hz, 2H), 3.85 (td, J = 12.3, 2.3 Hz, 2H), 2.12 (qt, J =
12.4, 4.9 Hz, 1H), 1.46 (s, 3H), 1.37 (d, J = 13.4 Hz, 1H); 13C NMR
(151 MHz, CDCl3): δ 198.3, 144.9, 134.4, 130.7, 128.8, 128.5, 120.3,
100.9, 62.6, 24.9, 24.7; IR (KBr): v 2960, 2927, 2884, 2847, 1698,
1613, 1142, 1080, 1046, 769 cm−1; HRMS calcd for C14H16O3Na
[M + Na+]: 255.0997, found: 255.0998.
2250
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254

The Journal of Organic Chemistry
Article
(E)-3-(4-Methoxyphenyl)-1-(2-methyl-1,3-dioxan-2-yl)prop-2-en-
134.3, 132.6, 128.3, 67.7, 45.7, 38.7, 18.8, 14.0; IR (KBr): v 3446, 3100,
2959, 2971, 2871, 1653, 1517, 1415, 1359, 1234, 1063, 726 cm−1; HRMS
calcd for C10H14O2SNa [M + Na+]: 221.0612, found: 221.0617.
Product 4bc (2.54 g, 58% yield) were synthesized according to
procedure B (6.00 g of 4b was used and 2.82 g was recovered) and is
known.7b
3-Hydroxy-4-methyl-1-(2-pyridinyl)pentan-1-one (4ca). Proce-
dure B: (500 mg of 4c was used, 519 mg of 4ca was obtained); oil;
1H NMR (600 MHz, CDCl3): δ 8.69 (d, J = 3.2 Hz, 1H), 8.08 (d, J =
7.8 Hz, 1H), 7.88 (t, J = 7.6 Hz, 1H), 7.52−7.50 (m, 1H), 3.95−3.93
(m, 2H), 3.35 (d, J = 16.4 Hz, 1H), 3.28 (dd, J = 16.5, 9.2 Hz, 1H),
1.88−1.78 (m, 1H), 1.02 (t, J = 6.3 Hz, 6H); 13C NMR (151 MHz,
CDCl3): δ 202.1, 153.2, 148.7, 137.2, 127.3, 122.0, 72.6, 42.6, 33.6,
18.4, 17.7; IR (KBr): v 3447, 3058, 2962, 1694, 1621, 1467, 1384,
1044, 998, 778, 616 cm−1; HRMS calcd for C11H15NO2Na [M + Na+]:
216.1000, found: 216.0999.
1-one (3hc). Procedure A: 1.692 g, 93% yield; white solid; mp 120−
1
121 °C; H NMR (600 MHz, CDCl3): δ 7.82 (d, J = 15.9 Hz, 1H),
7.58 (d, J = 8.7 Hz, 2H), 7.10 (d, J = 15.9 Hz, 1H), 6.93 (d, J = 8.7 Hz,
2H), 3.98 (ddd, J = 11.0, 4.8, 1.4 Hz, 2H), 3.88−3.84 (m, 5H), 2.11
(qt, J = 12.4, 4.9 Hz, 1H), 1.45 (s, 3H), 1.36 (d, J = 13.3 Hz, 1H); 13C
NMR (151 MHz, CDCl3): δ 198.3, 161.9, 144.8, 130.4, 127.1, 117.9,
114.3, 101.0, 62.6, 55.3, 55.2, 24.9; IR (KBr): v 2978, 2853, 1682, 1597,
1568, 1511, 1251, 1045, 800, 551 cm−1; HRMS calcd for C15H18O4Na
[M + Na+]: 285.1103, found: 285.1108.
Preparation of (E)-1-(2-benzofuranyl)-5-methylhex-2-en-1-one
(3ia). A mixture of 3i (1.00 g), isovaleraldehyde (2.0 equiv), Aliquat
336 (5 mol %), LiOH (1.0 equiv), PTFE sand (5 g), and water (5 mL)
was mechanically stirred (400 rmp) at 0 °C for 1 h. After stopping the
reaction by adding 1.2 equiv of acetic acid in 1 mL of water, it was
extracted with ethyl acetate (3 × 10 mL), dried over Na2SO4, and
purified by flash chromatograph on silica gel to afford the starting
material 3i (149 mg) and 3ia (382 mg, 32% yield). 3ia: Yellow solid;
3-Hydroxy-1-(2-pyridinyl)hexan-1-one (4cb). A mixture of 4c
(300 mg), butyraldehyde (2.0 equiv), LiOH (0.5 equiv), and water
(0.9 mL) was magnetically stirred (400 rmp) at 0 °C for 1.5 h. The
reaction was stopped and extracted with ethyl acetate (3 × 5 mL),
dried over Na2SO4, and purified by flash chromatograph on silica gel
to afford 4cb (182 mg, 38% yield); oil; 1H NMR (600 MHz, CDCl3):
δ 8.68 (s, 1H), 8.07 (d, J = 7.4 Hz, 1H), 7.88 (t, J = 7.1 Hz, 1H), 7.51
(s, 1H), 4.18 (s, 1H), 3.90 (s, 1H), 3.41 (d, J = 16.8 Hz, 1H), 3.26 (dd,
J = 16.6, 9.0 Hz, 1H), 1.62−1.44 (m, 4H), 0.96 (t, J = 6.1 Hz, 3H); 13C
NMR (151 MHz, CDCl3): δ 202.0, 153.1, 148.8, 137.2, 127.4, 122.0,
67.7, 45.5, 39.2, 18.8, 14.0; IR (KBr): v 3429, 3056, 2959, 2931, 2872,
1695, 1623, 1585, 1570, 1465, 1215, 997, 773 cm−1; HRMS calcd for
C11H13NONa [M − H2O + Na+]: 198.0895, found: 198.0899.
1-(2-Benzofuranyl)-3-hydroxy-5-methylhexan-1-one (4da). A
mixture of 3i (1.0 g), isovaleraldehyde (2.0 equiv), Aliquat 336
(5 mol %), LiOH (2.0 equiv), PTFE sand (5 g), and water (8 mL) was
mechanically stirred (400 rmp) at −18 °C for 1.5 h. After stopping the
reaction by adding 2.2 equiv of acetic acid in 1 mL of water, it was
extracted with ethyl acetate (3 × 10 mL), dried over Na2SO4, and
purified by flash chromatograph on silica gel to afford the starting
material 3i (492 mg) and 4da (726 mg, 93% yield). 4da: white solid;
1
mp 68−70 °C; H NMR (600 MHz, CDCl3): δ 7.71 (d, J = 7.8 Hz,
1H), 7.60 (dd, J = 8.4, 0.6 Hz, 1H), 7.56 (d, J = 0.8 Hz, 1H), 7.49−
7.46 (m, 1H), 7.32−7.30 (m, 1H), 7.23 (dt, J = 15.2, 7.5 Hz, 1H), 6.94
(dt, J = 15.4, 1.4 Hz, 1H), 2.24 (td, J = 7.1, 1.4 Hz, 2H), 1.91−1.82 (m,
1H), 0.98 (d, J = 6.7 Hz, 6H). 13C NMR (151 MHz, CDCl3): δ 179.7,
155.7, 153.4, 148.9, 128.1, 127.2, 126.0, 123.9, 123.2, 113.2, 112.4,
42.1, 28.0, 22.5; IR (KBr): v 3120, 3088, 1675, 1611, 1553, 1293, 1174,
1107, 1076, 847, 755 cm−1; elemental analysis calcd (%) for C15H16O2:
C 78.92, H 7.06, O 14.02; found: C 78.73, H 7.14.
(E)-3β-Hydroxy-3′-phenyl-4′,5′-dihydro-3′H-[16,17-d]triazol-21-
benzalpregn-5-en-20-one (3ja). As both the starting material and the
product are photosensitive, the reaction flask was covered with aluminum
foil, and the filtration was conducted in the dark. Procedure A: 1.209 g,
1
quantitative yield; white solid; mp 140−151 °C (decomposition); H
NMR (400 MHz, CDCl3): δ 7.77 (d, J = 15.9 Hz, 1H), 7.68−7.66 (m,
2H), 7.50 (d, J = 15.9 Hz, 1H), 7.44−7.33 (m, 7H), 7.07 (t, J = 6.7 Hz,
1H), 5.28 (d, J = 3.8 Hz, 1H), 5.00 (d, J = 6.4 Hz, 1H), 3.56−3.48 (m,
1H), 2.31−2.22 (m, 3H), 1.01 (s, 3H), 0.88 (s, 3H); 13C NMR (100 MHz,
CDCl3): δ 192.5, 144.0, 140.9, 139.3, 134.6, 130.8, 129.4, 129.0, 128.8,
123.4, 122.7, 120.8, 114.7, 107.5, 71.5, 57.3, 51.5, 50.5, 49.3, 42.1, 37.2, 36.5,
33.2, 33.0, 31.8, 31.5, 31.3, 26.9, 20.6, 19.3, 15.9; IR (KBr): v 3306, 2931,
1735, 1679, 1600, 1499, 1444, 1360, 1331, 1114, 1024, 910, 731, 649 cm−1;
elemental analysis calcd (%) for C34H39N3O2: C 78.28, H 7.54, N 8.05, O
6.13; found, C 78.08, H 7.59, N 8.11.
1
mp 63−64 °C; H NMR (600 MHz, CDCl3): δ 7.71 (d, J = 7.9 Hz,
1H), 7.58 (dd, J = 8.4, 0.7 Hz, 1H), 7.54 (d, J = 0.9 Hz, 1H), 7.49 (t,
J = 7.8 Hz, 1H), 7.32 (t, J = 7.6 Hz, 1H), 4.37−4.32 (m, 1H), 3.14
(ddd, J = 17.1, 2.6, 2.0 Hz, 1H), 3.06 (dd, J = 17.2, 8.9 Hz, 1H), 2.99−
2.96 (m, 1H), 1.92−1.83 (m, 1H), 1.63−1.58 (m, 1H), 1.32−1.27 (m,
Product 4aa (6.91 g, 79% yield) were synthesized according to
procedure B (6.00 g of 4a was used and 0.72 g was recovered) and is
known.7a
1
1H), 0.96 (dt, J = 6.7, 1.3 Hz, 6H); H NMR (600 MHz, CDCl3-
D2O): δ 7.71 (d, J = 7.9 Hz, 1H), 7.57 (d, J = 8.4 Hz, 1H), 7.54 (d, J =
0.6 Hz, 1H), 7.50−7.47 (m, 1H), 7.32 (t, J = 7.5 Hz, 1H), 4.35−4.31
(m, 1H), 3.14 (dd, J = 17.1, 2.9 Hz, 1H), 3.06 (dd, J = 17.1, 8.9 Hz,
1H), 1.90−1.85 (m, 1H), 1.62−1.58 (ddd, J = 14.3, 9.0, 5.6 Hz, 1H),
1.32−1.27 (m, 1H), 0.96 (dd, J = 6.7, 1.5 Hz, 6H); 13C NMR (151
MHz, CDCl3): δ 191.4, 155.7, 152.4, 128.5, 126.9, 124.0, 123.4, 113.5,
112.4, 66.0, 46.0, 45.9, 24.5, 23.3, 22.1; IR (KBr): v 3502, 2953, 2916,
1668, 1554, 1400, 1288, 1138, 1012, 746, 657 cm−1; HRMS calcd for
C15H18O3Na [M + Na+]: 269.1154, found: 269.1158.
1-(2-Furanyl)-3-hydroxyhexan-1-one (4ab). Procedure B: (6.00 g
1
of 4a was used and 2.70 g was recovered); 3.77 g, 69% yield; oil; H
NMR (600 MHz, CDCl3): δ 7.61 (d, J = 2.5 Hz, 1H), 7.23 (s, 1H),
6.57−6.54 (m, 1H), 4.20 (s, 1H), 3.04 (d, J = 17.0 Hz, 1H), 2.91 (ddd,
J = 17.0, 9.2, 2.3 Hz, 1H), 1.58−1.41 (m, 4H), 0.97−0.93 (m, 3H);
13C NMR (151 MHz, CDCl3): δ 188.7, 152.4, 146.8, 117.9, 112.2,
67.4, 45.2, 38.8, 18.5, 13.7; IR (KBr): v 3443, 3132, 2961, 2931, 2872,
1666, 1568, 1467, 1395, 1016, 768 cm−1; HRMS calcd for
C10H14O3Na [M + Na+]: 205.0841, found: 205.0846.
(S,2E,4Z)-4,6-Bis(benzyloxy)-1-cyclopropyl-7-hydroxyhepta-2,4-
1
dien-1-one (5aa). Procedure C: 371 mg, 98% yield; syrup; H NMR
3-Hydroxy-4-methyl-1-(2-thiophenyl)pentan-1-one (4ba). Proce-
(600 MHz, CDCl3): δ 7.39−7.26 (m, 10H), 7.03 (d, J = 15.7 Hz, 1H),
6.58 (d, J = 15.7 Hz, 1H), 5.44 (d, J = 9.2 Hz, 1H), 4.81 (d, J = 11.4
Hz, 1H), 4.75 (d, J = 11.5 Hz, 1H), 4.48 (d, J = 11.6 Hz, 1H), 4.36
(ddd, J = 9.5, 7.3, 3.8 Hz, 1H), 4.26 (d, J = 11.6 Hz, 1H), 3.45−3.37
(m, 2H), 2.16−2.12 (m, 2H), 1.14 (dt, J = 7.3, 3.5 Hz, 2H), 0.99−0.95
(m, 2H); 13C NMR (151 MHz, CDCl3): δ 200.1, 154.8, 138.1, 136.9,
136.5, 128.7, 128.53, 128.46, 128.4, 128.0, 127.8, 127.4, 124.9, 74.4, 74.3,
70.8, 64.7, 20.2, 11.7; IR (KBr): v 3450, 3062, 3031, 2923, 2871, 1674,
1645, 1599, 1496, 1452, 1390, 1207, 1181, 1082, 1027, 739, 699 cm−1;
HRMS calcd for C24H26O4Na [M + Na+]: 401.1723, found: 401.1721.
(2E,4Z,6S,7R)-4,6,8-Tris(benzyloxy)-1-cyclopropyl-7-hydroxyocta-
dure B: (6.00 g of 4b was used and 0.78 g was recovered); 6.24 g, 76%
1
yield; oil; H NMR (600 MHz, CDCl3): δ 7.75 (dd, J = 3.7, 1.0 Hz,
1H), 7.69−7.67 (m, 1H), 7.16−7.14 (m, 1H), 3.99−3.97 (m, 1H),
3.19 (s, 1H), 3.11 (dt, J = 16.8, 2.4 Hz, 1H), 2.99 (ddd, J = 16.8, 9.6,
1.4 Hz, 1H), 1.82−1.77(m, 1H), 1.01 (dd, J = 6.8, 2.2 Hz, 3H), 0.99
(dd, J = 6.8, 2.1 Hz, 3H); 13C NMR (151 MHz, CDCl3): δ 193.5,
144.2, 134.2, 132.8, 128.3, 72.5, 43.0, 33.3, 18.5, 17.6; IR (KBr): v
3470, 3094, 2962, 1653, 1517, 1415, 1233, 1059, 727 cm−1; HRMS
calcd for C10H14O2SNa [M + Na+]: 221.0612, found: 221.0618.
3-Hydroxy-1-(2-thiophenyl)hexan-1-one (4bb). Procedure B:
(20.00 g of 4b was used and 9.81 g recovered); 10.10 g, 63%; oil;
1H NMR (600 MHz, CDCl3): δ 7.74 (s, 1H), 7.68 (d, J = 3.0 Hz, 1H),
7.15 (d, J = 2.6 Hz, 1H), 4.22 (s, 1H), 3.21 (s, 1H), 3.11 (d, J = 17.0
Hz, 1H), 3.00 (dd, J = 17.0, 9.1 Hz, 1H), 1.61−1.41 (m, 4H), 0.96
(t, J = 6.7 Hz, 3H); 13C NMR (151 MHz, CDCl3): δ 193.6, 144.1,
1
2,4-dien-1-one (5ab). Procedure C: 484 mg, 97% yield; syrup; H
NMR (600 MHz, CDCl3): δ 7.36−7.25 (m, 15H), 7.08 (d, J = 15.8
Hz, 1H), 6.57 (d, J = 15.7 Hz, 1H), 5.57 (d, J = 9.5 Hz, 1H), 4.77 (d,
J = 11.8 Hz, 1H), 4.75 (d, J = 11.8 Hz, 1H), 4.49 (s, 2H), 4.46 (d, J =
11.8 Hz, 1H), 4.43 (dd, J = 9.6, 5.8 Hz, 1H), 4.24 (d, J = 11.8 Hz, 1H),
2251
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254

The Journal of Organic Chemistry
Article
3.88 (p, J = 4.7 Hz, 1H), 3.54 (dd, J = 9.7, 4.0 Hz, 1H), 3.50 (dd, J =
9.7, 6.1 Hz, 1H), 2.41 (d, J = 4.8 Hz, 1H), 2.16−2.12 (m, 1H), 1.15−
1.12 (m, 2H), 0.99−0.96 (m, 2H); 13C NMR (151 MHz, CDCl3): δ
200.1, 155.8, 138.1, 138.0, 137.1, 136.8, 128.6, 128.5, 128.4, 128.3,
128.2, 128.0, 127.83, 127.79, 127.7, 127.4, 124.7, 74.5, 73.7, 73.4, 72.2,
70.9, 70.6, 20.0, 11.7; IR (KBr): v 3458, 3063, 3031, 2915, 2867, 1675,
1650, 1599, 1497, 1454, 1389, 1206, 1182, 1084, 1027, 737, 698 cm−1;
HRMS calcd for C32H34O5Na [M + Na+]: 521.2298, found: 521.2298.
(S,5E,7Z)-7,9-Bis(benzyloxy)-10-hydroxy-2-methyldeca-5,7-dien-
(s, 1H), 6.80 (dd, J = 8.5, 2.5 Hz, 1H), 6.74 (d, J = 2.3 Hz, 1H), 5.22
(d, J = 8.8 Hz, 1H), 5.03 (s, 2H), 4.85 (d, J = 11.7 Hz, 1H), 4.67
(d, J = 11.4 Hz, 1H), 4.43 (ddd, J = 8.6, 7.0, 4.6 Hz, 1H), 4.36 (d, J =
11.6 Hz, 1H), 4.14 (d, J = 11.6 Hz, 1H), 3.53−3.51 (m, 1H), 2.89−2.85
(m, 3H), 2.44−2.40 (m, 1H), 2.31−2.24 (m, 2H), 2.18 (s, 1H), 2.07−
2.04 (m, 1H), 1.90−1.88 (m, 1H), 1.66−1.39 (m, 6H), 0.94 (s, 3H); 13C
NMR (151 MHz, CDCl3): δ 209.0, 157.0, 154.2, 138.5, 138.4, 137.8,
137.3, 136.6, 132.3, 128.70, 128.67, 128.61, 128.57, 128.5, 128.0, 127.8,
127.7, 127.6, 127.0, 126.4, 120.8, 115.0, 112.5, 75.1, 73.4, 70.8, 70.0, 65.0,
48.2, 48.0, 44.1, 37.9, 31.7, 29.7, 29.0, 26.8, 26.0, 14.6; IR (KBr): v 3552,
3343, 3063, 3032, 2929, 2858, 1716, 1646, 1629, 1499, 1454, 1228, 1085,
1047, 1013, 750, 730 cm−1; HRMS calcd for C44H46O5Na [M + Na+]:
677.3243, found: 677.3247.
1
4-one (5ba). Procedure C: syrup; 387 mg, 98% yield; H NMR (600
MHz, CDCl3): δ 7.39−7.26 (m, 10H), 6.97 (d, J = 15.8 Hz, 1H), 6.43
(d, J = 15.8 Hz, 1H), 5.44 (d, J = 9.2 Hz, 1H), 4.78 (d, J = 11.4 Hz,
1H), 4.72 (d, J = 11.4 Hz, 1H), 4.48 (d, J = 11.6 Hz, 1H), 4.35 (ddd,
J = 9.3, 7.2, 3.9 Hz, 1H), 4.26 (d, J = 11.6 Hz, 1H), 3.44 (dd, J = 11.5,
7.1 Hz, 1H), 3.40 (dd, J = 11.4, 3.5 Hz, 1H), 2.45 (d, J = 7.0 Hz, 2H),
2.21−2.14 (m, 1H), 0.96 (d, J = 6.6 Hz, 1H); 13C NMR (151 MHz,
CDCl3): δ 200.2, 154.8, 138.1, 137.2, 136.5, 128.7, 128.53, 128.45,
128.4, 128.0, 127.8, 127.6, 125.0, 74.42, 74.41, 70.8, 64.7, 50.3, 25.1,
22.7; IR (KBr): v 3445, 3063, 3032, 2957, 2929, 2871, 1685, 1658,
1631, 1600, 1496, 1456, 1295, 1091, 1057, 739, 698 cm−1; HRMS
calcd for C25H30O4Na [M + Na+]: 417.2042, found: 417.2042.
(5E,7Z,9S,10R)-7,9,11-Tris(benzyloxy)-10-hydroxy-2-methylunde-
ca-5,7-dien-4-one (5bb). Procedure C: 510 mg, 99% yield; syrup; 1H
NMR (600 MHz, CDCl3): δ 7.36−7.24 (m, 15 H), 7.00 (d, J = 15.8
Hz, 1H), 6.42 (d, J = 15.8 Hz, 1H), 5.56 (d, J = 9.6 Hz, 1H), 4.74 (d,
J = 11.6 Hz, 1H), 4.72 (d, J = 11.6 Hz, 1H), 4.48 (s, 2H), 4.46 (d, J =
11.8 Hz, 1H), 4.42 (dd, J = 9.5, 5.8 Hz, 1H), 4.24 (d, J = 11.8 Hz, 1H),
3.91−3.85 (m, 1H), 3.54 (dd, J = 9.7, 4.1 Hz, 1H), 3.50 (dd, J = 9.7,
6.1 Hz, 1H), 2.45 (d, J = 6.9 Hz, 2H), 2.21−2.14 (m, 1H), 0.95 (d, J =
6.6 Hz, 6H); 13C NMR (151 MHz, CDCl3): δ 200.3, 155.7, 138.2,
138.0, 137.6, 136.8, 128.7, 128.5, 128.42, 128.35, 128.2, 128.0, 127.84,
127.80, 127.75, 127.0, 124.8, 74.6, 73.7, 73.4, 72.2, 70.9, 70.7, 50.2,
25.2, 22.8; IR (KBr): v 3444, 3063, 3032, 2956, 2926, 2878, 1685,
1660, 1599, 1496, 1455, 1365, 1297, 1204, 1063, 1026, 739, 698 cm−1;
HRMS calcd for C33H38O5Na [M + Na+]: 537.2617, found: 537.2617.
(16E)-16-((S,Z)-2,4-Bis(benzyloxy)-5-hydroxypent-2-enylidene)-
3β-hydroxy-androst-5-en-17-one (5ca). Procedure D: 373 mg, 64%
(E)-16-((4S,5R,Z)-2,4,6-Tris(benzyloxy)-5-hydroxyhex-2-enyli-
dene)-O-benzyl-estrone (5db). Procedure D: 473 mg, 61% yield;
1
white powder; H NMR (600 MHz, CDCl3): δ 7.44−7.22 (m, 21H),
6.99 (s, 1H), 6.80 (d, J = 7.8 Hz, 1H), 6.74 (s, 1H), 5.34 (d, J = 8.9
Hz, 1H), 5.04 (s, 2H), 4.86 (d, J = 11.6 Hz, 1H), 4.65 (d, J = 11.5 Hz,
1H), 4.52 (s, 2H), 4.48−4.45 (m, 1H), 4.32 (d, J = 11.5 Hz, 1H), 4.12
(d, J = 11.4 Hz, 1H), 3.93 (s, 1H), 3.59−3.54 (m, 2H), 2.85 (s, 2H),
2.87 (s, 1H), 2.47−2.42 (m, 2H), 2.30−2.25 (m, 2H), 2.06 (d, J = 8.8
Hz, 1H), 1.87 (d, J = 11.3 Hz, 1H), 1.68−1.38 (m, 6H), 0.94 (s, 3H);
13C NMR (151 MHz, CDCl3): δ 209.0, 157.0, 154.8, 138.54, 138.50,
138.3, 137.8, 137.4, 136.9, 132.4, 128.73, 128.71, 128.6, 128.51, 128.45,
128.1, 128.0, 127.90, 127.86, 127.82, 127.76, 127.6, 127.0, 126.5, 120.6,
115.1, 112.6, 74.5, 73.5, 73.4, 72.7, 71.2, 70.6, 70.0, 48.2, 48.1, 44.1, 37.9,
31.8, 29.8, 29.1, 26.9, 26.1, 14.6; IR (KBr): v 3446, 3062, 3031, 2927, 2863,
1717, 1611, 1498, 1454, 1252, 1231, 1082, 1021, 910, 735, 698 cm−1;
HRMS calcd for C52H54O6Na [M + Na+]: 797.3813, found: 797.3813.
(S,Z)-3-(1,3-Bis(benzyloxy)-4-hydroxybut-1-enyl)-1,5-diphenyl-
pentane-1,5-dione (5ea). Procedure C: 519 mg, 97% yield; syrup; 1H
NMR (600 MHz, CDCl3): δ 7.97 (t, J = 7.2 Hz, 4H), 7.57 (t, J = 7.3
Hz, 2H), 7.46 (t, J = 7.7 Hz, 4H), 7.35−7.21 (m, 10H), 4.84 (d, J =
11.8 Hz, 1H), 4.81 (d, J = 11.8 Hz, 1H), 4.60 (d, J = 9.0 Hz, 1H),
4.42−4.39 (m, 2H), 4.19 (d, J = 11.7 Hz, 1H), 3.82 (p, J = 6.8 Hz,
1H), 3.42 (ddd, J = 12.0, 7.3, 5.0 Hz, 1H), 3.36 (ddd, J = 11.6, 7.9, 3.9
Hz, 1H), 3.30−3.20 (m, 4H), 2.18 (dd, J = 7.8, 5.1 Hz, 1H); 13C NMR
(151 MHz, CDCl3): δ 198.74, 198.68, 160.7, 138.6, 137.2, 136.9,
133.5, 133.4, 128.82, 128.80, 128.6, 128.4, 128.27, 128.26, 128.11,
128.08, 128.0, 127.6, 108.6, 74.2, 72.3, 70.0, 65.3, 41.9, 41.7, 33.8; IR
(KBr): v = 3492, 3062, 3032, 2919, 2870, 1681, 1598, 1450, 1391,
1277, 1215, 1155, 1056, 752, 695 cm−1; HRMS of 5ea + 4H obtained
from the reduction of 5ea using NaBH4 in methanol: calcd for
C35H38O5Na [M + Na+]: 561.2611; found: 561.2610.
3-((3S,4R,Z)-1,3,5-Tris(benzyloxy)-4-hydroxypent-1-enyl)-1,5-di-
phenylpentane-1,5-dione (5eb). Procedure C: 650 mg, 99% yield;
syrup; 1H NMR (600 MHz, CDCl3): δ 7.98−7.95 (m, 4H), 7.58−7.55
(m, 2H), 7.47−7.44 (m, 4H), 7.33−7.16 (m, 15H), 4.83 (d, J = 11.5 Hz,
1H), 4.80 (d, J = 11.5 Hz, 1H), 4.75 (d, J = 9.3 Hz, 1H), 4.50−4.45 (m,
2H), 4.42 (dd, J = 8.8, 5.6 Hz, 1H), 4.38 (d, J = 11.9 Hz, 1H), 4.17 (d, J =
11.8 Hz, 1H), 3.84−3.80 (m, 1H), 3.49−3.42 (m, 2H), 3.33−3.19 (m,
4H), 2.46 (s, 1H); 13C NMR (151 MHz, CDCl3): δ 198.73, 198.72, 161.4,
138.7, 138.4, 137.4, 136.9, 133.44, 133.42, 128.8, 128.5, 128.4, 128.33,
128.31, 128.28, 127.99, 127.97, 127.9, 127.8, 127.6, 127.5, 107.8, 73.5, 73.4,
72.8, 72.3, 71.1, 69.9, 42.0, 41.8, 34.0; IR (KBr): v 3430, 3153, 1682, 1631,
1597, 1449, 1400, 1215, 1181, 1023, 1001, 754, 690 cm−1; HRMS calcd for
C43H42O6Na [M + Na+]: 677.2874, found: 677.2876.
1
yield; white powder; H NMR (600 MHz, CDCl3): δ 7.36−7.25 (m,
10H), 6.92 (s, 1H), 5.37 (d, J = 1.8 Hz, 1H), 5.21 (d, J = 8.7 Hz, 1H),
4.83 (d, J = 11.6 Hz, 1H), 4.65 (d, J = 11.6 Hz, 1H), 4.44−4.41 (m,
1H), 4.34 (d, J = 11.5 Hz, 1H), 4.13 (d, J = 11.9 Hz, 1H), 3.56−3.49
(m, 3H), 2.78 (dd, J = 16.4, 6.0 Hz, 1H), 2.33−2.17 (m, 4H), 2.03−
2.95 (m, 2H), 1.05 (s, 3H), 0.93 (s, 3H); 13C NMR (151 MHz, CDCl3):
δ 209.1, 154.0, 141.3, 138.3, 138.2, 136.4, 128.6, 128.52, 128.45, 127.81,
127.76, 127.6, 121.0, 120.7, 75.1, 73.3, 71.3, 70.7, 64.8, 50.2, 49.4, 47.5,
42.1, 37.1, 36.7, 31.5, 31.4, 31.1, 30.8, 29.2, 20.4, 19.5, 14.1; IR (KBr): v
3423, 3031, 2932, 2859, 1717, 1624, 1496, 1455, 1398, 1090, 1058, 738,
698 cm−1; HRMS calcd for C38H46O5Na [M + Na+]: 605.3243, found:
605.3242.
(16E)-16-((4S,5R,Z)-2,4,6-Tris(benzyloxy)-5-hydroxyhex-2-enyli-
dene)-3β-hydroxy-androst-5-en-17-one (5cb). Procedure D: 478 mg,
1
68% yield; white powder; H NMR (600 MHz, CDCl3): δ 7.33−7.26
(m, 13H), 7.21 (d, J = 7.1 Hz, 2H), 6.96 (s, 1H), 5.34 (d, J = 2.3 Hz,
1H), 5.32 (d, J = 9.2 Hz, 1H), 4.83 (d, J = 11.6 Hz, 1H), 4.62 (d, J =
11.6 Hz, 1H), 4.52 (d, J = 11.7 Hz, 1H), 4.50 (d, J = 11.7 Hz, 1H),
4.46 (dd, J = 8.6, 5.6 Hz, 1H), 4.30 (d, J = 11.6 Hz, 1H), 4.10 (d, J =
11.6 Hz, 1H), 3.94−3.90 (m, 1H), 3.57 (dd, J = 9.3, 2.6 Hz, 1H),
3.54−3.48 (m, 2H), 2.76 (dd, J = 16.4, 6.0 Hz, 1H), 2.61 (d, J = 3.1
Hz, 1H), 2.29 (dd, J = 13.2, 4.2 Hz, 1H), 2.25−2.16 (m, 2H), 1.87−
1.82 (m, 3H), 1.03 (s, 3H), 0.92 (s, 3H); 13C NMR (151 MHz,
CDCl3): δ 209.0, 154.7, 141.3, 138.34, 138.33, 138.2, 136.7, 128.6,
128.5, 128.40, 128.36, 128.3, 127.8, 127.74, 127.68, 127.6, 120.7,
120.4, 74.4, 73.4, 73.3, 72.6, 71.4, 71.1, 70.6, 50.3, 49.5, 47.5, 42.1,
37.2, 36.7, 31.6, 31.5, 31.1, 30.9, 29.2, 20.4, 19.5, 14.2; IR (KBr): v
3442, 3063, 3031, 2932, 2860, 1716, 1627, 1496, 1455, 1376, 1090,
1025, 910, 733, 698 cm−1; HRMS calcd for C46H54O6 [M + Na+]:
725.3818, found: 725.3817.
(S,Z)-3-(1,3-Bis(benzyloxy)-4-hydroxybut-1-enyl)-1,5-bis(4-
fluorophenyl)pentane-1,5-dione (5fa). Procedure C: 564 mg, 99%
1
yield; syrup; H NMR (600 MHz, CDCl3): δ 8.05−7.97 (m, 4H),
7.35−7.19 (m, 10H), 7.14−7.11 (m, 4H), 4.84 (d, J = 11.6 Hz, 1H),
4.82 (d, J = 11.6 Hz, 1H), 4.60 (d, J = 9.0 Hz, 1H), 4.44−4.38 (m,
2H), 4.21 (d, J = 11.7 Hz, 1H), 3.77 (p, J = 6.8 Hz, 1H), 3.43 (dd, J =
11.2, 7.4 Hz, 1H), 3.38 (dd, J = 11.3, 4.0 Hz, 1H), 3.24−3.17 (m, 4H),
2.18 (s, 1H); 13C NMR (151 MHz, CDCl3): δ 197.1, 197.0, 165.90 (d,
1
1JCF = 255.1 Hz), 165.89 (d, JCF = 255.1 Hz), 160.5, 138.5, 137.1,
133.22 (d, 4JCF = 2.6 Hz), 133.21 (d, 4JCF = 2.6 Hz), 130.91 (d, 3JCF
=
3
9.3 Hz), 130.88 (d, JCF = 9.3 Hz,), 128.6, 128.4, 128.1, 128.0, 127.9,
(E)-16-((S,Z)-2,4-Bis(benzyloxy)-5-hydroxypent-2-enylidene)-O-
2
benzyl-estrone (5da). Procedure D: 380 mg, 58% yield; white
127.6, 115.9 (d, JCF = 21.8 Hz), 108.7, 74.1, 72.4, 70.0, 65.3, 41.7,
1
powder; H NMR (600 MHz, CDCl3): δ 7.36−7.20 (m, 16H), 6.95
41.5, 33.9; IR (KBr): v 3064, 3031, 2919, 2865, 1682, 1597, 1504,
2252
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254

The Journal of Organic Chemistry
Article
1453, 1231, 1156, 1089, 1068, 838, 739, 698 cm−1; HRMS of 5fa + 4H
obtained from the reduction of 5fa using NaBH4 in methanol: calcd
for C35H36F2O5Na [M + Na+]: 597.2423; found: 597.2427.
temperature or at reflux. For DMF-mediated reaction, no aldol product
was formed in 8 h with M2CO3; the starting material 3g decomposed
completely in 8 h at room temperature or in 3 h at 40−45 °C with MOH.
Organic Solvent-Mediated Aldol Reactions of Heteroaro-
matic Ethanones with Aliphatic Aldehydes. A mixture of
heteroaromatic ethanone (4a−4c, 200 mg), butyraldehyde or
isobutyraldehyde (2.0 equiv), base (1.0 equiv), and organic solvent
(5 mL) was magnetically stirred (400 rmp) at 0 °C or room
temperature for 8 h. The organic solvents used include methanol,
DMF, and CHCl3. The base was NaOH, K2CO3, Cs2CO3, or DBU.
For K2CO3-catalyzed or CHCl3-mediated reactions, no desired aldol
products were formed. A stronger base (Cs2CO3, NaOH or DBU)
gave only a trace amount of β-hydroxyketones in 8 h in methanol or in
DMF. For the reaction of 4b and excess isobutyraldehyde (5.0 equiv)
in methanol, a longer reaction time (24 h) also ended in a poor
conversion and gave complicated products.
A mixture of 3i (200 mg), isovaleraldehyde (2.0 equiv), LiOH
(1.0 equiv), and methanol (5 mL) was magnetically stirred (400 rmp)
at 0 °C or room temperature for 1 h. TLC indicated that complicated
products (at least eleven products) were formed with a poor
conversion of 3i and there were not major products.
Organic Solvent-Mediated Condensation of Acetophenone
and O-Benzyl-Protected D-Glucosyl Hemiacetal. A mixture of
acetophenone (180 mg), O-benzyl-protected D-glucosyl hemiacetal
(135 mg), base (2.0 equiv), TBAB (0 mg or 40 mg), and organic
solvent (methanol or CHCl3, 2.5 mL) was magnetically stirred (400 rmp)
at reflux for 8 h. The bases used include M2CO3, MOH (M: Li, Na,
and K), and DBU. For CHCl3-mediated or M2CO3-catalyzed
reactions, no reaction took place. For methanol-mediated reactions
catalyzed by MOH or DBU, the desired product 5eb was not formed.
1,5-Bis(4-fluorophenyl)-3-((3S,4R,Z)-1,3,5-tris(benzyloxy)-4-hy-
droxypent-1-enyl)pentane-1,5-dione (5fb). Procedure C: 687 mg,
99% yield; syrup; 1H NMR (600 MHz, CDCl3): δ 7.97−7.80 (m, 4H),
7.30−7.17 (m, 15H), 7.13−7.09 (m, 4H), 4.83 (d, J = 11.5 Hz, 1H),
4.80 (d, J = 11.5 Hz, 1H), 4.74 (d, J = 9.4 Hz, 1H), 4.49 (d, J = 11.9 Hz,
1H), 4.47 (d, J = 11.9 Hz, 1H), 4.43 (dd, J = 9.4, 5.5 Hz, 1H), 4.38 (d, J =
11.9 Hz, 1H), 4.18 (d, J = 11.9 Hz, 1H), 3.84−3.80 (m, 1H), 3.79−3.74
(m, 1H), 3.49 (dd, J = 9.8, 3.7 Hz, 1H), 3.44 (dd, J = 9.8, 6.4 Hz, 1H),
3.26−3.14 (m, 4H), 2.49 (d, J = 3.4 Hz, 1H); 13C NMR (151 MHz,
CDCl3): δ 197.14, 197.13, 165.9 (d, 1JCF = 254.8 Hz), 161.2, 138.7, 138.4,
3
3
137.4, 133.3, 131.00 (d, JCF = 9.2 Hz), 130.97 (d, JCF = 9.2 Hz), 128.5,
128.43, 128.36, 128.0, 127.9, 127.8, 127.7, 127.6, 115.9 (d, 2JCF = 21.8 Hz),
108.0, 73.6, 73.4, 72.7, 72.5, 71.2, 69.9, 41.8, 41.7, 34.2; IR (KBr): v 3065,
3032, 2907, 2867, 1683, 1597, 1504, 1453, 1231, 1157, 1090, 1068, 838,
739, 699 cm−1; HRMS calcd for C43H40F2O6Na [M + Na+]: 713.2691,
found: 713.2685.
Stereochemistry for 5aa−5fb. The configurations of the
conjugated diene or enolether groups for 5aa−5fb were indicated by
the NOESY spectra.
Recycling Procedures for the Aqueous Reactions for 1cc. A
mixture of 1c (1 g), Aliquat 336 (10 mol %), p-methoxybenzaldehyde
(1.05 equiv), Na2CO3 (0.8 equiv), PTFE sand (5 g), and water
(10 mL) was mechanically stirred at 80 °C for 2.5 h. After TLC
indicated completion of the reaction, the suspension in water was
filtrated to gave crude product 1cc, leaving the PTFE sand in the flask.
After crystallization in aqueous acetone (6 mL, 75% v/v), 96% yield of
1cc was obtained. The mother liquor was concentrated and combined
with water from the previous pot, to which were again added 1c (1 g)
and p-methoxybenzaldehyde (1.05 equiv). The mixture was treated as
in the first pot. This is the second cycle. In this manner, the reaction
was cycled from the third to the eighth. The yields were quantitative
starting from the second cycle. The durations extended from 2.5 to 4 h
from first to eighth cycles.
Recycling Procedures for the Aqueous Reactions for 4ba.
The recycling procedure for the aqueous reaction of 4b (2.00 g) with
isobutyraldehyde (Table 4, entry 3) was conducted according to
procedure B. After direct in-flask extraction with ethyl acetate (2 × 5 mL),
the aqueous phase was directly reused for the next aldol event for three
times. The yields of 4ba were 1.92 g (69%), 2.31 g (78%), 2.04 g (72%),
and 2.13 g (75%). The amounts of recovered starting material were 217,
105, 203, and 192 mg. The average yield was 2.10 g, 73%, close to that in
Table 4 (76%).
ASSOCIATED CONTENT
* Supporting Information
■
S
The modification of the standard two-blade stirring rod. Copies
of 1H NMR, 13C NMR and NOESY spectra for new
compounds. This material is available free of charge via the
Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: lichunbao@tju.edu.cn. Fax: (+86) 2227403475.
■
Notes
The authors declare no competing financial interest.
Recycling Procedures for the Aqueous Reactions for 5bb.
The recycling procedure for the aqueous reaction for 5bb (Table 5,
entry 4) was a direct in-flask extraction one, according to procedure C.
The aqueous phase was recycled three times. All three aldol events
were completed in 15 min and in quantitative yields.
Organic Solvent-Mediated Aldol Reactions for 1a and 1b. A
mixture of 1a (158 mg) or 1b (165 mg), 4-methoxybenzaldehyde
(71 mg, 1.05 equiv), MOH (M: Li or Na, 2.0 equiv), and DMF
(4 mL) or THF-water (3:1, 4 mL) was magnetically stirred (400 rmp)
at room temperature. TLC indicated that no reaction took place
in DMF. For both 1a and 1b, the reaction times were the same in
THF-water (3.5 h for NaOH and 6 h for LiOH).
Organic Solvent-Mediated Aldol Reactions of Ketone with a
Base-Liable Group Epoxyketone. A mixture of 3g (200 mg),
aldehyde (1.05 equiv for benzaldehyde, 2.0 equiv for isovaleralde-
hyde), K2CO3 (138 mg, 1.0 equiv), and methanol (4 mL) was
magnetically stirred (400 rmp) at room temperature for 6 h. TLC
indicated that no reaction took place. Another carbonate, Li2CO3 or
Na2CO3, gave the same result. When the reaction was catalyzed by
NaOH (1.0 equiv) at 10 °C in methanol, no desired product was
formed in 1 h and most of 3g decomposed in 8 h. When the reaction
temperature was 40−45 °C, the decomposition took only 2 h. In other
organic solvents (DMF or CHCl3), this reaction catalyzed by M2CO3 or
MOH (M: Li, Na, and K) also failed completely. For CHCl3-mediated
reaction, no desired product 3gb or 3gc was observed in 8 h at room
REFERENCES
■
(1) For comprehensive reviews, see: Modern Aldol reactions;
Mahrwald, R., Ed.; Wiley-VCH: Weinheim, Germany, 2004.
(2) (a) Cui, X.; Li, B.; Liu, T.; Li, C. Green Chem. 2012, 14, 668−672.
(b) He, G.; Li, B.; Li, C. J. Agric. Food Chem. 2013, 61, 2913−2918.
(3) Ikegami, S.; Ohishi, J.; Akaboshi, S. Chem. Pharm. Bull. 1975, 23,
2701−2710.
(4) (a) Narayan, S.; Muldoon, J.; Finn, M. G.; Fokin, V. V.; Kolb, H.
C.; Sharpless, K. B. Angew. Chem., Int. Ed. 2005, 44, 3275−3279.
(b) Butler, R. N.; Coyne, A. G. Chem. Rev. 2010, 110, 6302−6337.
(c) Beattie, J. K.; McErlean, C. S. P.; Phippen, C. B. W. Chem.Eur. J.
2010, 16, 8972−8974. (d) Li, C.-J. Chem. Rev. 2005, 105, 3095−3165.
(e) Chanda, A.; Fokin, V. V. Chem. Rev. 2009, 109, 725−748. (f) Jung,
Y.; Marcus, R. A. J. Am. Chem. Soc. 2007, 129, 5492−5502.
(5) (a) Butler, R. N.; Coyne, A. G.; Moloney, E. M. Tetrahedron Lett.
2007, 48, 3501−3503. (b) Badone, D.; Baroni, M.; Cardamone, R.;
Ielmini, A.; Guzzi, U. J. Org. Chem. 1997, 62, 7170−7173.
(6) For examples, see: (a) Paquette, L. A.; Wang, T-Z; Vo, N. H. J.
Am. Chem. Soc. 1993, 115, 1676−1683. (b) Lau, S. Y. W. Org. Lett.
2011, 13, 347−349. (c) Hong, B.-C.; Hsu, C.-S.; Lee, G.-H. Chem.
Commun. 2012, 48, 2385−2387. (d) Davies, J. S.; Higginbotham, C.
L.; Tremeer, E. J.; Brown, C.; Treadgold, R. C. J. Chem. Soc., Perkin
Trans. 1 1992, 3043−3048. (e) You, Y.-J.; Kim, Y.; Nam, N.-H.; Ahn, B.-
́
Z. Bioorg. Med. Chem. Lett. 2003, 13, 3137−3140. (f) Djurendic, E. A.;
2253
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254

The Journal of Organic Chemistry
Article
Ajdukovic,
́ ̌ ́ ́ ́
J. J.; Sakac, M. N.; Csanadi, J. J.; Kojic, V. V.; Bogdanovic, G. M.;
Gasi, K. M. P. Eur. J. Med. Chem. 2012, 54, 784−792. (g) Hurst, D. T.;
̌
McInnes, A. G. Can. J. Chem. 1965, 43, 2004−2011.
(7) (a) Menche, D.; Arikan, F.; Li, J.; Rudolph, S. Org. Lett. 2007, 9,
267−270. (b) Abed, H. B.; Mammoliti, O.; Bande, O.; Lommen, G.
V.; Herdewijn, P. J. Org. Chem. 2013, 78, 7845−7858. (c) Blay, G.;
́
Fernandez, I.; Munoz, M. C.; Pedro, J. R.; Vila, C. Eur. J. Org. Chem.
̃
2013, 1902−1907. (d) Liu, R.; Li, Z.; Zhu, H.; Sun, W. Inorg. Chim.
Acta 2012, 387, 383−389. (e) Molleti, N.; Rana, N. K.; Singh, V. K.
Org. Lett. 2012, 14, 4322−4325. (f) Trost, B. M.; Ito, H. J . Am. Chem.
Soc. 2000, 122, 12003−12004. (g) Trost, B. M.; Yeh, V. S. C. Org. Lett.
2002, 4, 3513−3516. (h) Crawford, C.; Nelson, A.; Patel, I. Org. Lett.
2006, 8, 4231−4234. (i) Singh, P. K.; Singh, V. K. Org. Lett. 2010, 12,
80−83. (j) Dodd, K.; Morton, D.; Worden, S.; Narquizian, R.; Nelson,
A. Chem.Eur. J. 2007, 13, 5857−5861. (k) Nagafuji, P.; Cushman,
M. J. Org. Chem. 1996, 61, 4999−5003.
(8) Richard, F.; Carreyre, H.; Coustard, J. M.; Bachmann, C.; Perot,
G. Tetrahedron 1998, 54, 14757−14766.
(9) (a) Casiraghi, G.; Zanardi, F. Chem. Rev. 1995, 95, 1677−1716.
(b) Nicolaou, K. C.; Mitchell, H. J. Angew. Chem., Int. Ed. 2001, 40,
1576−1624. (c) Reddy, L. V. R.; Kumar, V.; Sagar, R.; Shaw, A. K.
Chem. Rev. 2013, 113, 3605−3631. (d) Wang, C.-C.; Lee, J.-C.; Luo,
S.-Y.; Kulkarni, S. S.; Huang, Y.-W.; Lee, C.-C.; Chang, K.-L.; Hung,
S.-C. Nature 2007, 446, 896−899. (e) Romeo, G.; Chiacchio, U.;
Corsaro, A.; Merino, P. Chem. Rev. 2010, 110, 3337−3370.
(10) (a) Calvo-Mateo, A.; Camarasa, M.-J.; Diaz-Ortiz, A.; De las
Heras, F. G.; Alemany, A. J. Chem. Soc., Pekin Trans. I 1988, 2861−
2863. (b) Anastasia, M.; Allevi, P.; Ciuffreda, P.; Fiecchi, A.; Scala, A. J.
Org. Chem. 1991, 56, 3054−3058.
(11) Winchester, B. G. Tetrahedron: Asymmetry 2009, 20, 645−651.
(12) Banday, A. H.; Zargar, M. I.; Ganaie, B. A. Steroids 2011, 76,
1358−1362.
(13) Dubey, S.; Jindal, D. P.; Piplani, P. Indian J. Chem. B 2005, 44,
2126−2137.
(14) Huang, L. H.; Zheng, Y. F.; Song, C. J.; Wang, Y. G.; Xie, Z. Y.;
Lai, Y. W.; Lu, Y. Z.; Liu, H. M. Steroids 2012, 77, 710−715.
́ ́ ́ ́
(15) Stefanovic, M.; Miljkovic, D.; Miljkovic, M.; Jokic, A.;
Stipanovic, B. Tetrahedron Lett. 1966, 7, 3891−3895.
(16) Dory, I.; Lanyi, G. Acta Chim. Acad. Sci. Hung. 1962, 30, 71−75.
2254
dx.doi.org/10.1021/jo500213b | J. Org. Chem. 2014, 79, 2242−2254