Reactions of diazo ketones with activated unsaturated compounds in the presence of gallium trichloride

Article abstract of DOI:10.1007/s11172-014-0444-7

Diazoacetone reacts with methyl acrylate in the presence of anhydrous GaCl₃ to give isomeric methyl 2-acetylcyclopropanecarboxylates rather than pyrazolines obtained from diazo esters or by noncatalytic reactions. In a similar reaction, diazoacetophenone yields methyl 2-benzoylcyclopropanecarboxylates, benzoylmethyl acrylate, and benzoylmethyl 2-benzoylcyclopropanecarboxylate via partial transesterification. Addition of an equimolar amount of GaCl₃ to diazoacetone in the system CH₂Cl₂-HCl-H₂O unexpectedly produces 4,5-dimethylfuran-3(2H)-one and 1,1'-oxybis(propan-2-one).

Full text of DOI:10.1007/s11172-014-0444-7

Russian Chemical Bulletin, International Edition, Vol. 63, No. 2, pp. 404—408, February, 2014
404
Reactions of diazo ketones with activated
unsaturated compounds in the presence of gallium trichloride*
R. A. Novikov, Yu. V. Tomilov, and O. M. Nefedov
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 6390. Eꢀmail: tom@ioc.ac.ru
Diazoacetone reacts with methyl acrylate in the presence of anhydrous GaCl3 to give
isomeric methyl 2ꢀacetylcyclopropanecarboxylates rather than pyrazolines obtained from diazo
esters or by noncatalytic reactions. In a similar reaction, diazoacetophenone yields methyl
2ꢀbenzoylcyclopropanecarboxylates, benzoylmethyl acrylate, and benzoylmethyl 2ꢀbenzoylꢀ
cyclopropanecarboxylate via partial transesterification. Addition of an equimolar amount of
GaCl3 to diazoacetone in the system CH2Cl2—HCl—H2O unexpectedly produces 4,5ꢀdimethylꢀ
furanꢀ3(2H)ꢀone and 1,1´ꢀoxybis(propanꢀ2ꢀone).
Key words: diazoacetone, diazoacetophenone, cyclopropanes, Lewis acids, transesterificaꢀ
tion, gallium trichloride.
1,3ꢀDipolar cycloaddition to unsaturated compounds
pattern. Isomerization of primary 1ꢀpyrazolines leads to
2ꢀpyrazolines 3a,b, in which the double bond is conjugatꢀ
ed with the keto group (Scheme 1).
is a common reaction of aliphatic diazo compounds. Alkꢀ
enes normally yield 1ꢀ or 2ꢀpyrazolines,1 which can furꢀ
ther be transformed into compounds of other types,2 inꢀ
cluding biologically active ones.3 Except for alkenes conꢀ
taining electronꢀwithdrawing substituents or a strained
double bond, prolonged keeping or heating is mostly
required for these reactions to occur. In some cases,
1,3ꢀdipolar cycloaddition can be promoted by a combinaꢀ
tion of heating with catalysis by pyridine4 or molybdenum
hexacarbonyl.5 Recently,6 we have demonstrated that the
rate of cycloaddition of diazo esters to activated alkenes is
increased by several orders of magnitude in the presence of
some Lewis acids. Specifically, the use of GaCl3 catalyzes
not only 1,3ꢀdipolar cycloaddition but also subsequent
insertion of the electrophilic fragment CHCO2Me of
methyl diazoacetate into the N—H bond of the resulting
2ꢀpyrazolines.
Scheme 1
R = Me (a), Ph (b)
Conditions: 25 C, 3 days.
We tried several Lewis acids (SnCl4, TiCl4, BF3•Et2O,
EtAlCl2, In(OTf)3, Sn(OTf)2, Yb(OTf)3, and Sc(OTf)3)
as catalysts for this reaction. However, they all fell short of the
expected effect observed earlier6 in reactions with diazo
esters. For instance, Sc(OTf)3 and Yb(OTf)3 increase the rate
of the 1,3ꢀdipolar cycloaddition of diazo esters to acrylꢀ
ates by nearly two orders of magnitude6 but fail with subꢀ
strates 1 and 2. The aforementioned tin, titanium, aluminum,
boron, and indium compounds promptly break down the
starting diazo ketones 1a,b, yet forming no adducts
with acrylates. For instance, compounds 1a,b readily react
with EtAlCl2 to give relatively stable organoaluminum interꢀ
mediates 4a or 4b, which prove to be inert toward an alkene
(Scheme 2). When treated with water or methanol, comꢀ
pounds 4 instantaneously eliminate ethane to give ꢀchloro
ketones 5. That is why these Lewis acids are not very conꢀ
venient for use as catalysts for 1,3ꢀdipolar cycloaddition.
Results and Discussion
In the present work, we studied the effects of Lewis
acids on diazo ketones as well as on their reactions with
activated alkenes. Under normal conditions with no Lewis
acids employed, diazoacetone (1a) and diazoacetophenꢀ
one (1b) slowly and regioselectively react with methyl
acrylate (2) according to the 1,3ꢀdipolar cycloaddition
* On the occasion of the 80th anniversary of the N. D. Zelinsky
Institute of Organic Chemistry of the Russian Academy of
Sciences.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 0404—0408, February, 2014.
1066ꢀ5285/14/6302ꢀ0404 © 2014 Springer Science+Business Media, Inc.

GaCl3 promoted reactions of diazo ketones
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 2, February, 2014
405
Scheme 2
An intermediate complex of hydroxyacetone with
GaCl3 (A), which is formed by partial hydration of comꢀ
pound 1a, seems to be crucial for the formation of furanꢀ
3(2H)ꢀone 6 and ether 7. Intermediate A attacked by
a second diazoacetone molecule on the hydroxy group is
transformed into compound 7, while an attack on the
carbonyl group of A followed by migration of the methyl
group and elimination of water gives furanone 6 (Scheme 4).
Unlike diazoacetone, diazoacetophenone 1b does
not undergo such transformations: its reaction with
GaCl3 in both the presence and in the absence of water
promptly gives chloroacetophenone 5b in high yield (see
Scheme 2), the process being even promoted by the presꢀ
ence of water.
iii
Reagents and conditions: i. EtAlCl2, 1 min, CH2Cl2/hexane;
ii. MeOY or Y2O (Y = H, D); iii. GaCl3 (H2O), CH2Cl2, 5 min.
R = Me (a), Ph (b)
Nevertheless, gallium trichloride is the only Lewis acid
that favors reactions of diazo ketones 1a,b with unsaturatꢀ
ed compounds (specifically, with methyl acrylate). As opꢀ
posed to their noncatalytic transformations, GaCl3ꢀcataꢀ
lyzed reactions proceed quite rapidly, being completed
within 15 min. Unlike diazo esters,6 these diazo ketones
mostly react by eliminating nitrogen gas. A reaction of
diazoacetone with methyl acrylate in the presence of anꢀ
hydrous GaCl3 gives cyclopropane derivative 9a as the
only intermolecular product. This is a 3.5 : 1 mixture of
Eꢀ and Zꢀisomers (Scheme 5). Unfortunately, much of
diazoacetone under these conditions is transformed into
chloroacetone 5a. Since the presence of moisture traces
appreciably increases its fraction, the yield of cycloꢀ
propane 9a is moderate (48—54%) even when the reaction
is carried out in a dry inert environment and a threefold
excess of methyl acrylate is used (Table 1). The reaction
products were isolated by column chromatography on silꢀ
ica gel and identified by 1H and 13C NMR spectroscopy. It
should be noted that cyclopropanes are not formed from
diazo esters in reactions catalyzed by Lewis acids: the
predominant pathway leads to 2ꢀpyrazolines with a multiꢀ
ple increase in the reaction rate.6
Unlike the Lewis acids discussed above, gallium trichlorꢀ
ide behaves in a different way. In the absence of water, GaCl3
slowly decomposes diazoacetone into chloroacetone 5a and
unidentified products. When treating compound 1a with
an equimolar amount of GaCl3 in the system CH2Cl2—
HCl—H2O, we discovered an unusual transformation of
diazoacetone leading to compounds 6 and 7 (Scheme 3).
Scheme 3
Reagents and conditions: GaCl3 in CH2Cl2 and 5% HCl, 5 min.
Scheme 4

406
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 2, February, 2014
Novikov et al.
Table 1. Reaction products obtained from diazo ketones 1a,b
and methyl acrylate (2) in CH2Cl2 in the presence of GaCl3
addition of two diazoacetophenone molecules to methyl
acrylate.
We assumed that the formation of transalkylated esters 11
could be attributed to moisture traces that persist in the
reaction mixture despite great care taken to prevent this.
Indeed, the use of two equivalents of water in the reaction
of diazoacetophenone 1b with compound 2 in the presꢀ
ence of GaCl3 substantially changes the ratio of the products
(see Table 1). Strange as it may seem, derivative 11 beꢀ
comes a major product when an excess of methyl acrylate
is used and so does compound 12 in the reaction with an
excess of the diazo ketone, although the formation of prodꢀ
uct 12 results from transesterification of methyl acrylate.
Compounds 11 and 12 are both formed by transesteriꢀ
fication of methyl carboxylates with diazoacetophenone
in the presence of gallium derivatives; in the absence of
water, no transesterification occurs. Such processes have
not been documented hitherto. Derivative 11 is a ~4 : 1
mixture of Eꢀ and Zꢀisomers; i.e., its formation is more
selective than that of compound 9b. Apparently, the first
step involves cyclopropanation of methyl acrylate, which
is followed by transesterification of intermediate 9b. The
reaction products can easily be separated by column
chromatography on silica gel. It should be noted that such
processes have not been observed with diazo esters.6
To sum up, we were the first to perform direct cycloꢀ
propanation of methyl acrylate with diazoacetone and
diazoacetophenone in the presence of gallium trichlorꢀ
ide. Previous attempts at this cyclopropanation failed beꢀ
cause such classic catalysts as copper, palladium, and
rhodium derivatives commonly used to decompose diazo
compounds are inefficient or unsuitable at all for cycloꢀ
propanation of electronꢀdeficient alkenes such as methyl
acrylate.
Diazo
ketone
Molar ratio of reagents
Yield (%)
1
2
GaCl3 H2O
9
10 11 12
1a
1a
1b
1b
1b
1b
1
1
1
1
1
3
3
3
3
3
3
1
0.2
1
0.2
1
1
1
—
—
—
—
2
48
54
36
55
25
15
—
—
—
3
—
—
15
10
—
—
—
—
—
—
52 <5
21 46
2
Scheme 5
Reagents and conditions: GaCl3 (H2O), CH2Cl2, 20 C, 15 min.
As with diazoacetone 1a, a reaction of diazoacetophenꢀ
one 1b with excess methyl acrylate in the presence of
anhydrous GaCl3 produces chloroacetophenone and cycloꢀ
propane 9b as a 2.6 : 1 mixture of Eꢀ and Zꢀisomers in 36%
yield (Scheme 6, see Table 1). The use of an equimolar
amount of GaCl3 increases the yield of cyclopropane 9b to
55%. In addition, small amounts of Nꢀalkylated pyrazolꢀ
ine 10 and isomeric 2ꢀbenzoylcyclopropanecarboxylates
11 are detected (see Table 1). Interestingly, while a threeꢀ
fold excess of methyl acrylate (2) is employed, the reacꢀ
tion yields minor products 10 and 11 as a result of the
The main role of GaCl3 consists in its coordination to
the ester group of methyl acrylate, producing reactive comꢀ
plex 13. This complex reacts with diazo ketone 1 prior to
its decomposition by the Lewis acid (Scheme 7). The first
Scheme 6
Reagents and conditions: GaCl3 (H2O); CH2Cl2, 20 C, 15 min.

GaCl3 promoted reactions of diazo ketones
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 2, February, 2014
407
reaction mixture was acidified with 10% HCl to pH 1—2, and
the product was extracted with CH2Cl2 (3×10 mL). The comꢀ
bined organic extracts were dried with MgSO4 and concentrated
in vacuo to give chlorinated ketones 5a or 5b (or their deuterated
analogs). The 1H and 13C NMR spectra of compounds 5a or 5b
agree with the literature data.7—9
reaction intermediate 14 eliminates a nitrogen molecule
so quickly that no cyclization into a pyrazoline ring ocꢀ
curs. (Apparently, similar intermediates formed from diꢀ
azo esters are much more stable, and their cyclization into
pyrazolines is preferred to elimination of N2.6) The elimiꢀ
nation of a nitrogen molecule from compound 14 gives
intermediate 15, which undergoes cyclization into cycloꢀ
propane 9. Note that the formation of an unsaturated comꢀ
pound by possible deprotonation of intermediate 15 was
not observed. In the presence of GaCl3, compounds 1, 2,
and 9, as well as their reaction intermediates, can undergo
alternative transformations (e.g., transesterification and
NH insertion).
Reaction of diazo ketone 1a with GaCl3 in the system CH2Cl2—
HCl—H2O. A solution of GaCl3 (314 mg, 1.78 mmol) in CH2Cl2
(0.5 mL) was added to a stirred solution of diazoacetone 1a
(152 mg, 1.8 mmol) in CH2Cl2 (2.5 mL). This was immediately
followed by addition of 5% HCl (3 mL). The reaction mixture
was vigorously stirred at ~20 C for 5 min until gas evolution
ceased. Organic materials were extracted with CH2Cl2 (3×10 mL).
The combined organic extracts were dried with anhydrous
MgSO4 and concentrated in vacuo. The residue was separated by
column chromatography on silica gel with benzene—AcOEt as
an eluent (gradient elution from 5 : 1 to 1 : 10). All products were
obtained as colorless oils. They included chloroacetone (5a) (34 mg,
20%), 4,5ꢀdimethylfuranꢀ3(2H)ꢀone (6) (35 mg, 34%), 1,1´ꢀoxyꢀ
di(propanꢀ2ꢀone) (7) (36 mg, 31%), and 1ꢀhydroxypropanꢀ2ꢀ
one (8) (10 mg, 8%). The 1H and 13C NMR spectra of comꢀ
pounds 5a, 7, and 8 agree with the literature data.7,8,10,11
4,5ꢀDimethylfuranꢀ3(2H)ꢀone (6). 1H NMR, : 1.68 (s, 3 H,
MeC(4)); 2.20 (s, 3 H, MeC(5)); 4.45 (s, 2 H, CH2). 13C NMR,
: 5.4 (MeC(4)); 15.0 (MeC(5)); 74.0 (CH2), 111.7 (C(4)); 186.6
(C(5)); 203.3 (C(3)). Found (%): C, 64.08; H, 7.12. C6H8O2.
Calculated (%): C, 64.27; H, 7.19.
Scheme 7
ꢀChloroacetophenone (5b). Anhydrous GaCl3 (290 mg,
1.64 mmol) was added to a stirred solution of diazoacetoꢀ
phenone 1b (200 mg, 1.37 mmol) in CH2Cl2 (3 mL). The reacꢀ
tion mixture was vigorously stirred at 20 C for 5 min and acidiꢀ
fied with 10% HCl to pH 1—2. The product was extracted with
CH2Cl2 (3×10 mL). The combined organic extracts were dried
with anhydrous MgSO4 and concentrated in vacuo. The yield of
ꢀchloroacetophenone was 192 mg (91%), colorless crystals,
m.p. 55—57 C. The 1H and 13C NMR spectra of compound 5b
agree with the literature data.9
Reactions of diazo ketones 1a and 1b with methyl acrylate in
the presence of GaCl3 (general procedure). Anhydrous GaCl3
(0.2 or 1 mmol, see Table 1) was added in one portion under
argon to a stirred solution of diazo ketone 1a or 1b (1 mmol) and
methyl acrylate (3 mmol) in dry CH2Cl2 (3 mL). The mixture
was stirred at 20 C for 15 min and acidified with 10% HCl to
pH 1—2. Organic materials were extracted with CH2Cl2 (3×10 mL).
The combined organic extracts were dried with anhydrous
MgSO4 and concentrated in vacuo. The residue was separated by
column chromatography on SiO2 with benzene—AcOEt (10 : 1)
as an eluent. For the yields of the compounds obtained, see
Table 1.
Methyl 2ꢀacetylcyclopropanecarboxylate (9a) was obtained
from diazoacetone 1a (85 mg, 1 mmol) and methyl acrylate
(255 mg, 3 mmol) in the presence of GaCl3 (34 mg, 0.2 mmol).
Yield 68 mg (48%), a ~3.5 : 1 mixture of Eꢀ and Zꢀisomers (isoꢀ
lated by column chromatography). With an increased amount of
GaCl3 (175 mg, 1 mmol), the yield of compound 9a was 77 mg
(54%). The 1H and 13C NMR spectra of this product agree with
the literature data.12,13
Experimental
1
H and 13C NMR spectra were recorded on a Bruker AMXꢀ400
spectrometer (400.1 and 100.6 MHz, respectively) in CDCl3
containing 0.05% Me4Si as an internal standard. The signals
were assigned, and the ratio of isomeric reaction products was
determined, using homoꢀ and heteronuclear 1D and 2D correꢀ
lation experiments (DEPT, COSY, NOESY, HSQC, and HMBC).
Highꢀresolution mass spectra (ESIꢀHRMS) were recorded on
a micrOTOF instrument. Thinꢀlayer chromatography was carried
out on Silufol plates (Merck). For column chromatography,
Merck 60 silica gel (0.040—0.063 mm) was used. Anhydrous
GaCl3 was purchased from Aldrich and always handled under
dry argon. Reagentꢀgrade solvents (>99.5% purity) were used
without further purification. Dichloromethane was dried with
granulated KOH and distilled over P2O5 under dry argon.
Reactions of diazo ketones 1a,b with EtAlCl2. A 1 M soluꢀ
tion of EtAlCl2 (1.2 mL, 1.2 mmol) in hexane was added to
a stirred solution of diazo ketone 1a or 1b (1 mmol) in CH2Cl2
(2.5 mL). The resulting mixture was vigorously stirred at 20 C
for 1 min. Then MeOH or CD3OD (1 mL) was added. The
Methyl 2ꢀbenzoylcyclopropanecarboxylate (9b) was obtained
from diazoacetophenone 1b (145 mg, 1 mmol) and methyl acrylate
(255 mg, 3 mmol) in the presence of GaCl3 (34 mg, 0.2 mmol).
Separation by column chromatography gave isomers Eꢀ9b
(53 mg, 26%) and Zꢀ9b (21 mg, 10%) and small fractions conꢀ

408
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 2, February, 2014
Novikov et al.
taining compound 10 (~3%) and a ~4 : 1 mixture of minor cycloꢀ
propanes Eꢀ and Zꢀ11 (~5 or 10%; 1H NMR data) (see Table 1).
With an increased amount of GaCl3 (175 mg, 1 mmol), the
yields of Eꢀ9b and Zꢀ9b were 82 (40%) and 31 mg (15%), respecꢀ
tively. The 1H and 13C NMR spectra of cyclopropanes Eꢀ9b and
Zꢀ9b agree with the literature data.14 The procedure for isolation
of cyclopropanes Eꢀ and Zꢀ11 is described below, followed by
their characteristics.
4 H, oꢀHPh). 13C NMR, : 12.6 (C(3)); 22.8 (C(1)); 26.5 (C(2));
66.4 (OCH2); 127.9, 128.5, 128.7, and 129.0 (oꢀCHPh and
mꢀCHPh); 133.3 and 133.9 (2 pꢀCHPh); 134.2 and 136.7
(2 ipsoꢀCPh); 169.7 (COO); 192.1 and 194.8 (2 CO). C19H16O4.
Calculated: [M + Na], 331.0941. Found: m/z 331.0937.
This work was financially supported by the Division of
Chemistry and Materials Sciences of the Russian Academy
of Sciences (Basic Research Program "Theoretical and
Experimental Study of the Nature of Chemical Bonding
and the Mechanisms of Essential Chemical Reactions and
Processes) and the Council on Grants at the President of
the Russian Federation (State Support Program for Leadꢀ
ing Scientific Schools of the Russian Federation, Grant
NShꢀ604.2012.3).
Methyl 3ꢀbenzoylꢀ1ꢀ(2ꢀoxoꢀ2ꢀphenylethyl)ꢀ4,5ꢀdihydroꢀ1Hꢀ
pyrazoleꢀ5ꢀcarboxylate (10). Colorless oil, ~90% purity. 1H NMR,
: 3.47 (dd, 1 H, Ha(4), 2J = 17.5 Hz, 3J = 10.6 Hz); 3.66 (dd, 1 H,
Hb(4), 2J = 17.5 Hz, 3J = 13.4 Hz); 3.78 (s, 3 H, OMe); 4.75 (dd,
3
3
1 H, H(5), J = 13.4 Hz, J = 10.6 Hz); 5.01 and 5.22 (both d,
2
1 H each, CH2, J = 18.1 Hz); 7.35—7.65 (m, 6 H, mꢀHPh and
pꢀHPh); 7.96 and 8.07 (both m, 4 H, oꢀHPh).
Reaction of diazoacetophenone with methyl acrylate in the
presence of GaCl3 and water. A. Anhydrous GaCl3 (125 mg,
0.7 mmol) was added in one portion to a solution of diazoacetoꢀ
phenone (103 mg, 0.7 mmol), methyl acrylate (180 mg, 2.1 mmol),
and water (26 mg, 1.4 mmol) in CH2Cl2 (3 mL). The reaction
mixture was stirred at ~20 C for 15 min and worked up accordꢀ
ing to the general procedure. Separation by column chromatoꢀ
graphy on SiO2 with benzene—AcOEt (10 : 1) as an eluent afꢀ
forded compounds Eꢀ9b (26 mg, 18%), Eꢀ11 (45 mg, 42%), Zꢀ9b
(10 mg, 7%), and Zꢀ11 (11 mg, 10%) as colorless oils and a small
fraction containing compound 12 (<5% yield).
References
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B. A similar reaction of compound 1b (208 mg, 1.4 mmol)
with methyl acrylate (40 mg, 0.48 mmol) in the presence of
water (18 mg, 1 mmol) and GaCl3 (86 mg, 0.48 mmol) gave
2ꢀoxoꢀ2ꢀphenylethyl acrylate (12) (42 mg, 46%) as a colorless oil
and cyclopropanes Eꢀ and Zꢀ9b and Eꢀ and Zꢀ11 in a total yield
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1
eluent. The H and 13C NMR spectra of compounds 9b and 12
agree with the literature data.14,15
2ꢀOxoꢀ2ꢀphenylethyl Eꢀ2ꢀbenzoylcyclopropanecarboxylate
(Eꢀ11). 1H NMR, : 1.70 (ddd, 1 H, Ha(3), 2J = 3.7 Hz, 3J = 8.5 Hz,
2
3
3J = 5.7 Hz); 1.74 (ddd, 1 H, Hb(3), J = 3.7 Hz, J = 8.5 Hz,
3
3
3J = 6.0 Hz); 2.55 (ddd, 1 H, H(1), J = 8.5 Hz, J = 5.7 Hz,
3
3
3J = 3.7 Hz); 3.31 (ddd, 1 H, H(2), J = 8.5 Hz, J = 6.0 Hz,
3J = 3.7 Hz); 5.36 and 5.41 (both d, 1 H each, OCH2, 2J = 16.3 Hz);
7.44—7.65 (m, 6 H, mꢀHPh and pꢀHPh); 7.92 and 8.07 (both m,
4 H, oꢀHPh). 13C NMR, : 17.9 (C(3)); 24.5 (C(1)); 26.6 (C(2));
66.5 (OCH2); 127.9, 128.6, 128.8, and 129.1 (oꢀCHPh
and mꢀCHPh); 133.5 and 134.1 (2 pꢀCHPh); 134.4 and 137.2
(2 ipsoꢀCPh); 171.9 (COO); 192.0 and 197.0 (2 CO). C19H16O4.
Calculated: [M + Na], 331.0941. Found: m/z 331.0939.
12. T. Saegusa, K. Yonezawa, I. Murase, T. Konoike, S. Tomita,
Y. Ito, J. Org. Chem., 1973, 38, 2319.
13. D. Romo, J. L. Romine, W. Midura, A. I. Meyers, Tetraꢀ
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15. P. M. Joensuu, H. W. Lam, Org. Lett., 2005, 7, 4225.
2ꢀOxoꢀ2ꢀphenylethyl Zꢀ2ꢀbenzoylcyclopropanecarboxylate
(Zꢀ11). 1H NMR, : 1.48 (ddd, 1 H, Ha(3), 2J = 4.8 Hz, 3J = 8.6 Hz,
2
3
3J = 8.5 Hz); 2.01 (ddd, 1 H, Hb(3), J = 4.8 Hz, J = 7.1 Hz,
3
3
3J = 6.7 Hz); 2.51 (ddd, 1 H, H(1), J = 8.7 Hz, J = 8.5 Hz,
3
3
3J = 6.7 Hz); 2.89 (ddd, 1 H, H(2), J = 8.7 Hz, J = 8.6 Hz,
3J = 7.1 Hz); 5.18 and 5.28 (both d, 1 H each, OCH2, 2J = 16.4 Hz);
7.36—7.60 (m, 6 H, mꢀHPh and pꢀHPh); 7.83 and 8.04 (both m,
Received December 4, 2013