Synthesis of 3- and 5-alkyl-6-alkyl(aryl)tetrahydropyran-2,4-diones by the condensation of β-oxo acid esters with aldehydes and ketones

Article abstract of DOI:10.1023/A:1011913328785

A method is proposed for obtaining 3- and 5-alkyl-6-alkyl(aryl)tetrahydropyran-2,4-diones based on the condensation of the dianion of alkyl(dialkyl)acetoacetic ester with aldehydes and ketones.

Full text of DOI:10.1023/A:1011913328785

Chemistry of Heterocyclic Compounds, Vol. 37, No. 6, 2001
SYNTHESIS OF 3- AND 5-ALKYL-
6-ALKYL(ARYL)TETRAHYDROPYRAN-
2,4-DIONES BY THE CONDENSATION
OF -OXO ACID ESTERS WITH
β
ALDEHYDES AND KETONES
I. P. Lokot', F. S. Pashkovskii, and F. A. Lakhvich
A method is proposed for obtaining 3- and 5-alkyl-6-alkyl(aryl)tetrahydropyran-2,4-diones based on the
condensation of the dianion of alkyl(dialkyl)acetoacetic ester with aldehydes and ketones.
Keywords: dihydro-2-pyrones, carbonyl compounds, tetrahydropyrandiones, condensation,
lactonization.
Natural and synthetic alkyl(aryl)tetrahydropyran-2,4-diones attract attention because of their diverse
biological properties [1,2]. A large number of approaches has been developed for the preparation of
6-alkyl(aryl)pyran-2,4-diones, but only individual publications have been devoted to the synthesis of 3,6- and
5,6-substituted derivatives [3,4].
As in the case of other cyclic -dicarbonyl compounds the introduction of an alkyl substituent by
β
alkylating the anion of tetrahydropyran-2,4-dione is ineffective since O-alkylation predominates [5-9]. We have
therefore investigated the possibility of introducing an alkyl substituent at the stage of forming the acyclic
precursor to lead to the desired 3(5)-alkyltetrahydropyran-2,4-dione. As shown by retrosynthetic analysis of
compounds 1 (see Scheme 1) the precursors are substituted esters of the 5-hydroxy-3-oxo acids 2, the products of
aldol condensation of the readily available esters of the 3-oxo acids 3 [10-14] with carbonyl compounds 4 [13,15-19].
Scheme 1
O
R2
R3
R1
O
OH
R4
O
O
O
R3
OH
R2
R1
O
R4
1
O
OH
O
O
O
R3
R4
R3
OEt (Me)
+
OEt (Me)
R4
R2
R1
R2
R1
4
3
2
__________________________________________________________________________________________
Institute of Bioorganic Chemistry, Academy of Sciences of Belarus, Minsk 220141; e-mail:
lokot@yahoo.com. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 768-775, June 2001.
Original article submitted July 13, 1999; revision submitted June 29, 2000.
0009-3122/01/3706-0707$25.00©2001 Plenum Publishing Corporation
707

Results are given in the present work on the development of a general procedure for condensing
substituted compounds 3 and 4. In the first step of the reaction the appropriate dianion is obtained by treating
ester 3 with 2.5 equivalents of lithium diisopropylamide. The dianion is then treated with aldehyde or ketone.
Analysis of the reaction mixtures by TLC showed the presence of the desired tetrahydropyrandione 1 and its
precursor, the ester of 5-hydroxy-3-oxo acid 2. For complete conversion of the latter into product 1 the
unseparated mixture was in each case saponified with aqueous KOH solution. Dione 1 forms a salt under the
action of KOH, which is relatively inert to alkali, but ester 2 is converted into a salt of the 5-hydroxy-3-oxo
carboxylic acid, which on acidification is spontaneously lactonized into the desired product 1 (see Scheme 2).
Scheme 2
1. 2.5 eq. LDA
HMPA, -78°C,
argon, THF
O
R2
R3
R1
O
O
O
OH
R4
O
O
2. R3C(O)R4 4a-g
+
R3
OEt (Me)
1. KOH
OEt(Me)
+
3. H3O
R2
R1
3a–c
O
1a–j
R2
2a–j
R1
R4
+
2. H3O
1a-c, 3a, 4a-c R1 = CH2CH=CH2, R2 = R3 = H, a R4 = CH3, b R4 = C4H9,
c R4 = C6H4OCH3-4;1d, 3b R1 = R3 = H, R2 = C6H13, R4 = C6H4OCH3-4;
1e-j, 3c, 4d-g R1 = R2 = R3 = H, 1e R4 = C4H9, 1f R4 = C6H4OCH3-4,
1g, 4d R4 = C6H5, 1h, 4e R4 = C6H4(OCH3)2-4, 1i, 4f R3 = R4 = CH3,
1j, 4g R3+R4 = (CH2)8
The synthesis of 3-alkyl derivatives of tetrahydropyrandione was effected using as an example
-allylacetoacetic ester 3a, which was readily obtained from allyl bromide and acetoacetic ester 3c in the
α
presence of sodium methylate [20]. By condensing ester 3a with acetaldehyde 4a, butyraldehyde 4b, and
4-methoxybenzaldehyde 4c, the corresponding 3,6-disubstituted tetrahydropyrandiones 1a-c were synthesized.
The 5-alkyl derivative of tetrahydropyrandione 1d was synthesized from aldehyde 4c and octanoylacetic acid
ester 3b, the product of methanolysis of the octanoyl derivative of Meldrum's acid [14,21]. This is formed in
quantitative yield under mild conditions from the readily available Meldrum's acid and octanoyl chloride. In
addition, by the interaction of acetoacetic ester 3c with aldehydes 4b,c, benzaldehyde 4d,
3,4-dimethoxybenzaldehyde 4e, and acetone 4f, the products 1e-j respectively were obtained containing no
substituent in positions 3 and 5. The use of cyclononanone 4g in this reaction leads to the spiro compound 1j.
The yields of products 1 and their physicochemical properties are given in Table 1.
As might have been expected, the steric obstacles caused by the alkyl substituent in ester 3d introduced
a certain contribution to the fall in yield of the 5-hexyl derivative 1d, which was isolated only as the trans
isomer. The presence of an allyl substituent in ester 3a and the structure of carbonyl compounds 4a-c did not
significantly influence the yield of the desired products.
1
The tetrahydropyrandiones 1, according to data of H NMR spectra, are predominantly in the dioxo
form, though exchange of protons in position 3 by deuterium occurs in CD3OD solution due to enolization. For
a more precise assignment of the proton signals of the two tautomers of compound 1 we obtained derivatives of
the enol form, certain of them being the substituted dihydropyrones 5 and 6 (see Scheme 3). The
physicochemical properties of products 5 and 6 are given in Table 2.
708

TABLE 1. Characteristics of Alkyl(aryl)pyrane-2,4-diones
Found, %
——————
Com-
Empirical
formula
mp. oC
(ether)
Yield,
%
IR spectrum*, ν, cm-1
1H NMR spectrum, δ, ppm, CC (J), Hz
Name
2
Solvent
Calculated, %
pound
С
Н
1
3
4
5
6
7
8
9
10
77
1.45 (3Н, d, 3J = 6.5, СН3); 2.35-2.77 (4H, m,
СН2СН= and СНСН2СО); 3.54 (1H, t, 2J = 6.0,
СНСН2С=); 4.52 (1H, m, СНСН3);
3-Allyl-6-methyltetrahydro- C9H12O3
pyrane-2,4-dione
64.08
64.27
7.09
7.19
96-97
CDCl3
1a
5.10 (2H, m, =СН2); 5.90 (1H, m, =СН)
3-Allyl-6-butyltetrahydro-
pyrane-2,4-dione
C12H18O3 68.68
68.55
8.65
8.63
126-128 755, 800,875, 915, 930,
1000, 1135, 1165, 1220,
1270, 1320, 1360, 1380,
1595, 2640, 2960
CDCl3
0.94 (3Н, t, 3J = 7.0, СН3); 1.20-1.50 (4H, m,
СН3(СН2)2); 1.60-1.75 (2H, m, ОСНСН2СН2);
2.32-2.83 (4H, m, =СНСН2 and ОСНСН2);
3.55 (1Н, t, 3J = 6.0, СHСН2);
71
82
1b
1c
4.70 (1H, m, СНО); 5.03-5.22 (2H, m, =СН2);
5.92 (1H, m, =СН)
3-Allyl-6-(4-methoxy-
phenyl)tetrahydropyrane-
2,4-dione
C15H16O4 69.08
69.22
6.12
6.20
156-158 735, 920, 1010, 1040,
1080, 1130, 1180, 1255,
CDCl3 + 2.63 (1Н, dd, 3J = 12.5, 2J = 17.0,
CD3OD
CHCHAHBCO); 2.92 (1Н, dd, 3J = 12.5,
1305, 1390, 1525, 1615 br.
2J = 17.0, CHCHAHB); 3.09 (2Н, dd, 3J = 6.0,
1.0, =СНСН2); 3.34 (1H, t, 3J = 1.0,
СНСН2СН=); 3.82 (3H, s, ОСН3); 5.00 (2H, m,
=СН2); 5.38 (1Н, dd, 3J = 4.0, 12.0, ArCH);
5.90 (1H, m, =СН); 6.93 and 7.37 (2Н and 2Н,
two d, 3J = 8.9, o- and m-HAr
)
1d
1e
trans
-5-Hexyl-6-(4-
methoxyphenyl)-
tetrahydropyrane-2,4-dione
C18H24O4 70.92
71.03
7.96
7.95
86-87
Oil
840, 900, 1040, 1190,
1220, 1265, 1525, 1595,
1665, 2865, 2935
CDCl3
CDCl3
0.86 (3Н, t, 3J = 6.0, СН3СН2); 1.20 (10H, m,
СН3(СН2)5); 2.73 (1H, m, СНСН2); 3.40 (1Н, d,
2J = 19, СНAНBСО2); 3.58 (1Н, d, 2J = 19.0,
СНAНBСО2); 3.84 (3H, s, ОСН3); 5.37 (1Н, d,
3J = 7.8, АrCH); 6.93 and 7.15 (2Н and 2Н,
38
76
two d, 3J = 8.5, o- and m-HAr
)
6-Butyltetrahydropyrane-
2,4-dione
C9H14O3
63.60
63.51
8.31
8.29
1230, 1405, 1455, 1640,
2890, 2960
0.95 (3H, t, 3J = 7.0, СН3); 1.20-1.90 (6H,
m, 6-(СН2)3); 2.30 (1Н, dd, 3J = 4.0, 2J = 17.0,
5-HA); 2.46 (1Н, dd, 3J = 12.0, 2J = 17.0, 5-НB);
3.75 (2H, s, 3-Н2); 4.30 (1H, m, 6-H)

TABLE 1 (continued)
1
2
3
4
5
6
7
8
9
10
82
6-(4-Methoxyphenyl)-
C12H12O4 65.65
65.45
5.52 131-132 830, 920, 955, 1010, 1040, CDCl3
2.92 (2Н, d, 3J = 8.5, СНСН2); 3.50 (1Н, d,
2J = 20.0, СНAНBСО2); 3.70 (1Н, d, 2J = 20.0,
СHAНBСО2); 3.84 (3H, s, СН3); 5.67 (1Н, t,
3J = 7.0, ArCH); 6.95 and 7.17 (2Н and 2Н,
1f
8.29
tetrahydropyrane-2,4-dione
1070, 1180, 1260, 1295,
1350, 1525, 1620, 1720,
1740 br.
two d, 3J = 8.5, o- and m-HAr
)
CDCl3 + 2.57 (1Н, dd, 2J = 17.5, 3J = 4.0, СНСНAНB);
CD3OD
2.84 (1Н, dd, 2J = 17.5, 3J = 12.0, СНСНAНB);
3.37 (less than 2H due to exchange of D, s,
СН2СО2); 3.84 (3H, s, СН3); 5.40 (1Н, dd,
3J = 4.0, 12.0, ArCH); 6.93 and 7.35 (2Н and
2Н, two d, 3J = 8.5, o- and m-HAr
)
6-Phenyltetrahydropyrane-
2,4-dione
C11H10O3 69.62
69.46
5.30
5.30
132-134 1250, 1310, 1345, 1635,
CDCl3 + 2.36 (1Н, dd, 3J = 4.5, 2J = 17.0, СНСНAНB);
CD3OD 2.59 (1Н, dd, 3J = 12.0, 2J = 17.0, СНСНAНB);
3.09 (2H, s, СН2СО2); 5.20 (1Н, dd, 3J = 4.5,
2J = 12.0, PhCH); 7.14 (5H, m)
87
77
1g
1h
1715, 1735
[15]
6-(2,4-Dimethoxyphenyl)-
tetrahydropyrane-2,4-dione
C13H14O5 62.45
62.39
5.65
5.64
Oil
660, 675, 740, 775, 820,
860, 1030, 1140, 1270,
1470, 1525, 1595, 1710,
1740
CDCl3
2.76 (1Н, dd, 2J = 17.0, 3J = 4.5, СНСНAНB);
2.91 (1Н, dd, 2J = 17.0, 3J = 12.0, СНСНAНB);
3.40 (2Н, s, СН2СО2); 3.84 and 3.80 (6H,
two s, two СН3); 5.00 (1Н, dd, 3J = 4.0, 8.5,
ArCH); 5.84 (1Н, s, 2'-H);
6.75 (2Н, two s, 5'- and 6'-H)
6,6-Dimethyltetrahydro-
pyrane-2,4-dione
C7H10O3
59.10
59.14
7.06
7.09
127-128 1020, 1115, 1190, 1210,
1245, 1290, 1330, 1355,
1580, 1660
120-122 860, 1000, 1030, 1220,
1265, 1320, 1480, 1610,
1675, 2930
CD3OD 1.53 and 1.48 (6Н, two s, two СН3);
2.47 (1H, s, (СН3)2ССНAНB); 2.72 (1H, s,
(СН3)2ССНAНB)*2
84
75
1i
1j
1-Oxaspiro[5,8]tetradecane- C13H20O3 69.50
2,4-dione
9.00
8.99
CDCl3
1.35-1.85 (14H, m, 7 CH2); 2.13 (2H, m,
CCH2CH2); 2,70 (2H, s, ССН2СО);
3.43 (2H, s, СН2СО2)
69.61
_______
* The spectra of compounds 1e and 1h were taken with a film of substance, the remainder in KBr disks.
*2 The signal of the protons of the CH2CO2 grouping is not observed due to exchange of these protons with deuterium.

TABLE 2. Characteristics of Derivatives of the Enol Forms of Alkyl(aryl)pyrane-2,4-diones*
Found, %
——————
Com-
Empirical
formula
Yield,
%
IR spectrum, ν, cm-1
1H NMR spectrum, δ, ppm, CC (J), Hz*2
Name
Calculated, %
pound
С
Н
4-Acetoxy-3-allyl-6-
methyl-5,6-dihydro-
2-pyrone
C11H14O4
C17H18O5
C14H14O5
62.97 6.72
62.85 6.71
1.42 (3Н, d, 3J = 7.0, 6-CH3); 2.20 (3H, s, С(О)СН3);
2.46 (1Н, dd, 2J = 11.5; 3J = 4.0, СНСНAНB);
2.66 (1Н, dd, 2J = 11.5, 3J = 17.0, СНСНAНB);
3.00 (2H, m, СН2СН=); 4.58 (1H, m, СН3СН);
5.00 (2H, m, =СН2); 5.70 (1H, m, =СН)
94
93
95
5a
5b
5c
6a
4-Acetoxy-3-allyl-6-
(4-methoxyphenyl)-
5,6-dihydro-2-pyrone
67.44 5.99
67.54 6.00
750, 825, 910, 930, 1015, 1040, 2.21 (3H, s, С(О)СН3); 2.62 (1Н, dd, 3J = 4.0, 2J = 18.0, СНAНB);
1075, 1130, 1205, 1255, 1290,
1315, 1330, 1380, 1430, 1470,
1525, 1600, 1625, 1650, 1690,
1730, 1765, 2820, 2870
3.03 (3Н, m, СНAНB and =СНСН2); 3.78 (3H, s, ОСН3);
5.02 (2Н, m, =СН2); 5.36 (1Н, dd, 3J = 4.0, 13.0, ArCH);
5.76 (1Н, m, =СН); 6.83 and 7.28 (2Н and 2Н, two d,
3J = 8.5, o- and m-HAr
)
4-Acetoxy-6-
64.18 5.39
64.12 5.38
915, 935, 970, 1160, 1185,
1205, 1260, 1290, 1310, 1385,
1435, 1470, 1525, 1625, 1670,
1720, 1775
2.26 (3H, s, С(О)СН3); 2.64 (1Н, dd, 3J = 3.5, 2J = 18.0, СНAНB);
3.00 (1Н, ddd, 3J = 12.0, 2J = 18.0, 4J = 1.5, СНAНB);
(4-methoxyphenyl)-
5,6-dihydro-2-pyrone
3.83 (3H, s, ОСН3); 5.45 (1Н, dd, 3J = 3.5, 12.0, ArCH);
6.00 (1Н, d, 4J = 1.5, =СНСО); 6.90 and 7.33 (2Н and 2Н, two d,
3J = 8.5, o- and m-HAr
)
6-Butyl-4-methoxy-
5,6-dihydro-2-pyrone
C10H16O3
C12H12O3
65.04 8.74
65.19 8.75
745, 830, 880, 970, 1010, 1050, 0.95 (3Н, t, 3J = 7.0, СН3СН2); 1.20-1.95 (6H, m, СН3(СН2)3);
94
89
1135, 1180, 1230, 1290, 1400,
1460 br., 1630, 1720, 2885,
2965
2.27 (1Н, dd, 2J = 17.0, 3J = 4.0, СНAНB); 2.46 (1Н, ddd,
2J = 17.0, 3J = 12.0, 4J = 1.5, СНAНB); 3.75 (3H, s, ОСН3);
4.32 (1H, m, СН2СН); 5.07 (1H, d, 4J = 1.5, =СН)
4-Methoxy-6-phenyl-
5,6-dihydro-2-pyrone
70.47 5.91
70.58 5.92
2.67 (1Н, dd, 2J = 18.0, 3J = 4.0, СНAНB); 3.00 (1Н, ddd, 2J = 18.0,
6b
3J = 12.0, 4J = 1.5, СНAНB); 3.83 (3H, s, ОСН3);
6.03 (1Н, d, 4J = 1.5, ОС=СН); 7.15 (5H, m, НPh
)
_______
* Compounds 5a-c, 6a were oils, compound 6b had mp 101-102°C (ether).
*2 The spectrum of compound 5c was taken in a CDCl3–CCl4 mixture, the remainder in CDCl3.

Scheme 3
O
OMe
O
O
R1
–
+
1. Et3N
2. AcCl R3
1. Bu4N OH
2. Me2SO4
1a,b,f
1e,g
R3
O
O
O
5a–d
6a,b
5a R1 = CH2CH=CH2, R3 = CH3; b R1 = CH2CH=CH2, R3 = C6H4OCH3-4;
c R1 = H, R3 = C6H4OCH3-4; 6a R3 = C4H9; b R3 = C6H5
The shape of the signals of the protons in positions 3 and 5 of compound 1 depends on the substituents
in the ring and on the solvent (see Tables 1 and 3). The latter is probably explained by the change in dynamics
of the conformational transitions on forming methanolic solvates.
a
H
O
c
b
H
H
Ar
H
d
H
O
O
1f
Two racemic pairs of -hydroxy- -oxo esters 2a-c must formally be formed from the aldol condensation
γ
β
leading to the corresponding racemic pairs of tetrahydropyrandiones 1a-c with two chiral atoms at C(3) and C(6).
As a result of keto-enol tautomerism observed in the -dicarbonyl fragment of diones 1 there is possibly a
β
spontaneous change in configuration at atom C(3). The equilibrium of this reaction is displaced towards the
thermodynamically most stable racemic pair (starting from general considerations the most preferred seem to be
the isomers in which the alkyl substituents occupy equatorial positions).
H
3
O
5
4
R
6
O
Allyl
2
1
H
O
TABLE 3. Effect of Exchanging the Solvent on the Coupling Constants of
the Protons at C(3) and C(5) in 6-(4-Methoxy)tetrahydropyran-2,4-dione 1f
CDCl3
CDCl3 + CD3OD
H
shape of
shape of
δ, ppm
J
ab or Jcd
δ, ppm.
J
ab or Jcd
signal
signal
2.92
2.92
3.50
3.70
d
d
d
d
~0
~0
19
19
2.57
2.84
3.37
3.37
dd
dd
s
17.5
17.5
~0
a
b
c
s
~0
d
712

In order to obtain 5-alkyl derivatives of tetrahydropyran-2,4-dione of the type of 1d in good yield it was
logical to apply an alternative method, viz. the alkylation of tetrahydropyran-2,4-dione 1g dianion or the anion
of its 4-methoxy derivative 6b. However this reaction proceeded to benzylideneacetone in 80% yield (see
Scheme 4). Probably destruction of the dianion leads to the formation of the unstable acid 8 clearly shown by
TLC (like the hydroxy ester 2, 3-oxoacid 8 was colored brown by the action of alcoholic FeCl3 solution).
Scheme 4
_
_
O
O
O
O
_
2 eq. LDA
1g or 6b
_
Ph
Ph
O
O
H3O+
O
O
O
– CO2
Ph
Ph
OH
7
8
EXPERIMENTAL
1
The H NMR spectra were recorded on a Bruker AC spectrometer (operating frequency 200 MHz) in
CDCl3 and CD3OD solution, internal standard was TMS. The IR spectra were recorded on a UR 20 spectrometer
in KBr disks or as a film of compound. Melting points were determined on a Kofler block. Silufol UV 254
plates were used for TLC eluting with the following mixtures: chloroform–methanol [for pyrandiones 1 and
3,5-dioxo esters 2; Rf (1)/Rf(2) approx. 4], ether–hexane (for enol acetates 5 and enol esters 6). Column
chromatography was carried out on silica gel 60 (70-230 ), eluent was chloroform. The derivatives of
µ
acetoacetic ester 3 and carbonyl compounds 4 were redistilled before reaction. The spectral characteristics of
benzylidenacetone 7 were identical to the literature data of [22].
Condensation of Esters of -Oxo Carboxylic Acids 3 with Aldehydes and Ketones 4 (General
β
Procedure). Ester 3 (0.01 mol) was added with stirring in an atmosphere of argon to a solution of lithium
diisopropylamide (0.025 mol), obtained from butyllithium (0.025 mol), diisopropylamine (2.53 g, 0.025 mol),
and hexamethylphosphoramide (1.63 g, 0.01 mol), in absolute tetrahydrofuran (50 ml) at -78°C. After 20 min
the aldehyde or ketone 4 (0.012 mol) was added, the mixture stirred for 30 min, and treated with 2 N HCl
(60 ml). The organic layer was separated, combined with ether extracts (2 × 100 ml) of the aqueous layer, and
evaporated. The residue was dissolved in 1 N KOH (100 ml), the solution stirred for 5 h, cooled to 0°C, and
cold aqueous 6 N HCl solution added to pH 0. Product 1 precipitated as a solid, was filtered off, and washed
with cold water. An additional quantity of product 1 was obtained by extraction of the aqueous layer after
separating product 1 with ether (2 × 100 ml), drying the extract with sodium sulfate, and evaporating the
solvent. Column chromatography on silica gel (eluent chloroform) was used to isolate the 5-hexyl derivative 1d.
Analytical samples were obtained by recrystallization of the products from ether.
Acetylation of the Alkyl Derivatives of Tetrahydropyran-2,4-dione 1 (General Procedure).
Triethylamine (1.4 ml, 0.01 mol) was added with stirring to tetrahydropyran-2,4-dione 1 (0.01 mol) in absolute
dichloromethane (50 ml). After complete solution of dione 1, acetyl chloride (0.78 ml, 0.01 mol) in
dichloromethane (15 ml) was added dropwise. After 1 h the mixture was acidified with 0.2 N HCl (15 ml). The
713

organic layer was separated, washed with saturated NaCl solution (2 × 50 ml), dried with sodium sulfate, and
evaporated. To remove contaminating starting materials the solid was applied to a small layer of Al2O3 and
eluted with chloroform.
Synthesis of 4-Methoxy-5,6-dihydro-2-pyrones 6 (General Procedure). Calcined finely ground
potassium carbonate (2.76 g, 0.02 mol) and dimethyl sulfate (1.39 g, 0.011 mol) were added to a solution of the
appropriate tetrahydropyran-2,4-dione 1 (0.01 mol) in acetone. The mixture was boiled for about 4 h, after
which the solid inorganic salt was filtered off, and washed thoroughly with acetone. The washings were
combined with the filtrate. After evaporating the acetone the residue was recrystallized from ether.
REFERENCES
1.
2.
E. F. Steinmetz, Piper methysticum (Kava), Famous Drug Plant of the South Sea Islands, Elsevier,
Amsterdam (1960).
W. B. Morc, M. T. Magalhaes, and O. R. Gottlieb in L. Zechmeister (editor), Progress in the Chemistry
of Organic Natural Products, Vol. 20, Springer-Verlag, Berlin (1962).
B. Eistert and G. Heck, Justus Liebigs Ann. Chem., 681, 123 (1965).
R. M. Carlson, A. R. Oyler, and J. R. Peterson, J. Org. Chem., 40, 1610 (1975).
A. A. Akhrem, F. A. Lakhvich, L. G. Lis, V. A. Khripach, N. A. Fil'genkov, V. A. Kozinets, and
F. S. Pashkovskii, Dokl. Akad. Nauk SSSR, 311, 1381 (1990).
3.
4.
5.
6.
7.
8.
9.
J. M. McIntosh and P. M. Beaumier, Can. J. Chem., 51, 843 (1979).
H. Stetter and W. Dierichs, Chem. Ber., 85, 1061 (1952).
H. O. House, Modern Synthetic Reactions, Benjamin, New York (1972). p. 511.
D. N. Kursanov, Z. N. Parnes, M. I. Kalinkin, and N. M. Loim, Ionic Hydrogenation [in Russian],
Khimiya, Moscow (1979), p. 192.
10.
11.
12.
13.
14.
M. W. Rathke and J. Deitch, Tetrahedron Lett., 2953 (1971).
I. Shahak and Y. Sasson, Tetrahedron Lett., 4207 (1973).
R. M. Carlson and J. L. Isidor, Tetrahedron Lett., 4819 (1973).
S. N. Huckin and L. Weiler, Tetrahedron Lett., 1082 (1974).
M. Sato, J. Sakaki, K. Takayama, S. Kobayashi, M. Suzuki, and C. Kaneko, Chem. Pharm. Bull., 38, 94
(1990).
15.
16.
17.
18.
19.
20.
21.
22.
J. R. Petersen, T. J. Winter, and C. P. Miller, Synth. Commun., 18, 949 (1988).
I. Paterson, D. J. Wallace, and C. J. Cowden, Synthesis, 639 (1998).
D. Seebach and K. Meyer, Angew. Chem., 86, 40 (1974).
T. Reffstrup and P. M. Boll, Acta Chem. Scand., B30, 613 (1976).
J. F. Wolfe, T. M. Harris, and C. R. Hauser, J. Org. Chem., 29, 3249 (1964).
Organicum [Russian translation], Vol. 2, Mir, Moscow (1979), p. 176.
M. Sato, H. Ogasawara, K. Oi, and T. Kato, Chem. Pharm. Bull., 31, 1896 (1983).
C. Pouchert, Alrich Library of NMR Spectra, Ed. 2, Vol. 2, Aldrich Chem. Co. Inc. (1983), p. 53D;
Aldrich Library of IR Spectra, Ed. 3, Aldrich Chem. Co. Inc. (1981), p. 852D.
714