Intramolecular hetero-Diels-Alder reactions of functionalized α,β-unsaturated carbonyl compounds: Polycyclic 2H-pyran derivatives

Article abstract of DOI:10.1007/PL00010261

The reaction of benzoylacetonitrile, methyl cyanoacetate, and ethyl benzoylacetate with 2-allyloxy-and 2-(3-methyl-2-butenyloxy)-benzaldehyde as well as 2-(3-methyl-2-butenyloxy)-1-naphthaldehyde afforded the corresponding Knoevenagel condensation products. Some of those underwent spontaneous intramolecular cycloaddilion to give cis-fused 2H-pyran derivatives as major products. One-pot reactions of 1,3-cyclohexanedione and 5,5-dimethyl-1,3-cyclohexancdione with 2-(3-inethyl-2-butenyloxy)-benzaldehyde and 2-(3-methyl-2-butenyloxy)-1-naphthaklehyde resulted in Diels-Alder cycloadducts.

Full text of DOI:10.1007/PL00010261

Monatshefte fuÈr Chemie 130, 795±807 (1999)
Intramolecular Hetero-Diels-Alder Reactions
of Functionalized a,b-Unsaturated Carbonyl
Compounds: Polycyclic 2H-Pyran Derivatives
Ã
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Department of Organic Chemistry, Jagiellonian University, PL-30060 Krakow, Poland
Krystyna Bogdanowicz-Szwed and Aleksandra Paøasz
Summary. The reaction of benzoylacetonitrile, methyl cyanoacetate, and ethyl benzoylacetate with
2-allyloxy- and 2-(3-methyl-2-butenyloxy)-benzaldehyde as well as 2-(3-methyl-2-butenyloxy)-1-
naphthaldehyde afforded the corresponding Knoevenagel condensation products. Some of those
underwent spontaneous intramolecular cycloaddition to give cis-fused 2H-pyran derivatives as major
products. One-pot reactions of 1,3-cyclohexanedione and 5,5-dimethyl-1,3-cyclohexanedione with
2-(3-methyl-2-butenyloxy)-benzaldehyde and 2-(3-methyl-2-butenyloxy)-1-naphthaldehyde resulted
in Diels-Alder cycloadducts.
Keywords. Intramolecular hetero-Diels-Alder reaction; ꢀ,ꢁ-Unsaturated ketones; 2H-Pyrans.
È
Intramolekulare Hetero-Diels-Alder-Reaktionen von funktionalisierten a,b-ungesattigten
Carbonylverbindugen: Polycyclische 2H-Pyranderivate
Zusammenfassung. Reaktion von Benzoylacetonitril, Methylcyanoacetat and Ethylbenzoylacetat
mit 2-Allyloxy- und 2-(3-Methyl-2-butenyloxy)-benzaldehyd sowie mit 2-(3-Methyl-2-butenyloxy)-
1-naphthaldehyd ergab das entsprechende Knoevenagel-Derivat. Einige dieser letzteren Produkte
unterlagen einer spontanen intramolekularen Cycloaddition zu cis-verknuÈpfen 2H-Pyranderivaten als
Hauptprodukt. Eintopfreaktionen von 1,3-Cyclohexandion und 5,5-Dimethyl-1,3-cyclohexandion
mit 2-(3-Methyl-2-butenyloxy)-benzaldehyd und 2-(3-Methyl-2-butenyloxy)-1-naphthaldehyd re-
sultierten in Diels-Alder-Cycloaddukten.
Introduction
The hetero-Diels-Alder reaction of ꢀ,ꢁ-unsaturated carbonyl compounds ± which
can be formally treated as 1-oxa-1,3-butadienes ± with electron-rich dienophiles, e.g.
enol ethers, is an important synthetic method for the construction of 3,4-dihydro-
2H-pyran derivatives which are present in many natural products [1±4]. These
reactions belong to the class of 4ꢂ‡2ꢂ cycloadditions with an inverse electron
demand. Simple 1-oxa-1,3-butadienes show only low reactivity in cycloadditions
with enol ethers. The introduction of the electron-withdrawing groups at positions
Ã
Corresponding author

796
K. Bogdanowicz-Szwed and A. Paøasz
2 or 3 in heterodienes, however, changes their reactivity. This is due to a strong
decrease of the LUMO energy of the diene which then can more easily overlap
with the HOMO of the dienophile. This type of cycloadditions can be performed
via inter- or intramolecular modes. Several examples of intramolecular hetero-
Diels-Alder reactions of 1-oxa-1,3-butadienes possessing alkene substituents have
been reported [5±8], dealing with condensations of cyclic 1,3-dicarbonyl com-
pounds with aldehydes bearing dienophile moieties and affording 2-alkylidene- or
2-arylidene-1,3-dioxo compounds that subsequently underwent 4ꢂ‡2ꢂ cycloaddi-
tion to give cycloadducts. In all reported syntheses, 1,3-dicarbonyl groups were
incorporated in cyclic molecules such as Meldrum's acid [5], N,N-dimethylbarbi-
turic acid [6], pyrazolone, izoxazolone [7], and oxazepandione [8]. These types of
processes belong to the tandem Knoevenagel ± hetero-Diels-Alder reactions and
have been applied for the syntheses of several natural products [4].
Recently, we have reported the ef®cient synthesis of polyfunctionalized 3,4-
dihydro-2H-pyrans via intermolecular hetero-Diels-Alder reactions of cyano
substituted ꢀ,ꢁ-unsaturated ketones with enol ethers [9, 10]. The ef®ciency of
these cycloadditions prompted us to extend these reactions to intramolecular cases.
Results and Discussion
The aim of this work was to investigate intramolecular hetero Diels-Alder reactions
of acyclic o-alkenyloxyarylidene carbonyl compounds containing electron-with-
drawing groups and to compare their reactivity with those of cyclic analogues.
In our investigations, we applied the following active methylene compounds as
substrates: benzoylacetonitrile (1) methyl cyanoacetate (2), ethyl benzoylacetate
(3), benzaldehydes 4a,b, and 1-naphthaldehyde 4c. The aldehydes contained
allyloxy- (4a) and 2-(3-methyl-2-butenyloxy)- (4b,c) groups, in o-position to the
carbonyl function which should act as dienophiles in cycloadditions. Aldehydes
4a±c were condensed with 1, 2, and 3 yielding 2-arylidene derivatives as
intermediates. Their intramolecular hetero-Diels-Alder reaction should give the
desired fused pyrans. We studied these reactions taking into account the character
of the substituents in the diene and in dienophile moieties. All reactions were
carried out in acetonitrile solution in the presence of catalytic amounts of ethylene
diammonium diacetate (EDDA). The progress of the reactions was monitored by
TLC.
The reaction of 1 and 4a, carried out at room temperature, gave rise to the
formation of the Knoevenagel educt 5 in good yield (Scheme 1). The intra-
molecular hetero-Diels-Alder cycloaddition of 5 was accomplished in boiling
xylene and afforded a mixture of the annulated cycloadducts cis-6 and trans-6. The
1
ratio of two diastereoisomers (1.4:1) in the crude product was determined by H
NMR spectroscopy. The con®guration of the cis and trans-annulated compounds
was deduced from chemical shift values and coupling constants of the vicinal
protons attached to C-4a and C-10b. For the cis-adduct, the proton at C-10b
appeared as a doublet at ꢃ ˆ 3.88 ppm with a small coupling constant of 5.4 Hz. For
the trans-diastereoisomer, the signal of the proton at C-10b was a doublet at
ꢃ ˆ 3.73 ppm with a large coupling constant of 11.2 Hz. In the spectra of both

Intramolecular Hetero Diels-Alder Reactions
797
Scheme 1
diastereoisomers, the resonances of the protons at C-4a was observed as a multiplet
in the range of 2.45±2.54 ppm.
The reaction of 1 with aldehydes 4b and 4c, carried out at room temperature,
yielded exclusively the cis-annulated cycloadducts 7 and 8, respectively (Scheme
1). Thus, the condensation-cycloaddition sequence was run as an one-pot reaction.
1
The stereochemistry of the products was con®rmed by their H NMR spectra. For
7, the signal of the proton at C-10b appeared as a doublet at ꢃ ˆ 3.78 ppm with
3J ˆ 5.5 Hz; the signal of proton 12c-H of 8 was a doublet at ꢃ ˆ 4.55 ppm with
3J ˆ 4.1 Hz. It is interesting to note that during the reactions an intensive yellow
colour appeared which faded as the cycloadducts were formed. The condensation
of 2 with aldehyde 4a in acetonitrile in the presence of EDDA furnished the
condensation product 9 that was thermally stable at room temperature (Scheme 2).
Scheme 2

798
K. Bogdanowicz-Szwed and A. Paøasz
Scheme 3
However, heating of 9 in boiling xylene resulted in the formation of lactone 11.
The formation of 11 can be rationalized as depicted in Scheme 2. It consists in a
3,3-sigmatropic shift of the allyl group and formation of the o-phenol derivative 10
which subsequently undergoes ring closure with elimination of methanol to give
11. The structure of 11 was con®rmed by analytical and IR, 1H, 13C NMR, and MS
data.
The reaction of 2 with 4b, performed at room temperature, yielded the
yellowish coloured condensation product 12 exclusively (Scheme 3). Its cyclo-
addition was accomplished in boiling xylene giving the cis-annulated cycloadduct
13 as the sole product. In contrast, the reaction of 2 with 4c occurred at room
temperature, leading directly to the cis-fused compound 14.
In further experiments we studied the reactions of 3 with 4a±c. In these
reactions we expected to observe the in¯uence of the 3-ethoxycarbonyl group in
the 1-oxa-1,3-butadiene intermediates on the intramolecular cycloaddition.
Knoevenagel condensation of 3 with 4a,b, carried out at room temperature, led
to products 15 and 16, respectively (Scheme 4). Prolonged heating of 15 in xylene
did not afford the expected cycloadduct, whereas compound 16 underwent
cycloaddition yielding a mixture of the cis/trans-annulated cycloadducts 17 in a
ratio of 4:1 under these conditions. The reaction of 3 with aldehyde 4c at room
temperature gave rise to the formation of a mixture of the Knoevenagel condensa-
tion product and the Diels-Alder cycloadduct. To complete the cycloaddition, the
reaction mixture was heated in xylene, and the cis cycloadduct 18 was obtained as
the sole product (Scheme 4).
Next we investigated the reactions of cyclic 1,3-dicarbonyl compounds such as
1,3-cyclohexanedione (19) and 5,5-dimethyl-1,3-cyclohexanedione (dimedone 20)
with 4a±c. To our knowledge, the intramolecular cycloaddition of 1,3-cyclo-
hexanedione with (R)-citronellal catalyzed by sodium methoxide leading to the
corresponding trans-cycloadduct has been reported [11].
The reactions of 4a with 19 and 20, carried out at room temperature in
acetonitrile in the presence of EDDA, involved the formation of condensation

Intramolecular Hetero Diels-Alder Reactions
799
Scheme 4
products 21 and 22. Their analytical and spectroscopic data showed that they were
formed by condensation of two molecules of 1,3-dicarbonyl compounds 19 or 20
with one molecule of 4a (Scheme 5). Changing of the reaction condition, e.g. the
sequence of addition of the reagents or lowering of the temperature, did not
in¯uence the course of these reactions. Similar reactions of 20 with aliphatic or
aromatic aldehydes have already been reported [12]. In contrast to 4a, 4b reacted
with 19 and 20 to afford the Diels-Alder cycloaducts 23 and 24 in one-pot
reactions. The 1H NMR analysis of the crude products showed that they consisted
of a mixture of cis/trans-annulated cycloadducts. In both reactions the cis-
cycloadducts were the major products (Table 1). The reaction of 4c with 19 and 20,
carried out at room temperature, led exclusively to formation of cis-fused
cycloadducts 25 and 26, respectively (Scheme 5). The results of the reactions
leading to the cycloadducts obtained are given in Table 1.
In conclusion, we have shown, that the reactions of the activated methylene
compounds with aromatic 2-alkenyloxy aldehydes involved, in the ®rst step,
formation of ꢀ,ꢁ-unsaturated carbonyl compounds that were prone to undergo
intramolecular hetero-Diels-Alder cycloadditions. It is worth to note that all one-
pot reactions occurring at room temperature led to the exclusive formation of cis-
annulated cycloadducts. In contrast, the cycloaddition of isolated Knoevenagel
intermediates required heating and furnished a mixture of cis/trans-cycloadducts
with predominant formation of cis-products. The cyclic 1,3-dicarbonyl compounds
underwent the tandem Knoevenagel-hetero-Diels-Alder reactions easier than the
activated acyclic carbonyl compounds. We did not notice a striking difference

800
K. Bogdanowicz-Szwed and A. Paøasz
Scheme 5
Table 1. Yields and diastereomeric ratios of cycloadducts in reactions
of 1±3 and 19, 20 with 4a±c
Substrates
Cycloadducts
Yield
(%)
Ratio of
cis:trans
1 and 4a
4b
4c
6-cis/6-trans
7-cis
8-cis
86
60
66
65
69
70
67
73
70
73
60
1.4:1
>100:1
>100:1
>100:1
>100:1
4:1
2 and 4b
4c
13-cis
14-cis
3 and 4b
4c
17-cis/17-trans
18-cis
>100:1
4:1
19 and 4b
4c
23-cis/23-trans
24-cis
>100:1
7:1
20 and 4b
4c
25-cis/25-trans
26-cis
>100:1
between the reactivity of acyclic carbonyl compounds possessing cyano or
ethoxycarbonyl groups. The methyl groups attached to the terminal dienophile
systems in¯uenced their reactivity, since the reactions with aldehydes 4b and 4c
were more effective than with 4a and led almost exclusively to the cis-

Intramolecular Hetero Diels-Alder Reactions
801
cycloadducts. We assume that the formation of the cis-diastereoisomers depends on
the structure of the intermediate ꢀ,ꢁ-unsaturated carbonyl compounds. Their H
1
NMR spectra (compounds 5, 9, 12, 15, 16) indicated that they were single isomers,
since the signals of the vinyl protons in ꢀ,ꢁ-unsaturated systems appeared as one
proton singlets. Their chemical shift values strongly suggest that these compounds
are the E-isomers [13]. Thus, due to the cis-linkage of the newly formed rings, we
assume that the hetero-Diels-Alder reaction occurred via an energetically favoured
endo-E-syn transition state [4].
Experimental
Melting points were determined on a Boetius hot stage apparatus; IR spectra: Bruker IFS 48, KBr
pellets; 1H and 13C NMR spectra: Bruker AMX 500 (500.14 MHz for 1H and 125.77 MHz for 13C),
CDCl3, TMS as internal standard, 13C signal assignments were con®rmed by DEPT methods; MS:
Finningan Mat 95 (70 eV); Microanalyses: Perkin Elmer Analyser 240, Regional Laboratory of
Â
Physicochemical Analyses in Krakow; their results were in satisfactory agreement with the
calculated values. 2-Allyloxy-and 2-(3-methyl-2-butenyloxy)-benzaldehydes (4a±b) and 2-(3-
methyl-2-butenyloxy)-1-naphthaldehyde (4c) were obtained according to Ref. [14].
Reactions of compounds 1±3 and 20 with aromatic 2-alkenyloxy aldehydes 4a-c; Synthesis
of condensation products 5, 9, 12, 15, 16, 21, 22, and cycloadducts 7-cis, 8-cis, 14-cis,
18-cis, 23-(cis/trans), 24, 25-(cis/trans) and 26-cis
To a solution of the compounds 1±3, 19, 20 (0.01 mol) in 20 ml of dry acetonitrile, aldehydes 4a±c
(0.01 mol) and 60 mg ethylene diammonium diacetate (EDDA) were added. The solution was stirred
for several hours and left for 24±72 h at room temperature. The progress of the reactions was
monitored by TLC. The solvent was evaporated, and the residue was puri®ed by column
chromatography on silica gel using petrol ether and t-butyl-methyl ether (1:1) as eluent.
Recrystallization from petrol ether and t-butyl-methyl ether (3:1) mixture afforded pale yellow or
colourless crystals of the condensation products or the appropriate cycloadducts.
Synthesis of cycloadducts 6 (cis/trans), 13 cis, 17 (cis/trans) and 18 cis
A solution of the arylidene carbonyl compound 5, 12, or 16 (0.005 mol) in 10 ml anhydrous xylene
was re¯uxed for 24±48 h. The progress of the reactions was monitored by TLC. The solvent was
evaporated, and the mixture was separated and puri®ed by column chromatography on silica gel
using petrol ether and t-butyl-methyl ether (1:1 or 2:1) as eluent. Recrystallization from a mixture of
petrol ether and t-butyl-methyl ether (3:1) gave colourless crystals.
3-(2-Allyloxyphenyl)-2-benzoyl-2-propenecarbonitrile (5; C19H15NO2)
Pale yellow crystals (83%); m.p.: 140ꢀC; IR (KBr): v ˆ 3067, 2910, 2857 (CH), 2220 (C:N), 1645
(C=O), 1594 (C=C) cmꢁ1; 1H NMR (CDCl3, ꢃ): 4.60 (d, J ˆ 5.0 Hz, 2H, 100-H), 5.27 (dd, J ˆ 1.1 Hz,
10.6 Hz, 1H, 300-H), 5.32 (dd, J ˆ 1.1 Hz, 17.3 Hz, 1H, 300-H), 5.99 (m, 1H, 200-H), 6.95±8.39 (m, 9H,
13
CHarom), 8.60 (s, 1H, 3-H) ppm; C NMR (CDCl3, ꢃ): 69.27 (C-100), 109.99 (C-2), 112.37 (C-200),
116.93 (CN), 118.02 (C-300), 121.29 (i-Ph), 121.23, 128.55, 129.31, 129.35, 132.12, 133.07, 134.92
(Carom), 136.09 (i-Ph), 150.44 (C-3), 158.24 (i-Ph), 189.72 (C=O) ppm; MS: m/z (%) ˆ 289.0 (34)
‡Á
‡Á
‡Á
‡Á
[M] , 260.0 (100) [M-CHO] , 232.0 (21) [M-C3H5O] , 105.0 (29) [C6H5CO] , 77.0 (28)
‡Á
[C6H5] .

802
K. Bogdanowicz-Szwed and A. Paøasz
(4aRS,10bRS)-4a,10b-Dihydro-2-phenyl-4H,5H-pyrano[3,4-c][1]benzopyran-1-carbonitrile
(6-cis; C19H15NO2)
Colourless crystals (50%); m.p.: 180ꢀC; IR (KBr): v ˆ 3055, 2979, 2872 (CH), 2201 (C:N), 1605
1
(C=C) cmꢁ1; H NMR (CDCl3, ꢃ): 2.54 (m, 1H, 4a-H), 3.88 (d, J(4a-H,10b-H) ˆ 5.4 Hz, 1H, 10b-
H), 4.16 (dd, J(5-Hax,4a-H) ˆ 8.0 Hz, Jgem ˆ 11.1 Hz, 1H, 5-Hax), 4.30 (dd, J(5-Heq,4a-H) ˆ 2.3 Hz,
Jgem ˆ 11.2 Hz, 1H, 5-Heq), 4.38 (dd, J(4-Hax,4a-H) ˆ 6.0 Hz, Jgem ˆ 11.3 Hz, 1H, 4-Hax), 4.44 (dd,
J(4-Heq,4a-H) ˆ 2.1 Hz, Jgem ˆ 11.2 Hz, 1H, 4-Heq), 6.87±7.7 (m, 9H, CHarom) ppm; 13C NMR
(CDCl3, ꢃ): 29.53 (C-4a), 32.79 (C-10b), 64.46 (C-5), 67.44 (C-4), 86.86 (C-1), 117.1 (CN), 120.56,
121.14, 121.29, 128.26, 128.34, 128.85, 130.72, 130.90, 132.95 (Carom), 153.07 (i-Ph), 164.76 (C-
‡
‡
‡
Á
Á
Á
2) ppm; MS: m/z (%) ˆ 289.2 (100) [M] , 288.2 (45) [M-H] , 260.2 (17) [M-CHO] , 105.0 (67)
‡
‡Á
Á
[C6H5CO] , 77.0 (25) [C6H5] .
(4aRS,10bRS)-4a,10b-Dihydro-2-phenyl-4H,5H-pyrano[3,4-c][1]benzopyran-1-carbonitrile
(6-trans; C19H15NO2)
Colourless crystals (36%); 1H NMR (CDCl3, ꢃ): 2.45 (m, 1H, 4a-H), 3.73 (d, J(4a-H,10b-
H) ˆ 11.2 Hz, 1H, 10b-H), 3.99 (dd, J(4a-H,5-Hax) ˆ 11.7 Hz, Jgem ˆ 10.2 Hz, 1H, 5-Hax), 4.01 (dd,
J(4a-H,4-Hax) ˆ 11.45 Hz, Jgem ˆ 10.4 Hz, 1H, 4-Hax), 4.41 (dd, J(4a-H,5-Heq) ˆ 5.7 Hz,
Jgem ˆ 10.2 Hz, 1H, 5-Heq), 4.56 (dd, J(4a-H,4-Heq) ˆ 3.6 Hz, Jgem ˆ 10.4 Hz, 1H, 4-Heq), 6.88±
8.07 (m, 9H, CHarom) ppm; 13C NMR (CDCl3, ꢃ): 35.62 (C-4a), 35.81 (C-10b), 66.93 (C-5), 68.39
(C-4), 84.00(C-1), 117.15 (CN), 120.61, 121.03, 123,05, 125.63, 128.39, 128.56, 128.85, 131.29,
132.91 (Carom), 154.09 (i-Ph), 168.84 (C-2) ppm.
(4aRS,10bRS)-4a,10b-Dihydro-4,4-dimethyl-2-phenyl-4H,5H-pyrano[3,4-c][1]benzopyran-
1-carbonitrile (7-cis; C21H19NO2)
Colourless crystals (60%); m.p.: 223ꢀC; IR (KBr): v ˆ 3061, 2986, 2885 (CH), 2201 (C:N), 1599
(C=C) cmꢁ1; 1H NMR (CDCl3, ꢃ): 1.55 (s, 3H, 4-CH3), 1.6 (s, 3H, 4-CH3), 2.26 (ddd, J(10b-H,4a-
H) ˆ 5.6 Hz, J(5-Hax,4a-H) ˆ 11.5 Hz, J(5-Heq,4a-H) ˆ 3.7 Hz, 1H, 4a-H), 3.78 (d, J(4a-H, 10b-
H) ˆ 5.5 Hz, 1H, 10b-H), 3.83 (t, J(4a-H, 5-Hax ˆ 11.4 Hz, Jgem ˆ 11.4 Hz, 1H, 5-Hax), 4.43 (ddd,
J(4a-H, 5-Heq) ˆ 3.7 Hz, Jgem ˆ 11.2 Hz, J(10b-H, 5-Heq) ˆ 1.7 Hz, 1H, 5-Heq), 6.87±7.65 (m, 9H,
CHarom) ppm; 13C NMR (CDCl3, ꢃ): 25.52 (C-4a), 25.67 (C-10b), 31.97 (CH3), 36.63 (CH3), 62.53
(C-5), 77.85 (C-4), 86.28 (C-1), 119.51 (CN), 116.48, 120.65, 128.28, 129.05, 130.76, 131.96,
‡
‡
Á
Á
220.1 (100), 173.1 (33) [M-C6H5CO(CN)CH] , 105.0(61) [C6H5CO] , 77.1 (36) [C6H5] , 69.1
133.37 (Carom), 153.82 (i-Ph), 162.64 (C-2); MS: m/z(%) ˆ 317.1(97) [M] , 248.1(27) [M-C5H9]
,
‡
‡
‡
Á
Á
Á
‡
‡
Á
(37) [C5H9] , 41.0 (27) [C3H5]
Á
.
(4aRS,12cRS)-4a,12c-Dihydro-4,4-dimethyl-2-phenyl-4H,5H-naphtho[2,1-b]pyrano[3,4-d]-
pyran-1-carbonitrile (8 cis; C25H21NO2)
Yellow crystals (66%); m.p.: 245ꢀC; IR (KBr): ꢄ ˆ 3061, 2979, 2892 (CH), 2208 (C:N), 1645, 1625,
1603 (C=C) cmꢁ1; 1H NMR (CDCl3, ꢃ): 1.59 (s, 3H, 4-CH3), 1.65 (s, 3H, 4-CH3), 2.26 (ddd, J(12c-
H,4a-H) ˆ 4.3 Hz, J(5-Hax,4a-H) ˆ 12.1 Hz, J(5-Haq,4a-H) ˆ 4.3 Hz, 1H, 4a-H), 4.09 (t, J(4a-H, 5-
Hax) ˆ 11.5 Hz, Jgem ˆ 11.5 Hz, 1H, 5-Hax), 4.52 (dd, J(4a-H,5-Heq) ˆ 2.5 Hz, Jgem ˆ 11.0 Hz, 1H,
5-Heq), 4.55 (d, J(4a-H,12c-H) ˆ 4.1 Hz, 1H, 12c-H), 7.06±8.1 (m, 11H, Carom) ppm; MS: m/z
‡Á
‡Á
‡Á
‡Á
(%) ˆ 367.2 (100) [M] , 298.1 (21) [M-C5H9] , 270.1 (61), 182.1 (15) [M-C6H5CO,CH3,CH3] ,
‡Á
‡Á
‡Á
105.0 (29) [C6H5CO] , 77.0 (20) [C6H5] , 69.1 (11) [C5H9] , 41.1 (15) [C3H5] .
Methyl 3-(2-allyloxy-phenyl)-2-cyano-2-propenylate (9; C14H13NO3)
Yellow crystals (81%); m.p.: 72ꢀC; IR (KBr): v ˆ 2954, 2848 (CH), 2232 (C:N), 1743 (C=O), 1599
1
(C=C) cmꢁ1; H NMR (CDCl3, ꢃ): 3.94 (s, 3H, OCH3), 4.65 (dt, J(200-H, 100-H) ˆ 5.15 Hz, J(300-

Intramolecular Hetero Diels-Alder Reactions
803
H,100-H) ˆ 1.5 Hz, 2H, 100-H), 5.34 (ddd, J(200-H,300-Hcis) ˆ 10.6 Hz, J(100-H,300-Hcis) ˆ 1.4 Hz,
Jgem ˆ 2.7 Hz, 1H, 300-Hcis), 5.44 (ddd, J(200-H,300-Htrans) ˆ 17.3 Hz, J(100-H,300-Hcis) ˆ 1.6 Hz,
Jgem ˆ 2.9 Hz, 1H, 300-Htrans), 6.06 (ddt, J(100-H,200-H) ˆ 5.15 Hz, J(300-Hcis,200-H) ˆ 12.1 Hz, J(300-
Htrans, 200-H) ˆ 17.3 Hz, 1H, 200-H), 6.95 (d, J ˆ 8.4 Hz, 1H, Ph-H), 7.07 (t, J ˆ 7.5 Hz, 1H, CHarom),
7.50 (t, J ˆ 7.9 Hz, 1H, CHarom), 8.31 (d, J ˆ 7.9 Hz, 1H, CHarom), 8.83 (s, 1H, 3-H) ppm; 13C NMR
(CDCl3, ꢃ): 53.18 (OCH3), 69.39 (C-100), 102.03 (C-200), 112.49 (C-300), 115.83 (CN), 118.17,
120.96, 121.14, 129.42, 132.28, 134.92 (Carom), 150.04 (C-2) 158.30 (C-3), 163.29 (C=O) ppm; MS:
‡
‡
‡
‡
Á
Á
Á
m/z(%) ˆ 243.1 (53) [M] , 211.1 (62) [M-CH3OH] , 184.1 (90) [M-CH3OCO] , 183.1 (51),
‡
Á
182.1 (100), 156.1 (19) [M-C3H4O, CH3O] , 145.1 (27) [M-CH3OCO(CN)CH] , 143.1 (36)
Á
‡
‡
Á
[M-CH3OCO, C3H5] , 41.1 (88) [C3H5]
Á
.
8-Allyl-2-oxo-2H-1-benzopyran-3-carbonitrile (11; C13H9NO2)
Lactone 11 was obtained by heating 9 (0.005 mol) in 10 ml anhydrous xylene for 24 h. The progress
of the reaction was monitored by TLC. The solvent was evaporated, and the residue was puri®ed by
column chromatography on silica gel using a mixture of petrol ether and t-butyl-methyl ether (1:1) as
eluent. Recrystallization from a mixture of petrol ether and t-butyl-methyl ether (3:1) gave colourless
crystals.
Yield: 76%; m.p.: 131ꢀC; IR (KBr): v ˆ 3086, 3042, 2973 (CH), 2232 (C:N), 1731 (C=O), 1599
1
(C=C) cmꢁ1; H NMR (CDCl3, ꢃ): 3.62 (d, J(20-H,10-H) ˆ 6.6 Hz, 2H, 10-H), 5.15 (dd, J(20-H, 30-
Hcis ˆ 10.1 Hz, Jgem ˆ 1.5 Hz, 1H, 30-Hcis), 5.16 (dd, J(20-H,30-Htrans) ˆ 16.9 Hz, Jgem ˆ 1.3 Hz, 1H,
30-Htrans), 5.98 (tdd, J(10-H,20-H) ˆ 6.6 Hz, J(30-Hcis, 20-H) ˆ 10.2 Hz, J(30-Htrans, 20-H) ˆ 16.9 Hz,
1H, 20-H), 7.36 (t, J ˆ 7.6 Hz, 1H, CHarom), 7.48 (dd, J ˆ 7.75 Hz, 1.3 Hz, 1H, CHarom), 7.59 (d,
13
J ˆ 7.5 Hz, 1H, CHarom), 8.28 (s, 1H, 4-H) ppm; C NMR (CDCl3, ꢃ): 32.95 (C-10), 103.00 (C-20),
113.00 (C-30), 117.09 (CN), 117.52, 125.41, 127.45, 129.19, 134.37, 136.12 (Carom), 152.12 (C-4),
‡
‡
Á
Á
152.42 (C-3), 156.38 (C-2) ppm; MS: m/z (%) ˆ 211.1 (100) [M] , 183.1 (76) [M-CO] , 182.1
‡
Á
(55), 167.1 (7) [M-CO2] , 154.1 (31).
Methyl 2-cyano-3-(2-(3-methyl-2-butenyloxy)phenyl)-2-propenylate (12; C16H17NO3)
Pale yellow crystals (81%); m.p.: 71ꢀC; IR (KBr): v ˆ 3049, 2948, 2866 (CH), 2220 (C:N), 1724
1
(C=O), 1599 (C=C) cmꢁ1; H NMR (CDCl3, ꢃ): 1.75 (s, 3H, CH3), 1.80 (s, 3H, CH3), 3.93 (s, 3H,
OCH3), 4.62 (d, J ˆ 6.6 Hz, 2H, 100-H), 5.47 (t, J ˆ 6 Hz, 1H, 200-H), 6.97 (d, J ˆ 8.4 Hz, 1H, CHarom),
7.04 (t, J ˆ 7.7 Hz, 1H, CHarom), 7.49 (t, J ˆ 7.9 Hz, 1H, CHarom), 8.30 (d, J ˆ 7.9 Hz, 1H, CHarom
)
‡
‡
Á
8.79 (s, 1H, 3-H) ppm; MS: m/z (%): 271.1 (34) [M] , 212.1 (10) [M-CH3OCO] , 203.1 (13) [M-
C5H8] , 171.0 (48) [M-CH3OCO, CN, CH3] , 145.1 (68) [M-CH3OCO, C5H7] , 69.1 (100)
Á
‡
‡
‡
‡
Á
Á
Á
Á
[C5H9]
.
(4aRS, 10bRS)-4a,10b-Dihydro-2-methyloxy-4H,5H-pyrano [3,4-c][1]benzopyran-1-carbonitrile
(13-cis; C16H17NO3)
Colourless crystals (65%); m.p.: 109ꢀC; IR (KBr): v ˆ 3073, 2998, 2866 (CH), 2195 (C:N), 1618
1
(C=C) cmꢁ1; H NMR (CDCl3, ꢃ): 1.49 (s, 3H, 4-CH3), 1.51 (s, 3H, 4-CH3), 2.14 (m, 1H, 4a-H),
3.75 (s, 3H, OCH3), 3.77 (m, 2H, 5-H), 4.35 (d, J(4a-H, 10b-H) ˆ 10.85 Hz, 1H, 10b-H), 6.81 (d,
J ˆ 7.9 Hz, 1H, CHarom), 6.95 (t, J ˆ 6.9 Hz, 1H, CHarom), 7.17 (t, J ˆ 6.6 Hz, 1H, CHarom), 7.41 (d,
J ˆ 7.3 Hz, 1H, CHarom); 13C NMR (CDCl3, ꢃ): 25.18 (CH3), 25.93 (CH3), 30.22 (C-10b), 37.12 (C-
4a), 54.85 (OCH3), 61.98 (C-5), 62.57 (C-4), 81.22 (C-1), 118.89 (CN), 116.37, 120.42, 120.71,
‡
Á
128.73, 131.30, 131.39 (Carom), 163.49 (C-2) ppm; MS: m/z (%) ˆ 271.1 (87) [M] , 212.1 (13)
‡
‡
Á
[M-CH3OCO] , 196.1 (29), 171.0 (55) [M-CH3OCO, CN, CH3] , 145.1 (88) [M-CH3OCO,
C5H7] , 69.1 (100) [C5H9]
Á
‡
‡
Á
Á
.

804
K. Bogdanowicz-Szwed and A. Paøasz
(4aRS, 12cRS)-4a, 12c-Dihydro-4,4-dimethyl-2-methyloxy-4H,5H-naphtho [2,1-b] pyrano
[4,3-d]pyran-1-carbonitrile (14-cis; C20H19NO3)
Pale yellow crystals (69%); m.p.: 198ꢀC; IR (KBr): v ˆ 3067, 2986, 2860 (CH), 2208 (C:N), 1618
(C=C) cmꢁ1; 1H NMR (CDCl3, ꢃ): 1.55 (s, 3H, 4-CH3), 1.58 (s, 3H, 4-CH3), 2.13 (ddd, J(12c-H,4a-
H) ˆ 4.2 Hz, J(5-Hax,4a-H) ˆ 11.9 Hz, J(5-Heq, 4a-H) ˆ 4.2 Hz, 1H, 4a-H), 3.77 (s, 3H, OCH3), 3.99
(t, J(4a-H, 5-Hax) ˆ 11.5 Hz, Jgem ˆ 11.5 Hz, 5-Hax), 4.41 (br, 2H, 5-Heq, 12c-H), 7.01±8.04 (m, 6H,
‡
‡
Á
Á
CHarom) ppm; MS: m/z (%): 321.2 (90) [M] , 253.1 (52) [M-C5H8] , 246.1 (20) [M-CH3O,
‡
‡
‡
Á
CH2(CH3)2] , 221.1 (100) [M-CH3O, C5H9] , 193.1 (49) [M-CH3OCO, C5H9] , 195.1 (67) [M-
CH3O, C5H9,CN] , 182.1 (57), 139.1 (21), 69.1 (47) [C5H9] , 41.1 (56) [C3H5] .
Á
Á
‡
‡
‡
Á
Á
Á
Ethyl 3-(2-allyloxyphenyl)-2-benzoyl-2-propenylate (15; C21H20O4)
Colourless crystals (78%); m.p.: 60ꢀC; IR (KBr): v ˆ 3080, 3061, 2986 (CH), 1718, 1668 (C=O),
1
1618 (C=C) cmꢁ1; H NMR (CDCl3, ꢃ): 1.16 (t, J ˆ 7.1 Hz, 3H, OC2H5), 4.20 (q, J ˆ 7.1 Hz, 2H,
OC2H5), 4.52 (dd, J(200-H, 1-H00) ˆ 5.0 Hz, J(300-H, 1-H00) ˆ 1.5 Hz, 2H, 100-H), 5.27 (dd, J(200-H,
300-Hcis) ˆ 10.6 Hz, J(100-H, 300-Hcis) ˆ 1.4 Hz, 1H, 300-Hcis), 5.38 (dd, J(200-H, 300-Htrans) ˆ 17.3 Hz,
J(100-H,300-Htrans) ˆ 1.5 Hz, 1H, 300-Htrans), 6.00 (ddt, J(100-H, 200-H) ˆ 5.0 Hz, J(300-Hcis, 200-
H) ˆ 12.0 Hz, J(300-Htrans, 200-H) ˆ 17.3 Hz, 1H, 200-H), 7.17±7.92 (m, 9H, CHarom), 8.36 (s, 1H,
13
3-H) ppm; C NMR (CDCl3, ꢃ): 13.99 (CH3CH2O), 61.26 (CH3CH2O), 69.01 (C-100), 112.19
(C-200), 117.49 (C-300), 120.66, 122.64, 128.55, 129.09, 130.34, 131.09, 131.61, 132.83, 133.40,
136.60 (Carom), 138.41 (C-3), 156.99 (C-2), 165.24 (COOEt), 195.39 (COPh) ppm; MS: m/z
‡
‡
‡
Á
Á
Á
(%) ˆ 336.2 (14.3) [M] , 290.1 (63) [M-C2H5OH] , 279.1 (100) [M-C3H5O] , 263.1 (13) [M-
‡
‡
‡
Á
C6H5CO] , 249.1 (24) [M-C3H5, C2H5OH] , 173.0 (39) [M-C6H5CO,C3H5O, H] , 105.0 (89)
[C6H5CO] , 77.0 (31) [C6H5]
Á
Á
‡
‡
Á
Á
.
Ethyl 2-benzoyl-3-(2-(3-methyl-2-butenyloxy)phenyl)-2-propenylate (16; C23H24O4)
Colourless crystals (81%); m.p.: 62ꢀC; IR (KBr): v ˆ 3055, 2986, 2892 (CH), 1718, 1668 (C=O),
1605 (C=C) cmꢁ1; 1H NMR (CDCl3, ꢃ): 1.16 (t, J ˆ 7.1 Hz, 3H, OC2H5), 1.74 (s, 3H, CH3), 1.79 (s,
3H, CH3), 4.21 (q, J ˆ 7.1 Hz, 2H, OC2H5), 4.52 (d, J ˆ 6.4 Hz, 2H, 100-H), 5.44 (t, J ˆ 6.5 Hz, 1H,
‡
200-H), 6.68±7.95 (m, 9H, CHarom), 8.35 (s, 1H, 3-H) ppm; MS: m/z (%) ˆ 296.1 (17) [M-C5H8]
,
Á
250.1 (33) [M-C5H9, C2H5O] , 221.1 (49) [M-C2H5OCO, C5H9,H] , 219.1 (96) [M-C5H8,
‡
‡
Á
C6H5] , 191.1 (41) [M-C6H5CO, C5H8] , 173.0 (48), 105.0 (100) [C6H5CO] , 69.1 (49) [C5H9] ,
Á
‡
‡
‡
‡
Á
41.0 (30) [C3H5]
Á
Á
Á
‡
Á
.
(4aRS, 10bRS)-4a,10b-Dihydro-4,4-dimethyl-2-phenyl-4H,5H-pyrano[3,4-c][1]benzopyran-
1-ethyl carboxylate (17-cis; C23H24O4)
Oil (56%); IR (KBr): v ˆ 3061, 2986, 2898 (CH), 1711 (C=O), 1649 (C=C) cmꢁ1; 1H NMR (CDCl3,
ꢃ): 0.79 (t, J ˆ 7.2 Hz, 3H, OC2H5), 1.38 (s, 3H, 4-CH3), 1.51 (s, 3H, 4-CH3), 2.17 (ddd, J(10b-H, 4a-
H) ˆ 6.5 Hz, J(5-Hax, 4a-H) ˆ 8.5 Hz, J(5-Heq, 4a-H) ˆ 3.85 Hz, 1H, 4a-H), 385 (m, 2H, OC2H5),
4.19 (d, J(4a-H, 10b-H) ˆ 5.4 Hz, 1H, 10b-H), 4.21 (dd, 4a-H, 5-Hax) ˆ 8.5 Hz, Jgem ˆ 11.3 Hz, 1H,
5-Hax), 4.45 (dd, J(4a-H, 5-Heq) ˆ 3.8 Hz, Jgem ˆ 11.3 Hz, 1H, 5-Heq), 6.76±7.39 (m, 9H,
CHarom) ppm; 13C NMR (CDCl3, ꢃ): 13.48 (OCH2CH3), 24.78 (CH3), 26.59 (CH3), 32.11 (C-10b),
37.84 (C-4a), 60.29 (OCH2CH3), 63.83 (C-5), 107.01 (C-4), 116.01, 120.29, 121.86, 127.81, 127.97,
128.09, 128.75, 130.39 (Carom), 136.55 (i-Ph), 154.09 (C-1), 154.23 (C-2), 169.31 (C=O) ppm; MS:
‡
‡
‡
Á
Á
Á
m/z (%) ˆ 364.2 (54) [M] , 318.2 (59) [M-C2H5OH] , 291.2 (34) [M-C2H5OCO] , 173.1 (34),
‡
‡
‡
Á
Á
105.0 (100) [C6H5CO] , 69.1 (16) [C5H9] , 41.0 (18.1) [C3H5] .
Á

Intramolecular Hetero Diels-Alder Reactions
805
(4aRS, 12cRS)-4a,12c-Dihydro-4,4-dimethyl-2-phenyl-4H,5H-naphtho[2,1-b]-
pyrano[4,3-d]pyran-1-ethyl carboxylate (18-cis; C23H24O4)
Colourless crystals (67%); m.p.: 170ꢀC; IR (KBr): v ˆ 3061, 2979, 2890 (CH), 1705 (C=O), 1624
1
(C=C) cmꢁ1; H NMR (CDCl3, ꢃ): 0.42 (t, J ˆ 7.15 Hz, 3H, OC2H5), 1.52 (s, 3H, 4-CH3), 1.68 (s,
3H, 4-CH3), 2.18 (ddd, J(12c-H, 4a-H) ˆ 4.4 Hz, J(5-Hax, 4a-H) ˆ 4.4 Hz, J(5-Heq, 4a-H) ˆ 11.9 Hz,
1H, 4a-H), 3.14 (dq, J(CH3, OCH2) ˆ 7.1 Hz, Jgem ˆ 10.8 Hz, 1H, OC2H5), 3.41 (dq,
J(CH3,OCH2) ˆ 7.1 Hz, Jgem ˆ 10.8 Hz, 1H, OC2H5), 4.28 (t, (4a-H, 5-Hax) ˆ 11.4 Hz,
Jgem ˆ 11.4 Hz, 1H, 5-Hax), 4.50 (dd, J(4a-H, 5-Heq ˆ 2.7 Hz, Jgem ˆ 10.8 Hz, 1H, 5-Heq), 7.07±
7.88 (m, 11H, CHarom) ppm; 13C NMR (CDCl3, ꢃ): 13.48 (OCH2CH3), 24.78 (CH3), 26.59 (CH3),
32.11 (C-10b), 37.84 (C-4a), 60.29 (OCH2CH3), 63.83 (C-5), 107.01 (C-4), 116.01, 120.29, 121.86,
127.81, 127.97, 128.09, 128.75, 130.39 (Carom), 136.55 (i-Ph), 154.09 (C-1), 154.23 (C-2), 169.31
‡
‡
Á
Á
(C=O) ppm; MS: m/z (%) ˆ 414.2 (100) [M] , 341.2 (13) [M-C2H5OCO] , 223.1 (17) [M-
‡
‡
Á
.
Á
C2H5OCOCH, C6H5CO] , 105.0 (31) [C6H5CO]
(2-Allyloxyphenyl)-bis-(2-hydroxy-6-oxo-1-cyclohexenyl)-methane (21; C22H24O5)
Colourless crystals (50%); m.p.: 186ꢀC; IR (KBr): v ˆ 3230 (OH), 3061, 2961 (CH), 1711 (C=O),
1636, 1605 (C=C) cmꢁ1, 1H NMR (CDCl3, ꢃ): 1.71±3.29 (m, 13H, CH, CH2), 3.67 br, 0.15H, OH),
4.44 (s, 0.85H, OH), 4.53 (m, 2H, OCH2CHCH2), 4.95 (s, 0.55H, OH), 5.23 (m, 1H, OCH2CHCH2),
5.32 (m, 1H, OCH2CHCH2), 5.55 (s, 0.45H, OH), 6.0 (m, 1H, OCH2CHCH2), 6.76±7.18 (m, 4H,
‡
‡
Á
Á
CHarom ppm; MS: m/z (%) ˆ 368.2 (46) [M] , 309.1 (73) [M-C3H5O, 2H] , 213.1 (22) [M-C3H6,
‡
‡
‡
Á
Á
Á
C6H7O2, 2H] , 199.1 (100) [M-C3H5O, C6H7O2, H] , 55.0 (30), 41.0 (17) [C3H5] .
(2-Allyloxyphenyl)-bis-(2-hydroxy-4, 4-dimethyl-6-oxo-1-cyclohexenyl)-methane (22: C26H32O5)
Colourless crystals (56%); m.p.: 190ꢀC, IR (KBr): v ˆ 3387 (OH), 3042, 2947 (CH), 1718 (C=O),
1642, 1609 (C=C) cmꢁ1; 1H NMR (CDCl3, ꢃ): 0.94 (s, 3H, CH3), 1.08 (s, 9H, CH3), 2.11±2.48 (m,
9H, CH, CH2), 4.43 (t, J ˆ 5.5 Hz, 2H, OCH2CHCH2), 5.30 (m, 2H, OCH2CHCH2), 5.62 (s, 1H,
OH), 6.02 (m, 1H, OCH2CHCH2), 6.70±7.5 (m, 4H, CHarom), 12.0 (br, 1H, OH) ppm; 13C NMR
(CDCl3, ꢃ): 29.25, 31.51 42.83, 46.77, 53.54 (CH, CH2, CH3, C(CH3)), 69.04 (C-100), 111.50 (C-200),
117.38 (C-300), 116.39, 120.27, 127.34, 128.27, 128.57, 133.63 (C=C-OH, Carom), 154.0, 156.19
‡
‡
Á
Á
(i-Ph), 189.19 (C=O) ppm; MS: m/z (%) ˆ 424.0 (14) [M] , 365.1 (32) [M-C3H5O, 2H] , 243.1
‡
‡
Á
(12) [M-C3H6, C8H11O2] , 227.1 (100) [M-C3H5O, C8H12O2] , 83.1 (31).
Á
(6aRS, 12bRS)-1,2,3,4,6a,12b-Hexahydro-6,6-dimethyl-6H,7H-[1]benzopyrano
[3,4-c] [1]benzopyran-1-one (23-cis; C18H20O3)
Colourless crystals (58%); m.p.: 153ꢀC; IR (KBr): v ˆ 3086, 2979, 2872 (CH), 1640 (C=O), 1601
(C=C) cmꢁ1; 1H NMR (CDCl3, ꢃ): 1.15 (s, 3H, CH3), 1.48 (s, 3H, CH3), 2.0 (m, 3H, 2-H, 3-H, 4-H),
2.4 (m, 3H, 2-H, 3-H, 4-H), 2.59 (dt, J(12b-H, 6a-H) ˆ 5.7 Hz, 1H, 6a-H), 4.20 (d, J(6a-H, 12b-
H) ˆ 5.7 Hz, 1H, 12b-H), 4.33 (dd, J(6a-H, 7-H) ˆ 3.3 Hz, Jgem ˆ 11.9 Hz, 1H, 7-H), 4.42 (dd, J(6A-
H, 7-H) ˆ 3.7 Hz, Jgem ˆ 11.9 Hz, 1H, 7-H), 6.68±7.19 (m, 4H, CHarom) ppm; 13C NMR (CDCl3, ꢃ):
20.57 (C-6a), 23.96 (C-12b), 27.91, 27.98, 29.56 (C-2, C-3, C-4), 37.25 (CH3), 38.70 (CH3), 64.98
(C-7), 79.84 (C-6), 112.81 (C-12c), 115.69, 120.71, 123.14, 127.44, 129.92, 153.77 (Carom), 170.77
‡
‡
Á
Á
(C-4a), 198.47 (C-1) ppm; MS: m/z (%) ˆ 284.2 (57) [M] , 241.1 (100) [M-(CH3)2CH] , 173.1
‡
Á
(15) [M-C6H7O2]
.
(6aRS,12bSR)-1,2,3,4,6a,12b-Hexahydro-6,6-dimethyl-6H,7H-[1]benzopyrano[3,4-c][1]-
benzopyran-1-one (23-trans; C18H20O3)
Colourless crystals (15%); m.p.: 176ꢀC; 1H NMR (CDCl3, ꢃ): 1.20 (s, 3H, CH3), 1.57 (s, 3H, CH3),
2.02±2.65 (m, 6H, 2-H, 3-H, 4-H), 2.12 (ddd, J(12b-H, 6a-H) ˆ 11.9 Hz, J(7-Hax, 6a-H) ˆ 11.9 Hz,

806
K. Bogdanowicz-Szwed and A. Paøasz
J(7-Heq, 6a-H) ˆ 5.4 Hz, 1H, 6a-H), 3.52 (d, J(6a-H,12b-H) ˆ 11.5 Hz, 1H, 12b-H), 4.03 (dd, J(6a-H,
7-Hax) ˆ 12.1 Hz, Jgem ˆ 9.65 Hz, 1H, 7-Hax), 4.35 (dd, J(6a-H, 7-Heq) ˆ 5.45 Hz, Jgem ˆ 9.65 Hz,
1H, 7-Heq), 6.82±7.09 (m, 4H, CHarom) ppm.
(6aRS,12bRS)-1,2,3,4,6a,12b-Hexahydro-3,3,6,6-tetramethyl-6H,7H-[1]benzopyrano[3,4-c][1]-
benzopyran-1-one (24-cis; C20H24O3)
Colourless crystals (73%); m.p.: 137ꢀC; IR (KBr): v ˆ 3086, 2961, 2872, (CH), 1636 (C=O), 1605
(C=C) cmꢁ1; 1H NMR (CDCl3, ꢃ): 1.08 (s, 3H, 3-CH3), 1.11 (s, 6H, 3-CH3, 6-CH3), 1.49 (s, 3H, 6-
CH3), 2.02 (ddd, J(12b-H, 6a-H) ˆ 5.7 Hz, J(7-H, 6a-H) ˆ 3.0 Hz, J(7-H, 6a-H) ˆ 3.0 Hz, 1H, 6a-H),
2.25±2.47 (m, 4H, 2-H, 4-H), 4.21 (d, J(6a-H, 7-H) ˆ 5.7 Hz, 1H, 12b-H), 4.36 (dd, J(6a-H,
7-H) ˆ 3.0 Hz, Jgem ˆ 12.0 Hz, 1H, 7-H), 4.42 (dd, J(6a-H, 7-H) ˆ 3.7 Hz, Jgem ˆ 12.0 Hz, 1H, 7-H),
6.68 (d, J ˆ 7.9 Hz, 1H, CHarom), 6.81 (t, J ˆ 7.2 Hz, 1H, CHarom), 7.05 (t, J ˆ 7.0 Hz, 1H, CHarom),
‡
‡
Á
,
Á
7.15 (d, J ˆ 7.4 Hz, 1H, CHarom) ppm; MS: m/z (%) ˆ 312.2 (54) [M] , 297.2 (15) [M-CH3]
‡
‡
Á
.
Á
269.1 (100) [M-(CH3)2CH] , 173.1 (14) [M-C8H10O2, H]
(6aRS,14cRS)-1,2,3,4,6a,14c-Hexahydro-6,6-dimethyl-6H,7H-naphtho[10,20:5,6]pyrano[3,4-c][1]-
benzopyran-1-one (25-cis; C22H22O3)
Colourless crystals (61%); m.p.: 203ꢀC; IR (KBr): v ˆ 3067, 2979, 2937 (CH), 1649 (C=O), 1599
(C=C) cmꢁ1; 1H NMR (CDCl3, ꢃ): 1.42 (s, 3H, 6-CH3), 1.48 (s, 3H, 6-CH3), 1.87 (m, 2H, 2-H, 3-H),
2.11 (ddd, J(14c-H, 6a-H) ˆ 4.8 Hz, J(7-Hax, 6a-H) ˆ 11.0 Hz, J(7-Heq, 6a-H) ˆ 6.1 Hz, 1H, 6a-H),
2.19 (t, J ˆ 6.5 Hz, 2H, 4-H), 2.36±2.48 (m, 2H, 2-H, 3-H), 4.12 (t, J(6a-H, 7-Hax) ˆ 10.95 Hz,
Jgem ˆ 10.95 Hz, 1H, 7-Hax), 4.35 (dd, J(6a-H, 7-Heq) ˆ 6.1 Hz, Jgem ˆ 10.4 Hz, 1H, 7-Heq), 4.53 (br,
1H, 14c-H), 6.97 (d, J ˆ 8.8 Hz, 1H, CHarom), 7.32 (t, J ˆ 8.6 Hz, 1H, CHarom), 7.50 (t, J ˆ 7.2 Hz,
1H, CHarom), 7.61 (d, J ˆ 8.8 Hz, 1H, CHarom), 7.72 (d, J ˆ 7.9 Hz, 1H, CHarom), 8.15 (d, J ˆ 8.6 Hz,
‡
‡
Á
Á
1H, CHarom) ppm; MS: m/z (%) ˆ 334.2 (96) [M] , 317.2 (100) [M-OH] , 291.1 (42) [M-
‡
‡
Á
(CH3)2CH] , 249.1 (21) [M-C5H9O] , 223.1 (60), 210.1 (39), 181.1 (18) [M-
C6H6O2,(CH3)2CH] , 69.1 (22) [C5H9] , 57.1 (26) , 41.1 (42) [C3H5] .
Á
‡
‡
‡
‡
Á
Á
Á
Á
(6aRS,14cRS)-1,2,3,4,6a,14c-Hexahydro-3,3,6,6-tetramethyl-6H,7H-naphtho[10,20:5,6]pyrano[3,4-
c][1]benzopyran-1-one (26-cis; C24H26O3)
Colourless crystals (60%); m.p.: 225ꢀC; IR (KBr): v ˆ 3073, 2973, 2866 (CH), 1649 (C=O), 1592
(C=C); 1H NMR (CDCl3, ꢃ): 0.98 (s, 3H, 3-CH3), 1.03 (s, 6H, 3-CH3), 1.42 (s, 3H, 6-CH3), 1.48 (s,
3H, 6-CH3), 2.11 (m, 1H, 6a-H), 2.03 (d, J ˆ 16.2 Hz, 1H, 4-H), 2.10 (d, J ˆ 16.2 Hz, 1H, 4-H), 2.29
(s, 2H, 2-H), 4.09 (t, J(6a-H, 7-Hax) ˆ 10.85 Hz, Jgem ˆ 10.85 Hz, 1H, 7-Hax), 4.35 (dd, J(6a-H,7-
Heq) ˆ 6.3 Hz, Jgem ˆ 10.7 Hz, 1H, 7-Heq), 4.52 (br, 1H, 14c-H), 6.97±8.15 (m, 6H, Charom) ppm;
‡
‡
‡
Á
Á
Á
MS: m/z (%) ˆ 362.2 (100) [M] , 345.2 (56) [M-OH] , 319.1 (52) [M-(CH3)2CH] , 277.1 (15)
‡
‡
‡
Á
[M-C5H9O] , 223.1 (57) [M-C8H10O2, H] , 41.1 (18) [C3H5] ,
Á
Á
References
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[2] Tietze LF (1983) Ang Chem Int Ed Engl 22: 828
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807
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134
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Received November 2, 1998. Accepted November 19, 1998