Reactions of allyl alcohols of the pinane series and of their epoxides in the presence of montmorillonite clay

Article abstract of DOI:10.1002/hlca.200790042

The reactivity of allyl alcohols of the pinane series and of their epoxides in the presence of montmorillonite clay in intra- and intermolecular reactions was studied. Mutual transformations of (+)-trans-pino-carveol ((+)-2) and (-)-myrtenol ((-)-3a) were major reactions of these compounds on askanite-bentonite clay (Schemes 1 and 2). However, the two reactions gave different isomerization products, indicating that the reactivity of the starting alcohol (+)-2 or (-)-3a was different from that of the same compound (+)-2 or (-)-3 formed in the course of the reactions, (-)-cis- and (+)-trans-Verbenol ((-)-16 and (+)-12, resp.), as well as (-)-cis-verbenol epoxide ((-)-20) reacted with both aliphatic and aromatic aldehydes on askanite-bentonite clay giving various heterocyclic compounds (Schemes 4, 5 and 7); the reaction path depended on the structure of both the terpenoid and the aldehyde.

Full text of DOI:10.1002/hlca.200790042

Helvetica Chimica Acta – Vol. 90 (2007)
353
Reactions of Allyl Alcohols of the Pinane Series and of Their Epoxides in the
Presence of Montmorillonite Clay
by Irina V. Ilꢀina, Konstantin P. Volcho*, Dina V. Korchagina, Vladimir A. Barkhash, and Nariman F.
Salakhutdinov
N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of
Sciences, 630090 Novosibirsk, Russian Federation
(fax: +73833309752; e-mail: volcho@nioch.nsc.ru)
The reactivity of allyl alcohols of the pinane series and of their epoxides in the presence of montmor-
illonite clay in intra- and intermolecular reactions was studied. Mutual transformations of (+)-trans-pino-
carveol ((+)-2) and (ꢀ)-myrtenol ((ꢀ)-3a) were major reactions of these compounds on askanite–ben-
tonite clay (Schemes 1 and 2). However, the two reactions gave different isomerization products, indicat-
ing that the reactivity of the starting alcohol (+)-2 or (ꢀ)-3a was different from that of the same com-
pound (+)-2 or (ꢀ)-3 formed in the course of the reactions. (ꢀ)-cis- and (+)-trans-Verbenol ((ꢀ)-16
and (+)-12, resp.), as well as (ꢀ)-cis-verbenol epoxide ((ꢀ)-20) reacted with both aliphatic and aromatic
aldehydes on askanite–bentonite clay giving various heterocyclic compounds (Schemes 4, 5 and 7); the
reaction path depended on the structure of both the terpenoid and the aldehyde.
Introduction. – Interest in the chemistry of pinane terpenes and their O-containing
derivatives is largely dictated by the accessibility of these substances, which are more
widespread in nature than any other monoterpenes or their derivatives [1]. Due to
their chemical reactivity and high optical purity, pinanes may be employed as substrates
to obtain compounds potentially useful as synthons in asymmetric synthesis [2]. In acid
media, however, pinenes and their derivatives generally undergo numerous transfor-
mations, giving complex mixtures of products, which is one of the obstacles to a wide
application of these compounds in fine organic chemistry [1]. For example, acid-cata-
lyzed isomerization of a-pinene oxide may yield up to two hundred products [3]. There-
fore, reactions of pinane terpenoids in the presence of crystalline acidic aluminosilicate
catalysts (clays, zeolites) are of considerable interest because of the possibility to bring
about processes with drastically increased selectivity or an even unknown reaction
pathway [3][4] (clay microreactors are known to occasionally display enzyme-like char-
acteristics [4][5]).
The interesting and unexpected data obtained in our previous study of the behavior
of (ꢀ)-verbenone epoxide (1) in the presence of montmorillonite clay [6]1) prompted us
to investigate transformations of other compounds of the pinane series under the same
1
)
Aseries of new polyfunctional optically active heterocyclic compounds ( a-hydroxy ketones, a-dike-
tones, ketoaldehyde) was obtained. Important biological activity has recently been found in bicyclic
ethers of this kind: compounds with a 3-oxabicyclo[3.3.1]nonane framework showed activity as estro-
gen receptor a and b agonists [7].
ꢀ 2007 Verlag Helvetica Chimica Acta AG, Zürich

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conditions. For the object of this investigation, we took a number of accessible optically
active alcohols: (+)-trans-pinocarveol ((+)-2), (ꢀ)-myrtenol ((ꢀ)-3a), and verbenols
(+)-12 and (ꢀ)-16. The choice of these terpenoids is dictated by several reasons: 1)
these are widespread reactive pinenes possessing high optical purity; 2) their behavior
in the presence of aluminosilicate catalysts has not yet been studied; 3) these terpenoids
are allyl alcohols that differ only in the position of the double bond and hydroxy group,
which allows an easy comparison of the results; 4) their epoxides are readily accessible
and thus can substantially expand the synthetic potential of the transformations being
studied.
Results and Discussion. – (+)-trans-Pinocarveol ((+)-2) and Myrtenol ((ꢀ)-3a). As
is known from the literature, in the presence of mineral acids, (+)-trans-pinocarveol
((+)-2) is mostly converted into fenchyl derivatives [8] (Scheme 1), while (ꢀ)-myrtenol
((ꢀ)-3a) forms either hydrocarbons when boiled with 10% sulfuric acid [9] or myrtenol
acetate with AcOH [9]. When we exposed (+)-2 for 3 h at room temperature to askan-
ite–bentonite clay (its synthetic analog is the commercially available clay K10), the
products isolated from the reaction mixture were unchanged alcohol (+)-2 (conversion
75%), (ꢀ)-myrtenol ((ꢀ)-3a; 33%), and the condensation product (+)-4 (11%); the
given yields refer to converted alcohol (+)-2 (Scheme 1)2). Compound 4 is probably
formed by reaction of carbocation A with (+)-2. Interestingly, despite the presence
of two alcohols in comparable proportion in the reaction mixture and their potential
to add at two positions of cation A, only compound (+)-4 was formed in appreciable
amounts besides (ꢀ)-3a.
Scheme 1. Transformations of (+)-trans-Pinocarveol ((+)-2) on Askanite-Bentonite Clay
When (ꢀ)-myrtenol ((ꢀ)-3a) was kept on askanite–bentonite clay for 1 h at room
temperature, the products were (+)-trans-pinocarveol ((+)-2; 9%), perillyl alcohol
((ꢀ)-5; 12%), and para-cymene derivative 6 (6%) (yields relative to converted (ꢀ)-
3a, conversion 44%; Scheme 2). Since the reaction mixture contains products with a
2
)
Trivial or arbitrary atom numbering; for systematic names, see Exper. Part.

Helvetica Chimica Acta – Vol. 90 (2007)
355
para-menthane framework, it follows that isomerization of (ꢀ)-3a occurs not only via
formation of carbocation A from the protonated enol but also, obviously, via double-
bond protonation with subsequent skeletal rearrangement of the resulting carbocation
into cation B. Despite the high optical purity of the starting (ꢀ)-myrtenol ((ꢀ)-3a), the
products of its isomerization had lower optical-activity characteristics than those
reported in the literature. This is indicative of a racemization process occurring during
the reaction. Thus, the specific rotation [a]580 was +9.1 (c=3, CHCl3) for (+)-trans-
pinocarveol ((+)-2) obtained from (ꢀ)-myrtenol ((ꢀ)-3a) ([10]: [a]D =+52 (CHCl3)
for pure (+)-2) and ꢀ17 (c=3, CHCl3) for perillyl alcohol (5) ([11]: [a]D =ꢀ121
(neat)). At the same time, (ꢀ)-myrtenol ((ꢀ)-3a) formed from (+)-2 (see Scheme 1)
20
has a rather high optical purity ([a] =ꢀ40 (c=25, CHCl3); [12]: [a]25800 =ꢀ50.6
580
(CHCl3)).
Scheme 2. Transformations of (ꢀ)-Myrtenol ((ꢀ)-3a) on Askanite–Bentonite Clay
Thus mutual transformations are the main reaction paths of (+)-trans-pinocarveol
((+)-2) and (ꢀ)-myrtenol ((ꢀ)-3a) in the presence of askanite–bentonite clay. In both
cases, the reaction mixture contained (+)-2 and (ꢀ)-3a. However, ꢁnonoverlappingꢂ iso-
merization products unexpectedly formed in each case, which actually means that clay
is able to ꢁdistinguishꢂ between two states of the same compound (the state of the start-
ing compound applied to clay and the state of the reaction product). Note that the
behavior of (+)-trans-pinocarveol ((+)-2) and (ꢀ)-myrtenol ((ꢀ)-3a) on clay differs
substantially from their reactivity in the presence of mineral acids [8][9].
(ꢀ)-Myrtenol Epoxide ((ꢀ)-8) and (+)-trans-Pinocarveol Epoxide ((+)-7). (+)-
trans-Pinocarveol epoxide ((+)-7) was prepared by oxidation of (+)-trans-pinocarveol
((+)-2) with monoperphthalic acid in 33% yield according to [13]. (ꢀ)-Myrtenol epox-
ide ((ꢀ)-8a) was synthesized in 32% yield by oxidation of (ꢀ)-myrtenol ((ꢀ)-3a) with
peracetic acid according to [14] or by reduction of (ꢀ)-myrtenal epoxide ((ꢀ)-9) with
LiAlH4 according to [15] (53%) (Scheme 3).
As in the case of the starting alcohols, storage of the epoxides (+)-7 and (ꢀ)-8 on
clay gave unexpected results. Although the reactions were expected to yield identical
cations due to cleavage of the protonated oxirane rings, isomerization products partly
formed from only one particular starting compound. Thus, storage of (+)-pinocarveol
epoxide ((+)-7) on askanite–bentonite clay for 1 h at room temperature gave a com-
plex product mixture from which we isolated (+)-pinocarvone ((+)-10; 6%) and cam-

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Helvetica Chimica Acta – Vol. 90 (2007)
Scheme 3. Transformations of (+)-Pinocarveol Epoxide ((+)-7) and (ꢀ)-Myrtenol Epoxide ((ꢀ)-8a)
on Clay
pholenic aldehyde analog (+)-11a; 19%)3) (Scheme 3). Transformations of (ꢀ)-myrte-
nol epoxide ((ꢀ)-8a) on clay under the same conditions yielded an aromatic alcohol 6
(16%) with a para-menthane framework and compound (+)-11a (27%) (Scheme 3). It
should be emphasized that 6 was not formed from epoxide (+)-7, and ((+)-10) did not
result from epoxide ((ꢀ)-8a). This may be explained, for example, by differences of
adsorption of the epoxides (+)-7 and (ꢀ)-8a on clay4).
The behavior of (ꢀ)-myrtenol epoxide ((ꢀ)-8a) in the presence of askanite–benton-
ite clay is similar to the previously studied transformations of its homologue (ꢀ)-nopol
epoxide ((ꢀ)-8b) on montmorillonite clays [17]5). We have not found any publications
on the behavior of pinocarveol epoxide and myrtenol epoxide in acid media.
Pinocarveol (+)-2, myrtenol (ꢀ)-3a, and their epoxides (+)-7 and (ꢀ)-8a, as well as
(ꢀ)-nopol ((ꢀ)3b) and its epoxide (ꢀ)-8b, did not react with the aldehydes prop-2-enal,
(2E)-but-2-enal, 2-hydroxybenzalaldehyde, or 4-methoxybenzaldehyde in the presence
of askanite–bentonite clay.
3
)
)
)
Racemic compound 11a has been synthesized earlier by reaction of 6-exo-hydroxy-2,10-epoxycam-
phane with HClO4 [16].
4
5
Intramolecular assistance of the primary-alcohol function in the oxirane-ring opening of (ꢀ)-8a may
eventually afford a stereoisomer of hydroxy epoxide (+)-7 as an intermediate.
The transformations of the latter compound also gave a campholenic aldehyde analog and three
compounds with a para-menthane framework as the major products obtained on cooling. The reac-
tivity of (ꢀ)-nopol epoxide ((ꢀ)-8b) on clay differed substantially from that in the presence of ZnBr2,
when aldehyde (+)-11b was obtained as a sole product [18].

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Verbenols. As mentioned above, verbenol which can be accessible in the form of cis-
and trans-isomers, was another alcohol from the pinane series which we chose for our
investigation. According to GC/MS data, storage of (+)-trans-verbenol ((+)-12) on
askanite–bentonite clay for 40 min at room temperature afforded para-cymene (13;
39%), 2-(4-methylcyclohexa-2,4-dienyl)propan-2-ol (14; 20%) and 2-(2-methylcyclo-
hexa-2,4-dienyl)propan-2-ol (15; 15%) as the major products (Scheme 4). These results
are in good agreement with the literature data on the behavior of verbenol in various
acids (storage in the presence of sulfuric acid [19], treatment with acetic anhydride in
the presence of clay K-10 [20])6).
Scheme 4. Transformations of Verbenols on Askanite–Bentonite Clay
We investigated the behavior of the cis-stereoisomer (ꢀ)-cis-verbenol ((ꢀ)-16) on
askanite–bentonite clay in the presence of (2E)-but-2-enal or 2-hydroxybenzaldehyde
and found compounds (+)-17 or (+)-18, optical antipodes of the corresponding heter-
ocyclic compounds obtained from (+)-trans-verbenol ((+)-12)6) (Scheme 4). Thus the
relative arrangement of the OH group in the starting verbenol did not affect the occur-
rence and direction of intermolecular reactions. Moreover, replacement of the OH
group by a MeO group in passing from (+)-trans-verbenol ((+)-12) to (ꢀ)-trans-verbe-
6
)
Previously, we showed that on askanite–bentonite clay, (+)-trans-verbenol ((+)-12) undergoes
unusual reactions with aliphatic and aromatic aldehydes, resulting in heterocyclic compounds [21].
These transformations were accompanied by a skeletal rearrangement of the starting alcohol (+)-
12, presumably forming a carbocation with a para-menthane framework which reacted with alde-
hydes. This was followed by intramolecular carbocyclization, leading to cyclic ethers.

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nol methyl ether ((ꢀ)-19) did not change the reaction route either (Scheme 4). The
presence of an OH group (or its ether) at C(4), however, is of critical importance in
these reactions because verbenone (having an oxo substituent at C(4)), (ꢀ)-myrtenol
((ꢀ)-3a; OH group at C(10)), and a-pinene (no O-containing substituents) do not
react with aldehydes on askanite–bentonite clay. It is noteworthy that the bicyclic
ether (+)-17 formed from (ꢀ)-cis-verbenol ((+)-16) has a much smaller optical rota-
tion than the same compound obtained from (+)-trans-verbenol (+)-12 or (ꢀ)-trans-
verbenol methyl ether ((ꢀ)-19). Obviously, during the reaction of alcohol (ꢀ)-16
with (2E)-but-2-enal, carbocyclization in cation D occurs less stereoselectively than
in the case of the reactions of (+)-12 or (ꢀ)-19 with (2E)-but-2-enal. This may be
explained, for example, by differences in adsorption of the starting compounds on clay.
(ꢀ)-cis-Verbenol Epoxide ((ꢀ)20). (ꢀ)-cis-Verbenol epoxide ((ꢀ)-20) could not be
synthesized by epoxidation of (ꢀ)-cis-verbenol ((ꢀ)-16) with conventional oxidants
(peracetic, monoperphthalic, or meta-chloroperbenzoic acid) because of the high labil-
ity of alcohol (ꢀ)-16 and its epoxide in acid media. Instead of the desired epoxide, we
obtained a complex mixture of isomerization products. Therefore, epoxy alcohol (ꢀ)-20
was prepared by an alternative procedure, namely, by reduction of (ꢀ)-verbenone
epoxide (1) with LiAlH4 according to [15], which gave the cis-isomer (ꢀ)-20 as the
sole product; therefore, trans-verbenol epoxide was not prepared, and its reactivity
with clay was not investigated. Storage of epoxide (ꢀ)-20 on askanite–bentonite clay
for 40 min at room temperature produced trans-diol (ꢀ)-21 with a para-menthane
framework as a major product (47%) and hydroxy ketone (ꢀ)-22 as a minor product
(5%) (Scheme 5). Previously, compound (ꢀ)-22 has been synthesized as a major prod-
uct in a study of the behavior of (ꢀ)-cis-verbenol epoxide ((ꢀ)-20) in the presence of
ZnBr2 [22]. In our case, however, this compound formed only as a minor product.
trans-Diol (ꢀ)-21 was not found in the literature and may be regarded as a precursor
of a promising chiral ligand for an asymmetric metal-complex catalyst7). As in the
case of compounds (+)-2, (ꢀ)-3a, and (ꢀ)-8b, epoxy alcohol (ꢀ)-20 showed pro-
nounced differences in reactivity in the presence of clay on one hand and of conven-
tional acid catalysts on the other hand.
We found that in the presence of montmorillonite clay (ꢀ)-cis-verbenol epoxide
((ꢀ)-20) underwent intermolecular reactions with both aromatic and aliphatic alde-
hydes. In the reaction of (ꢀ)-20 with 4-methoxybenzaldehyde in the presence of clay
for 40 min at room temperature, in addition to the isomerization products (ꢀ)-21
(33%) and (ꢀ)-22 (7%), we also isolated compound (ꢀ)-23 (13%). The hypothetical
mechanism leading to (ꢀ)-23 includes protonation and cleavage of the oxirane ring,
skeletal rearrangement into a cation with a para-menthane framework, and its subse-
quent interaction with aldehyde (Scheme 5). Interestingly, at the last stage of this mech-
anism, heterocyclization in the resulting cation E is preferable to carbocyclization, as
previously observed in reactions of other O-containing terpenoids of the pinane series
[6][21]. When performed on synthetic montmorillonite clay K-10, this reaction gave
the same products (GC/MS data) as in the case of the reaction carried out on an askan-
ite–bentonite clay, but the product ratio changed, the content of the intermolecular-
7
)
A cis-isomer of compound (ꢀ)-21 has previously been obtained as one of the minor products during
oxidation of 3-carene with thallium acetate [22].

Helvetica Chimica Acta – Vol. 90 (2007)
359
Scheme 5. Isomerization of( ꢀ)-cis-Verbenol Epoxide ((ꢀ)-20) on Askanite–Bentonite Clay
reaction product (ꢀ)-23 increasing substantially and hydroxy ketone (ꢀ)-22 being prev-
alent among isomerization products. When montmorillonite clays were replaced by
zeolite Hb, compound (ꢀ)-23 vanished from the reaction mixture almost completely
(GC/MS data).
It can be seen from Scheme 6 that the structure of the cations possibly formed from
trans- and cis-verbenols (+)-12 and (ꢀ)-16, respectively, verbenone epoxide (1), and
pinene epoxides during the interaction of these compounds with aldehydes on clay is
very similar to the structure of cation E, believed to be formed from cis-verbenol epox-
ide ((ꢀ)-20). While in five cases, we obtained exclusively the products of carbocycliza-
tion that took place at the last stage of the reaction, verbenol epoxide (ꢀ)-20 gave only
the product of heterocyclization. Thus, with montmorillonite clay used as a catalyst,
even relatively minor changes in the structure of a terpenoid can change the reaction
path drastically.
Interaction of epoxide (ꢀ)-20 with 2-hydroxybenzaldehyde on clay occurred in
much the same way as in the case of 4-methoxybenzaldehyde, yielding trans-diol
(ꢀ)-21 (51%) and compound 24 in minor amounts (4%) (Scheme 5).
Anew reaction path appeared on passing from aromatic aldehydes to the aliphatic
(2E)-but-2-enal. Interaction of epoxide (ꢀ)-20 with (2E)-but-2-enal for 1 h at room

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Helvetica Chimica Acta – Vol. 90 (2007)
Scheme 6
temperature yielded not only compound (ꢀ)-25 (16%), an analog of compounds (ꢀ)-23
and 24, and as the isomerization products (ꢀ)-21 (13%) and (ꢀ)-22 (5%), but also a
mixture of two diastereoisomers 26a,b (9% and 5%, resp.), whose isomerism is due
to the different orientation of the substituents at C(5) (Scheme 7). Moreover, we also
isolated a small amount of triol 27 from the reaction mixture. Scheme 7 shows a possi-
ble mechanism for the formation of 26a,b; one can see that diol (ꢀ)-21 can act as an
intermediate neutral species in this reaction. To verify this assumption, we carried
out a control experiment in which diol (ꢀ)-21 was stored in the presence of (2E)-
but-2-enal on clay for 2 h. Amixture of diastereoisomers 26a,b (26a/26b 1:0.14) was
formed in a total yield of 35% based on converted diol (ꢀ)-21 (conversion 52%).
This result confirmed that diol (ꢀ)-21 can be an intermediate in the synthesis of com-
pounds 26a,b from epoxide (ꢀ)-20.
All products containing stereogenic centers obtained were optically active.
Structure Elucidation ofReaction Products. Compounds (+)-4, (ꢀ)-21, (ꢀ)-23, 24,
(ꢀ)-25, 26a, 26b, and 27 are not described in the literature. They were identified
from 1H- and 13C-NMR data taking into account the configurations of the starting ter-
penoids.
1
3
In the H-NMR spectrum of compound (+)-17, the coupling constant J(1,2) is 2.5 Hz [21], analo-
3
gous to J(4,12)=3 Hz in the spectrum of (+)-18 [21], indicating that HꢀC(2) of (+)-17 and HꢀC(4)
of (+)-18 are in the exo-position. The absence of W-coupling between these protons and the protons
of the CH2 bridge confirms that the former have an exo-position in both compounds. Quantum-mechan-
ical calculations suggest that the six-membered heterocycle adopts a chair conformation in (+)-17 and a
boat-like conformation in (+)-18 (Scheme 4).
In the 13C-NMR spectrum of (ꢀ)-21, the signals of C(1) and C(2) and the signals of the Me groups
were assigned by means of the long-range 13C,1H J modulated differential (LRJMD) spectrum. When the
olefinic HꢀC(4) signal at d(H) 5.56 was suppressed, the LRJMD spectrum showed a d at d(C) 71.82 and a
q at d(C) 20.72, assigned to C(2) and C(10), respectively, as well as the expected d at d(C) 39.82 (C(6))

Helvetica Chimica Acta – Vol. 90 (2007)
361
Scheme 7. Interaction of( ꢀ)-cis-Verbenol Epoxide ((ꢀ)-20) with (2E)-But-2-enal on Askanite–Ben-
tonite Clay
and t at d(C) 24.65 (C(5)). In the 1H-NMR spectrum, the low value of 3J(1,2) (=3 Hz) points to the equa-
torial position of HꢀC(1) and HꢀC(3). The coupling constants between HaꢀC(5) and HꢀC(6) are much
higher (J(5a,6)=11 Hz), indicating that the latter has an axial orientation. From the foregoing, one can
conclude that the substituents at C(1) and C(6) are in cis-configuration relative to each other and in trans-
configuration relative to the substituent at C(2).
1
3
In the H-NMR spectra of compounds (ꢀ)-23–26a,b, the corresponding vicinal constants J(1,6),
3J(1,10), and J(6,7) are virtually identical. Therefore, ring fusion may be assumed to be the same in
3
all these compounds. Since 3J(1,6)=2 Hz, which points to coupling of protons in the e,e or e,a conforma-
tion, cis-fusion of the six-membered rings is suggested in these cases. For compound (ꢀ)-23, 3J(1,6)=2 Hz
indicates that an isomer with cis ring fusion is formed because in the case of the trans-isomer, the angular
protons would occupy the axial positions and hence the coupling constant would be much larger. By anal-
ogy with cis-decalin, one can assume with certain allowances that both six-membered rings have a chair
3
conformation. The high coupling constants J(6,7)ꢁ11 and 6–7 Hz suggest that HꢀC(6) is axial in the
cyclohexene ring in all cases, and hence HꢀC(1) has an equatorial conformation. In this situation, the
low value of 3J(1,10) (<3 Hz) reflects e,e coupling between HꢀC(1) and HꢀC(10).
For compounds 26a and 26b, the 3J(3,4) suggest that HꢀC(3) is axial in both cases. For compounds
(ꢀ)-23, 24, and (ꢀ)-25, therefore, HꢀC(3) may also be assumed to have axial conformations, and the
bulkier substituents at C(3) are assumed to occupy equatorial positions.
From the foregoing it follows that in all compounds (ꢀ)-23–26a,b, HꢀC(1) and HꢀC(10) are equa-
torial, while HꢀC(3) and HꢀC(6) are axial. Isomers 26a and 26b arise from the different arrangements of
substituents at C(5); the Me group is axial in 26a, as indicated by the presence of the long-range 4J(Me,4a)
of 0.8 Hz, but equatorial in 26b. In the latter case, as would be expected, the axial OH group causes a
paramagnetic shift Dd= 0.42 and 0.34 of the HꢀC(1) and HꢀC(3) signal, respectively, due to the 1,3-dia-
xial interaction.
In the 13C-NMR spectrum of (ꢀ)-23, the signals of C(1) and C(10), as well as of C(9) and C(11), were
assigned based on LRJMD spectral data. In the former case, after suppression of the signal of the olefinic
HꢀC(8) at d(H) 5.60, the LRJMD spectrum contained ds at d(C) 70.33 and 33.98, a t at d(C) 23.04, and a
q at d(C) 20.6, assigned to C(10), C(6), C(7), and C(20), respectively. In the latter case, when the HꢀC(1)
signal at d(H) 4.3 was suppressed, among the low-field s of interest was a s at d(C) 130.89 assigned to C(9)
in the LRJMD spectrum. Structure 28, as an alternative for (ꢀ)-23, was rejected based on the 13C-NMR
spectrum of a CCl4/CDCl3 solution after D2O addition. Due to the isotope effect in this solution, replace-

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Helvetica Chimica Acta – Vol. 90 (2007)
ment of OH by OD led to an upfield shift of the d at d(C) 70.33 (Dd=0.12) assigned to C(10) in the struc-
ture (ꢀ)-23. In the case of 28, the isotope effect would be exhibited for a d appearing at d(C) 75.0. Signal
assignments in the 13C-NMR spectra of compounds 24–26a,b and structure elucidation were performed
by analogy with those of (ꢀ)-23. For compound 27 the presence of OH groups was established by the 13C-
NMR spectrum of a CDCl3 solution after D2O addition. Due to the isotope effect in this solution, replace-
ment of OH by OD led to upfield shifts of the d at d(C) 71.04 and 72.16 and the s at d(C) 73.25 (Dd 0.12,
0.18, and 0.16 resp.).
Conclusions. – The above results and our previous investigations [6][21] represent a
systematic study of the reactivity of pinane alcohols ((+)-trans-pinocarveol ((+)-2),
(ꢀ)-myrtenol ((ꢀ)-3a), (ꢀ)-cis-verbenol ((ꢀ)-16), (+)-trans-verbenol ((+)-12), and
(ꢀ)-nopol ((ꢀ)-3b)] and of their epoxides (except for trans-verbenol epoxide) in the
presence of acidic montmorillonite clay.
It was shown that on askanite–bentonite clay, these compounds undergo various
transformations, mostly accompanied by skeletal rearrangements of the pinane frame-
work and generally leading to a different set of products as compared to the products
obtained in the presence of conventional homogeneous acids.
Mutual transformations of (+)-trans-pinocarveol ((+)-2) and (ꢀ)-myrtenol ((ꢀ)-
3a) are the major reactions of these compounds on askanite–bentonite clay. In each
case, however, the reactions gave different isomerization products, indicating that the
reactivity of the starting alcohols was different from that of the same compounds
formed in the course of reactions. The clay also proved very sensitive to minor changes
in the structure of the terpenoids during the transformations of (+)-pinocarveol epox-
ide ((+)-7) and (ꢀ)-myrtenol epoxide ((ꢀ)-8a) in the presence of clay. Although fully
identical cations were expected to be formed during cleavage of the protonated oxirane
rings of these compounds, some isomerization products formed from only one particu-
lar starting compound.
Storage of (ꢀ)-cis-verbenol epoxide ((ꢀ)-20) in the presence of clay afforded 1,2-
trans-diol ((ꢀ)-21) with a para-menthane framework as the major product. cis- and
trans-Verbenols, as well as cis-verbenol epoxide, reacted with both aliphatic and aro-
matic aldehydes on askanite–bentonite clay, giving various heterocyclic compounds;
the reaction path depended on the structure of both the terpenoid and the aldehyde.
Thus, in the presence of clay, the reactivity of O-containing terpenoids of the pinane
series depends considerably on even minor changes of their structure.
The authors are grateful to the Presidium ofRussian Academy ofSciences for financial support (com-
plex program N 18).

Helvetica Chimica Acta – Vol. 90 (2007)
363
Experimental Part
1. General. As catalyst, we used askanite–bentonite clay obtained (according to Specs TU-113-12-86-
82) by acidic activation of bentonite clays from the Askan group of deposits; a synthetic analog of this
clay is K10. The clay was calcinated at 1108 for 3 h immediately before use. GLC (purity control and
product analyses); 3700 instrument; quartz capillary column (15 m”0.22 mm), VC-30 phase, flame-ion-
ization detector, He (1 atm) as carrier gas. Column chromatography (CC): silica gel (70–230 mesh;
Merck); 1–95% gradient Et2O/hexane. Optical rotation: Polamat-A spectrometer; CHCl3 soln. 1H-
and 13C-NMR Spectra: Bruker AM-400 apparatus at 400.13 MHz (1H) and 100.61 MHz (13C); in CCl4/
CDCl3 1:1 (v/v); chemical shifts d in ppm rel. to residual CHCl3 (d(H) 7.24, d(C) 76.90), J in Hz; assign-
ments by Js and 1H,1H double-resonance spectra, and by considering the 13C-NMR spectra under proton
off-resonance saturation, including 13C,1H-type 2D-COSY (1J(C,H)=135 Hz), and 13C,1H-type 1D-
LRJMD (J(C,H)=10 Hz) spectra. HR-MS: Finnigan MAT-8200 instrument; in m/z.
2. Transformations of (+)-trans-Pinocarveol (=(1R,3S,5R)-6,6-Dimethyl-2-methylenebicyclo[3.1.1]-
heptan-3-ol; (+)-2) on Askanite–Bentonite Clay. To a suspension of askanite–bentonite clay (0.3 g) in
CH2Cl2 (10 ml) was added a soln. of (+)-trans-pinocarveol (2; 0.300 g; [a]25800 =+53 (c=23); obtained
in 82% yield by oxidation of b-pinene (Fluka) with t-BuOOH in the presence of SeO2 according to
[24]) in CH2Cl2 (10 ml). The mixture was stirred for 3 h at 208. Then Et2O (5 ml) was added. The catalyst
was filtered off and the solvent evaporated. The resulting mixture was separated by CC (silica gel (10 g)):
(+)-2 (0.075 g, 25%), (+)-4 (0.046 g, 11%), and (ꢀ)-3a (0.075 g, 33%; [a]25800 =ꢀ40 (c=25)); yields given
based on converted (+)-2.
Data of(1 R,5S)-2-{[(1R,3S,5R)-6,6-Dimethyl-2-methylenebicyclo[3.1.1]hept-3-yloxy]methyl}-6,6-
dimethylbicyclo[3.1.1]hept-2-ene ((+)-4): [a]25800 =+20 (c=20). 1H-NMR2): 0.63 (s, Me(9’)); 0.83 (s,
Me(9)); 1.18 (d, J(7anti,7syn)=8.5, HantiꢀC(7)); 1.26 (s, Me(8’)); 1.27 (s, Me(8)); 1.78 (d, J(7’anti,
7’syn)=10, HantiꢀC(7’)); 1.84–1.97 (m, HꢀC(5’), HꢀC(4’)); 2.04–2.17 (m, HꢀC(1), HꢀC(5), Hꢀ
C(4’)); 2.22–2.29 (m, 2 HꢀC(4)); 2.26 (m, HsynꢀC(7’)); 2.37 (ddd, J=8.5, J(7syn,1)=5.5, J(7syn,
5)=5.5, HsynꢀC(7)); 2.43 (dd, J(1’,7’)=5.5, J(1’,5’)=5.5, HꢀC(1’)); 3.73 (ddt, J(10a,10b)=12.5, J(10a,
3)=1.5, J(10a,4)=1.5, HaꢀC(10)); 3.88 (ddt, J=12.5, J(10b,3)=1.5, J(10b,4)=1.5, HbꢀC(10)); 3.89
(br. d, J(3’,4’)=7.5, HꢀC(3’)); 4.80 (br. s, 2HꢀC(10’)); 5.40–5.46 (m, HꢀC(3)). 13C-NMR2): 21.19 (q,
C(9)); 22.01 (q, C(9’)); 26.25 (q, C(8’)); 26.39 (q, C(8)); 26.93 (t, C(7’)); 31.31 (t, C(4)); 31.60 (t, C(7));
32.89 (t, C(4’)); 38.04 (s, C(6)); 39.75 (d, C(5’)); 41.00 (d, C(5)); 41.42 (s, C(6’)); 43.56 (d, C(1)); 50.74
(d, C(1’)); 70.08 (t, C(10)); 72.81 (d, C(3’)); 112.55 (t, C(10’)); 119.05 (d, C(3)); 145.93 (s, C(2)); 150.20
(s, C(2’)). HR-MS: 286.22968 (M+, C20H30O+; calc. 286.22965).
3. Transformations of (ꢀ)-Myrtenol (=(1R,5S)-6,6-Dimethylbicyclo[3.1.1]hept-2-ene-2-methanol;
(ꢀ)-3a) on Askanite–Bentonite Clay. As described in Exper. 2, with (ꢀ)-myrtenol ((ꢀ)-3a; 0.500 g;
[a]25080 =ꢀ54 (c=12.5); obtained in 89% yield by reduction of (ꢀ)-myrtenal (Aldrich, ꢁpurity 98%ꢂ,
20
580
[a] =ꢀ11.4 (c=17)) with NaBH4 according to [25]) in CH2Cl2 (5 ml) and askanite–bentonite clay
(0.5 g) in CH2Cl2 (15 ml) for 1 h at 208. Workup with Et2O (5 ml) followed by CC (silica gel (15 g)):
(ꢀ)-3a (0.282 g, conversion 44%; [a]25800 =ꢀ43 (c=10)), (+)-trans-pinocarveol ((+)-2; 21 mg, 9%;
[a]25080 =9.1 (c=3)), perillyl alcohol ((ꢀ)-5; 12%; [a]52800 =ꢀ17 (c=3)), and 4-isopropylbenzenemethanol
(6; 6%); yields given based on converted (ꢀ)-3a). Compounds (ꢀ)-5 and 6: 13C-NMR identical with
reported data [26].
4. Transformations of (+)-trans-Pinocarveol Epoxide (=(1R,2R,3S)-6,6-Dimethylspiro[bicy-
clo[3.1.1]heptane-2,2’-oxiran]-3-ol; (+)-7) on Askanite–Bentonite Clay. (+)-trans-Pinocarveol epoxide
((+)-7; [a]25800 =+34 (c=15)) was synthesized in 58% yield by oxidation of (+)-trans-pinocarveol ((+)-
2) with monoperphthalic acid according to [13]. Data of 7: corresponding to those reported in [27].
Then as described in Exper. 2, with (+)-7 (0.300 g) in CH2Cl2 (5 ml) and askanite–bentonite clay (0.3
g) in CH2Cl2 (10 ml) for 1 h at 208. Workup with Et2O (5 ml) followed by CC (silica gel (15 g)): (+)-pino-
carvone ((+)-10; 0.015 g, 6%; [a]25800 =+10 (c=10)) and 11a (0.056 g, 19%).
Data of(1 R)-3-(Hydroxymethyl)-2,2-dimethylcyclopent-3-ene-1-acetaldehyde ((+)-11a): [a]25800 =+20
(c=20). 1H-NMR2): 0.85 (s, Me(9)); 1.04 (s, Me(8)); 1.91 (ddtd, J(5,5’)=16, J(5,1)=8.5, J(5,10)=2.5, J(5,
4)=2, HꢀC(5)); 2.25–2.34 (m, HꢀC(1)); 2.36 (ddd, J(6,6’)=12, J(6,1)=10, J(6,7)=2, HꢀC(6)); 2.46
(ddddd, J=16, J(5’,1)=7.5, J(5’,4)=3, J(5’,10)=1.5, J(5’,10’)=2, H’ꢀC(5)); 2.46–2.51 (m, H’ꢀC(6));

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Helvetica Chimica Acta – Vol. 90 (2007)
4.08 (dddd, J(10,10’)=14, J(10,5)=2.5, J(10,5’)=1.5, J(10,4)=1.5, HꢀC(10)); 4.13 (dddd, J=14, J(10’,
5)=2.5, J(10’,5’)=2, J(10’,4)=1.5, H’ꢀC(10)); 5.52 (ddt, J(4,5’)=3, J(4,5)=2, J(4,10)=1.5, HꢀC(4));
9.75 (t, J(7,6)=2, HꢀC(7)). 13C-NMR2): 35.52 (t, C(2)); 44.49 (t, C(6)); 44.72 (d, C(1)); 46.28 (s, C(5));
123.00 (d, C(3)); 151.65 (s, C(4)); 201.54 (d, C(7)); 25.80 (q, C(8)); 20.96 (q, C(9)); 59.57 (t, C(10)).
HR-MS: 167.107723 ([Mꢀ1]+, C10H15O2þ ; calc. 167.10720).
5. Transformations of (ꢀ)-Myrtenol Epoxide (=(1R,2S,4S,6R)-7,7-Dimethyl-3-oxabicyclo[4.1.1.02,4}-
octane-2-methanol; (ꢀ)-8a) on Askanite–Bentonite Clay. (ꢀ)-Myrtenol epoxide ((ꢀ)-8a) was prepared in
two ways. In the first procedure, epoxide (ꢀ)-8a was obtained by oxidation of (ꢀ)-myrtenol ((ꢀ)-3a) with
peracetic acid according to [14]. After purification by CC, the yield of (ꢀ)-8a was 32%. In the second
procedure, oxidation of (ꢀ)-myrtenal (Acros) with 35% aq. H2O soln. in the presence of 6N NaOH
according to [28] gave (ꢀ)-myrtenal epoxide ((ꢀ)-9) in 74% yield. Subsequent reduction with LiAlH4
according to the procedure of [15] gave (ꢀ)-8a (53%). [a]25800 =ꢀ88 (c=8). H-NMR2): 0.90 (s, Me(9));
1
1.27 (s, Me(8)); 1.64 (d, J(7,7’)=10, HꢀC(7)); 1.70–1.76 (m, HꢀC(5)); 1.87 (dddd, J(4’,4)=15, J(4’,
3)=4, J(4’,5)=3, J(4’,7’)=2, H’ꢀC(4)); 1.93 (dd, J(1,5)=5.5, J(1,7’)=5.5, HꢀC(1)); 2.01 (dd, J=15,
J(4,5)=3, HꢀC(4)); 1.97–2.05 (m, H’ꢀC(7)); 3.30 (dd, J(3,4’)=4, J(3,5)=1, HꢀC(3)); 3.50 (d, J(10,
10’)=13, HꢀC(10)); 3.67 (d, J=13, H’ꢀC(10)). 13C-NMR2): 40.72 (d, C(1)); 63.67 (s, C(2)); 52.88 (d,
C(3)); 27.21 (t, C(4)); 40.31 (d, C(5)); 40.57 (s, C(6)); 25.63 (t, C(7)); 26.65 (q, C(8)); 20.18 (q, C(9));
62.69 (t, C(10)). HR-MS: 153.09107 ([Mꢀ15]+, C9H13O2þ ; calc. 153.09155).
Then as described in Exper. 2, with (ꢀ)-8a (0.188 g) in CH2Cl2 (5 ml) and askanite–bentonite clay
(0.3 g) in CH2Cl2 (10 ml) for 40 min at r.t. Workup with Et2O (5 ml) followed by CC (silica gel (10 g)):
6 (0.027 g, 16%) and (+)-11a (0.050 g, 27%; [a]25820 =+20.7 (c=8)).
6. (ꢀ)-cis-Verbenol (=(1S,2S,5S)-4,6,6-Trimethylbicyclo[3.1.1]hept-3-en-2-ol; (ꢀ)-16) and (ꢀ)-trans-
Verbenol Methyl Ether (=(1S,4R,5S)-4-Methoxy-2,6,6-trimethylbicyclo[3.1.1]hept-2-ene; (ꢀ)-19). (ꢀ)-
cis-Verbenol ((ꢀ)-16; [a]25800 =ꢀ10 (c=5)) was prepared by reduction of (ꢀ)-verbenone (Acros; purity
20
94%; [a] =ꢀ176 (c=20)) with NaBH4 in MeOH according to [25]. 1H- and 13C-NMR: identical
580
with those reported in [28] and [29], resp. This reaction gave (ꢀ)-trans-verbenol methyl ether ((ꢀ)-19
(22%; [a]25080 =ꢀ55 (c=0=6)) as a by-product. 1H- and 13C-NMR: identical with those reported
in [30].
7. Interaction of( ꢀ)-cis-Verbenol ((ꢀ)-16) with (2E)-But-2-enal on Askanite–Bentonite Clay. Asoln.
of (2E)-but-2-enal (0.12 g) in CH2Cl2 (3 ml) was added to a suspension of askanite–bentonite clay (0.3 g)
in CH2Cl2 (3 ml). Then a soln. of (ꢀ)-16 (0.120 g) in CH2Cl2 (3 ml) was added dropwise. The mixture was
stirred for 60 min at r.t. Then Et2O (5 ml) was added. The catalyst was filtered off and the solvent evapo-
rated. The resulting mixture was separated by CC (silica gel (5 g)): (1S,2R,5R)-4,4-dimethyl-8-methylene-
2-(prop-1-enyl)-3-oxabicyclo[3.3.1]non-6-ene ((+)-17; 0.033 g, 21%; [21]: 26%). [a]15890 =+18 (c=9) ([21]:
[a]D =ꢀ85 for enantiomer). 1H- and 13C-NMR: identical with those reported in [21].
8. Interaction of( ꢀ)-cis-Verbenol ((ꢀ)-16) with 2-Hydroxybenzaldehyde on Askanite–Bentonite Clay.
As described in Exper. 7, with 2-hydroxybenzaldehyde (0.12 g) in CH2Cl2 (3 ml), askanite–bentonite clay
(0.3 g) in CH2Cl2 (3 ml), and (ꢀ)-16 (0.100 g) in CH2Cl2 (3 ml) for 40 min at r.t. Workup with Et2O (3 ml)
followed by CC (silica gel (5 g)): (4S,8R)-2,2,8-trimethyl-3,7-dioxa-5,6-benzotricyclo[6.2.2.04,12]dodec-9-
ene (=(2R,5R,8S,13R)-5,6-Dihydro-2,6,6-trimethyl-5,2,8-ethanylylidene-2H,8H-1,7-benzodioxecin; (+)-
19
18; 0.059 g, 35%; [21]: 12%). [a] =+9 (c=19) ([21]: [a]D =ꢀ26.7 for enantiomer). 1H- and 13C-
580
NMR: identical with those reported in [21].
9. Interaction of( ꢀ)-trans-Verbenol Methyl Ether ((ꢀ)-19) with (2E)-But-2-enal on Askanite–Benton-
ite Clay. As described in Exper. 7, with (2E)-but-2-enal (0.30 g) in CH2Cl2 (5 ml), askanite–bentonite clay
(1.5 g) in CH2Cl2 (10 ml), and (ꢀ)-19 (0.300 g) in CH2Cl2 (5 ml) for 40 min at r.t. Workup with Et2O (5
ml) followed by CC (silica gel (10 g)): (+)-17 (0.090 g, 24%; [a]15890 =+83.5 (c=5)). Spectral data: iden-
tical with those reported in [21].
10. Interaction of( ꢀ)-trans-Verbenol Methyl Ether ((+)-19) with 2-Hydroxybenzaldehyde on Askan-
ite–Bentonite Clay. As described in Exper. 7, with 2-hydroxybenzaldehyde (0.12 g) in CH2Cl2 (3 ml),
askanite–bentonite clay (0.3 g) in CH2Cl2 (3 ml), and (ꢀ)-19 (0.100 g) in CH2Cl2 (3 ml) for 40 min at
r.t. Workup with Et2O (3 ml) followed by CC (silica gel (5 g)): (+)-18 (0.143 g, 30%). [a]15890 =+10
(c=13)). Spectral data; identical with those reported in [21].

Helvetica Chimica Acta – Vol. 90 (2007)
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11. (ꢀ)-cis-Verbenol Epoxide (=(1R,2R,4S,5R,6S)-2,7,7-Trimethyl-3-oxatricyclo[4.1.1.02,,4]octan-5-
ol; (ꢀ)-20). (ꢀ)-Verbenone epoxide (1; 1.0 g); ([6]: [a]25800 =ꢀ137 (c=3.5)) was added to a suspension
of LiAlH4 (0.24 g) in Et2O (5 ml) at 08. The mixture was stirred for 4.5 h at 08. Then H2O (5 ml) was
added, the mixture stirred for 5 min and extracted with Et2O, the extract dried (K2CO3), and the solvent
evaporated: (ꢀ)-20 (0.84 g, 83%). [a]25800 =ꢀ44 (c=12). 1H-NMR2): 1.05 (s, Me(8)); 1.25 (s, Me(9)); 1.32
(s, Me(10)); 1.34 (d, J(7anti,7syn)=9.5, HantiꢀC(7)); 1.83–1.91 (m, HꢀC(1), HꢀC(5)); 1.91–1.99 (dm,
J(7syn,7anti)=9.5, HantiꢀC(7)); 2.70 (br. s, OH); 2.96 (d, J=2, HꢀC(3)); 4.03 (d, J(4,5)=3, HꢀC(4)).
13C-NMR2): 45.30 (d, C(1)); 60.55 (s, C(2)); 60.30 (d, C(3)); 69.95 (d, C(4)); 46.70 (d, C(5)); 40.62 (s,
C(6)); 22.07 (t, C(7)); 27.17 (q, C(8)); 22.07 (q, C(9)); 21.97 (q, C(10)). HR-MS: 168.11486 (M+,
C10H16Oþ2 ; calc. 168.11502).
12. Transformation of (ꢀ)-cis-Verbenol Epoxide ((ꢀ)-20) on Askanite–Bentonite Clay. As described
in Exper. 2, with (ꢀ)-(20) (0.200 g) in CH2Cl2 (7 ml) and askanite–bentonite clay (0.5 g) in CH2Cl2 (8 ml)
for 40 min at 208. Workup with Et2O (5 ml) followed by CC (silica gel (10 g)): (ꢀ)-21 (0.094 g, 47%) and
(ꢀ)-22 (0.009 g, 5%).
Data of(1 R,2R,6S)-3-Methyl-6-(1-methylethenyl)cyclohex-3-ene-1,2-diol ((ꢀ)-21): [a]25800 =ꢀ46
(c=18). 1H-NMR2): 1.75 (dddd, J(10,5a)=2.5, J(10,4)=1.5, J(10,5e)=1.5, J(10,2)=1, Me(10)); 1.78
(br. s, Me(9)); 1.93 (dddq, J(5e,5a)=17.5, J(5e,4)=5, J(5e,6a)=5, J(5e,10)=1.5, HeꢀC(5)); 2.16
(dddqd, J=17.5, J(5a,6a)=11, J(5a,4)=2.5, J(5a,10)=2.5, J(5a,2)=1, HaꢀC(5)); 2.35 (br. dd, J(6a,
5a)=11, J(6a,5e)=5, HaꢀC(6)); 2.44 (br. s, 2 OH); 3.77 (br. d, J(2,1)=3, HꢀC(2)); 3.82 (dd, J(1,
2)=3, J(1,6)=2, HꢀC(1)); 4.79 and 4.88–4.92 (br. s and m, 2 HꢀC(8)); 5.56 (ddq, J(4,5e)=5, J(4,
5a)=2.5, J(4,10)=1.5, HꢀC(4)). 13C-NMR2): 71.39 (d, C(1)); 71.82 (d, C(2)); 131.76 (s, C(3)); 124.89
(d, C(4)); 24.65 (t, C(5)); 39.82 (d, C(6)); 145.67 (s, C(7)); 111.46 (t, C(8)); 22.55 (q, C(9)); 20.72 (q,
C(10)). HR-MS: 168.11503 (M+, C10H16Oþ2 ; calc. 168.11502).
Data of(1 S)-2-Hydroxy-1-(2,2,3-trimethylcyclopent-3-enyl)ethanone ((ꢀ)-22): [a]25800 =ꢀ20.7
(c=8.2). 1H-NMR2): 0.81 (s, Me(9)); 1.20 (s, Me(8)); 1.58 (ddd, J(10,4)=2.5, J(10,5’)=2.5, J(10,
5)=1.5, Me(10)); 2.26 (dddq, J(5,5’)=16, J(5,1)=8, J(5,4)=3, J(5,10)=1.5, HꢀC(5)); 2.68 (ddqd,
J=16, J(5’,1)=9, J(5’,10)=2.5, J(5’,4)=2, H’ꢀC(5)); 2.87 (dd, J(1,5’)=9, J(1,5)=8, HꢀC(1)); 3.20
(br. s, OH); 4.16 (br. d, J(7,7’)=19, HꢀC(7)); 4.23 (br. d, J=19, H’ꢀC(7)); 5.22 (dqd, J(4,5)=3, J(4,
10)=2.5, J(4,5’)=2, HꢀC(4)); broadening of the HꢀC(7) signals because of the interactions with the
OH proton, but sharp narrowing of these signals in the 1H,1H double-resonance spectrum due to signal
suppression at d 3.20. 13C-NMR2): 58.41 (d, C(1)); 49.15 (s, C(2)); 145.80 (s, C(3)); 121.08 (d, C(4)); 31.06
(t, C(5)); 210.20 (s, C(6)); 69.12 (t, C(7)); 27.34 (q, C(8)); 21.17 (q, C(9)); 12.20 (q, C(10)). HR-MS:
168.11520 (M+, C10H16Oþ2 ; calc. 168.11502).
13. Interaction of( ꢀ)-cis-Verbenol Eepoxide ((ꢀ)-20) with 4-Methoxybenzaldehyde on Askanite–
Bentonite Clay. As described in Exper. 7, with 4-methoxybenzaldehyde (0.3 g) in CH2Cl2 (4 ml), askan-
ite–bentonite clay (0.8 g) in CH2Cl2 (7 ml), and (ꢀ)-20 (0.3 g) in CH2Cl2 (4 ml) for 40 min at 208. Workup
with Et2O (5 ml) followed by CC (silica gel (10 g)): (ꢀ)-21 (0.099 g, 33%), (ꢀ)-22 (0.021 g, 7%), and (ꢀ)-
23 (0.071 g, 13%).
Data of(2 S,4aR,8R,8aR)-4a,5,8,8a-Tetrahydro-2-(4-methoxyphenyl)-4,4,7-trimethyl-4H-1,3-benzo-
dioxin-8-ol ((ꢀ)-23). [a]25800 =ꢀ43 (c=20). 1H-NMR2): 1.23 (s, Me(18)); 1.49 (s, Me(17)); 1.47 (ddd,
J(6a,7a)=11, J(6a,7e)=6, J(6a,1e)=2, HꢀC(6a)); 1.78 (ddd, J(20,7a)=2.5, J(20,7e)=1.5, J(20,
8)=1.5, Me(19)); 2.03 (dddq, J(7e,7a)=17.5, J(7e,6)=6, J(7e,8)=6, J(7e,20)=1.5, HeꢀC(7)); 2.43
(dddqd, J=17.5, J(7a,6)=11, J(7a,8)=2.5, J(7a,20)=2.5, J(7a,10)=1.5, HaꢀC(7)); 3.75 (s, MeO);
3.77–3.80 (m, HꢀC(10)); 4.25 (dd, J(1e,10)=2.5, J(1e,6)=2, HeꢀC(1)); 5.60 (ddq, J(8,7e)=6, J(8,
7a)=2.5, J(8,20)=1.5, HꢀC(8)); 5.69 (s, HꢀC(3)); 6.81 (d, J=8 , HꢀC(13), HꢀC(15)); 7.33 (d, J=8,
HꢀC(12), HꢀC(16)). 13C-NMR2): 20.63 (q, C(19)); 22.75 (q, C(17)); 23.04 (t, C(7)); 27.29 (q, C(18));
33.98 (d, C(6)); 54.98 (q, MeO); 70.33 (d, C(10)); 74.35 (s, C(5)); 75.04 (d, C(1)); 95.70 (d, C(3));
113.41 (d, C(13), C(15)); 125.14 (d, C(8)); 127.61 (d, C(12), C(16)); 130.89 (s, C(9)); 131.51 (s, C(11));
159.83 (s, C(14)). HR-MS: 304.16725 (M+, C18H24O4+; calc. 304.16745).
14. Interaction of( ꢀ)-cis-Verbenol Epoxide ((ꢀ)-20) with 2-Hydroxybenzaldehyde on Askanite–Ben-
tonite Clay. As described in Exper. 7, with 2-hydroxybenzaldehyde (0.35 g) in CH2Cl2 (5 ml), askanite–

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bentonite clay (1.0 g) in CH2Cl2 (10 ml), and (ꢀ)-20 (0.330 g) in CH2Cl2 (5 ml) for 60 min at 208. Workup
1
with Et2O (5 ml) followed by CC (silica gel (10 g)): 0.187 g of a 10 :1 mixture (by H-NMR) of (ꢀ)-21
(51%) and 24 (4%).
Data of(2 S,4aR,8R,8aR)-4a,5,8,8a-Tetrahydro-2-(2-hydroxyphenyl)-4,4,7-trimethyl-4H-1,3-benzo-
dioxin-8-ol (24): 1H-NMR2): 1.25 (s, Me(18)); 1.17 (s, Me(18)); 1.55 (ddd, J(6a,7)=11, J(6a,7’)=6,
J(6a,1)=2, HꢀC(6)); 1.74–1.77 (m, Me(19)); 2.07 (dddq, J(7’,7)=18, J(7’,6)=6, J(7’,8)=5, J(7’,
19)=1.5, H’ꢀC(7)); 2.29–2.41 (m, HꢀC(7)); 3.81 (br. s, HꢀC(10)); 4.29 (dd, J(1,10)=2.5, J(1,6a)=2,
HꢀC(1)); 5.58–5.62 (m, HꢀC(8)); 5.87 (s, HꢀC(3)); 6.74–6.80 (m, HꢀC(13), HꢀC(15)); 7.06 (dd,
J(16,15)=8, J(16,14)=1.8, HꢀC(16)); 7.13 (td, J(14,13(15))=8, J(14,16)=1.8, HꢀC(14)); 7.87 (s,
OHꢀC(12)). 13C-NMR2): 20.60 (q, C(19)); 22.45 (q, C(17)); 22.97 (t, C(7)); 26.99 (q, C(18)); 33.74 (d,
C(6)); 69.77 (d, C(10)); 75.25 (d, C(1)); 75.54 (s, C(5)); 97.26 (d, C(3)); 117.08 (d, C(13)); 119.38 (d,
C(15)); 122.09 (s, C(11)); 124.63 (d, C(8)); 128.04 (d, C(16)); 130.06 (d, C(14)); 130.97 (s, C(9));
155.41 (s, C(12)).
15. Interaction of( ꢀ)-cis-Verbenol Epoxide ((ꢀ)-20) with (2E)-But-2-enal on Askanite–Bentonite
Clay. As described in Exper. 7, with (2E)-but-2-enal (0.4 g) in CH2Cl2 (5 ml), askanite–bentonite clay
(1.5 g) in CH2Cl2 (15 ml), and (ꢀ)-(20) (0.400 g) in CH2Cl2 (5 ml) for 60 min at r.t. Workup with Et2O
(5 ml) followed by CC (silica gel (10 g)): (ꢀ)-21 (0.052 g, 13%), (ꢀ)-22 (0.019 g, 5%), (ꢀ)-25 (0.088 g,
1
1
16%), 26a/26b 1:0.4 (by H-NMR; 0.043 g) and 26a/26b/27 1:0.7:0.4 (by H-NMR; 0.036 g), i.e., yield
8.5% for 26a, 4.6% for 26b, and 1% for 27.
Data of(2 S,4aR,8R,8aR)-4a,5,8,8a-Tetrahydro-4,4,7-trimethyl-2-[(1E)-prop-1-enyl]-4H-1,3-benzo-
1
dioxin-8-ol ((ꢀ)-25): [a]25800 =ꢀ66 (c=10). H-NMR: 1.15 (s, Me(14)); 1.38 (s, Me(15)); 1.66 (dd, J(13,
12)=6.5, J(13,11)=2, Me(13)); 1.75 (br. s, Me(16)); 1.37 (ddd, J(6a,7)=11, J(6a,7’)=6, J(6a,1)=2,
HaꢀC(6)); 1.93 (dddq, J(7’,7)=17.5, J(7’,6)=6, J(7’,8)=5, J(7’,16)=1.5, H’ꢀC(7)); 2.28 (dddqd, J(7,
7’)=17.5, J(7,6a)=11, J(7,8)=2.5, J(7,16)=2.5, J(7,10)=2, HꢀC(7)); 2.68 (br. s, OH); 3.72–3.75 (m,
HꢀC(10)); 4.09 (dd, J(1,10)=2.5, J(1,6a)=2, HꢀC(1)); 5.13 (d, J(3,11)=6, HꢀC(3)); 5.44 (ddq, J(11,
12)=15.5, J(11,3)=6, J(11,13)=2, HꢀC(11)); 5.55 (ddq, J(8,7’)=5, J(8,7)=2.5, J(8,16)=1.5, Hꢀ
C(8)); 5.80 (dqd, J(12,11)=15.5, J(12,13)=6.5, J(12,3)=0.5, HꢀC(12)). 13C-NMR: 17.523 (q, C(13));
20.62 (q, C(16)); 22.68 (q, C(15)); 22.87 (t, C(7)); 27.17 (q, C(14)); 33.83 (d, C(6)); 70.23 (d, C(10));
73.85 (s, C(5)); 74.51 (d, C(1)); 95.46 (d, C(3)); 125.24 (d, C(8)); 128.87 (d, C(11)); 130.15 (d, C(12));
130.72 (s, C(9)). HR-MS: 238.15711 (M+, C14H22O3þ ; calc. 238.15688).
Data of(2 S,4R,4aS,8R,8aR)-3,4,4a,5,8,8a-Hexahydro-4,7-dimethyl-2-[(1E)-prop-1-enyl]-2H-1-ben-
zopyran-4,8-diol (26a; main isomer): 1H-NMR (from mixture 26a/26b)2): 1.42 (d, J(14,4a)=0.8,
Me(14)); 1.47 (ddd, J(4e,4a)=13, J(4e,3a)=3, J(4e,6a)=1, HeꢀC(4)); 1.65 (dd, J(13,12)=6.5, J(13,
11)=2, Me(13)); 1.69 (br. dd, J(4a,4e)=13, J(4a,3a)=11.5, HaꢀC(4)); 1.73 (dddd, J(6a,7)=10.5, J(6a,
7’)=7, J(6a,1)=2, J(6a,4e)=1, HaꢀC(6)); 1.77–1.80 (m, Me(15)); 2.00–2.17 (m, 2 HꢀC(7)); 3.65 (dd,
J(1,10)=2.5, J(1, 6a)=2, HꢀC(1)); 3.83 (ddddq, J(3a,4a)=11.5, J(3a,11)=7, J(3a,4e)=3, J(3a,12)=1,
J(3a,13)=0.5, HaꢀC(3)); 3.86 (br. s, HꢀC(10)); 5.45 (ddq, J(11,12)=15,5, J(11,3)=7, J(11,13)=2, Hꢀ
C(11)); 5.58–5.62 (m, HꢀC(8)); 5.68 (dqd, J(12,11)=15.5, J(12,13)=6.5, J(12,3)=1, HꢀC(12)). 13C-
NMR: 17.63 (q, C(13)); 20.67 (q, C(15)); 22.58 (t, C(7)); 27.09 (q, C(14)); 38.34 (d, C(6)); 41.28 (t,
C(4)); 70.57 (d, C(10)); 70.80 (s, C(5)); 76.43 (d, C(3)); 77.22 (d, C(1)); 124.79 (d, C(8)); 128.00 (d,
C(11)); 131.25 (d, C(12)); 131.32 (s, C(9)).
Data of(2 S,4S,4aS,8R,8aR)-3,4,4a,5,8,8a-Hexahydro-4,7-dimethyl-2-[(1E)-prop-1-enyl]-2H-4-ben-
1
zopyran-4,8-diol (26b; minor isomer): H-NMR (from mixture 26a/26b)2): 1.19 (s, Me(14)); 1.41 (ddd,
J(4e,4a)=14, J(4e,3a)=3, J(4e,6a)=1.2, HeꢀC(4)); 1.57 (dd, J(4a,4e)=14, J(4a,3a)=11.5, HaꢀC(4));
1.59 (m, HꢀC(6)); 1.64 (dd, J(13,12)=6.5, J(13,11)=2, Me(13)); 1.77–1.80 (m, Me(15)); 1.80–1.93
(m, HꢀC(7)); 1.92–2.01 (m, H’ꢀC(7)); 3.88 (br. s, HꢀC(10)); 4.07 (dd, J(1,10)=2.5, J(1,6)=2, Hꢀ
C(1)); 4.17 (ddddq, J(3a,4a)=11.5, J(3a,11)=7, J(3a,4e)=3, J(3a,12)=1, J(3a,13)=0.5, HaꢀC(3));
5.43 (ddq, J(11,12)=15.5, J(11,3)=7, J(11,13)=2, HꢀC(11)); 5.52–5.56 (m, HꢀC(8)); 5.68 (dqd, J(12,
11)=15.5, J(12,13)=6.5, J(12,3)=1, HꢀC(12)); d of HꢀC(6) was determined by 2D 13C,1H correlated
1
spectroscopy on direct constants; after suppression of the HꢀC(8) signal at d 5.54 in the H,1H dou-
ble-resonance spectrum, J(7,7’)=17 Hz for the HꢀC(7) signal and J(7’,7)=17 Hz, J(7’,6)=7 Hz, and

Helvetica Chimica Acta – Vol. 90 (2007)
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J(7’,6)=2 Hz for the H’ꢀC(7) signal. 13C-NMR2): 17.66 (q, C(13)); 20.77 (q, C(15)); 24.47 (t, C(7)); 28.37
(q, C(14)); 38.08 (d, C(6)); 40.13 (t, C(4)); 70.50 (s, C(5)); 70.57 (d, C(10)); 74.68 (d, C(1)); 74.72 (d,
C(3)); 124.17 (d, C(8)); 127.71 (d, C(11)); 131.64 (d, C(12)); 131.81 (s, C(9)).
Data of(1 R,2R,6R)-6-(1-Hydroxy-1-methylethyl)-3-methylcyclohex-3-ene-1,2-diol (27): 1H-NMR
(from mixture 26a/26b/27)2): 1.23 (s, Me(9)); 1.38 (s, Me(10)); 1.60–1.65 (m, HꢀC(6)); 1.77–1.81 (m,
Me(7)); 2.07–2.16 (m, HeꢀC(5)); 2.23–2.35 (ddm, J(5a,5e)=18, J(5a,6a)=11, HaꢀC(5)); 3.77 (br. d,
J(2,1)=3, HeꢀC(2)); 4.29 (br. dd, J(1,2)=3, J(1,6)=1.5, HeꢀC(1)); 5.58–5.62 (m, HꢀC(4)). 13C-
NMR2): 20.72 (q, C(10)); 20.89 (q, C(7)); 21.31 (t, C(5)); 28.54 (q, C(9)); 39.82 (d, C(6)); 71.04 (d,
C(1)); 72.16 (d, C(2)); 73.25 (s, C(8)); 125.72 (d, C(4)); 131.09 (s, C(3)).
16. Interaction ofDiol (ꢀ)-21 with (2E)-But-2-enal on Askanite–Bentonite Clay. Asoln. of (2 E)-But-
2-enal (0.05 g) and (ꢀ)-21 (0.05 g) in CH2Cl2 (1 ml) was added to a suspension of askanite–bentonite clay
(0.2 g) in CH2Cl2 (2 ml). The reaction mixture was stirred for 2 h at r.t. Workup and CC as described in
Exper. 7 gave (ꢀ)-21 (0.024 g) and 26a/26b (0.014 g, 35% based on converted (ꢀ)-21).
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Received July 24, 2006