Formation of 6-methyl-7,11-diphenylheptaleno[1,2-c]furanones

Article abstract of DOI:10.1002/hlca.200900458

The dehydrogenation reaction of a mixture of heptalene-1,2- and heptalene-4,5-dimethanols 4a and 4b with basic MnO₂ in AcOEt at room temperature led to the formation of the corresponding heptaleno[1,2-c]furan-1- one 6a and heptaleno[1,2-c]furan-3-one 7a (Scheme 2). Both products can be isolated by chromatography on silica gel. The methylenation of the furan-3-one 7a with 1 mol-equiv. of Tebbe's reagent at - 25 to - 30° afforded the 2-isopropenyl-5-methylheptalene-1-methanol 9a, instead of the expected 3,6-dimethylheptaleno[1,2-c]furan 8 (Scheme 3). Also, the treatment of 7a with Takai's reagent did not lead to the formation of 8. On standing in solution at room temperature, or more rapidly on heating at 60°, heptalene 9a undergoes a reversible double-bond shift (DBS) to 9b with an equilibrium ratio of 1:1.

Full text of DOI:10.1002/hlca.200900458

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Formation of 6-Methyl-7,11-diphenylheptaleno[1,2-c]furanones
by Xudong Jina)b), Anthony Lindenb), and Hans-Jꢀrgen Hansen*b)
a) College of Chemistry, Liaoning University, Shenyang 110036, P. R. China
b) Organisch-chemisches Institut der Universitꢀt Zꢁrich, Winterthurerstr. 190, CH-8057 Zꢁrich
(phone: þ 41-44-6354231; fax: þ 41-44-6359812; e-mail: H.-J.H@access.uzh.ch)
The dehydrogenation reaction of a mixture of heptalene-1,2- and heptalene-4,5-dimethanols 4a and
4b with basic MnO2 in AcOEt at room temperature led to the formation of the corresponding
heptaleno[1,2-c]furan-1-one 6a and heptaleno[1,2-c]furan-3-one 7a (Scheme 2). Both products can be
isolated by chromatography on silica gel. The methylenation of the furan-3-one 7a with 1 mol-equiv. of
Tebbeꢂs reagent at ꢀ 25 to ꢀ 308 afforded the 2-isopropenyl-5-methylheptalene-1-methanol 9a, instead
of the expected 3,6-dimethylheptaleno[1,2-c]furan 8 (Scheme 3). Also, the treatment of 7a with Takaiꢂs
reagent did not lead to the formation of 8. On standing in solution at room temperature, or more rapidly
on heating at 608, heptalene 9a undergoes a reversible double-bond shift (DBS) to 9b with an equilibrium
ratio of 1:1.
Introduction. – Several years ago, we reported on the dehydrogenation reaction of
heptalene-1,2- and heptalene-4,5-dimethanols, which can easily be obtained by LiAlH4
or DIBAH (diisobutylaluminium hydride) reduction of the corresponding heptalene-
dicarboxylates. Treatment of the heptalenedimethanols with activated MnO2 in CH2Cl2
led to the formation of the corresponding heptaleno[1,2-c]furans and heptaleno[1,2-
c]furan-3-ones 1 and 1’ (cf. [1] and lit. cit. therein). We further studied the synthesis of
3-methyl-substituted heptaleno[1,2-c]furans 3 and 3’ by the reaction of the correspond-
ing furan-3-ones with 1 mol-equiv. of Tebbeꢂs reagent (¼ m-chlorobis(h5-cyclopenta-2,4-
dien-1-yl)(dimethylaluminium)-m-methylenetitanium) in toluene, respectively
(Scheme 1). We assumed that, in the first step, the methylene forms 2 and 2’ are
formed, and then isomerize under base catalysis to the final products.
Scheme 1
a) 1 Mol-equiv. of Tebbeꢂs reagent (Aldrich), 0.5m in toluene [1].
ꢃ 2010 Verlag Helvetica Chimica Acta AG, Zꢁrich

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Results. – The starting mixture of the heptalene-1,2- and -4,5-dimethanols 4a and
4b, respectively, for this study was obtained by DIBAH reduction of the corresponding
heptalene-4,5-dicarboxylate in excellent yield [2]. The thermal equilibrium mixture of
4a and its DBS isomer 4b was vigorously stirred in AcOEt at room temperature in the
presence of a 20 – 25-fold amount by weight of MnO2 for 30 – 40 min. After removal
and extraction of MnO2 with AcOEt, the product mixture was separated by
chromatography (silica gel) leading to heptaleno[1,2-c]furan-1-one 6a and heptale-
no[1,2-c]furan-3-one 7a (Scheme 2).
Scheme 2
a) Thermal 1:2 equilibrium mixture of 4a and its double-bond-shift (DBS) isomer 4b. b) n.d. ¼ not
detectable. c) At room temperature, 7a is in thermal equilibrium with 6% of its DBS isomer 7b (CDCl3).
In this reaction, heptaleno[1,2-c]furan 5 was not found and, instead, the yield of 7a
was up to 87%. Its isomer 6a was formed in only 7% yield, due to the sterically hindered
position of the methanol function at C(5). It is of interest to note that both furanones
show quite different UV/VIS spectra in hexane (Fig. 1,a and b). The furan-3-one 7a
displays a clear maximum at 292 nm, whereas the spectrum of the isomeric furan-1-one
6a possesses only a weak shoulder. On the other hand, the heptalene bands in the long-
wavelength region are comparable. Both show a very broad flat maximum at ca.
400 nm, which can be attributed to heptalene-band I (see [3] for band assignment). We
suppose that the absorption at 292 nm reflects slight differences in the conjugation of
the furanone C¼O groups with the heptalene chromophore of 6a and 7a, which can be
attributed to small deviations in the torsion angles of the heptalene perimeter. Indeed,
AM1 calculations (CS Chem3D Proꢄ, 2001) of both structures indicate slightly smaller
cisoid torsion angles at the central heptalene axis (C(6a)ꢀC(11a)) for 7a in comparison
with 6a (see also [1])1).
The structure of 6a and 7a could be unequivocally deduced from their NMR
spectra. Both compounds exhibit for HꢀC(4) and HꢀC(5) an AB signal pattern with
3JAB ¼ 11.3 and 11.5 Hz for 6a and 7a, respectively. Whereas the methylene H-atoms of
7a display in CDCl3 the expected AB signal pattern at d 4.16 and 3.91, respectively, with
2JAB ¼ 17.8 Hz, they appear for 6a as a more deshielded s at d 4.81 (cf. [1]). Moreover, in
the 1H-NMR spectrum of 7a, weak signals of its double-bond-shifted (DBS) isomer 7b
1
)
Another explanation would be that the clearly defined 292 nm band of heptaleno[1,2-c]furan-3-one
7a reflects a residual conjugation within the partial structure PhꢀC(11)¼C(11a)ꢀC(11b)¼
C(3a)ꢀC(3)¼O, which is not present in the furan-1-one 6a. However, the AM1 calculations show
for both structures an almost perpendicular PhꢀC(11) group with respect to the C(11)¼C(11a)
bond.

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Fig. 1. UV/VIS Spectra (hexane) of a) 6a and b) 7a
could be identified with an AB signal pattern for CH2(1) at d 4.39 and 3.94, respectively,
2
with JAB ¼ 13.3 Hz. The reduced 2J value of 7b indicates the interrupted hyper-
conjugation between CH2(1) and C(3)¼O (cf. [1]). The DBS isomer of 6a, i.e., 6b, was
not found in solutions of 6a (C6D6 or CDCl3) at room temperature.
When furanone 7a was treated in the established way with Tebbeꢂs reagent in
toluene at ꢀ 25 to ꢀ 308 [1] (see also [4][5]), a single product was formed. However,
instead of the expected 3,6-dimethylheptaleno[1,2-c]furan 8, the ring-opened 2-
isopropenyl-5-methylheptalene-1-methanol 9a was isolated (Scheme 3). On standing
in solution (CDCl3 or C6D6), 9a was converted slowly into its DBS isomer 9b. The
equilibrium mixture 9a/9b in C6D6 was rapidly established on heating at 608, leading to

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937
a 1:1 ratio of 9a/9b (see below). The structures of 9a and 9b were unambiguously
confirmed by their 1H-NMR spectra in CDCl3 and C6D6, respectively. In particular, the
3J value of HꢀC(3) and HꢀC(4) of 9a (C6D6) changed from 11.8 Hz to 6.1 Hz for the
equivalent H-atoms HꢀC(2) and HꢀC(3) of 9b. Moreover, the qualitative UV/VIS
spectra of 9a and 9b in hexane are quite interesting (Fig. 2,a and b). Both isomers show
the typical long-wavelength heptalene-band I as a broad shoulder at ca. 368 nm with a
slightly stronger intensity in the case of 9b, where the CH2¼C(Me) group is in
conjugation with the heptalene fragment MeꢀC(1)¼C(2)ꢀC(3)¼C(4). On the other
hand, heptalene 9a displays a much more pronounced absorption band at 286 nm in
comparison with that of 9b, which appears at the same wavelength (cf. Fig. 2,a and b).
We believe that this effect is again attributable to the slightly smaller cisoid torsion
angles at the central s-bond of the heptalene core of 9a leading to a better conjugative
interaction with the isopropenyl group, as we have already discussed in the case of 7a
(see Fig. 1,b, and below).
Scheme 3
a) 1 Mol-equiv. of Tebbeꢂs reagent (Fluka), 0.5m in toluene, at ꢀ 25 to ꢀ 308, followed by basic workup
at r.t. b) On heating at 608 in C6D6, 9a formed a 1:1 equilibrium mixture with its DBS isomer 9b.
The structure of 9a was further elucidated by an X-ray crystal-structure analysis
(Fig. 3). Unfortunately, heptalene 9a crystallized from hexane/Et2O as thin plates
which showed only very weak diffraction. The poor quality of the available data
allowed only the confirmation of the backbone structure of 9a. Nevertheless, two
independent molecules could be identified in the asymmetric unit, which seemed to
differ only with respect to the conformation of the primary-alcohol group, relative to
the backbone structure (for the X-ray structure, see Sect. 3 in the Exper. Part).
We therefore performed AM1 calculations of 9a as well as of 9b. There exist indeed
for the two DBS isomers low-energy conformations A and B with almost the same
DHf 8 values (Figs. 4 and 5). In conformations A, the H-atom of the OH group of the
primary-alcohol function at C(1) and C(5), respectively, is located close to

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Helvetica Chimica Acta – Vol. 93 (2010)
Fig. 2. UV/VIS Spectra (hexane) of a) 9a and b) 9b
C(10),C(10a) and C(5a),C(6), respectively. In the B conformations, the H-atom of the
OH group is pointing toward the C¼C bond of the isopropenyl group2).
2
)
There are a number of further conformations of 9a and 9b of similar energy and with the OꢀH
bond above the heptalene core or close to the C¼C bond of the isopropenyl group. The two of 9a
shown in Fig. 4 reflect at best the backbone structure of molecules A and B found in the asymmetric
unit of 9a.

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Fig. 3. Stereoscopic view of the X-ray crystal structure of 2-isopropenyl-5-methyl-6,10-diphenylheptalene-
1-methanol (9a)
Fig. 4. Stereoscopic view of the AM1-calculated structure of 9a with the OꢀH bond oriented a) toward the
heptalene core and b) toward the isopropenyl group

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Fig. 5. Stereoscopic view of the AM1-calculated structure of 9b with the OꢀH bond oriented a) toward the
heptalene core and b) the isopropenyl group
In agreement with the calculated structures for 9a and 9b is the fact that both form
an 1:1 equilibrium mixture at 608 and both exhibit chemical shifts of the H-atom of the
OH group of 9a and 9b, which appear in CDCl3 as well as C6D6 around d 1.0 (cf. Exper.
Part), speaking for intramolecular shielding of the hydroxy H-atom by the surrounding
p-systems. Moreover, the above-mentioned cisoid torsion angles at the central s-bond
are slightly larger for 9a than for 9b, which explains the stronger conjugation of the
isopropenyl group with the heptalene core of 9b in comparison with 9a.
Regarding the formation of 9a from furanone 7a and Tebbeꢂs reagent (Scheme 3), it
is of interest to note that a Me group must have been transferred from the reagent to
the C¼O group of the fused lactone, followed, after ring opening, by normal
methylenation of the formed MeCO group (Scheme 4).
Later on, we also tested the reaction of furan-3-one 7a with 1 mol-equiv. of Takaiꢂs
reagent [6] (see Exper. Part), which did not lead to the desired 3-methylheptaleno[1,2-
c]furan 8 either (Scheme 5).
We thank our MS department for mass spectra and our NMR department for NMR support and 2D-
NMR measurements. The financial support of this work by the Swiss National Science Foundation is
gratefully acknowledged.

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Scheme 4
Scheme 5
a) 1 Mol-equiv. of Takaiꢂs reagent in 0.5m solution in toluene, r.t., followed by basic workup [6].
Experimental Part
1. General. See [1][2]. Compound 4 was available from our previous work [2].
2. Heptaleno[1,2-c]furans and Heptaleno[1,2-c]furanones. 2.1. 6-Methyl-7,11-diphenyl-heptaleno[1,2-
c]furan-1(3H)-one (6a) and 6-Methyl-7,11-diphenyl-heptaleno[1,2-c]furan-3(1H)-one (7a). The basic
MnO2 was prepared according to [7]. The thermal 1:2 equilibrium mixture of 4a and its DBS isomer 4b
(56 mg, 0.147 mmol) was dissolved in AcOEt (100 ml), and a 20 – 25-fold amount by weight of MnO2 was
added within 30 – 40 min. After the addition, the mixture was stirred vigorously during 30 min at r.t.
(TLC: no dimethanols left). The MnO2 was filtered off over Celite and washed with AcOEt. To the
filtrate was added TsOH (15 mg), and stirring was continued overnight. The soln. was washed with a sat.
aq. NaHCO3 soln. and dried (MgSO4). CC (silica gel, hexane/Et2O 1:1) gave two yellow products, 6a
(4 mg, 7%) and 7a (48 mg, 87%). The products were recrystallized from hexane/Et2O 1:1 and acetone,
resp.
Data of 6a: M.p. 197 – 1988 (hexane/Et2O). Rf (hexane/Et2O 1:1) 0.16. UV/VIS (hexane; Fig. 1,a):
max. 231 (sh, 1.00), 260 (0.86); min. 249 (0.84), 289 (sh, 0.64). IR (KBr): 3438w, 3054w, 3018m, 2923m,
2853m, 1757s, 1684m, 1595m, 1491m, 1443m, 1335m, 1243w, 1153m, 1108m, 1076m, 1036m, 901w, 839w,
803w, 761m, 720m, 699s, 533w, 494w. 1H-NMR (600 MHz, CDCl3): 7.30 (d with f.s., 3J ¼ 7.2, 2 arom. H);
7.18 – 7.14 (m, 5 arom. H); 7.11 (t-like, 3J ¼ 7.2, 7.4, 1 arom. H); 6.99 (2d, 3J ¼ 7.2, 8.0, 2 arom. H); 6.81 (d,
3J(5,4) ¼ 11.3, HꢀC(5)); 6.80 (d, 3J(8,9) ¼ 6.2, HꢀC(8)); 6.63 (dd, 3J(9,10) ¼ 11.4, 3J(9,8) ¼ 6.3,
3
3
HꢀC(9)); 6.49 (d, J(4,5) ¼ 11.3, HꢀC(4)); 6.46 (d, J(10,9) ¼ 11.4, HꢀC(10)); 4.81 (s, CH2(3)); 1.44
.
(s, MeꢀC(6)). EI-MS (GC): 377, 376, and 375 (9, 31, and 12, Mþ ), 281 (11), 274 (35), 239 (10), 209 (14),
208 (20), 207 (100), 198 (33), 191 (13), 151 (38), 150 (20), 138 (12), 105 (17), 96 (32), 91 (15), 73(22).
Data of 7a: M.p. 157 – 1588 (acetone). Rf (hexane/Et2O 1:1) 0.37. UV/VIS (hexane, c ¼ 0.361 ·
10ꢀ4 m; Fig. 1,b): max. 234 (0.91), 292 (0.88); min. 223 (0.87), 263 (0.63), 310 (sh, 0.53). IR (KBr):
3486w, 3018w, 2914w, 2861w, 1752s, 1640w, 1596w, 1490m, 1442m, 1374w, 1330m, 1284w, 1270w, 1240w,
1189w, 1144w, 1101w, 1074w, 1048m, 1029s, 1003m, 924w, 876w, 814w, 790m, 769m, 753w, 738m, 721m,

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1
703m, 675w, 633w, 616w, 567w, 538w, 503w, 473w. H-NMR (600 MHz, CDCl3; in thermal equilibrium
3
3
with 6% of 7b): 7.30 (d with f.s., J ¼ 7.2, 2 arom. H); 7.23 – 7.19 (m, 5 arom. H); 7.16 (t-like, J ¼ 7.2, 1
3
5
3
arom. H); 6.97 – 6.96 (m, 2 arom. H); 6.86 (d, J(8,9) ¼ 6.2, HꢀC(8)); 6.75 (dd, J ¼ 0.7, J(4,5) ¼ 11.3,
HꢀC(4)); 6.88 (dd, 3J(9,10) ¼ 11.5, 3J(9,8) ¼ 6.2, HꢀC(9)); 6.69 (d, 3J(5,4) ¼ 11.5, HꢀC(5)); 6.42 (d,
3J(10,9) ¼ 11.5, HꢀC(10)); 4.16 (d, A of AB, 2JAB ¼ 17.8, 1 H, CH2(1)); 3.91 (d with f.s., B of AB, 2JAB
¼
17.8, 1 H, CH2(1)); 1.44 (s, MeꢀC(6)). 13C-NMR (125 MHz, CDCl3): 171.81 (s); 153.50 (s); 139.22 (d);
139.31 (s); 139.20 (s); 138.82 (s); 137.76 (s); 135.78 (s); 134.05 (d); 133.52 (d); 130.26 (s); 129.51 (s);
129.31 (d, 2 arom. C); 129.27 (d, 2 arom. C); 128.90 (d, 2 arom. C); 128.62 (d); 127.98 (d); 127.31 (d);
126.17 (d, 2 arom. C); 125.20 (s); 122.22 (s); 68.69 (t); 19.36 (q). EI-MS (GC): 377, 376, and 375 (17, 57,
.
and 13, Mþ ), 361 (52), 317 (18), 303 (20), 302 (29), 289 (16), 275 (19), 274 (88), 246 (9), 245 (41), 239
(26), 215 (32), 207 (59), 202 (68), 198 (88), 158 (21), 157 (38), 151 (100), 145 (60), 138 (36), 132 (22), 91
(25), 77(14).
1
Data of 6-Methyl-7,11-diphenylheptaleno[4,5-c]furan-3(1H)-one (7b): H-NMR (600 MHz, CDCl3;
6% 7b in the thermal equilibrium mixture with 7a): identified signals: 6.82 (d, 3J(10,9) ¼ 6.5, HꢀC(10));
6.51 (dd, 3J(9,8) ¼ 11.6, 3J(9,10) ¼ 6.5, HꢀC(9)); 6.45 (dq-like, 3J(5,4) ¼ 6.8, 4J(5,MeꢀC(6)) ¼ 1.4,
HꢀC(5)); 6.42 (d, 3J(8,9) ¼ 11.6, HꢀC(8)); 4.39 (d, A of AB, 2JAB ¼ 13.3, 1 H, CH2(1)); 3.94 (d, B of AB,
2JAB ¼ 13.3, 1 H, CH2(1)); 1.70 (d-like, 4J(MeꢀC(6),5) ꢁ 1.3, MeꢀC(6)).
2.2. Methylenation of Heptaleno[1,2-c]furan-3-one 7a with Tebbeꢀs Reagent. Furanone 7a (25 mg,
0.066 mmol) was dissolved in dry THF (10 ml) and treated with Tebbeꢂs reagent (Flukaꢄ; 0.2 ml of a 0.5m
soln. in toluene) as described in Exper. 3.1 of [1]. Purification by CC (silica gel, hexane/Et2O 4 :1) gave
pure 9a (15 mg, 58%). When its solution was exposed to daylight for 2 days, the 1H-NMR showed,
besides 9a, the presence of 9b (cf. Scheme 3). The molar ratio 9a/9b was 61:39 in C6D6 and 71:29 in
CDCl3. The equilibrium mixture 9a/9b in C6D6 was rapidly established on heating at 608 for 10 h, leading
to a 1:1 ratio of 9a/9b. Both isomers were isolated by CC (silica gel, hexane/Et2O 4 :1).
Data of 5-Methyl-2-(1-methylethenyl)-6,10-diphenylheptalene-1-methanol (9a): Yellow crystals. M.p.
112 – 1138 (hexane/Et2O). Rf (hexane/Et2O 4 :1) 0.18. UV/VIS (hexane; Fig. 2,a): max. 231 (1.05), 286
(0.95); min. 221 (0.98), 258 (0.65). 1H-NMR (600 MHz, C6D6; present with 39% of 9b): 7.65 (d with f.s.,
Jo ¼ 8.4, Ho of PhꢀC(6)); 7.28 (d with f.s., Jo ¼ 8.4, Ho of PhꢀC(10)); 7.15 – 7.03 (arom. H); 7.01 (tt, Jo ¼ 7.4,
3
3
Jm ¼ 1.0, Hp of PhꢀC(10)); 6.82 (d, J(7,8) ¼ 6.1, HꢀC(7)); 6.56 (d, J(9,8) ¼ 11.4, HꢀC(9)); 6.51 (dd,
3J(8,9) ¼ 11.5, 3J(8,7) ¼ 6.2, HꢀC(8)); 6.47 (br. d, 3J(3,4) ¼ 11.8, HꢀC(3)); 6.37 (d, 3J(4,3) ¼ 11.7,
HꢀC(4)); 4.94 (t-like, J ¼ 1.8, Htrans of CH2¼C(Me)ꢀC(2)); 4.86 (t-like, 5J ¼ 1.0, Hcis of
2
3
CH2¼C(Me)ꢀC(2)); 4.16 (dd, A of ABX, JAB ¼ 12.8, JAX ¼ 5.5, 1 H, HOCH2ꢀC(1)); 3.57 (dd, B of
ABX, 2JAB ¼ 12.8, 3JBX ¼ 2.6, 1 H, HOCH2ꢀC(1)); 1.82 (s, CH2¼C(Me)ꢀC(2)); 1.52 (s, MeꢀC(5)); 1.03
1
(t-like, partially covered, J ꢁ 5.8, HOCH2ꢀC(1)). H-NMR (600 MHz, CDCl3; present with 29% of its
DBS isomer 9b): 7.47 (d with f.s., Jo ¼ 7.4, Ho of PhꢀC(6)); 7.21 (t-like, partially covered, Hm of PhꢀC(6));
7.20 – 7.15 (arom. H); 7.11 (d, superimposed by d of 9b, Ho of PhꢀC(10)); 6.94 (d, 3J(7,8) ¼ 6.3, HꢀC(7));
3
3
3
3
6.63 (dd, J(8,9) ¼ 11.6, J(8,7) ¼ 6.4, HꢀC(8)); 6.47 (d, J(9,8) ¼ 11.4, HꢀC(9)); 6.46 (s, J(3,4) ꢁ 12,
HꢀC(3,4)); 5.00 (t-like, J ¼ 1.6, Htrans of CH2¼C(Me)ꢀC(2)); 4.67 (d-like, J ¼ 0.9, Hcis of
2
2
CH2¼C(Me)ꢀC(2)); 3.93 (dd, A of ABX, JAB ¼ 12.7, JAX ¼ 6.3, 1 H, HOCH2ꢀC(1)); 3.33 (dd, B of
ABX, 2JAB ¼ 12.9, 2JBX ¼ 4.0, 1 H, HOCH2ꢀC(1)); 1.86 (s, CH2¼C(Me)ꢀC(2)); 1.45 (s, MeꢀC(5)); 0.96
(br. t, J ꢁ 6, HOCH2ꢀC(1)). 13C-NMR (125 MHz, C6D6; present with 76% of its DBS isomer 9b): not
assigned signals: 134.52 (d); 132.86 (d); 131.21 (d); 130.27, 128.91, 127.51, 127.25, 125.78 (5 ꢂ 2 C);
assigned signals: 145.19 (s, C(1)); 143.35 (s, C(2)); 140.66 (s, 1 arom. C); 139.80 (s, 1 arom. C); 136.75 (s,
C(6)); 136.37 (s, C(10)); 133.51 (s, CH2¼C(Me)ꢀC(2)); 132.10 (s, C(5a)); 131.68 (s, C(5)); 115.14 (t,
CH2¼C(Me)ꢀC(2)); 60.36 (t, HOCH2ꢀC(1)); 23.60 (q, CH2¼C(Me)ꢀC(2)); 22.23 (q, MeꢀC(5)). EI-
.
MS (GC): 391 and 390 (24 and 75, Mþ ), 375 (20, [M ꢀ Me]þ), 331 (19), 317 (27), 289 (16), 273 (69), 252
(18), 239 (40), 215 (34), 212 (47), 202 (17), 197 (100), 165 (21), 164 (29), 163 (46), 151 (53), 145 (30), 138
(22), 115 (20), 92 (30), 91 (92), 77 (19), 57 (21).
Data of 1-Methyl-4-(1-methylethenyl)-6,10-diphenylheptalene-5-methanol (9b): Yellow oil. Rf
(hexane/Et2O 4 :1) 0.10. UV/VIS (hexane; Fig. 2,b): max. 229 (1.09), 286 (0.89); min. 221 (1.06), 266
(0.80). 1H-NMR (600 MHz, C6D6; present with 61% of its DBS isomer 9a): 7.60 (d with f.s., Jo ¼ 8.4, Jm ¼
1.3, Ho of PhꢀC(6)); 7.33 (d with f.s., Jo ¼ 8.2, Jm ¼ 1.3, Ho of PhꢀC(10)); 7.15 – 7.03 (arom. H); 6.97 (tt,
Jo ¼ 7.3, Jm ¼ 1.5, Hp of PhꢀC(6)); 6.71 (d, 3J(7,8) ¼ 6.0, HꢀC(7)); 6.67 (dq-like, 3J(3,2) ¼ 6.1,

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3
3
3
5J(3,MeꢀC(1)) ¼ 0.7, HꢀC(3)); 6.58 (d, J(9,8) ¼ 11.4, HꢀC(9)); 6.51 (dd, J(8,9) ¼ 11.5, J(8,7) ¼ 6.3,
HꢀC(8)); 6.08 (dq-like, 3J(2,3) ¼ 6.1, 4J(2,MeꢀC(1)) ¼ 1.4, HꢀC(2)); 5.10 (d-like, J ¼ 1.5, Hcis of
CH2¼C(Me)ꢀC(4)); 4.94 (t-like, J ¼ 1.8, Htrans of CH2¼C(Me)ꢀC(4)); 4.28 (dd, A of ABX, 2JAB ¼ 12.4,
3JAX ¼ 4.2, 1 H, HOCH2ꢀC(5)); 4.24 (dd, B of ABX, 2JAB ¼12.4, 3JBX ¼ 5.0, 1 H, HOCH2ꢀC(5)); 1.92 (s,
CH2¼C(Me)ꢀC(4)); 1.55 (s, MeꢀC(1)); 1.02 (t-like, partially covered, J ꢁ 6, HOCH2ꢀC(5)). 1H-NMR
(600 MHz, CDCl3, present with 71% of its DBS isomer 9a): 7.52 (d with f.s., Jo ¼ 7.4, Ho of PhꢀC(6)); 7.23
(t-like, Jo ¼ 7.4, 7.9, Hm of PhꢀC(6)); 7.20 – 7.15 (arom. H); 7.13 (d, superimposed by d of 9a, Ho of
PhꢀC(10)); 6.85 (d, 3J(9,8) ¼ 6.1, HꢀC(9)); 6.64 (dd, 3J(8,7) ¼ 11.2, 3J(8,9) ¼ 6.2, HꢀC(8)); 6.61 (br. d,
partially covered, 3J(3,4) ꢁ 6, HꢀC(3)); 6.48 (d, 3J(7,8) ¼ 11.4, HꢀC(7)); 6.20 (dq-like, 3J(2,3) ¼ 6.0,
4J(2,MeꢀC(1)) ¼ 1.3, HꢀC(2)); 4.96 (qunit.-like, J ¼ 1.5, Htrans of CH2¼C(Me)ꢀC(4)); 4.91 (br. d-like,
3
J ¼ 1.7, Hcis of CH2¼C(Me)ꢀC(4)); 3.97, 3.94 (AB of ABX, 2JAB ¼ 12.2, 3JAX ꢁ JBX ¼ 5, HOCH2ꢀC(5));
1.88 (s, CH2¼C(Me)ꢀC(4)); 1.49 (s, MeꢀC(1)); 0.91 (br. t-like, J ꢁ 6.7, HOCH2ꢀC(5)). 13C-NMR
(125 MHz, C6D6; present with 24% of its DBS isomer 9a): 147.94 (s, C(4)); 146.44 (s, C(5)); 140.42 (s, 1
arom. C); 139.54 (s, 1 arom. C); 137.61 (s, C(1)); 136.26 (s, C(10)); 134.95 (s, CH2¼C(Me)ꢀC(4)); 134.45
(d, C(9)); 134.29 (s, C(6)); 134.18 (s, C(10a)); 132.75 (s, C(5a)); 131.47 (d, C(8)); 129.89 (d, 2 arom. C);
129.42 (d, C(3)); 129.17 (d, 2 arom. C); 129.02 (d, C(2)); 128.33 (d, 2 arom. C); 127.95 (d, 1 arom. C);
127.76 (d, 1 arom. C); 126.47 (d, 2 arom. C); 125.71 (d, C(7)); 114.83 (t, CH2¼C(Me)ꢀC(4)); 60.32 (t,
HOCH2ꢀC(5)); 23.42 (q, CH2¼C(Me)ꢀC(4)); 22.23 (q, MeꢀC(1)). EI-MS (GC): 391 and 390 (5 and
.
16, Mþ ), 373 (17), 372 (53), 357 (22), 313 (10), 295 (11), 279 (19), 270 (45), 256 (40), 239 (41), 215 (14),
202 (13), 194 (100), 179 (35), 164 (40), 163 (65), 157 (39), 151 (36), 138 (28), 132 (18), 92 (29), 91 (78),
84 (47), 77 (12), 57 (18).
2.3. Methylenation of Heptaleno[1,2-c]furan-3-one 7a with Takaiꢀs Reagent. The Takaiꢂs reagent was
prepared as described in [6]. A soln. of TiCl4 (1.0m, 0.4 mmol) in CH2Cl2 was diluted with THF (10 ml) at
08, then N,N,N’,N’-tetramethylethylenediamine (¼ N1,N1,N2,N2-tetramethylethane-1,2-diamine; TME-
DA; 0.12 ml, 0.8 mol) and zinc dust (59 mg, 0.9 mmol) were added. After 30 min stirring at 258, a soln. of
furanone 7a (37.6 mg, 0.1 mmol) and CH2Br2 (54 mg, 0.22 mmol) in THF (1 ml) were added. After 3 h,
the reaction was quenched with 2m NaOH, the mixture filtered over Celite, and the filtrate dried
(MgSO4). The solvent was distilled off and the residue subjected to CC (silica gel, hexane/Et2O 1:1). The
results indicated that compound 8 was not formed.
3. X-Ray Crystal-Structure Determination of Compound 9a (cf. Table and Fig. 3)3). All measure-
ments were made with a Nonius-KappaCCD area-detector diffractometer [8], graphite-monochromated
MoKa radiation (l 0.71073 ꢅ), and an Oxford-Cryosystems-Cryostream-700 cooler. The data collection
and refinement parameters are given in the Table. Data reduction was performed with HKL DENZO
and SCALEPACK [9]. The intensities were corrected for Lorentz and polarization effects but not for
absorption. The structure was solved by direct methods with SHELXS97 [10], which revealed the
positions of all non-H-atoms. There are two symmetry-independent molecules in the asymmetric unit.
The atomic coordinates of the two molecules were tested carefully for a relationship from a higher-
symmetry space group with the program PLATON [11], but none could be found. The non-H-atoms were
refined anisotropically. All of the H-atoms were placed in geometrically calculated positions and refined
with a riding model where each H-atom was assigned a fixed isotropic displacement parameter with a
value equal to 1.2 Ueq of its parent atom (1.5 Ueq for the Me groups). Refinement of the structure was
carried out on F2 by full-matrix least-squares procedures, which minimized the function Sw(j Fo jꢀj Fc j )2.
A correction for secondary extinction was not applied. One reflection, whose intensity was considered to
be an extreme outlier, was omitted from the final refinement.
Neutral-atom scattering factors for non-H-atoms were taken from [12a], and the scattering factors
for H-atoms were taken from [13]. Anomalous dispersion effects were included in Fc [14]; the values for
f ’and f ’’ were those of [12b]. The values of the mass attenuation coefficients are those of [12c]. All
calculations were performed with SHELXL97 [15].
3
)
CCDC-758044 contains the supplementary crystallographic data for this work. These data can be
obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.

944
Helvetica Chimica Acta – Vol. 93 (2010)
Table. Crystallographic Data of 9a
Crystallized from
Empirical formula
Mr
Crystal color, habit
Crystal dimensions [mm]
Temperature [K]
Crystal system
Space group
hexane/Et2O
C29H26O
390.52
F(000)
832
Dx [g cmꢀ3
]
1.179
0.0694
w
m(MoKa) [mmꢀ1
]
Scan type
yellow, plate
0.02 ꢂ 0.12 ꢂ 0.30 2q (max) [8]
50
26048
160(1)
Total reflections measured
Symmetry-independent reflections 4171
Rint
Reflections with I > 2s (I)
Reflections used in refinement
Parameters refined; restraints
Final R(F) (I > 2s(I) reflections) 0.0788
wR(F2) (all data)
Weights
Goodness of fit
Final Dmax/s
D1 (max; min) [e ꢅꢀ 3
s (d (CꢀC)) [ꢅ]
monoclinic
P21
4
0.134
2711
4170
Z
Reflections for cell determination 4136
2q Range for cell determination [8] 4 – 50
Unit cell parameters:
a [ꢅ]
b [ꢅ]
c [ꢅ]
a [8]
b [8]
g [8]
V [ꢅ3]
545; 1
13.471(1)
0.1758
a
8.1778(7)
20.812(2)
90
106.278(6)
90
)
1.129
0.001
0.27; – 0.21
0.008 – 0.01
]
2200.8(3)
a) w ¼ [s2 (Fo)2 þ (0.0491 P)2 þ 0.5479 P]ꢀ1, where P ¼ (Fo2 þ 2 F2c )/3.
The diffraction data of 9a are poor due to very weak diffraction of the available thin-plate crystals
and do not allow the structure to be confirmed unambiguously. There are two independent molecules in
the asymmetric unit. Molecule A looks to have the expected structure, but molecule B leaves some doubt
about the nature of the hydroxymethyl substituent, because the displacement parameters for the hydroxy
O-atom are too large, but a disordered model cannot be refined successfully either, leaving doubt about
whether the hydroxy O-atom is really an O-atom. The space group permits the compound in the crystal to
be enantiomerically pure, but the absolute configuration of the molecules was assigned arbitrarily. The
two independent molecules have the same axial chirality. The two independent molecules have similar
conformations, except for the 1-methylethenyl substituents which differ by a small twist of ca. 338 about
the C(2)ꢀC(1’’) bond.
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Helvetica Chimica Acta – Vol. 93 (2010)
945
[12] a) E. N. Maslen, A. G. Fox, M. A. OꢂKeefe, in ꢆInternational Tables for Crystallographyꢂ, Ed. A. J. C.
Wilson, Kluwer Academic Publishers, Dordrecht, 1992, Vol. C, Table 6.1.1.1, pp. 477 – 486; b) D. C.
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Received December 18, 2009