photolysis of dibenzo[ a , d ]cycloheptene...

Photolysis of Dibenzo[a,d]cycloheptene Dimer

Meng-Yang Chang* and Yu-Ping HuangDepartment of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C.

(Received: Oct. 31, 2012; Accepted: Jan. 28, 2013; Published Online: ??; DOI: 10.1002/jccs.201200570)

Photolysis reaction of dibenzo[a,d]cycloheptene dimer 3 provides three dibenzo[a,d]cycloheptyl dimers4, 5 and 6 under different irradiation conditions via the intramolecular degradative cyclodimerization. Atetracyclic benzo[4,5]cyclohepta[1,2,3-de]naphthalene core is also synthesized.

Keywords: Photolysis; Dibenzo[a,d]cycloheptene; Dimer.

INTRODUCTION

In the context of the photochemical reaction of cis- or

trans-stilbene libraries, many synthetic methodologies for

the construction of strained molecules have been investi-

gated.1-2 Many organic researchers have reported that the

photochemistry of aromatic o-stilbene compounds (�-

heteroaryl 1,2-divinylbenzenes) provided some strained

photo-adducts via a series of intramolecular cycloaddition

reactions.3-4 As an extension of the studies on the skeleton

of dibenzosuberenone (1) for the synthesis of dizocilpine

(MK-801),5 we became interested in determining the pho-

tolytic cyclodimerization reaction of dibenzo[a,d]cyclo-

heptene and in the identification of the isolated products af-

ter observation under different experimental conditions

(Figure 1).

Because dibenzosuberenone (1) and its analogues are

known as the building partners in the synthesis of useful

compounds with potential applications, a number of strate-

gies have been employed for preparing the structures with

different functionalized substitutents.6 The starting mate-

rial 2a with a C-5 allyl and C-5 hydroxyl functional group

represents a cyclic cis-stilbene bearing two fused benzene

rings and is easily synthesized through Grignard allylation

of commercial grade compound 1.

As shown in Scheme I, the synthetic two-step route of

compound 3 involved: (1) Grignard allylation with allyl-

magnesium bromide and (2) cross metathesis of the corre-

sponding allyl compound 2a with the Grubbs second gen-

eration catalyst. First, compound 2a produced with a 95%

yield following a treatment of compound 1 with allylmag-

nesium bromide (1.0 M in tetrahydrofuran) for 2 h at rt.

Cross metathesis of compound 2a was treated with Grubbs

second generation catalyst to provide a sole (E)-isomer 3 in

a 70% yield. The structure of compound 3 was constructed

using single-crystal X-ray analysis (Figure 2).7 Further-

more, intramolecular photolytic degradative cyclodimeri-

J. Chin. Chem. Soc. 2013, 60, 000-000 © 2013 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1

JOURNAL OF THE CHINESE

CHEMICAL SOCIETYArticle

* Corresponding author. E-mail: [email protected]

Fig. 1. Structures of trans-Stilbene, trans-o-Vinylstil-bene and 1.

Scheme I Synthesis of dimer 3 and its photolytic reac-tion

Fig. 2. X-ray Structure of Compound 3.

zation was investigated next.

In order to contract the strained dimeric molecules,

photochemical reaction of compound 3 was examined at rt

for 2 h via different polar or nonpolar solvent (ethyl acetate

or benzene) and different wavelengths (� = 3600, 3060,

2540 Å). Under the irradation conditions, compounds 1, 4,

5, and 6 could be generated in different ratios. As shown in

Table 1, compounds 1 and 4 were isolated as major prod-

ucts and the lower yields of compounds 5~6 and the re-

corvery compound 3 in different ratios were observed.

Three strutural frameworks of the isolated products 4, 5

and 6 are constructed using single-crystal X-ray crystallog-

raphy. Single-crystal X-ray diffraction analysis was ob-

tained to prove the constitution and relative configuration

of the isolated product. These ORTEP plots clearly show

the dimeric configuration of dibenzo[a,d]cycloheptyl skel-

eton (Figures 3~5).8

When ethyl acetate was chosen as the reaction solvent

by the different irradiation wavelengths (3600 Å, 3060 Å or

2540 Å), we found that the ratios of products 1 and 3 were

stepwise decreased and the increasing yields of compounds

4~6 were observed. Under the photolytic conditions (en-

tries 1~3), we found that the yields of compound 4 were in-

creased (12% � 22% � 38%) and the yields of compound

1 were decreased (50% � 39% � 20%), respectively. For

the formation of compounds 5 and 6, only trace amounts

were generated (for 5: trace � 8% � 14%; for 6: no de-

tected � 6% � 8%). By the addition of catalytic amounts

of methylene blue (a photosensitizer), compound 4 is ob-

tained in better yield (entry 4). The product distributions

are similar between entry 3 and entry 4. Therefore, the iso-

lated photoadducts 4~7 should be predicted from the triplet

excited state during the photolytic procedure.9 Changing

the solvent from ethyl acetate to benzene (entries 5~6), we

found that the yields of compound 4 (10% � 20%) were in-

creased and the yields of compound 1 (42% � 30%) were

decreased, respectively. The yield distribution of products

4~6 were increased along with the increased energy. By the

increasing energy (3600 Å � 3060 Å), the above results re-

vealed that compound 3 could be converted completely

into these rigid products 4~6.

2 www.jccs.wiley-vch.de © 2013 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim J. Chin. Chem. Soc. 2013, 60, 000-000

Article Chang and Huang

Table 1. Photolytic reaction of compound 3a-d

Products, Yields (%)b-c

Entry SolventWavelength

(Å) 1 4 5 6 3

1 EtOAc 3600 50 12 trace -- 152 EtOAc 3060 39 22 8 6 103 EtOAc 2540 20 38 14 8 trace4d EtOAc 2540 15 45 11 10 trace5 Benzene 3600 42 10 -- -- 206 Benzene 3060 30 20 15 12 10a For the reaction condition: compound 3 (50 mg), solvent (10mL), rt, 2 h. b The recovery yield of compound 3. c The shownyields of compounds 1 and 3~6 were determined by the isolatedproducts. d Methylene blue (1 mM, 0.1 mL) was added.

Fig. 3. X-ray Structure of Compound 4.

Fig. 4. X-ray Structure of Compound 5. Fig. 5. X-ray Structure of Compound 6.

The possible mechanism is explained in Scheme II by

pathways a~g.3 Under the photochemical irradiation condi-

tions, the possible 1,2-diradicals intermediate I are pre-

ferred insofar as initiating the photolytic procedure (path-

way a).3a After the photolytic degradation of intermediate

I, two equivalents of intermediate II and butadiene should

be afforded (pathway b). Dehydrogenation of intermediate

II is further converted to compound 1 via the intermolecu-

lar [2 + 2] cycloaddition (pathways c~d).3d For minor route,

intermediate II is dimerized to form intermediate III (path-

way e). By the double dehydroxylation of intermediate III,

compound 5 is generated (pathway f).10 Then, compound 6

is obatined via the intramolecular [2 + 2] cycloaddition

(pathway g).3e Changing the solvent from ethyl acetate to

benzene, the similar phenomenon is also observed. Under

the irradiation conditions with 3600 Å and 3060 Å, the iso-

lated yields of compounds 5 and 6 were incresed to nearly

twofold in comparison with ethyl acetate. Furthermore, the

relationship between absorption wavelength and product

distribution is examined. From the UV-vis spectra, the

maximum absorption wavelength (�max) of compound 3 is

distributed with 295 nm. According to the phenomenon, we

think that UV-vis light within a range of 254~360 nm

should excite the (E)-double bond firstly. Then, the diben-

zo[a,d]cycloheptene core is likely to be the chromophore

that absorbs the UV-vis light. Therefore, the interesting ir-

radiation wavelength dependent product distribution is ob-

served.

With the above results in hand, our attention turned to

irradiate compound 2a. As shown in Table 3, major com-

pound 7 with cage skeleton was isolated in high yields

(68% for 3600 Å; 81% for 3060 Å; 70% for 2540 Å) via

intramolecular [2 + 2] cycloaddition of compound 2a using

three kinds of wavelengths (entries 1~3). Under the irradia-

tion conditions, dimer 4 or starting material 2a were iso-

lated in minor or trace amounts. By the increasing energy,

J. Chin. Chem. Soc. 2013, 60, 000-000 © 2013 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.jccs.wiley-vch.de 3


Photolysis of Dibenzo[a,d]cycloheptene Dimer CHEMICAL SOCIETY

Scheme II The possible mechanism for reaction ofcompound 1f

Table 2. Crystal data for compounds 4, 5 and 6

CCDC number 839171 (4) 839174 (5) 841658 (6)

Crystal system Monoclinic Monoclinic OrthorhombicSpace group P 1 21/c 1 P 1 21/n 1 P n m aa (Å) 10.3270(9) 10.2910(2) 8.4960(5)b (Å) 10.6469(7) 8.3098(17) 19.7509(12)c (Å) 18.8079(13) 12.3890(3) 12.0282(7)� (°) 90 90 90� (°) 99.232(5) 108.914(6) 90� (°) 90 90 90Volume (Å3)/Z 2041.2(3)/4 1002.3(4)/2 2018.4(2)/8Temperature (K) 100(2) 100(2) 296(2)Dc (Mg/m3) 1.342 1.267 1.259Absorption coefficient (mm-1) 0.083 0.072 0.071Crystal size (mm) 0.20 � 0.15 � 0.10 0.30 � 0.28 � 0.15 0.35 � 0.25 � 0.22� range for data collection (°) 2.00 to 26.45 2.24 to 26.36 1.98 to 26.36Reflections collected 15990 8234 12379Independent reflections 4188 (R = 0.0526) 2050 (R = 0.0851) 2127 (R = 0.0320)RF, Rw(F2) (all data)a 0.0733, 0.1593 0.0859, 0.1742 0.0817, 0.1874RF, Rw(F2) (I > 2(I))a 0.0454, 0.1208 0.0630, 0.1409 0.0634, 0.1727GOF 1.135 1.156 1.051a RF = |Fo-Fc|/|Fo|; RW (F2) = [W|Fo

2-Fc2|2/W Fo

4]1/2

the yield of compound 1 was decreased due to the higher

energy triggered the conversion from compound 1 to 4. In

comparison with the photolysis of compound 3 and 2a, the

only difference was the generation of cage compound 7.

For constructing compound 7, the results demonstrated that

the teminal olefinic motif was a key factor in the intra-

molecular [2 + 2] cycloaddition of compound 2a. The 1H-

NMR spectrum of compound 7 exhibited one triplet at �

4.07 for Ha proton. Both of protons of Hb and Hc appeared

as multiplets in the range of � 2.89-2.82 and � 3.73-3.68.

One CH2 protons between Hb and hydroxyl group appeared

as one doublet of doublet of doublet (� 2.13) and one dou-

blet (� 2.43). The other CH2 protons between Hb and Hc ap-

peared as one doublet (� 1.47) and one multiplet (� 2.81-

2.74). The proton of hydroxyl group showed as one singlet

at � 2.32.

When the C5-allyl group of compound 2a was re-

placed to C5-benzyl group, only product 8 was produced

with a 60% yield via photolytic dehydration of compound

2b with 3060 Å wavelength (Scheme III). Compound 2b

was yielded from Grignard benzylation of compound 1

with benzylmagnesium bromide (1.0 M in THF) with a

87% yield. Among the formed products, 12% of compound

2b was recovered and no photo-adducts were found under

this irradiative dehydration condition.

To further explore the application of polycyclic com-

pounds,11 the tetracyclic benzo[4,5]cyclohepta[1,2,3-de]-

naphthalene core 11 was chosen as a model substrate

(Scheme IV). Boron trifluoride etherate-mediated dehy-

droxylation of compound 2a with triethylsilane afforded

compound 9 with a 72% yield. After the regioselective

hydroboration of terminal olefin on the compound 9 and

Jones oxidation of the resulting alcohol, compound 10 was

synthesized in a 67% yield of two-step.12 The structural

framework of compound 10 was constructed using sin-

gle-crystal X-ray crystallography.8 Hydrogenation of com-

pound 10 with acetic acid in the presence of palladium on

carbon in acetic acid produced tetracyclic compound 11 in

a 64% yield. In particular, the skeleton of 1-tetralone was

also achieved by the palladium catalyzed intramolecular

Friedel-Crafts annulation.

In conclusion, we have successfully presented a

photolytic reaction of dimer 3 and compounds 2a~2b for

preparing dibenzosuberenone (1), three dimers 4, 5 and 6,

and cage molecules 7, and one compound 8 in ethyl acetate

or benzene at rt under three irradiation conditions (� =

3600, 3060, 2540 Å). The possible photochemical mecha-

nism was also proposed. Synthesis of tetracyclic com-

pound 11 was also achieved via a simple transformation of

compound 2a. Several structures of the products were con-

firmed by X-ray crystal analysis. Further studies on the de-

rivatives of dibenzosuberenone are actively underway in

laboratories.

EXPERIMENTAL

General. All other reagents and solvents were obtained

from commercial sources and used without further purification.

Reactions were routinely carried out under an atmosphere of dry

nitrogen with magnetic stirring. Products in organic solvents were



Table 3. Photolytic reaction of compound 2aa-c

2a

HO

Photolysis

EtOAc, rt, 2h

7

1 + +

Hc

Hb

Ha

4

Products, Yields (%)b-c

Entry SolventWavelength

(Å) 1 4 7 2a

1 EtOAc 3600 25 trace 68 trace2 EtOAc 3060 8 6 81 trace3 EtOAc 2540 trace 12 70 --a For the reaction condition: compound 2a (200 mg), EtOAc (40mL), rt, 2 h. b The recovery yield of compound 2a. c The shownyields of compounds 1, 2a, 4 and 7 were determined by theisolated products.

Scheme III Photolytic reaction of compound 2b

Scheme IV Synthesis of tetracyclic compound 11

dried with anhydrous magnesium sulfate before concentration in

vacuo. Melting points were determined with a SMP3 melting ap-

paratus. 1H and 13C NMR spectra were recorded on a Varian

INOVA-400 spectrometer operating at 400/200 and at 100/50

MHz, respectively. Chemical shifts (�) are reported in parts per

million (ppm) and the coupling constants (J) are given in Hertz.

High resolution mass spectra (HRMS) were measured with a mass

spectrometer Finnigan/Thermo Quest MAT 95XL. X-ray crystal

structures were obtained with an Enraf-Nonius FR-590 diffracto-

meter (CAD4, Kappa CCD). Elemental analyses were carried out

with Heraeus Vario III-NCSH, Heraeus CHN-OS-Rapid Ana-

lyzer or Elementar Vario EL III. UV-Visible spectra were mea-

sured with a UV/VIS/NIR spectrophotometer JASCO V-570.

Compound 3. Grubbs second catalyst (24 mg, 2.8% mmol)

was added to a stirred solution of compound 2a (75 mg, 0.3 mmol)

in 1,2-dichloroethane (8 mL) at rt. The reaction mixture was

stirred at reflux for 10 h. The reaction mixture was cooled to rt,

concentrated, and extracted with ethyl acetate (3 � 30 mL). The

combined organic layers were washed with brine, dried, filtered

and evaporated to afford crude products under reduced pressure.

Purification on silica gel (hexanes/ethyl acetate = 10/1 ~ 6/1) af-

forded compound 3 (99 mg, 70%). Colorless solid; M.p. =

195-197 oC (recrystallized from hexanes and ethyl acetate); UV

(dichloromethane) �max (log �): 295 nm (1 mg/50 mL); HRMS

(ESI, M++1) calcd for C34H29O2 469.2168, found 469.2171; 1H

NMR (400 MHz): � 7.84 (dd, J = 1.2, 8.4 Hz, 4H), 7.45 (dt, J =

2.4, 6.8 Hz, 4H), 7.35-7.28 (m, 8H), 6.93 (s, 4H), 4.79-4.76 (m,

2H), 2.53-2.51 (m, 4H), 2.30 (br s, 2H); 13C NMR (100 MHz): �

141.9 (4x), 132.3 (4x), 131.6 (4x), 130.3 (2x), 129.5 (4x), 128.7

(4x), 126.6 (4x), 124.3 (4x), 75.3 (2x), 39.0 (2x). Single-crystal

X-ray diagram: crystal of compound 3 was grown by slow diffu-

sion of ethyl acetate into a solution of compound 3 in dichloro-

methane to yield colorless prism. The compound crystallizes in

the orthorhombic crystal system, space group P c a 21, a =

21.6617(18) Å, b = 9.2296(8) Å, c = 24.861(2) Å, V = 4970.5(7)

Å3, Z = 8, Dcalcd = 1.252 g/cm3, F(000) = 1984, 2� range 1.64~

26.43o, R indices (all data) R1 = 0.1602, wR2 = 0.1696.

A representative photolysis procedure of compound 3 is as

follows (for Table 1, entry 2). Compound 3 (50 mg, 0.1 mmol)

was dissolved in ethyl acetate (10 mL) free of oxygen was irradi-

ated under a nitrogen atmosphere with a lamp (� = 3060 Å), using

a pyrex glass filter at rt for 2 h. Ten reaction vessels were col-

lected and the solvent was evaporated to afford crude product. Pu-

rification on silica gel (hexanes/ethyl acetate = 10/1~8/1~6/1~

4/1) afforded compounds 1, 4, 5 and 6. Compound 4:8a Yield =

22% (97 mg); Colorless solid; M.p. > 230 oC (recrystallized from

hexanes and ethyl acetate); UV (dichloromethane) �max (log �):

296 nm (1 mg/50 mL); HRMS (ESI, M++1) calcd for C30H21O2

413.1542, found 413.1543; 1H NMR (200 MHz): � 7.74 (dd, J =

2.0, 7.2 Hz, 4H), 7.41-7.34 (m, 8H), 7.03 (dd, J = 2.0, 6.8 Hz, 4H),

4.11 (s, 4H). Single-crystal X-ray diagram: crystal of compound 4

was grown by slow diffusion of ethyl acetate into a solution of

compound 4 in dichloromethane to yield colorless prism. The

compound crystallizes in the monoclinic crystal system, space

group P 1 21/c 1, a = 10.3270(9) Å, b = 10.6469(7) Å, c =

18.8079(13) Å, V = 2041.2(3) Å3, Z = 4, Dcalcd = 1.342 g/cm3,

F(000) = 864, 2� range 2.00~26.45o, R indices (all data) R1 =

0.0733, wR2 = 0.1593. Compound 5:8b-8d Yield = 8% (33 mg);

Colorless solid; M.p. > 230 oC (recrystallized from hexanes and

ethyl acetate); UV (dichloromethane) �max (log �): 295 nm (1

mg/50 mL); HRMS (ESI, M++1) calcd for C30H23 383.1800,

found 383.1802; 1H NMR (200 MHz): � 7.22 (dd, J = 1.6, 7.6 Hz,

4H), 7.06 (s, 4H), 7.00-6.85 (m, 8H), 6.60 (dd, J = 1.6, 7.6 Hz,

4H), 4.71 (s, 2H). Single-crystal X-ray diagram: crystal of com-

pound 5 was grown by slow diffusion of ethyl acetate into a solu-

tion of compound 5 in dichloromethane to yield colorless prism.

The compound crystallizes in the monoclinic crystal system,

space group P 1 21/n 1, a = 10.291(2) Å, b = 8.3098(17) Å, c =

12.389(3) Å, V = 1002.3(4) Å3, Z = 2, Dcalcd = 1.267 g/cm3, F(000)

= 404, 2� range 2.24~26.36o, R indices (all data) R1 = 0.0859,

wR2 = 0.1742. Compound 6:8d Yield = 6% (24 mg); Colorless

solid; M.p. > 230 oC (recrystallized from hexanes and ethyl ace-

tate); UV (dichloromethane) �max (log �): 295 nm (1 mg/50 mL);

HRMS (ESI, M++1) calcd for C30H23 383.1800, found 383.1804;1H NMR (200 MHz): � 7.06 (t, J = 4.8 Hz, 4H), 6.93-6.85 (m, 8H),

6.77 (t, J = 4.8 Hz, 4H), 4.77 (s, 2H), 4.53 (s, 4H). Single-crystal

X-ray diagram: crystal of compound 6 was grown by slow diffu-

sion of ethyl acetate into a solution of compound 6 in dichloro-

methane to yield colorless prism. The compound crystallizes in

orthorhombic crystal system, space group P n m a, a = 8.4960(5)

Å, b = 19.7509(12) Å, c = 12.0282(7) Å, V = 2018.4(2) Å3, Z = 8,

Dcalcd = 1.259 g/cm3, F(000) = 808, 2� range 1.98~26.36o, R indi-

ces (all data) R1 = 0.0817, wR2 = 0.1874.

A representative photolysis procedure of compound 2a is as

follows (for Table 3, entry 2). Compound 2a (200 mg, 0.81 mmol)

was dissolved in ethyl acetate (40 mL) free of oxygen was irradi-

ated under a nitrogen atmosphere with a lamp (� = 3060 Å), using

a pyrex glass filter at rt for 2 h. The reaction vessel was collected

and the solvent was evaporated to afford crude product. Purifica-

tion on silica gel (hexanes/ethyl acetate = 10/1~8/1~6/1~4/1) af-

forded compounds 1, 4 and 7. Compound 7: Yield = 81% (162

mg); Colorless oil; HRMS (ESI, M++1) calcd for C18H17O

249.1280, found 249.1283; 1H NMR (400 MHz): � 7.87 (dd, J =

1.2, 7.6 Hz, 1H), 7.64 (dd, J = 1.2, 7.6 Hz, 1H), 7.26-7.08 (m, 5H),




6.89 (dd, J = 1.6, 7.6 Hz, 1H), 4.07 (t, J = 7.2 Hz, 1H), 3.73-3.68

(m, 1H), 2.89-2.82 (m, 1H), 2.81-2.74 (m, 1H), 2.43 (d, J = 12.8

Hz, 1H), 2.32 (br s, 1H), 2.13 (ddd, J = 1.2, 8.8, 12.8 Hz, 1H), 1.47

(d, J = 10.8 Hz, 1H); 13C NMR (100 MHz): � 146.1, 144.0, 139.8,

134.8, 129.4, 127.3, 127.1, 127.0, 126.7, 126.1, 123.0, 120.0,

75.5, 47.0, 44.3, 41.5, 37.5, 32.2; Anal. Calcd for C18H16O: C,

87.06; H, 6.49. Found: C, 87.54; H, 6.65.

Compound 8. Compound 2b (200 mg, 0.67 mmol) was dis-

solved in ethyl acetate (40 mL) free of oxygen was irradiated un-

der a nitrogen atmosphere with a lamp (� = 3060 Å), using a pyrex

glass filter at rt for 2 h. The reaction vessel was collected and the

solvent was evaporated to afford crude product. Purification on

silica gel (hexanes/ethyl acetate = 10/1~8/1) afforded compound

8 (60%, 113 mg). Colorless solid; M.p. = 69-70 oC (recrystallized

from hexanes and ethyl acetate); HRMS (ESI, M++1) calcd for

C22H17 281.1330, found 281.1332; 1H NMR (400 MHz): � 7.57

(d, J = 7.2 Hz, 1H), 7.47-7.42 (m, 2H), 7.36-7.29 (m, 3H), 7.23-

7.11 (m, 6H), 7.02 (d, J = 12.0 Hz, 1H), 6.97 (s, 1H), 6.97-6.95

(m, 2H); 13C NMR (100 MHz): � 142.4, 142.3, 137.4, 136.9,

134.9, 134.3, 132.2, 131.4, 131.2, 129.2 (2x), 129.1, 128.9, 128.8,

128.7, 128.3, 127.8 (2x), 127.2, 127.0, 126.9, 126.7.

Compound 9. Trimethylsilane (1 mL) was added to a solu-

tion of compound 2a (200 mg, 0.81 mmol) in dichloromethane (5

mL) at rt. The reaction mixture was stirred at rt for 5 min. Boron

trifluoride etherate (BF3-OEt2, ~0.1 mL) was added to the reac-

tion mixture. The reaction mixture was stirred at rt for 3 h. Satu-

rated sodium bicarbonate solution (2 mL) was added to the reac-

tion mixture and the solvent was concentrated under reduced

pressure. The residue was extracted with ethyl acetate (3 � 30

mL). The combined organic layers were washed with brine, dried,

filtered and evaporated to afford crude product under reduced

pressure. Purification on silica gel (hexane/ethyl acetate = 6/1~

3/1) afforded compound 9 (135 mg, 72%). Colorless oil; HRMS

(ESI, M++1) calcd for C18H17 233.1330, found 233.1332; 1H

NMR (200 MHz): � 7.50-7.27 (m, 8H), 7.04 (s, 2H), 5.68-5.46

(m, 1H), 4.98-4.89 (m, 2H), 4.12 (t, J = 7.8 Hz, 1H), 2.64 (dt, J =

1.2, 7.8 Hz, 2H); 13C NMR (50 MHz): � 140.7 (2x), 136.9, 134.0

(2x), 130.9 (2x), 129.8 (2x), 129.6 (2x), 128.6 (2x), 126.3 (2x),

115.6, 55.3, 34.4.

Compound 10.12 Borane solution (2.0 mL, 1.0 M in tetra-

hydrofuran, 2.0 mmol) was added to a solution of compound 9

(120 mg, 0.52 mmol) in tetrahydrofuran (5 mL) at ice bath. The

reaction mixture was stirred at rt for 3 h. Hydrogen peroxide

(H2O2, 33%, 1.0 mL) and sodium hydroxide (NaOH, 6 M in water,

2.0 mL) were added to the reaction mixture. The reaction mixture

was stirred at rt for 3 h. Water (2 mL) was added to the reaction

mixture and the solvent was concentrated under reduced pressure.

The residue was extracted with ethyl acetate (3 � 30 mL). The

combined organic layers were washed with brine, dried, filtered

and evaporated to afford crude product under reduced pressure.

Without further purification, Jones reagent was added to the re-

sulting primary alcohol product in acetone (8 mL) at ice bath. The

reaction mixture was stirred at ice bath for 10 min. Water (2 mL)

was added to the reaction mixture and the solvent was concen-

trated under reduced pressure. The residue was extracted with

ethyl acetate (3 � 30 mL). The combined organic layers were

washed with brine, dried, filtered and evaporated to afford crude

product under reduced pressure. Purification on silica gel (hex-

ane/ethyl acetate = 1/1~1/2) afforded compound 10 (91 mg,

67%). Colorless solid; M.p. = 174-175 oC (recrystallized from

hexanes and ethyl acetate); HRMS (ESI, M++1) calcd for

C18H17O2 265.1229, found 265.1232; 1H NMR (400 MHz): �

7.40-7.24 (m, 8H), 6.91 (s, 2H), 4.01 (t, J = 7.6 Hz, 1H), 3.39 (br s,

1H), 2.11-2.01 (m, 4H); 13C NMR (100 MHz): � 179.7, 140.1

(2x), 134.0 (2x), 130.8 (2x), 129.9 (2x), 129.7 (2x), 128.8 (2x),

126.6 (2x), 54.0, 32.2, 24.8. Single-crystal X-ray diagram: crystal

of compound 10 was grown by slow diffusion of ethyl acetate into

a solution of compound 10 in dichloromethane to yield colorless

prism. The compound crystallizes in the triclinic crystal system,

space group P-1, a = 9.0372(4) Å, b = 11.3033(5) Å, c =

15.0270(6) Å, V = 1446.32(11) Å3, Z = 4, Dcalcd = 1.214 g/cm3,

F(000) = 560, 2� range 1.90~26.78o, R indices (all data) R1 =

0.0793, wR2 = 0.1473.

Compound 11. Palladium on activated carbon (10%, 15

mg) was added to a solution of compound 10 (60 mg, 0.23 mmol)

in acetic acid (10 mL) at rt. Then hydrogen was bubbled into the

mixture for 10 min, and stirring occurred at rt for 20 h. The reac-

tion mixture was filtered and evaporated to yield crude product.

Purification on silica gel (hexanes/ethyl acetate = 7/1 ~ 4/1) af-

forded compound 11 (36 mg, 64%). Colorless oil; HRMS (ESI,

M++1) calcd for C18H17O 249.1280, found 249.1287; 1H NMR

(400 MHz): � 7.94 (dd, J = 1.2, 8.0 Hz, 1H), 7.46 (dd, J = 2.4, 6.4

Hz, 1H), 7.39 (d, J = 6.4 Hz, 1H), 7.27-7.10 (m, 4H), 4.94 (t, J =

4.0 Hz, 1H), 3.59 (ddd, J = 4.4, 10.8, 15.2 Hz, 1H), 3.50 (dt, J =

5.6, 16.4 Hz, 1H), 3.12-2.91 (m, 3H), 2.87-2.74 (m, 2H), 2.59-

2.50 (m, 1H); 13C NMR (100 MHz): � 198.0, 144.7, 140.4, 138.8,

138.4, 134.1, 131.2, 130.9, 126.8, 126.8, 126.0, 125.3, 125.1,

35.5, 35.2, 33.3, 32.0, 24.9.

ACKNOWLEDGEMENTS

The authors would like to thank the National Science

Council of the Republic of China for its financial support.



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photolysis of dibenzo[ a , d ]cycloheptene...

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