1008
Chemistry Letters Vol.38, No.10 (2009)
Synthesis of 4H-Cyclopenta[def]phenanthrene from 1-Naphthylacetic Acid
Jinwoo Kim,1 Youngeup Jin,2 Suhee Song,1 Il Kim,3 and Hongsuk SuhÃ1
1Department of Chemistry and Chemistry Institute for Functional Materials,
Pusan National University, Busan 609-735, Korea
2Division of Applied Chemical Engineering, Pukyong National University, Busan 608-739, Korea
3Department of Polymer Science and Engineering, Pusan National University, Busan 609-735, Korea
(Received July 7, 2009; CL-090635; E-mail: hssuh@pusan.ac.kr)
4H-cyclopenta[def]phenanthrene (CPP) was prepared from
78% yield. The reduction of diketone 5 using sodium borohy-
dride in methanol followed by treatment with p-TsOH in toluene
provided CPP (6) in 65% yield.
In summary, this paper describes the synthesis of CPP from
commercially available 1-naphthylacetic acid.9 CPP was pre-
pared by a convenient route in six steps with an overall yield
of 36% utilizing the Michael addition and Lewis acid catalyzed
dicyclization.
1-naphthylacetic acid in six steps with an overall yield of
36%. From easily available ethyl 1-naphthaleneacetate, the
Michael addition and Lewis acid catalyzed dicyclization provid-
ed the diketone, which was reduced and dehydrated to give CPP.
Stabilized blue emission from of polymeric organic light
emitting diodes (OLED) has been a great challenge to over-
come.1,2 OLEDs with dialkyl-substituted poly(4H-cyclopenta-
[def]phenanthrene) (PCPP) have shown outstanding stability
of blue emission even after annealing or operation of the device
in air.2 The 4H-cyclopenta[def]phenanthrene (CPP), used as the
starting material for the synthesis of PCPP, was originally isolat-
ed in 1934 by Kruber3 from a refined neutral fraction of anthra-
cene oil. The exceedingly high price of CPP is possibly caused
by the very low overall yield of the known preparative meth-
od.4,5 Harvey et al.4 have prepared CPP from acenaphthene in
seven steps with an overall yield of 33%. Here, the improved
synthetic method of CPP from 1-naphthylacetic acid, which is
much cheaper than acenaphthene, by six steps with an overall
yield of 36% is reported.6
This work was supported by the Ministry of Information &
Communications, Korea, under the Information Technology Re-
search Center (ITRC) Support Program and International Coop-
eration Research Program of the Ministry of Science & Technol-
ogy, Korea (Global Research Laboratory, K20607000004-
09A0500-00410).
References and Notes
1
a) S. Y. Cho, A. C. Grimsdale, D. J. Jones, S. E. Watkins,
Huang, Y. Zhang, M. S. Liu, Y.-J. Cheng, A. K.-Y. Jen,
37, 8523. e) M. Grell, W. Knoll, D. Lupo, A. Meisel, T.
Miteva, D. Neher, H. G. Nothofer, U. Scherf, A. Yasuda,
It was envisioned to synthesize CPP from diketone 5. Re-
duction of diketone 5 with NaBH4 followed by treatment with
acid provided CPP.
As shown Scheme 1, commercially available 1-naphthylace-
tic acid (1) was protected using triethyl orthoacetate to afford
ethyl 1-naphthaleneacetate (2).7 Compound 2 was mono-alkyl-
ated using ethyl acrylate in the presence of small amounts of so-
dium ethoxide by a Michael addition to generate diethyl 2-(1-
naphthyl)pentanedioate (3) with 97% yield without any notice-
able amount of dialkylated by-product. Compound 3 was hydro-
lysed with aqueous NaOH followed by acidification with aque-
ous HCl solution to generate 2-(1-naphthyl)pentanedioic acid
(4).8 The dicarboxylic acid 4 was treated with thionyl chloride
followed by aluminum chloride for the simultaneous formation
of five- and six-membered rings to generate compound 5 in
2
a) H. Suh, Y. Jin, S. H. Park, D. Kim, J. Kim, C. Kim, J. Y.
Y. Jin, J. Y. Kim, S. H. Kim, J. Kim, H. Suh, K. Lee, Adv.
3
4
5
Contrast to the previously reported method,4,5 the simultane-
ous formation of five- and six-membered rings is essential
for the increase of the overall yield.
A typical experimental procedure is given in the Supporting
Information, available electronically on the CSJ-Journal
O
O
O
O
NaOH (aq)
THF
OH
EtO
OEt
OEt
TEOA
NaOEt, THF
tolene, 98%
Ethyl acrylate
97%
then HCl (aq)
75%
6
3
2
1
O
O
O
SOCl2
then AlCl3
HO
OH
1) NaBH4, MeOH
7
8
9
CH2Cl2, 78%
2) p-TsOH, 65%
O
5
4
6
Scheme 1. Synthesis of CPP (6) from 1.
Copyright Ó 2009 The Chemical Society of Japan