Journal of Photochemistry and Photobiology A:
Chemistry
Short note
1-phenyl-2-(pyridyl)acetylenes in acidic aqueous solution
Junpeng Zhuang∗, Shuguang Zhang, Haijun Hao, Long Jiang
Department of Organic Chemistry, Faculty of Science, Beijing University of Chemical Technology, Beijing 100029, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 3 May 2013
Received in revised form 29 June 2013
Accepted 8 July 2013
Available online 23 July 2013
The photocycloaddition of 1-(4-R-phenyl)-2-(4-pyridyl)acetylenes (R = H, Br, CH3, Cl) and 1-(4-R-
phenyl)-2-(2-pyridyl)acetylenes (R = H, Br, Cl) was carried out in acidic aqueous solution. The
unexpected photo-dehydro-Diels–Alder reaction of these monomers was observed, and the results
show that two monomers react in a head-to-tail manner and lead to the formation of 2-phenyl-1,3-
di(pyridyl)naphthalene derivatives. This reaction presents a direct metal-free method to construct the
1,2,3-triaryl substituted naphthalenes from diarylacetylenes.
Keywords:
© 2013 Elsevier B.V. All rights reserved.
Photo-dehydro-Diels–Alder reaction
Photodimerization
Diarylacetylene
Naphthalene
Head-to-tail
1. Introduction
acidic aqueous solution [21–24].
In recent years, photo-dehydro-Diels–Alder (PDDA) reaction has
been reported, which provides a new method to construct a con-
siderable variety of substituted naphthalene derivatives [1,2]. The
In this paper, we synthesized 1-phenyl-2-(4-pyridyl)acetylene
to explore its photochemical properties in 1 M HCl aqueous solu-
tion, and to verify whether the heteroarylacetylene has a similar
photo property as heteroarylethene. To our surprise, a new pho-
todimer with the structure of 1,2,3-triaryl substituted naphthalene
is formed as the main product. A literature survey revealed that the
reaction of N-heteroarylacetylenes in acidic aqueous solution and
this reaction is a direct method to construct 1,2,3-triaryl substituted
naphthalene structure without metal catalyst or organic solvents
(Scheme 1).
C
Wessig has reported the extensive studies on the intermolecular
and intramolecular [4 + 2] PDDA reaction. The synthesis of phenyl-
naphthalenes [3–5], 1,1ꢀ-binaphthyls [6,7], N-heterocyclic analogs
of phenylnaphthalenes [8], and highly strained naphthalenophanes
[9] are accomplished by the PDDA reaction using 3-arylynones
and arylacetylenes in organic solvents upon the irradiation of UV
light. Though the PDDA reaction is an efficient route to synthesize
naphthalenes, the starting materials always contain arylynones or
arylacetylenes and the PDDA reaction of other functional molecules
It is well-known that the photodimerization of diarylethenes
will form a cyclobutane ring, and among these diarylethenes,
stilbenes and styrylpyridine derivatives are the most studied
ones [10–20]. In the past few years, we have been studying
the photodimerization of some N-heteroarylethenes, such as
The synthesis of 1,2,3-triphenylnaphthalene derivatives from
diphenylacetylenes by mesoporous graphitic C3N4 catalyst [25], by
RhCl(PPh3)3-based catalyst [26] or by other conditions have been
of 1-phenyl-2-(pyridyl)acetylene can be carried out in mild condi-
tions without the presence of any metal-catalyst and without inert
atmosphere. Compared with the arylynones and arylacetylenes
reported by Wessig et al. [1], the diarylacetylene monomers used in
this paper is simple and easy to prepare. The PDDA reaction of such
monomers extends the scope of PDDA reactions from monoary-
lacetylenes to diarylacetylenes and from organic solvent to aqueous
solution.
∗
Corresponding author. Tel.: +86 10 64412948.
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