K . N A M B A , * A . M E R A , A . O S A W A , E . S A K U D A , N . K I T A M U R A , K . TA N I N O * ( H O K K A I D O
Ca t e g o r y
U N I V E R S I T Y, S A P P O R O , J A P A N )
Synthesis of
Materials and
Unnatural Products
One-Pot Synthesis of Highly Fluorescent 2,5-Disubstituted-1,3a,6a-triazapentalene
Org. Lett. 2012, 14, 5554–5557.
Tuning The Quantum Yield of Fluorescent
2,5-Disubstituted-1,3a,6a-triazapentalene
Ke y w o rd s
fluorescent dyes
triazapentalenes
one-pot synthesis
R1
OTf
R2
+
R1
N
N
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MeO
N3
1.) CuI (5 mol%)
(Me2NCH2CH2)2O
Et3N, THF
2.) reflux
3.) KHMDS, –78 °C
N
up to 81% yield
R2
R1
R2
Product
1
OMe
Ph
1a
64
2
OMe
CN
1b
60
3
Me
CN
1c
63
4
CN
CN
1d
57
5a
Ph
CN
1e
19
6
Me
OMe
1i
72
7
Me
NO2
1j
27
a The
Yield (%)
triflate was generated in situ and used without purification.
Significance: Rational design of organic molecules with improved photo-physical properties,
such as high quantum yields and tunable fluorescence wavelength, is of great interest in modern
science and technology. In this paper, the authors
report a one-pot synthesis of 2,5-disubstituted1,3a,6a-triazapentalenes. By a cascade sequence
utilizing a copper(I)-catalyzed 1,3-dipolar cycloaddition followed by intramolecular cyclization and
elimination, the authors managed to obtain the
desired 1,3a,6a-triazapentalene skeleton.
Comment: The authors report the synthesis of a
series of 2,5-disubstituted-1,3a,6a-triazapentalenes. These novel compounds allowed the authors to probe the effects of electron-donating
and -withdrawing substituents on the photo-physical properties of 1,3a,6a-triazapentalene derivatives. Introduction of substituents in the 5-position
led to a dramatically increased quantum yield. A
correlation between the Hammet σp-value of the
R2-substituent and the quantum-yield tendency
could furthermore be estimated.
SYNFACTS Contributors: Timothy M. Swager, Jens B. Ravnsbæk
Synfacts 0312013, 9(1), 0043 Published online: 17.12.20121861-19581861-194X
DOI: 10.1055/s-0032-1317891; Reg-No.: S13912SF
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