Laˆn et al.
ment of a new, sharp, weak-to-medium intensity absorp-
tion band at 2089 cm-1. The best wavelength for the
formation of this band was 222 nm. This band is ascribed
to the 2-diazomethylquinoline 19′, but since diazo com-
pounds usually have very high extinction coefficients, it
can be concluded that the photolysis was very inef-
ficient.11 Similar photolysis of triazoloisoquinoline 29
produced a new, weak and sharp band at 2092 cm-1
assigned to 1-diazomethylisoquinoline 29′. In photolyses
where 19′ was present, a new multiplet was also present
at 1913-1926 cm-1. The characteristic band structure
identifies the carrier as the cyclic ketenimine 22 (8),
whose IR spectrum has been described in detail else-
where.3 The amount of diazo compound 29′ formed from
triazoloisoquinoline 29 was insufficient to allow a firm
identification of the cyclic ketenimine 32. We have
experienced difficulty in photolyzing matrix-isolated tri-
azoloazines in other cases.17 The tetrazolylazines are
generally inert under matrix photolysis conditions. As
mentioned in the Introduction, photolysis of the matrix-
isolated triazoles in the cavity of an ESR spectrometer
easily allows the observation of the triplet carbenes 23
and 33,5 and FVT of the triazoles and tetrazoles with
matrix isolation of the products in the ESR cryostat
allows the direct observation of the triplet nitrenes 21
and 31.5 Thus, most of the intermediates involved in the
quinolyl- and isoquinolylcarbene-to-naphthylnitrene re-
arrangements have now been observed.18
Exp er im en ta l Section
The procedures used for flash vacuum thermolysis and
matrix isolation have been published.20 A 1000 W high-
pressure Hg/Xe lamp equipped with a monochromator and
appropriate filters, and an excimer lamp operating at 222 nm
(25 mW/cm2) were used for the photolyses.
The 1- and 2-naphthyl azides21 18 and 28, 1,2,3-triazolo-
[1,5-a]quinoline22,23 19, and 1,2,3-triazolo[5,1-a]isoquinoline22
29 were prepared according to literature methods. The 1- and
2-aminonaphthalenes were obtained from a commercial sup-
plier, and the azonaphthalenes were prepared by the method
of Hantzsch and Schmiedel.23
2-(5-Tetr a zolyl)qu in olin e 20. A mixture of 3.08 g (20
mmol) of 2-cyanoquinoline, 1.43 g (22 mmol) of sodium azide,
and 1.15 g (21.5 mmol) of ammonium chloride in 30 mL of
absolute DMF was heated at 100 °C with magnetic stirring
for 5 h. After the mixture was cooled to room temperature,
the inorganic salts were filtered off, and the solution was
evaporated to dryness. The residue was taken up in 5 mL of
water and acidified to pH ) 2. The resulting beige precipitate
was recrystallized from ethyl acetate to yield 3.6 g (92%) of
white needles: mp 192-193 °C dec. Anal. Calcd for C10H7N5
C, 60.91; H, 3.58; N, 35.51. Found: C, 61.10; H, 3.40; N, 35.50.
1-(5-Tet r a zolyl)isoq u in olin e 30 was prepared analo-
gously from 1-cyanoisoquinoline: yield 80%; mp 237-238 °C.
Anal. Calcd for C10H7N5 C, 60.91; H, 3.58; N, 35.51. Found:
C, 61.03; H, 3.72; N, 35.33.
P r ep a r a tive F VT Exp er im en ts. Portions of ca. 400 mg
of the precursors were subjected to FVT at the appropriate
temperature in a dynamic vacuum of 10-3 Torr or at 1 Torr
by using N2 as a carrier gas. The thermolysis products were
isolated in a liquid nitrogen cooled cold trap, dissolved in
absolute ether or chloroform after the end of the thermolysis,
evaporated to dryness, and weighed. The cyanoindenes were
assayed by gas chromatography (10% Carbowax 20M, 165 °C,
Con clu sion
FVT of 1,2,3-triazolo[1,5-a]quinoline 19 and 1,2,3-
triazolo[5,1-a]isoquinoline 29 as well as 2-(5-tetrazolyl)-
quinoline 20 and 1-(5-tetrazolyl)isoquinoline 30 generates
2-quinolylcarbene 23 and 1-isoquinolylcarbene 33, re-
spectively, which rearrange to 1- and 2-naphthylnitrenes
21 and 31, respectively. The nitrenes undergo H-abstrac-
tion to afford aminonaphthalenes, dimerization to azo-
naphthalenes, and ring contraction, initially to 3-cyano-
indene 26. The highly exothermic ring contraction reac-
tion causes chemical activation of 3-cyanoindene, which
therefore undergoes thermal interconversion with the
lower energy 2-cyanoindene 27.
Matrix photolysis of the triazoles permits the detection
of the higher energy diazomethylquinoline and -isoquino-
line valence isomers 19′ and 29′ as well as the cyclic
ketenimine 22 connecting 2-quinolylcarbene and 1-naph-
thylnitrene.
1
carrier gas H2 at 30 mL /min) and H NMR spectroscopy. The
aminonaphthalenes and azonaphthalenes were separated by
column chromatography (SiO2/chloroform). All products were
characterized by direct comparison with authentic samples.
The results are collected in Table 1.
Ack n ow led gm en t. This work was supported by the
Australian Research Council. We thank Mr. Michael
Vosswinkel for assistance with the DFT calculations.
Su p p or tin g In for m a tion Ava ila ble: Computed Carte-
sian coordinates, energies and vibrational data for 3- and
2-cyanoindenes, and the transition states for their intercon-
version at the B3LYP/6-31+G* level of theory. This material
J O035670C
(18) (a) Annelated cyclopropenes may connect 23 with 22 and 33
with 32. These are expected to be high energy, shallow minima or
transition states.3,18b The same is true of the azirines connecting 22
with 21 and 32 with 31.3 (b) Kuhn, A.; Vosswinkel, M.; Wentrup, C. J .
Org. Chem. 2002, 67, 9023.
Com p u ta tion a l Meth od
The calculations of structures and energies of ground and
transition states reported here were carried out at the B3LYP/
6-31+G* and B3LYP/6-31G* levels of theory, using the Gauss-
ian94 suite of programs.19 Each of he transition structures had
one imaginary vibrational frequency, but their locations of the
reaction coordinates were not corroborated by intrinsic reaction
coordinate calculations. The IR spectra of 2- and 3-cyanoindene
were also calculated. The reliability of these computational
methods for the present purposes has been amply demon-
strated.2d,3 There was no significant difference between the
structures and relative energies obtained with the two basis
sets.
(19) Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.; Gill, P. M. W.;
J ohnson, B. G.; Robb, M. A.; Cheeseman, J . R.; Keith, T.; Petersson,
G. A.; Montgomery, J . A.; Raghavachari, K.; Al-Laham, M. A.;
Zakrzewski, V. G.; Ortiz, J . V.; Foresman, J . B.; Cioslowski, J .;
Stefanov, B. B.; Nanayakkara, A.; Challacombe, M.; Peng, C. Y.; Ayala,
P. Y.; Chen, W.; Wong, M. W.; Andres, J . L.; Replogle, E. S.; Gomperts,
R.; Martin, R. L.; Fox, D. J .; Binkley, J . S.; Defrees, D. J .; Baker, J .;
Stewart, J . P.; Head-Gordon, M.; Gonzalez, C.; Pople, J . A. Gaussian
94, revision E.2; Gaussian, Inc.: Pittsburgh, PA, 1995.
(20) Wentrup, C.; Blanch, R.; Briehl, H.; Gross, G. J . Am. Chem.
Soc. 1988, 110, 1874. Kappe, C. O.; Wong, M. W.; Wentrup, C. J . Org.
Chem. 1995, 60, 1686. Kuhn, A.; Plu¨g, C.; Wentrup, C. J . Am. Chem.
Soc. 2000, 122, 1945.
(21) Forster, M. O.; Fierz, H. E. J . Chem. Soc 1907, 1942
(22) Abramovitch, R. A,; Takaya, T. J . Org. Chem. 1972, 37, 2022.
(23) Hantzsch, A.; Schmiedel, M. Ber. Deutsch. Chem. Ges. 1897,
30, 71.
(17) Addicott, C. Ph.D. Thesis, The University of Queensland,
Brisbane, Australia, 2002.
2036 J . Org. Chem., Vol. 69, No. 6, 2004
Lan, Nguyen Mong
