J . Org. Chem. 1997, 62, 761-764
761
Ta ble 1. IR Sp ectr oscop ic Da ta of (s-Z)-2 Ma tr ix
Isola ted in Ar gon a t 10 K
P h otolysis of Dia zo(3-th ien yl)m eth a n e: A
Sim p le Syn th esis of a
argon, 10 K MP2/6-31G(d)
ν (cm-1 Irelb
Meth ylen ecyclop r op en e
Nra
)
Irelb
νc (cm-1
)
Reinhard Albers and Wolfram Sander*
1
2
3
4
5
6
7
8
9
0
1
2
3
14
15
16
7
8
9
108
136
275
339
422
453
645
785
833
0
0
0
0
1
1
7
1
2
0
4
0
3
4
2
26
1
6
Lehrstuhl f u¨ r Organische Chemie II der Ruhr-Universit a¨ t,
D-44780 Bochum, Germany
450
653
754
828
6
11
7
Received J une 27, 1996
12
In tr od u ction
1
1
1
1
837
865
910
Methylenecyclopropene and its derivatives are in gen-
eral highly reactive species and have been the target of
1005
1013
1098
1182
1253
1405
1501
1718
2956
25
8
7
25
3
13
90
100
4
1007
1020
1088
1190
1252
1418
1508
1756
2963
3083
3155
3191
1
-6
a number of syntheses.
In solution, the parent com-
pound was synthesized and characterized independently
5
6a
by Billups et al. and Staley and Norden in 1984. It is
stable at temperatures below -90 °C but rapidly decom-
poses above -75 °C. Simple alkyl-substituted methyl-
1
1
1
28
100
2
0
1
3
enecyclopropenes are still highly reactive. Here, we
20
21
2
3
4
report on the synthesis and matrix spectroscopic char-
acterization of R-thial methylenecyclopropene utilizing
a carbene rearrangement.
2
2
2
3137
3
1
a
Number of vibration. b Relative intensities based on the most
Resu lts a n d Discu ssion
intense band (100). c Calculated frequencies are scaled by 0.95.
The assignment of experimental and calculated frequencies is
tentative and based on band positions and relative intensities.
Diazo(3-thienyl)methane (1) was synthesized via the
Bamford-Stevens reaction according to a modified pro-
cedure by Hoffman and Shechter, who reported the in
situ generation of 1.7 Warming the lithium salt of
thiophene-3-carbaldehyde tosylhydrazone to 115 °C re-
sulted in the formation of 1, which was collected at -78
Ta ble 2. IR Sp ectr oscop ic Da ta of s-tr a n s-Ald eh yd e
(s-E)-2, Ma tr ix Isola ted in Ar gon a t 10 K
argon, 10 K
ν (cm-1
MP2/6-31G(d)
νc (cm-1 Irelb
Nra
)
Irelb
)
°
C. For matrix isolation experiments diazomethane 1
1
2
3
4
5
6
7
8
9
129
137
228
326
461
616
677
743
790
0
0
1
0
1
6
7
7
0
was directly sublimed from the lithium salt with a large
excess of argon on top of a cold spectroscopic window.
The orange red 1 exhibits UV absorption maxima at 227,
2
57, and 290 nm; however, due to the low concentration
445
630
2
14
in the matrix isolation experiments, the weak absorption
in the visible region could not be observed. The IR
spectrum of 1 shows a very strong absorption at 2066
769
21
-
1
cm , characteristic for the CdNdN moiety.
1
0
847
0
Irradiation of 1 in argon at 10 K with λ > 435 nm
within several minutes resulted in the complete disap-
pearance of all IR vibrations assigned to 1 and formation
of a new compound 2 with intense vibrations at 1718 and
11
863
890
958
1006
1089
1167
2
4
4
19
6
44
878
894
940
1010
1096
1178
1353
1386
1
1
0
4
1
24
0
1
1
1
1
2
3
4
5
-
1
1
501 cm
(Table 1). 2 is photolabile under these
16
17
conditions, and prolonged irradiation (several hours)
produces an isomer with similar strong bands at 1712
1
8
1357
364
32
38
62
100
97
3
2
5
3
30
1
-
1
and 1480 cm
(Table 2). The isomerization is not
1
2
9
0
1480
1712
1714
2964
3139
3152
3196
1485
1746
29
100
quantitative, and shorter wavelength irradiation results
in the decomposition of both isomers. By comparison of
the IR spectra with ab initio calculated spectra and with
21
2987
3081
3158
3204
5
1
1
1
2
2
2
2
3
4
(
1) Kende, A. S. J . Am. Chem. Soc. 1963, 85, 1882-1884.
(2) Billups, W. E.; Blakeney, A. J . J . Am. Chem. Soc. 1976, 98, 7817-
7
3
818.
a
Number of vibration. b Relative intensities based on the most
(
3) Stang, P. J .; Mangum, M. G. J . Am. Chem. Soc. 1975, 97, 3854-
intense band (100). c Calculated frequencies are scaled by 0.95.
856.
(
The assignment of experimental and calculated frequencies is
tentative and based on band positions and relative intensities.
4) Maier, G.; Hoppe, M.; Lanz, K.; Reisenauer, H. P. Tetrahedron
Lett. 1984, 25, 5645-5648.
5) Billups, W. E.; Lin, L-J .; Casserly, E. W. J . Am. Chem. Soc. 1984,
06, 3698-3699.
6) (a) Staley, S. W.; Norden, T. D. J . Am. Chem. Soc. 1984, 106,
699-3700. (b) Norden, T. D.; Staley, S. W.; Taylor, W. H.; Harmony,
(
1
related compounds, the isomers were identified as (s-Z)-
and (s-E)-R-thial methylenecyclopropene (2).
(
3
M. D. J . Am. Chem. Soc. 1986, 108, 7912-7918.
7) (a) Hoffman, R. V.; Shechter, H. J . Am. Chem. Soc. 1971, 93,
940-5941. (b) Hoffman, R. V.; Orphanides, G. G.; Shechter, H. J . Am.
Chem. Soc. 1978, 100, 7927-7933.
8) Chapman, O. L. Pure Appl. Chem. 1974, 40, 511-523.
The two strongest IR bands in 2 are assigned to the
asymmetric and symmetric combination of the CdC
stretching vibrations νasym and νsym (Tables 1-3, Figure
(
5
5
(
1). Compared to the parent methylenecyclopropene,
S0022-3263(96)01217-0 CCC: $14.00 © 1997 American Chemical Society