8144
J. Am. Chem. Soc. 1996, 118, 8144-8145
Carbene-to-Carbene Oxygen Atom Transfer
Table 1. Thermochemistry of Oxygen Donors and Selected Rate
Constants for Their Reactions with Fluorenylidene
∆
Ha
†
†
‡
Dalila Kovacs, Ming-Shi Lee, David Olson, and
kXO(LFP)
× 10
-8 d
James E. Jackson*,
†
X:
X:
XO BDEb CSEc
kXO/kMeOH
1
1
:
C:
201 -26 286
51
0
9
H2C:
102 -26 187
Department of Chemistry, Michigan State UniVersity,
East Lansing, Michigan 48824-1322
Department of Chemistry, The Ohio State UniVersity
f
Fl:
F2C:
(
(
(
133e
13 179
-45g -153 168
-35h -139 163
39 -59 158
57
MeO)2C:
H2N)2C:
Me2N)2C:
C2H4(NMe)2C:
CO
(MeO)3P:
C4H8SO
Z-2-butene
E-2-butene
C5H5N:
92 (1.2(0.2)×10-3 0.01
Columbus, Ohio 43210-1173
79
i
-1
44 -57 160
72 (4.9(0.2)×10
2.6 (3)
2.8
ReceiVed April 22, 1996
i
-1
56 -41 156
(5.2(0.2)×10
:
-26 -94 127 120
-167 -265 158
-35 -88 113
(1.4(0.2)×10-
2
0.8
We present here evidence for carbene-to-carbene oxygen atom
transfer, R2C: + OdCR′2 f R2CdO + :CR′2. Singlet atomic
carbon abstracts oxygen atoms from a variety of carbonyl
-2 -30
-3 -31
33
25
88
88
79
79
3
9
1
compounds to make carbon monoxide and carbenes; these
14
6
1.7(0.4
1.7(0.4
9 (4.8)
9
highly exothermic processes can produce “hot” carbenes with
unusual behavior.2 We now report that the reactive carbenes
fluorenylidene (Fl:) and methylene (:CH2) behave analogously
if the carbene product is sufficiently stabilized with electron
donor groups (see Table 1).3 Besides its intrinsic interest as an
abstraction of a doubly bonded atom, this reaction represents
a photochemical route to nucleophilic carbenes.
Carbenes do abstract oxygen atoms from suitable donors such
as N-oxides, nitroxides, carbon dioxide, PF3O, or epoxides.
Many carbenes react with molecular oxygen to give carbonyl
4
-MeC5H4N:
a
f
Unless otherwise noted, these are ∆H values at 298 K, from:
Lias, S. G.; Bartmess, J. E.; Liebman, J. F.; Holmes, J. L.; Levin, R.
D.; Mallard, W. G. Gas Phase Ion and Neutral Thermochemistry. J.
Phys. Chem. Ref. Data 1988, 17 (Suppl. 1). b BDE ) bond dissociation
4
c
energy; note that ∆H for oxygen is 59.6 kcal/mol at 298 K.
f
CSE )
f CH
s , obtained with the
carbene stabilization energy, defined as ∆H(:CH + CX
2
2
H
2
4
+
d
8
-1 -1
:
CX
2
). Referenced to kMeOH ) 5 × 10 M
same LFP and protocol (ylide probe method) as the O-donor rate
5
6
7
8
9
8
-1 -1
constants; this value is less than literature values (∼9 × 10 M
s ;
see ref 19). e From MP2/6-31G*//HF/6-31G* energies for X-transfer
1
0
oxides or their isomeric dioxiranes. With simple carbonyl
from FlX to :CH
2
f
, with experimental ∆H values for the reference
compounds, we estimate ∆H
f
(Fl:) ) 129 and 136 kcal/mol for X ) O
†
‡
and X ) H , respectively; the listed value is an average. A previously
Michigan State University.
The Ohio State University.
2
cited value of 156 kcal/mol (Li, Y.; Schuster, G. B. J. Org. Chem.
1988, 53, 1273) was estimated from the semiempirical AM1 calcula-
(
1) (a) Skell, P. S.; Plonka, J. H. J. Am. Chem. Soc. 1970, 92, 836-839.
f
(
b) Dewar, M. J. S.; Nelson, D. J.; Shevlin, P. B.; Biesiada, K., A. J. Am.
tions. Sabbah, R.; Watik, L. E.; Minadakis, C. C. R. Acad. Sci., Ser.
II 1988, 307, 239. From calculated proton affinity (234 kcal/mol at
Chem. Soc. 1981, 103, 2802-07. (c) Ahmed, S. N.; Shevlin, P. B. J. Am.
g
Chem. Soc. 1983, 105, 6488-90.
MP3/6-31+G*//HF/6-31+G*+scaled ZPE) and the experimental ∆H
f
(
2) (a) Shevlin, P. B.; Wolf, A. P. Tetrahedron Lett. 1970, 3987-89.
+
(
97 kcal/mol) of (MeO)
ZPE reaction energies for F
and (H N) C: + (MeO) CdO f (H
2
CH . The MP2/6-31G*//HF/6-31G*+scaled
C: + (MeO) CdO f F CdO + (MeO) C:
N) CdO + (MeO) C: give similar
(
b) Rahman, M.; Shevlin, P. B. Tetrahedron Lett. 1985, 26, 2959-60. (c)
2
2
2
2
Fox, J. M.; Gillen Scacheri, J. E.; Jones, K. G. L.; Jones, M., Jr.; Shevlin,
P. B.; Armstrong, B. M.; Sztyrbicka, R. Tetrahedron Lett. 1992, 33, 5021-
2
2
2
2
2
2
2
4. (d) Armstrong, B. M.; McKee, M. L.; Shevlin, P. B. J. Am. Chem. Soc.
995, 117, 3688-89.
results, -31 and -35 kcal/mol, respectively. The agreement among
these three independent calculations brings into question the -61 kcal/
1
h
(
3) Donor groups strongly stabilize carbenes; see: Wanzlick, H. W.
mol reported in an earlier experimental study (see ref 22). McGibbon,
Angew. Chem., Int. Ed. Engl. 1962, 1, 75-80. In combination with steric
G. A.; Kingsmill, C. A.; Terlouw, J. K. Chem. Phys. Lett. 1994, 22,
protection this effect has recently allowed stable carbenes to be isolated:
i
1
29-34. Substituted diaminocarbene ∆H
f
values were estimated via
(
a) Igan, A.; Grutzmacher, H.; Baceiredo, A.; Bertrand, G. J. Am. Chem.
experimental values and the MP2/6-31G*//HF/6-31G*+scaled ZPE
Soc. 1988, 110, 6463-66. (b) Arduengo, A. J., III; Harlow, R. L.; Kline,
M. J. Am. Chem. Soc. 1991, 113, 361-362. (c) Arduengo, A. J., III; Dias,
R. H. V.; Harlow, R. L.; Kline, M. J. Am. Chem. Soc. 1992, 114, 5530-
reaction energies for oxygen exchange with urea.
3
4. (d) Kuhn, N.; Kratz, T. Synthesis 1993, 561-62. (e) Alder, R. W.; Allen,
compounds such as aldehydes,11 ketones,12 esters,13 amides,14
and ureas, electrophilic singlet carbenes attack the oxygen lone
electron pairs to form carbonyl ylides 1. These intermediates
may then cyclize to form epoxides or undergo cycloaddition
with a second equivalent of carbonyl compound to give
A third, almost unexplored, pathway is
fragmentation to a new carbene/carbonyl compound pair.
D. R.; Williams, S. J. J. Chem. Soc., Chem. Commun. 1995, 1267-68. (f)
1
5
Arduengo, A. J., III; Goerlich, J. E.; Marshall, W. J. J. Am. Chem. Soc.
1
995, 117, 11027-28.
(
4) Carbenes commonly abstract monovalent atoms or groups: broadly,
16
triplets take hydrogen and singlets halogen to yield radical pairs which may
couple, disproportionate, or diffuse apart. (a) Kirmse, W. Carbene
Chemistry, 2nd ed.; Academic Press: New York, 1971. (b) Roth, H. D.
Acc. Chem. Res. 1977, 10, 85-91. (c) Platz, M. S. Acc. Chem. Res. 1988,
1
1,12g
dioxolanes.
2
1, 236-42. (d) Platz, M. S.; Maloney, V. M. In Kinetics and Spectroscopy
1
7
Indeed, Warkentin et al. have shown that explicit synthesis
of Carbenes and Biradicals; Platz, M. S., Ed.; Plenum Press: New York,
990; Chapter 8.
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1
(
(11) L’Esperance, R. P.; Ford, T. M.; Jones, M., Jr. J. Am. Chem. Soc.
1988, 110, 209-13.
(
(
(12) (a) Shimizu, N.; Bartlett, P. D. J. Am. Chem. Soc. 1978, 100, 4260-
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1987, 2135-38.
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1
2.
(
7) (a) For CO2 + CH2, see: Kistiakowsky, G. B.; Sauer, K. J. Am.
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1
1
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2
0, 159-73.
(
(
(
8) Mahler, W. J. Am. Chem. Soc. 1968, 90, 523-24.
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