Search for dioxocarbenes in photochemical reactions of 5-diazo-4,6-dioxo-1, 3-dioxanes, associated diazirines, and S-ylides

Article abstract of DOI:10.1016/j.tetlet.2004.11.102

On direct photolysis of 2,2-dialkyl-5-diazo-4,6-dioxo-1,3-dioxanes in the presence of pyridine, methanol or dimethyl sulfide as carbene traps, the yield of 'carbene' products does not exceed 27-28%. At the same time photochemical transformations of the re

Full text of DOI:10.1016/j.tetlet.2004.11.102

Tetrahedron
Letters
Tetrahedron Letters 46 (2005) 435–438
Search for dioxocarbenes in photochemical reactions of
-diazo-4,6-dioxo-1,3-dioxanes, associated diazirines, and S-ylides
5
a
V. V. Shevchenko, N. N. Khimich, M. S. Platz and V. A. Nikolaev
a
b
a,
*
a
Saint-Petersburg State University, St.-Petersburg, University prosp. 26, 198504, Russia
b
Ohio State University, 120 West 18th Avenue, Columbus, OH 43210, USA
Received 7 October 2004; revised 12 November 2004; accepted 17 November 2004
Available online 7 December 2004
Abstract—On direct photolysis of 2,2-dialkyl-5-diazo-4,6-dioxo-1,3-dioxanes in the presence of pyridine, methanol or dimethyl sul-
fide as carbene traps, the yield of ÔcarbeneÕ products does not exceed 27–28%. At the same time photochemical transformations of the
related 3,3-diacyldiazirines and dioxosulfonium ylides of this series, evidently, occur without generation of carbene intermediates.
Ó 2004 Elsevier Ltd. All rights reserved.
Useful information on the intermediacy of carbenes in
chemical reactions can be obtained by generating these
species from independent precursors. A potential source
of carbenes, which complements diazo compounds and
processes: Wolff rearrangement (W.R.) and isomeriza-
tion of diazo compound 2a to 3,3-diacyldiazirine
3a. The results of laser flash photolysis (LFP)
(XeF, 351 nm) studies of diazodioxane 2a in the pres-
5
b,c,6
1
,2
3
diazirines are ylides.
ence of pyridine also gave evidence of W.R. under these
5
d
conditions. At the same time, direct photolysis of dia-
zodioxane 2a in the presence of alkene carbene traps
4
This work is concerned with a comparison of the pho-
tochemical reactions of potentially independent precur-
sors of dioxocarbenes 1, namely, diazo compounds 2,
diazirines 3, and S-ylides 4 (Scheme 1).
5
a
gave very low yields of cyclopropanes (1–2%), which
7
are typical carbene reaction products.
Photochemical transformations of 3,3-diacyldiazirines 3
and dioxosulfonium ylides 4 have not been previously
4,6
investigated.
Previous investigations of the photochemical reactions
5
,6
of diazodioxodioxane 2a using long wavelength irra-
diation (k > 280 nm) revealed two main photochemical
We have studied pyridine, methanol, and dimethyl sul-
fide as carbene traps in the photochemical reactions of
2–4 (Scheme 1). Irradiation of substrates 2–4 was typi-
O
O
O
Me
Me
R
O
O
O
O
R
O
O
8
R
N
N
+
-
S
-
N
2
;
R'
;
R'
R'
cally performed by conventional photolysis using a med-
ium-pressure Hg-lamp through quartz (k > 210 nm),
pyrex (k > 280 nm) or Ôsimple glassÕ (k > 310 nm) filters
without any further monochromatization. Pyridine has
O
O
?
O
4a,b
2
a,b
3a,b
hv
9
been previously used in LFP experiments.
O
R
O
O
Attempts to detect the generation of ylides of dioxocarb-
enes 1a,b using LFP of diazodioxodioxanes 2a,b in solu-
tions of cyclohexane or 1,1,2-trifluorotrichloroethane
a: R, R' = Me, Me
b: R, R' = t-Bu, Me
:
R'
O
1a,b
1
0
with pyridine failed. Thus, in succeeding experiments
more effective traps of dioxocarbenes, namely methanol
Scheme 1.
1
1
and dimethyl sulfide were employed in conditions of
1
conventional photolysis.
2
Keywords: Diazo compounds; Diazirines; Sulfonium ylides; Carbenes;
Photochemistry.
*
Corresponding author. Tel.: +7 812 323 10 68; fax: +7 812 428 69
9; e-mail: vnikola@vn6646.spb.edu
Irradiation of diazodioxodioxanes 2a,b in a solution of
pure methanol through a quartz filter (k > 210 nm)
3
0
040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.11.102

436
V. V. Shevchenko et al. / Tetrahedron Letters 46 (2005) 435–438
Table 1. Photolysis of diazodioxodioxanes 2a,b
lysis of diazo compounds 2a,b depends to a certain ex-
tent on the wavelength of irradiation and the nature of
the solvent/trap, were only 27–28% and 9–13%, respec-
tively. The formation of insertion products 8a,b
into the O–H bond of MeOH was observed only quali-
tatively by the appearance of the relevant signals of
the methine proton of the H–COMe group at 6.30
Diazo Reaction conditions
Yields of the products, (%)
a
3
5/6
7
4
b
2
2
2
2
2
2
a,b
a,b
a,b
a
k > 210 nm, 1–2 h
5–12
56/64 3–6
30/31 7–9
13/18 5–13
—
—
b
k > 280 nm, 6 h
k > 310 nm, 9 h
24–25
43–44
13 (12)
b
—
27
c,d
k > 210 nm, 1.3 h
Me S; k > 310 nm, 28 h
k > 310 nm, 8 h
0/48
—
1
e
and 6.34 ppm in H NMR spectra of reaction
mixtures.
a,b
b
2
27–28
2
c
43 (19)
0/19
—
a
b
c
In brackets are given the percentage of diazo compound 2 in the
reaction mixture.
Thus, one can conclude that the contribution of carb-
enic processes in the photochemical reactions of diazo
compounds 2a,b does not exceed 27–28% (Table 1).
Diazirines 3 and S-ylides 4, which are formed on long
wavelength irradiation of diazodioxodioxanes 2, are
photochemically rather stable and do not experience sig-
nificant further transformations under these conditions.
As a consequence, photolysis of diazirines 3 and S-ylides
00
Reaction was carried out in solution of THF/R OH (molar ratio of
R OH/2a,b = 10/1).
00
Reaction was carried out in solution of Me
MeOH/2a,b = 10/1).
2
S/MeOH (molar ratio of
d
e
1
The yields of the products were calculated from the data of H NMR
spectra of reaction mixture after photolysis.
Quantity of other reaction products were not estimated.
4
in subsequent experiments were performed with short
wavelength irradiation (k > 210 nm).
furnished, with high yields, only W.R. products—Me-
esters 6a,b (more then 85–90%) (Table 1 and Scheme
Before proceeding to investigate the photochemistry of
14
1
3
2
THF/H O or MeOH (mole ratio NuH/1a,b = 10/1) also
). Photolysis of diazodioxanes 2a,b in a mixture of
the diazirines we established that the lifetimes of dioxo-
diazirines 3a,b at 50 °C are 3.5–3.6 h in solution in
2
gave rise mainly to the W.R. products 5,6 (56–64%), but
here small amounts of diazirines 3a,b (5–12%), and
dioxodioxanes 7a,b (3–6%) were also formed.
CDCl and about 4 h—in solution in C D . Since pho-
3
6
6
tochemical experiments with diazirines 3 were carried
out at lower temperatures (18–20 °C) and for shorter
times (1–1.5 h) it was assumed that the thermal transfor-
mations of these diaza-substrates could be safely
ignored.
Photolysis of diazo compounds 2 through a Pyrex filter
(
k > 280 nm) yielded the same three reaction products,
but the yield of diazirines 3 in these irradiation condi-
tions was considerably increased (24–25%) with a corre-
sponding reduction of the yield of W.R. products
15
Photolysis of diazirines 3a,b through a quartz filter
(
k > 210 nm) in solution in MeOH or in a mixture of
(
30–31%). Finally, on irradiation of diazodioxanes 2
THF/MeOH (mole ratio MeOH/3 = 10/1) led solely to
W.R. products 6 (more than 85–90%) (Table 2 and
Scheme 3). The only ÔsideÕ products in the reaction mix-
tures which we managed to identify by means of H
NMR and TLC were traces of 4,6-dioxo-1,3-dioxanes
7. It is significant that no detectable amount of diazodi-
oxodioxanes 2 were revealed at any stage of the photo-
reaction, which was monitored by
spectroscopy at 5–10 min intervals.
with long wavelength UV light (k > 310 nm) the
efficiency of the two main photoprocesses (isomerization
to diazirines and W.R.) in comparison with short wave-
length irradiation was reversed (43–44% and 13–18%
correspondingly).
1
1
The maximum yields of carbene products—sulfonium
7
ylides 4a,b and dioxodioxanes 7a,b —produced on photo-
H
NMR
At the same time, formation of diazo compounds 2 (6–
%) and sulfonium ylides 4 (14–16%), along with W.R.
products 6 (49–52%), was found upon photolysis of
8
O
O
R
N2
diazirines 3a,b in a solution of Me S/MeOH (mole ratio
2
R'
O
MeOH/3a,b = 10/1) (Table 2). It seems likely that under
these conditions isomerization of diazirines 3 into diazo
compounds 2 occurs partially with their subsequent car-
benic decomposition to S-ylides 4.
O
a,b
2
MeOH pure,
THF/ R''OH,
Me S/MeOH
o
hv, 20 C
2
O
O
R
3a,b + 4a,b +
R'
O
CO R''
Table 2. Photolysis of diazirines 3a,b (k > 210 nm)
2
5
,6a,b
Diazirine Reaction conditions
Product yield (%)
O
O
H
O
O
O
R
R'
R
R'
2
4
6
7
+
O
OMe
O
a,b
2
a,b
a,b
MeOH; 1.3 h
THF/MeOH;
—
—
—
—
95–97 Traces
89–97 Traces
O
a,b
2
7
8
0
.8–1.3 h
Me S/MeOH;
.1–1.25 h
5: R''=H; 6: R''= Me
2
a,b
2
6–8 14–16 49–52
—
1
Scheme 2.

V. V. Shevchenko et al. / Tetrahedron Letters 46 (2005) 435–438
437
O
O
References and notes
R
O
O
N
N
R'
1. (a) Carbene Chemistry; Bertrand, G., Ed.; Marcel Dekker:
New York, 2002; p 301; (b) Zollinger, H. Diazo Chemistry
II; VCH Verlagsgesellshaft: Weinheim, 1995; p 305.
3
a,b
2
. (a) Liu, M. T. H.; Stevens, I. D. R. Thermolysis and
Photolysis of Diazirines. In Chemistry of Diazirines; Liu,
M. T. H., Ed.; CRC: Baton Rouge, FL, 1987; Vol. 1, pp
MeOH pure,
THF/ MeOH,
o
hv, 20 C
Me S/MeOH
2
1
11–160; (b) Doyle, M. P. In The Selectivity of Carbenes
Generated from Diazirines; Liu, M. T. H., Ed.; CRC:
Baton Rouge, FL, 1987; Vol. II, pp 33–74; Bonneau, R.;
Liu, M. T. H. 1,2-Hydrogen Migration in Carbenes: LPF
and beyond In Advances in Carbene Chemistry; Brinker,
U. H., Ed.; JAI: Stamford, 1998; Vol. 2, pp 1–35.
. (a) Camacho, B. M.; Clark, A. E.; Liebrecht, T. A.;
DeLuca, J. P. J. Am. Chem. Soc. 2000, 122, 5210–5213; (b)
Neilands, O. Latvian J. Chem. 2002, 1, 27–59; (c) Mueller,
P.; Yves, A.; Estelle, R. Tetrahedron: Asymmetry 2003, 14,
779–785.
O
Me
O
R
O
O
R
O
O
-
S
+
Me
+
+
7a,b
R'
R'
CO Me
2
O
a,b
4
6a,b
3
Scheme 3.
Photochemical transformation of S-ylides 4 proceeds in
a quite different manner than photolysis of diaza-ana-
logs 2 and 3 (Scheme 4). The main photo-process in this
case is not elimination of Me S, but intramolecular
2
,2-migration of a methyl group (Stevens rearrange-
ment) and apparently subsequent cleavage by a Norrish
Type II photoreaction of the initially formed 5-methyl-
-(methylthio)-substituted dioxodioxanes 9a,b to pro-
duce 5-methyldioxanes 10a,b [ratio of stereoisomers in
the case of 10b was about 4/1].
4. (a) Shevchenko, V. V.; Nikolaev, V. A.; Platz, M. S.
Abstracts of ISRIUM-2002, Switzerland, Ascona, July 7–
12, 2002, 48; (b) Khimich, N. N.; Candidate Diss.,
Leningrad State University, USSR, 1989, 127 p.
1
6
1
5
. (a) Jones, M.; Ando, W.; Hendrick, M. E.; Kulczycki, A.;
Howley, P. M.; Hummel, K. F.; Malamet, D. S. J. Am.
Chem. Soc. 1972, 94, 7469–7479; (b) Livinghouse, T.;
Stevens, R. V. J. Am. Chem. Soc. 1978, 100, 6479–6482; (c)
Nikolaev, V. A.; Khimich, N. N.; Korobitsyna, I. K.
Chem. Heterocycl. Comp. (Russ.) 1985, 321–325; (d)
Wang, J.-L.; Toscano, J. P.; Platz, M. S.; Nikolaev, V.
A.; Popik, V. V. J. Am. Chem. Soc. 1995, 117, 5477–5483.
. During completion of the experimental part of this project
an article appeared considering the photoreactions of
diazodioxodioxane 2a and corresponding diazirine 3a.
See: Bogdanova, A.; Popik, V. V. J. Am. Chem. Soc. 2003,
5
Thus, chemical analysis of photolysis mixtures indicates
that during photolysis of dioxosulfonium ylides 4a,b
under the specified conditions the generation of carbene
products [O–H-insertion 8, dioxodioxanes 7 etc.] is not
observed.
6
7
1
25, 1456–1457.
. (a) By Ôtypical carbene reaction productsÕ, besides cyclo-
propanes, we mean here formation of pyridinium, oxo-
nium or sulfonium ylides plus H-abstraction products.
The occurrence of these latter is commonly assigned to the
In summary, diazo compounds 2 and diazirines 3 of
the 4,6-dioxo-1,3-dioxane series on short wavelength
irradiation (k > 210 nm) are mainly decomposed
with elimination of dinitrogen, whereas in the case of
dioxosulfonium ylides 4 an intramolecular 1,2-shift of
a methyl group (Stevens rearrangement) prevails fol-
lowed by photochemical transformations of the original
reaction products. The yield of carbene processes real-
ized upon direct photolysis of diazo dioxodioxanes 2
using the most efficient trap (dimethyl sulfide) is only
5
a,7a–c
reactions of triplet carbenes.
Okada, T.; Kawanisi, M. Bull. Chem. Soc. Jpn. 1970, 43,
506–2511; (b) Ando, W. Photochemistry of Diazocom-
Hayashi, Y.;
2
pounds. In The Chemistry of Diazonium and Diazo Groups;
Patai, S., Ed.; Wiley: Chichester–Toronto, 1978; P. 1, pp
439–442; (c) Kirmse, W. Adv. Carbene Chem. 1994, 1, 39–
42.
8
. Diazo compounds 2a,b were prepared from 4,6-dioxo-1,3-
dioxanes 7 using the diazo transfer reaction. Diazirines
2
7–28%, yet photolysis of diacyldiazirines 3 and S-ylides
of this series, evidently occurs without generation of
8a
4
the corresponding heterocyclic dioxocarbenes 1.
3
a,b were synthesized with the help of photochemical
isomerization of diazodioxodioxanes 2a,b by long wave-
length irradiation (k > 280 nm) in solution of THF
4
b,5c
with nucleophiles (H
4
in dimethyl sulfide.
2
O, MeOH or Me
2
S).
S-Ylides
a,b were obtained by photolysis of diazo compounds 2a,b
8
b,c
O
See: (a) Popik, V. V.; Korneev, S.
R O
+ Me
S
Me
M.; Nikolaev, V. A.; Korobitsyna, I. K. Synthesis 1991,
195–198; (b) Illger, W.; Liedhegener, A.; Regitz, M.
Liebigs Ann. 1972, 760, 1–16; (c) Nikolaev, V. A.; French,
J.; Korobitsyna, I. K. J. Org. Chem. (Russ.) 1978, 14,
-
R'
O
4
O
a,b
1
433–1441.
MeOH pure,
THF/ MeOH
o
hv, 20 C
9. Platz, M. S.; Maloney, V. M. Laser Flash Photolysis
Studies of Triplet Carbenes. In Kinetics and Spectroscopy
of Carbenes and Biradicals; Platz, M. S., Ed.; Plenum: New
York, 1994; pp 239–352.
0. Platz, M. S. Observing Invisible Carbenes By Trapping
Them With Pyridine. In ÔCarbene ChemistryÕ, pp 27–56,
and references cited therein.
O
O
R O
R'
SMe
R O
R'
Me
+
1
H
O
Me
O
O
O
9
a; 5%
10a,b; 62-63%
1
1. Shevchenko, V. V.; Zhegalova, N. G.; Platz, M. S.;
Nikolaev, V. A. J. Org. Chem. (Russ.), in press.
Scheme 4.

438
V. V. Shevchenko et al. / Tetrahedron Letters 46 (2005) 435–438
1
using H spectra of individual compounds, obtained in the
course of preparative photolysis of diazo compounds
2a,b.
1
2. The conventional photolysis of compounds 2–4 was
performed in solutions of THF or Me S in the presence
of nucleophiles (H O, MeOH) with a mol ratio ꢀ 1/10
2
2
(
substrate/nucleophile), or directly in solutions of MeOH,
15. Typical procedure for photolysis of diazirines 3: a solution
of diazirine 3a (0.22 g, 1.3 mmol) in 20 ml of freshly
distilled THF and 1 ml MeOH was irradiated
(k > 210 nm) for 60 min, while samples (0.5 ml) of reaction
mixture were taken at 5–10 min intervals. Easily volatile
material from each sample was evaporated in vacuo (1–
2 mmHg, 18–20 °C), internal standard (p-C H Br ) was
Me S. Isolated compounds were identified with the help of
2
1
13
H, C NMR and mass spectra. All new compounds were
characterized and gave satisfactory spectral data.
1
3. Typical procedure for photolysis of diazodioxanes 2: a
solution of 1.09 g (5 mmol) of diazo compound 2b in
Me S/MeOH (70/1 ml) was irradiated (k > 310 nm) during
2
6
4
2
8 h. On completion of the photolysis the solvent and
nucleophile were removed in vacuo, the crude reaction
added to the residue and quantitative composition of each
1
sample was determined by H NMR spectroscopy. Thus,
1
mixture was analyzed by H NMR spectroscopy and
components of the reaction mixture after photolysis of
diazirine 3a were identified as the methyl ester of 5-
thereafter separated using chromatography on neutral
silica gel (30 g; eluents 0–100% Et O/petroleum, then pure
5
a,c
2
oxocarboxylic acid 6a
( > 95%) and traces of dioxane 7.
EtOH) to give the products: diazirine 3b, 456 mg (43%);
methyl esters 7b, 200 mg (19%, ratio of stereoisomers ꢀ 1/
16. Photoreactions of S-ylides 4 were carried out on a
preparative scale. Typical procedure: a solution of 0.49 g
(2 mmol) of S-ylide 4b in 20 ml of freshly distilled THF
and 1 ml of MeOH was irradiated (k > 210 nm) for 3 h,
unreacted ylide was separated by filtration, the residue
after evaporation of the solvent and MeOH in vacuo was
subjected to chromatography on silica gel (30 g, eluents 0–
1
.5); diazodioxodioxane 2b, 200 mg (19%); sulfonium ylide
4b, 21 mg (2%).
1
4. On investigation of the reactions of diazirines 3a,b and
during kinetic experiments, an analytical alternative was
applied for the determination of composition of reaction
1
mixture using H NMR spectroscopy (internal standard p-
2
100% Et O/petroleum) to give 5-methyldioxodioxanes 10b
C
6
H
4
Br
2
) without isolation of reaction products. In these
(248 mg, 62%) as a mixture of cis- and trans-stereoisomers
1
cases the products in analyzed solutions were identified
ꢀ 1/4 (by H NMR spectra in CDCl ).
3