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o-Benzoquinone Monoformylmethides by Sensitized Photooxygenation of cis--Methoxystyrenes.

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These results point to very efficient photodissociation of
Cu2excited in CH, matrices; this appears to have its origin
in the chemical quenching of the Cu(*D) photofragment:
Cu('D)
+ CHI
-
"CH,
+ CUH
J
This eliminates the competing cage-assisted recombination
pathway which predominates in rare gas
This
proposal is entirely consistent with our observation of a
large, net Cu2 photodissociative yield of the immobilized
ground state [Cu('S)] of Cu atoms, which occurs in addition to the excited state [CU(~D)].
These results may be significant as they point to the possibility of excited state selectivity in the condensed phase
photosensitization reactions of Cu atoms with CH,:
Cu(*D)+CH,
cu(zs)
+
CH4
.Lhslc,\cIuon
------+
"0
reacllon
H,Co
3
+ CUH
Cu + CH,
I
H,O'*
In conclusion, photochemistry of metal atoms and dimetal
species opens u p the possibility of activating saturated hydrocarbons and performing selective alkane transformat i o n ~ " . ~in
] ; this connection certain M2 species can be photoexcited with visible light.
Received: February 12, 1982 [Z 76b IE]
German version: Angew. Chem. 92 (1982) 383
The complete version of this communication appears in:
Angew. Chem. Suppl. 1982, 798-806
CAS Registry numbers:
Cuz, 12190-70-4: CH4, 74-82-8
[I] G . A. Ozin, D. F. Mclntosh, S. A. Mitchell, J. Garcia-Prieto, J . Am. Chem.
SOC.103 (1981) 1574.
131 G . A. Ozin, S. A. Mitchell, J. Garcia-Prieto, Angew. Chem. 94 (1982) 218;
Angew. Chem. I n t . Ed. Engl. 21 (1982) 211.
[5] G. A. Ozin, S. A. Mitchell, J. Garcia-Prieto, L Phys. Chem. 86 (1982)
473.
17) G. A. Ozin, H. X. Huber, D. F. Mclntosh, S. A. Mitchell, J. G. Norman,
Jr., L. Noodleman, J . Am. Chem. SOC.101 (1979) 3504.
o-Benzoquinone Monoformylmethides
by Sensitized Photooxygenation
of cis-0-Methoxystyrenes
By Masakatsu Matsumoto and Keiko Kuroda*
A reactive o-quinone methide"] is often generated as a
reaction intermediate by dehydrationf2'or by pyrolysis[31at
high temperature. Mainly because of these forcing conditions, generation of quinone methides possessing labile
functional groups has hardly been attempted so far. We report here an effective generation of new o-quinone methides 3, which have a formyl group at the exocyclic carbon, from cyclic peroxides 2 of cis-p-methoxystyrenes 1
under mild conditions. These quinone derivatives 3 react
with enol ethers 5 affording 4-formylchromans 7, which
are utilized as versatile intermediates in the synthesis of furobenzofuran-type mycotoxins.
Sensitized photooxygenation of cis-a-methoxystyrene l a
at low temperature gives quantitatively an unstable 1,4-endoperoxide 2al4"],which decomposes into a complex mixture at room t e m p e r a t ~ r e [ ~ ~However,
.'~.
decomposition of
[*I Dr. M. Matsumoto, K. Kuroda
Sagami Chemical Research Center
Nishi-Ohnuma 4-4-1, Sagamihara, Kanagawa 229 (Japan)
382
0 Verlug Chemie GmbH, 6940 Weinheim. 1982
la
la
la
lb
lc
H
H
H
H
PhCH20
H
+
+
+
5a
5b
H
5c
Me0
5a
M e 0 i 5a
H
+
iBu
-CHZCH?Me
iBu
iBu
H
Ph
H
H
----
7a
lb
7~
7d
7e
Za was found to proceed cleanly in the presence of excess
isobutyl vinyl ether 5a ; chromatographic purification of
the reaction mixture afforded a 4-formylchroman 7a in
68% yield['I. In this reaction, the peroxide 2a is believed to
decompose initially into the quinone methide 3a and methanol. Diels-Alder addition of 3a to 5a then leads to the
product 7a. Intermediary 3a was further confirmed by
reaction of 2a with a nucleophile such as thiophenol 4,
which affords a stereoisomeric mixture of lactols 6 in 45%
yield.
The addition of 3a to 2,3-dihydrofuran 5b and cis+
methoxystyrene l a ( = 5c), respectively, afforded the 4-formylchromans 7b (13%) and 7c (54%). Ring-substituted cisp-methoxystyrenes l b and l c gave the chromans 7d (29%)
and 7e (399/0), respectively, when allowed to react with 5a.
On the other hand, reaction of the peroxide from the transisomer of l a with vinyl ethers gave unfavorable results.
The formylchromans 7 are useful synthetic intermediates. For example, under acid catalysis with H,SO, they
give furobenzofurans 8. The reaction sequence described
here is suitable for the synthesis of some mycotoxins possessing a furobenzofuran skeleton such as sterigmatocystin
and a f l a t ~ x i n s ' ~ ~ ] .
Received: February 3, 1981 [Z 89 IEl
German version: Angew. Chem. 92 (1982) 376
[I] For reviews, see J. Colonge, G. Descotes in J. Hamer: 1.4-Cycloaddilion
Reuctions. Academic Press, New York, 1967, p. 217: H. U. Wagner, R.
Gompper in S. Patai: m e Chemistry of Quinonoid Compounds. Wiley,
New York 1974, Pt. 2, p. 1145.
0570-0833/82/0505-0382 CE 02.50/0
Angew. Chem. In:. Ed. Engl. 21 (1982) No. 5
[Z] G. Dumas, P. Rumpf, C . R. Acad. Sci. 242 (1956) 2574.
[3] a ) W. S. Emerson, G. H. Birum, R. 1. Longley, J. Am. Chem. Soc. 7S
(1953) 1312; b) H. Fiesselmann, J. Ribka, Ber. Dtsch. Chem. Ges. 89
(1939) 40.
141 a) D. Lerdal, C. S . Foote, Tetrahedron Lett. 1978. 3227: b) M. Matsumoto,
K. Kuroda, rbid. 1979. 1607: c) some products which might be derived
from 3 were contained in the mixture (see [4b]); d) M. Matsumoto, K.
Kuroda, unpublished results.
151 l a : A solution of cis-8-methoxystyrene la (0.67 g, 5 mmol) and tetraphenylporphyrine ( 5 mg) in CHLC12(20 mL) was irradiated with visible light
under 0,at -78OC until an equimolar amount of oxygen was consumed
(ca. 4 h). lsobutyl vinyl ether 5a (5 g) was added to the mixture which was
allowed to stand for 15 h at 5 ° C . The reaction mixture was condensed tn
uacuo and chromatographed on S i 0 2 (Wako C-200). Elution with CH2C12
gave l a [747 mg, 68% yield based on the consumed la]; b.p. 100°C/0.24
torr: ' H - N M R (CCI,): 6=0.78 (d, J=6.5 Hz, 3H), 0.81 (d, J = 6 . 5 Hz,
3H), 1.52-2.00 (m, 1 H), 2.00-2.20 (m, 2H), 3.12-3.60 (m, ZH), 3.573.80(m, IH),5.05--5.16(m, lH),6.66-7.18(m,4H),9.56(d,J=3.5 Hz,
1 H).
R,
1
R
R
/
3
MTAD
KR
Reaction of 4-Methyl-1,2,4-triazoline-3,5-dione
with Fulvenes: A 1,3-Sigmatropic Shift involving
a Dipolar Intermediate**
/
By Henrik Olsen*
The Diels-Alder reaction of azodicarbonyl compounds
and fulvenes has led to a wide variety of polycyclic N-heterocycles. We have now found that the reaction between 4methyl- 1,2,4-triazoline-3,5-dione
(MTAD) and fulvenes l a
and l b provides novel products, the heptacycles 2a and
2b, respectively, formally derived by successive [6 21- and
[4 21-cycloadditions. Since a [,6, ,2,]-cycloaddition contravenes the Woodward-Hoffmann rules, the mechanistic
details of this reaction were examined more closely.
Surprisingly, the reaction between l a and MTAD at
room temperature did not furnish the expected DielsAlder adduct 3a. The 'H-NMR spectrum of the isolated
product (72% yield) is in complete agreement with the
structure of the bis-adduct 2a. In addition to six singlets
for the methyl groups (6=3.00, 2.98, 1.78, 1.65, 1.44, 1.41)
eight groups of signals for the eight other protons are observed. On the other hand, reaction of MTAD and l b under analogous conditions furnished bis-adduct 2b (86%
yield). Formation of heptacycles 2 strongly suggests that
MTAD reacts initially with 1 to give the 1,6-addition products 4. When the cycloaddition reaction between l a and
l b and MTAD was performed (in the ratio 1 :2) the 1 :2
adducts 5a (49%) and 6a (36%) or 5b (88%), respectively,
could be isolated. Clearly the Diels-Alder reaction of 4a
and 4b with MTAD must be considerably faster than the
dimerization.
In order to establish whether the pathway leading to 4
from 1 and MTAD could proceed via initial [4+2]-cycloaddition followed by a formal [ 1,3]-sigmatropic shift o r
directly via a [6 2]-cycloaddition, MTAD was added to a
CD2CI2 solution of dimethylfulvene l a (1 : 1) in an N M R
tube at -78°C. 'H- [(I00 MHz), 6=6.57 (AA' part of an
AA'XX' system, I - and 1'-H), 5.41 (XX' part, 2- and 2'-H),
+
+
+
+
[*I Dr. H. Olsen ['I
Laboratorium fur Organische Chemie
der Eidgenossischen Technischen Hochschule
ETH-Zentrum, Universitatstrasse 16, CH-8092 Zurich (Switzerland)
['I
[**I
Present address:
Teknologisk lnstitut
Gregersensvej, DK-2630 Tistrup (Denmark)
This work was supported by the Danish Natural Science Research
Council. Prof. Dr. J . F. M. 0 t h (Zurich) and Dr. R. Dyllick-Brezmnger
(Ludwigshafen) are thanked for helpful comments.
Angew. Chem. Int. Ed. Engl. 21 (1982) No. 5
MTAD
CH
n/
5
6
0
8 -
CHsOOH
HOCH3
H
"N-N
R R
+
R R
CH3
9
10
CH3
11
a, R = Me; b, R = P h
Scheme 1.
2.94 (s, NCH,), 1.72 (s, CH,)] and I3C-NMR spectra indicate that the [4+2]-cycloadduct 3a is formed initially.
At - 10°C 3a rearranged to afford isomers 4a and 7a.
In the final stages of the reaction only signals corresponding to 2a, 5a, 6a, and l a could be observed. Similarly, the
reaction between l b and MTAD at -78°C furnished 3b,
which rearranged at - 10°C to furnish 2b.
In preliminary investigations of the mechanism (concerted, diradical, or zwitterionic), remarkably low-energy
barriers for the conversion 3b-4b (AH' = 2 I .7 f.2 kcal/
mol, AS+=6.5&.6 cal/mol K in [D,]THF) were estimated. Evidence for a true intermediate on the potential
energy surface was provided by performing the cycloaddition reaction between l b and MTAD in CH2CI,/MeOH
( I : 5 ) at -45 "C. NMR spectroscopy (at -45°C) indicates
the initial formation of 3b ; however, warming the solution
to room temperature results in the formation of the metha-
0 Verlag Chemie GmbH. 6940 Weinheim. 1982
0570-0833/82/0505-0383 .$02.50/0
383
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monoformylmethides, sensitized, benzoquinone, photooxygenation, cis, methoxystyrenes
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