Photochemistry of Diaryl Vicinal Tetraketones and Chemistry of Intermediate (Aroyloxy)arylketenes

Article abstract of DOI:10.1021/jo971247q

Photolysis of diaryl vic-tetraketones results in formation of tricyclic-γ-lactones 3 and 4 with low quantum but high chemical yield. (Aroyloxy)arylketenes and carbon monoxide are the initial photochemical products of these photolyses. Subsequent reaction of ketene with ground-state tetraketone results in formation of the observed photoproducts via intermediate β-lactones. The latter are formed with a high degree of stereoselectivity. The failure of a cyclic tetraketone to react is attributed to its inability to undergo the cyclic mechanism proposed for formation of ketenes from tetraketones. Dimesityl and di-tert-butyl tetraketones react by a competing intramolecular hydrogen atom transfer mechanism. Dimerization of (benzoyloxy)phenylketene and its reactions with a number of tetraketones are described.

Full text of DOI:10.1021/jo971247q

480
J . Org. Chem. 1998, 63, 480-488
P h otoch em istr y of Dia r yl Vicin a l Tetr a k eton es a n d Ch em istr y of
In ter m ed ia te (Ar oyloxy)a r ylk eten es1
Mordecai B. Rubin,*,† Marina Etinger,† Moshe Kapon,† Eric C. Krochmal J r.,†
Raisa Monosov,† Stephan Wierlacher,‡,§ and Wolfram Sander‡,§
Department of Chemistry, Technion - Israel Institute of Technology, Haifa, Israel and Institute fu¨r
Organische Chemie, Hagenring 30, D-3300 Braunschweig, Germany
Received J uly 9, 1997
Photolysis of diaryl vic-tetraketones results in formation of tricyclic-γ-lactones 3 and 4 with low
quantum but high chemical yield. (Aroyloxy)arylketenes and carbon monoxide are the initial
photochemical products of these photolyses. Subsequent reaction of ketene with ground-state
tetraketone results in formation of the observed photoproducts via intermediate â-lactones. The
latter are formed with a high degree of stereoselectivity. The failure of a cyclic tetraketone to
react is attributed to its inability to undergo the cyclic mechanism proposed for formation of ketenes
from tetraketones. Dimesityl and di-tert-butyl tetraketones react by a competing intramolecular
hydrogen atom transfer mechanism. Dimerization of (benzoyloxy)phenylketene and its reactions
with a number of tetraketones are described.
In tr od u ction
in air results in rapid replacement of the red color of
tetraketone by the pale yellow of the hydrate. Tetrake-
tones containing bulky end groups such as mesityl or tert-
butyl or cyclic tetraketone 211 are hydrated to a much
lesser extent. Traces of hydrate are not a major problem
in preparative photochemical experiments since ap-
propriate filters can ensure that only the free tetrone
absorbs light, but extreme dryness is a must for quantum
yield or other quantitative measurements. The special
drying techniques developed for working with these
compounds in solution are described in the Experimental
Section. The use of protic solvents such as alcohols is
precluded for most tetraketones.
R-Diketones have a rich photochemistry which has
been studied extensively.2 Very different photochemistry
of vic-triketones which is characterized by extremely low
quantum yields and formation of complex product mix-
tures has recently been reported.,3,4 Although open-chain
vic-tetraketones were first prepared,5,6 in 1891, their
photochemical reactions have not been reported. The
present paper describes the delightful photochemistry
(Scheme 1) of some such compounds (1a -c) involving
reasonable reactivity and high chemical yields.
Absorption spectra of vic-tetraketones have been stud-
ied in detail by Horner and co-workers.7 Typical is
diphenyl tetraketone (1a , 1,4-diphenylbutane-1,2,3,4-
tetrone) with UV-vis maxima at 262 (18000), 385 (160),
and 515 (200) nm; long wavelength maxima for related
tetraketones (1a -e, 5a ) lie in the range 510-525 nm.
Our attempts and those of others8 to observe light
emission from tetraketones failed to detect either fluo-
rescence or phosphorescence. Structures of 1a and 1d
have been determined by X-ray crystallography.9
P h otolysis Resu lts
Preparative scale irradiations of tetraketones were
performed in dry benzene solutions under nitrogen or
argon using a sodium chromate solution filter to ensure
irradiation above 500 nm so that reaction product(s)
would not undergo further photochemistry. Steady
evolution of bubbles was observed during irradiation; the
evolved gas was shown to be carbon monoxide by exami-
nation of the headspace after the reaction. Bubble
formation ceased and the red solution became yellow
when the reaction was complete. Dimesityl (1d ) and di-
It should be emphasized that most vic-tetraketones
undergo hydration extremely rapidly.10 Simple standing
† Israel Institute of Technology.
tert-butyl (1e) tetraketones, and cyclic tetraketone12
2
‡ Institute fu¨r Organische Chemie.
§ Present address: Lehrstuhl fu¨r Organische Chemie, Ruhr Uni-
versita¨t, D-44780 Bochum, Germany.
were recovered unchanged under these irradiation condi-
tions.
TLC analysis of crude products from 1a -c showed one
major spot and indications of a second, minor, spot of very
similar Rf value. Crude reaction products were washed
(1) A prelimnary report of part of this work has appeared. Rubin,
M. B.; Krochmal, E. C., J r.; Kaftory, M. Rec. Trav. Chim. 1979, 98,
85. Taken in part from the M.Sc. thesis of M. Etinger, Technion, 1995.
(2) For reviews see Rubin, M. B. Top. Curr. Chem. 1969, 13, 251.
Monroe, B. M. Adv. in Photochem. 1971, 8, 77. Rubin, M. B. Top. Curr.
Chem. 1985, 129, 1.
(3) Netto-Ferreira, J . C.; Scaiano, J . C. Photochem. Photobiol. 1991,
54, 17.
(4) Rubin, M. B.; Heller, M.; Monisov, R.; Gleiter, R.; Do¨rner, T. J
Photochem. Photobiol. A: Chem. 1995, 87, 7.
(5) Abenius, P. W.; Soderbaum, H. G. Ber. 1891, 24, 3033.
(6) For a general review of the chemistry of vicinal polyketones see
Rubin, M. B. Chem. Rev. 1975, 75, 177.
(7) Horner, L.; Maurer, F. Ann. 1970, 736, 145. Idem. Chem. Ber.
1968, 101, 1783.
(9) Diphenyl tetraketone: Beddoes, R. L.; Cannon, J . R.; Heller M.;
Mills, O. S.; Patrick, V. A.; Rubin, M. B.; White, A. H. Aust. J . Chem.
1982, 35, 543. Dimesityl tetraketone: Kaftory, M.; Rubin, M. B. J .
Chem. Soc., Perkin Trans. 2 1983, 149.
(10) The equlibrium constant for hydration of 1a to its monohydrate
in dioxane containing traces of water at 25 °C has been determined to
be on the order of 1000, M. Heller, M. Sc. thesis, Technion.
(11) Gleiter, R.; Kramer, R.; Irngartinger, H.; Bissinger, C. J . Org.
Chem. 1992, 57, 252.
(8) Fischer, E. (deceased), Weizmann Institute, personal com-
munication.
(12) Kramer, R., Technion, unpublished results.
S0022-3263(97)01247-4 CCC: $15.00 © 1998 American Chemical Society
Published on Web 01/22/1998

Photochemistry of Diaryl Vicinal Tetraketones
J . Org. Chem., Vol. 63, No. 3, 1998 481
Sch em e 1
Ta ble 1. Qu a n tu m Yield s for Disa p p ea r a n ce of
Tetr a k eton es a t 546 n m in Tolu en e Solu tion
rapidly through short columns of neutral alumina or
chromatographed carefully on silica gel columns. Slow
decomposition occurred on both types of columns as
indicated by loss of material. Crystallization of alumina
washings from di-p-bromo (1b) and di-p-anisyl (1c)
tetraketones gave pure, yellow crystalline products (3b
74%, 3c 82%). The product from 1b was shown to be
the tricyclic lactone 3b, a very unexpected result, by
X-ray crystallographic analysis.13 The structure includes
R-diketone, γ-lactone, and ortho ester moieties in a rigid
molecule derived from two flexible open-chain tetrake-
tones with loss of one molecule of carbon monoxide. Prior
to the X-ray structure determination, we had explored a
number of reductive degradation procedures with no
success, a result which is not surprising in view of the
sensitive functional groups present. Considerable spec-
troscopic data (see Experimental Section) in the UV-
concn
anthracene
TK (1)
(M × 103)
(M × 102)
Φ546
a
a
a
a
b
b
c
3.4
3.6
3.4
2.7
2.1
1.8
3.1
-
0.016
0.015
0.015
0.014
0.022
0.021
0.013
1.8
3.4
5.3
-
1.8
-
noted above, TLC analysis of crude reaction products
showed major and minor spots of very similar Rf value,
and these were assigned to 3a and 4a , respectively.
Products analogous to 4a may be formed to a minor
extent in photolyses of other tetraketones.
Photolysis of the unsymmetrical compound, p-anisyl
tert-butyl tetraketone (5a ), was also investigated.
1
vis, IR, H and 13C NMR were diagnostic of the tricylic
A
priori, four different tricyclic lactones analogous to
compounds 3 and four of type 4 could be formed in this
reaction. In the event, we were able to isolate only one
pure product in 20% yield. This yellow compound 5b
exhibited the expected diketone and γ-lactone absorptions
but no anisoyl absorption. It is tentatively assigned
structure 5b on the basis of its spectroscopic properties.
Since 80% of the reaction remains unknown, it is not
possible to draw any conclusions regarding preferred
modes of reaction from this result.
Quantum yield data for disappearance of tetraketones
upon irradiation at 546 nm, calculated from the decrease
in the long wavelength maximum, are summarized in
Table 1. We note that the values for the three compounds
measured are nearly identical even for bromine-contain-
ing 1b. Quantum yields for reaction of 1a were inde-
pendent of light intensity over the range 1.7-5.4 × 10-6
einstein/min14 and of tetraketone concentration over the
range 1.2-5.2 × 10-3 M. The quantum yield for disap-
system present and served to establish the structures of
compounds of this type. The product from 1c exhibited
four O-methyl resonances in the 1H NMR spectrum,
consistent with the presence of four different aryl groups.
We note the γ-lactone band in the IR at 1810-1820 cm-1
in all cases. Electron impact mass spectra generally did
not show the molecular ion; the most intense m/z peak
corresponded to loss of carbon monoxide or carbon
dioxide.
Silica gel chromatography of the photoproduct from 1a
afforded the expected yellow 3a (63%) and a second,
colorless product 4a (6%). The structure 3a was assigned
on the basis of spectroscopic properties as discussed
above. Isomeric 4a was a colorless compound lacking the
second carbonyl group of an R-diketone moiety, but
showing the appropriate spectrosocopic data for γ-lactone
and ortho ester moieties. The presence of two benzoyl
groups was inferred from the enhanced extinction coef-
ficient (20000) at 260 nm and from the 13C NMR. As
(13) Kaftory, M. Acta Crystallogr. 1979, B35, 1717.
(14) Total light intensity on a 0.9 × 2.7 cm area of the cell.

482 J . Org. Chem., Vol. 63, No. 3, 1998
Rubin et al.
Sch em e 2
pearance of 1a at 366 nm was 0.08. The results obtained
in the presence of added anthracene (ET 42 kcal/mol15)
show that this potential triplet quencher has no effect
on quantum yield, suggesting that reaction proceeds from
the first excited singlet state of 1a . In the absence of
information on the triplet energy of tetraketones, this
conclusion must be regarded as tentative. It is, however,
supported by the observation that quantum yields were
identical in the presence or absence of oxygen.
The failure of 1d to undergo photochemical change
could be due to a competing reaction, intramolecular
abstraction of a hydrogen atom from an o-methyl group.
This process is well-known with o-alkyl-substituted ben-
zophenones16 and has also been shown to occur with
analogous R-diketones.17 This behavior could be dem-
onstrated by irradiation of a solution of 1d in toluene
containing tert-butyl-OD and recovery of the “unreacted”
starting material. The recovered tetraketone had incor-
porated a significant amount of deuterium in an o-methyl
group, as shown by NMR and MS analysis. This is
suggested to occur via H-atom abstraction to form
biradical 6.18 Exchange with tert-butyl-OD can occur
with 6 or with the subsequently formed enol 7; in either
case, ketonization will regenerate tetraketone incorporat-
ing a deuterium atom. A similar explanation or steric
effects of the tert-butyl groups could be possible for the
failure of 1e to undergo photochemical change.
Mech a n ism
We have found a single example in the literature of
the tricyclic lactone skeleton present in the tetraketone
photoproducts. In 1982 Dominguez and Cava19 (Scheme
2) reported that reaction of biacetyl with phenylacetox-
yketene (8a ), generated in situ by reaction of R-phenyl-
R-acetoxyacetyl chloride (9a ) with triethylamine, gave
crystalline â-lactone 10a (1840 cm-1) in 30% yield (not
optimized). Heating 10a above its melting point, or
distillation of crude reaction product from the reaction
of biacetyl with 8a , afforded a single crystalline substance
in high yield. This was assigned structure 12a on the
basis of analytical data and spectroscopic properties; it
incorporates the lactone ortho ester features of our
tetraketone photoproducts. The mechanism suggested
by Cava (Scheme 2) involves initial cycloaddition between
ketene and one of the carbonyl groups of biacetyl. Two
isomeric â-lactones, 10a and 11a , are possible from such
a cycloaddition. In 10a , where acetyl and acetoxyl groups
are in a cis-relationship, rearrangement to γ-lactone 12a
can occur as illustrated. The preferential formation of
10a having this required cis relationship was attributed
to secondary orbital interactions. Isomeric 11a , in which
acetyl and acetoxyl groups are trans, would rearrange
without involvement of the acetyl group to bicyclic lactone
13 possessing an intact acetyl group; this was not
observed. We had no difficulty in repeating Dominguez
and Cava’s results and also found that an analogous
reaction of (benzoyloxy)phenylketene (8b), prepared from
the corresponding acid chloride, with biacetyl gave
tricyclic lactone 12b, isolated in 54% yield after chroma-
tography on silica gel.
(15) Evans, D. J . Chem. Soc. 1957, 1351. Lewis, G. N.; Kasha, M.
J . Am. Chem. Soc. 1944, 66, 2100.
(16) Sammes, P. G. Tetrahedron, 1976, 32, 405. For
a recent
reference see Hopf, H.; Laue, T.; Zander, M. Angew. Chem., Intl. Ed.
Engl. 1991, 30, 432.
(17) For a summary see Rubin, M. B. Top. Curr. Chem. 1985, 129,
1.
(18) The initial H-atom abstraction need not be by the carbonyl
group adjacent to the aromatic ring since there will be a rapid
equilibrium between ketyl radicals.
(19) Dominguez, F.; Cava, M. P. Tetrahedron Lett. 1982, 5513.

Photochemistry of Diaryl Vicinal Tetraketones
J . Org. Chem., Vol. 63, No. 3, 1998 483
The Cava mechanism described above can also apply
to the reaction of ketenes with tetraketones. Addition
of 8b to tetraketone would be expected to occur at one of
the more reactive6 central carbonyl groups of 1 and could
produce two stereoisomeric â-lactones 14 and 15. In 14,
benzoyl and benzoyloxy groups are in the cis relationship;
the product of rearrangement to γ-lactone should be
identical with the major product 3a of photolysis of
tetraketones. Isomeric 15 has a phenylglyoxyl moiety cis
to benzoyloxy; the product of its rearrangement would
then have the structure of the minor photoproduct 4a .
Gratifyingly, reaction of 8b with 1a indeed produced two
products identical with 3a and 4a in yields similar to
those obtained in the photolysis reaction; the ratio 3a :
4a was 10:1. Similar reaction of (anisoyloxy)anisylketene
(8c) with tetraketone 1c gave photoproduct 3c in 85%
yield, and no isomeric product was isolated in this case.
Further reactions of 8b are described later in this report.
These results clearly establish that reactions of ap-
propriate ketenes with tetraketones yield the same
products as do photoreactions of tetraketones. They do
not prove that ketenes are formed photochemically from
tetraketones and are intermediates in the photoreactions,
only that if ketenes were formed, they would react
thermally to give the observed products. Attempted
trapping of a ketene intermediate by irradiation of
solutions of 1a containing added cyclopentene, benzhy-
drol, diphenyl triketone, or biacetyl resulted in formation
of 3a and 4a alone. Preliminary evidence supporting the
intermediacy of ketenes was obtained when the reaction
of 1a was performed at low temperatures in toluene
solution in a UV cell. In a narrow range of temperature,
F igu r e 1. Argon matrix IR difference spectrum (product
bands upward) showing the photochemistry of 1a upon ir-
radiation at 10 K with λ g 360 nm. Bands labeled A are
assigned to ketene 8b.
feasible. It is interesting to compare the formation of 8b
from 1a with the photochemical reaction of cis-diben-
zoylethylene (18) which also has terminal benzoyl groups
as part of a four-carbon chain. In this case, phenyl
migration from the singlet state is observed to give a
ketene20 as illustrated. However, if a similar phenyl
migration occurred in the case of tetraketones (cf. Scheme
3), the products would be two molecules of CO or the
elusive ethylenedione21 and phenoxyphenylketene. The
latter is not consistent with the observed results; the
difference in behavior could be due to differing geometries
of excited states.
An alternative mechanism for photochemical formation
of 8b involves initial R-cleavage of tetraketone (Scheme
3). This would produce either a pair of phenylglyoxyl
radicals 19 or a benzoyl radical plus triketo radical 20.
Facile decarbonylation of 19 or 20 would produce22
benzoyl and phenylglyoxyl radicals, possibly still in the
original solvent cage. Subsequent coupling of these two
radicals could lead to 8b. However, it seems likely that
such a coupling should also produce photochemically
inert3 diphenyl triketone (21). Triketones have not been
observed in any tetraketone photolysis. Further, benzil
might be expected to be formed by coupling of benzoyl
radicals, but none could be detected even though benzil
does not react (v.i.) with 8b . We note that analogous
R-cleavage is not observed2 with vic-di- or triketones.
The failure to obtain products analogous to 4a in other
photolyses and in some of the thermal reactions of 8b
with tetraketones may be the result of failure of chro-
matographic separation, particularly in view of the
lability of the tricyclic lactones on silica gel or alumina
columns. The only other case in which a significant
amount of product analogous to 4 was formed was the
reaction of 8b with 1d where steric factors may be
involved. The ratio 3d :4d was unity in this case.
approximately -80 to -100 °C, a new absorption (λmax
∼
510 nm) appeared. At lower temperatures, the photore-
action was very slow and at higher temperatures the new
absorption disappeared rapidly and was difficult to
observe. Unfortunately, it was not possible to achieve a
high degree of conversion because spectra of 1a and the
new intermediate overlapped, and the new intermediate
underwent further photochemical reaction. Similar spec-
troscopic behavior with a maximum at the same wave-
length was observed when triethylamine was added to a
solution of ketene precursor in toluene at -80 °C.
Definitive results were obtained in Braunschweig by
irradiation of 1a in an argon matrix at 10 K. The
difference IR spectrum from irradiation at λ g 360 nm
is shown in Figure 1. It exhibits a shoulder at 2135 cm-1
,
assigned to CO, and strong absorptions at 2128 (100, rel
intensity), 1771 (45), 1266 (35), 1240 (90), 1237 (56), 1026,
and 709 (64) cm-1, assigned to ketene 8b formed by
photochemical reaction of tetraketone. On irradiation at
shorter wavelengths (λ g 330 nm), the bands for 8b
disappeared and new absorptions at 1678, 1311, 1214,
1178, 944, 922, 702, 647, and 640 cm-1 grew in, consistent
with the results observed in toluene solution at -80 °C.
Simultaneously with the decay of 8b, larger amounts of
CO and CO2 were formed.
If the photochemical reaction of tetraketones proceeds
from a singlet state as suggested earlier, the formation
of (benzoyloxy)phenylketene from such a singlet could be
a concerted, cyclic process as illustrated (Scheme 3).
Alternative stepwise mechanisms involving biradical 16
or zwitterionic intermediates such as 17 are also possible
and would be required from the triplet state. The failure
of cyclic tetraketone 2 to react photochemically is pre-
sumably due to the fact that a cyclic mechanism is not
(20) Griffin, G. W.; O’Connell, E. J . J . Am. Chem. Soc. 1962, 84,
4148. Zimmerman, H. E.; Durr, H. G. C.; Lewis, R. G.; Bram, S. Ibid.
1962, 84, 4149. Barik, R.; Bhatttacharya, K.; Das, P. K.; George, M.
V. J . Org. Chem. 1986, 51, 3420 and references therein.
(21) Rubin, M. B.; Patyk, A.; Sander, W. Tetrahedron Lett. 1988,
29, 6641.
(22) These radicals might be close to one another in a solvent cage.

484 J . Org. Chem., Vol. 63, No. 3, 1998
Rubin et al.
Sch em e 3
Sch em e 4
We have previously reported3 single electron transfer
(SET) when diphenyl triketone was irradiated in the
presence of DABCO or p-dimethoxybenzene. Rates of
photolysis were enhanced in the presence of these
electron donors and exclusive formation of benzil was
observed. Attempts to observe similar SET with 1a were
not successful. The photochemical reaction in the pres-
ence of dimethoxybenzene produced the same products
as observed in its absence. A similar experiment with
DABCO was precluded by the observation of decomposi-
tion of 1a in the presence of DABCO, and no identifiable
products were obtained.
Ad d ition a l Rea ction s of Keten e 8b
It appeared of interest to examine additional reactions
of the novel type of ketene23 obtained in the present work.
To our knowledge, such compounds have not been
described previously except for the preliminary report of
Dominguez and Cava describing acetoxyphenylketene. In
all cases, 8b or 8c was generated by reaction of equimolar
amounts of the appropriate acid chloride with triethy-
lamine in benzene solution at room temperature.
the Supporting Information.24 This product may have
resulted from rearrangement of an initially formed
â-lactone such as that illustrated (or a stereoisomer).
Intermediacy of 1,3-cyclobutanediones, often formed in
dimerization of disubstituted ketenes, does not seem
reasonable. A noncrystalline dimer, 22b, was obtained
from 8c, and spectroscopic properties suggest that its
structure is analogous to that of 22a . We note that
Dominguez and Cava obtained an intractable gum from
attempted dimerizaton of acetoxyphenylketene under
similar conditions. The dimerization of 8b limits the
possibility of observing its products of reaction in some
cases and provides an internal “clock” which allows
qualitative comparison of rates of reaction of various
compounds with the ketene. The much greater reactivity
of tetraketones is evidenced by the fact that dimeric
products were not observed in any of the reactions with
tetraketones in contrast to the results with other com-
pounds as discussed below. Also, tetraketone photolyses
in the presence of added di- or triketones yielded only
the tetraketone photoproducts.
A. Dim er iza tion . Generation of 8b in benzene or
toluene at room-temperature resulted in appearance of
a red color (λmax 510 nm) and separation of crystalline
amine hydrochloride. After 3 h at room temperature, the
color had faded to pale yellow, and workup provided a
white solid, mp 116-117 °C, in 74% yield. A higher
melting form (mp 144-145 °C) was obtained upon
recrystallization. Both products had identical solution
spectra. The structure of the higher melting form was
established as 22a , a dimer of starting ketene (Scheme
4), by X-ray crystallographic analysis; the ORTEP dia-
gram of 22a together with selected bond lengths and
angles are shown in Figure 2, and details of the structure
analysis are provided in the Experimental Section and
(23) For summaries of ketene chemistry see: Borrman, D. Methoden
der Organsichen Chemie (Houben-Weyl), 4th ed.; Georg Thieme Verlag:
Stuttgart, 1968; vol VII/4. Tidwell, T. Ketenes; Wiley: Chichester,
1995.
(24) M. Kapon has deposited atomic coordinates for this structure
with the Cambridge Crystallographic Data Centre. The coordinates
can be obtained, on request, from the Director, Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, UK.

Photochemistry of Diaryl Vicinal Tetraketones
J . Org. Chem., Vol. 63, No. 3, 1998 485
Sch em e 5
â-lactone could be observed in the reaction of 1d with
8b. The crude reaction product had infrared absorption
at 1820 cm-1 and consisted of a 1:1 mixture of γ-lactones
25d and 26d which could be separated by crystallization.
F igu r e 2. ORTEP diagram of 22a , the dimer of ketene 8b.
Hydrogen atoms are omitted for clarity. Bond lengths (Å):
O(1)-C(2) 1.379(3), O(1)-C(6) 1.437(3), C(2)-O(3) 1.202(3),
C(2)-C(4) 1.469(4), C(4)-C(5) 1.317(4), C(5)-O(28) 1.376(3),
C(5)-C(6) 1.501(4), C(6)-O(7)1.423(3). Selected bond angles
(deg): C(2)-O(1)-C(6) 109.0(2), O(3)-C(2)-O(1) 119.5, O(3)-
C(2)-C(4) 130.6(3), O(1)-C(2)-C(4) 109.9(3), C(5)-C(4)-C(2)
105.5, C(4)-C(5)-O(28) 131.2(3), C(4)-C(5)-C(6) 112.8(3),
O(28)-C(5)-C(6) 116.0(2), O(7)-C(6)-O(1) 109.1(2), O(7)-
C(6)-C(5) 114.3(2), C(5)-C(6)-O(1) 102.6(2).
Exp er im en ta l Section
Melting points are uncorrected. Combustion analyses were
performed by the Microanalytical Laboratory, Hebrew Uni-
versity, J erusalem. 1H NMR spectra were determined at 200
MHz in CDCl3 and 13C spectra at 100 MHz in CDCl3 unless
specified otherwise and are expressed in ppm from tetram-
ethylsilane. Infrared spectra were determined with a Nicolet
Impact 400 FT spectrometer using KBr pellets for solids and
neat or in chloroform solution for noncrystalline materials. A
Hewlett-Packard diode array instrument was used for UV-
vis spectra. High-resolution mass spectra were measured with
a Varian MAT-711 at 70 eV unless noted otherwise and low
resolution spectra with a Finnigan TSQ 70.
Ir r a d ia tion s. Irradiations were performed in Pyrex vessels
using a 200 W high-pressure mercury lamp (Osram HBO 200)
in a Wild housing or a 900 W xenon lamp (Osram XBO-900)
in a Schoeffel housing. A Schott interference filter was used
to isolate the 546 nm mercury line. For preparative irradia-
tions, analytical grade benzene was boiled briefly before use
to ensure dryness, and solutions were bubbled with argon or
nitrogen for 30 min before closing and starting irradiation. An
18 mm layer of 10% aqueous potassium chromate between the
light source and the sample eliminated light of wavelength
shorter than 500 nm. Quantum yields at 546 nm were
determined in square Pyrex cells (light path 10 mm). Dry
solutions of tetraketone in toluene were prepared by the
procedure described below. Light intensities incident on a 9
× 27 mm area of the cell were on the order of 1 × 10-6 einstein/
min. The actinometer was the colored form of Aberchrom
540.25
Sa m p le P r ep a r a tion . The extremely anhydrous condi-
tions required for quantitative measurements with tetrake-
tones were achieved by the use of the apparatus shown in
Figure 3, consisting of a 10 mm square Pyrex cell fused to a
length of tubing with a constriction (for sealing off) and a
standard taper joint. This was connected to a tube with a
coarse fritted disk which in turn connected via a standard
taper joint to a 10 mL round-bottomed flask containing a
magnetic stirring bar. The appropriate amount of tetraketone,
carefully dried solvent, and phosphorus pentoxide (10-15 mg)
were introduced into the flask, the apparatus was connected,
and the flask was stirred for about 15 min. The flask was
then inverted and the cell cooled in dry ice-acetone mixture
so that the liquid flowed through the frit into the cell. The
absorption spectrum was measured after warming to room
temp, the apparatus inverted, and the round-bottom flask
cooled so that the liquid flowed into it. The process was then
B. Rea ction of 8b w ith Mon ok eton es a n d r-Dik e-
ton es. Only dimer formation was observed when 8b was
generated in the presence of excess acetone or acetophe-
none. As noted earlier, 8b reacted readily with biacetyl
to give the tricyclic lactone 12b. However, in contrast
to the reaction of 8a with biacetyl, where intermediate
â-lactone could be isolated by trituration of crude reaction
product, no crystalline â-lactone could be obtained from
reaction of 8b. Benzil, in contrast to biacetyl, was
unreactive with 8b affording recovered benzil, a trace of
benzoin benzoate, and the dimer 22a . Dominguez and
Cava reported a failure to observe a product from reaction
of benzil with acetoxyphenylketene. These results suport
the view that reaction of ketenes with tetraketones occurs
at a central, more reactive carbonyl group. Reaction with
9,10-phenanthrenequinone (PQ) was also investigated.
A labile, crystalline product was obtained in crude yield
of 81%. It is tentatively assigned structure 23 on the
basis of its spectroscopic properties.
C. Rea ction w ith Tetr a k eton es. In addition to the
reactions of 8b with 1a and of 8c with 1c described
earlier in connection with the mechanism of photolysis,
reactions of 8b with 1d -f were also investigated. In two
cases (1e,f), trituration of the crude reaction product
afforded a crystalline yellow solid in about 50% yield
(Scheme 5). Both of these products (24e,f) showed
infrared maxima at about 1840 cm-1 characteristic of
â-lactones. Each â-lactone rearranged in chloroform
solution at room temperature to a single, yellow γ-lactone
(25e,f) whose structure was assigned as shown on the
basis of spectroscopic properties and mechanism. The
results observed with anisyl tert-butyl tetraketone (1f)
suggest that initial addition of ketone occurs at the
central carbonyl group furthest from the tert-butyl group.
In addition, a low yield of an isomeric product having
two monoketone functions instead of the R-diketone
group was obtained. The stereochemistry of the â-lac-
tones is assigned as shown on mechanistic grounds as
discussed above. Minor products in these reactions were
the isomeric γ-lactones 26e and 26f. In contrast, no
(25) Kuhn, H. J .; Braslavsky, S. E.; Schmidt, R. Pure Appl. Chem.
1989, 61, 198. Cf also Wintgens, V.; J ohnston, L. J .; Scaiano, J . C. J .
Am. Chem. Soc. 1988, 110, 511.

486 J . Org. Chem., Vol. 63, No. 3, 1998
Rubin et al.
125.22, 126.06, 126.63, 126.93, 128.24, 128.70, 128.81, 129.04,
129.88, 129.96, 131.27, 132.12, 132.28, 132.42, 132.61, 167.37,
187.02 ppm. UV (CH3CN) 230 (42800), 302 (7100) nm. MS,
CI (isobutane), 872, 874, 876, 878, 880 (relative intensities 1:4:
6:4:1). Anal. Calcd for C31H16O7Br4: C, 45.40, H, 1.97, Br,
38.97. Found: C, 45.18, H, 2.23, Br, 38.77.
P h otolysis of Di-p-a n isyl Tetr a k eton e (1c). A solution
of 1c (20 g) in dry benzene (300 mL) was irradiated under
nitrogen with the 900 W lamp for 70 h when the characteristic
red color of starting material had disappeared. Evolution of
bubbles of gas occurred throughout the irradiation. The yellow
solution was concentrated in vacuo, a small sample withdrawn
for spectroscopic analysis, and the remainder washed through
neutral alumina (48 g) with methylene chloride (350 mL).
Removal of solvent gave material (13.4 g, 74%) which crystal-
lized on standing; crystallization from methylene chloride-
hexane gave pure 3c (11.3 g), mp 145.5-146.5 °C. Spectra
(IR, NMR) of crude product and pure 3c were very similar.
The analytical sample of 3c was prepared by further crystal-
lization from methylene chloride-hexane, mp 146-7 °C. IR,
1811, 1728, 1648, 1616, 1592 cm-1 1H NMR, 3.66 (s, 3H), 3.74
.
(s, 3H), 3.80 (s, 3H), 3.86 (s, 3H), 6.66 (d, J ) 6.4 Hz, 2H),
6.72 (d, J ) 6.4 Hz, 2H), 6.84 (d, J ) 8 Hz, 2H), 7.02 (d, J )8
Hz, 2H), 7.28 (d, J ) 8 Hz, 2H), 7.45 (d, J ) 8 Hz, 2H), 7.65
(d, J ) 8 Hz, 2H), 7.88 (d, J ) 8 Hz) ppm. 13C NMR, 55.13,
55.39, 55.55, 82.82, 99.51, 106.21, 113.70, 113.90, 120.13,
121.55, 121.89, 123.17, 123.50, 128.31, 128.50, 129.46, 132.53,
160.47, 161.03, 161.93, 165.17, 168.66, 186.04, 186.86 ppm.
F igu r e 3. Apparatus for obtaining dry solutions of tetrake-
tones.
UV (CH3CN) 328 nm (10000) nm. Anal. Calcd for C35H28O11
C, 67.30, H, 4.26. Found: C, 67.50, H, 4.32.
:
repeated until the spectrum of the filtered solution remained
unchanged after further contact with phosphorus pentoxide.
The apparatus was rapidly disassembled and the cell im-
mediately closed or connected to a vacuum line, cooled, and
sealed off. Freeze-pump-thaw degassing could be performed
at this stage. The absorption spectrum of cells stored in the
dark was measured at 1 day intervals, and only cells whose
absorption spectrum remained unchanged were used for
further work.
P h otolysis of ter t-Bu tyl p-An isyl Tetr a k eton e (5a ). A
solution of 5a (0.011 mol) in benzene (80 mL) was irradiated
with light from the 900 W lamp until complete disappearance
of the long wavelength maximum at 518 nm. The oil obtained
after evaporation of solvent was chromatographed on silica gel
with hexanes-ethyl acetate (20:1) to give yellow crystalline
5b (0.26 g, 20%), mp 165-167 °C. IR, 1810, 1740, 1715, 1700,
1615 cm-1 1H NMR, 0.66 (s, 9H), 1.38 (s, 9H), 3.75 (s, 3H),
.
P h otolysis of Dip h en yl Tetr a k eton e (1a ). A degassed
solution of 1a (0.69 g, 0.0023 mol) in benzene (10 mL) was
irradiated for 48 h with light from the 200 W mercury lamp
filtered through an 18 mm layer of 10% aqueous potassium
chromate. Bubbles of gas evolved during this time, and the
red color faded to pale yellow. A commercial carbon monoxide
detector gave a positive test in the headspace of the cell. After
removal of solvent, the residue was chromatographed on silica
gel (35 g), eluting with hexanes-ethyl acetate (50:1) to give
two crystalline products: 3a (0.37 g, 63%) and 4a (0.034 g,
6%).
3.76 (s, 3H), 6.84 (d,d, J ) 8 Hz, J ) 8 Hz, 4H), 7.34 (d, J )
8 Hz, 2H), 7.46 (d, J ) 8 Hz, 2H) ppm. 13C NMR, 24.89, 24.98,
34.33, 42.07, 55.23, 55.35, 81.82, 99.32, 106.03, 113.58, 113.73,
113.91. 121.92, 123.74, 126.86, 128.11, 129.29, 160.32, 161.02,
169.11, 202.39 ppm. UV, 236 (25000), 268 (2000), 420 (24)
nm. Anal. Calcd for C29H32O9: m/z 524.2046, C, 66.40; H,
6.15. Found: C, 66.77, H, 6.24, m/z 524.2081.
Ir r a d ia tion of Dim esityl Tetr a k eton e (1d ). A. In
Tolu en e Solu tion . A solution of 1d in approximately 3 mL
of toluene in a cuvette was irradiated for 16 h with the 200 W
lamp. The absorbance at 512 nm decreased from 1.30 to 1.28.
B. In Tolu en e Solu tion Con ta in in g t-Bu OD. A solution
of tetraketone (10.6 mg) in toluene (3.5 mL) was dried over
P2O5 in the standard manner in a Pyrex cell fitted with a
standard taper joint. The cell was immediately connected to
the vacuum line, tert-butyl alcohol-OD (0.37 g) distilled in, and
the cell sealed off. The absorbance at 512 nm after sealing
was 1.285. The solution was irradiated with the 200 W lamp
for 16 h under the usual conditions. Final absorbance was
0.9 at 512 nm. The cell was opened, and solvents were
evaporated. Determination of the proton-decoupled 13C NMR
spectrum of a sample showed a triplet centered at 20.44 ppm
with couplings of 27 and 32 Hz which is assigned to the CH2D
group replacing an o-CH3 group (20.35 ppm) in the mesityl
moiety. A second sample was subjected to mass spectroscopic
analysis. The ratio of the mesitoyl peaks at m/z 147 and 148
was 4.7:1 in the irradiated sample as compared to 8.5:1 in the
starting material.
The major product, 3a , was a yellow solid, mp 93-95 °C.
IR, 1820, 1733, 1662 cm-1
.
13C NMR, 83.19, 99.60, 106.48,
122.19, 126.92, 126.98, 127.87, 128.02, 128.41, 128.56, 128.69,
129.32; 129.84, 130.39, 130.53, 131.05, 131.66, 135.21, 168.23,
187.70 ppm. UV (CH3CN), 268 (6800), 280 (6600), 398 (50) nm.
MS, m/z 460.1311; calcd for C30H20O5 (M - CO2) 460.1314.
Anal. Calcd for C31H20O7: C, 73.80, H, 4.00. Found: C, 73.65;
H, 4.21.
The minor product, 4a , was a white solid, mp 172-174 °C,
IR, 1824, 1686, 1667 cm-1
.
13C NMR 83.70, 97.96, 108. 61;
123.53; 126.99, 127.66, 127.90, 128.19, 128.44, 128.72, 129.20,
129.75, 130.78, 131.48, 131.81, 133.75, 135.03, 135.54, 167.99;
185.44, 191.23 ppm. UV (CH3CN), 260 (22000) nm. MS, m/z
476.1266, calcd for C30H20O6 (M-CO) 476.1259. Anal. Calcd
for C31H20O7: C, 73.80, H, 4.00. Found: C, 73.40, H, 4.06.
P h otolysis of Di-p-br om op h en yl Tetr a k eton e (1b). Dry
benzene (ca 50 mL) was distilled on the vacuum line into a
cylindrical vessel containing tetraketone (7.0 g) and the
solution irradiated with the 900 W lamp until gas evolution
ceased and the color faded to pale yellow. Evaporation of
solvent gave crude product (6.90 g) which afforded 3b (5.26 g,
82%) after washing rapidly through neutral alumina (20 g)
with methylene chloride. A sample was crystallized from
methylene chloride-cyclohexane and then from ether to give
the pale yellow analytical sample of 3b, mp 161-163 °C. IR,
2-P h en yl-2-(ben zoyloxy)a cetic Acid (9d ).26 A solution
of methyl 2-phenyl-2-(benzoyloxy)acetate27 (methyl ester of the
(26) Angus, W. R.; Owen, R. P. J . Chem. Soc. 1943, 227 reported
isolation of a compound mp 115 °C from reaction of mandelic acid and
benzoyl chloride to which they assigned the structure 9d . Repetition
of this procedure in our hands afforded a product of similar melting
point which, however, could be shown by spectroscopic properties to
be impure benzoic acid and could be purified by recrystallization to
give pure benzoic acid, mp 122 °C, identical with an authentic sample.
1817, 1729, 1664 cm-1 13C NMR, 82.90, 99.73, 106.22, 122.18,
.

Photochemistry of Diaryl Vicinal Tetraketones
J . Org. Chem., Vol. 63, No. 3, 1998 487
benzoate of mandelic acid, 6 g, 0.022 mole) in dioxane (200
mL) in a three-necked flask maintained at water pump
vacuum (ca. 15 mm) and a 1% solution (180 mL) of potassium
hydroxide in water was added through an equalizing arm
dropping funnel with magnetic stirring during 15 min. Stir-
ring was continued for 40 min while maintaining the vacuum.
The flask was disconnected from the vacuum, and ether (200
mL) was added. After cooling to 10 °C, 1% hydrochloric acid
solution (125 mL) was added with stirring. The ether layer
was separated, washed with water, and dried over sodium
sulfate, and the ether was removed with a rotary evaporator.
Hexane (50 mL) was added to the residual oil. After standing
in the refrigerator, a white solid separated. Filtration and
drying afforded 4.5 g (78%) of 9d . Crystallization from ether-
hexane yielded 4.2 g, mp 98-100 °C. IR, (CHCl3) 1600, 1720,
130.06, 130.50, 133.29, 134.69, 160.25, 160.87, 163.38, 167.60
ppm. UV (CH3OH), 276 (11500), 234 (30000) nm. Anal. Calcd
for C30H20O6: C, 75.62; H, 4.23. Found: C, 75.23; H, 4.32.
Refluxing a sample (25 mg) in benzene for 1 h followed by
evaporation gave a white solid, mp 144-145 °C. Crystalliza-
tion from hexanes-ether gave white crystals of 22a , mp 146-7
°C. IR (KBr), 1682, 1733, 1767, 1782 cm-1. UV (CH3OH), 276
(9000), 236 (22000) nm. The IR and 1H NMR spectra in
chloroform solution were identical with that of the material
mp 116-117 °C described above.
When the reaction with TEA was performed in a UV cuvette,
a maximum at 510 nm was observed.
Cr ysta l Da ta for 22a . T 293 K, wavelength 0.71069 Å,
crystal system monoclinic, space group P21/n, a ) 17.102(8),
b ) 12.086(6), c ) 12.084(6) Å, â ) 104.76°, V ) 2415 Å,3 Z )
4, Dx ) 1.310 g cm-3, µ ) 0.091 mm-1, F(000) 992, crystal size
0.15 × 0.22 × 0.35 mm, θ range for data collection 2.09-25.02°,
index ranges -20 e h e 19, 0 e k e 14, 0 e l e 14, reflections
collected 4459, independent reflections 4253[R(int) ) 0.0255],
refinement method full-matrix least-squares on F2, number
of parameters 405, goodness-of-fit on F2 1.078, final R indices
[I > 2σ(I)] R1 ) 0.061, wR2 ) 0.099, R indices (all data) R1 )
0.126, wR2 ) 0.125, largest diff peak and hole 0.153 and
3000-3500 cm-1 1H NMR, 6.14 (1H), 7.39-7.56 (m, 8H), 8.09
.
(d, J ) 8 Hz, 2H), 8.99 (1H) ppm. MS, m/z 256 (M+). Anal.
Calcd for C15H12O4: C, 70.31; H, 4.72. Found: C, 70.63; H,
4.68.
r-(Ben zoyloxy)-r-p h en yla cetyl Ch lor id e (9b). The acid
chloride was prepared by heating 9d (4.49 g) with excess
freshly distilled thionyl chloride (2.7 mL) for 1 h at 80 °C.
Distillation gave 3.57 g (74%) of 9b, bp (0.1 mm) 150-2 °C.
The product crystallized on standing, mp 46-48 °C. IRmax
-0.170 eÅ-3
.
(CHCl3), 1725, 1800 cm-1
8H), 8.10 (d, J ) 8 Hz, 2H) ppm.
.
1H NMR, 6.31 (1H), 7.42-7.60 (m,
Rea ction of Keten e 8b w ith Meth a n ol. Preparation of
8b in toluene solution by reaction of acid chloride (0.325 g,
1.18 mM) with TEA (0.165 mL, 1.18 mM) at -80 °C afforded
a deep red solution. After 4 h at -90 °C, methanol (5 mL)
was added. The deep red color disappeared immediately.
After warming to room temp, the solution was concentrated
under reduced pressure, ether was added, and TEA‚HCl (0.151
g, 98%) was removed by filtration. Evaporation gave a white
solid which was washed through silica gel (10 g) with 8:1
hexanes-ether to give methyl R-phenyl-R-(benzoyloxy)acetate
(0.256 g, 80%), mp 74-76 °C, identical with an authentic
sample.
Meth yl r-(p-An isoyloxy)-r-p-a n isyla ceta te. A solution
of p-anisoyl chloride (4.43 g, 0.026 mol) in dry ether (5 mL)
was added dropwise with stirring at room temp to a solution
of methyl p-methoxymandelate28 (5.14 g, 0.026 mol) and
pyridine (2.07 g, 0.026 mol) in dry ether (30 mL) over 30 min.
The mixture was stirred for 24 h, precipitated pyridinium
hydrochloride was filtered off, and the solvents were removed
in vacuo. The crude product was crystallized from methanol
to give diester (5 g, 60%), mp 95-96 °C. IR, 1610, 1710, 1745
cm-1 1H NMR, 3.72 (s, 3H), 3.79 (s, 3H), 3.82 (s, 3H), 6.89 (d,
.
F or m a tion a n d Dim er iza tion of p-An isyl-p-(a n isoy-
loxy)k eten e (8c). TEA (0.26 mL, 0.0019 mol) was added with
a syringe to a solution of acid chloride 9c (0.63 g, 0.0019 mol)
in dry toluene (5 mL) maintained at 0-3 °C. A deep violet
color appeared immediately and a precipitate began to form.
The mixture was stirred at 0-3 °C for 1 h when the color had
disappeared completely. TEA‚HCl was filtered (0.25 g, 100%)
and washed with 5 mL of toluene. The filtrate and washings
were concentrated at reduced pressure to give an oil (0.56 g).
Washing through silica gel (17 g) with a mixture of hexanes-
ethyl acetate (3:1) gave an oil (0.5 g, 76%). All attempts to
crystallize failed. Prolonged drying of this oil in high vacuum
resulted in a solid foam, 22b. IR (CCl4), 1730, 1750 (sh), 1780
J ) 8 Hz, 2H), 6.92 (d, J ) 8 Hz, 2H), 7.47 (d, J ) 8 Hz, 2H),
8.03 (d, J ) 8 Hz, 2H) ppm. UV (CH3OH), 236 (13000), 260
(20000) nm. Anal. Calcd for C18H18O6: C, 65.45; H 5.49.
Found: C, 65.81; H, 5.24.
r-(p-An isoyloxy)-r-p-a n isyla cetic Acid (9e). The pro-
cedure described above for preparation of 9d afforded acid 9e
in 70% yield, mp 109-110° C. IR, 1710, 1725, 2700-3500
cm-1 1H NMR, 3.79 (s, 3H), 3.82 (s, 3H), 6.05 (s, 1H), 6.88 (d,
.
J ) 8 Hz, 2H), 6.91 (d, J ) 10 Hz, 2H), 7.47 (d, J ) 10 Hz,
2H), 8.02 (d, J ) 8 Hz, 2H) ppm. UV (CH3OH), 232 (13000),
258 (19000) nm.
r-(p-An isoyloxy)-r-p-An isyla cetyl Ch lor id e (9c). Thio-
nyl chloride (1.5 mL) in dry benzene (20 mL) was added
dropwise to 9e (3.94 g; 0.0125 mole) in benzene (30 mL). The
mixture was refluxed for 40 min and cooled to room temp and
solvent evaporated in vacuo. The oily residue crystallized
slowly on standing. The crystals of 9c (2 g, 50%) were
separated and dried, mp 72-74 °C. Standing with methanol
gave the methyl ester of 9e, identical in all respects with the
substance described above.
cm-1 1H NMR (CDCl3), 3.76 (s, 3H), 3.79 (s, 3H), 3.84 (s, 3H),
.
3.86 (s, 3H), 6.84 (d, J ) 9 Hz, 2H), 6.92 (d,d; J ) 8 Hz, J )
8 Hz; 4H), 7.56 (d, J ) 8 Hz, 2H), 7.68 (d, J ) 8 Hz, 2H), 7.94
(d, J ) 9 Hz, 2H), 8.01 (d, J ) 8 Hz, 2H) ppm. 1H NMR (C6D6),
3.00 (s, 3H), 3.07 (S, 6H), 3.14 (s, 3H), 6.36 (d, J ) 10 Hz, 2H),
6.26 (d, J ) 8 Hz, 2H), 6.59 (d, J ) 8 Hz, 2H), 6.68 (d, J ) 8
Hz, 2H), 7.75 (d, J ) 8 Hz, 2H), 7.86 (d, J ) 8 Hz, 2H), 7.99
(d, J ) 8 Hz, 2H), 8.14 (d, J ) 10 Hz, 2H) ppm. 13C NMR,
55.20, 55.29, 55.48, 55.61, 101.37, 113.80, 114.04, 116.54,
119.42, 119.97, 121.71, 126.10, 126.75, 128.28, 129.43, 132.20,
132.81, 159.71, 160.04, 160.18, 160.57, 163.14, 163.89, 164.64,
168.21 ppm. Anal. Calcd for C34H28O16 : C, 68.45, H, 4.73.
Found: C, 68.22, H, 4.92.
Rea ction s of Keten e 8b w ith Ca r bon yl Com p ou n d s.
Gen er a l P r oced u r e. Equivalent amounts of carbonyl com-
pound, triethylamine (TEA), and acid chloride in benzene (1
mL per 50 mg of carbonyl compound) were used. Triethy-
lamine was added dropwise with a syringe at room temp to a
stirred solution of carbonyl compound and 2-(benzoyloxy)phe-
nylacetyl chloride in benzene. After 1 h, triethylamine hy-
drochloride was filtered off and washed with benzene, and the
combined benzene solutions were evaporated to dryness.
Keten e w ith Dip h en yl Tetr a k eton e (1a ). Reaction of
0.41 g of 1a afforded a 54% yield of solidified foam after rapid
chromatography on silica gel eluting with hexanes-ethyl
acetate (50:1); IR, 1815, 1730, 1715, 1685, 1670 cm-1. Further
F or m a t ion a n d Dim er iza t ion of (Ben zoyloxy)p h e-
n ylk eten e (8b). Triethylamine (TEA) (0.5 mL, 3.6 mM) was
added with a syringe to a solution of acid chloride 9b (0.955
g) in dry benzene (10 mL). A deep red color appeared
immediately, and a precipitate began to form. The mixture
was left at room temp for 3 h when the color had completely
disappeared. The precipitated triethylamine hydrochoride
(TEA‚HCl) (0.47 g, 100%) was filtered and washed with
benzene (5 mL). The benzene solutions were concentrated to
give an oil (0.8 g). Washing through silica gel (24 g) with 20:1
hexanes-ethyl acetate gave a white solid (22a , 0.55 g, 72%),
mp 98-102 °C. Crystallization from 1:1 hexanes-ether (48
mL) gave 0.3 g of white solid, mp 116-117°. IR (KBr), 1672,
1740, 1726, 1795 cm-1
.
13C NMR, 101.36, 117.84, 125.32,
127.08, 127.32, 128.01, 128.61, 128.92, 129.20, 129.53, 129.99,
(27) Freudenberg, K.; Markert, L. Chem. Ber. 1925, 58, 1758.
(28) Barthel, W. F.; Leon, J .; Hall, S. A. J . Org. Chem. 1954, 19,
485.

488 J . Org. Chem., Vol. 63, No. 3, 1998
Rubin et al.
careful chromatography with the same system afforded crys-
talline 3a and 4a in the ratio 10:1. These products were
identical in all respects with the products of the photolysis of
1a .
8 Hz, 2H), 7.32-7.58 (m, 10H), 7.94 (d, J ) 8 Hz, 2H) ppm.
13C NMR, 24.89, 42.15, 55.42, 114.03, 123.28, 126.96, 127.96,
128.11, 128.34, 128.65, 129.57, 129.79, 131.54, 161.29, 168.45,
202.36 ppm. UV (CH3CN), 230 (21000), 262 (1800); 424 (20)
nm. MS, m/z 514. 1761, calcd for C30H26O8 514.1728. Anal.
Calcd for C30H26O8: C, 70.03, H, 5.09. Found: C, 69.87, H,
5.15.
Keten e w ith Dim esityl Tetr a k eton e (1d ). The crude
product from 0.24 g of 1d was an oil, IR (neat), 1822, 1725,
-1
1680 cm
. Chromatography on silica gel eluting with
hexanes-ethyl acetate (40:1) gave a yellow solid (45%), which
contained 25d and 26d in the ratio approximately 1:1 (by
spectroscopic analysis). Crystallization from hexane afforded
25d as yellow crystals, mp 143-146 °C. IR, 1808, 1728, 1678
The mother liquors after separation of 24f were concen-
trated and passed through silica gel with hexanes-ethyl
acetate (20:1) affording additional 25f (7%), and white crystals
of 26f (9%), mp 152-153 °C. IR, 1813, 1718, 1651 cm-1 1H
.
cm-1
.
1H NMR (400 MHz), 1.24 (s, 6H), 2.16 (s, 6H), 2.56
NMR, 1.34 (9H), 3.76 (3H), 6.73 (d, 2H, J ) 8 Hz), 7.22-7.26
(m, 3H), 7.37-7.40 (m, 2H), 7.53-7.60 (m, 3H), 7.85 (d, 2H, J
) 8 Hz), 7.89 (d, 2H, J ) 8 Hz) ppm. 13C NMR, 26.05, 44.12,
55.42, 83.46, 98.75, 108.06, 113.58, 123.15, 126.99, 127.50,
127.99, 128.14, 128.23, 128.69, 128.74, 129.60, 131.69, 132.01,
164.30, 168.39, 189.04, 201.58 ppm. UV (CH3CN), 298 (20000)
nm. MS m/z 514. 1761, calcd for C30H26O8 514.1728.
(broad s, 6H), 6.62 (s, 2H), 6.78 (s, 2H), 7.34-7.35 (m, 3H),
7.53-7.56 (m, 3H), 7.72 (broad peak, 2H), 7.95 (d, J ) 8 Hz,
2H) ppm. 13C NMR, 18.61, 20.46, 21.14, 23.95 (broad), 25.41
(broad), 81.40, 100.78, 109.94, 121.80, 124.80, 126.86, 127. 26d ,
127.76, 128.00, 128.43; 128.65, 128.80, 129.10, 129.62, 129.81,
131.39, 132.82, 136.84, 139.35 (broad), 139.91, 141.53, 167.54,
193.38 ppm. UV (CH3CN), 262 (14000), 330 (10000), 458 (100)
nm. MS, m/z 544.2153, calcd for C36H32O5 (M - CO2) 544.2159.
The mother liquors, upon standing at -15 °C in hexane,
afforded 26d as white crystals, mp 154-157 °C. IR, 1826, 1712
R ea ct ion of p-(An isoyloxy)-p -a n isylk et en e (8c) w it h
1c. The crude oil obtained from reaction of 1c (0.34 g) with
R-(p-anisyl)-R-(p-anisoyloxy)acetyl chloride (9c) and triethy-
lamine had IR maxima at 1810 and 1720 cm-1
. Washing
(w), 1657 cm-1
.
1H NMR, 1.92 (s, 6H), 2.21 (s, 6H), 2.27 (s,
through silica gel gave 0.53 g (85%) of yellow solid identical
6H), 6.74 (s, 2H), 6.87 (2H), 7.33-7.37 (m, 3H), 7.49-7.56 (m,
3H), 7.78 (d, J ) 8 Hz, 2H) ppm. 1H NMR (C6D6), 1.92 (3H),
2.03 (3H), 2.17 (6H), 2.41 (s, 6H), 6.54 (s, 2H), 6.60 (2H), 6.98-
7.07 (m, 6H), 7.74 (d, J ) 8 Hz, 2H), 7.81 (d, J ) 8 Hz, 2H)
ppm. 13C NMR, 19.89, 20.92, 21.07, 21.13, 84.25, 99.06, 107.95,
122.83, 126.78, 127.93, 128.17, 128.61, 128.74 129.45, 129.75,
129.92, 131.57, 133.11, 133.69, 135.15, 138.82, 139.90, 141.58,
168.30, 196.81, 196.90 ppm. UV (CH3CN), 282 (6500) nm. MS,
m/z 544 0.2243, calcd for C36H32O5 (M - CO2) 544.2159. Anal.
Calcd for C37H32O7: C, 75.49, H, 5.48, Found: C, 75.39, H,
5.48.
in all respects with 3c described above.
Rea ction of 8b w ith Bia cetyl. Reaction of 8b (0.6 g) with
biacetyl gave a crude oil, IR 1840 (sh), 1795 cm-1. Trituration
with pentane-ether did not give crystalline material. Tritu-
ration with methanol resulted in decomposition of the sub-
stance. Washing through silica gel with hexanes-ethyl
acetate (20:1) gave white crystals of 12b, yield 54%, mp 114-
115 °C. IR, 1795, 1605 cm-1 1H NMR 1.31 (s, 3H), 1.70 (s,
.
3H), 7.41-7.51 (m, 8H), 7.81 (d, J ) 8 Hz, 2H) ppm. 13C NMR
10.15, 17.82, 82.67, 91.56, 108.43, 121.28, 126.65, 127.02,
128.32, 128.48, 129.11, 129.29, 130.63, 131.06, 170.33 ppm.
UV (CH3CN) 260 (600) nm. MS m/z (CI, isobutane) 325 (M +
H)+. Anal. Calcd for C19H16O5: C, 70.36; H, 4.97. Found: C,
70.29; H, 5.03.
Keten e w ith Di-ter t-bu tyl Tetr a k eton e (1e). The crude
product from 0.30 g of 1e showed IRmax (neat), 1840, 1790, 1720
cm-1. Trituration with ether gave yellow crystals of â-lactone
24e (70%), mp 113-116 °C. IR, 1838, 1738, 1711 cm-1
.
1H
Rea ction of 8b w ith Ben zil. The crude oil obtained after
standing of 0.64 g of benzil with 8b for 3 h at room temp
showed IR maxima at 1815, 1785, 1740, 1720 cm-1. Chroma-
tography on silica gel gave 78% of unreacted benzil, 4% of
benzoin benzoate, and 20% (based on acid chloride) of dimer
23a .
NMR (C6D6) 0.73 (9H), 1.24 (9H), 6.93-7.18 (m, 6H), 7.97 (d,
2H, J ) 8 Hz), 8.12 (d, 2H, J ) 8 Hz) ppm. 13C (C6D6) 25.81,
27.45, 42.69, 45.86, 90.69, 92.66, 121.81, 125.86, 127.18,
127.67, 127.75, 127.87, 128.58, 128.76, 128.84, 129.76, 130.01,
131.82, 165.49, 186.81, 203.22, 203.80 ppm. UV (CH3CN) 254
(14000), 444 (35) nm. MS, m/z 436.1923, 420.1944; calc for
Rea ction of Keten e w ith 9,10-P h en a n th r en equ in on e
(P Q). The crude oil from reaction of 0.20 g of PQ was
triturated with ether to give 23 as white crystals (0.34 g, 81%),
mp 135-142 °C. The analytical sample of 23 was obtained
by crystallization from hexanes-ethyl acetate, mp 148-150
C
26H28O6 (M - CO) 436.1886, for C26H28O5 (M - CO2)
420.1937.
After standing for 1 h in chlorofrom at room temp, 24e had
rearranged in 90% yield to γ-lactone 25e mp 128-131 °C. IR,
1807, 1734, 1719 cm-1 1H NMR, 0.81 (s, 9H), 1.02 (s, 9H),
.
°C. IR, 1805 cm-1 1H NMR (C6D6), 6.32 (d, 1H, J ) 8 Hz),
.
7.29-7.33 (m, 3H), 7.47-7.60 (m, 5H), 7.83 (d, J ) 8 Hz, 2H)
ppm. 13C NMR, 24.80, 24.98, 25.06, 36.93, 42.61, 97.99, 113.20,
120.46, 126.81, 128.26, 128.47, 128.72, 128.93, 129.14, 129.63,
130.38, 131.26, 168.51, 201.64 ppm. UV (CH3CN), 226 (2000),
256 (1500), 428 (25) nm. MS, m/z 464.1821; calcd for C27H28O7
464.1835. Anal. Calcd for C27H28O7: C, 69.81; H, 6.08.
Found: C, 69.58; H, 6.01.
6.60 (t, 1H, J ) 8 Hz), 6.96-7.24 (m, 10H), 7.49 (d, 1H, J ) 8
Hz), 7.57 (d, 1H, J ) 8 Hz), 7.84-7.93 (m, 4H) ppm. MS, m/z
446.1180, calcd for C29H18O5 418.1162.
R ea ct ion of p -(An isoyloxy)-p -a n isylk et en e (8c) w it h
Di-p-An isyltetr a k eton e (1c). Reaction of 1c (0.34 g) with
8c, generated from acid chloride 9c, followed by chromatog-
raphy on silica gel gave a crystalline yellow product in 85%
yield. It was identical in all respects with 3c obtained from
the photochemical reaction of tetraketone 1c.
The mother liquors after separation of 24e were concen-
trated and chromatographed on silica gel with hexanes-ethyl
acetate (20:1) to give additional 25e (2%) and 26e (3%, mp
108-110° C). IR, 1827, 1717, 1687 cm-1
.
1H NMR, 0.81 (s,
9H), 1.32 (s, 9H), 7.33-7.37 (m, 5H), 7.57-7.60 (m, 3H), 7.84
(d, 2H, J ) 8 Hz) ppm. 13C NMR, 24.57, 25.04, 25.26, 26.08,
26.25, 26.40, 44.06, 45.94, 83.67, 98.66, 108.42, 122.80, 126.99,
127.68, 127.89, 127.99, 128.26, 128.50, 129.04, 129.62, 130.17,
131.54, 168.51, 201.18, 205.32 ppm. MS, m/z 436.1916, calcd
for C26H28O6 (M-CO) 436.1886.
Ack n ow led gm en t. This research was supported in
part by the German-Israel Foundation for Scientific
Research and Development and by the Technion Fund
for the Promotion of Research. M.E. and R.M. acknowl-
edge support from the Israel Ministry of Absorption.
This paper is dedicated to Professor Rolf Gleiter,
Heidelberg, on the occasion of his 60th birthday.
Keten e w ith p-An isyl ter t-Bu tyl Tetr a k eton e. The
crude product from reaction of 0.30 g of tetraketone had IRmax
(neat), 1841, 1734, 1706, 1682 cm-1. Trituration with ether
gave yellow crystals of 24f (53%), mp 102-103 °C. IR, 1844,
Su p p or tin g In for m a tion Ava ila ble: Details of X-ray
structure analysis of 22a (6 pages). This material is contained
in libraries on microfiche, immediately follows this article in
the microfilm version of the journal, and can be ordered from
the ACS; see any current masthead page for ordering
information.
1734, 1703, 1682 cm-1 1H NMR (C6D6), 0.77 (s, 9H), 3.02 (s,
.
3H), 6.42 (d, J ) 8 Hz, 2H), 7.09-7.18 (m, 6H), 8.10-8.14 (m,
6H) ppm. 13C NMR (C6D6) 25.32, 42.56, 54.87, 90.21, 91.39,
114.26, 122.00, 164.19, 165.89, 187.30, 188.54, 201.80 ppm.
Compound 24f rearranged rapidly in chloroform solution at
room temp to give 25f, mp 145-147 °C, in 85% yield. IR, 1815,
1733, 1692 cm-1
.
1H NMR, 0.68 (9H), 3.78 (3H), 6.68 (d, J )
J O971247Q