Reactions of carbonyl compounds in basic solutions. Part 23. 1 the mechanism of the base-catalysed ring fission of 2,2-dihydroxyindane-1,3-diones

Article abstract of DOI:10.1039/a606312h

The base-catalysed ring fission of a series of substituted 2,2-dihydroxyindane-1,3-diones and phenalene-1,3-dione has been studied in 30% (v/v) dioxane-water. The reaction proceeds in two distinct steps. The first is a relatively fast base-catalysed ring fission to give substituted o-carboxyphenylglyoxals, and the second is a rearrangement of the latter resulting in formation of substituted 0-carboxymandelic acids. Rate coefficients for the ring fission of a limited series of substrates have been determined at 25.0°C. The reaction is first order in the mono-anion of the substrate alone. The Hammett reaction constants, ρ, have been obtained from both the kinetic and product studies. The rate- and product-determining step appears to be an intramolecular nucleophilic attack. The rate coefficients for the rearrangement have been determined for all substrates at 25.0, 35.0 and 45.0°C. The activation parameters have been calculated. The kinetic solvent isotope, solvent and salt effects have been studied. The effects of the 5-substituted and 5,6-disubstituents on the rates have been correlated using a modified Hammett equation giving a reaction constant, ρ, equal to 3.4 at 25°C.

Full text of DOI:10.1039/a606312h

View Article Online / Journal Homepage / Table of Contents for this issue
Reactions of carbonyl compounds in basic solutions. Part 23.1 The
mechanism of the base-catalysed ring fission of 2,2-dihydroxyindane-
1,3-diones
Keith Bowden* and Sanjay Rumpal
Department of Biological and Chemical Sciences, Central Campus, University of Essex,
Wivenhoe Park, Colchester, Essex, UK CO4 3SQ
The base-catalysed ring fission of a series of substituted 2,2-dihydroxyindane-1,3-diones and phenalene-
1,3-dione has been studied in 30% (v/v) dioxane–water. The reaction proceeds in two distinct steps. The
first is a relatively fast base-catalysed ring fission to give substituted o-carboxyphenylglyoxals, and the
second is a rearrangement of the latter resulting in formation of substituted o-carboxymandelic acids.
Rate coefficients for the ring fission of a limited series of substrates have been determined at 25.0 ЊC. The
reaction is first order in the mono-anion of the substrate alone. The H ammett reaction constants, ñ, have
been obtained from both the kinetic and product studies. The rate- and product-determining step appears
to be an intramolecular nucleophilic attack. The rate coefficients for the rearrangement have been
determined for all substrates at 25.0, 35.0 and 45.0 ЊC. The activation parameters have been calculated.
The kinetic solvent isotope, solvent and salt effects have been studied. The effects of the 5-substituted and
5,6-disubstituents on the rates have been correlated using a modified H ammett equation giving a reaction
constant, ñ, equal to 3.4 at 25 ЊC.
The benzilic acid and related rearrangements were reviewed in
1960 by Selman and Eastham.2 These included the intra-
molecular Cannizzaro-type reaction of phenylglyoxal3 and the
base-catalysed rearrangement–fission of 1,3-diphenylpropane-
1,2,3-triones.4,5 However, in 1910, Ruhemann 6 had found that
indane-1,2,3-trione, as the hydrate (ninhydrin) 1, rearranged in
base to give o-carboxymandelic acid 2 (isolated as its lactone 3).
More recently, the kinetics of this reaction were studied using
polarography7 and a pathway involving o-carboxyphenyl-
glyoxal 4/5 as an intermediate was suggested. This suggestion
parameters, substituent, salt, solvent and solvent isotope effects
are reported. The present study, together with the following
Parts 24 and 25, present an attempt to elucidate the pathways
for base-catalysed ring fission of 1,2-dicarbonyl and 1,2,3-
tricarbonyl compounds, as well as the factors controlling their
modes of reactivity.
Results and discussion
Acidity of the hydrates
The 2,2-dihydroxy 1,3-diones are gem-diols and are consider-
ably more acidic than 1,2-glycols. It is possible to estimate the
pKa in water of 2,2-dihydroxyindane-1,3-dione 1 as 8.85, using
the relation (1) for gem-diols and σ* for PhCO equal to 2.2.9
O
CO2H
i OH–
ii H+
OH
OH
CH(OH)CO2H
X
X
pKa = 14.4 Ϫ 1.42 ͚ σ*
(1)
O
2
1
H+
The pKa of 1 has been reported to be 8.6 from polarographic
studies,7 with the dihydrate, 1,1,2,2-tetrahydroxyindan-3-one,
being considered to be a significantly weaker acid. For the
kinetics studied here, the base concentrations were sufficient to
ionise almost completely the gem-diols.
O
C
O
C
X
The base-catalysed ring fission and rearrangement
CO2H
H
Two possible mechanistic schemes are shown in Schemes 1 and
2. Scheme 1 shows a pathway involving intramolecular nucleo-
philic attack within the anion 6 to form the fused oxirane 7.
Ring opening of this intermediate gives the carbanionic inter-
mediate 8. These processes have analogies with both the reac-
tion of 1 with nitroalkanes10 and the reaction of 1,2-dicarbonyl
compounds with cyanide.11,12 Proton exchange in the inter-
mediate 8 is followed by ring-opening of the semi-acetal anion
9, resulting in the formation of the monoanion of o-
carboxyphenylglyoxal 10. Compound 10 may be regarded as
a relatively stable intermediate which will suffer an intra-
molecular Cannizzaro-type reaction catalysed by base to give
the dianion of o-carboxymandelic acid 15 as the final product,
cf. ref. 3. Scheme 2 shows a pathway which is essentially a
benzilic acid-type rearrangement of the type employed by
related 1,2-dicarbonyl and 1,2,3-tricarbonyl compounds.2–4 The
3
O
C
CO2H
O
C
COCHO
CHO
H
5
4
had already been made by Ruhemann.6 A closely related path-
way has been offered for the reaction of 1 with cyanide.8
The present study describes a detailed investigation of base-
catalysed ring fission of a series of substituted 2,2-dihydroxy-
indane-1,3-diones. The products of the fission have been
determined and possible intermediates examined. The rates of
the base-catalysed ring fission and rearrangement, activation
J. Chem. Soc., Perkin Trans. 2, 1997
983

View Article Online
Table 1 Rate coefficients (k1 and k2) for the base-catalysed ring fission and rearrangement of substituted 2,2-dihydroxyindane-1,3-diones in 30%
(v/v) dioxane–water (µ = 0.1 mol dmϪ3
)
Substituent(s)
Ring fission a
k1/10Ϫ2 sϪ1
at 25 ЊC
Rearrangementb k2/10Ϫ2 dm3 molϪ1 sϪ1
5-
6-
at 25.0 ЊC
at 35.0 ЊC
at 45.0 ЊC
λ/nm c
H
CH3
OCH3
Cl
CH3
OCH3
Cl
Benzo[ f ]
Phenalene-
1,3(2H)-dione
H
H
H
H
CH3
OCH3
Cl
5.00
5.89 (2.14)d
1.29
0.820
45.4
0.408
11.2
2.82
1.86
87.7
0.944
0.313
450
21.2
5.77
4.08
161
2.12
0.746
796
230, 246
—, 234
—, 240
235, 223
—, 241
—, 255
240, 240
—, 269
220, 324
e
e
11.0
e
e
0.129
21.8
e
1.22
237 (87.8)d
3.51
7.61
236
15.6
584
89.9
a
b
c
Rate coefficients were reproducible to ±6%. Rate coefficients were reproducible to ±3%. Wavelengths used to monitor the ring fission and
rearrangement reaction, respectively. d In 30% (v/v) dioxane–deuterium oxide. e Rate coefficients could not be obtained (see text).
O
O
O
O
K′a
+H+
–H+
O
O
O
O
Ka
–H+
O–
OH
OH
O–
OH
OH
OH
+H+
OH
X
X
X
X
6
6
1
1
k′′
k′′
k′–1
k′1
–2
2
O
O
O–
–H+
fast
O
O
O
O
O
k′2
–
CO2H
+H+
CO2
–
OH
k′–2
OH
OH
X
O–
X
X
X
O–
X
O
17
O
O–
16
8
7
k′3
k′′
k′′
3
–3
O
O
–
O
O–
O–
O
H
fast
O
O
H
O
O–
O
–
X
X
X
X
CO2
–
CO2
O
19
+H+
18
10
9
KH
–H2O + H2O
fast
O
O
O
O
O
K′a1
+OH–
O–
O–
–H+
+H+
O–
k′′
4
O–
O
H
H
O–
O
OH
X
X
X
X
–
O
OH
OH
H
CO2
HO
H
11
12
20
15
O
Scheme 2
O–
H
O
–H+
+H+
K′a2
ing of this intermediate gives the carbanion 19. Protonation
of the latter gives the monoanion of the lactone of
o-carboxymandelic acid 20. Base-catalysed hydrolysis of the
lactone 20 gives the final product 15. This is analogous to the
base-catalysed rearrangement of 1,3-diphenylpropane-1,2,3-
trione.5
O–
X
OH
fast
15
+H+
O
O
O–
O–
k′′1
H
O
H
Intermediates
O–
O–
X
X
O–
O–
O
In Scheme 1 the anion of o-carboxyphenylglyoxal 10, or its
hydrate 11, would be expected to be a relatively stable inter-
mediate. This was not observed, isolated or trapped in previous
studies.6–8 Phenylglyoxals have been shown to readily undergo
intramolecular Cannizzaro-type reactions to form the mono-
anions of mandelic acids in base.3,4 o-Carboxyphenylglyoxal
has been prepared directly as the product of ozonolysis of 1,4-
naphthoquinone.13
14
13
Scheme 1
monoanion 6 suffers ring contraction by migration of the aroyl
group to form the benzocyclobutanone 16. This is followed by
rapid ionisation of the carboxylic acid to form 17 and then
intramolecular attack to give the fused oxirane 18. Ring open-
In this study, the kinetics of the base-catalysed fission of the
984
J. Chem. Soc., Perkin Trans. 2, 1997

View Article Online
Table 2 Product ratios, ratio, for the base-catalysed ring fission and activation parameters for the base-catalysed rearrangement of substituted 2,2-
dihydroxyindane-1,3-diones in 30% (v/v) dioxane–water at 30 ЊC (µ = 0.1 mol dmϪ3
)
Substituent(s)
5-
Rearrangement a
Ring fission
product ratio,b
ratio
6-
∆H ‡/kcal molϪ1 c
∆S ‡/cal molϪ1 KϪ1 c
H
CH3
OCH3
Cl
CH3
OCH3
Cl
Benzo[ f ]
Phenalene-
1,3(2H)-dione
H
H
H
H
CH3
OCH3
Cl
11.5
13.5
14.5
11.3
14.9
16.0
10.8
13.5
17.0
Ϫ26
1
Ϫ22
Ϫ19
Ϫ22
Ϫ20
Ϫ18
Ϫ21
Ϫ20
Ϫ2
0.805
0.305
0.62
1
1
1
1
1
a
Values of ∆H ‡ and ∆S ‡ are considered accurate to with ±300 cal molϪ1 KϪ1 and ±1 cal molϪ1 KϪ1, respectively. b See text. c 1 cal = 4.184 J.
Table 3 Rate coefficient (k2) for the base-catalysed rearrangement of
Table 4 Hammett reaction constants (ρ) for the base-catalysed reac-
2,2-dihydroxyindane-1,3-dione in aqueous dioxane at 25.0 ЊC (µ = 0.l
tions of substituted 2,2-dihydroxyindane-1,3-diones
b
mol dmϪ3
)
ρ
log k0
r
s
n
Volume (%) dioxane
k2/10Ϫ2 dm3 molϪ1 sϪ1
Ring fission
0a
10
30
50
70
5.15
5-Substituent and 5,6-
disubstituent with σp and 2σp
5-Substituent and 5,6-
disubstituent with σm and 2σm
5-Substituent product ratios
with (σp Ϫ σm)
0.857 Ϫ1.203 0.999 0.035
1.409 Ϫ1.203 0.999 0.058
3
3
4
5.03
5.89 (10.2)c (11.0)d
13.6
120
1.335
0.007 0.994 0.105
0.5% (v/v) dioxane–water. b See Table 1. c µ = 0.5 mol dmϪ3 d µ = 1.0
.
a
mol dmϪ3
.
Rearrangement
substituted 2,2-dihydroxy 1,3-diones has been found to be
biphasic. First, there is a very rapid reaction to form a relatively
stable intermediate. The UV–VIS spectra of the intermediate
product for 1 is almost identical with that of o-carboxy-
phenylglyoxal under the same conditions. This first reaction is
first order in the substrate (mono-anion of gem-diol) and zero
order in base. Secondly, there is a fast, but relatively slow, reac-
tion to form the final products of the reaction, the dianion of
the corresponding o-carboxymandelic acids. The second reac-
tion is first order both in the substrate and in base. The rate of
this reaction for 1 is identical with that of o-carboxy-
phenylgloxal under the same conditions. Table 1 shows the rate
coefficients for the base-catalysed ring fission and rearrange-
ment in 30% (v/v) dioxane–water, with the activation param-
eters and solvent and salt effects on the rates of rearrangement
shown in Tables 2 and 3, respectively.
Mono-substituents with σp
Disubstituents with 2σp
Mono-substituents and
disubstituents with σp and 2σp
(Hydration vs. rearrangement
3.580 Ϫ1.199 0.996 0.229
3.380 Ϫ1.186 0.999 0.120
3.362 Ϫ1.191 0.998 0.108
4
4
7
0.380 Ϫ1.642 0.971 0.031 8)
a
s is the standard deviation, r the correlation coefficient and n the
number of substituents studied.
results in open-chain systems, the relative ring strain would
appear to be the main source for this rate diference.
Kinetic substituent effects
The Hammett equation (2) is usually employed in the quanti-
log(k/ko) = ρσ
(2)
tative assessment of meta/para-substituent effects in aromatic
systems.14 For 2,2-dihydroxyindane-1,3-diones, the situation is
more complex for 5- or 6-substituents, which could be con-
sidered to be both meta- and para-substituents for reactions in
the side-chain. Having results for only three relevant substrates,
it is only possible to make preliminary correlation studies with
either σp and 2σp, for the 5-substituted and the identically 5,6-
disubstituent, respectively, or, similarly, σm and 2σm. The corre-
lations given are shown in Table 4 and are good with ρ equal to
ca. 0.9 or 1.4 (see further below).
In Scheme 2 the monoanion of the lactone of o-carboxy-
mandelic acid 20 could be a relatively stable intermediate. The
isolated product, after treatment with acid, is the lactone itself.
This lactone is rapidly hydrolysed in aqueous base with k1 equal
to ca. 1.23 sϪ1 in water at 0.01 mol dmϪ3 base at 25 ЊC. Thus, if
formed as an intermediate, 20 would not be observed.
The evidence appears to be unequivocally in favour of
Scheme 1.
Rates of base-catalysed ring fission
Owing to biphasic kinetics, rapidity of reactions and spectral
changes, it was only possible to measure securely the rate co-
efficients for the base-catalysed ring fission of the four most
reactive substrates, i.e. the unsubstituted, 5-chloro- and 5,6-
dichloro-2,2-dihydroxyindane-1,3-diones and 2,2-dihydroxy-
phenalene-1,3-dione, in 30% (v/v) dioxane–water at constant
ionic strength (µ = 0.1 mol dmϪ3) at 25.0 ЊC. The reactions were
first order in the mono-anion of the substrate. The rates of
reaction are accelerated by electron-withdrawing substituents.
The six-membered ring 2,2-dihydroxyphenalene-1,3(2H)-dione
reacts significantly slower than the five-membered ring 2,2-
dihydroxyindane-1,3-dione 1. Angle strain in the five-
membered cycle system (ca. ϩ48Њ) is much greater than that in
the six-membered cyclic system (ca. Ϫ12Њ). As the ring fission
Product substituent effects
The final isolated reaction products for base-catalysed ring fis-
sion of the substituted 2,2-dihydroxyindane-1,3-diones are the
corresponding lactones of the substituted o-carboxymandelic
acids 3. For the unsubstituted and identically disubstituted sub-
strates, there is only one product. For the monosubstituted sub-
strates there are two possible products, as shown in Scheme 3,
i.e. the di-anions of the 5- and 4-substituted 2-carboxymandelic
acids. The product ratios, ratio, of the corresponding lactones,
i.e. the 1,3-dihydro-3-oxoisobenzofuran-1-carboxylic acids,
1
were measured using H NMR spectroscopy and are shown in
Table 2. Thus, ratio is equal to the ratio of 4-substituted to that
of 5-substituted o-carboxymandelic acid, x4/x5. These results
J. Chem. Soc., Perkin Trans. 2, 1997
985

View Article Online
–
CO2
are shown in Table 2. These values are consistent with a bi-
kb
molecular reaction. In general, electron-withdrawing groups
decrease and electron-releasing groups increase ∆H ‡. The faster
rate for 8-carboxy-1-naphthylglyoxal results from a greatly
reduced negative ∆S ‡ value of Ϫ2 cal molϪ1 KϪ1 coupled with a
significantly increased ∆H ‡ value. This suggests a transition
state for this compound involving very favourable stereo-
chemistry, but unfavourable electrostatic and steric interactions.
This type of behaviour has been found in 1,8-disubstituted
systems.19,20
O
C
–
–
X
X
CH(OH)CO2
OH
OH
+ OH–
C
–
CO2
C
O
X
ka
CH(OH)CO2
Scheme 3
are of importance as they identify the point of cleavage of the
substrate. The 5-substituted product predominates in all cases.
The Wegscheider principle15 relates the ratio of two products
formed in irreversible, simultaneous reactions to their rates of
formation as shown in eqn. (3). If the Hammett equation is
Kinetic solvent isotope, solvent and salt effects
H 2
D 2
The kinetic solvent isotope effects, k2 O/k2 O, for the unsubsti-
tuted and 5,6-dichloro substrates are both ca. 0.37 at 25 ЊC (see
Table 1). Thus, no significant, detectable primary isotope effect
H 2
D 2O
occurs. Values of k2 O/k2 have been found for the base-
catalysed ring fission of benzocyclobutenedione in water at
25 ЊC,21 for the benzilic acid rearrangement in 2:1 dioxane–
water at 50 ЊC 22 and for alkaline hydrolysis of methyl benzoate
in 70% aqueous dioxane at 25 ЊC 23 to be 0.58, 0.54 and 0.87,
respectively. Such results have been ascribed to the greater bas-
icity and nucleophilicity of deuteroxide anions in D2O, than of
hydroxide anions in H2O. The reason for the significantly
reduced ratio found in this study probably arises from the
dianionic initial and transition states in which the solvation
effects underlying the kinetic solvent isotope effects are
approximately double those observed for monoanionic
systems.24
x4/x5 = ka/kb or log(x4/x5) = log(ka/kb)
(3)
applied to both these processes and the reaction constants for
both process forming products are the same, eqn. (4) results, cf.
log(kb/kH ) = ρσm and log(ka/kH ) = ρσp
(4)
ref. 16. Substituting in eqn. (3) the values of log kb and log ka
derived from eqn. (4) gives the final relation, eqn. (5). The
log(x4/x5) or log ratio = ρ(σp Ϫ σm)
(5)
The effect of dioxane content on the rates of rearrangement
are shown in Table 3, together with the effect of increasing ionic
strength. No simple relations between solvent effects and rates
exist. However, the dramatic increase in rate with increasing
dioxane content would be that expected from the formation of
dianionic transition state from two monoanions as an initial
state with the greatly decreased relative permittivity of the
medium as dioxane content increases.25 This is quite unlike
and opposite to the changes observed for the reaction of
dipolar molecules such as methyl benzoate26 and benzocyclo-
butenedione21 with hydroxide anions in aqueous dioxane. The
significant increases in rate observed for increased ionic
strength of the medium clearly indicate a positive primary salt
effect.27 This appears to indicate a rate-determining step having
a transition state with a dianionic structure formed from two
monoanions. Comparable effects have been observed for
the intramolecular Cannizzaro reaction of biphenyl-2,2Ј-
dicarbaldehyde28 and the benzilic acid rearrangement of
2-carboxybenzil,29 both of which involve the formation of a
dianion from two monanions.
correlation between log ratio and (σp Ϫ ρm) is very good as
shown in Table 4. The reaction constant, ρ, equal to ca. 1.3
refers to the ring fission product-determining step. The latter
process would be the formation of the anionic oxirane 7 from
the anion 6. Model processes, which enable an estimate for ρ for
the latter reaction, would be the development of a negatively
charged tetrahedral intermediate for alkaline hydrolysis of suit-
able esters. For 6 passing to 7, this is the difference between the
ρ for alkaline hydrolysis of methyl benzoates (2.07 in 40%
aqueous dioxane at 20 ЊC)17 and of methyl phenylacetates. The
latter can be calculated using the transmission coefficient for a
methylene group 18 (0.58) as shown in eqn. (6). The estimate of
ρ = 2.07 (1.0 Ϫ 0.58) = 0.9
(6)
0.9 is in reasonable agreement, considering the uncertainties,
with the observed value of 1.3. The observed ρ values for the
kinetic and product determining steps are very similar and it
appears likely that they relate to the same process, i.e. kЈ1 in
Scheme 1.
Kinetic substituent effects
Rates of base-catalysed rearrangement
As ring fission has already occurred, the modified Hammett
equation suggested by Jaffé30 for transmission via two links is
not applicable. It is just possible that a polar effect could be
transmitted via the 2-carboxylate group, but this is unlikely
here. As in our investigation of the uncatalysed hydration
of substituted indane-1,2,3-triones,31 correlations of identical
disubstituents using σm ϩ σp are very poor, as is that of mono-
substituents using σm. Again, correlations of mono-substituent
effects with σp and identical disubstituent effects with 2σp
are very successful, as shown in Table 4. Similar behaviour
was so found for the base-catalysed ring fission of benzo-
cyclobutenediones.21 A possible cause for this behaviour has
been discussed previously.31 1,2-Dicarbonyl substitution in a
benzene ring may result in powerful cross-conjugation effects
with substituents so modifying the expected substituent effects.
Furthermore, a plot of log k1 for hydration of the substituted
indane-1,2,3-triones in 96.7% aqueous dioxane at 25 ЊC versus
log k2 for the rearrangement reaction in 30% aqueous dioxane
at 25 ЊC is linear with a correlation coefficient of 0.971 (see
Table 4), showing that substituents behave very similarly in
The rate coefficients for the base-catalysed rearrangement in
30% (v/v) dioxane–water at constant ionic strength (µ = 0.1 mol
dmϪ3) are shown in Table 1. The reported kinetic studies for the
ring fission in water of 1 using a polarographic method 7 agree
well with the present studies for the rearrangement. The prod-
ucts of the reaction were the dianions of the corresponding
substituted o-carboxymandelic acids. The reactions were found
to be strictly first order in the substrates, the o-carboxyphenyl-
glyoxals, i.e. the conjugate base of the monanionic hydrate 12,
and first order in base. The trends in the rates clearly indicate
that the rates of reaction are accelerated by electron-
withdrawing and retarded by electron-releasing substituents.
The fused benzo[ f ] substituent results in a small decrease in the
rate resulting from a modest electron-withdrawing resonance
effect. 8-Carboxy-1-naphthylglyoxal reacts very much faster
than o-carboxyphenylglyoxal (see below).
Activation parameters
The activation parameters for the base-catalysed rearrangement
986
J. Chem. Soc., Perkin Trans. 2, 1997

View Article Online
Table 5 The physical constants of the previously unreported substituted 1,3-dihydro-3-oxoisobenzofuran-1-carboxylic acids
Substituents Found (%) Calc. (%)
5-
6-
Mp/ ЊC
C
H
Other
Formula
C
H
Other
CH3
OCH3 OCH3
Cl Cl
CH3
188–190a
200–203b
194–196a
64.3
55.1
43.6
4.7
4.2
1.4
C11H10O4
C11H10O6
C9H4Cl2O4
64.1
55.5
43.8
4.9
4.2
1.6
28.0(Cl)
28.7(Cl)
a
Colourless prisms. b Colourless crystals.
both reactions. This is a surprising result as ring fission has
already occurred for the substrates of the rearrangement. How-
ever, the mono-substituted 2-carboxyphenylglyoxals are a mix-
ture of 4- and 5-substituted compounds. Thus, the reaction
constant, ρ, for the base-catalysed rearrangement was found to
be ca. 3.4 in 30% aqueous dioxane at 25 ЊC and indicates the
size and position of the charge developed in the transition state,
compared to the initial state.32 Comparisons with other systems
must be done with care as these may have been studied in differ-
ent solvent systems and at different temperatures. The same
reaction for a series of substituted phenylglyoxals in water at
pH 12 and 25 ЊC gave a ρ value of 2.0.36 The base-catalysed ring
fission of benzocyclobutenediones in water at 25 ЊC 21 and the
cyanide-catalysed cleavage of benzils in alcoholic solutions at
30 ЊC 12 gave ρ values equal to ca. 3.7 and 3.45, respectively.
However, the equilibria addition of hydroxide anions to
benzaldehydes in water at 25 ЊC had a ρ value equal to 2.233
or 2.8,34 whereas, the alkaline hydrolysis of ethyl or methyl
benzoates in water at 25 ЊC 35 and 40% aqueous dioxane at
20 ЊC 30 had ρ values equal to 1.3 and 2.1, respectively. Thus, the
ρ values observed here indicate that the negative charge in the
transition state must be developed close to the substituted
phenyl group a transition state close to 14 in Scheme 1, cf.
ref. 3.
out further purification. The solvents were carefully purified by
standard methods38 and stored as described previously.31
Measurements
Rate coefficients for the base-catalysed reactions were deter-
mined spectrophotometrically by use of a Perkin-Elmer lambda
16 UV–VIS spectrometer. A Haake thermostatted water circu-
lating bath was used to control the temperature of the cell to
±0.05 ЊC. The procedure was that described previously.39 The
reactions were followed at suitable wavelengths, as shown in
Table 1. These were normally those having the greatest differ-
ences between the 2,2-dihydroxy 1,3-diones and the products.
Rate coefficients were measured at least twice. The reactions
were strictly first order in the substrates. The ionic strength was
maintained at 0.1 mol dmϪ3 using sodium chloride. The sub-
strate concentration was 1.5 × 10Ϫ5–1.5 × 10Ϫ4 mol dmϪ3 and
the base concentrations 1.5 × 10Ϫ4–1 × 10Ϫ1 mol dmϪ3, at least a
ten-fold excess of base being used. The reactions were found to
be either zero order or first order in base, with due allowance for
that used in fully ionising the substrates. The same kinetics were
obtained if either the 2,2-dihydroxy 1,3-diones or 1,2,3-triones
were used as substrates as the latter were very rapidly converted
into the former on addition of base. Use of aqueous dioxane as
the reaction solvent was required due to the restricted solubility
of certain substrates in water.
Mechanistic pathway
Product analysis
The evidence indicates that the pathway for the base-catalysed
ring fission of the 2,2-hydroxy 1,3-diones is that shown in
Scheme 1. The rate-determining step for the ring fission process,
with a transition state close to the intermediate 7, appears
to be k1 in Scheme 1. The product-determining step, where
dichotomy can exist, would be the same as the latter. The
relative ease of the two types of pathways available for such
base-catalysed fission reactions, i.e. the intramoleclar nucleo-
philic attack as in Scheme 1, cf. ref. 21, and the benzilic acid
rearrangement, with ring contraction, as in Scheme 2, cf. ref.
The final products of the base-catalysed ring fission reactions
of the substituted 2,2-dihydroxyindane-1,3-diones were shown
to be quantitatively the dianions of the corresponding
o-carboxymandelic acids by isolation of the corresponding
lactones and UV spectral comparison with the product of
hydrolysis of the lactones. In general, the products of the kin-
etic runs or preparative studies were isolated by acidification
and extraction with diethyl ether. After isolation, the lactones
were recrystallised from toluene. The same procedures gave the
lactone derived from 2,2-dihydroxyphenalene-1,3-dione. The
products had either mps in good agreement with literature
values6,40 or are reported in Table 5. 1H and 13C NMR, IR and
mass spectral studies, as well as elemental analysis, confirmed
the stated structures and purity of the products. For the
5-substituted 2,2-dihydroxyindane-1,3-diones, the product is a
mixture of two isomers, i.e. as shown in Scheme 3. Before
recrystallisation as above, the relative compositions were
obtained by integrations of 1H NMR spectra using a JEOL
EX270, 270 MHz multinuclear FT instrument and the values of
ratio shown in Table 2 were found to be reproducible to ±5%.
36, can be considered. The switch is between
a 1,2-
intramolecular nucleophilic attack of an alkoxide anion on a
carbonyl group carbon and a 1,2-migration of an aroyl group
to a carbonyl group carbon. Obviously, there are important
stereochemical demands on the nucleophilic attack and
migration 37 which are more difficult to satisfy when the sys-
tems are constrained in a ring system. It would appear that
the stereochemistry of the systems studied here allows the
intramolecular attack to proceed from a favourable attack
angle, cf. ref. 37. The intramolecular rearrangement,3,4 follow-
ing the ring fission, for the system under study is a facile
process as noted for a range of intramolecular Cannizzaro-
type reactions, e.g. ref. 28.
Acknowledgements
We thank Dr A. G. Osborne for his kind and detailed help in
the interpretation of NMR spectra.
Experimental
Materials
References
The 2,2-dihydroxy 1,3-diones and the 1,2,3-triones were
prepared and/or purified as described previously.31 o-Carboxy-
phenylglyoxal was prepared by the ozonolysis of 1,4-naphtho-
quinone.13 Pure phenylglyoxal, mandelic and benzoic acids were
obtained commercially.
1 Part 22. K. Bowden and J. M. Byrne, J. Chem. Soc., Perkin Trans. 2,
1997, 123.
2 S. Selman and J. F. Eastham, Quart. Rev., 1960, 14, 221.
3 J. Hine and G. F. Koser, J. Org. Chem., 1971, 36, 3591.
4 D. L. Vander Jagt, L.-P. B. Han and C. H. Lehman, J. Org. Chem.,
1972, 37, 4100.
Inorganic salts were of analytical grade and were used with-
J. Chem. Soc., Perkin Trans. 2, 1997
987

View Article Online
5 H. L. Dao, F. Dayer, L. Duc, H. Rodé-Gowal and H. Dahn, Helv.
Chim. Acta, 1974, 57, 2215.
6 S. Ruhemann, J. Chem. Soc., 1910, 2025.
7 G. A. Melkonian and L. Holleck, Z. Electrochem., 1960, 64, 1210.
8 T. C. Bruice and F. M. Richards, J. Org. Chem., 1958, 23, 145.
9 G. B. Barlin and D. D. Perrin, Quart. Rev., 1966, 4, 1.
10 B. Lukats and O. Clauder, Acta Chim. (Budapest), 1972, 71, 339.
11 J. P. Kuebrich and R. L. Schowen, J. Am. Chem. Soc., 1971, 93, 1220.
12 H. Kwart and M. B. Baevsky, J. Am. Chem. Soc., 1958, 80, 580.
13 E. Bernatek, Tetrahedron, 1958, 4, 213.
14 C. D. Johnson, The Hammett Equation, Cambridge University
Press, Cambridge, 1973.
15 R. Wegscheider, Z. Phys. Chem., 1899, 30, 593.
16 O. Exner, Collect. Czech., Chem. Commun., 1961, 26, 1.
17 K. Bowden and M. J. Price, J. Chem. Soc. (B), 1971, 1784.
18 K. Bowden, Can. J. Chem., 1963, 41, 2781.
26 K. Bowden and M. J. Price, J. Chem. Soc. (B), 1971, 1784.
27 K. Wiberg, Physical Organic Chemistry, Wiley, New York, 1964.
28 M. R. Abbaszadeh and K. Bowden, J. Chem. Soc., Perkin Trans. 2,
1990, 2081.
29 F. H. Westheimer, J. Org. Chem., 1936, 1, 93.
30 H. H. Jaffé, J. Am. Chem. Soc., 1954, 76, 4261.
31 K. Bowden and S. Rumpal, J. Chem. Res., 1977, 35 (S), 0355 (M ) .
32 K. Bowden, Org. React. (Tartu), 1995, 29, 19.
33 P. Greenzaid, J. Org. Chem., 1973, 38, 3164.
34 W. J. Bover and P. Zuman, J. Chem. Soc., Perkin Trans. 2, 1973, 786.
35 M. Hojo, M. Utaka and Z. Yoshida, Tetrahedron Lett., 1966, 19, 25.
36 A. Al-Najjar, K. Bowden and M. V. Horri, J. Chem. Soc., Perkin
Trans. 2, 1997, 993.
37 P. Deslongchamps, Stereoelectronic Effects in Organic Chemistry,
Pergamon Press, Oxford, 1983; H. B. Burgi, J. D. Dunitz and
E. Shefter, J. Am. Chem. Soc., 1973, 95, 5065.
19 V. Balasubramiyan, Chem. Rev., 1966, 66, 567.
20 K. Bowden and A. Brownhill, J. Chem. Soc., Perkin Trans. 2, 1997,
997.
21 K. Bowden and M. V. Horri, J. Chem. Soc., Perkin Trans. 2, 1997,
989.
38 D. D. Perrin and W. L. F. Armarego, Purification of Laboratory
Chemicals, 3rd edn., Pergamon Press, Oxford, 1988.
39 K. Bowden and A. M. Last, J. Chem. Soc., Perkin Trans. 2, 1973,
345.
40 A. R. Miller, J. Org. Chem., 1979, 44, 1931.
22 J. Hine and H. W. Haworth, J. Am. Chem. Soc., 1958, 80, 2274.
23 K. Bowden and G. R. Taylor, J. Chem. Soc. (B), 1971, 149.
24 C. A. Bunton and V. J. Shiner, J. Am. Chem. Soc., 1961, 83, 3207;
3214.
25 E. S. Amis, Solvent Effects on Reaction Rates and Mechanism,
Academic Press, New York, 1966.
Paper 6/06312H
Received 13th September 1996
Accepted 23rd December 1996
988
J. Chem. Soc., Perkin Trans. 2, 1997