Radical formation in the oxidation of 2,2′-azo-2-methyl-6-heptene by thianthrene cation radical

Article abstract of DOI:10.1021/jo9601371

Reaction of 2,2′-azo-2-methyl-6-heptene (1) with thianthrene cation radical perchlorate (Th^?+ClO₄^-) in CH₂Cl₂ solution containing 2,6-di-tert-butyl-4-methylpyridine (DTBMP) gave a mixture of nine C₈ hydrocarbons, namely, 1,1,2-trimethylcyclopentane (4, 2.2%), 6-methyl-1-heptene (5, 2.2%), 2-methyl-1,6-heptadiene (6, 9.8%), 2,2-dimethyl-1-methylenecyclopentane (7, 2.9%), 6-methyl-1,5-heptadiene (8, 39%), 3,3-dimethyl- (9, 7.6%), 4,4-dimethyl- (10, 11%), 1,2-dimethyl- (11, 5.4%), and 1,6-dimethylcyclohexene (12, 1.5%). The amounts of acyclic dienes (6, 8) fell and of cyclohexenes (9, 10) rose when DTBMP was omitted from or diminished in the solution. The results provide firm evidence (products 4, 5, and 7) for the formation of the 2-methyl-6-hepten-2-yl radical (2), although the major fate of 2 is its oxidation to the corresponding cation 13, the origin of the bulk of the other products.

Full text of DOI:10.1021/jo9601371

4716
J . Org. Chem. 1996, 61, 4716-4719
Ra d ica l F or m a tion in th e Oxid a tion of 2,2′-Azo-2-m eth yl-6-h ep ten e
by Th ia n th r en e Ca tion Ra d ica l
Tonghua Chen and Henry J . Shine*
Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409
Received J anuary 22, 1996X
Reaction of 2,2′-azo-2-methyl-6-heptene (1) with thianthrene cation radical perchlorate (Th•+ClO4
)
-
in CH2Cl2 solution containing 2,6-di-tert-butyl-4-methylpyridine (DTBMP) gave a mixture of nine
C8 hydrocarbons, namely, 1,1,2-trimethylcyclopentane (4, 2.2%), 6-methyl-1-heptene (5, 2.2%),
2-methyl-1,6-heptadiene (6, 9.8%), 2,2-dimethyl-1-methylenecyclopentane (7, 2.9%), 6-methyl-1,5-
heptadiene (8, 39%), 3,3-dimethyl- (9, 7.6%), 4,4-dimethyl- (10, 11%), 1,2-dimethyl- (11, 5.4%), and
1,6-dimethylcyclohexene (12, 1.5%). The amounts of acyclic dienes (6, 8) fell and of cyclohexenes
(9, 10) rose when DTBMP was omitted from or diminished in the solution. The results provide
firm evidence (products 4, 5, and 7) for the formation of the 2-methyl-6-hepten-2-yl radical (2),
although the major fate of 2 is its oxidation to the corresponding cation 13, the origin of the bulk
of the other products.
The facile oxidative decomposition of azoalkanes was
ylpropane (azoisobutane) and 9,10-dicyanoanthracene
(DCA) in acetonitrile and methanol solutions gave prod-
ucts attributable to the formation of tBu• and its trapping
by DCA•-.
Recently, Walborsky and co-workers reported the
preparation and photolysis of 2,2′-azo-2-methyl-6-heptene
(1).8 The objective in the photolysis was to generate and
explore the fate of the 2-methyl-6-hepten-2-yl radical (2),
which is known to cyclize readily to the (2,2-dimethyl-
cyclopentyl)methyl radical (3, eq 1).9 Photolysis of a
first reported in the reaction of 1,1′-azoadamantane
(AdNdNAd) with thianthrene cation radical perchlorate
(Th•+ClO4-).1 Most (91%) of the adamantyl groups in the
AdNdNAd were converted by two-electron oxidation into
the adamantyl cation (Ad+), trapped subsequently, for
example, by the solvent acetonitrile. Circumstantial
evidence for the formation of the adamantyl radical (Ad•)
was adduced for the small amount (0.2%) of adamantane
and larger amount (5.5%) of adamantyl methyl ketone
that were obtained. In the same year, one-electron
transfer to solvent CCl4 was attributed to the photolytic
decomposition of cyclopropyl-substituted 2,3-diazabicyclo-
[2.2.2]oct-2-enes.2 Attempts to obtain further evidence
for the initial formation of alkyl radicals in the oxidation
of azoalkanes by Th•+, with the use of 1,4-diphenyl-
azomethane3 and 1,1′-azo-5-hexene,4 were thwarted by
the tautomerization of the azoalkane to the corresponding
hydrazone. In the case of 1,4-diphenylazomethane,
oxidative cycloaddition of the hydrazone, namely ben-
zaldehyde benzylhydrazone, to solvent acetonitrile oc-
curred and led to 1-benzyl-3-phenyl-5-methyl-1,2,4-
triazole. The anticipated formation of benzyl radicals
was not achieved. These initial reports were followed by
a number of others, particularly on the reactions of
diazabicycloalkenes.5,6 In these cases, one-electron oxi-
dation led to deazatization and the formation of the cation
radical of the corresponding cycloalkene or bicylcloalkane.
Here, radical formation was deducible in the sense that
the radical was part of a hydrocarbon cation radical,
identifiable indirectly from its chemistry or directly with
ESR spectroscopy. More concrete evidence for the forma-
tion of free alkyl radicals was provided by Zona and
Goodman.7 Irradiation of solutions of 2,2′-azo-2-meth-
dilute solution of 1 in ether solution gave three major
products, 1,1,2-trimethylcyclopentane (4, 43%), 6-methyl-
1-heptene (5, 26%), and 2-methyl-1,6-heptadiene (6, 22%)
(Scheme 1). These products were attributed reasonably
to the cyclization (for 4) and disproportionation (for 5 and
6) of radical 2. Formation of 2,2-dimethyl-1-methyl-
enecyclopentane (7), which would result from dispropor-
tionation of 3, was not reported.
We have now turned to the use of 1 for seeking further
evidence for radical formation in oxidations by Th•+
.
Resu lts a n d Discu ssion
Oxidation of 1 by Th•+ in CH2Cl2 solution was carried
out by dropwise addition of a solution of 1, 2,6-di-tert-
butyl-4-methylpyridine (DTBMP), and nonane (GC stan-
dard) to a stirred suspension of Th•+ClO4-. Gas chro-
matographic (GC) analysis of the solution, after addition
of a small amount of aqueous K2CO3, yielded nine
identifiable C8 hydrocarbons, namely, 4-7, 6-methyl-1,5-
heptadiene (8), 3,3-dimethylcyclohexene (9), 4,4-dimeth-
ylcyclohexene (10), 1,2-dimethylcyclohexene (11), and 1,6-
dimethylcyclohexene (12) (Scheme 2). The amounts of
these products, totaling 82% of the available hydrocarbon
X Abstract published in Advance ACS Abstracts, J une 15, 1996.
(1) Bae, D. H.; Engel, P. S.; Hoque, A. K. M. M.; Keys, D. E.; Lee,
W.-K.; Shaw, R. W.; Shine, H. J . J . Am. Chem. Soc. 1985, 107, 2561.
(2) Engel, P. S.; Keys, D. E.; Kitamura, A. J . Am. Chem. Soc. 1985,
107, 4964.
(3) Hoque, A. K. M. M.; Kovelesky, A. C.; Lee, W.-K.; Shine, H. J .
Tetrahedron Lett. 1985, 26, 5655.
(4) Unpublished work in these laboratories.
(5) (a) Adam, W.; Do¨rr, M. J . Am. Chem. Soc. 1987, 109, 1570. (b)
Adam, W.; Sahin, C.; Sendebach, J .; Walter, H.; Chen, G.-F.; Williams,
F. J . Am. Chem. Soc. 1994, 116, 2576 and earlier papers cited therein.
(6) Zona, T. A.; Goodman, J . L. J . Am. Chem. Soc. 1995, 117, 5879
and earlier papers.
(7) Zona, T. A.; Goodman, J . L. Tetrahedron Lett. 1992, 33, 6093.
(8) Walborsky, H. M.; Topolski, M.; Hamdouchi, C.; Pankowski, J .
J . Org. Chem. 1992, 57, 6188.
(9) Chatgilialoglu, C.; Dickhaut, J .; Giese, B. J . Org. Chem. 1991,
56, 6399 and earlier references therein.
S0022-3263(96)00137-5 CCC: $12.00 © 1996 American Chemical Society

Radical Formation in Oxidation
J . Org. Chem., Vol. 61, No. 14, 1996 4717
Sch em e 1
Radical 2 has served as a radical clock9 and also as a
radical probe in a number of diverse reactions. The
products that may be expected from 2 are, therefore, well-
recorded in the literature. Thus, Chatgilialoglu and co-
workers, in reactions of 6-bromo-6-methyl-1-heptene (14)
with (Me3Si)3SiH obtained 4 and 5 (in relative amounts
that varied with the concentration of (Me3Si)3SiH and
1,1-dimethylcyclohexane (15).9 The last product 15,
whose yield was not given, arose evidently from the less
common endo-trig cyclization of 2. The same products
were reported by Ashby and co-workers in the amounts
68%, 11.8%, and 7.3% in the investigation of the Grignard
reagent made from 6-chloro-6-methyl-1-heptene (16).11 In
the reactions of 2 in CCl4, Giese and Hartung12 obtained
as major products 16 and 1-(chloromethyl)-2,2-dimeth-
ylcyclopentane, corresponding with chlorine abstraction
by 2 and by 3. Only a minor amount of 1-chloro-3,3-
dimethylcyclohexane, the product that would follow from
endo-trig cyclization of 2, was obtained. Toi and co-
workers,13 from reaction of 16 with Bu3SnH, obtained not
only 4 (40%), 5 (50%), and 15 (5%) but also 8 (5%). Other
workers, in various reactions, on the other hand, were
able either to trap or identify only the radicals 2 and
3.14-16
Sch em e 2
Ta ble 1. P r od u cts of Rea ction of
2,2′-Azo-2-m eth yl-6-h ep ten e (1) w ith Th •+ClO4
-
In contrast with 2, information in the literature on 13
is sparse. The kinetics but not the products of solvolysis
of 16 in 80% ethanol have been reported.17 The only work
with the chemistry of 13 that we have been able to find
is by Toi and co-workers.13 Reduction of 16 by the ate
complex prepared from B-butyl-9-borabicyclo[3.3.1]nonane
and butyllithium gave 33% of 5, 7% each of 8 and 15,
and 3.4% of 6. None of 4 was obtained, signifying13 that
in that reaction of 16, 13 rather than 2 was involved.
From our perspective, the sum of the results in the
literature is that 2 will cyclize preferentially to 3 as
expected, but also in small amounts, by the endo-trig
route, to the 3,3-dimethylcyclohexyl radical (17). The
amounts of the latter may be small enough to be
overlooked or missed. On the other hand, there is no
evidence in the (sparse) literature on 13 for its cyclization
to anything but the 3,3-dimethylcyclohexyl cation (18).
Our results are discussed, therefore, on the basis that
none of our products 4 and 7 came from 13 and that we
can ignore the amount of endo-trig cyclization (17) that
may have contributed to the several cyclohexenes, 9-12.
Compounds 4, 5, and 7 are certainly derived from
radical 2. Compounds 9-12 are almost as certainly
derived from the corresponding cation (13). Walborsky
found approximately equal amounts of 5 and 6, whereas
we have not only about five times more 6 than 5 but also
large amounts of 8 (which was not obtained by Walbor-
products mmola and %b
run
4
5
6
7
8
9
10
11
12 Th ThO
1
2
3
4
3.72 3.86 16.8 4.62 68.0 13.2 19.2 9.69 2.43 182 2.9
3.69 3.91 16.9 5.24 67.2 13.3 19.1 9.43 2.57 180 3.1
3.71 3.75 16.4 5.23 64.7 12.5 18.2 9.11 2.59 179 4.8
3.88 3.18 16.6 4.82 66.1 13.1 18.9 8.43 2.52 176 4.1
avc 3.75 3.67 16.8 4.98 66.5 13.0 18.9 9.17 2.53 179 3.7
2.2 2.2
9.8 2.9 39
3.69 8.05 38.7 54.0 11.0 2.67 161 6.7
2.3 5.1 24 34 6.9 1.7 96 4.0
7.6 11
5.4 1.5
98 2.2
5d 3.63 1.30 tr
2.3 0.82
6e 3.54 1.07 0.54 2.24 15.0 30.2 42.5 13.4 3.11 177 9.6
2.2 0.67 0.34 1.4
9.4 19
27
8.4 1.9
95 5.1
a
The yield of each product (mmol) is an average of 10 or more
b
GC measurements. Entries in rows 6, 8, and 10. The percentage
is based on millimoles of C8 groups in 1 after compensation for
recovered 1. c Average of runs 1-4. Standard deviation in the
order 4-12 was 0.088, 0.34, 0.12, 0.31, 1.43, 0.40, 0.42, 0.071. In
each run, 85.5 × 10-3 mmol of 1, 312 × 10-3 mmol of DTBMP,
and GC standard in 1 mL of CH2Cl2 was added dropwise to a
stirred suspension of 183 × 10-3 mmol of Th•+ClO4 in 1 mL of
-
CH2Cl2. 79.5 × 10-3 mmol of 1, 141 × 10-3 mmol of DTBMP and
d
167 × 10-3 mmol of Th•+ClO4
.
e 80.2 × 10-3 mmol of 1, no
-
DTBMP, and 187 × 10-3 mmol of Th•+ClO4
.
-
groups in 1, are listed in Table 1. Small amounts of other
hydrocarbon products were formed but were not identi-
fied. Also, GC traces and GC/MS data suggested that
some radicals had been trapped by Th•+ to form 1- and
2-substituted thianthrenes, a reaction that has been
observed in other work with Th•+ 10
No attempt was
.
made to identify and assay these products.
(12) Giese, B.; Hartung, J . Chem. Ber. 1992, 125, 1777.
(13) Toi, H.; Yamamoto, Y.; Sonoda, A.; Murahashi, S.-I. Tetrahedron
1981, 37, 2261.
(14) Lusztyk, J .; Maillard, B.; Deycard, S.; Lindsay, D. A.; Ingold,
C. K. J . Org. Chem 1987, 52, 3509.
(15) Tanaka, J .; Nojima, M.; Kusabayashi, S. J . Am. Chem. Soc.
1987, 109, 3391.
Oxidation of 1 by Th•+ must lead initially to 1•+, which
we treat as next decomposing into the radical 2 and the
corresponding cation 13 (eqs 2 and 3). The products
4-12 are derived, then, from 2 and 13.
(16) Santiago, A. N.; Rossi, R. A. J . Chem. Soc., Chem. Commun.
1990, 206.
(17) Orlovic, M.; Borcic, S.; Humski, K.; Kronja, O.; Imper, V.; Polla,
E.; Shiner, V. J ., J r. J . Org. Chem. 1991, 56, 1874.
(10) Lochynski, S.; Shine, H. J .; Soroka, M.; Venkatachalam, T. K.
J . Org. Chem. 1990, 55, 2702.
(11) Ashby, E. C.; Oswald, J . J . Org. Chem. 1988, 53, 6068.

4718 J . Org. Chem., Vol. 61, No. 14, 1996
Chen and Shine
Sch em e 3
The origin of products 4 and 7 is certainly the cyclization
of radical 2, evidence for which we were seeking. Our
data show on the other hand that if 2 and 13 are formed
in the initial cleavage of 1•+, most of the 2 is next oxidized
by the relatively large excess of Th•+ to 13. This finding
is analogous to that with the oxidation of azo-tert-octane,
in which products of the 2-methyl-2-heptyl cation were
dominant.18 In the present work, more of 8 than 6 was
obtained, as would be expected from 13. More of 10 was
obtained (from 18 and 19) than 9 (from 18 and 20).
Finally, as would be expected, more of 11 than 12 was
formed from 21. We searched for but could not find 15
among our products.
In conclusion, the formation of an alkyl radical (here,
2) from cation-radical oxidation of an azoalkane (here,
1) has been certified.
Exp er im en ta l Section
Dichloromethane, dimethyl sulfoxide (DMSO), hexameth-
ylphosphordiamide (HMPA), and triethylamine (Et3N) were
distilled from CaH2. Tetrahydrofuran (THF) was distilled from
sodium benzophenone ketyl. Dimethylformamide (DMF) was
distilled from CaH2 under reduced pressure. Diethyl ether was
distilled from LiAlH4. 1H and 13 C NMR spectra were recorded
with a 200 MHz Bruker spectrometer with CDCl3 solvent
unless noted otherwise. GC/MS analyses were made with a
Hewlett-Packard instrument, model 5988A and a Supelco
SEP-5 capillary column, 30 m × 0.32 mm. GC analyses of
product mixtures were made with a Varian model 3700 gas
chromatograph attached to a Spectra Physics model 4290
integrator. Two capillary columns were used: Supelco SE-54
and SPB-20, each 30 m × 0.25 mm, and 0.25 µm film thickness.
The SE-54 was used for all analyses, while the SPB-20 was
used only for 6 and 9 which were inseparable on the SE-54
column. Each column was held initially at 36 °C for 4 min
and was programmed for 12 °C/min increase until 250 °C. The
injector and FID detector were held at 250 °C.
1,1,2-Trimethylcyclopentane (4) was purchased from the
API inventory at Carnegie Institute of Technology. 6-Methyl-
1-heptene (5), 6-methyl-1,5-heptadiene (8), 4,4- (10), 1,2- (11),
and 1,6-dimethylcyclohexene (12) were purchased from Wiley
Organics. A sample of 8 was also initially donated by Professor
G. A. Molander. 1,1-Dimethylcyclohexane (15) and 1,3-di-
methylcyclohexene, which were sought but not found among
the products of reaction, were also purchased from Wiley
Organics. Compounds 6, 7, and 9 were prepared as described
later. All other reagents were purchased from Aldrich Chemi-
cal Company.
2-Meth yl-1,6-h ep ta d ien e (6) was prepared essentially as
described by Walborsky8 from 6-h ep ten -2-on e, with the
exception that the ylide Ph3PdCH2 was prepared in DMSO
from the reaction of methyltriphenylphosphonium bromide
with NaH.19 After chromatographic purification of the pentane
solution of 6 by passage through a silica gel column, the 6 was
distilled through a small Vigreux column and had the same
1H NMR properties as described.8
6-Hep ten -2-on e. 4-Pentenyl 1-mesylate was obtained as
an oil from reaction of 4-penten-1-ol with methanesulfonyl
chloride in CH2Cl2 containing Et3N.20 The mesylate was
converted into 4-pentene-1-nitrile as follows. A solution of 11.7
g (0.239 mol) of NaCN in DMSO was heated to 90 °C. To the
solution was added 4-pentenyl 1-mesylate (32.0 g, 0.195 mol)
over a period of 15 min at such a rate that the temperature
did not exceed 150 °C. Stirring was continued without heating
for 5 h. The mixture was poured into water, and the product
was extracted with 4 × 50 mL of pentane. The pentane
sky). It is apparent, then, that most of 6 and 8 must
have come from 13. Thus, if we allow for obtaining equal
amounts of 5 and 6 from disproportionation of 2, the
remaining amounts of 6 and 8 can be assigned to
deprotonation of 13. The summation is that about 10%
of the products is attributable to 2 and the remainder to
13. The formation of products from 13 is shown in
Scheme 3. It appears that either cyclization of 2, in spite
of its rapid rate (106 s-1),9 does not compete well with
oxidation by an excess of Th•+, or that two-electron
oxidation of 1 prevails before 1•+ can fragment. Ready
oxidation of the tertiary radical 2 to the tertiary cation
13 is understandable and is a built-in liability of using a
branched azoalkane in order to avoid its tautomerization
to a hydrazone. Our work nevertheless shows the
formation of and survival of the radical 2, albeit in the
minor reaction pathway.
Walborsky found approximately equal amounts of 5
and 6 and attributed them to disproportionation of 2.
None of 7 and 8 was reported by Walborsky, so that the
ratio of the amounts of products 4/(5 + 6) that were
obtained from a dilute solution of 1 was 0.9.8 In our work
(runs 1-4), if we assume that an amount of 6, by
disproportionation of 2, equal to that of 5 was formed,
the ratio of amounts of cyclic to acyclic, radical-derived
products, (4 + 7)/(2 × 5), is 1.2, not far from that of
Walborsky. Our major product was 8, consistent with
deprotonation of 13. We assume also that the larger
portion (7.6%) of 6 came from 13, although some may
have formed from disproportionation of radical 2, too. The
cyclic products 9-12 have their origin in the cyclization
of 13, as shown in Scheme 3. Among these products are
11 and 12, whose formation must have been preceded
by hydride and methyl rearrangements. When reaction
was carried out in the presence of a smaller amount of
base (run 5) and in the absence of base (run 6), the
distribution of some products changed considerably. The
amounts of acyclic dienes (6 and 8) fell and the amounts
of cyclohexenes rose, particularly of products 9 and 10.
Assuming that an amount of 6 equal to that of 5 would
be formed in disproportionation of radical 2, the sum (8
+ 6 - 5) falls from nearly 47% in runs 1-4 to nearly 4%
and 9% in runs 5 and 6, while correspondingly, the sum
of 9-12 rises from nearly 26% to nearly 67% and 56%.
The data point to competition in deprotonation and
cyclization of the cation 13, cyclization becoming domi-
nant when the concentration of DTBMP was diminished.
(18) Engel, P. S.; Robertson, D. T.; Scholz, J . N.; Shine, H. J . J . Org.
Chem. 1992, 57, 6178.
(19) Kesselmans, R. P. W.; Wijnberg, J . B. P. A.; Minnaard, A. J .;
Walinga, R. E.; deGroot, A. J . Org. Chem. 1991, 56, 7237.
(20) J ones, D. N.; Hill, D. R.; Lewton, D. A.; Sheppard, C. J . Chem.
Soc., Perkin Trans 1. 1977, 1574.

Radical Formation in Oxidation
J . Org. Chem., Vol. 61, No. 14, 1996 4719
solution was washed with brine and dried over MgSO4.
Fractional distillation gave 15.3 g (0.161 mol, 83%) of 4-pen-
tene-1-nitrile, bp 156-160 °C, having a satisfactory H NMR
3,3-Dim eth ylcycloh exen e (9) was obtained as a mixture
with 4,4-dimethylcyclohexene (10) by decomposition of 3,3-
dimethylcyclohexyl 1-tosylate on the SPB-20 column. With
authentic 10 at hand, it was possible to assign a retention time
to its isomer 9, and by assuming that 9 and 10 have the same
Rf, their relative yields of 41:59 were obtained. Isolation of 9
was not attempted. Distillation of 3,3-dimethylcyclohexanol
from p-toluenesulfonic acid has been reported to give 9 and
10 in the ratio 35:65.28
3,3-Dim eth ylcycloh exyl 1-Tosyla te. 3,3-Dimethylcyclo-
hexanone was prepared by reaction of 3-methyl-2-cyclohex-
enone with Me2CuMgBr as described by Pelletier and Mody
with use of Cu2MeLi.29 Me2CuMgBr was prepared from CH3-
MgI (12.6 g CH3I, 2.16 g Mg in 100 mL of ether) and a
CuBrMe2S complex (7.73 g, 37.6 mmol) at -78 °C. Workup
gave 3.2 g (25.4 mmol, 70%) of 3,3-dimethylcyclohexanone, bp
174-175 °C (lit.29 bp 58-60 °C/15 Torr), having a satisfactory
1H NMR spectrum. The ketone was reduced with LiAlH4 to
3,3-dimethylcyclohexanol and this (230 mg, 1.81 mmol) was
converted into the tosylate with 476 mg (2.50 mmol) of
p-toluenesulfonyl chloride and 3.0 g (38 mmol) of pyridine
according to the general procedure of Bartsch and Bunnett.30
The product was not distilled and had 1H NMR peaks at δ
0.80 (s, 3H), 0.89 (s, 3H), 1.09-1.60 (m, 8H), 2.42 (s, 3H), 4.48-
4.63 (m, 1H), 7.28-7.35 (m, 2H), 7.74-7.83 (m, 2H).
1
spectrum.21 Other workers have reported the preparation from
5-bromo-1-pentene, bp 59 °C/19 Torr21 and bp 160-162 °C.22
Hydrolysis of the nitrile was achieved by refluxing it (7.65 g,
80.5 mmol) for 15 h in a solution of 6.5 g of NaOH in 20 mL of
water. Acidification with 9 mL of 50% H2SO4 and 10 mL of
water gave 5-hexenoic acid as an oil. This was extracted with
ether. Fractional distillation gave 6.0 g (52.6 mmol, 65%), bp
200-201 °C, having a satisfactory 1H NMR spectrum.23
Earlier preparations have been reported by oxidation of
5-hexen-1-ol22 and from butenylmalonic acid, bp 103 °C/12
Torr.24 5-Hexenoic acid (3.42 g, 30 mmol) in 50 mL of THF
was converted into 6-hepten-2-one by reaction with MeLi (90
mmol) using the general procedure of Rubottom and Kim.25
The product (2.76 g, 24.6 mmol, 82%) had bp 141-142 °C and
1
a satisfactory H NMR spectrum.26
2,2-Dim eth yl-1-m eth ylen ecyclop en ta n e (7) was pre-
pared in 61% yield from 2,2-dimethylcyclopentanone as de-
1
scribed by Barfield and co-workers and had a satisfactory H
NMR spectrum.27
(21) deRaadt, A.; Klempier, N.; Faber, K.; Griengl, H. J . Chem. Soc.,
Perkin Trans 1 1992, 137.
(22) Abd El Samii, Z. K. M.; Ashmawy, M. I. A.; Mellor, J . M. J .
Chem. Soc., Perkin Trans. 1 1988, 2523.
(23) Parry, R. J .; J u, S.; Baker, B. J . J . Labelled Compd. Radio-
pharm. 1991, 47, 633.
(24) Linstead, R. P.; Rydon, H. N. J . Chem. Soc. 1934, 1995.
(25) Rubottom, G. M.; Kim, C. J . Org. Chem. 1983, 48, 1550.
(26) Molander, G. A.; McKie, J . A. J . Org. Chem. 1992, 57, 3132.
(27) Barfield, M.; Dean, A. M.; Fallick, C. J .; Spear, R. J .; Sternhell,
S.; Westman, P. W. J . Am. Chem. Soc. 1975, 97, 1482.
Ack n ow led gm en t. We thank the Robert A. Welch
Foundation for support (Grant D-028).
J O9601371
(28) Onopchenko, A.; Schulz, J . G. D. J . Org. Chem. 1975, 40, 3338.
(29) Pelletier, S. W.; Mody, N. V. J . Org. Chem. 1976, 41, 1069.
(30) Bartsch, R. A.; Bunnett, J . F. J . Am. Chem. Soc. 1969, 91, 1376.