Oxidative ring cleavage of 2-nitrocycloalkanones: Synthesis and radical-induced transformations of methyl ω,ω-dihalo-ω-nitroalkanoates

Full text of DOI:10.1021/jo960488f

5652
J . Org. Chem. 1996, 61, 5652-5655
Sch em e 1
Oxid a tive Rin g Clea va ge of
2-Nitr ocycloa lk a n on es: Syn th esis a n d
Ra d ica l-In d u ced Tr a n sfor m a tion s of
Meth yl ω,ω-Dih a lo-ω-n itr oa lk a n oa tes
Roberto Ballini, Marino Petrini,* and Olga Polimanti
Dipartimento di Scienze Chimiche, Universita` di Camerino,
via S. Agostino, 1, I-62032 Camerino, Italy
Received March 11, 1996
Ring cleavage often represents a particularly effective
route to R,ω-difunctionalized frameworks. In this context
2-nitrocycloalkanones1 are able to produce a consistent
array of functionalized molecules through an easy nucleo-
philic retro-Claisen condensation.2 Since 2-nitrocyclo-
alkanones are readily available from the corresponding
ketones or olefins by several nitrating processes,3 these
substrates are profitable precursors in many synthetic
procedures. The utilization of a nucleophile-oxidizing
agent couple allows the tandem ring cleavage-oxidation
of the nitro function, thus affording dicarboxylic acids.4
Basic solutions of hypohalite salts induce the oxidative
demolition of R,R′-keto dinitronates to give R,ω-dinitro-
R,R,ω,ω-tetrahaloalkanes.5 The widespread interest in
halogenated nitro compounds mainly stems from their
recognized antimicrobial and insecticide activities.6 Re-
cently a direct synthesis of dichloronitro ketones starting
from trichloronitromethane has been devised.7
Sch em e 2
In this context 2-nitrocycloalkanones 1 can be ef-
ficiently cleaved at room temperature by employing basic
solutions of sodium hypochlorite, leading to the corre-
sponding ω,ω-dichloro-ω-nitroalkanoic acids. These acids
can be directly converted into their methyl esters with
the use of methanol in the presence of Amberlyst 15 ion
exchange resin (Scheme 1).8 The double halogenation
process can be rationalized by taking into account the
ease of addition of hypohalite ion to nitronates.9 Chloro-
nitrocycloalkanone 5 is readily cleaved because of the
enhanced ability of the R-chloronitro moiety to act as a
leaving group. Chlorination of the resulting R-chloro-
nitronate anion 6 leads to the dichloronitro compound
2b after an acid catalyzed methyl esterification (Scheme
Ta ble 1. Rin g Clea va ge a n d Den itr a tion of
2-Nitr ocycloa lk a n on es (1)
cleavage product
denitration product
entry
substrate 1
2 yield %a
3 yield %a
1
2
3
4
5
6
7
8
a
b
c
d
e
f
75 (70)
85 (75)
65 (68)
71 (65)
70 (70)
78 (71)
(80)
78
82
70
75
77
70
85
65
g
h
(72)
a
Yields of pure, isolated products. Yields in parentheses refer
to method B (see Experimental Section).
2).10 A variety of 2-nitrocycloalkanones are cleaved in
respectable yield regardless the ring size (Table 1). The
so-called two-step transformation can be avoided by using
an alternative procedure that uses NCS as chlorinating
agent. In this case sodium methoxide is used as a base,
directly affording the corresponding open chain esters 2.
This process is particularly effective for the ring opening
of 2-nitrotetralone and derivatives since the Amberlyst
15 method to carry out the methyl esterification is scantly
efficient with benzoic acids (Scheme 3).8
(1) Reviews: (a) Rosini, G.; Ballini, R.; Petrini, M.; Marotta, E.;
Righi, P. Org. Prep. Proc. Int. 1990, 22, 707. (b) Fischer, R. H.; Weitz,
H. M. Synthesis 1980, 261.
(2) For some recent examples see: (a) Ballini, R.; Bartoli, G.;
Giovannini, R.; Marcantoni, E.; Petrini, M. Tetrahedron Lett. 1993,
34, 3301. (b) Ballini, R.; Petrini, M.; Polzonetti, V. Synthesis 1992, 355.
(c) Ballini, R.; Petrini, M.; Rosini, G. Tetrahedron 1990, 46, 7531.
(3) (a) Rathore, R.; Lin, Z.; Kochi, J . K. Tetrahedron Lett. 1993, 34,
1859. For a complete mechanistic study of this procedure see: Rathore,
R.; Kochi, J . K. J . Org. Chem. 1996, 61, 627. (b) Venkat Ram Reddy,
M.; Kumareswaran, R.; Vankar, Y. D. Tetrahedron Lett. 1995, 36, 7149.
(c) Dampawan, P.; Zajac, W. W. Synthesis 1983, 545. (d) Ballini, R.;
Sorrenti, P. Org. Prep. Proc. Int. 1984, 16, 289.
(4) Ballini, R.; Marcantoni, E.; Petrini, M.; Rosini, G. Synthesis 1988,
915.
(5) Feuer, H.; Shepherd, J . W.; Savides, C. J . Am. Chem. Soc. 1956,
78, 4364.
Compounds 2 generated by this methodology may
represent an attractive class of substrates since the
presence of three functional groups on the same carbon
atom foretells potentially useful synthetic applications.
Chlorine atoms as well as nitro groups are usually
(6) Metcalf, R. L. Organic Insecticides: Their Chemistry and Mode
of Action; Interscience: New York, 1955; p 134.
(7) Demir, A. S.; Tanyeli, C.; Aksoy, H.; Gulbeyaz, V.; Mahasneh,
A. S. Synthesis 1995, 1071.
(8) Petrini, M.; Ballini, R.; Marcantoni, E.; Rosini, G. Synth.
Commun. 1988, 18, 847.
(9) Nielsen, A. T. The Chemistry of the Nitro and Nitroso Groups;
Feuer, H., Ed.; J ohn Wiley and Sons, Inc.: New York, 1969; p 393.
(10) Similar results can be obtained with 2-(phenylsulfonyl)cycloal-
kanones but monochlorinated phenylsulfonyl derivatives are obtained
in this instance since the open chain R-chlorophenyl sulfone is less
prone to chlorination: Sholtz, D. Liebigs Ann. Chem. 1984, 264.
S0022-3263(96)00488-4 CCC: $12.00 © 1996 American Chemical Society

Notes
J . Org. Chem., Vol. 61, No. 16, 1996 5653
Ta ble 2. Allyla tion of ω,ω-Dich lor o-ω-n itr o Ester s (2)
Sch em e 3
w ith Allyltr ibu tyltin
nitro
ester 2
product 7
entry
yield %a
1
2
3
4
b
d
g
h
68
62
70
68
a
Yields of pure, isolated products.
Sch em e 5
Sch em e 4
enhanced using electron-rich alkenes.11 However, at-
tempts to add chloronitro ester 2b to butyl vinyl ether
by standard conditions (Bu3SnH, AIBN, benzene at
reflux), gave a rather unclean mixture of products in
which the denitrated compound 3b predominated. This
clearly means that the reductive process is faster than
the addition of the dichloro radical to the olefin. Frag-
mentation processes, which avoid the use of hydride
donors in radical reactions, could be of some benefit for
our purposes.14 Allylation can be successfully performed
with the use of allyltin derivatives that have been proved
to be about 10-fold more reactive than ordinary alkenes.15
R-Chloro-R-nitro compounds have been converted by Ono
et al. into the corresponding allyl derivatives through a
selective removal of the halogen atom by using allyl-
tributyltin and AIBN as radical initiator.16 The same
process conducted on compounds 2 shows a completely
different pattern since in this case the nitro group is
substituted by the allyl framework, giving the products
7. Allylation is best conducted in toluene at reflux with
the use of 2 equiv of tin derivative and AIBN as initiator
(Table 2). The yields of this reaction are modest, and
therefore we attempted to improve them by using differ-
ent allyltin derivatives as shown in Scheme 5. Triph-
enylallyltin gives comparable results to that obtained
with the tributyl derivative but only after prolonged
reaction times. Trimethylallyltin is able to slightly
improve the yield of the allylated product but this reagent
is much more expensive than the butyl one and further-
more its preparation is more difficult to carry out.
A similar procedure used for the preparation of nitro
derivatives 2 (Br2, NaOH, H2O) can be adopted for the
oxidative bromination of compounds 1 although it is less
effective in terms of yield. The direct ring cleavage-
bromination (NBS, MeONa, MeOH) is more efficient, but
the yields are always comparably lower to that obtained
sensitive toward radical processes.11 Tributyltin hydride
is known to produce a radical-induced denitration of
tertiary, secondary, or activated nitro compounds.12 We
found that the chlorine atoms make possible the removal
of the nitro group from methyl ω,ω-dichloro-ω-nitroal-
kanoates 2 using Bu3SnH in benzene at reflux in the
presence of AIBN as initiator. Chlorine atoms are
unaffected by these conditions and hence methyl ω,ω-
dichloroalkanoates are the final products of this proce-
dure.13 A substantial weakening of the carbon-nitrogen
bond is expected in compounds 2, and this effect, coupled
with the low mobility of chlorine atoms in radical
processes, could be responsible for the success of this
selective denitration. Indeed a different behavior is
displayed by compounds 2i,j, obtained by the usual
oxidative ring cleavage from precursors 1i,j. These
chloronitro esters, upon treatment with Bu3SnH, suffer
the removal of the chlorine atom while the nitro group
is retained in the molecule (Scheme 4).
At this point it is clearly evident that gem-dichloro-
carbon radicals are stable enough to possibly undergo
other radical processes. These radicals possess an elec-
trophilic nature, and therefore their reactivity would be
(11) Giese, B. Radicals in Organic Synthesis: Formation of Carbon-
Carbon Bonds; Pergamon Press: Oxford, 1986.
(12) Ono, N. Nitro Compounds: Recent Advances in Synthesis and
Reactivity; Feuer, H., Nielsen, A. T., Eds.; VCH; Weinheim, 1990; p 1.
(13) Dichlorides are usually reduced using the tributyltin hydride-
triethylborane couple: (a) Miura, K.; Ichinose, Y.; Nozaki, K.; Fugami,
K.; Oshima, K.; Utimoto, K. Bull. Chem. Soc. J pn. 1989, 63, 143. (b)
Hamada, T.; Fukuda, T.; Imanishi, H.; Katsuki, T. Tetrahedron 1996,
52, 515.
(14) Curran, D. P. Synthesis 1988, 489.
(15) Curran, D. P.; van Elburg, P. A.; Giese, B.; Gilges, S. Tetrahe-
dron Lett. 1990, 31, 2861.
(16) Ono, N.; Zinsmeister, K.; Kaji, A. Bull. Chem. Soc. J pn. 1985,
58, 1069.

5654 J . Org. Chem., Vol. 61, No. 16, 1996
Notes
(CdO), 1560, 1325 (NO2); 1H NMR (300 MHz, CDCl3) δ ppm
1.53-1.81 (m, 4H), 2.35 (t, 2H, J ) 7.3 Hz), 2.67-2.76 (m, 2H),
3.68 (s, 3H); 13C NMR δ ppm 24.13, 25.12, 33.82, 46.53, 52.15,
111.05, 173.71; MS m/ z 214 (M+ - 31), 197, 165, 101, 85, 74,
59. Anal. Calcd for C7H11Cl2NO4 (244.07) C, 34.45; H, 4.54; N,
5.74. Found C, 34.50; H, 4.52; N, 5.78.
Sch em e 6
Meth od B. 2-Nitrocyclohexanone (1.43 g, 10 mmol) was
dissolved in methanol (60 mL), and then sodium methoxide (1,-
35 g, 25 mmol) and NCS (3.33 g, 25 mmol) were added at 0 °C.
After 10 min the cooling bath was removed, and strirring was
continued for 2 h. Most of the methanol was then removed at
reduced pressure, and the solid residue was dissolved in dichlo-
romethane (50 mL). The organic solution was washed with
water and dried over MgSO4. After evaporation of the solvent
the crude ester was purified as for method A, giving 1.83 g (75%)
of 2b.
Met h yl 5,5-d ich lor o-5-n it r op en t a n oa t e (2a ): yield 75%
(method A); oil; IR (cm-1, neat) 1735 (CdO), 1560, 1325 (NO2);
1H NMR (300 MHz, CDCl3) δ ppm 1.85-2.03 (m, 2H), 2.45 (t,
2H, J ) 7.5 Hz), 2.72-2.83 (m, 2H), 3.81 (s, 3H). Anal. Calcd
for C6H9Cl2NO4 (230.04) C, 31.33; H, 3.94; N, 6.09. Found C,
31.29; H, 3.96; N, 6.04.
Met h yl 8,8-d ich lor o-8-n it r ooct a n oa e (2c): yield 65%
(method A); oil; IR (cm-1, neat) 1735 (CdO), 1555, 1330 (NO2);
1H NMR (300 MHz, CDCl3) δ ppm 1.28-1.44 (m, 4H), 1.46-
1.69 (m, 4H), 2.27 (t, 2H, J ) 7.3 Hz), 2.63-2.75 (m, 2H), 3.66
(s, 3H). Anal. Calcd for C9H15Cl2NO4 (272.13) C, 39.72; H, 5.56;
N, 5.15. Found C, 39.76; H, 5.53; N, 5.19.
with the corresponding chlorination procedure.These ω,ω-
dibromo-ω-nitro esters also behave in a completely dif-
ferent fashion when treated with the above cited tin
reagents. Methyl 6,6-dibromo-6-nitrohexanoate (8) is
reduced by tributyltin hydride and loses two bromine
atoms giving the corresponding nitro ester 9 (Scheme 6).
Further evidence for the enhanced mobility of the bro-
mine atoms is given by the allylation process that
experiences the double substitution of the halogen atoms
with the allyl framework as displayed in Scheme 5. The
latter procedure requires a large excess (6 equiv) of the
allyltin reagent to go to completion. Indeed, upon lower-
ing the amount of the tin reagent, a mixture of mono-
and bisallylated products are obtained.
Meth yl 12,12-d ich lor o-12-n itr od od eca n oa te (2d ): yield
71% (method A); oil; IR (cm-1, neat) 1735 (CdO), 1565, 1330
1
(NO2); H NMR (300 MHz, CDCl3) δ ppm 1.15-1.42 (m, 10H),
1.46-1.70 (m, 6H), 2.29 (t, 2H, J ) 7.3 Hz), 2.66-2.71 (m, 2H),
3.65 (s, 3H). Anal. Calcd for C13H23Cl2NO4 (328.23) C, 47.57;
H, 7.06; N, 4.27. Found C, 47.61; H, 7.02; N, 4.30.
Meth yl 15,15-dich lor o-15-n itr open tadecan oate (2e): yield
70% (method A); oil; IR (cm-1, neat) 1735 (CdO), 1560, 1325
1
(NO2); H NMR (300 MHz, CDCl3) δ ppm 1.20-1.48 (m, 18H),
In conclusion, the oxidative ring cleavage of 2-nitro-
cycloalkanones provides an efficient entry to a new class
of functionalized compounds, namely methyl ω,ω-dichlo-
ronitro-ω-alkanoates. These compounds can be deni-
trated to afford the corresponding methyl ω,ω-dichloro-
alkanoates or allylated, giving a selective substitution of
the nitrogroup by the allyl framework. The correspond-
ing ω,ω-dibromo-ω-nitro esters behave differently with
tin reagents, suffering the removal of the halogen atoms.
It is therefore evident that significant structural changes
can be performed with this class of cleavage products,
and many other changes are to be expected from further
studies.
1.50-1.70 (m, 4H), 2.30 (t, 2H, J ) 7.3 Hz), 2.64-2.72 (m, 2H),
3.67 (s, 3H). Anal. Calcd for C16H29Cl2NO4 (370.31) C, 51.90;
H, 7.89; N, 3.78. Found C, 51.86; H, 7.92; N, 3.75.
Meth yl 3,3,5,5-tetr am eth yl-6,6-dich lor o-6-n itr oh exan oate
(2f): yield 78% (method A); oil; IR (cm-1, neat) 1735 (CdO),
1560, 1325 (NO2); 1H NMR (300 MHz, CDCl3) δ ppm 1.16 (s,
6H) 1.42 (s, 6H), 1.72 (s, 2H), 2.33 (s, 2H), 3.67 (s, 3H). Anal.
Calcd for C11H19Cl2NO4 (300.18) C, 44.01; H, 6.38; N, 4.67.
Found C, 44.06; H, 6.35; N, 4.67.
Meth yl 2-(3,3-dich lor o-3-n itr opr opyl)ben zoate (2g): yield
80% (method B); oil; IR (cm-1, neat) 1735 (CdO), 1560, 1325
(NO2); 1H NMR (300 MHz, CDCl3) δ ppm 2.95-3.10 (m, 2H),
3.18-3.28 (m, 2H), 3.91 (s, 3H), 7.25-7.50 (m, 3H), 7.92 (m, 1H).
Anal. Calcd for C11H11Cl2NO4 (292.12) C, 45.23; H, 3.80; N,
4.79. Found C, 45.19; H, 3.84; N, 4.74.
Met h yl 2-(3,3-d ich lor o-3-n it r op r op yl)-3-m et h oxyb en -
zoa te (2h ): yield 72% (method B); oil; IR (cm-1, neat) 1735
(CdO), 1560, 1325 (NO2); 1H NMR (300 MHz, CDCl3) δ ppm
2.93-3.05 (m, 2H), 3.12-3.26 (m, 2H), 3.88 (s, 3H), 3.91 (s, 3H),
7.01 (dd, 1H, J ) 8.1,1.0 Hz), 7.22-7.31 (m, 1H), 7.46 (dd, 1H,
J ) 7.8, 1.2 Hz). Anal. Calcd for C12H13Cl2NO5 (322.14) C,
44.74; H, 4.07; N, 4.35. Found C, 44.79; H, 4.02; N, 4.4.38.
Dim eth yl 4-ch lor o-4-n itr oocta n d ioa te (2i): yield 70%
(method A); oil; IR (cm-1, neat) 1735 (CdO), 1560, 1335 (NO2);
1H NMR (300 MHz, CDCl3) δ ppm 1.60-1.80 (m, 2H), 2.20-
Exp er im en ta l Section
1H NMR spectra were performed at 300 MHz. Mass spectra
were performed with the EI technique. All chemicals used are
commercially available. 2-Nitrocycloalkanones 1a -h were pre-
pared by nitration of the enol derivatives of the corresponding
cycloalkanones.3 Compounds 1i,j were prepared by conjugate
addition of 1a ,b with methyl acrylate.17
Oxid a tive Rin g Clea va ge of 2-Nitr ocycloa lk a n on es.
Met h yl 6,6-Dich lor o-6-n it r oh exa n oa t e (2b ). Met h od A.
2-Nitrocyclohexanone (1.43 g, 10 mmol) was dissolved in 10%
KOH methanolic solution (30 mL), and then 5% NaClO (25 mL)
was added at 0 °C. After 10 min the cooling bath was removed,
and strirring was continued for 1 h. The mixture was acidified
with 2 N HCl, and then most of the methanol was removed at
reduced pressure. The aqueous solution was exctracted with
dichloromethane and dried over MgSO4. Removal of the solvent
afforded the crude acid that was dissolved in methanol (30 mL)
and stirred 15 h in the presence of Amberlyst 15 ion exchange
resin (0.8 g). The resin was removed by filtration, and after
evaporation of the solvent, the crude ester was purified by flash
chromatography (hexane-ethyl acetate (8:2)), affording 2.07 g
(85%) of chloronitro ester 2b as an oil: IR (cm-1, neat) 1735
2.80 (m, 8H), 3.67 (s, 3H), 3.69 (s, 3H). Anal. Calcd for C10H16
-
ClNO6 (281.69) C, 42.64; H, 5.73; N, 4.97. Found C, 42.68; H,
5.77; N, 4.94.
Dim eth yl 4-ch lor o-4-n itr on on a n ed ioa te (2j): yield 78%
(method A); oil; IR (cm-1, neat) 1735 (CdO), 1560, 1335 (NO2);
1H NMR (300 MHz, CDCl3) δ ppm 1.50-1.85 (m, 4H), 2.15-
2.90 (m, 8H), 3.68 (s, 3H), 3.70 (s, 3H). Anal. Calcd for C11H18
-
ClNO6 (295.72) C, 44.68; H, 6.14; N, 4.74. Found C, 44.73; H,
6.18; N, 4.72.
R a d ica l Den it r a t ion of Met h yl ω,ω-d ich lor on it r oa l-
k a n oa tes. Meth yl 6,6-Dich lor oh exa n oa te (3b). Nitro ester
2b (1.22 g, 5 mmol) was dissolved in dry benzene (20 mL), and
then Bu3SnH (2.91 g, 10 mmol) and AIBN (0.12 g, 0.75 mmol)
were added. The mixture was refluxed for 1 h, and then the
solvent was removed at reduced pressure. The crude product
was purified by flash chromatography [hexane-ethyl acetate (95:
(17) Nakashita, Y.; Hesse, M. Helv. Chim. Acta 1983, 66, 845.

Notes
J . Org. Chem., Vol. 61, No. 16, 1996 5655
5)], affording 0.82 g (82%) of dichloro ester 3b as an oil: IR (cm-1
,
pressure, and the crude product was purified by flash chroma-
tography [hexane-ethyl acetate (95:5)], affording 0.82 g (68%)
of allylchloro ester 7b as an oil: IR (cm-1, neat) 1720 (CdO);
1H NMR (300 MHz, CDCl3) δ ppm 1.60-1.85 (m, 4H), 2.10-
2.21 (m, 2H), 2.32-2.45 (m, 2H), 2.97 (t, 1H, J ) 1.2 Hz), 3.02
(t, 1H, J ) 1.2 Hz), 3.68 (s, 3H), 5.16-5.32 (m, 2H), 5.84-6.06
(m, 1H); MS m/ z 208 (M+ - 31), 171, 135 128, 93, 74, 59. Anal.
Calcd for C10H16Cl2O2 (239.14) C, 50.23; H, 6.74. Found C, 50.29;
H, 7.02.
neat) 1720 (CdO); 1H NMR (300 MHz, CDCl3) δ ppm 1.50-1.80
(m, 4H), 2.15-2.28 (m, 2H), 2.35 (t, 2H, J ) 7.1 Hz), 3.70 (s,
3H), 5.75 (t, 1H, J ) 6.0 Hz); MS m/ z 167 (M+ - 31), 131, 101,
74, 59. Anal. Calcd for C7H12Cl2O2 (199.07) C, 43.23; H, 6.08.
Found C, 43.29; H, 6.02.
Meth yl 5,5-d ich lor op en ta n oa te (3a ): yield 78%; oil; IR
(cm-1, neat) 1735 (CdO), 1H NMR (300 MHz, CDCl3) δ ppm
1.77-1.98 (m, 2H), 2.15-2.26 (m, 2H), 2.48 (t, 2H, J ) 7.3 Hz),
3.78 (s, 3H), 5.76 (t, 1H, J ) 6.0 Hz). Anal. Calcd for C6H10
Cl2O2 (185.05) C, 38.94; H, 5.45. Found C, 39.00; H, 5.41.
-
Meth yl 12,12-dich lor o-14-pen tadecen oate (7d): yield 62%;
1
oil; IR (cm-1, neat) 1720 (CdO); H NMR (300 MHz, CDCl3) δ
Meth yl 8,8-d ich lor oocta n oa te (3c): yield 70%; oil; IR
(cm-1, neat) 1735 (CdO), 1H NMR (300 MHz, CDCl3) δ ppm
1.20-1.75 (m, 8H), 2.12-2.25 (m, 2H), 2.34 (t, 2H, J ) 7.3 Hz),
ppm 1.15-1.80 (m, 16H), 2.10-2.19 (m, 2H), 2.22-2.40 (m, 2H),
2.92 (d, 1H, J ) 1.2 Hz), 2.98 (d, 1H, J ) 1.2 Hz), 3.65 (s, 3H),
5.14-5.30 (m, 2H), 5.80-6.05 (m, 1H). Anal. Calcd for C16H28
Cl2O2 (323.30) C, 59.44; H, 8.73. Found C, 59.39; H, 8.67.
-
3.68 (s, 3H), 5.75 (t, 1H, J ) 6.0 Hz). Anal. Calcd for C9H16
Cl2O2 (227.13) C, 47.59; H, 7.10. Found C, 47.56; H, 7.12.
-
Meth yl 2-(3,3-d ich lor o-5-h exen yl)ben zoa te (7g): yield
70%; oil; IR (cm-1, neat) 1720 (CdO); 1H NMR (300 MHz, CDCl3)
δ ppm 2.40-2.60 (m, 2H), 3.03 (d, 1H, J ) 1.0 Hz), 3.07 (d, 1H,
J ) 1.0 Hz), 3.28-3.40 (m, 2H), 3.91 (s, 3H), 5.15-5.36 (m, 3H),
5.92-6.12 (m, 1H). Anal. Calcd for C14H16Cl2O2 (287.18) C,
58.55; H, 5.62. Found C, 58.60; H, 5.65.
Meth yl 12,12-d ich lor od od eca n oa te (3d ): yield 75%; oil;
IR (cm-1, neat) 1735 (CdO); 1H NMR (300 MHz, CDCl3) δ ppm
1.15-1.70 (m, 16H), 2.12-2.21 (m, 2H), 2.29 (t, 2H, J ) 7.3 Hz),
3.68 (s, 3H), 5.74 (t, 1H, J ) 6.0 Hz). Anal. Calcd for C13H24
Cl2O2 (283.24) C, 55.13; H, 8.54. Found C, 55.15; H, 8.52.
-
Meth yl 15,15-d ich lor op en ta d eca n oa te (3e): yield 77%; oil;
IR (cm-1, neat) 1735 (CdO); 1H NMR (300 MHz, CDCl3) δ ppm
1.15-1.45 (m, 18H), 1.50-1.75 (m, 4H), 2.12-2.21 (m, 2H), 2.31
(t, 2H, J ) 7.3 Hz), , 3.66 (s, 3H), 5.74 (t, 1H, J ) 6.0 Hz). Anal.
Calcd for C16H30Cl2O2 (325.32) C, 59.07; H, 9.29. Found C, 59.11;
H, 9.25.
Meth yl 3,3,5,5-tetr a m eth yl-6,6-d ich lor oh exa n oa te (3f):
yield 70%; oil; IR (cm-1, neat) 1735 (CdO); 1H NMR (300 MHz,
CDCl3) δ ppm 1.14 (s, 6H) 1.21 (s, 6H), 1.72 (s, 2H), 2.30 (s, 2H),
3.64 (s, 3H), 5.63 (s, 1H). Anal. Calcd for C11H20Cl2O2 (255.18)
C, 51.77; H, 7.90. Found C, 51.72; H, 7.94.
Met h yl 2-(3,3-d ich lor o-5-h exen yl)-3-m et h oxyb en zoa t e
(7h ): yield 68%; oil; IR (cm-1, neat) 1720 (CdO); 1H NMR (300
MHz, CDCl3) δ ppm 2.35-2.50 (m, 2H), 3.00 (d, 1H, J ) 1.0
Hz), 3.04 (d, 1H, J ) 1.0 Hz), 3.32-3.48 (m, 2H), 3.85 (s, 3H),
3.92 (s, 3H), 5.15-5.36 (m, 2H), 5.92-6.12 (m, 1H). Anal. Calcd
for C15H18Cl2O3 (317.21) C, 56.80; H, 5.72. Found C, 56.85; H,
5.74.
Meth yl 6,6-d ibr om o-6-n itr oh exa n oa te (8). This product
was prepared with the use of NBS according to method B used
for the synthesis of compounds 2: yield 72%; oil; IR (cm-1, neat)
1735 (CdO), 1560, 1330 (NO2); 1H NMR (300 MHz, CDCl3) δ
ppm 1.53-1.88 (m, 4H), 2.38 (t, 2H, J ) 7.0 Hz), 2.82-2.91 (m,
2H), 3.68 (s, 3H). Anal. Calcd for C7H11Br2NO4 (332.97) C,-
25.25; H, 3.33; N, 4.21. Found C, 25.21; H, 3.35; N, 4.25.
R ea ct ion of Met h yl 6,6-Dib r om o-6-n it r oh exa n oa t e (8)
w ith Tr ibu tyltin Hyd r id e. Meth yl 6-Nitr oh exa n oa te (9).
Product 8 (1.0 g, 3 mmol) was treated as for denitration of
compounds 2 and gave 0.34 (75%) of pure 9 whose spectroscopic
data were in full agreement with those reported.2b
R ea ct ion of Met h yl 6,6-Dib r om o-6-n it r oh exa n oa t e (8)
w ith Allyltr ibu tyltin . Meth yl 6-Nitr o-6-a llyl-8-n on en oa te
(10). Nitro ester 8 (1.30 g, 4 mmol) was dissolved in dry toluene
(30 mL), and then allyltributiltin (7.95 g, 24 mmol) and AIBN
(0.54 g, 3 mmol) were added. The mixture was refluxed for 8h,
and during this time AIBN (0.90 g, 5 mmol) dissolved in toluene
(5 mL) was added in two portions. The solvent was removed at
reduced pressure, and the crude product was purified by flash
chromatography [hexane-ethyl acetate (95:5)], affording 0.71
g (70%) of nitrodiallyl ester 10 as an oil: IR (cm-1, neat) 1720
(CdO) 1545, 1360 (NO2); 1H NMR (300 MHz, CDCl3) δ ppm
1.50-1.75 (m, 4H), 1.85-1.95 (m, 2H), 2.25-2.40 (m, 2H), 2.63
(d, 2H, J ) 0.9 Hz), 2.67 (d, 2H, J ) 0.9 Hz), 3.65 (s, 3H), 5.09-
5.31 (m, 4H), 5.53-5.85 (m, 1H); MS m/ z 224 (M+ - 31), 177,
149 135, 93, 107, 93, 79, 41. Anal. Calcd for C13H21NO4 (255.31)
C, 61.16; H, 8.29; N, 5.49. Found C, 61.21; H, 8.26; N, 5.53.
Meth yl 2-(3,3-d ich lor op r op yl)ben zoa te (3g): yield 85%;
1
oil, IR (cm-1, neat) 1715 (CdO); H NMR (300 MHz, CDCl3) δ
ppm 2.45-2.60 (m, 2H), 3.20 (t, 2H, J ) 7.3 Hz), 3.91 (s, 3H),
5.76 (t, 1H, J ) 6.0 Hz), 7.25-7.50 (m, 3H), 7.92 (m, 1H). Anal.
Calcd for C11H12Cl2O2 (247.12) C, 53.46; H, 4.89. Found C, 53.50;
H,4.95.
Met h yl
2-(3,3-d ich lor op r op yl)-3-m et h oxyb en zoa t e
(3h ): yield 65%; oil; IR (cm-1, neat) 1715 (CdO); 1H NMR (300
MHz, CDCl3) δ ppm 2.40-2.52 (m, 2H), 3.15-3.28 (m, 2H), 3.88
(s, 3H), 3.91 (s, 3H), 7.01 (dd, 1H, J ) 8.0,1.0 Hz), 7.22-7.31
(m, 1H), 7.41 (dd, 1H, J ) 7.6, 1.2 Hz). Anal. Calcd for C12H14
-
Cl2O3 (277.14) C, 52.01; H, 5.09. Found C, 52.06; H, 5.14.
Meth yl 4-n itr oocta n d ioa te (3i): yield 66%; oil; IR (cm-1
,
neat) 1735 (CdO), 1535, 1365 (NO2); 1H NMR (300 MHz, CDCl3)
δ ppm 1.50-1.65 (m, 2H), 1.80-2.37 (m, 8H), 3.67 (s, 3H), 3.69
(s, 3H), 4.45-4.60 (m, 1H). Anal. Calcd for C10H17NO6 (247.25)
C, 48.58; H, 6.93. Found C, 48.54; H, 6.98.
Meth yl 4-n itr on on a n ed ioa te (3j): yield 71%; oil; IR (cm-1
,
neat) 1720 (CdO), 1540, 1365 (NO2); 1H NMR (300 MHz, CDCl3)
δ ppm 1.55-1.70 (m, 4H), 1.90-2.45 (m, 8H), 3.64 (s, 3H), 3.68
(s, 3H), 4.45-4.60 (m, 1H); MS m/ z 215 (M+ - 46), 183, 151,
123, 81, 55, 41. Anal. Calcd for C11H19NO6 (261.27) C, 50.57;
H, 7.33. Found C, 50.63; H, 7.36.
Rea ction of ω,ω-Dich lor o-ω-n itr oester s w ith Allyltr ibu -
tyltin . Meth yl 6,6-Dich lor o-8-n on en oa te (7b). Nitro ester
2b (1.95 g, 8 mmol) was dissolved in dry toluene (25 mL), and
then allyltributiltin (6.62 g, 20 mmol) and AIBN (0.36 g, 2 mmol)
were added. The mixture was refluxed for 8 h, and during this
time AIBN (0.72 g, 4 mmol) dissolved in toluene (5 mL) was
added in two portions. The solvent was removed at reduced
Ack n ow led gm en t. The authors thank University
of Camerino for the financial assistance.
J O960488F