|United States Patent
April 24, 2001
An efficient direct functionalization of nitrocubanes has been achieved by
irradiation of a solution in an oxalyl halide to yield halogenated and
halocarbonylated derivatives of nitrocubanes.
Bashir-Hashemi; Abdollah (Bridgewater, NJ) |
The United States of America as represented by the Secretary of the Army
April 14, 1994|
Related U.S. Patent Documents
||Application Number||Filing Date||Patent Number||Issue Date|
| ||955386||Oct 1, 1992|
|Current U.S. Class: ||562/498 |
|Current CPC Class:
||C07C 205/10 (20130101); C07C 205/55 (20130101); C07C 2103/90 (20130101)|
|Current International Class:
||C07C 205/10 (20060101); C07C 205/55 (20060101); C07C 205/00 (20060101); C07C 061/12 ()|
|Field of Search:
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Shippen; Michael L.
Attorney, Agent or Firm: Moran; John F.
The Government has rights in this invention pursuant to Contract No.
DAAA21-89-C-0013 awarded by the U.S. Army.
The invention described herein was made under a contract with the
Government and may be used and licensed by or for the Government.
Parent Case Text
This application is a continuation of application Ser. No. 07/955,386,
filed Oct. 1, 1992, now abandoned.
What is claimed is:
FIELD OF USE
This invention describes the direct functionalization of nitrocubanes via irradiation in the presence of an oxalyl halide.
BACKGROUND OF THE INVENTION
Considerable effort in recent years has been directed toward the synthesis of polynitrocubanes because of the potential use of this class of energetic materials as explosives, propellants, fuels and binders (Chemistry of Energetic Materials; Ed.,
G. A. Olah; D. R. Squire; Academic Press, Inc., San Diego, Calif., 1991. Also see Carbocyclic Cage Compounds; Ed., E. J. Osawa; O. Yonemitsu; VCH Publishers, Inc., New York, N.Y., 1992). The compact structures of cage molecules result in high
densities, and the introduction of NO.sub.2 groups further enhances the density. The strain energy present in the cubane skeleton (>166 kcal/mol) is an added bonus to its performance. Furthermore, preliminary results with polynitrocubanes indicate
that such compounds are thermally very stable and are also very insensitive energetic materials. Consequently, it is of interest to introduce functional groups on the cubane skeleton which can be converted to nitro group or other active functionalities.
Direct functionaliztion of nitrocubanes, while an attractive approach, has not heretofore been realized. Cationic or anionic reactions, due to the activity of the nitro groups give either decomposed products or recovered starting materials. We
report here an efficient direct functionalization of a nitrocubane molecule by its irradiation in a solution of oxalyl halide (for a related case see Wiberg, K. B.; 10.sup.th Annual Working Group Meeting, Jun. 3-6, 1992, Kiamesha Lake, N.Y. For much
simpler cases see Wiberg, K. B.; Williams, Jr., V. Z.; J. Org. Chem., 1970, 35, 369; Applequist, D. E.; Saski, T.; J. Org. Chem.; 1978, 43, 2399). This new and potentially powerful synthetic development will greatly shorten the number of steps necessary
to obtain nitrocubane derivatives which are otherwise difficult to synthesize.
SUMMARY OF THE INVENTION
A solution of 1,4-dinitrocubane (Eaton, P. E.; et al; J. Org. Chem.; 1984, 49, 185; Eaton, P. E.; Wicks, G. E.; J. Org. Chem.; 1988, 53, 5353) in oxalyl chloride was irradiated under a sunlamp for 12 h at room temperature. After removing oxalyl
chloride under reduced pressure, the reaction mixture was hydrolyzed and partioned between ethyl acetate and 5% aqueous NaOH. From the organic phase was isolated 2-chloro-1,4-dinitrocubane, 3, and 2,5-dichloro-1,4-dinitrocubane, 4. After acidification
of the alkaline layer with HCl and extraction with ethyl acetate, 2-carboxy-1,4-dinitrocubane, 5, was obtained in 68% yield. ##STR1##
The structures of 3, 4, and 5 were confirmed by NMR spectrometry. Furthermore, Compound 5 was converted to the corresponding 2-carbomethoxy-1,4-dinitrocubane 6 by esterification using MeOH, and the molecular structure of 6 was confirmed by X-ray
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following section describes specific experimental procedures used for the synthesis:
A mixture of 1,4-dinitrocubane, 1, (388 mg, 2.0 mmol) in oxalyl chloride (50 mL) was photolyzed under a sunlamp for 18 h at room temperature. Oxalyl chloride was removed on a rotary evaporator and the solid residue was partioned between EtOAc
(40 mL) and NaOH solution (5%, 30 mL). After stirring for 3 h, the organic phase was separated, washed with brine, dried over anhydrous Na.sub.2 SO.sub.4 and concentrated under reduced pressure. The residue was chromatogrphed on silica gel using
hexane/CH.sub.2 Cl.sub.2 (1:1) to give 2-chloro-1,4-dinitrocubane 3, m.p. 145-147.degree. C.; .sup.1 H NMR (CDCl.sub.3); .delta. 4.84 (m, 2H); 4.71 (m, 3H); and 2,5-dichloro-1,4-dinitrocubane, 4, m.p. 188-190.degree. C.; .sup.1 H NMR (CDCl.sub.3);
.delta. 4.90 (dd, 2H); 4.78 (dd, 2H).
The alkaline layer was acidified with HCl (10%) and organic materials were extracted with EtOAc (2.times.30 mL). The organic phase was washed with bring, dried over Na.sub.2 SO.sub.4, and concentrated via rotary evaporator to give 400 mg or a
crude product which was triturated with hexane/acetone 10:1, (5.0 mL) to give 2-carboxy-1,4-dinitrocubane, 5, m.p. 187-189 (Dec) .degree. C.; .sup.1 H NMR (acetone-d.sub.6); .delta. 4.96 (m, 2H); 4.74 (m, 3H).
Compound 5 (100 mg, 0.4 mmol) was stirred with MeOH (20 mL) and MeSO.sub.3 H (4 drops) at reflux overnight. The reaction mixture was concentrated and then dissolved in ethyl acetate (20 mL). The solution was washed with aqueous Na.sub.2
CO.sub.3 (5%), then brine, dried over anhydrous Na.sub.2 SO.sub.4 and concentrated. The residue was triturated with ether hexane (1:1) to give 2-carbomethoxy-1,4-dinitrocubane 6 m.p.=165.degree. C.; .sup.1 H NMR (CDCl.sub.3), .delta. 4.92 (M, 2H);
4.62 (m, 3H), 3.80 (s, 3H).
In another expremint, the solid residue from the reaction of 1,4-dinitrocubane (100 mg) and oxalyl chloride (20 mL) under a sunlamp (vide supra) was treated with methanol (20 mL) for 4 h at room temperature. The excess methanol was evaporated
and the residue was dissolved in ethyl acetate (20 mL). The organic layer was washed with 5% aqueous Na.sub.2 CO.sub.3 and then brine. After drying over Na.sub.2 SO.sub.4 and then concentration, the crude product was chromatographed on silica gel using
hexane/CH.sub.2 Cl.sub.2 (1:1) to give compounds 3, 4, and 6.
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