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United States Patent Office Patented June 17, 1969

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United States Patent Office Patented June 17, 1969 3,450,782 United States Patent Office Patented June 17, 1969 2 1,3-dibromocyclobutane with sodium in refluxing dioxane, 3,450,782 PROCESS FOR THE PREPARATION OF K. B. Wiberg, G. M. Lampman, R. P. Ciula, D. S. Con CYCLICALKANES nor, P. Scherter, and J. Lavanesh, Tetrahedron, 21, 2749 Daniel S. Connor, Cincinnati, Ohio, assignor to The (1695), bicyclo[1.1.1 pentane by treatment of 3-(bromo Procter & Gamble Company, Cincinnati, Ohio, a cor methyl)-cyclobutyl bromide with sodium metal at a 0.5% poration of Ohio yield, with lithium amalgam in refluxing dioxane at a No Drawing. Filed Nov. 29, 1967, Ser. No. 686,738 4.2% yield and with sodium/naphtahalene at a 8% yield, Int, C. C07c I/28 K. B. Wiberg, D. S. Connor, and G. M. Lampman, Tetra U.S. C. 260-666 8 Claims hedron Letters, 531 (1964); K. B. Wiberg and D. S. Con 0 nor, J. Am. Chem. Soc., 88, 4437 (1966). On examination of the literature hereinbefore cited ABSTRACT OF THE DISCLOSURE on cyclization, it is apparent that the yields obtained were This invention concerns the preparation of cyclic al extremely low, that the conditions for reaction when it kanes from dihalogenated alkanes using lithium amalgam. did occur were quite severe, and that the starting materials 5 used were less than common. OBJECTS OF THE INVENTION SUMMARY OF THE INVENTION The use of the method of this invention to obtain cyclic The object of this invention is to prepare cyclic al compounds provides a valuable synthetic tool heretofore kanes from the halogenated straight chain starting ma 20 unknown to chemists, thus enabling the production of terials using lithium amalgam to remove the halogens valuable end products. For example, the cyclization of and form a cyclic compound. butane to cyclobutane provides a compound with an in A further object of this invention is to prepare known creased energy source over that available with the straight cyclic compounds useful as anesthetics. chain entity. Butane is well known as a fuel source, e.g., Another object of this invention is to prepare known 25 as a lighter fuel or in any application requiring a com cyclic compounds having a greater energy level than their bustible material that is readily volatile and has a low analogous straight chain compounds. flash point for combustion. Cyclobutane can be advanta A further object of this invention is the preparation of geous Substituted for butane in numerous applications. known cyclic compounds in yields which are not avail The cyclization of pentane to cyclopentane yields, as is able with methods heretofore known. 30 Well known, a solvent useful in many different applica An additional object of this invention is to prepare tions. The cyclization of propane to cyclopropane results known cyclic compounds heretofore difficult to synthesize. in a product that is well known as an anaesthetic. BACKGROUND OF THE INVENTION This invention involves the intramolecular reaction of The Wurtz reaction using sodium in toluene to couple a dihaloalkane in the presence of lithium amalgam to hydrocarbon groups by removal of halogens is known 35 form the cyclic compound and the production of lithium as a synthesis method for some cyclic compounds. How halide according to the following schematic: ever, because of the poor yields and the availability of Li(Hg). alternate routes, the use of the Wurtz reaction in cycli X-(CR2)X --> (CR2) zation has been severely limited. In fact, it has been 40 limited almost exclusively to the closures of three-mem where X is a halogen, R is a hydrogen or a hydrocarbon bered rings-for example, the preparation of cyclopro group and n is an integer. Cyclization using lithium amal pane in an 80% yield. H. B. Hass, E. I. McBee, G. E. gam has been used in the prior art to form bicyclo[1.1.1 - Hinds, and E. S. Gluesenkamp, Ind. Eng. Chem., 28, pentane from 3-(bromomethyl)cyclobutylbromide. This 1178 (1936). Other examples of ring closure include the 45 reaction yielded primarily 1,4-pentadiene and production synthesis of spiro 2.5]-octane, R. W. Shortridge, R. A. of bicyclo[1.1.1 pentane occurred only in a 4.2% yield. Craig, K. W. Greenlee, J. M. Derfee, and C. E. Boord., The cyclization of straight chain dihaloalkanes in good J. Am. Chem. Soc. 70, 946 (1948) and spiropentane, yields with the present invention was unexpected because D. E. Appleduist, G. F. Fanta, and B. W. Henrikson, of the smaller probability that the halogens would be J. Org. Chem., 23 1715 (1958) using pentaerythrity tet 50 spatially arranged such that cyclization would occur. This romide and zinc metal with a simultaneous removal of is in contrast to the situation involved in the formation zinc ions as they form using tetrasodium ethylenediamine of a bicyclic since the possible spatial configurations are tetraacetate. No successful synthesis of a four membered well defined due to the cyclic nature of the starting ma ring system, e.g., cyclobutane, using the Wurtz synthesis terial. Again, it was unexpected that cyclization in good was reported for over 50 years. Unsuccessful attempts 55 yields would occur with straight chain dihaloalkanes and were reported by the following: H. G. Colman and W. lithium amalgam. Rather telomerization would be ex H. Parkin, Jr., J. Chem. Soc., 53, 201 (1888); D. Phili pected to occur based on the known difficulty, as demon poff, J. prakt. chem., 93, 177 (1916); J. P. Wilrant, Rec. strated by the prior art hereinbefore described, in forming Trav. Chem, 58, 329 (1939); and R. C. Krug, Ph.D. cyclic structures from straight chain starting materials. Dissertation, Ohio State University (1944). 60 Dihaloalkanes Cyclobutane was finally prepared using 1,4-dibromo The dihaloalkanes of this invention are of the following butane and sodium in refluxing toluene at a 7% yield, general formula J. Cason and R. L. Way, J. Org. Chem., 14, 31 (1949) and using lithium in reflexing ether at a 20% yield, R1 Burger, German Patent 832,750. Ring closure to form 65 x -i-x bicyclic compounds, similar to the straight chain ring closure situation, has had only limited success. Bicyclo R. 1.1.0 butane has been synthesized by the treatment of where each R and R is selected from the group consist 3,450,782 3. 4 ing of hydrogen, alkyl, aryl, alkaryl, aralkyl, cyclic, heters are also suitable, and in a solvent medium. The lithium ocyclic groups, and, when taken together in pairs, bi amalgam is placed in the solvent and the dihaloalkane valent alkylene groups, having from 1 to about 20 car added over a period of time. Suitable solvents are those bon atoms, which heteroatoms in the heterocyclic groups that are stable to lithium amalgam, e.g., saturated hydro can be sulfur and oxygen, and mixtures of the entities carbons, such as pentane, hexane, octane, cyclopentane, hereinbefore described, wherein n is an integrer from 3 to and cyclohexane; aromatic hydrocarbons such as benzene, about 20 and is determined prior to the selection of said Xylene, and toluene; or ether solvents such as dioxane, tet R1 and R2 groups, wherein each X is selected from the rahydrofuran, 1,2-dimethoxyethane, and diethyl ether. group consisting of bromine, chlorine, and iodine, and The dihaloalkane can be added as a pure material or dis wherein the total number of carbon atoms in the dihalo 10 solved in any of the aforementioned solvents. The con alkane is less than 30. centration of the dihaloalkane in the solvent can range Where R1 and R2 are alkyl or aralkyl, examples of suit from 0.0001% to the actual addition of the pure dihalo able groups are as follows: methyl, ethyl, propyl, n-butyl, alkane. The use of a solvent in the addition step at a di isobutyl, n-pentyl, 2,3-dimethylpentyl, n-hexyl, 3-ethyl haloalkane concentration of 25% is preferred. The reac hexyl, n-octyl, isooctyl, n-nonyl, n-decyl, n-undecyl, tri tion is normally run at the reflux temperature of the propylene, n-dodecyl, tetrapropylene, n-tridecyl, n-tetra Solvent and with the proper choice of solvents, the best decyl, 6-hexyltetradecyl, 5-ethyl-2,2-dimethyltridecyl, n conditions for maximum yields can be readily obtained. pentadecyl, 2,5,8,11-tetraethylpentadecyl, n-hexadecyl, n The temperature of the reaction can range from about 20 octadecyl, eicosyl, 4-phenylbutyl, 6-naphthylhexyl, and C. to about 150° C. The preferred temperature is about 12-phenyldodecyl; where R and R2 are aryl or alkaryl, 20 100° C. The preferred solvent is dioxane. Tetrahydro suitable groups are as follows: phenyl, biphenyl, triphenyl, furan is also preferred as a solvent. The reaction is naphthyl, anthracyl, anthranthryl, phenanthryl, 3-butyl normally run for about 3 to 6 hours but it may be neces pheny, 3-dodecylphenyl, tetrapropylenephenyl, 8-hexyl sary to allow a longer reaction time depending on the naphthyl, 8-benzylnaphthyl, and 4-dodecylnaphthyl; conditions, reactants, solvents, and temperatures used. where R1 and R are cyclic or heterocyclic, suitable 25 Usual gas chromatographic techniques can be used to fol groups are as follows. cyclopropyl, cyclobutyl, cyclo low the course of the reaction and the determination of pentyl, cyclohexyl, cycloheptyl, methylcyclohexyl, dode the starting materials remaining. cyclohexyl, cyclopentyltetradecyl, cyclooctyl, furanyl, The following examples are intended to be illustrative thiophenyl, pyranyl, and thiopyranyl: where R and Rare of the invention and are not intended to limit the scope taken together to be a bivalent alkylene group, suitable 30 of the invention nor the claims of the invention. groups are methylene, ethylene, propylene, butylene, All percentages given herein are weight percent unless pentylene, hexylene, dodecalene, and eicosylene.
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