Patent Publication Number: US-4318831-A

Title: Polysubstituted cyclopentene derivatives

Description:
FIELD OF THE INVENTION 
     The present invention concerns new substituted cyclopentene derivatives of the general formula I, ##STR2## wherein R 1  signifies a lower alkyl group with 1 to 3 carbon atoms, R 2  signifies a hydroxymethyl, acetoxymethyl, or formyl group, and the wavy line on carbon atom 1 signifies epimeric forms. 
     The present invention also concerns the use of compounds of the general formula I as perfumes and also as perfume compositions, characterized by a content of a compound of the general formula I, as well as the preparation of such compounds. It has been found that the new polysubstituted cyclopentene derivatives of the general formula I are useful and stable perfumes. In particular, the derivatives with saturated side chains, wherein R 1  =methyl, ethyl, or n-propyl and R 2  =hydroxymethyl, have a pronounced sandalwood scent. 
     BACKGROUND OF THE INVENTION 
     The sandalwood oil from the East Indies used frequently in the perfume industry contains primarily the sesquiterpenes α-and β-santalol (A and B respectively), which also produce the characteristic mild woody odor of the oil. ##STR3## 
     The limited availability and the high price of sandalwood oil motivated the development of chemical syntheses for A and B, which nevertheless could not be utilized industrially. The replacement products used currently are chiefly terpenylcyclohexanols (review article: I. S. Aulchenko and L. A. Kheifits, American Perfumer and Cosmetic, 37 (1970), which are obtained by an acid-catalyzed reaction of camphene with phenol derivatives and subsequent catalytic hydrogenation. Complex mixtures are thereby formed, which consist only to a small extent of active perfumes of the sandalwood type, and are frequently contaminated with terpenylphenols. 
     It would be natural to assume that the production of the most natural sandalwood scent possible would be expected from compounds which are structurally similar to the santalols A and B shown above, and which have a comparable molecular size or number of carbon atoms. However, this implies the synthesis of a comparatively complex ring system which, as shown above, requires complicated procedures and purification steps, or the introduction of comparatively long side chains with appropriate partial structure into a simpler skeletal structure. In the latter process, the results showed little success with respect to the shades of odor (review article: G. Ohloff, Fortschr. Chem. Forsch., Vol. 12/2, page 212, 1969). Thus, in U.S. Pat. No. 4,052,341, besides higher-molecular-weight compounds or those with longer chains, the compound 3-methyl-5-(2,2,3-trimethylcyclopent-3-ene-1-yl)pentane-2-ol, a compound in which a rather long side chain containing a secondary hydroxyl group is bonded to the simple trimethylcyclopentene ring skeleton, is also shown. The process specified for industrial preparation of this substance produces a mixture of isomers which contains a large fraction of 6-(trimethylcyclopent-3-ene-1-yl)hexane-3-ol, so that the odor intensity and quality of the products are somewhat less satisfactory. The patent mentioned states that longer chains with secondary hydroxyl groups must be introduced in order to obtain the desired notes or shades of odor. 
     German Offenlegungsschrift No. 1,922,391 describes campholenylidenealkanols, namely campholenylidenepropanol, 2-campholenylidenebutanol and campholenylideneisopropanol, which have shades of fragrance reminiscent of musk, sandalwood, or of the aroma of figs. The disadvantage of these compounds too is that, because of the unsaturation in their side chains, as is frequently the case with such unsaturated compounds, they are chemically less stable, they have a tendency toward aging reactions, and are therefore less well suited as perfumes. 
     SUMMARY OF THE INVENTION 
     It has now been surprisingly found that the saturated partial structure with a primary hydroxyl group (1-hydroxy-2-methyl-alkanyl) of the santalols also produces excellent fragrances in combination with the trimethylcyclopentene skeleton, when shorter side chains are introduced, and the total number of carbon atoms in the compound is therefore reduced. Thus, the compound 4a FIG. 1) has a pronounced and intense sandalwood odor. This is all the more surprising since according to the general state of knowledge, only compounds which contain 14 or more carbon atoms should have sandalwood aromas (G. Ohloff, Fortschr. Chem. Forsch., Vol. 12/2, p. 213, 1969). 
     Therefore, campholenal (1) can be used as a starting material; it permits the construction of suitable side chains, and it can also be obtained in large amounts according to well-known methods (e.g. L. C. King and H. Farber, J. Org. Chem. 26, 326, 1961) by rearrangement of α-pinene epoxide. Also, the enantiomeric forms of campholenal result from the naturally occurring optical antipodes of α-pinene, which can be used individually or as a mixture. The synthesis of the side chains is carried out by well-known methods (FIGS. 1 and 2), and results in homogeneous products, in contrast to U.S. Pat. No. 4,052,341. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows one reaction scheme for the production of compounds in accordance with the present invention. 
     FIG. 2 shows a second reaction scheme for the production of compounds in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The unsaturated compounds of Formula I can be prepared easily by the Wittig Reaction of 1 with α-bromoalkanoic esters with 3 to 5 carbon atoms in the alkanoic acid portion (including the carboxyl group), preferably the ethyl esters, by well-known procedures (Helv. Chim. Acta 40, 1242, [1957]). 
     The phosphineylides needed for Wittig Reaction can be prepared in a known manner by the action of strong bases on the phosphonium salts obtained by the reaction of α-haloalkanoic esters (halo=chloro, bromo, iodo) with triphenylphosphine (review article: Tripett, Quart. Reviews, Vol. 17, p. 406 [1963]). 
     As usual, aliphatic or aromatic hydrocarbons (e.g. hexane, octane, cyclohexane, benzene, toluene, and xylene), their halogenation products, and alcohols (e.g. methanol, ethanol, isopropanol, butanols, hexanols, cyclohexanol, cyclooctanol), glycols, and ethers (e.g. diisopropyl ether, ethylene glycol dimethyl ether, tetrahydrofuran, dimethyltetrahydrofuran, and dioxane), or their mixtures can be used as solvents for the preparation of the phosphineylides and for carrying out the Wittig Reaction. Polar aprotic solvents such as methanol, ethanol, formamide, dimethylformamide, N-methylpyrrolidone, hexamethyl phosphoramide, acetonitrile, and dimethyl sulfoxide, or their mixtures, are especially suitable. The process can also be carried out in the presence of water. 
     To carry out the Wittig Reaction, esters of α-halo fatty acids (halo=chloro, bromo, iodo) are caused to react with stoichiometric quantities of a strong base, to give the particular phosphoranylidenes. Suitable bases are alkali hydroxides, alkali hydrides, alkali amides, alkali and alkaline earth alkoxides, phenyllithium, or butyllithium. The phosphineylides thus obtained are caused to react with campholenal in the solvents mentioned at temperatures of 10°-40° C. 
     The Witting Reaction can also be carried out in a single step, by dissolving the phosphonium salt and approximately stoichiometric quantities of campholenal in a solvent, treating the approximately stoichiometric amounts of a strong base, and holding the mixture at temperatures of 10°-40° C. for one to two hours. 
     The compounds 2a, b, and c, of FIG. 1 were prepared in this way, and 3a, b, and c, were obtained from these compounds by catalytic hydrogenation. Reduction of the esters, for example with alkali metals or alkaline earth metals in alcohols, or with mixed hydrides of metals of the first and third major groups, provided the carbinols 4a, b, and c, which have an intense sandalwood odor. 
     The hydrogenation was accomplished in a known manner with the use of transition metal catalysts, preferably platinum, (Adams catalyst, Pt or activated charcoal), palladium (on activated charcoal), or Raney nickel in a neutral medium, preferably methanol or ethyl acetate at temperatures of 10°-80° C., and pressures of 1-30 atm, preferably 20°-40° C. and 1-5 atm. 
     The ester reduction is accomplished by Bouveault-Blanc Reduction, using alkali metals or alkaline earth metals in alcohols, preferably sodium in amyl alcohol, or using mixed hydrides of the elements of the first and third major groups in a polar aprotic solvent, preferably with Li[AlH 4  ] in diethyl ether. 
     The methods of reduction mentioned and just discussed, and the catalytic hydrogenation, as already mentioned, are known as such and require no detailed explanation. However, they are mentioned again in the examples of preparation which follow later. 
     Another synthetic route proceeds from the base-catalyzed aldol condensation of 1 with aliphatic C 3  to C 5  aldehydes (FIG. 2). The unsaturated aldehydes 5a-c obtained in this way were converted by catalytic hydrogenation into 6a-c, and, by subsequent reduction, into the saturated carbinols 4a-c. These reactions also are well known as such. 
     Alkali hydroxides or alkali alkoxides, preferably sodium hydroxide or sodium ethoxide, are used as bases for aldol condensations of campholenal with aliphatic aldehydes; boric anhydride is also suitable. Alcohols, preferably methanol or ethanol, serve as the solvent. 
     The aldehydes 6a-c are also accessible by the reaction of 1 with substituted vinyl alkyl ethers with BF 3  catalysis (in analogy with S. Satsumabayshi, K. Nakajo, R. Soneda, and S. Motoki, Bull. Chem. Soc. Japan 43, 1586 [1970]). 
     The alcohols 4a-c were esterified with acetic acid in a known manner to give the acetoxymethyl compounds 7a-c. 
     Suitable IR, NMR, and mass spectra are available for the new compounds (2a-c→7a-c). 
     The compounds of the general formula I excel in their special aromatic properties, in particular with mildly woody (4a-c), green woody (6a-c), and also perhaps somewhat resinous, fruity, ester-like shades of odor (7a-c). Above all, the alcohols 4a-c excel in their sometimes intense sandalwood odors; thus, 4a exceeds the structurally analogous 3-methyl-5-(2,2,3-trimethyl-cyclopent-3-ene-1-yl)pentene-2-ol (U.S. Pat. No. 4,052,341) in the odor intensity and therewith also in their strength in compositions. Compounds of the general formula I can accordingly be used as perfumes and as components of fragrance compositions such as perfumes and perfume bases, or for the perfuming of cosmetic and industrial products of all types. 
     The following examples illustrate the preparation of the compounds pursuant to the invention. 
     PREPARATIVE EXAMPLE 1 
     1-(3-carbethoxybut-2-enyl)-2,2,3-trimethylcyclopent-3-ene (2a) 
     150 g (1 mole) of campholenal (1) and 470 g of (2-carbethoxyethylidene)triphenylphosphorane in 4.5 L of benzene were stirred under N 2  for 6 hours at the boiling point. After cooling, washing with water, and distilling off the benzene, the residue was taken up in petroleum ether and filtered. From the crude product remaining after removal of the solvent by distillation (210 g of yellow oil), 176 g (75%) of 2a, b 0 .8 105°-108° C., was obtained by fractional distillation. 
     PREPARATIVE EXAMPLE 2 
     1-(3-carbethoxybutyl)-2,2,3-trimethylcyclopent-3-ene (3a) 
     A solution of 100 g (0.42 mole) of 2a in 300 mL of methanol was hydrogenated under standard conditions with 5 g of Raney nickel (ca. 10 hours). Filtration, distillation of the solvent, and fractionation yielded 94 g (94%) of 3a, b 0 .7 92°-95° C. 
     PREPARATIVE EXAMPLE 3 
     1-(3-hydroxymethylbutyl)-2,2,3-trimethylcyclopent-3-ene (4a) 
     50 g of 3a in 200 mL of absolute ether was added dropwise at 15° C. to a slurry of 9 g of Li[AlH 4  ] in 250 mL of absolute ether. After four hours of stirring at room temperature, 20 mL of glacial acetic acid was added. The reaction was poured onto ca. 300 g of ice, processed and fractionated. The yield was 32 g (83%) of 4a, b 0 .8 96°-99° C. 
     PREPARATIVE EXAMPLE 4 
     1-(3-formyl-2-alkanyl)-2,2,3-trimethylcyclopent-3-enes (5a-c) 
     At ca. 0° C., 368 g (2.4 moles) of campholenal (1) was added in each case to suspensions of 17 g of sodium ethoxide in 450 mL of methanol. To each mixture was added dropwise over a period of one hour, ca. 5 moles of the aldehyde (propionaldehyde, butyraldehyde, and n-valeraldehyde) (internal temperature, 40° C.). After one hour of stirring at room temperature, acidification with 50 mL of glacial acetic acid in each case, distillation of the methanol, processing, and fractional distillation, there remained 60 to 80% of the corresponding aldehyde (5a-c). 
     PREPARATIVE EXAMPLE 5 
     1-(3-formyl-2-alkyl)-2,2,3-trimethylcyclopentenes (6a-c) 
     In each case, 100 g of the aldehyde 5a-c (from Preparative Example 4) was hydrogenated in 200 mL of methanol with 5 g of Raney nickel for 3 hours under standard conditions. Filtration and distillation of the methanol provided 80 to 90% of the aldehydes 6a-c. On carrying out the hydrogenation at elevated pressure, preferably 20-60 atm, further reduction to 4a-c took place. 
     PREPARATIVE EXAMPLE 6 
     1-(3-hydroxymethyl-2-alkyl)-2,2,3-trimethylcyclopent-3-enes (4a-c) 
     To solutions of 150 g of the aldehydes 6a-c in each case (from Preparative Example 5) in 100 mL of ethanol, solutions of 38 g of sodium borohydride and 0.6 g of NaOH in 75 mL of water were added dropwise at 35°-40° C. over a period of 30 min. After 3 hours of stirring at room temperature and distillation, the alcohols 4a-c were present in yields of 75-85%. 
     The following examples show the use of the compounds pursuant to the invention. 
     EXAMPLE 7 
     
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Perfume oil with sandalwood odor                                          
______________________________________                                    
Linalool                    120 g                                         
Oak moss extract, 50% in diethyl phthalate (DEP)                          
                            100 g                                         
Geranium oil bourbon        100 g                                         
Storax extract              100 g                                         
Coumarin                    70 g                                          
Lavandin oil                65 g                                          
Amyl salicylate             50 g                                          
Benzyl salicylate           50 g                                          
Heliotropin                 50 g                                          
Hydroxycitronellal          50 g                                          
Musk ambrette               50 g                                          
Musk ketone                 50 g                                          
Neryl acetate               35 g                                          
Patchouli oil               30 g                                          
Eugenol                     20 g                                          
                            940 g                                         
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     An addition of 60 g of compounds 4a or 4b to the above mixture endows the resulting perfume oil with a natural persistent sandalwood odor. 
     EXAMPLE 8 
     
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Perfume oil with aldehydic woody note                                     
______________________________________                                    
Bergamot oil               150 g                                          
α-hexylcinnamaldehyde                                               
                           100 g                                          
p-isopropyl-α-methylcinnamaldehyde                                  
                           100 g                                          
Vetiveryl acetate          100 g                                          
Calarene epoxide           70 g                                           
Methylionone               70 g                                           
Musk ketone                50 g                                           
Isobutylquinoline 1%/DEP   45 g                                           
Citronellol                35 g                                           
Undecylenaldehyde 10% in DEP                                              
                           30 g                                           
Styrenyl acetate 10% in DEP                                               
                           30 g                                           
Galbanum oil               20 g                                           
Cyclopentadecanolide       20 g                                           
Oak moss extract           15 g                                           
Elemi oil                  15 g                                           
Iris extract               15 g                                           
Tonka bean extract         15 g                                           
Ylang-Ylang oil            15 g                                           
Decanal 10% in DEP         10 g                                           
Methylnonylacetaldehyde 10% in DEP                                        
                           10 g                                           
Isoeugenol                 10 g                                           
Neryl acetate              10 g                                           
Absolute oil of orange blossom                                            
                           5 g                                            
                           940 g                                          
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     An addition of 60 g of compound 4a brings about a very desirable intensification of the woody background odor and provides a perfume oil with natural emanation. 
     EXAMPLE 9 
     
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Perfume oil with heavy balsam note                                        
______________________________________                                    
Phenylethyl alcohol        180 g                                          
Patchouli oil              129 g                                          
Bergamot oil               90 g                                           
Methylionone               60 g                                           
Musk ketone                60 g                                           
α-hexylcinnamaldehyde                                               
                           50 g                                           
Eugenol                    40 g                                           
Lavender oil               40 g                                           
Benzyl salicylate          30 g                                           
Hydroxyisohexyltetrahydrobenzaldehyde                                     
                           70 g                                           
Ethylvanillin 10% in DEP   30 g                                           
Siam benzoin - resinoid    25 g                                           
Phenylethyl acetate        25 g                                           
Benzyl acetate             25 g                                           
Coumarin                   25 g                                           
Geranium oil bourbon       25 g                                           
Peru balsam oil            20 g                                           
Ethylene brassylate        15 g                                           
Isoeugenol                 10 g                                           
German camomile oil        10 g                                           
                           950 g                                          
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     The addition of 50 g of compound 4b rounds off the perfume oil in a natural manner and imparts to the balsam fragrance components a strong fresh background scent. 
     EXAMPLE 10 
     
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Perfume oil with flowery fragrance                                        
______________________________________                                    
Citronellol                 100 g                                         
Phenylacetaldehyde, 10% in phenylethyl alcohol                            
                            100 g                                         
Ethylene brassylate         85                                            
amylcinnamaldehyde          80 g                                          
Hydroxycitronellal          80 g                                          
α-ionone              80 g                                          
Anise alcohol               60 g                                          
Heliotropin                 50 g                                          
Cinnamyl alcohol            50 g                                          
Methyl octynoate, 10% in DEP                                              
                            50 g                                          
Phenylethyl alcohol         55 g                                          
Phenylethyl acetate         45 g                                          
Nerol                       40 g                                          
Methyl naphthyl ketone      35 g                                          
Monomenthadienyl formate    30 g                                          
Anisyl acetate              20 g                                          
Citronellyl nitrile         15 g                                          
                            975 g                                         
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     In each case, 25 g of the compounds 4a, 4b, 4c, added to this mixture, impart a natural emanation to the flower-like aroma, with simultaneous fixation. 
     EXAMPLE 11 
     
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Perfume oil of the aldehydic cypress type                                 
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Vetiveryl acetate          200 g                                          
Bergamot oil               110 g                                          
Calarene epoxide           110 g                                          
Lemon oil                  60 g                                           
Linaloyl acetate           55 g                                           
α-hexylcinnamaldehyde                                               
                           50 g                                           
Hydroxyisohexyltetrahydrobenzaldehyde                                     
                           50 g                                           
Phenylethyl alcohol        50 g                                           
Oak moss extract           40 g                                           
Musk ambrette              40 g                                           
Benzyl acetate             30 g                                           
Undecylenal, 10% in DEP    25 g                                           
Methylionone               40 g                                           
Neroli oil                 20 g                                           
Lavender oil               20 g                                           
Citronellyl propionate     20 g                                           
Citronellol                20 g                                           
Coumarin                   15 g                                           
Dodecanal 10% in DEP       15 g                                           
                           970 g                                          
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     If 30 g of compound 6a is added to this mixture, an immediate intensification of the aldehydic fresh cypress odor is noted, which also undergoes a substantial fixation from this addition. 
     EXAMPLE 12 
     
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Perfume with lily of the valley odor                                      
______________________________________                                    
Hydroxycitronellal         200 g                                          
Phenylethyl alcohol        200 g                                          
α-hexylcinnamaldehyde                                               
                           200 g                                          
Linalool                   100 g                                          
Rhodinol                   80 g                                           
Rosewood oil               25 g                                           
Geraniol                   20 g                                           
Ylang-ylang oil            15 g                                           
Indole 10% in DEP          10 g                                           
Benzyl acetate             10 g                                           
Phenylacetaldehyde dimethyl acetal                                        
                           10 g                                           
Oil of cinnamon, 10% in DEP                                               
                           10 g                                           
Hydroxyisohexyltetrahydrobenzaldehyde                                     
                           30 g                                           
Linaloyl acetate           25 g                                           
Heptanal, 10% in DEP       5 g                                            
                           940 g                                          
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     An addition of 60 g in each case of compounds 7a-c imparts a fresh fruity blossom character to the perfume oil, with great emanation. 
     It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification.