Substituted delta-lactones in perfume compositions
SUMMARY OF THE INVENTION 
     The present invention relates to a method for enhancing, improving or modifying the odorous properties of perfumes and perfumed products which comprises adding thereto a perfuming effective amount of 6-ethyl-5,6-dihydro-2H-pyran-2-one or 6-n-butyl-5,6-dihydro-2H-pyran-2-one. 
     This invention provides further a perfume, perfume base or perfumed article which comprises having added thereto an effective amount of 6-ethyl-5,6-dihydro-2H-pyran-2-one or 6-n-butyl-5,6-dihydro-2H-pyran-2-one. 
     BACKGROUND OF THE INVENTION 
     Among the great variety of lactone derivatives which have found sofar an industrial application in the field of perfumery, there appear to be numerous γ- and δ-lactones whose odorous properties could be defined as being of fatty, coco-nut, flowery and fruity type. Some lactones are further characterized by an odour reminiscent of vegetable, celery in particular, or lovage [see: S. Arctander, Perfume and Flavor Chemicals, Montclair U.S.A. (1969), Secs. 416, 828, 829, 1102, 1103, 1504, 1590, 1648 etc.]. Specific examples of such derivatives are indicated for instance in U.S. Pat. No. 3,380,457 which document describes the use of lactones having generic formula ##STR1## comprising a single or a double bond in the position indicated by the dotted lines, and wherein each of substituents R 1 , R 2  and R 3  represents a hydrogen atom or an alkyl radical, as flavouring agents for tobacco products. The following compounds have been disclosed in the cited U.S. patent as being derivatives of special interest: ##STR2## 3-isopropyl-δ-valerolactone; ##STR3## δ-lactone of 5-hydroxy-3-isopropyl-pent-2-enoic acid; ##STR4## p-methyl-δ-valerolactone. 
     U.S. Pat. No. 3,996,170 describes the use as perfuming agents of lactones of formula ##STR5## wherein R 1  represents a methyl radical or a hydrogen atom, and R 2  represents an alkyl group containing 3 to 5 carbon atoms. Said lactones of formula (II) possess notes as varied as sweet, floral, herbal, green, celery-like, coconut, coumarin, lovage-like, foenugreek, tagette. 
     When we have tried to repeat the process for the preparation of 6-n-butyl-alpha-pyrone--the compound of formula (II) wherein R 1  ═H and R 2  ═n-butyl--in accordance with the disclosure of cited U.S. Pat. No. 3,996,170, we have noticed that the obtained substance polymerized rapidly at room temperature, it became yellow and its smell gradually changed and denaturated. 
     We have now discovered that two compounds of analogous structure viz. 6-ethyl- and 6-n-butyl-5,6-dihydro-2H-pyran-2-one, possessed very useful odorous properties and consequently could be advantageously used in the perfume industry. The two compounds cited above presented, in contradistinction to the mentioned 6-n-butyl-alpha-pyrone, a constant and homogeneous odorous note; moreover, the lactonic-celery character of 6-n-butyl-alpha-pyrone is practically absent in the two compounds of the invention, whose character is more spicy and fruity. Owing to their properties, 6-ethyl- and 6-n-butyl-5,6-dihydro-2H-pyran-2-one find a particular application in the compounding of composition of fougere, chypre, lavender or even fruity type. 
     PREFERRED EMBODIMENTS OF THE INVENTION 
     Depending on the nature of the perfumed materials or on the effect desired, the proportions used may vary within a wide range and may be, for example, of the order of about 1 or 2% by weight, based on the total weight of said perfumed materials or composition into which they are incorporated. These values of concentrations can however be increased up to 15 or 20% according to the particular application under consideration. 
     6-Ethyl- and 6-n-butyl-5,6-dihydro-2H-pyran-2-one are known compounds; however, the prior art does not disclose nor suggest their utility as perfumants [see e.g. Chim. Ind. (Milan), 50, 194-6(1968) as reported in Chem. Abstrs. 69, 35352 t (1968); Rec. Trav. Chim. Pays-Bas 86, 504 (1967)]. 
     The invention is better illustrated by the following examples. 
    
    
     EXAMPLE 1 
     A base perfume composition of fruity type was prepared by mixing together the following ingredients (parts by weight): 
     
         ______________________________________                                    
Cinnamyl isobutyrate     500                                              
HEDIONE® *           100                                              
Phenoxyethyl isobutyrate 100                                              
Dimethyl-benzyl carbinol 50                                               
α-Isomethylionone  50                                               
Allylionone              50                                               
                         850                                              
______________________________________                                    
 *HEDIONE: origin Firmenich SA, Geneva                                    
 
    
     By adding to the above base composition, 150 g of 6- n-butyl-5,6-dihydro-2H-pyran-2-one there was obtained a novel composition whose fruity character was reminiscent of the odour of plums or apricots. 
     EXAMPLE 2 
     A base perfume composition of &#34;fougere&#34; type destined to the perfuming of toilet soaps was prepared by admixing the following ingredients (parts by weight): 
     
         ______________________________________                                    
Lavandin oil               200                                            
Geranium oil               100                                            
Cedryl acetate             100                                            
Absolute tree moss 50%*    100                                            
Hexyl salicylate           60                                             
Linalyl acetate            50                                             
Linalol                    50                                             
Aspic oil                  40                                             
Hex-3-en-1-yl formate 1%*  30                                             
Galbanum oil 10%*          30                                             
Terpineol                  30                                             
Clove oil of Madagascar    20                                             
Patchouli oil              20                                             
1,1-Dimethyl-4-acetyl-6-ter-butylindane                                   
                           20                                             
Coumarin                   20                                             
Isopropylcyclohexyl methanol                                              
                           10                                             
Cinnamic alcohol           10                                             
Couminic aldehyde 10%      10                                             
                           900                                            
______________________________________                                    
 *in diethyl phthalate                                                    
 
    
     By adding to the above base 100 g of 6-n-butyl-5,6-dihydro-2H-pyran-2-one, there was obtained a novel composition whose spicy coumarinic character was more pronounced. 
     By replacing in the above examples, 6-n-butyl-5,6-dihydro-2H-pyran-2-one with 6-ethyl-5,6-dihydro-2H-pyran-2-one, analogous effects were observed.