it is known to those with the skill in the art that formula i as defined above provides the following novel compounds : the compounds of the present invention were prepared with cyclohexanones according to the following reaction scheme , the details of which are specified in the examples . materials and catalysts were purchased from sigma - aldrich chemical company unless noted otherwise . wherein r 1 , r 2 , r 3 and r 4 are defined as above ; those with skill in the art will recognize that the compounds of the present invention may have a number of chiral centers , thereby providing numerous isomers of the claimed compounds . it is intended herein that the compounds described herein include isomeric mixtures of such compounds , as well as those isomers that may be separated using techniques known to those having skill in the art . suitable techniques include chromatography such as high performance liquid chromatography , referred to as hplc , and particularly silica gel chromatography and solid phase microextraction , referred to as spme . 2 , 2 , 3a , 7 - tetramethyl - octahydro - benzofuran has been surprisingly found to possess unexpected fragrance effect such as , for example , herbal , sweet , camphor , woody , fresh , and green notes . 3a - isopropyl - 2 , 6 - dimethyl - octahydro - benzofuran has been surprisingly found to possess strong and unexpected fragrance effect such as , for example , cedar wood , green , spice , flora , eucalyptus , and slight piney notes . the use of the compounds of the present invention is widely applicable in current perfumery products , including the preparation of perfumes and colognes , the perfuming of personal care products such as soaps , shower gels , and hair care products , fabric care products as well as air fresheners and cosmetic preparations . these compounds can also be used to perfume cleaning agents , such as , but not limited to detergents , dishwashing materials , scrubbing compositions , window cleaners and the like . in these preparations , the compounds of the present invention can be used alone or in combination with other perfuming compositions , solvents , adjuvants and the like . the nature and variety of the other ingredients that can also be employed are known to those with skill in the art . many types of fragrances can be employed in the present invention , the only limitation being the compatibility with the other components being employed . suitable fragrances include but are not limited to fruits such as almond , apple , cherry , grape , pear , pineapple , orange , strawberry , raspberry ; musk , flower scents such as lavender - like , rose - like , iris - like , carnation - like . other pleasant scents include herbal and woodland scents derived from pine , spruce and other forest smells . fragrances may also be derived from various oils , such as essential oils , or from plant materials such as peppermint , spearmint and the like . a list of suitable fragrances is provided in u . s . pat . no . 4 , 534 , 891 , the contents of which are incorporated by reference as if set forth in its entirety . another source of suitable fragrances is found in perfumes , cosmetics and soaps , second edition , edited by w . a . poucher , 1959 . among the fragrances provided in this treatise are acacia , cassie , chypre , cyclamen , fern , gardenia , hawthorn , heliotrope , honeysuckle , hyacinth , jasmine , lilac , lily , magnolia , mimosa , narcissus , freshly - cut hay , orange blossom , orchid , reseda , sweet pea , trefle , tuberose , vanilla , violet , wallflower , and the like . the term “ improving ” in the phrase “ improving , enhancing or modifying a fragrance formulation ” means raising the fragrance formulation to a more desirable character . the term “ enhancing ” means making the fragrance formulation greater in effectiveness or providing the fragrance formulation with an improved character . the term “ modifying ” means providing the fragrance formulation with a change in character . the terms “ fragrance formulation ”, “ fragrance composition ”, and “ perfume composition ” mean the same and refer to a mixture of compounds including , for example , alcohols , aldehydes , ketones , esters , ethers , lactones , nitriles , natural oils , synthetic oils , and mercaptans , which are admixed so that the combined odors of the individual components produce a pleasant or desired fragrance . the fragrance formulation of the present invention is a fragrance formulation comprising a compound of the present invention . the term “ fragrance product ” means a consumer product that adds a fragrance or masks a malodor . fragrance products may include , for example , perfumes , colognes , personal care products such as soaps , shower gels , and hair care products , fabric products , air fresheners , cosmetic preparations , and perfume cleaning agents such as detergents , dishwashing materials , scrubbing compositions , and window cleaners . the fragrance product of the present invention is a consumer product that contains a compound of the present invention . olfactory acceptable amount is understood to mean the amount of a compound in a fragrance formulation , wherein the compound will contribute its individual olfactory characteristics . however , the olfactory effect of the fragrance formulation will be the sum of effect of each of the fragrance ingredients . thus , the compounds of the present invention can be used to improve or enhance the aroma characteristics of the fragrance formulation , or by modifying the olfactory reaction contributed by other ingredients in the formulation . the olfactory acceptable amount may vary depending on many factors including other ingredients , their relative amounts and the olfactory effect that is desired . the amount of the compounds of the present invention employed in a fragrance formulation varies from about 0 . 005 to about 50 weight percent , preferably from 0 . 5 to about 25 weight percent , and more preferably from about 1 to about 10 weight percent . those with skill in the art will be able to employ the desired amount to provide desired fragrance effect and intensity . in addition to the compounds of the present invention , other materials can also be used in conjunction with the fragrance formulation . well known materials such as surfactants , emulsifiers , polymers to encapsulate the fragrance can also be employed without departing from the scope of the present invention . when used in a fragrance formulation , the compounds of the present invention provide unexpected strong herbal , sweet , camphor , woody , fresh , green , spice , flora , eucalyptus , and slight piney characteristics and make the fragrance formulation more desirable and noticeable . the odor qualities found in the compounds of the present invention assist in beautifying and enhancing the finished accord and improve the performance of other materials in the fragrance formulation . the following are provided as specific embodiments of the present invention . other modifications of this invention will be readily apparent to those skilled in the art . such modifications are understood to be within the scope of this invention . as used herein all percentages are weight percent unless otherwise noted , ppm is understood to stand for parts per million , l is understood to be liter , ml is understood to be milliliter , mol is understood to be mole , kg is understood to be kilogram , g is understood to be gram and mol is understood to be mole . iff as used in the examples is understood to mean international flavors & amp ; fragrances inc ., new york , n . y ., usa . preparation of 2 , 6 - dimethyl - 2 -( 2 - methyl - allyl )- cyclohexanone : 2 , 6 - dimethyl - cyclohexanone ( 1 kg , 4 mol ), trimethyl orthoformate ( tmof , 880 g ), and methanol ( 800 ml ) were charged to a 5 l reaction flask . hcl was added quickly . reaction exothermed and the temperature increased from 14 ° c . to 20 ° c . the reaction mixture was heated to 60 ° c . and aged for 7 hours . when the reaction was about 75 % complete , the reaction mixture was quenched with naoch 3 ( 25 %, 25 g ), heated to 90 ° c ., and applied to a dean - stark trap . the reaction mixture was then cooled to room temperature followed by sequential addition of methallyl alcohol ( 1 . 25 kg , 8 . 5 moles ), hoac ( 50 g ), and methane sulfonic acid ( msa , 10 g ). the resulting mixture was heated to 110 ° c ., applied to a bidwell - sterling trap , and aged for 4 hours until gas chromatograph analysis indicated that the reaction was 95 % completed . the reaction mixture was then cooled and washed with saturated sodium carbonate solution ( 3 l ) to provide the crude product 2 , 6 - dimethyl - 2 -( 2 - methyl - allyl )- cyclohexanone . preparation of 2 , 2 , 3a , 7 - tetramethyl - octahydro - benzofuran ( formula ii ): a 3 l reaction flask was charged with vitride ® ( 325 g , 0 . 9 mol ) and toluene ( 500 ml ), heated to 100 ° c ., fed with 2 , 6 - dimethyl - 2 -( 2 - methyl - allyl )- cyclohexanone ( 200 g , 1 . 1 mol , obtained in example i ) for over 2 hours , and aged for another 2 hours . after the reaction completed , the reaction mixture was cooled to room temperature , quenched with ipa ( 100 ml ). naoh ( 50 %, 300 g ) and water ( 200 ml ) were then added , heated to 80 ° c ., and aged for another hour . the reaction mixture was cooled to room temperature and more water ( 200 ml ) was added . layers were split to dispose the aqueous waste . the organic layer was charged back to the flask . toluene ( 300 ml ) was added and water was removed with a dean - stark trap through azeotrope . the resuling mixture was cooled to 50 ° c . msa ( 28 g , 0 . 3 mol ) was added and the reaction mixture was heated to reflux . the consumption of the starting material was indicated after 3 hours . the resulting mixture was then cooled to room temperature and washed with saturated sodium carbonate solution ( 1 l ) followed by brine ( 1 l ). distillation and fractionation provided the product 2 , 2 , 3a , 7 - tetramethyl - octahydro - benzofuran ( 125 g ) in 63 % yield . 1 h nmr ( cdcl 3 , 500 mhz ): 3 . 17 ( d , j = 5 . 7 hz , 1h ), 1 . 26 ( s , 3h ), 1 . 20 ( s , 3h ), 1 . 05 ( s , 3h ), 0 . 93 ( d , j = 7 . 2 hz , 3h ), 0 . 80 - 1 . 78 ( m , 9h ) 2 , 2 , 3a , 7 - tetramethyl - octahydro - benzofuran was described as having herbal , sweet , camphor , woody , fresh and green notes with low strength . preparation of 3a - isopropyl - 2 , 6 - dimethyl - octahydro - benzofuran ( formula iii ): menthone ( 500 g ), trimethylorthoformate ( 377 g ) and methanol ( 400 ml ) were charged to a 3 l reaction flask . in one portion , hydrochlorioc acid ( 3 g ) was added and the mixture exothermed from 22 ° c . to 40 ° c . the reaction mixture was aged 6 hours and quenched with sodium methoxide solution ( 35 g ). low boiling materials were removed while the reaction mixture was heated to 90 ° c . allyl alcohol ( 404 g ) and acetic acid ( 195 g ) were added and the reaction mixture was heated to 160 ° c . the reaction mixture was held at 160 ° c . for 3 hours , cooled to 25 ° c ., and washed with brine ( 500 ml ). the crude product was distilled to provide a mixture of allyl menthone isomers . red - al ® ( 397 g ) was charged to a 2 l reaction flask and heated to 55 ° c . allyl menthone isomers ( 248 g , obtained in above ) were fed into the flask and the reaction was allowed to exotherm to 70 ° c . the reaction mixture was aged for 8 hours and quenched with isopropanol ( 100 ml ) followed by aqueous sodium hydroxide solution ( 50 %, 307 g ). the resulting organic layer was washed with brine ( 500 ml ). the crude alcohol was distilled to provide a mixture of allyl menthol isomers . allyl menthol isomers ( 200 g , obtained in above ), toluene ( 500 ml ), and methanesulfonic acid ( msa , 5 g ) were charged to 1 l reaction flask . the reaction mixture was heated to 80 ° c ., aged for 8 hours , then cooled to 22 ° c ., and washed with aqueous sodium carbonate solution ( 10 %, 300 ml ). the resulting crude mixture was purified by distillation to afford 3a - isopropyl - 2 , 6 - dimethyl - octahydro - benzofuran in ( 130g ) 65 % yield . 1 h nmr ( cdcl 3 , 500 mhz ): 3 . 40 - 4 . 25 ( m , 2h ), 0 . 75 - 2 . 17 ( m , 10h ), 1 . 28 ( d , j = 6 . 3 hz , 3h ), 0 . 96 ( d , j = 6 . 6 hz , 3h ), 0 . 89 ( d , j = 6 . 9 hz , 6h ) 3a - isopropyl - 2 , 6 - dimethyl - octahydro - benzofuran was described as having cedar wood , green , spice , flora , eucalyptus , and slight piney notes .
the present invention is directed to novel fragrance compounds and their unexpected advantageous use in improving , enhancing or modifying a fragrance formulation through the addition of an olfactory acceptable amount of the compounds , wherein the compounds are represented by the following formula : wherein r 1 , r 2 and r 3 are independently selected from the group consisting of hydrogen and methyl ; and r 4 is a c 1 - c 3 alkyl group .