5- Methyl-3-heptanone oxime

C8H17NO, Mr 143.23, bpo.i i-pa 70 °C, wf 1.4519, is not reported as being found in nature. It is a colorless to pale yellow liquid with a powerful, green, leafy odor. 5-Methyl-3-heptanone oxime is prepared by oximation of the corresponding ketone. It imparts natural and fresh nuances to fragrance notes and is used in fine perfumery as well as in cosmetics, soaps, and detergents. 

Unlike the reaction of alkyl aryl ketoximes with tetrasulfur tetranitride <1996CHEC-II(4)355>, the treatment of alkyl methyl ketoximes 189 with tetrasulfur tetranitride antimony pentachloride complex in either benzene or toluene at 50-80°C gave low yields (3-37%) of 3-alkyl-4-methyl-l,2,5-thiadiazoles 190 (Equation 39) <1999H(50)147>. Compounds 190 were volatile and the low yields are in part attributed to their loss as the solvent was removed in vacuo. Suprisingly, only single regioisomers were obtained. 3-Heptanone oxime 191 did, however, give a mixture of two isomers 192 and 193 (Equation 40). 

Because previous investigations showed that there is no syn-anti isomerization in oxime dianions , in contrast to dimethylhydrazone anion where a syn-anti mixture gives after lithiation only one (jy/i) monoanion, Ensley and Lohr checked the ability of the oxime ether to undergo isomerization of this type. An E and Z mixture of the 2-heptanone tetrahydropyranyl oxime gave, after lithiation and reaction with acetone, a substitution product only on the methyl group (equation 41). 

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