Patent GB-859567-A (GB)
Title: Production of unsaturated derivatives of 2,6-dimethyl octanes
IPC: C07C21/04
Filed: 1957-04-03
Abstract: The invention comprises unsaturated derivatives of 2.6-dimethyl octanes having the general formula:  <FORM:0859567/IV(b)/1> in which in section ??? of the molecule two of the unsatisfied valences form a double bond and the remainder are satisfied by hydrogen, and x is a halogen, hydroxyl, alkoxy or an acyloxy radical, the acyloxy radical being derived from a carboxylic acid.  They are prepared by reacting under strongly acidic conditions a diene of general formula: <FORM:0859567/IV(b)/2> in which section ??? of the molecule is as defined above and in section ??? two of the unsatisfied valences form a double bond and the others are satisfied by hydrogen, with a compound of general formula HX in which X is a halogen, alkoxy or alkoxy radical and, if desired, hydrolysing the product to give a compound of formula I in which X is a hydroxyl group.  Preferably the reaction with the compound HX is carried out at 15-45 DEG  C.  When X is acyloxy suitable compounds of formula HX are formic, acetic and chloroacetic acids.  In some cases a mineral acid catalyst, for example sulphuric acid, is necessary.  Lower ethers are readily produced by treating the hydrocarbon with the corresponding alcohol in the presence of a mineral acid catalyst.  The higher ethers can be produced more readily by reacting the sodium salt of 2,6-dimethyloctene-2-ol with an alkylating agent such as an alkyl halide or sulphate or alternatively by reacting an alkoxide with a 2,6-dimethylocten-2-yl halide.  The 2,6-dimethylocten-2-yl chlorides and bromides are made by passing the corresponding anhydrous hydrohalide gas into the diene.  The products may be converted to compounds useful in perfumery.  For example a 2,6-dimethyl-6-octen-2-yl alcohol, ester, halide or ether is treated with ozone to give the corresponding methyl heptanone from which water, acid, hydrohalic acid or alcohol is split off to give 2-methyl-1-hepten-6-one or 2-methyl-2-hepten-6-one as follows : <FORM:0859567/IV(b)/3> The latter ketone on treatment with acetylene in the presence of sodamide yield dehydrolinalool which on selective hydrogenation yields linalool.  Linalool may be oxidised with chromic acid to give citral.  2,6-Dimethyl-7-octen-2-yl-alcohol on treatment with ozone cleaves at the 7-position to give the hydroxy aldehyde which on dehydration gives 2,6-dimethyl-1-hepten-7-al and 2,6-dimethyl-2-hepten-7-al.  Examples are given of the preparation of 2,6-dimethyl-6-octene-2-ol, 2,6-dimethyl-6-octene -2-yl acetate, 2-methyl-6-methylene-2-yl acetate, 2-chloro-2,6-dimethyl-7-octene, 2,6-dimethyl-4-octene-2-ol, 2,6-dimethyl-3-octene-2-ol, 2,6-dimethyl-7-octene-2-ol, 2-methoxy-2,6-dimethyl-7-octene and 2-bromo 2,6-dimethyl-7-octene.  Starting materials are produced as follows :-(a) myrcene is hydrogenated using a Rufert nickel catalyst to give 2-methyl-6-methylene-2-octene ; (b) myrcene is hydrogenated using a palladium-on-carbon catalyst to give 2,6-dimethyl-2,6-octadiene ; (c) alloocimene "A" is hydrogenated using a PtO2 catalyst to give 2,6-dimethyl-2,4-octadiene and (d) 2,6-dimethyl-7-octene-2-ol is treated with formic acid and the ester formed is heated to give 2,6-dimethyl-1,7-octadiene and 2,6-dimethyl-2,7-octadiene.  Specification 859,568 is referred to.