GB812106A - Novel unsaturated ethers and a process for the manufacture thereof - Google Patents

Abstract

Unsaturated ethers of the general formula I <FORM:0812106/IV (b)/1> where R1 and R2 are each hydrogen or an alkyl group containing up to respectively 6 and 2 carbon atoms, U is an ethenyl or ethynyl radical, n is 1 or 2 and R is hydrogen or a hydrocarbon radical containing not more than 6 carbon atoms and which may only contain a triple bond in cases where U is an ethynyl radical are prepared by condensing a ketone of the general formula II (where n, R1 and R2 have the meanings given above) with an alkali metal acetylide M-C ­ CH (where M is an alkali metal atom and reacting the resulting alkali metal derivative of an acetylenic carbinol of the general formula III with an etherifying agent R3-CH2-A (where R3 is hydrogen or a hydrocarbon radical containing up to 6 carbon atoms and A is a strong mineral acid anion to give the ether IV. If a compound free of acetylenic linkages is required the ether IV is hydrogenated in the presence of a selective hydrogeneration catalyst to give the olefinic ether V (where R4 is a hydrocarbon radical containing up to 6 carbon atoms but which does not contain an acetylenic bond) <FORM:0812106/IV (b)/2> The ethers in which U is ethenyl only when R1 has an alkyl value are novel compounds and form an additional feature of the invention. In the above process the condensation step may be carried out in the presence of an inert solvent, e.g. toluene or diethyl ether, and the etherifying step may be carried out using a solution of the etherifying agent in an inert solvent, e.g. toluene or diethyl ether. The hydrogenation may be carried out in the presence of 1-15 per cent by weight of a Lindlar catalyst comprising a palladium/calcium carbonate catalyst upon which metallic lead has been deposited, room temperature and a moderate hydrogen overpressure are found to be suitable for the reduction of acetylenic bonds to olefinic bonds. In the examples the above method is used to prepare 1(A) derivatives of 3 : 7 dimethyl octen-(6) yne-1 from 6-methyl-hepten-5-one-2 where the product is substituted in the 3-position by methoxy, ethoxy, amyloxy, allyloxy, propargyloxy and benzyloxy groups; 1(B) the corresponding octadienes by hydrogenation; 2(A) 3 : 6 : 7-trimethyl - 3 - methoxy - octen - 6 - yne - 1- from 5 : 6 - dimethyl - hepten - 5 - one - 2; 2(B) the corresponding octadiene by hydrogenation; 3(B) 3 : 7 - dimethyl - 3 - methoxy - (and 3-ethoxy -) nonen - 6 - yne - 1 from 6 - methylocten - 5 - one - 2; 3(B) 3 : 7 - dimethyl - 3-methoxy - nonadiene - 1 : 6 by hydrogenation; 4(B) 3 : 7 : 9 - trimethyl - 3 - methoxy (and 3-allyloxy) - decen - 6 - yne - 1 from 6 : 8 - dimethyl - nonen - 5 - one - 2; 4(C) the correresponding decadienes by hydrogenation; 5(A) 3 : 7 : 11 - trimethyl - 3 - methoxy (and 3 - allyloxy) - dodecadien - 6 : 10 - yne - 1 from 6 : 10-dimethyl - undecadiene - 5 : 9 - one - 2; 5(B) 3 : 7 : 11 - trimethyl - 3 - methoxy - dodecatriene-1 : 6 : 10 by hydrogenation. The 6-methyl-octen-5-one-2 used as the starting material in Example (3) is prepared by treating 3-methyl-penten-1-ol-3 with hydrochloric acid to give 1-chloro-3-methyl-pentene-2, condensing the chloro compound with the sodium derivative of ethyl acetoacetate to give an a -keto ester, saponifying the ester and heating the a -keto acid to give the ketone 6 : 8-dimethyl nonen-5-one-2 is similarly prepared from 3 : 5-dimethyl-hexen-1-ol-3. Specification 667,552 is referred to.