Patent GB-1111193-A (GB)
Title: Preparation of polyenes
Inventor: HALL DAVID WARREN
IPC: C07C11/18
Filed: 1966-05-24
Abstract: Di- and tri-enes are produced by reacting the corresponding mono- or di-enes with a haloether to form an adduct (see Division C2), which is then cleaved to split off hydrogen halide and an alcohol to produce the di- or tri-ene.  The cleavage is preferably carried out in one step by heating in the presence of either a solvent or a complexing agent for the hydrogen halide. Alternatively, a two-stage process may be employed, the first stage being dehydrohalogenation to form an olefinic ether, and the second stage involving cracking of the olefinic ether to form the desired polyene. The following products are made:  Isoprene by cleavage of the adduct isobutylene/chloromethyl methyl ether, either in one stage in the presence of N-methyl pyrrolidone, dimethyl formamide or tertbutyl alcohol; or in two stages, the first being dehydrochlorination in the presence of aniline to give 3-methyl-3-butenyl methyl ether, which is then cracked using a ZnO/SiO2 catalyst.  Isoprene by cleavage of the adduct 2-butene/chloromethyl methyl ether in the presence of N-methyl pyrrolidone and lithium chloride.  2,3-dimethyl-1,3-butadiene by cleavage of the adduct 2-methyl-2-butene/chloromethyl methyl ether in the presence of N-methyl pyrrolidone.  2-phenyl-1,3-butadiene by cleavage of the adduct a -methyl styrene/chloromethyl methyl ether at 550 DEG  C.  Piperylene by cleavage of the adduct 1-butene/chloromethyl methyl ether in the presence of N-methyl pyrrolidone and a metal halide.  2,5-dimethyl-2,4-hexadiene by cleavage of the adduct isobutylene/1-chloro-2-methylpropyl methyl ether in the presence of N-methyl pyrrolidone.  2-vinyl-1,3-butadiene by cleavage of the adduct isoprene/chloromethyl methyl ether in the presence of N-methyl pyrrolidone.  Chloroprene is also prepared (see Division C2).ALSO:Di- and tri-enes, which may contain halogen substituents, are produced by reacting the corresponding mono- or dienes with a halo-ether to form an adduct which is then cleaved to split off hydrogen halide and an alcohol to produce the di- or tri-ene.  The haloether adduction may be carried out in the presence of a FriedelCrafts catalyst in the liquid phase, optionally in the presence of a solvent.  The cleavage may be a one-stage process in which the adduct is heated in the presence of either a solvent or a complexing agent for the hydrogen halide. Alternatively, a two-stage process may be employed in which the adduct is first dehydrohalogenated to form an olefinic ether, which is then cracked to form the polyene, suitable conditions being given.  The following adducts are prepared:-  A.  3-Chloro-3-methylbutyl methyl ether.  B. 3 - Chloro - 2,3 - dimethylbutyl methyl ether.  C.  2 - Chloro - 2 - phenyl - butyl methyl ether.  D.  3-Chloropentyl methyl ether.  E.  3 - Chloro - 2 - methylbutyl methyl ether.  F.  2,5 - Dimethyl - 2 - chloro - 4 - methoxy hexane.  G.  3,3-Dichlorobutyl methyl ether.  H. 2,3-Dichlorobutyl methyl ether.  J.  3 - Methyl - 5 - chloro - 3 - pentenyl methyl ether.  Dehydrochlorination of A in the presence of aniline yields 3-methyl-3-butenyl methyl ether.  Chloroprene is prepared by cracking G or H, or by heating G or H with N-methyl pyrrolidone and lithium chloride.  A typical haloether starting material, chloromethyl methyl ether, is made by reaction of methanol, paraformaldehyde and either HCl or chlorosulphonic acid.  A product which is 3-methyl-2,4-pentadienyl methyl ether and/or 1-methoxyethyl-1-vinyl ethylene is obtained by heating J with N-methyl-2-pyrrolidone.