The present invention is directed to a process for the manufacture of 1,1,4,4-tetramethoxy-2-butene from 2,5-dimethoxy-2,5-dihydrofuran with methanol in the presence of an acidic ion exchanger as catalyst, whereby the molar ratio of 2,5-dimethoxy-2,5-dihydrofuran to methanol is ≥1:45. The present invention is further directed to a process of separating 1,1,4,4-tetramethoxy-2-butene, methanol and 2,5-dimethoxy-2,5-dihydrofuran from each other and H2O whereby a basic compound, preferably a basic metal salt or a basic ion exchanger, is present. Both processes can be carried out on an industrial scale, batch-wise or in continuous mode and are sustainable since the selectivity and the space-time-yields are high and less waste compared to known processes is produced. Further objects of the present invention are the use of a basic compound in the distillation of a mixture comprising H2O, 1,1,4,4-tetramethoxy-2-butene and 2,5-dimethoxy-2,5-dihydrofuran, as well as the use of an acidic ion exchanger as catalyst in a reaction of 2,5-dimethoxy-2,5-dihydrofuran with methanol to 1,1,4,4-tetramethoxy-2-butene, whereby the molar ratio of 2,5-dimethoxy-2,5-dihydrofuran to methanol is ≥1:45.

Provided are a method for efficiently producing an asymmetric conjugated diyne from an inexpensive and safe alternative compound to hydroxylamine hydrochloride and a method for producing a Z,Z-conjugated diene compound from the asymmetric conjugated diyne compound thus obtained. More specifically, provided is a method for producing an asymmetric conjugated diyne compound comprising a step of subjecting a terminal alkyne compound (1): HC≡C—Z.sup.1—Y.sup.1 to a coupling reaction with an alkynyl halide (2): Y.sup.2—Z.sup.2—C≡C—X by using sodium borohydride in water and an organic solvent in the presence of a copper catalyst and a base to obtain the asymmetric conjugated diyne compound (3): Y.sup.2—Z.sup.2—C≡C—C≡C—Z.sup.1—Y.sup.1. In addition, provided is a method for producing a Z,Z-conjugated diene compound by reducing the resulting asymmetric conjugated diyne compound, or the like.

Provided are a method for efficiently producing an asymmetric conjugated diyne from an inexpensive and safe alternative compound to hydroxylamine hydrochloride and a method for producing a Z,Z-conjugated diene compound from the asymmetric conjugated diyne compound thus obtained. More specifically, provided is a method for producing an asymmetric conjugated diyne compound comprising a step of subjecting a terminal alkyne compound (1): HC≡C—Z.sup.1—Y.sup.1 to a coupling reaction with an alkynyl halide (2): Y.sup.2—Z.sup.2—C≡C—X by using sodium borohydride in water and an organic solvent in the presence of a copper catalyst and a base to obtain the asymmetric conjugated diyne compound (3): Y.sup.2—Z.sup.2—C≡C—C≡C—Z.sup.1—Y.sup.1. In addition, provided is a method for producing a Z,Z-conjugated diene compound by reducing the resulting asymmetric conjugated diyne compound, or the like.

Provided are a method for producing a terminal conjugated dienal compound without an oxidation reaction and a terminal hydroxyacetal compound useful as an intermediate in the method. More specifically, provided are a method for producing an (E)-dienal compound comprising the steps of: a metalation reaction of an alkynal acetal compound (1) to obtain an organic metal compound (2), an addition reaction of (2) to ethylene oxide to obtain a hydroxyalkynal acetal compound (3), a reduction reaction of (3) to obtain an (E)-hydroxyalkenal acetal compound (4), a functional group conversion reaction of (4) to obtain an (E)-alkenal acetal compound (5) having a leaving group X, an elimination reaction of (5) to obtain an (E)-dienal acetal compound (6), and a hydrolysis reaction of (6) to obtain the (E)-dienal compound (7); and others.

##STR00001##

Provided are a method for producing a terminal conjugated dienal compound without an oxidation reaction and a terminal hydroxyacetal compound useful as an intermediate in the method. More specifically, provided are a method for producing an (E)-dienal compound comprising the steps of: a metalation reaction of an alkynal acetal compound (1) to obtain an organic metal compound (2), an addition reaction of (2) to ethylene oxide to obtain a hydroxyalkynal acetal compound (3), a reduction reaction of (3) to obtain an (E)-hydroxyalkenal acetal compound (4), a functional group conversion reaction of (4) to obtain an (E)-alkenal acetal compound (5) having a leaving group X, an elimination reaction of (5) to obtain an (E)-dienal acetal compound (6), and a hydrolysis reaction of (6) to obtain the (E)-dienal compound (7); and others.

##STR00001##

Provided are a terminal conjugated trienal acetal compound useful as an intermediate for producing a terminal conjugated trienal compound, and a method for producing a terminal conjugated trienal compound through deprotection of the terminal conjugated trienal acetal compound. More specifically, provided are a terminal conjugated trienal acetal compound represented by General Formula (1); a method for producing a (Z,E)-terminal conjugated trienal acetal compound, the method comprising the step of: reacting a phosphonium salt represented by General Formula (7) with (E)-2,4-pentadienal through Wittig reaction to obtain a (Z,E)-terminal conjugated trienal acetal compound represented by General Formula (3); and a method for producing a terminal conjugated trienal compound, the method comprising the step of: deprotecting the terminal conjugated trienal acetal compound represented by General Formula (1) to obtain a terminal conjugated trienal compound represented by General Formula (2).

##STR00001##

Provided are a terminal conjugated trienal acetal compound useful as an intermediate for producing a terminal conjugated trienal compound, and a method for producing a terminal conjugated trienal compound through deprotection of the terminal conjugated trienal acetal compound. More specifically, provided are a terminal conjugated trienal acetal compound represented by General Formula (1); a method for producing a (Z,E)-terminal conjugated trienal acetal compound, the method comprising the step of: reacting a phosphonium salt represented by General Formula (7) with (E)-2,4-pentadienal through Wittig reaction to obtain a (Z,E)-terminal conjugated trienal acetal compound represented by General Formula (3); and a method for producing a terminal conjugated trienal compound, the method comprising the step of: deprotecting the terminal conjugated trienal acetal compound represented by General Formula (1) to obtain a terminal conjugated trienal compound represented by General Formula (2).

##STR00001##

Provided are a terminal conjugated trienal acetal compound useful as an intermediate for producing a terminal conjugated trienal compound, and a method for producing a terminal conjugated trienal compound through deprotection of the terminal conjugated trienal acetal compound. More specifically, provided are a terminal conjugated trienal acetal compound represented by General Formula (1); a method for producing a (Z,E)-terminal conjugated trienal acetal compound, the method comprising the step of: reacting a phosphonium salt represented by General Formula (7) with (E)-2,4-pentadienal through Wittig reaction to obtain a (Z,E)-terminal conjugated trienal acetal compound represented by General Formula (3); and a method for producing a terminal conjugated trienal compound, the method comprising the step of: deprotecting the terminal conjugated trienal acetal compound represented by General Formula (1) to obtain a terminal conjugated trienal compound represented by General Formula (2).

##STR00001##

The present invention provides a process for preparing (9Z,11E)-9,11-hexadecadienal of the following formula (4), the process comprising: subjecting (2E)-2-heptenal of the following formula (1) to a Wittig reaction with a triarylphosphonium 9,9-dialkoxynonylide compound of the following general formula (2), wherein Ar represents an aryl group that may be same with or different from each other, and R.sup.1 and R.sup.2 represent, independently of each other, a monovalent hydrocarbon group having 1 to 15 carbon atoms, or R.sup.1 and R.sup.2 may form together a divalent hydrocarbon group, R.sup.1-R.sup.2, having 2 to 10 carbon atoms to form a (5E,7Z)-16,16-dialkoxy-5,7-hexadecadiene compound of the following general formula (3), wherein R.sup.1 and R.sup.2 are as defined above; and hydrolyzing the (5E,7Z)-16,16-dialkoxy-5,7-hexadecadiene compound (3) to form (9Z,11E)-9,11-hexadecadienal (4).

##STR00001##

The present invention provides a process for preparing (9Z,11E)-9,11-hexadecadienal of the following formula (4), the process comprising: subjecting (2E)-2-heptenal of the following formula (1) to a Wittig reaction with a triarylphosphonium 9,9-dialkoxynonylide compound of the following general formula (2), wherein Ar represents an aryl group that may be same with or different from each other, and R.sup.1 and R.sup.2 represent, independently of each other, a monovalent hydrocarbon group having 1 to 15 carbon atoms, or R.sup.1 and R.sup.2 may form together a divalent hydrocarbon group, R.sup.1-R.sup.2, having 2 to 10 carbon atoms to form a (5E,7Z)-16,16-dialkoxy-5,7-hexadecadiene compound of the following general formula (3), wherein R.sup.1 and R.sup.2 are as defined above; and hydrolyzing the (5E,7Z)-16,16-dialkoxy-5,7-hexadecadiene compound (3) to form (9Z,11E)-9,11-hexadecadienal (4).

##STR00001##