13  US 9,926,580 B2  14  Preferred are methyl formate, ethyl formate, propyl formate,  butyl formate, isobutyl formate, pentyl formate, and the like.  Most preferred is ethyl formate.  The ethers are not particularly restricted, and may be  cyclic or acyclic, or saturated or unsaturated. But saturated  ones are preferably used in general. Generally, ones con› taining 3 to 20 carbon atoms, preferably  4  to 12 carbon  atoms and more preferably  4  to 8 carbon atoms are used. As  specific examples, there may be mentioned, for example,  diethyl ether, methyl tert-butyl ether, dipropyl ether, diiso› propyl ether, dibutyl ether, dihexyl ether, ethyl vinyl ether,  butyl vinyl ether, anisol, phenetole, butyl phenyl ether,  methoxytoluene, dioxane, furan, 2-methylfuran, tetrahydro› furan, tetrahydropyran, ethylene glycol dimethyl ether, eth› ylene glycol diethyl ether, ethylene glycol dibutyl ether,  ethylene glycol monomethyl ether, ethylene glycol mono› ethyl ether, ethylene glycol monobutyl ether, and the like.  Preferred are diethyl ether, methyl tert-butyl ether, dipropyl  ether, diisopropyl ether, dibutyl ether, dihexyl ether, anisol,  phenetole, butyl phenyl ether, methoxytoluene, dioxane,  2-methylfuran, tetrahydrofuran, tetrahydropyran, ethylene  glycol dimethyl ether, ethylene glycol diethyl ether, ethylene  glycol dibutyl ether, ethylene glycol monomethyl ether,  ethylene glycol monoethyl ether, and the like. More pre› ferred are diethyl ether, methyl tert-butyl ether, anisol,  dioxane,  tetrahydrofuran,  ethylene glycol monomethyl  ether, ethylene glycol monoethyl ether, and the like. Still  more preferred are diethyl ether, methyl tert-butyl ether,  anisol, and the like, and most preferred is methyl tert-butyl  ether.  The alcohols are not particularly restricted but may be  cyclic or acyclic, or saturated or unsaturated. Saturated ones  are generally preferred, however. Generally, ones containing  1  to 20 carbon atoms, more preferably  1  to 12 carbon atoms,  and still more preferably  1  to 6 carbon atoms are used. 35  Among them, monohydric alcohols containing  1  to 5 carbon  atoms, dihydric alcohols containing 2 to 5 carbon atoms, and  trihydric alcohols containing 3 carbon atoms are preferred.  As specific examples of these alcohols, there may be  mentioned, for example, monohydric alcohols such as  methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-bu› tanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pen› tanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol,  tert-pentyl alcohol, 3-methyl-2-butanol, neopentyl alcohol,  1-hexanol,  2-methyl-1-pentanol,  4-methyl-2-pentanol,  2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-oc› tanol, 2-octanol, 2-ethyl-1-hexanol, 1-nonanol, 1-decanol,  1-undecanol, 1-dodecanol, ally! alcohol, propargyl alcohol,  benzyl  alcohol,  cyclohexanol,  1-methylcyclohexanol,  2-methylcyclohexanol, 3-methylcyclohexanol, 4-methylcy- clohexanol, and the like; dihydric alcohols such as 1,2- ethanediol, 1,2-propandiol, 1,3-propandiol, 1,2-butanediol,  1,3-butanediol,  1,4-butanediol,  2,3-butanediol,  1,5-pen› tanediol, and the like; and trihydric alcohols such as glyc› erol, and the like.  As the monohydric alcohols, preferred are methanol,  ethanol,  1-propanol,  2-propanol,  1-butanol,  2-butanol,  isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol,  3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, tert-pen- tyl alcohol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexa- no!, 2-methyl-1-pentanol, 4-methyl-2-pentanol, 2-ethyl-1- butanol,  1-heptanol, 2-heptanol,  3-heptanol,  1-octanol,  2-octanol, 2-ethyl-1-hexanol, 1-nonanol, 1-decanol, 1-unde› canol, 1-dodecanol, benzyl alcohol, cyclohexanol, 1-meth› ylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexa- no!, 4-methylcyclohexanol, and the like. More preferred are  methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-bu- In selecting the organic solvent to be used from among the  organic solvents mentioned above, such properties as boil- As the sulfur compounds, there may be mentioned, for  example, dimethyl sulfoxide, sulfolane, and the like.  As the nitrogen compounds other than nitriles, there may  be mentioned, for example, amides such as formamide,  N-methylformamide, N, N-dimethylformamide, N,N-dim› ethylacetoamide, N-methylpyrrolidone, and nitromethane,  triethylamine, pyridine, and the like.  Preferred are acetonitrile, propiononitrile, succinonitrile,  butyronitrile, isobutyronitrile, valeronitrile, methyl cyano- acetate, ethyl cyanoacetate, benzonitrile, tolunitrile and  chloropropiononitrile. More preferred are acetonitrile, pro› piononitrile, butyronitrile and isobutyronitrile, and most  preferred is acetonitrile.  As specific examples, there may be mentioned, for  example, acetonitrile, propiononitrile, malononitrile, buty› ronitrile, isobutyronitrile, succinonitrile, valeronitrile, glu› taronitrile, hexanenitrile, heptylcyanide, octylcyanide, unde› canenitrile,  dodecanenitrile,  tridecanenitrile,  pentadecanenitrile, stearonitrile, chloroacetonitrile, bromo- acetonitrile,  chloropropiononitrile, bromopropiononitrile,  methoxyacetonitrile, methyl cyanoacetate, ethyl cyanoac- etate,  tolunitrile,  benzonitrile,  chlorobenzonitrile,  bro› mobenzonitrile,  cyanobenzoic  acid,  nitrobenzonitrile,  anisonitrile, phthalonitrile, bromotolunitrile, methyl cya› nobenzoate, methoxybenzonitrile, acetylbenzonitrile, naph› thonitrile, biphenylcarbonitrile, phenylpropiononitrile, phe- nylbutyronitrile,  methylphenylacetonitrile,  diphenylacetonitrile,  naphthylacetonitrile,  nitrophenylac› etonitrile, chlorobenzylcyanide, cyclopropanecarbonitrile,  cyclohexanecarbonitrile, cycloheptanecarbonitrile, phenyl› cyclohexanecarbonitrile, tolylcyclohexanecarbonitrile, and  the like.  The nitriles are not particularly restricted, and may be  cyclic or acyclic, or saturated or unsaturated. However,  saturated ones are preferably used in general. Generally,  ones containing 2 to 20 carbon atoms, preferably 2 to 12  carbon atoms, and more preferably 2 to 8 carbon atoms are  used.  The ketones are not particularly restricted, and ones  having 3 to 6 carbon atoms are preferably used. As specific  examples, there may be mentioned, for example, acetone,  methyl ethyl ketone, methyl butyl ketone, methyl isobutyl  ketone, and the like. Preferred are acetone and methyl ethyl  ketone, and most preferred is acetone.  As fatty acids, there may be mentioned, for example,  formic acid, acetic acid, propionic acid, and the like. Pre- ferred are formic acid and acetic acid, and most preferred is  acetic acid.  As the dihydric alcohols, preferred are 1,2-ethanediol,  1,2-propandiol, 1,3-propandiol, and the like. Most preferred  is 1,2-ethanediol. As the trihydric alcohols, glycerol is  preferred.  tanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pen› tanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol,  tert-pentyl alcohol, 3-methyl-2-butanol, neopentyl alcohol,  1-hexanol,  2-methyl-1-pentanol,  4-methyl-2-pentanol,  2-ethyl-1-butanol, cyclohexanol, and the like. Still more  preferred are methanol, ethanol, 1-propanol, 2-propanol,  1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol,  1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, iso› pentyl alcohol, tert-pentyl alcohol, 3-methyl-2-butanol, neo- pentyl alcohol, and the like. Particularly preferred are  methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-bu› tanol, isobutyl alcohol, 2-methyl-1-butanol, isopentyl alco› hol, and the like. Most preferred is 2-propanol. 