A method of production of malic acid includes treating a first intermediate product to form a second intermediate product. The treating includes substantially removing impurities from the first intermediate product to obtain a treated intermediate product by gas stripping the crude maleic anhydride, or subjecting a mixture of one or more of the crude maleic acid, the crude fumaric acid, and the vent gas scrubber solution obtained from a phthalic anhydride production process or a maleic anhydride production process to crystallization, passing an aqueous solution of the treated intermediate product through a carbon column to substantially remove retained impurities to form the second intermediate product, obtaining a feed that includes the second intermediate product, and causing the feed to undergo hydration reaction in a tubular reactor or a continuous stirred tank reactor to produce malic acid.

The present invention relates to an improved process for the preparation of [[2(S)-[[4(R)-(3-hydroxyphenyl)-3(R),4-dimethyl-1-piperidinyl]methyl]-1-oxo-3-phenylpropyl]amino]acetic acid dihydrate, represented by the following structural formula (I).

The present invention relates to an improved process for the preparation of [[2(S)-[[4(R)-(3-hydroxyphenyl)-3(R),4-dimethyl-1-piperidinyl]methyl]-1-oxo-3-phenylpropyl]amino]acetic acid dihydrate, represented by the following structural formula (I).

Processes for producing 2,5-dichlorophenol and 3,6-dichloro-2-methoxybenzoic acid are described. Various processes for isomerizing 2,4-dichlorophenol over a zeolite catalyst to form 2,5-dichlorophenol are provided. Processes for preparing 2,5-dichlorophenol including hydroxylating 1,4-dichlorobenzene are also described. The present invention also relates to processes for producing 3,6-dichloro-2-methoxybenzoic acid.

Processes for producing 2,5-dichlorophenol and 3,6-dichloro-2-methoxybenzoic acid are described. Various processes for isomerizing 2,4-dichlorophenol over a zeolite catalyst to form 2,5-dichlorophenol are provided. Processes for preparing 2,5-dichlorophenol including hydroxylating 1,4-dichlorobenzene are also described. The present invention also relates to processes for producing 3,6-dichloro-2-methoxybenzoic acid.

Processes for producing 2,5-dichlorophenol and 3,6-dichloro-2-methoxybenzoic acid are described. Various processes for isomerizing 2,4-dichlorophenol over a zeolite catalyst to form 2,5-dichlorophenol are provided. Processes for preparing 2,5-dichlorophenol including hydroxylating 1,4-dichlorobenzene are also described. The present invention also relates to processes for producing 3,6-dichloro-2-methoxybenzoic acid.

The invention provides a method for the preparation of regioisomerically pure intermediates which are useful for the preparation of carboxy-fluorescein-type compounds. Such compounds have broad applications within bio-conjugation and/or fluorescent imaging.

The invention provides a method for the preparation of regioisomerically pure intermediates which are useful for the preparation of carboxy-fluorescein-type compounds. Such compounds have broad applications within bio-conjugation and/or fluorescent imaging.

The present invention relates to the technical field of organic chemistry, specifically an asymmetrical hydrogenation of an ∂-ketonic acid compound, the technical proposal being as shown by the following formula:

##STR00001##

Wherein R.sup.1 is a phenyl, a substituted phenyl, a naphthyl a substituted naphthyl, a C.sub.1-C.sub.6 alkyl or aralkyl, the substitute is a C.sub.1-C.sub.6 alkyl, a C.sub.1-C.sub.6 alkoxy, a halogen, the number of the substituents is 1-3.

M is a chiral spiro-pyridyl amido phosphine ligand iridium complex having the following structure,

##STR00002##

Wherein, R is hydrogen, 3-methyl, 4-.sup.tBu or 6-methyl

The present invention relates to the technical field of organic chemistry, specifically an asymmetrical hydrogenation of an ∂-ketonic acid compound, the technical proposal being as shown by the following formula:

##STR00001##

Wherein R.sup.1 is a phenyl, a substituted phenyl, a naphthyl a substituted naphthyl, a C.sub.1-C.sub.6 alkyl or aralkyl, the substitute is a C.sub.1-C.sub.6 alkyl, a C.sub.1-C.sub.6 alkoxy, a halogen, the number of the substituents is 1-3.

M is a chiral spiro-pyridyl amido phosphine ligand iridium complex having the following structure,

##STR00002##

Wherein, R is hydrogen, 3-methyl, 4-.sup.tBu or 6-methyl