摘要:
Process for preparing esters of alkanoic acids via rearrangement of alpha-haloketals in the presence of a Lewis acid.The rection is preferably carried out in the presence of catalytic amounts of a Lewis acid and of a diluent at a temperature in the range from about 0.degree. to the reflux temperature of diluent.The esters thus obtained are useful as intermediate products for preparing drugs.The process involves the preparation of new alpha-haloketals.
摘要:
A process is disclosed for the preparation of optically active alpha-arylalkanoic acids, consisting in the rearrangement of optically active (alpha-haloalkyl)-aryl-ketals and in submitting to hydrolysis the thus obtained esters of alpha-arylalkanoic acids. The rearrangement reaction is carried out under neutral or alightly alkaline conditions, in an aprotic dipolar diluent and in the presence of a protic substance having a high dielectric constant.
摘要:
Rearrangement of alpha-halo-alkylarylketals in neutral or weakly alkaline conditions and in the presence of a polar-protic medium and subsequent hydrolysis of the thus obtained esters, in the same reaction medium, to afford the corresponding alpha-arylalkanoic acids or their salts which are particularly useful as anti-inflammatory, analgesic and antipyretic agents.
摘要:
Compositions comprising 1,3,5-oxathiazine derivatives and which are highly effective against nematodes but exhibit low toxicity for warm-blooded animals are disclosed.
摘要:
A method is described for the preparation of aryl-pyridine compounds of formula (I) by cross-coupling reaction, promoted by catalytic systems based on palladium or nickel between compounds of formula (II) and (III) in which: -Met represents Mg or Zn, —Y represents Cl, Br, I or acetoxy, —Z represents I, Br, Cl, triflate, sulphonate, phosphate, —R1, R2, R3, R4, which are the same as one another or different, represent hydrogen, a linear and/or branched C1-C4 alkyl, and/or an aryl, and/or a heteroaryl, or R1 and R2 and/or R3 and R4, taken together, form a C3-C8 ring, an aryl and/or a heteroaryl, -A represents —COR5 where R5 represents hydrogen, a linear and/or branched C1-C4 alkyl, and/or an aryl, and/or a heteroaryl, or -A represents —CRs5(OR6)(OR7) where R5 has the meaning described above and R6 and R7, which are the same as one another or different, represent a linear and/or branched C1-C4 alkyl, and/or an aryl, and/or a heteroaryl, or R6 and R7, joined together, represent a C1-C8 alkyl or alkenyl.
摘要:
A process for the preparation of the compounds of formula (wherein R has the meanings reported in the specification) by enzymatic transesterification of enantiomeric mixtures is described. These compounds are intermediates useful in the synthesis of Diltiazem.
摘要:
Intermediates for transforming (2S,3S)-2-amino-3-phenyl-1,3-propanediols into their (2R,3R)-enantiomers are described. The final compounds are useful intermediates for the synthesis of antibiotics like chloramphenicol, Thiamphenicol and Florfenicol.
摘要:
A crystallization process of crude 5-(2',4'-difluorophenyl)-salicylic acid from a mixture of an aromatic hydrocarbon and an aliphatic ketone for preparing 5-(2',4'-difluorophenyl)-salicylic acid in form II substantially pure is described.
摘要:
A process for preparing 2,6-di-t-butyl-4-mercapto-phenol. This is accomplished by sulfonation of the phenol with a silylated sulfonating agent (e.g., trimethylsilyl-chlorosulfonate). The sulfonic acid is then reduced directly or is converted to the sulfonyl halide intermediate which is then reduced to yield the 2,6-di-t-butyl-4-mercapto-phenol.
摘要:
A process is described for preparing an intermediate in the synthesis of naproxen.The intermediate, namely the methyl ester of S(+)-2-(5-bromo-6-methoxy-2-naphthyl)-propionic acid or of its 5-chloro analogue, is prepared by preferential crystallization from mixtures with its enantiomer.