p-Toluenesulfonic acid → (-)-(4R,trans)-1-[2-(2,4-dichlorophenyl)-4,5-dimethyl-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole

Beteiligte Stoffe

Reaktionsschritte

A mixture of 9.5 parts of 1-[2(2,4-dichlorophenyl)-2,2-dimethoxyethyl]-1H-1,2,4-triazole 4-methylbenzenesulfonate, 2 parts of (2R, 3R)(-)-2,3-butanediol, 1 part of 4-methylbenzenesulfonic acid and 90 parts of methylbenzene is stirred and refluxed for 3 days. The reaction mixture is cooled and alkalized with a sodium hydroxide solution 20%. The whole is poured onto water and the product is extracted with dichloromethane. The extract is dried, filtered and evaporated. The residue is purified by column-chromatography over silica gel using ethyl acetate as eluent. The pure fractions are collected and the eluent is evaporated. The residue is crystallized from a mixture of 2,2'oxybispropane and petroleumether (1:1 by volume). The product is filtered off and dried, yielding 3.2 parts (50%) of (-)-(4R,trans)-1-[2-(2,4-dichlorophenyl)-4,5-dimethyl-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole; mp. 82.5° C.; [α]D =-30.26° (c=0.5% CHCl3)

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