Fenpropimorph synthesis

Yield:67564-91-4 0.14%

Reaction Conditions:

Stage #1:(2R,6S)-2,6-dimethyl-4-(2-methyl-3-phenylpropyl)morpholine hydrochloride with iron(III) chloride in dichloromethane
Stage #2:2-methyl-2-butylchloride in dichloromethane at -52 - -20;
Stage #3: with sodium hydroxide;waterProduct distribution / selectivity;more than 3 stages;

Steps:

2a
a) General considerations:1 part bepromoline.HCl is treated with 1.3 parts FeCl₃ +5% in dichloromethane at room temperature. The resulting slurry is cooled to approximately - 15 50⁰C, whereupon 1 to 1.1 parts of 2-chloro-2- methylbutane is added.After an appropriate reaction time of around 2.5 hours, the reaction mixture is poured onto an ice-20. water mixture. The organic phase is separated and washed with acidic water, and then with sodium phosphate solution and with sodium hydroxide solution. After a stripping with toluene, extractions with water are performed. The solvent25 is then removed. Then the residue is distilled.Schematic of Production of Amorolfine Base:M MoI. Wt.: 106.59 EPO Reaction Temperature for the addition of FeCl3 toBepromoline HClThe addition of FeC13 to Bepromoline HCl takes place at room temperature. At lower temperatures the subsequent Friedel-Crafts alkylation fails partially or completely (Table 1)Table 1Friedel-Crafts CatalystsA suitable molar ratio of FeCl₃ to bepromoline is 1:2 to 1:5 equivalents of catalyst. 1.3 equivalents of FeCl₃ is preferred.Reaction Temperature for Friedel-Crafts Alkylation To decrease the fenpropimorph (FPM) by-product, the reaction is conducted at low temperature, preferably -50⁰C (see Table 2) :Fenpoprimorph (FPM)Table 2 EPO Fenpropimorph (FPM) is a problematic by-product as it is difficult to remove from the end product.Ratio of Bepromoline HCl to 2-chloro-2-methylbutane Batches were performed with 10 % excess 2-chloro-2- methylbutane and at a 1:1 ratio. The FPM assay is lower for the 1:1 ratio and thus this proportion is preferred.Phosphate and Alkaline ExtractionThe Amorolfine HCl (which is in the DCM) is converted to the free base during these extractions. Phosphate was used to remove traces of Fe.Solvent ExchangeAdvantages result if the solvents are exchanged (i.e. toluene in place of DCM) : the volume is reduced and the waste-water is contaminated with less chlorinated solvent.Toluene-water ExtractionThose extractions are necessary to get the appropriate quality for the subsequent distillation. If these extractions are omitted, the Amorolfine base slightly decomposes at 180⁰C. The distillation become very sluggish and fumes are formed. The vacuum distillation is then not possible at plant scale. EPO The yield was approximately 90% of crude Amorolfine base .

References:

GALDERMA S.A. WO2007/12983, 2007, A2 Location in patent:Page/Page column 13-16

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