Hydrochloric Acid → 2-(1,3,2-Dioxaborinan-2-yl)benzonitrile

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Reaction Conditions

Reaction Steps

Into a previously dried and inertised flask under nitrogen flow, fitted with a thermometer, reflux and a dropping funnel, are loaded 50.0 g (1.0 equiv.) of 2-bromobenzonitrile and 250 ml (5 V) of anhydrous Toluene. It is cooled at 0-5° C. and there are added, in 0.5 hours and maintaining the T at 0-5° C., 269.0 g (1.35 equiv.) of Isopropylmagnesium chloride/lithium chloride complex 1.3 M (about 20% wt/wt) in THF. It is stirred at T 0-5° C. and stirred for 1.5 hours. The conversion in checked in HPLC. If the reaction is complete there are added in 0.25 hours at 0-5° C., 57.0 g=61.3 ml (2 equiv.) of trimethylborate (d=0.932 g/ml). It is stirred at 0-5° C. for 0.25 hours and then allowed to warm to 20-25° C. and stirred for 0.25 hour. The conversion is checked in HPLC. If the reaction is complete, it is cooled to 0-5° C. and there is added at 0-10° C. a solution of hydrochloric acid 0.1 M prepared by mixing 5 ml of hydrochloric acid 32% (10.17 M) and 495 ml (9.9 V) of purified water. It is left under agitation 0.5 h at 20-25° C. and then the pH, which must be less than 5, is checked. If the pH is not less than 5, sufficient 10% HCl is added to correct the pH. It is stirred 0.25 hours and the phases are separated. The aqueous phase is again extracted with 250 ml (5 V) of Toluene. The organic phases, which are washed with 250 ml (5 V) of a saturated sodium chloride solution, are recombined. The phases are separated and the organic solution is sampled for HPLC checking. The organic phase is extracted with a soda solution 1 M (the product passes into aqueous phase), prepared by mixing 25 ml (0.5 V) of caustic soda solution 30% and 225 ml (4.5 V) of purified water. Before performing separation, check the pH which must be greater than 10. There is separation of the organic phase which is again re-extracted with caustic soda solution 1 M, prepared by mixing 25 ml (0.5 V) of caustic soda solution 30% and 225 ml (4.5 V) of purified water. Before performing separation, the pH, which must be greater than 10, is checked. There is separation of the organic phase which is again re-extracted with 1 M caustic soda solution, prepared by mixing 25 ml (0.5 V) of caustic soda solution 30% and 225 ml (4.5 V) of purified water. Before performing separation, the pH, which must be greater than 10, is checked. The aqueous phases which are washed with 2×100 ml (2×2 V) of ethyl acetate are recombined. The organic phase is discarded. The pH of the aqueous phase (containing the reaction product) is corrected with hydrochloric acid to a final pH of 6-7. The aqueous phase is extracted with 2×250 ml (2×5 V) of Ethyl acetate. The product passes into the organic phase. The organic phases are recombined and washed with 250 ml (5 V) of saturated solution of sodium chloride. The phases are separated and the organic solution is sampled for HPLC checking. There are added to the organic phase 23 g=21.8 ml (1.1 equiv.) of 1,3-propanediol (d=1.0597 g/ml). It is stirred at 20-25° C. for 2 h and the conversion in checked in TLC. If the reaction is complete, the aqueous phase is separated (water is generated during the reaction) and is concentrated to residue at Tbath 35-40° C. It is taken up with 250 ml (5 V) of Dichloromethane and the organic phase is washed with 50 ml (1.0 V) of purified water. It is concentrated to residue in Tbath 35-40° C. 150 ml (3.0 V) of n-Hexane are slowly added under agitation. The product crystallizes. It is stirred at 20-25° C. for 0.5 h and then at 0-5° C. for 0.5 h. It is filtered by washing with 50 ml (1.0 V) of n-Hexane pre-cooled to 0-5° C. It is vacuum dried at 20-25° C. for at least 8 h. There are obtained 23.0 g of 2-(1,3,2-dioxaborinane-2-yl)benzonitrile equal to a molar yield from 2-bromo benzonitrile of 44.8%. HPLC purity (A/A % 99.7%.).

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