I am trying to follow a published paper. It is a one-pot synthesis of pyrazole from a ketone and and acid chloride via a diketone intermediate.
Here is the produre from the paper:
General Procedure: Ketone (2 mmol) was dissolved in 5 mL dry toluene in a screw cap vial (with septum) and then the solution was cooled to 0°C under nitrogen. LiHMDS(2.1 mL, 1.0 M in THF, 2.1 mmol) was added quickly via syringe with agitation stirring and the formed anion was allowed to sit for approximately 1 minute before the addition via syringe of acid chloride (1 mmol) in one portion with stirring. The vial was then removed from the ice bath and allowed to stand for 1 minute, then 2 mL AcOH was added with stirring. 10 mL EtOH and 5 mL THF was added to form a homogeneous mixture, and then hydrazine hydrate (2 mL, 1.1 g, 34.3 mmol) or substituted hydrazine(5 mmol) was added and the mixture was allowed to auto-reflux and was held at that temperature for 5 minutes, when LCMS showed that all diketone had reacted. The resulting solution was added to 1.0 M NaOH solution and extracted with EtOAc. The organic fraction was then washed with brine, dried over Na2SO4, and evaporated under reduced pressure.See specific compounds for purification details.
My questions are:
- What is the purpose of excess hydrazine hydrate, acetic acid, and enolate in producing the pyrazole?
- How many molar equivalents of sodium hydroxide should I use at the end of the reaction?