Preparation of Ethyl NitriteMix 288g of 95% ethanol (190 Proof/Everclear) with 290mL of dH2O and 300g 98% H2SO4 and chill in the freezer. In a 2L RBF with a magnetic stirbar, dissolve 227.7g sodium nitrite in 725mL dH2O and cool in the freezer for a few hours, without freezing the solution (some precipitation will occur). Place the RBF in a -10C ice bath. Add the ethanol/water solution to an addition funnel positioned above the RBF. Add the ethanol solution dropwise to the nitrite solution over a period of 1-2h {with gentle stirring}, and monitor the temperature of the solution, assuring that it does not rise above 6-9C. Once the addition is complete, allow the solution to cool in the bath, and filter out the precipitated sodium sulfate in a chilled buchner funnel/filtering flask (use very low vacuum, or the ethyl nitrite will boil away), and wash the filter cace with a little ice-cold 95% ethanol. Remove the flask and pour the contents into a 2L separatory funnel which has been chilled in the freezer, remove the aqueous layer, and wash the nitrite with 500 mL of a 5% sodium bicarbonate solution which has been chilled in the freezer. Drain the nitrite into a 2L RBF and add anhydrous, denatured ethanol to bring the final volume to 1L. Dry over 100g sodium sulfate for 15 minutes, filter, and rinse the cake with ~100mL ethanol. {You must dilute before filtering or the ethyl nitrite will froth violently and you will get loopy
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Nitrite WackerTake the ethyl nitrite solution from above, bring the total volume to 2L with anhydrous ethanol {Used denatured anhydrous, 5% MeOH, or make your own from 95% and CaO}, and place in a 4L filter flask, stoppered, with a tube leading from the outlet into a jug of 2% HCl. Add 2.65g PdCl2 (0.015 moles) and 10.08g CuCl2 (0.075 moles, anhydrous) to the flask and gently warm the flask to ~30C. Add 325g of fractionally distilled safrole (2 moles) to the flask, and continue stirring for 8h at 30C. Once complete, add 500mL H2O to the flask and raise the temperature to 50C, holding it there for 40 minutes. When this is done, filter the contents over celite, rinse with 100mL EtOH, and optionally roto-vap off ~1200 mL of the EtOH. Flood the contents with 1200mL of 5% HCl and extract the precipitated ketone 3x with 400 mL of DCM. Wash the pooled extracts with water, saturated sodium bicarbonate solution, and brine. Filter the organic phase through celite to remove some residual, precipitated metals. Dry the extract over sodium sulfate, filter, and rinse the cake with DCM. Rotary evaporate the solvent at atmospheric pressure at the steam bath, then fractionally distill the piperonylacetone over a 300mm column packed with glass beads at 10.0 mmHg (149-152C). Optionally, run a chaser to clear the column, or extract and distill with a smaller rig/shorter path. Store the pure ketone in an equal volume of anhydrous methanol, under nitrogen, in the freezer. Weight of piperonylacetone; 321.5g, 83.5%.
Don't forget to use a water-trap to prevent suck-back should it occur!!!
I believe there may have been additional piperonylacetone which wasn't collected, or it might have been mostly contaminant. This was by no means a first shot at the nitrite. An aspiring young neophyte, a KrZ apprentice, allowed a retiree to conduct some small tinkerings with it on his premises, and this is the scale-up of the most fruitful of these meanderings. Methyl nitrites produced unsatisfactory results, and were quite malodorous during the gassing. Perhaps this was due to escaping MeONO, and yes, that was with a diffusion tube into cold MeOH. I don't care what any of you say, bubbling gases into solutions, no matter how cold, is no way to go about things. n-Butyl nitrites proceeded according to the patent {w/o cocatalyst} but that damn nBuOH stinks to hell and annoys me in general. Isopropyl nitrites were too hindered to form the dialkoxides effectively {my theory, yields sucked regardless}. Ethyl nitrite was settled on, and while aq. solutions worked effectively with no cocatalyst {as with MeONO & nBuONO}, the turnover thing just wasn't happening. We upped the nitrite concentration to no alleive, then went with anhydrous conditions, and acheived suitable results. There was still a lag time of 1-2h with the above conditions.
After this there has been some tinkering with the sulfided Pt catalyst, including atmospheric hydrogenations and ground-up catalyst preparation. Hopefully that will be detailed soon, although there are still a few optimizations to investigate.
