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Osmium/BrightStar Al/Hg Methylamine Reductive Amination

by RoundBottom (with much help and thanks to Chromic)
(format & minor edits by metanoid)
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Reagents

(the first amount is the actual amount measured, the amounts in brackets are the desired/calculated amounts)

55.2g (53.4g) MDP2P [1]
66.9g (66.8g) Methylamine.HCl [2]
39.6g (39.6g) 98% NaOH
423mL (420mL) MeOH
26.1g (26.7g) Al Foil [3]
141mg (150mg) HgCl2
230g KOH [4]
dH2O

Equipment

1000mL 1N RBF
allihn condenser
claissen adapter
them and adapter
1" egg bar
mantle and controller
cooling setup

Short Form:

mixed 66.8g MeAm.Hcl in 67g dH2O
mixed 39.6g NaOH in 119g dH2O, cooled in ice bath
mixed 423mL MeOH, 26.1g Al foil, 140mg HgCl2 in RBF
slowly poured NaOH solution into MeAm solution, then added to RBF
added ketone to RBF
refluxed with mixing until slowed down and temp started dropping, then added heat to keep at ~65C
strained unreacted foil
basified with KOH solution (230g 85% KOH, 469g dH2O)
extracted 1x 500mL, 1x 200mL toluene
washed toluene 3x 700mL dH2O, 1x 700mL brine
dried 10 minutes in 40g MgSO4
gassed and vacuum filtered 5x, cleaned in boiling acetone, vacuum filtered, dried
yield 50.99g

Procedure

Mixed 66.9g MeAm was with 67mL (67mL) dH2O. Mixed 39.6g NaOH with 119g (119mL) dH2O, and cooled in ice bath.

Set up equipment, started cooling, added stir bar. Put 26.1g Al foil in RBF. Added most of the 423mL MeOH to the RBF, saving about 50mL to wash out the ketone container. About 140mg of HgCl2 was then added to the RBF and the whole flask was swirled to mix the HgCl2 into the MeOH.

Once the MeOH started bubbling (about 5 minutes after the addition of the HgCl2), the cool NaOH solution was slowly poured into the MeAm solution. The smell of MeAm gas was now very strong. The basified MeAm solution, and the 55.2g ketone were then poured into the RBF. The remaining MeOH was swirled in the ketone flask and added to the RBF, and the whole flask was swirled a few times to mix everything.

This reaction is nowhere near as exothermic as a Methyl Man Al/Hg Nitromethane. The fact that 55g of ketone (~300mmol) can be comfortably converted in a 1L flask says it all.

Stirring was attempted, but the bar would not move, probably due to the Al foil weighing it down. Different stirrers were tried, but to no avail. During the reflux the solution was bubbling quite well, but was still diligently swirled a couple times every five minutes. After the reflux subsided, the flask was swirled approximately every 15 minutes. When a top layer of clear fluid started forming, that means it's time to swirl.

The temperature rose quickly to about 72C with lots of foil floating on the top, and lots of bubbles were evolving, but it stayed in control. This is with all the ketone added at once. See below for a full temperature readout.

The reaction was left to run for 4.5 hours, and began to calm down after about 45 minutes from the addition of the ketone. When it calms down a bit, prepare the basification solution (230g 85% KOH added to 469mL dH2O) to give it time to cool. Heat was added to the RBF after about 75 minutes to get the temperature up to about 65C.

Once the reaction is deemed finished, (there isn't really an indicator to look for, just when enough time has elapsed) strain/filter out any unreacted foil chunks. In this case, a large amount was left, probably about 8g, if dry. The foil in the strainer was rinsed with about 50mL dH2O which was added to the reaction contents in a 2L beaker.

The mixture was slowly basified by pouring the KOH solution into reaction contents, and was stirred on a stirrer for about 10 minutes. Some bubbling was observed as any remaining foil was reduced. The mixture was extracted with 1x 500mL, 1x 200mL fresh toluene by pouring the toluene into the beaker and continuing stirring. After separating the extractions were combined. The toluene started out clear, water-white, and after the extractions was slightly cloudy and slightly coloured.

The combined toluene extracts were washed with 3x 700mL dH2O, 1x 700mL brine (saturated NaCl). Most of the cloudiness cleared up after the washes. The toluene was dried in 40g dried MgSO4 for 10 minutes.

The toluene was then gassed, and filtered 4 times. Even though the crystals were as white as has been ever seen, the crystals were put into some boiling acetone and filtered again.

Total yield after acetone cleaning: 51.1g (92.4% w/w)

Anyone want some Nitromethane?


Temperature Readout
T+ (minutes) Temp (C)
0 24C
+ 10 58C
+ 15 71C
+ 20 72C
+ 30 70C
+ 40 69C
+ 50 68C
+ 85 64C (external heat added)
+ 105 66C
+ 115 67C
+ 175 56C (heat off)
+ 265 50C

Notes
[1] made by buffered performic, double distilled, measured a hair under 44mL, had light pale green tint... used up remaining amount, so it was a bit over what was called for
[2] made by chromic's method, as written up on the Hive
[3] properly nuggetized
[4] not enough NaOH (needed 200g) was available to basify the mixture, so enough 85% KOH flakes were used to compensate