methylammonium formate leuckart - help needed

[armageddon]

I didn't manage to find a good writeup for a simple Leuckart using methylammonium formate here at the hive, so I started this thread...

This is from "Gattermann, Ludwig: Die Praxis des organischen Chemikers", so sorry for the bad english...  

alpha-Phenethylamine

A 500ml two-ecked flask is fitted with a claisen, downward condenser and a thermometer reaching into the rxn mixture. 125g ammonium formate are introduced and heat is apllied (using an oil bath) until the solids liquifies, boils and the temp. reaches 165°C. The watery-ammoniacal distillate is being discarded. Bath temp. is allowed to drop to 130°C. At this point, the dist. setup is removed and 60g freshly distilled acetophenone (0.5 mol) are added. A 30cm long unpacked column (or air-condenser) is fitted between flask and claisen/condenser and bath temp. is raised to 175°C over 1 hour (water distills over and ammonium carbonate appears on top of column). After heating for 4 hours at 170-180°C, homogenization occurs and rxn is finished.

After cooling, the rxn mixture is poured into a sep. funnel and excess amm.formate and formamide are removed by shaking 2x with 60ml water, which in turn is re-extracted with 30ml benzene. The crude product and benzene xtract are put back into the flask and 60ml concentrated HCl are added. The benzene is removed by distillation, then the dist.setup is changend with a reflux condenser and hydrolysis of the formyl derivative is allowed for 45 minutes at reflux.

The cooled, acidic solution is washed 2x with 25ml benzene, after which it is basified in a 1l flask using 75g NaOH dissolved in 250ml ice water (the phenethylamine separates forming a top layer). The free base is then steam distilled (heating the flask too, keeping volume constant). After 600ml distillate have been collected, it is extracted with 50ml benzene, followed by 4x extraction with 25ml benzene. The combined benzene solutions are dried over KOH pellets. After the removal of benzene, alpha-phenethylamine distills over at 74-76°C/15torr. The yield is 45-48g alpha-phenethylamine as a colorless oil (74-79% of theory).





OK this is only phenethylamine - but I think it's a good point to start a new Leuckart discourse..  

Although I would rather use a dean-stark instead of distillation setup: the idea of removing excess formic/formate/formamide before hydrolyzing sounds good - probably less tar to bother with!? (same thing with steam distilling the free base, but that's rather old coffee..)

my questions: what happens if alkyl-substituted formate is used? (proposed temp., heating time etc.) and what about using different P2Ps instead of acetophenone? Yields will decrease I would guess? Difficulties to be expected?

Post 302161 (missing)

(Antoncho: "Leuckart with 92%+ overall yield", Methods Discourse)unfortunately contains very little info about CH3NH3COOH..

(terbium?)

Greetz A

[Methlaab]

When i looked to SWIM's source and compare it with yours I could see that SWIM would use only 100 Grams of ammonium formate and 0.5 moles of substituated P-2-P to put it with some boiling stones in a boiling flask (maby porcelain to prevent bumping). Then SWIM would heat the mixture on a small flame. The content will melt and form two layers. The mixture begins to distill at 140°C. The mixture becomes homogeneous between 150 to 160°C. The heating is stopped when the temperature reaches 185°C.
     The distillate forms two layers. The water insoluble layer is the top layer and contains the substituted phenyl-2-propanone. The upper layer of the distillate is separated from the bottom aqueous layer and is poured back into the boiling flask.
     The solution is refluxed for two more hours until the tempferature reaches 185 degrees. The solution is then extracted with an appropriate solvent and evaporated to leave the 1-phenyl-2-(formylamino)propane.
     Formamide can be recycled from the aqueous layrt of the distillate by distilling to 165°C. The formamide can be purified by crystallization or fractional distillation. This is unnecessary as long as the recovered formamide is going to be used with the same ketone in future reactions...

Refernce:
         (Ingersol 1936)
         (Heinzelman 1953)
         (Alles 1935)
         (Dal Cason 1990), (Elks 1943)
         (Bobranskii 1941)