I've tried this synthesis and gotten yields ranging from 30% 45%. Sharing in case it might be helful to others. Vice versa, other people might know changes to this synthesis for higher yields.
Improvements are always welcome
Needed:
100 g 2-bromo-4-methylpropiophenone
500 ml DCM
200 ml Methylamine 40% aqua solution
60 ml HCI 30÷ aqua solution
550 ml Acetone
2 L Deminiralised water
PH measuring Strips
1 L IPA
Equipment:
Round bottom flask 2 L
Hotplate
Measuring cups 1 L
Crystallization dish
Vacuum pump
Buchner flask
1. Add 100 g 2-bromo-4-methylpropiophenone to 500 ml DCM and let it dissolve.
2. Add 200 ml methylamine in 4 portions
3. After 30 mins, put on hotplate and stir.
4. Temperature 32-36 C for 4 hours, or 40 C for 2 hours.
5. Rinse in measuring cup with demi-water until there is no methylamine smell left. Stir or shake after adding.
6. Add an ice cold solution of acetone/HCI 550ml/60ml, or add ice cold acetone and add HCI after.
7. Measure the PH, should be 6.
7. Put the 4-MMC freebase in freezer for 12h
8. Rinse with ice cold acetone trough buchner filter.
9. If you have obtained dry 4-MMC prepare a solution of 50/50 demi-water and IPA. Add 1g per 2-3 ml solvent. Boil until 4-MMC (Not longer than needed, aprox. 1-3 min.). Pour into a crystallization dish. When crystallization stops at room temperature, put the dish in the fridge. Put in freezer after and you will be left with nice looking crystals.