Post 439898 (https://www.thevespiary.org/talk/index.php?topic=11190.msg43989800#msg43989800)
(LaBTop: "No. Wrong.", Newbee Forum)it stated ethanol and DMF are having good solubility of NaBH4. Has any bee tried out using ethanol or DMF as solvent?Post 439864 (https://www.thevespiary.org/talk/index.php?topic=11190.msg43986400#msg43986400)
(Vibrating_Lights: "Imine reduction", Newbee Forum)Ethanol has got reasonable NaBH4 solubility, 4g/100g. At room temperature. SWIM also reads in some thread that ethanol can hold 33% wt of methylamine.Disadvantages of using methanol/water/polar aprotic solvents as solvent in sodium borohydride reduction:
Sodium borohydride reductions are usually conducted in methanol as solvent due to its high solubility in methanol.
Other popular solvents for reductions using sodium borohydride as reducing agent are water and polar aprotic solvents such as DMF etc.
Following disadvantages are encountered when these solvents are employed :
1. Reacts vigorously with lower aliphatic alcohol such as methanol and ethanol at room temperature liberating 4 moles of hydrogen.
2. Promotes side reactions such as ketals, acetals, hydrates, etc.
3. Protonolysis takes place in aqueous solution, rate increasing rapidly with increasing temperature and decreasing pH.
4. Organic molecules to be reduced are not soluble in water.
5. Sodium borohydride exhibits useful solubility in diglyme and DMF and could be used for the reduction but these solvents due to water miscibility and high boiling points make work-up of the reaction quite inconvenient, further ketones react very slowly in diglyme.
To overcome the above mentioned problems such reduction reactions are conducted in two phase system using non-polar aprotic solvents such as benzene, toluene, dichloromethane, diethyl ether and tetrahydrofuran (THF) using phase transfer catalyst.
It mentions DCM, DMF, toluene, ether are among the solvents that could be used in NaBH4 reduction.(with or without PTC). There so many possibilities.
Post 531792 (https://www.thevespiary.org/talk/index.php?topic=10127.msg53179200#msg53179200)
(XrLeap: "Easy NaBH4 amination", Newbee Forum)Post 503533 (https://www.thevespiary.org/talk/index.php?topic=9774.msg50353300#msg50353300)
(Bandil: "Pseudo-"wet"- BH4 amination BH4", Methods Discourse)It stated 80%+ of yield is achievable. However, SWIM used Barium's method to generate methylamine gas in situ, whereas Bandil used 40% aq methylamine solution. The IPA as solvent method is quite sentive to the parameters, and end yield will be affected badly. Side note, when water is very salty, it forms 2 layers with IPA. Most of the low yield was more or less due to SWIM's sloppy nature, that is also why SWIM is not generating methylamine gas to "pump" them into methanol.