Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
 Pages:  1  2
Author: Subject: Metal/acid reduction of benzoin
Newton2.0
Hazard to Self
**




Posts: 63
Registered: 12-8-2019
Member Is Offline


[*] posted on 19-2-2021 at 14:41


karlosĀ³! I am enamored with this! I tried both methods and I have found that Zn in AcOH is the most efficient method, at least for me.

Tin/HCl Reduction of Benzoin:

-53g benzoin
-53g Sn powder which was obtained by using a bandsaw to make the powder and using a sieve to try and obtain the finest particles (These were on average likely larger than 100 mesh, however, there were some fine particulates which were in the 100-200 mesh range)
65mL EtOH (absolute)
65mL 32% HCl

Refluxed this mixture for approximately 35 hours and additional portions of Sn powder totalling 15g were added to compensate for the large particle size of the Sn.

A slightly oily, yellowish material is present and it appears the reduction is taking place.



In a separate run, I have tried the GAA/Zn mix and have found it far superior in both reaction time and simplicity. I ran the reaction similarly to SC, refluxing for approximately an hour.

Zinc/GAA Reduction of Benzoin
-29g benzoin
-40g GAA
-6.6g Sn (325 mesh) activated by immersion in 3-5% HCl and swirled around and then decanted and washed with dH2O.

An oily, yellowish precipitate was noted and upon pouring the mixture into a beaker of warm dH2O, a mass of chunky, off-white solid was formed. This will be collected and recrystallized in boiling EtOH at which point the solids will be dried and weighed and a melt test will be performed.



I'm excited to follow up with this method! I have seen others discussing additional reactions involving tosylates, etc. in an attempt to improve amination yields. I think this is a really promising avenue of discovery for the amateur chemist!


I wonder if piperidine can be used in place of DMA ala Chemplayer's piperidine ephedrone synthesis. And I will look into the effects of various N-, and N, N-substitutions.
View user's profile View All Posts By User
mr_bovinejony
Hazard to Others
***




Posts: 130
Registered: 20-4-2018
Member Is Offline

Mood: ASS

[*] posted on 19-2-2021 at 15:53


I've found that adding the metal in increments helps a lot during reduction. I'm excited that someone else is trying this! I have deoxybenzoin oxime sitting around still but I think I'm going to try again with nabh4 and molecular seives first when I get back to this project
View user's profile View All Posts By User
Newton2.0
Hazard to Self
**




Posts: 63
Registered: 12-8-2019
Member Is Offline


[*] posted on 20-2-2021 at 09:21


I haven't gotten to the point of the reductive amination yet.

I do somewhat wonder about the presence of Sn and Zn in the deoxybenzoin. Hopefully, recrystallization will separate this out. I have to do a few more of these because it seems pretty dirty still.

I have found a very interesting bit of information for the reductive amination step. Probably common knowledge to most of you but here it is:

https://www.organic-chemistry.org/abstracts/literature/363.s...
View user's profile View All Posts By User
karlosĀ³
International Hazard
*****




Posts: 1520
Registered: 10-1-2011
Location: yes!
Member Is Offline

Mood: oxazolidinic 8)

[*] posted on 20-2-2021 at 11:42


As for the enamine/imine formation, you want to do that separately before over molsieves or under dean-stark conditions(for higher boiling amines like piperidine).
Lower boiling amines like ethylamine and dimethylamine require to be left in, for example DCM, over molsieves for a week or the like, then the organic solvent is removed and the enamine/imine used as it is in alcohol.
This is the key to achieve a moderate yield, it is a bit discussed over at HL with references.

We haven't done this though, none of us, at least yet.
View user's profile View All Posts By User
Newton2.0
Hazard to Self
**




Posts: 63
Registered: 12-8-2019
Member Is Offline


[*] posted on 13-4-2021 at 10:13


So, I decided to run the Zn/GAA reduction again but I did not properly activate the Zn grains. As a result, the amount of Zn at the bottom of the flask seems to be unchanged after a few hours.

As this is the last of my benzoin, I must salvage the reaction. I added a small amount (approximately 2mL) of 32% HCl dropwise in hopes of etching the Zn enough to activate it. Hopefully, this plan works and doesn't screw the whole thing up.

View user's profile View All Posts By User
 Pages:  1  2

  Go To Top