Okie dokie, here's how it is.
Reductive Amination:
Well the "reductive" bit refers to reducing. Reducing is
synonymous with "hydrogenation". Let's say you have a
compound like the following:
# double bond
/ - \ single bond
O oxygen atom
C carbon atom
H hydrogen atom
O
#
H C H
\ / \ /
H-C C-H
| |
H-C C-H
/ \ / \
H C H
/ \
H H
Pardon the ascii art. This is cyclohexanone (keto form).
If we REDUCE this (HYDROGENATION) using catalytic
hydrogenation (that just means reducing with hydrogen and
a catalyst - something that speeds up the reaction, but
doesn't become part of the reaction products), we
will get:
OH
|
H C H
\ / \ /
H-C C-H
| |
H-C C-H
/ \ / \
H C H
/ \
H H
cyclohexanol.
Can you see how the hydrogen has "attached" itself to the
oxygen atom, by breaking one of the bonds that it had with
the carbon atom? If we continue to reduce we get:
H H
\ /
H C H
\ / \ / H
H-C C-H /
| | + O
H-C C-H \
/ \ / \ H
H C H
/ \
H H
cyclohexane
Can you see how further reducing(hydrogenation) has fully
removed the Oxygen atom from the compound? Now it has
bonded with another hydrogen atom, and no-longer has a
bond to the carbon atom, so it drops off as water (H2O).
Now the carbon is 2 bonds too short, and bonds with 2 more
hydrogens to "fill itself up".
This is how reducing works. If you look at ephedrine, you'll
see that it has an alpha-hydroxy group (another name for
an OH). If you reduce ephedrine, this O bonds with another
H atom and drops off as H2O. Then more H's come along to
"fill up the space", and we get methamphetamine (a powerful
and dangerous stimulant, a controlled substance in many
countries).
So now you know what REDUCING is. But you want to know what
reductive amination means?
Well, to AMINATE something refers to reacting a compound
with ammonia (NH3), or an ammonia-containing compound, such
as methylamine (NH2CH3) to produce an imine (never mind
what that means). Reductive amination is the action of:
1. reacting a compound with an ammonia-containing compound.
2. reducing the formed imine
Thus, when we reductively aminate safrole, we add NH2CH3,
and then we hydrogenate it (reduce it), to give us
3,4-methylenedioxymethamphetamine (pay honey).
If we're making honey from bromosafrole, we don't need to
reduce it, we just aminate it with ammonia (NH3). This is
why the bromosafrole method is popular with some people, as
it can be sealed up inside a container and sat for several
days (until it finished aminating), or put into a pipe-bomb
and heated to 130'C in hot oil for 2 hours (this aminates
faster).
In turning L-PAC into l-ephedrine, one could aminate with
methylamine in the pipe-bomb, and then reduce it with
sodium borohydride (NaBH4), or aluminum amalgam (Al/Hg),
catalytic hydrogenation with raney nickel, or possibly
even with an urushibara catalyst such as created from
nickel chloride (NiCl2) and aluminum. Many other ways
exist to reduce this formed imine. If one had the glassware,
the pipe-bomb would be replaced with a reflux condenser
and a round-bottomed flask, and the mixture of methylamine
in methanol and the L-PAC would be refluxed for the
necessary amount of time.
Many reductive aminations reduce and aminate at the same
time, such as the popular Al/Hg method (not actually the
Al/Hg method, but an extension a bee has made to it that
aminates and reduces at the same time).
So I hope that explains reductive amination. For more info,
visit Rhodium's site at
https://www.rhodium.ws
and look at some of the info on different methods (of
interest to you might be the bromosafrole/halosafrole route
that uses the pipe-bomb for aminating. However, this
reaction aminates with ammonia, not methylamine as is
required for reductively aminating L-PAC).
Hope I could sort some things out for you.
And now I need a big dump (darned coffee).
Sphincterally yours,
Encopo.
Don't mind me. I'm mentally ill.