The article just recently posted at Rhodium, https://www.thevespiary.org/rhodium/Rhodium/chemistry/chloroephedrine.reduction.html
has been very useful.
Swig has been recently studying cuprates and coupling reactions, and realized a few weeks ago that higher order cuprates are and can be very efficient, and produce better yields compared to the low order cuprates or CuBr,and CuCN. Now after looking at this and seeing the poor yields using copper, I can't help to wonder if using higher order cuprates will produce higher yields compared to that of the stated copper compounds.
This confirms the role of the metal, and we may interpret the findings reported above by the assumption that the zinc donates two electrons to the polar C-Cl and C-N bonds of I, allowing the ions Cl- and CH3NH- to break away, and leaving the biradical PhC·HC·HCH3 behind which is propenylbenzene when the orbitals of the two odd electrons overlap to form a ð electron pair. Hydrogen, on the other hand, is not metallic enough to break the slightly polar C-N bond but it can break the C-Cl bond which in I - a substituted benzyl chloride - is very highly polar. Consequently a benzylic monoradical (IV) is formed, which quickly combines either with a hydrogen atom to form desoxyephedrine, or, to a lesser extent, with another radical IV to form II.
To test this hypothesis, I was reacted with copper, an element even less metallic than hydrogen. It might be reasonably expected to yield the monoradical IV which, in the absence of atomic hydrogen, can only dimerize.
The better success of higher order cuprates compared to low order cuprates might be the result of the electrons being sucked from the copper by it's neighbors, for example; CuBr*SMe2. It seems that one needs a metal that is neither to electropositive, nor not to electronegative. If this is true then one day expensive metals like palladium may not be needed if we can somehow influence a cheap metal like Copper to behave like Palladium by adding and removing the desired neighbors of the metal. This is just a little wishful thinking though. The d orbits seem to get really fucking complicated according to temperature, neighboring atoms, pressure and so on. I wonder if there is any data relating to the reduction of chloroephedrine using high order cuprates. Also, is there any data on the same subject concerning bromine?
A beginner of any given science becomes a master and expert of that science, when he/she realizes that they will be a beginner for the rest of their life.
