This seems like a good method, I am surprised no one has give it a shot - any comments?
ith acetaldehyde diethyl acetal, just heating together with ethyl N-methyl carbamate should be enough to produce ethyl N-alpha-ethoxyethyl N-methyl
carbamate.
Alternately, the procedure of japanese patent JP8268991 is followed with ethyl N-methyl carbamate, acetaldehyde, and ethanol in acidic solution. (90%
yield quoted)
This material is dried, the alcohol evaporated and the product dissolved in ether and dried over mol. sieves (necessary?)
The organometallic reaction is following the vague directions of Tet. Let. 1989, 5611 "The alkylation of a-ethoxycarbamates with organo-lead, -zinc,
and -copper reagents. High Cram selectivity and formal nonbasic alkylation of imines"
Benzyl chloride is dissolved in ether or THF and dry zinc powder added with stirring. Extra ZnCl2, FeCl2, or AlCl3 could be added here.
The solution is cooled (in the paper to -78 C, but is that really necessary?), the alpha-ethoxy carbamate added slowly, and the solution allowed to
rise to 0 C or RT (depends?), then quenched with NaHCO3 solution. {I would use HCl...}
Expected yield: ~70 - 88%
The amine is deprotected by stirring the crude product with 1 M HCl solution, the solution filtered and the amine salt purified by A/B extraction and
gassed to a salt.
This seems like a good method, I am surprised no one has give it a shot - any comments?
You're surprised
that nobody wants to use organolead compounds?zephler1 - 20-11-2013 at 21:17
ZnCl2 can bee used....Zephyr - 3-12-2013 at 22:39
Could you provide links to the corresponding patents?
I would be interested in taking a look at them.
The lack of references/attempts on this procedure may be a result of the hard to get reagents.
