05-03-04 23:08
No 504730
Well, here it is. A wild stab in the dark, born of sleepless nights and way too much hive reading. If it works, GHB can be put on the "uncontrollable" list.
Basically, the idea is simple.
I: Ethylene glycol is placed in a vessel with NaOAc and NaCl and H2SO4 is added to yield chloroethylacetate (ClEtOAc, ClCH2CH2OCOCH3) by reaction ( (CH2OH)2 --> (CH2OAc)2 --> ClCH2CH2OAc) (refs and details provided later).
Alternately, ethylene chlorohydrin and acetic acid can be esterified quantitatively in the presence of catalytic tosic acid. Sulfuric acid would likely also work.
II: chloroethyl acetate is cyclized by PTC under not-very-hydrous conditions (i.e. Na2CO3 solid phase?) to GBL.
Molecule: cyclization ("ClCOC(=O)C>>C1COC(=O)C1")
No refs on this one exactly as stated. Several cyclizations, done with K.OtBu, NaH, or NaNH2 (the most common ones) into 5 and 6 membered rings, and the promise that PTCs can deprotonate very basic substrates. This one should be very close to the limit, but still doable. The fact that it's an intramolecular substitution makes it much faster.
The real challenge is to prevent hydrolysis of the ester before cyclization can take place. This will no doubt require careful reaction design, and the first bee to pull it off will recieve unending accolades, not to mention a never ending supply of GHB
.I really hope someone could try this.
Probably oxidation of THF is more practical, at least for the time being.
I've been chased by both cops and robbers. So what does that make me?
(Chief Bee)
05-04-04 09:29
No 504802
Unfortunately the chloroethyl acetate will likely cyclize to oxirane instead, as the following references says will happen in a basic environment:
Patent US2022182 (heating with aqueous NaOH)
Ann. Chem. 113, 121 (1860) (heating with potassium carbonate)
Heating in the absence of base, ethene or chloroethene will form instead. I could find no lactone-forming reactions in beilstein.
The Hive - Clandestine Chemists Without Borders
(acetaminophanatic)
05-04-04 22:29
No 504955
That patent uses an aqueous solution of hydroxide, which surely hydrolyzes the rather delicate ester.
This reaction must be performed in anhydrous conditions, with a non-nucleophilic base. Hydroxide is not very good for this.
"synthesis of cyclopropylamine with phase transfer catalysis" is very promising. They perform an intramolecular PTC Claisen condensation (Finally!) of isopropyl gamma-isopropoxybutyrate (derived from GBL
) to give isopropyl cyclopropanecarboxylate, which is then converted to the amide and hofmann rearranged to give cyclopropylamine. (should make a fun PCP derivative....)This is cool also because it has bearing on the tryptamine idea....
Unfortunately, it's also inaccessible. Journal of Central South University of Technology (English Edition) 2000, 7(2), 81-83. {this is a chinese university}
So, they are doing something similar. Actually, I have several papers where people alkylate esters, just not intramolecularly. And a few papers where they perform intramolecular ring closures, just not on esters. So why wouldn't this ring closing work, as long as water is carefully kept out?
I've been chased by both cops and robbers. So what does that make me?
(Chief Bee)
05-05-04 04:09
No 504997
under not-very-hydrous conditions (i.e. Na2CO3 solid phase?)
You suggested this, and that is what is used in the Ann. Chem. article I referenced, and the author arrived at oxirane.
It looks like carbonate (even without a PTC) is able to deprotonate the 2-chloroethyl chain, and thereby causing an irreversible elimination/rearrangement to oxirane. The problem with the ester deprotonation/cyclization is probably because it is reversible, and therefore any deprotonation may just as well be followed by a re-protonation (maybe the ester enolate is the species which actually grabs a proton from the chloroethyl chain?).
The Hive - Clandestine Chemists Without Borders