ORGLIST: dehydrochlorination

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From: M7419$##$aol.com
Date: Mon Feb 02 1998 - 16:46:04 EST


I am trying to synthesize 3-chlorocyclobutane carboxylic acid to
dehydrochlorinate to 2-cyclobutenecarboxylic acid. I synthesised
cyclobutanedicarboxylic acid using the procedure of Heisig and Stodola (Org
Syntheses, vol 4). Following the procedure of Nevel, Frank and Trepka (JOC,
27, 428, 1961(or 2)) I attempted to chlorinate it at the 3 position with
sulfuryl chloride and benzoyl peroxide as an initiator. When I fractionated
the black residue after the decarboxylation step the temperature never rose to
the value given in the reference (113-125^C/10mm). The highest it went was
94^C/10mm and in the recieving flask there were two layers which I didn't
bother to collect seperately since the temp was too low and the oil bath I was
using to heat the flask had reached its temp limit. One of the grad students
in the lab said the bottom layer was most likely my product. There was only a
few drops of liquid which I discarded along with the black residue. I now
kinda have a feeling the liquid was my product.

Now to get to my question. I have a feeling I am going to have to start over
and a few days ago I accidently ran across a procedure to make
cyclobutanecarboxylic acid (J. Chem. Soc. Perkin Trans I 1993) from the same
starting materials as the procedure from Org Syntheses (1,3-dibromopropane and
diethyl malonate) but instead of using sodium ethoxide as the base and heating
the mixture they used a 50% NaOH solution and an alkylammonium chloride phase
transfer catalyst at room temperature to go directly to cyclobutanecarboxylic
acid. This seemed much easier and faster (albeit less fun not being able to
play with the metallic sodium) way to get to the acid I want. The reference I
have gives a procedure to chlorinate the mono acid (which is simpler and
faster than the one for the diacid) but it gives a mixture of the 2- and 3-
chlorinated acids. My question is (finally) if I dehydorchlorinate the
2-chlorocyclobutanecarboxylic acid will the proton on the #1 carbon be removed
to form 1-cyclobutenecarboxylic acid or will it still form the product I want
2-cyclobutenecarboxylic acid. 3-chlorocyclobutanecarboxylic acid is the major
isomer formed but it would be nice if I could skip the step to seperate the
isomers before I dehydrochlorinate the acid.

Thanks a bunch for any help (and for having the patience to read through all
this).

Michael Lynch
lync0106$##$tc.umn.edu
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