From: Jack Sullivan (jsulliva$##$eclipse.net)
Date: Thu May 13 1999 - 12:47:20 EDT
I'm interested in getting some direction on references or experience in
hydroborating 1,2-disubstituted alkynes with reagents such as 9-BBN or
catecholborane in order to produce vinyl boronic acids. For discussion,
the substiturent on C-1 would be an aryl group while that on C-2 could
be either alkyl or aryl.
I assume from the references that I have that the addition would prefer
the least hindered carbon atom of the alkyne. With C-2 being alkyl I
would imagine this would yield predominantly C-2 addition. If both
substituents are aryl, I would also assume that a mixture of C-1 & C-2
boronic acids would result & that these should be separable by either
crystallization or chromatography.
As a final point, I would also presume that the resulting vinyl boronic
acids would have the more stable trans configuration.
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