There's a certain reaction I've been doing that involves DBU (I've drawn the structure out below). The reaction is done in a flow machine (ie. high temperature and high pressure). enter image description here I've read that chloroform can't be used as a solvent for this reaction, because under the flow machine conditions DBU reacts with chloroform to form a side product. I was interested in what this reaction is, so I've had a bit of a look but can't work it out. Here's what I'm thinking so far:

  1. I've read that chloroform can react with base to form dichlorocarbene. There's no strong base here in this reaction, but could the high temperature/pressure conditions be causing this species to form? Dichlorocarbene could then react with DBU.
  2. The only alternative I can think of is that chloroform does a nucleophilic substitution (with the DBU acting as electrophile)? Under normal conditions chloroform doesn't do nucleophilic substitution, but maybe under high temperature/pressure conditions it can. Also, DBU could potentially act as an electrophile in different ways: enter image description here Or alternatively, the enamine tautomer could potentially be the nucleophile: enter image description here Thanks for any help!

1 Answer 1


DBU is stronger base than you think. Strong enough to generate dichlorocarbene from chloroform under flow conditions as this reference shows here.


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