Does the dieckmann condensation occur in the gas phase?

Burinsky and Cooks 1 have reported that deprotonated dimethyl adipate eliminates methanol via a gas‐phase Dieckmann condensation. This is in contrast to the behaviour of simple methyl ester enolates which lose MeOH by a different mechanism, e.g. MeOCOC̄HCH 2 R → [Me O (OCCHCH 2 R)] → OCCHC̄HR + MeOH. Evidence is presented which supports the Dieckmann mechanism for adipates. For example, MeOCOC̄(Me)CH 2 CH 2 CD(Me)CO 2 Me should eliminate MeOD in a Dieckmann condensation, but MeOH by the alternative mechanism outlined above. Experimentally, MeOD is lost exclusively. Similarly, MeOCOC̄DCH 2 CH 2 C(Me) 2 CO 2 Me also loses MeOD, consistent with a Dieckmann process.