Investigations into theC-deuteriation of silyl enol ethers derived from aryl alkyl ketones

Abstract

SummaryResults are reported on the regioselective C-deuteriation of a series of silyl enol ethers derived from aryl alkyl ketones using deuterium (D 2 ) gas as the deuterium source and palladium-on-barium sulfate as the mediator. These results highlight the numerous reaction pathways and different product types available from simple deuteriation of substituted enol precursors.

Recent Advances in the Synthesis of Deuterium‐Labeled Compounds

“…On one hand, the positions and levels of deuterium incorporation are highly dependent on the structure of the functional group connected with the aromatic ring. For example, deuterium incorporation into the indenyl skeleton is higher than that into larger tetralenyl and benzocycloheptenyl homologs [87] . On the other hand, the electronic nature of functional groups contained in the aromatics also affects the replacement position and amount of deuterium atoms because the activation energies of different positions for the H−D exchange are quite different [88] .…”

“…For example, deuterium incorporation into the indenyl skeleton is higher than that into larger tetralenyl and benzocycloheptenyl homologs. [87] On the other hand, the electronic nature of functional groups contained in the aromatics also affects the replacement position and amount of deuterium atoms because the activation energies of different positions for the HÀ D exchange are quite different. [88] Branch et al studied the kinetics of the Hg(C 6 H 5 Me) 2 (GaCl 4 ) 2 catalyzed HÀ D exchange of naphthalene with C 6 D 6 .…”

Preparation of α‐labeled aldehydes by base‐catalyzed exchange reactions

“…Acid‐ or base‐catalyzed exchange of a proton in a carbonyl function by using D 2 O or diluted tritium oxide in water could meet these requirements of simplicity and compatibility with small scale 5. However, α‐labeling of aldehydes is challenging due to the tendency of most such compounds to self‐condense under acidic or basic conditions.…”

“…Even if the extent of such aldol reactions was only moderate, purification of the crude, usually by distillation, would be necessary 6. For this reason, the reported protocols of exchange of a proton are not suitable for small amounts α‐labeled aldehydes 5. Thus, we studied the deuteration of nonanal, as a representative example of an enolizable aldehyde, with D 2 O under various conditions and catalysts.…”