An
efficient gold-catalyzed cyclization of 2-alkynylaldehyde cyclic acetals
has been developed for the synthesis of indenone derivatives. A wide
variety of functionalized indenone derivatives can be obtained in
good-to-excellent yields. HMBC and NOESY NMR analyses and mechanistic
elucidation experiments revealed that the cyclization occurs via a
1,5-H shift. The cyclic acetal group promoted the 1,5-H shift by activating
the benzylic C–H bond and preventing the migration of the alkoxy
group by tethering both alkoxy groups.
The platinum on carbon (Pt/C)-catalyzed deuteration of acrylic and methacrylic acid derivatives in deuterium oxide (D 2 O) efficiently proceeded to give the corresponding acrylic acid-d 3 and methacrylic acid-d 5 derivatives. The olefinic functionality, as well as the methyl group on the unsaturated functionality of the substrate, were satisfactorily deuterated via the hydrogen (H)deuterium (D) exchange reaction. The obtained deuterated compounds are useful building blocks and efficiently converted to the corresponding desired products including a polymer without the degradation of the original deuterium contents.
Deuterium-labeled compounds are widely utilized in various scientific fields. We summarize the recent advances in the direct deuteration of sugar, saturated fatty acid, and arene derivatives using heterogeneous platinum group metal on carbon catalysts by our research group. Hydrogen gas is a key catalyst-activator to facilitate the present H-D exchange reactions. In this review, the direct activation method of catalysts using in situ-generated hydrogen based on the dehydrogenation of alcohols is introduced. The obtained multiple deuterium-labeled products, including bioactive compounds, are expected to contribute to the development of many scientific investigations.
The polyethyleneimine-modified
polymers, polystyrene–divinylbenzene-based
(TAs) and polymethacrylate-based polymers (TAm), were used as palladium
scavengers to eliminate residual palladium species after palladium
on carbon-catalyzed Sonogashira-type coupling reaction. Since both
TAs and TAm indicated relatively favorable elimination abilities toward
residual palladium species in the reaction mixture, the affinities
of TAs and TAm for palladium species were used as supports for palladium
catalysts. The TAm-supported palladium catalyst (Pd/TAm) indicated
better catalyst properties for the chemoselective hydrogenation compared
to those of the corresponding TAs-supported palladium catalyst (Pd/TAs).
Aromatic benzyl ethers; aromatic and aliphatic
N
-Cbzs;
and aromatic carbonyl groups were smoothly hydrogenated in the presence
of 1–5 mol % of Pd/TAm in MeOH or 2-PrOH. In contrast, the
hydrogenation of aromatic ketones was selectively suppressed in morpholine
which act as appropriate catalyst poison and solvent. Furthermore,
Pd/TAm-catalyzed chemoselective hydrogenation was applicable to continuous-flow
reaction.
We have established am ild and direct platinum on carbon (Pt/C)-catalyzed multi-deuterium labeling of various saturated fatty acids including bioactive compounds with high deuterium efficiencies in am ixeds olvent of isopropyla lcohol and deuterium oxide (i-PrOH)/D 2 Ou nder neutral conditions at 120 8 8Cw ithout the external addition of deuterium or hydrogengas.
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