Reactivity versus Stability of Oxiranes under Palladium‐Catalyzed Reductive Conditions

Abstract

This review highlights the different selectivities and efficiencies of the Pd‐catalyzed reductive procedures that have been applied to substrates containing an epoxide ring. The proposed mechanisms are also described with, in some cases, personal comments. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Studies directed toward the exploitation of vicinal diols in the synthesis of (+)-nebivolol intermediates

“…However, it has been reviewed that not only benzylic epoxides but also non-benzylic epoxides are sensitive to the standard hydrogenation/debenzylation conditions [35]. Whereas benzylic epoxides are highly sensitive to hydrogenation conditions, non-benzylic epoxides, depending on the reaction conditions, may produce traces to significant amounts of side-products via hydrogenolysis.…”

High‐Efficiency and Room‐Temperature Reduction of Graphene Oxide: A Facile Green Approach Towards Flexible Graphene Films

“…The FT‐IR spectra of RGO‐L samples obtained with different H‐CR times demonstrate that the oxygen‐containing functional groups in GO, such as COOH (1720 cm −1 ), C–O (1050 cm −1 ), and C–O–C (983 cm −1 ), disappear and the graphene skeleton (1570 cm −1 ) and C–OH (shift from 1230 to 1200 cm −1 ) are formed gradually along with the increase of reaction time (Figure 1a) 28–30. The C–O–C groups in GO are susceptible to reduction into C–OH groups via catalytic hydrogenation,31 while the H‐CR of COOH groups does not easily occur at low temperatures even under high‐pressured hydrogen 32. Accordingly, the diminished FT‐IR signal (1720 cm −1 ) during H‐CR of GO may be attributed to the removal rather than reduction of COOH groups 32…”

Selective palladium nanoparticles-catalyzed hydrogenolysis of industrially targeted epoxides in water

“…Catalytic reductive opening of epoxides by heterogenized Pd species constitutes a strategic way to selectively produce alcohols but its mechanism still remains unclear. The formation of PdH species is usually admitted through the dissociative adsorption of H 2 on the active surface sites of Pd NPs [2,40].…”

“…The reductive ring-opening of oxiranes constitutes a paramount organic transformation [1,2], giving access to alcohols as relevant synthons for fine chemistry and fragrance industry.…”

“…In that context, molecular complexes have been designed to control the opening of epoxides to selectively provide either the primary [7,8] or the secondary [9,10] alcohol. Heterogeneous catalysts have also been used, such as modified Raney nickel at the early stage as well as palladium on charcoal with a higher occurrence [2,11,12], with good results for the reduction of terminal epoxides, but substrate-dependent selectivity [13]. Recently, nanocatalysts proved to be pertinent tools, affording relevant catalytic performances owing to their unique surface reactivity [14,15].…”