Polystyrene-Supported (Catecholato)oxorhenium Complexes: Catalysts for Alcohol Oxidation with DMSO and for Deoxygenation of Epoxides to Alkenes with Triphenylphosphine

Abstract

Dedicated to Professor Dieter Seebach on the occasion of his 65th birthday Polymer-supported catalysts offer practical advantages for organic synthesis, such as improved product isolation, ease of catalyst recycling, and compatibility with parallel solution-phase techniques. We have developed the (carboxypolystyrene-catecholato)rhenium catalyst 2 derived from tyramine ( 4-(2-aminoethyl)phenol), which is effective for alcohol oxidation with dimethylsulfoxide (DMSO) and for epoxide deoxygenation with triphenylphosphine. The supported [Re(catecholato)]catalyst 2 is air-and moisture-stable and can be recovered and used repeatedly without decreasing activity. The procedures work with nonhalogenated solvents (toluene). DMSO for Re-catalyzed alcohol oxidation is inexpensive and safer for transport and storage than commonly used peroxide reagents. The oxidation procedure was best suited for aliphatic alcohols, and the mild conditions were compatible with unprotected functional groups, such as those of alkenes, phenols, nitro compounds, and ketones (see Tables 1 and 2). Selective oxidation of secondary alcohols in the presence of primary alcohols was possible, and with longer reaction time, primary alcohols were converted to aldehydes without overoxidation. Epoxides (oxirans) were catalytically deoxygenated to alkenes with this catalyst and Ph 3 P (see Table 3). Alkyloxiranes were converted to the alkenes with retention of configuration, while partial isomerization was observed in the deoxygenation of cis-stilbene oxide ( cis-1,2-diphenyloxirane).These studies indicate that supported [Re(catecholato)] complexes are effective catalysts for O-atom-transfer reactions, and are well suited for applications in organic synthesis.

Supported Gold and Silver Nanoparticles for Catalytic Deoxygenation of Epoxides into Alkenes

“…In addition, most of these methods require special handling and harsh reaction conditions, which may affect other sensitive functional groups in the parent molecules. Several successful catalyst systems have appeared to date such as Re complexes with triphenylphosphine,15–17 a Fe complex with NaBH 4 ,18 and a Co complex with Na,19 but these systems suffer from the need for hazardous reductants, inert conditions, and display low catalytic activities (TOFs <13 h −1 , TONs<20; TOF=turnover frequency, TON=turnover number), and low atom efficiencies. Therefore, the development of an efficient catalytic system for deoxygenation of epoxides remains of great importance.…”

Technetium & Rhenium: Inorganic & Coordination Chemistry

“…(33) and (34) reductions to alkenes with PPh 3 , following the proposed mechanism of Scheme 4. 105 The use of technetium compounds in catalysis is a much less studied field. An example, investigated kinetically, is the oxidation of hydrazine (to NH 4 + , N 2 and other nitrogeneous products) by oxo-anions (nitrate or perchlorate) catalyzed by pertechnetate in aqueous acidic medium, which was proved to proceed via a chain process.…”

Catalytic Oxidative Processes in Steroid Chemistry: Allylic Oxidation, &#946;-Selective Epoxidation, Alcohol Oxidation and Remote Functionalization Reactions

“…The same reaction has also been performed with [160], with pyridinium dichromate-Me 3 SiO OSiMe 3 system [161] and with DMSO catalyzed by a (polystyrene-catecholato)oxorhenium complex (Fig. 13) [162]. In the latter case, the supported [Re(catecholato)] catalyst could be recovered and used repeatedly without loss of activity.…”

“…-Estradiol 76 was oxidized to the 17-keto derivative 77 by DMSO and (polystyrene-catecholato) oxorhenium complex as catalyst (Fig. 13, scheme 20) [162]. N-tert-Butylbenzenesulfenamide catalyzed the oxidation of 17 -hydroxy-5 -androstan-3-one 75 to the corresponding 17-ketone 55 (scheme 19) using N-chlorosuccinimide in the presence of K 2 CO 3 and MS 4Å [165].…”