Michiel C. A. van Vliet

Alumina: a cheap, active and selective catalyst forepoxidations with (aqueous) hydrogen peroxide

Chromatography alumina catalyses the epoxidation of alkenes with hydrogen peroxide under nearly anhydrous conditions. A variety of different aluminas show a similar catalytic behaviour. The hydrogen peroxide can be used as a preformed anhydrous solution in ethyl acetate, or it can be dried in situ by conducting the reaction under reflux with Dean–Stark water separation. The presence of a small amount of water in the reaction medium was shown to be of crucial importance.

Improvements in the Total Synthesis of Morphine

The chiral 1,2,3,4-tetrahydroisoquinoline intermediates in the Rice and Beyerman routes to morphine, (+)-(R)-1-(3-hydroxy-4-methoxybenzyl)-6-methoxy-1,2,3,4-tetrahydroisoquinoline (6) and (+)-(R)-1-(3,5-dibenzyloxy-4-methoxybenzyl)-6-methoxy-1,2,3,4-tetrahydroisoquinoline (5), were prepared in high ee by ruthenium-catalyzed asymmetric transfer hydrogenation of the corresponding imine precursors (Noyori method). The yield of the key raw material in the Beyerman route, 3,5-dibenzyloxy-4-methoxyphenylacetic acid (1), starting from gallic acid methyl ester (7) was improved by a factor of 5 over previously described syntheses. Key steps in the new procedure are the selective formation of methyl 3,5-dihydroxy-4-methoxybenzoate (9) via the 3,5-diacetate and an improved benzylation of the hydroxyl groups in 9.

Tertiary arsine oxides: active and selective catalysts for epoxidation with hydrogen peroxide

Abstract Tertiary arsines are active and selective catalysts for the epoxidation of a variety of alkenes with hydrogen peroxide at low catalyst loading (1–5 mol%); highly fluorinated analogues of these arsines can be recovered and reused with moderate efficiency.

Methyltrioxorhenium-catalysed epoxidation of alkenes in trifluoroethanol

The well known methyltrioxorhenium-catalysed epoxidation of alkenes with aqueous H2O2 is significantly improved by conducting the epoxidation in trifluoroethanol; excellent reaction rates and yields can be obtained for a variety of (terminal) alkenes with only 0.1 mol% of catalyst.

Perfluoroheptadecan-9-one: a selective and reusable catalyst for epoxidations with hydrogen peroxide

Perfluoroheptadecan-9-one is a selective and mild catalyst for the epoxidation of a wide variety of alkenes with hydrogen peroxide; after the reaction the catalyst can be easily recovered and reused without noticable decomposition.

Rhenium catalysed epoxidations with hydrogen peroxide: tertiary arsines as effective cocatalysts

Perrhenic acid in combination with tertiary arsines gives a versatile catalytic system for epoxidation of alkenes with hydrogen peroxide. The best results are obtained with diphenylmethylarsine. A wide range of alkenes could be epoxidised with aqueous hydrogen peroxide (60%) in 60–100% yields with substrate to catalyst ratios of up to 1000.