Chemical Synthesis

Os EnCat 40


Os EnCatTM 40
Microencapsulated OsO4


Sigma-Aldrich is pleased to offer innovative catalysts for use in practical synthetic transformations in collaboration with Reaxa. Reaxa has immobilized osmium tetroxide, a toxic and volatile reagent, via encapsulation in a polyurea matrix to create Os EnCatTM 40 catalyst (cf. pictures below). This innovative product offers safety and handling advantages versus conventional OsO4, while acting as an alternative reagent in the industrially useful dihydroxylation reaction paradigm.

Product Ordering Information
Os EnCat™40, 0.3 mmol/g Os loading: 658685

Optical Image
of Os EnCatTM40 Beads

Os EnCatTM40 and OsO4 visual after
2 months storage



Advantages of Os EnCat™ 40 Catalyst:


· Safer, easier to handle, and non-volatile
· Greater storage stability versus OsO4
· Facile recovery of catalyst
· Low levels of Os metal in final product
· Catalyst can be recycled

Reactivity of Os EnCat

Application Data


Os EnCatTM 40 has shown good catalytic activity in the dihydroxylations of acyclic and cyclic olefins of varying substitution patterns (Table I below). Catalyst efficiency is heightened by use of a single phase solvent in conjunction with the co-oxidant 4-methylmorpholine-N-oxide (NMO, 224286). Amounts of Os metal in the crude product mixture are normally in the 10-40 ppm range, which is acceptable for most pharmaceutical purity assays. To achieve optimum reaction rates, processes with Os EnCatTM are normally performed at elevated temperatures. Os EnCatTM 40 can be utilized in combination with chiral ligands such as [(DHQD)2PHAL] (Aldrich product 392766) to induce stereoselective transformations. Os EnCatTM 40 has also shown to be an effective catalyst for the oxidative cleavage of olefins to generate their respective carbonyl compounds under mild reaction conditions.

Dihydroxylation of Acyclic and Cyclic Olefins Using Os EnCatTM 40*:

Table I. *Conditions: Olefin (1 mmol), N-methylmorpholine-N-oxide (1.5 mmol), solvent (10 mL).

Product Name Product # 
Os EnCat™ 40: 0.3 mmol/g Os loading 658685
4-Methylmorpholine N-oxide 97% 224286
AD-mix-β 392766


Os EnCat™ 40 Experimental Guide (2.3 MB PDF)


Microencapsulation of Osmium Tetroxide in Polyurea. Ley, S. V. et al. Org. Lett., 2003, 5, 185-187.