Science of Synthesis

Nativi, C.; Roelens, S., Science of Synthesis, (2008) 36, 758.

To minimize problems associated with the toxicity and the high cost of osmium(VIII) oxide, which makes the stoichiometric osmylation dangerous and uneconomical, catalytic variants that employ inexpensive reagents for the reoxidation of the osmium(VI) product have been developed.[‌10‌] One of the most effective methods was developed by VanRheenen, Kelly, and Cha at Upjohn, who used tertiary amine N-oxides, such as 4-methylmorpholine N-oxide, as both an oxidant for the osmium(VI) product, and the decomposing agent of the osmium ester.[‌11‌] Osmylation reactions using 4-methylmorpholine N-oxide can be performed at room temperature with as little as 1 mol% of osmium(VIII) oxide. This method is superior to other syn-hydroxylation procedures as only small amounts of osmium(VIII) oxide are required and, in addition, overoxidation byproducts are minimized.[‌10‌] The solvents generally employed are aqueous acetone, tetrahydrofuran, or tert-butyl alcohol (as either one- or two-phase mixtures). Although these solvents can be used in different combinations the optimized system uses acetone/tert-butyl alcohol/water in a ratio of 18:1:1. With hindered alkenes, osmylation with 4-methylmorpholine N-oxide is often sluggish; in such cases the use of trimethylamine N-oxide gives better results. The catalytic osmylation of alkenes has been extended to potassium aryl- and alkyltrifluoroborates such as ‌2‌ (‌Scheme 2‌). The resulting diols ‌3‌ are effective coupling partners in Suzuki–Miyaura coupling reactions.[‌12‌]

‌Meeeee 8‌ Meeeeeeeeeeeeee ee Meeeeeeee Meeeeeeeeeeeeeeeeeeee[‌88‌]

Meeeeeeeeeee Meeeeeeee

Meeeeeeee Mee-8-ee-8-eeeeeeeeeeeeeeeee (‌8‌); Meeeeee Meeeeeeee:[‌88‌]

MMMMMMM: Meeeeeee ee eeeeee(MMMM) eeeee eee eeeeee ee eeeee eeeeeeeeeeeeee, eee eeeeeeeeee eeee eeeeeee eeee eeeeeeeee.

M 8% e/e eeee ee MeM8 ee M8M (8.8 eM), eee MMM (888 ee, 8.88 eeee), eeee eeeee ee e eeee ee eeeeeeeee eeeeeeeeeeeeeeeeeeee ‌8‌ (888 ee, 8.88 eeee) ee e eeeeeee ee eeeeeee (8.8 eM), e-MeMM (8.8 eM), eee M8M (8.8 eM) ee ee. Meee eeeeeeeeee (eeeeeeeeee ee 8M MMM), Me8M eee eeeee ee eee eeeeeee eeeee ee eeee eeeeeeeeeeeee eee eeeeeeee. Mee eeeeeeeeeee eee eeeeeeeee, eeeeee eeee eeeee eeeeeeee ee Me8M, eee eeeee eeeee eeee eeeeee; eeeee: 888 ee (88%); ee 888°M; 88M MMM (MMMM-e8, δ): 888.8; 88M MMM (MMMM-e8, δ): 8.88.

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) 8/8e8, 888.
• 8.Meeeee-Meee, (8888) M 8e8, 88.
• 8.Meeeee-Meee, (8888) M 88e, 8888.
• 8.Meeeee-Meee, (8888) M 88e, 8888.
• 8.Meeeee-Meee, (8888) M 88e, 8888.