Mono-oxygenation

The addition of ethoxyacetylene to 17-keto steroids has been discussed earlier. The 17a-ethoxyethynyl-17jS-hydroxy compounds thus produced can be readily converted to 21-mono-oxygenated pregnanes by acid treatment. 

Preparation of 20-monO-oxygenated pregnanes by side-chain oxygenation of pregnanes... 

Sample Time (h) Si/M ratio Cyclohexane Conversion (%) TBHP Conversion (%) Mono- oxygenated selectivity (%) Ketone/ Alcohol ratio... 

Results of the cyclohexane oxidation tests are shown in Table 41.4. Mono-oxygenated products are cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide. Cu and Cr were very active, but subsequent tests showed considerable leaching for both metals, whereas Co-Si-TUD-1 did not show ai r leaching. Tests with different Co loadings indicate that the lowest Co concentration has the best conversion and ketone selectivity. Isolated cobalt species are most efficient for the conversion of cyclohexane, as agglomeration of Co reduces... 

Thus, it was shown that Co-Si-TUD-1 is a highly active catalyst for the oxidation of cyclohexane, has a high selectivity for mono-oxygenated species and cyclohexanone, and can be used repeatedly. 

Monooxygenases, 25 382, 383 reactions effected by, 25 383 Mono-oxygen species, characterization, 32 111-112... 

We also enconnter tautomerism in hydroxy- and amino-diazines, and the preference for one tautomeric form over the other follows what we have seen with the pyridine derivatives. Thus, with the exception of 5-hydroxypyrimidine, all the mono-oxygenated diazines exist predominantly in the carbonyl tan-tomeric form. We term these amide-like tautomers diazinones. 5-Hydroxypyrimidine is analogous to 3-hydroxypyridine, in that the hydroxyl is wrongly positioned for tautomerism. 

Coon, M. J. and White, R. J. (1980) Cytochrome P450 a versatile catalyst in mono-oxygenation reactions. In Metal ion activation of dioxygen. Wiley, New York. 

Better yields of the mono-oxygenated product and the concurrent generation of higher oxides can be achieved by oxidahon with m-chloroperoxybenzoic acid (MCPBA) (Scheme 8.2) [20-24] Cjq and usually about 10 to 30 equiv. of the peroxy acid are stirred in toluene at 80 °C [21]. The product distribuhon can be influenced by reaction hme and the amoimt of acid. The existence of the C gO-isomer 1 -accessible in 30% yield - and the ds-l-CgQ02-isomer 2 - accessible in 8% yield -could be proven (Scheme 8.2) [21], but higher oxides CggO up to n = 12 can also be formed [24]. The main products are oxides with n = 1-3. 

The mono-oxygen species on the surface fall into two main types O ions formed either by adsorption or from surface oxide ions of the lattice and O2 ... 

Mono-oxygen transfer from peroxoW to a halide such as Br leads to in situ production of Br+ , which is useful for bromination, or even for Br-assisted epoxidation [11]. 

IV. Side-Chain Oxygenation of Pregnanes / 162 17-Mono-oxygenated pregnanes / 162... 

---