Functionalization of Non-activated Positions

Reaction of 6 (3-hydroxy-steroids with ceric ammonium nitrate was reported to give the 6(3, 19-epoxides,123 and fragmentation of 5- and 19-hydroxy-compounds were also reported. A detailed investigation of the hypoiodite reaction and the related Pb(OAc)4 oxidation of a 5a-bromo-6(3-hydroxy-compound indicated that for the former a halocarbon solvent promotes 6(3,19-epoxide formation.124 Photolysis of the 17a-iodobenzoate (148) with PhICI2 gave the 9 -chloro-derivative (149) which on thermolysis gave a good yield of the 9(11), 16-diene (150).125 Photolysis of 

Reactions of 5a- and 5/3-androstane-3,17-diones with ozone in HF-SbFj gave directly the 6-oxo- and 7-oxo-compounds. Some epimerization of the 5j8-6-oxo- 

Drammann, M. Braun, and D. Seebach, Helv. Chim. Acta, 1976, 59, 2821. 

Sasamori, and T. Masamune, Bull. Chem. Soc. Japan, 1977, 50, 437. 

Wittig-Horner reaction (see p. 241). Photolysis of the nitrite of the 21-chloro-20-hydroxy-compound (194) gave the 18-oximino-compound (195) which on Jones oxidation was converted into the chlorolactone (196). Hypoiodite reaction of the 21-chloro-20-hydroxy-compound (194) also gives the chloro-lactone (196) which with modification gives 18-hydroxy-11-deoxycorticosterone (see also ref. 198). 

Functionalization of the methyl groups in the photolysis of the nitrites of 6-hydroxy-4,4-dimethyl steroids is used as a probe for conformational analysis. It is confirmed that in the 4,4-dimethyl-19-nor-series ring A has the normal chair 

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TBS-Protected 7-lactol is obtained through the formation of hypoiodite, followed by the formation of an alkoxyl radical, 1,5-H shift, and then formation of 8-iodoalcohol, and finally polar cyclization. The Fenton system with ROOH and Fe2+ also generates alkoxyl radical, RO. These reactions indicate that the Barton (-type) reactions are remote functionalization of non-activated C-H bonds at the 8- or e-position. 

The microbial hydroxylation of aliphatic compounds can effect the functionalization of molecules at positions distant from pre-existing groups. Such functionalizaton of non-activated positions is difficult to emulate using conventional chemistry. A good deal of research in this area has con-... 

In eqn. (65), A+B is a contact (externally solvated) ion pair, A+ B" is a solvent-separated ion pair (with solvent molecules between the ions), and A+, B are free (solvated) ions S stands for solvent. The initiating efficiency of a Lewis acid AB generally increases with a shift of the equilibria (65) from left to right. In the system monomer-initiator-(solvent) the concentration of active formations suitable for initiation and propagation is a function of the equilibrium position. In non-polar, poorly solvating media, only weakly... 

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