Isomerisation radicalaire de l'oxepanne. Un nouveau type de cyclisation homolytique sur un carbonyle.

Photo-induced transformations. Part 51. Photo- and thermally-induced rearrangements of hypoiodites of steroidal homoallyl alcohols. The formation of some oxygen heterocycles via photo- and thermally-induced rearrangements of 3-hydroxy-Δ5-steroid hypoiodites in the presence of mercury(II) oxide and iodine

“…Species (C) appears to be unimportant in the present reaction, and in fact a recent work has shown the formation of cyclohexanol from an oxepan radical, and the equilibrium (A) =+= (B) e (C) seems to lie largely towards the oxygen-centred radical . 22 Thus, the stereochemical outcome of the present reactions can be understood as a consequence of the initial preferred arrangements of the formyl group and the planar ally1 radical portion of the radical (D).…”

“…The residue was subjected to column chromatography (silica gel, 70-270 mesh, 4.5 g) . Elution of the residue with hexane-benzene (1 : 1) afforded the alcohol (21) (10 nig) and then cholesterol Preparation of 3P-Hydroxy-Sa,4,4-trimethylchoZest-5-ene (23) .--4,4-Dimethyl-3-oxacholest-5-ene (22) (1.8 g) in d r y diethyl ether (120 ml) was added dropwise to a stirred solution of methylmagnesium iodide, prepared from methyl iodide (2 ml) and magnesium turnings (500 mg) in dry diethyl ether (30 ml), under an atmosphere of nitrogen. The solution was set aside overnight at room temperature and was poured into ice-water containing ammonium chloride.…”

“…5 Hz,9.32 (3 H, s, lS-Me), and 8.93, 8.89, or 8.83 (3 H, s, 19-Me). Further elutions with hexanebenzene (4 : 3), hexane-benzene (1 : l), benzene, and finally diethyl ether gave a fraction which was recrystallized from methanol to give 3~-hydroxy-3a,4,4-trimethylcholest-5-ene The Irradiation of 3p-Hydroxy-3a,4,4-trinzethyZcholest-5ene Hypoiodite in the Presence of Mercury(r1) Oxide and Iodine .-3P-Hydroxy-3a, 4,4-trimethylcholest-5-ene (22) (500 mg, 1.17 mmol), mercury(I1) oxide (740 mg, 3.42 mmol), and iodine (860 mg, 3.38 mmol) in benzene (60 ml) were irradiated under a nitrogen atmosphere for 8 h. The solution was filtered and the filtrate was extracted with tliethyl ether. The organic layer was twice washed with 50/, aqueous sodium hydrogensulphite solution, then with water, and dried (Na,SO,).…”

Practical Synthesis of (±)-Chlorovulone II

“…Plausible substrates for the planned transformations were aldehydes 6 − 8 or even a glyoxal analog, 9 . Whereas ene reaction of 6 − 8 would be followed by suitable activation of the vinyl ether and radical cyclization into an olefinic π system, use of glyoxal equivalent 8 would ultimately entail a radical−carbonyl cyclization. , …”

The Study of the Kinetics of Intramolecular Radical Cyclizations of Acylsilanes via the Intramolecular Competition Method

“…The carbonyl functional group plays a central role in organic chemistry. Radical cyclizations involving carbonyls which produce cyclic alcohols were first reported in 1976 by Flies et al and later extensively studied by Fraser-Reid and others . For example (eq 1), the cyclization of ε-iodo aldehyde 1 was reported to give alcohol 2 in 85% yield 4b.…”