Issue 0, 1981

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

Abstract

Hypoiodites of cholesterol and epicholesterol in benzene containing mercury(II) oxide and iodine underwent photo-induced rearrangement to give 3α,5-epoxy-6β- and -6α-iodo-A-homo-4-oxa-5α-cholestanes (3) and (4), together with 3-formyloxy-2-iodo-A-nor-2,3-secocholest-5-ene (2). Stereochemistry of the epoxide (3) was established by an X-ray crystallographic analysis. When the reaction of cholesterol hypoiodite was induced thermally at 55–60 °C, only the 6β-isomer, accompanied by cholest-5-en-3α-yl A-homo-4-oxacholest-5-en-3α-yl ether (20) and A-homo-4-oxacholest-5-en-3α-ol (21), is formed. Catalytic hydrogenolysis of iodo-epoxide (3) or (4) gave 3α,5-epoxy-A-homo-4-oxa-5β-cholestane (16) which was transformed into 2-acetyl-5-acetoxymethyl-4-oxa-5β-cholest-2-ene (29) upon treatment with boron trifluoride–ether–acetic anhydride in benzene.

In contrast, the newly synthesized hypoiodite of 3α,4,4-trimethylcholest-5-en-3β-ol, in benzene containing mercury(II) oxide and iodine, gave 2-acetyl-3-oxacholest-5-enes (26) and (27) together with 3α,5α-epoxy-A-homo-4-oxasteroids (24) and (25) on irradiation or thermolysis. The formation of the products (26) and (27) indicates the intervention of a common oxyl radical (E) in the rearrangements of 3-hydroxy-Δ5-steroid hypoiodites to products (3), (4), (24), (25), (26), and (27). The pathways of the rearrangements and the stereoselectivity of the reactions are discussed.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 1, 1981, 236-250

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

H. Suginome, A. Furusaki, K. Kato, N. Maeda and F. Yonebayashi, J. Chem. Soc., Perkin Trans. 1, 1981, 236 DOI: 10.1039/P19810000236

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