- Chloromethanesulfonate as an efficient leaving group: Rearrangement of the carbon-carbon bond and conversion of alcohols into azides and nitriles
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The chloromethanesulfonate (monochlate) served as an efficient leaving group for rearrangement of the carbon-carbon bond and conversion of alcohols into azides and nitriles. The treatment of the monochlate 16a with zinc acetate in dioxane at 90 °C effected migration of the 4α-methyl group to give alkene 17a. Upon similar treatment of the monochlates 22a, 25a, 28a, and 31a with zinc acetate, the carbon-carbon bonds antiperiplanar to the hydroxyl groups efficiently migrated to afford the alkenes 23a, 26a-c, 29a,b, and 32a, respectively. In the case of the diol 40, the monochlate was converted into the ketone 41 via a rearrangement-ring expansion. The reaction of the monochlates 44a, 47a, 49a, 52a, and 57a with sodium azide or lithium azide in N,N-dimethylformamide efficiently afforded the azides with inversion of the configuration. The introduction of a nitrile group to the sterically hindered alcohol 59 was performed in high yield by the reaction of the monochlate 60a with sodium cyanide.
- Shimizu, Takeshi,Ohzeki, Tomoya,Hiramoto, Katsuya,Hori, Nobuyuki,Nakata, Tadashi
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p. 1373 - 1385
(2007/10/03)
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- Ring-c Aromatic Steroids. Part 4. The c-Aromatic Analogue of Progesterone
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The ring-c aromatic analogue of progesterone, 18-norpregna-4,8,11,13-tetraene-3,20-dione (2), was formed together with its 17-epimer (3) when 9α,11α-epoxy-20ξ-hydroxy-3-oxopregn-4-eno-18,20-lactone (14) was subjected to oxidative decarboxylation, and the resulting products treated with boron trifluoride.The precursor (14) was synthesised as follows. 11α-Hydroxyprogesterone (4) was dehydrated, and the product then selectively reduced (by two routes) to 20β-hydroxypregna-4,9(11)-dien-3-one (9).The latter was functionalised at C-18 to give 3-oxopregna-4,9(11)-dieno-18,20-lactone (10) which was oxidised, after opening of the lactone ring, to the corresponding lactol (12).The latter was converted into the required lactol epoxide (14).Internal displacement on the 9α,11α-epoxide occurred when the lactol epoxide (14) was treated with acid, yielding 9α-hydroxy-3,20-dioxopregn-4-eno-18,11β-lactone (16).
- Burden, Peter M.,Cheung, H. T. Andrew,Ai, Tu Hoa,Watson, Thomas R.
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p. 2669 - 2674
(2007/10/02)
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