- RHODIUM CARBENOID MEDIATED CYCLISATIONS. USE OF ETHYL LITHIODIAZOACETATE IN THE PREPARATION OF ω-HYDROXY-, -MERCAPTO-, AND -Boc-AMINO-α-DIAZO-β-KETO ESTERS
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Reaction of ethyl lithiodiazoacetate with lactones, thiolactones, and lactams (1, 4, 8) gives the diazo-compounds (2, 5, 9), substrates for rhodium carbenoid cyclisation reactions.
- Moody, Christopher J.,Taylor, Roger J.
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- Rhodium carbenoid mediated cyclisations. Part 3. Synthesis of cyclic ethers from lactones
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Ethyl lithiodiazoacetate ring opens lactones, N-Boc lactams, and cyclic anhydrides and carbonates to give ω-functionalised α-diazo-β- keto esters in varying yield (Tables 1 and 2). Thus simple 5-, 6-, 7-, and 8-membered lactones react to give α,ω-diazo alcohols, and benzo-fused lactones give diazo phenols. The corresponding reaction with N-Boc lactams gives Boc-amino diazo compounds, and cyclic anhydrides give α,ω-diazo carboxylic acids. Treatment of the diazo compounds derived from 5-, 6-, and 7-membered lactones with a catalytic amount of rhodium(II) acetate resulted in rhodium carbenoid mediated cyclisation to give 6-, 7-, and 8-membered cyclic ethers (Table 3). Attempted preparation of larger rings, however, resulted in formation of cyclopentanones by competing C-H insertion reactions. Similarly, the Boc-protected amino diazo compounds only gave the products of C-H insertion on treatment with rhodium(II) acetate.
- Moody, Christopher J.,Taylor, Roger J.
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p. 721 - 731
(2007/10/02)
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