Synthesis of Multicyclic Butyrolactones by Selective Oxidation of Tetrahydrofuran Derivatives with Ruthenium Tetraoxide
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چکیده
0002-7863/82/1504-6842$01.25/0 the original alcohol substituent. Similar annulations from allylic alcohols via unsymmetrical diallyl ethers are demonstrated by Table I1 entries g-j. The requisite diallyl ethers for photoannulation of 2g-j are readily available by Williamson synthesis from the hydroxy olefin precursors indicated. It is noteworthy that the stereochemistry of the substituent R' in 3i and 3j is exclusively exo.I6 This synthetically valuable stereoselectivity is in sharp contrast with a topologically different previous synthesis of 3i by intermolecular photocycloaddition of ethylene with 4, which affords an equal yield of the endo-epimer 5 (eq 3).17 The requisite diallyl
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