- Silicon and tin-directed Tiffeneau-Demjanov reaction
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Silicon and tin substituents surprisingly have only a moderate directing effect on the Tiffeneau-Demjanov reaction. The low selectivity is rationalised as being due to the reactive nature of the diazonium ion leaving group, the weaker oxydiazene leaving g
- Chow, Leonie,McClure, Melanie,White, Jonathan
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p. 648 - 650
(2007/10/03)
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- (TRIALKYLSTANNYL)COPPER(I) REAGENTS: PREPARATION AND REACTION WITH α,β-UNSATURATED CARBONYL SYSTEMS. PREPARATION OF β-TRIALKYLSTANNYL α,β-UNSATURATED KETONES
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Reaction of Me3SnLi with 1 equivalent of CuBr*Me2S, PhSCu, Me2(MeO)C-CC-Cu, or CuCN in tetrahydrofuran (THF) affords the (trimethylstannyl)copper(I) reagents Me3SnCu*Me2S (1) and Li (Y = PhS (2), Me2(MeO)C-CC (4), CN (5)), respectively.Similarly, treatment of a THF solution of Me3SnLi with 0.5 equivalent of CuBr*Me2S provides (Me3Sn)2CuLi (3), while reaction of n-Bu3SnLi with PhSCu (1 equivalent) gives Li (6).Reagents 2 and 6 readily transfer (in a conjugate sense) the R3Sn group to conjugated enones (e.g. 7-9) and structurally simple enoates (e.g. 10), but do not react with β,β-disubstituted α,β-unsaturated esters (e.g. 11-13).Reaction of reagent 2 with the enone 26 under normal conditions produces, in addition to the expected ketone 28, a significant amount of the double conjugate addition product 30.A similar result is obtained with ethyl propenoate (27).However, reaction of 26 and 27 with reagent 2 in the presence of acetic acid provides cleanly and efficiently the simple conjugate addition products 28 and 29, respectively.Reagent 1 does not react, or reacts very sluggishly, with α,β-unsaturated carbonyl compounds. β-Trialkylstannyl α,β-unsaturated ketones (e.g. 37-46) can be produced smoothly and efficiently by reaction of the corresponding β-iodo enones (e.g. 32-36) with reagents 2 (or 1) and 6.
- Piers, Edward,Morton, Howard E.,Chong, J. Michael
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