Solvolysis in carboxamides. II. Solvolytic elimination of 7.BETA.-methylbicyclo[3.3.1]non-3.BETA.-yl tosylate in carboxamides.

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概要

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• Solvolysis of 7β-methylbicyclo[3.3.1]non-3β-yl tosylate (<B>1</B>) was carried out in a series of carboxamides, <I>N</I>-methylformamide (NMF), <I>N</I>-methylacetamide (NMA), <I>N</I>,<I>N</I>-dimethylformamide (DMF), and <I>N</I>,<I>N</I>-dimethyl-acetamide (DMA), as solvents. The rate (<I>k</I><SUB>1</SUB> first-order rate constant) of <B>1</B> decreases in the order NMF>NMA>DMF>DMA, a linear free-energy relationship being found between the rates of <B>1</B> and those of 1-adamantyl tosylate in acetic acid and 80% ethanol as well as the carboxamides. The products consist of olefin (<I>≥</I>96%) (<I>exo</I>-7-methylbicyclo[3.3.1]non-2-ene (<B>4</B>) and 3-methylbicyclo[3.3.1]non-2-ene (<B>5</B>)) and small amounts of esters (acetates or formates, <I>≤</I>4%). The content of rearranged olefin <B>5</B> is considerably less than that of acetolysis (55%) and ethanolysis (55%), decreasing in the order NMF (34%)>NMA(22%)>DMF(13%)>DMA(9%). A linear reactivity-selectivity relationship holds between log <I>k</I><SUB>1</SUB> and log (%<B>5</B>/%<B>4</B>) for the four carboxamide solvents. The observed kinetic isotope effect (<I>k</I><SUB>H</SUB>/<I>k</I><SUB>D</SUB>=1.01±0.03) for 7α-deuterium-tagged derivative (<B>1</B>-7α-<I>d</I>) in NMF indicates that the σ(C(7)–H)-assisted ionization process for the solvolysis of <B>1</B> in the amides is absent. The results are in line with the stepwise mechanism which involves the formation of an intimate ion-pair intermediate followed by competitive processes such as 1,5-hydride shift, <I>syn</I>-El reaction, and nucleophilic substitution by the amide molecules. Substitution by the amide molecule leads to the formation of a cationic imidate, the hydrolysis of which affords the carboxylic esters. It is proposed that the <I>syn</I>-El process <I>via</I> an intimate ion-pair intermediate is affected by the tosylate anion reactivity in each amide solvent and suppressed by the hydrogen bonding of the each amide with the tosylate anion.

• 公益社団法人 日本化学会の論文

著者

• Saito Seiki

  Department Of Bioengineering Science Faculty Of Engineering. Okayama University

• Okamoto Kunio

  Department of Fuel Chemistry Faculty of Engineering Kyoto University

• Yabuki Tatsumi

  Department of Synthetic Chemistry, School of Engineering, Okayama University

• Yabuki Tatsumi

  Department of Synthetics Chemistry, School of Engineering, Okayama University

• Moriwake Toshio

  Department of Synthetics Chemistry, School of Engineering, Okayama University

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