Tri(hetero)substituted Carbonium Ions. VII. Effect of the Ring System on the Ambident Reactivity of Cyclic Dithiocarbamidium Ions
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概要
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In order to study the effect of structure on the ambident reactivity of cyclic dithiocarbamidium ions, two <I>endo</I>-imimum type cations, 2-methylthio-3-methyl-4,5-dihydrothiazolium ion (<B>5</B>) and 2,3,5,6-tetrahydrothiazolo-[2,3-<I>b</I>]-thiazolium ion (<B>6</B>) were prepared. Their electrophilic reactivities were studied and compared with those of the <I>exo</I>-iminium type cations, 2-dimethylamino-1,3-dithiolan-2-ylium ion (<B>1</B>) and its ring analogues. 3-Di-methylamino-2,4-benzodithiepan-3-ylium ion (<B>7</B>) was prepared and its ambident reactivity was studied. Examination of the products obtained from their reactions with various nucleophiles revealed that the three cation have two reactive sites, <I>i.e.</I>, the central (sp<SUP>2</SUP>) carbon (site <I>a</I>) and the <I>S</I>-methylene (or <I>S</I>-methyl) (sp<SUP>3</SUP>) carbon atoms (site <I>b</I>). Significant differences in the electrophilic behavior of the <I>endo</I>- and <I>exo</I>-iminium type cations were observed. They were discussed in terms of the structures as estimated from the spectra. Kinetic experiments showed that the reactivities at site <I>a</I> of these cations with hydroxide ion, relative to that of <B>1</B>, are 22.5 (<B>5</B>): 16.6 (<B>6</B>): 27.2 (<B>7</B>), and at site <I>b</I> with <I>N</I>,<I>N</I>-dimethyldithiocarbamate ion are 3.3 : 282 : >10<SUP>4</SUP>. The reactivity order suggests that the reactivities at the two sites, especially at site <I>b</I>, are very sensitive to a change in the ring system of the cations.
- 公益社団法人 日本化学会の論文
著者
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Hiratani Kazuhisa
Reserach Laboratory of Resources Utilization, Tokyo Institute of Technology
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Nakai Takeshi
Reserach Laboratory of Resources Utilization, Tokyo Institute of Technology
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Okawara Makoto
Reserach Laboratory of Resources Utilization, Tokyo Institute of Technology