Sanya Akaboshi

The roles of hetero atoms in solvolytic reactions—II: Transannular participation by neighbouring sulphur atom

Abstract Esters of sulphur-containing 5- and 6-membered heterocycles, tetrahydro-3- and 4-thiopyranol and their 3- and 4-methyl, phenyl derivatives, and tetrahydro-2-thiophenemethanol, were synthesized. The solvolysis of β-thioesters in 80% aqueous acetone resulted in strong transannular S-participation and the products of solvolysis substantiated formation of bicyclic episulphonium ion intermediates. Such participation is considered to be present even in a tertiary system. On the other hand, γ-thioesters were solvolysed without any transannular S-participation,

2-Aminoindoles : Preparation from 2-indolinethiones, tautomerism and autoxidation

Abstract 2-Aminoindoles (2 and 4) have been prepared by the reaction of 2-indolinethiones (1) with primary and secondary aliphatic amines. The reaction of 1b with ethyleneimine produced the S-alkylated product 5, and with phenylhydrazine compound 9. The reaction 1b with aniline and 10 with piperidine failed to give an 2-aminoindole derivative or 12. The UV and NMR spectra of the free base 2 shows the presence of a tautomeric mixture of 13 and 14 in bases 2c, 2g, 2h and 2i. The free base 2b in CDCl3 exists substantially in the indolenine form 15. The free bases of 2b, 2g, 2h and 2i are susceptible to autoxidation to 3-oxo derivatives (19, 21, 22 and 23).

The roles of hetero atoms in solvolytic reactions—I: Preferential effect by nitrogen to facilitate carbonyl-oxygen cleavage of esters

Abstract 3- and 4-Piperidinyl and 2-pyrrolidinylmethyl halides and p-nitrobenzoates were prepared. In the solvolysis, the remarkable difference in the effect of nitrogen on the two kinds of the leaving groups was observed. Halides underwent the solvolysis of SN1 mechanism, whereas p-nitrobenzoates resulted in the preferential OCO cleavage. The results of IR absorption of ester-carbonyl group and kinetic deuterium isotope effect suggested that in the solvolysis of the esters, an initial solvation may be important for the cleavage of a OCO bond.