Highly Controlled Chemoselectivity of Tin Enolate by Its Hybridization State. Anionic Complex of Tin Enolate Coordinated by Tetrabutylammonium Bromide as Halo Selective Reagent
| Autor: | Ken-ichiro Hayashi, Yasuhiro Katoh, Makoto Yasuda, Ikuya Shibata, Akio Baba |
|---|---|
| Rok vydání: | 1998 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 120:715-721 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja972190s |
| Popis: | The control of reactivity and/or selectivity of organotin(IV) enolates has been studied by means of a high coordination method in which the hybridization state of tin was effectively changed. An anionic tin complex, five-coordinated tin enolate 1(h), was formed by the coordination of bromide anion from tetrabutylammonium bromide (Bu4NBr) to neutral four-coordinated tin(IV) enolates 1(e). The highly coordinated enolates which attained a marked change in chemoselectivity have higher nucleophilicity to organic halides. In addition, they showed low nucleophilicity toward carbonyl moieties by the coordination of the bromide anion, whereas carbonyl addition readily proceeds using the usual four-coordinated tin enolate. NMR studies revealed the generation of HMPA- or bromide-anion-coordinated tin enolates in equilibrium between four-coordinated enolate 1c(e) and five-coordinated enolate 1c(h), showing a considerable upfield shift δ(119Sn) and increasing values of the coupling constants 1J(119Sn−13C). In detailed... |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|