A novel “Ti(O)” induced allylation of imines in a TiCl4 (cat.)/A1 bimetal system. Chirality transfer of l-valine to homoallylamine
✍ Scribed by Hideo Tanaka; Keizo Inoue; Ulrike Pokorski; Masatoshi Taniguchi; Sigeru Torii
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- French
- Weight
- 223 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
Barbier Type" allylation of imines with ally1 bromide has been performed successfully by the action of aluminum (1 equiv.) and titanium(W) chloride (0.05 equiv.) in THF. The chirality transfer of a-amino acid esters to homoallyl amines is demonstrated by allylation of N-benzalvaline methyl ester followed by alkaline hydrolysis and electrolytic decarboxylation.
Low valent titanium, "Ti(O)", generated by the reduction of titanium(II1 or IV) salts with appropriate reductants, e.g., Mg.1 Mg-Hg,2 Zn,3 and LiAlH4,4 has been widely utilized in modem organic synthesis. The low valent titanium "Ti(O)"S has always been prepared immediately before use. Therefore, the hitherto disclosed '"H(0)"-promoted reactions are stoichiometric with respect to titanium and no successful attempt to recycle use of '"Ii(O)" has been recorded,6 presumably because of lack of proper reducing agents for regeneration of "Ti(0)" in the reaction media. Herein, we disclose the first example of a catalytic use of titanium which can effect "Barbier Type" allylation of imines 1 in combination with aluminum metal (reducing agent) (Scheme 1).