- The synthesis of 5-substituted proline derivatives and of 5-substituted pyrrole-2-carboxylates by 5-endo cyclisations featuring a method for effectively favouring these with respect to 5-exo cyclisations
-
Overall 5-endo cyclisations of the C-allylic glycine sulfonamides 5 lead to usually excellent yields of the 2,5-cis- or 2,5-trans-pyrrolidine-2-carboxylates 11 and 12 respectively, depending upon whether base is absent or present. While reductions to the corresponding pyrrolidine-2-methanols 13 proved efficient, subsequent eliminations of the elements of hydrogen iodide gave mixtures of products 14-16. Suitably positioned hydroxy groups compete successfully with the sulfonamide via a 5-exo cyclisation mode. However, when such a substrate contains a furan ring attached to the alkene function (21), then cyclisation does occur at the sulfonamide, presumably by participation of the furan oxygen, to give an iodopyrrolidine-2-methanol 13a. Finally, base-induced elimination of both hydrogen iodide and toluene-p-sulfinic acid from the initial iodopyrrolidines 11 and 12 leads to 5-substituted pyrrole-2-carboxylates 26. Overall, this sequence is complementary to the Kenner pyrrole synthesis.
- Knight,Redfern,Gilmore
-
p. 2874 - 2883
(2007/10/03)
-
- SYNTHESIS OF α-AMINOACIDS BY CATALYTIC PALLADIUM (O) ALKYLATION OF BASES
-
Schiff bases 1 b, 1 c, 2 derived from glycine ester or aminoacetonitrile were alkylated with allylic acetates 3 a, 3 b or allylic carbonates 3 c, 3 d, 4 a, 4 b (under neutral conditions) in presence of catalytic amount of palladium (O).After hydrolysis higher and functionalized α-aminoesters were obtained in good yields (50 to 85 percent).
- Ferroud, D.,Genet, J. P.,Kiolle, R.
-
-