Synthesis of polysubstituted dihydropyrroles and pyrroles from β-carbonyl O-methyloximes
摘要:
Polysubstituted 4,5-dihydropyrroles and pyrroles were synthesized from beta-carbonyl O-methyloximes via alkylation and intramolecular Michael addition with unsaturated 4-bromobutyrates by treatment with sodium hydride or a sodium alkoxide. (C) 2004 Elsevier Ltd. All rights reserved.
[image omitted] The reactions between different N,O-bis-trimethylsilyl-carbamates and oxo compounds were studied. The N,O-bis-trimethylsilyl-N-methoxy-carbamate converts ketones to the corresponding O-methyl oximes. The product is usually a mixture of syn and anti isomers. If the carbonyl compound bears a hydroxyl group, the oxime formation and the O-silylation take place simultaneously. In the case of -haloketones, the undesired substitution of halogen was not observed. The reactions between N,O-bis-trimethylsilyl-N-methyl-carbamate and oxo compounds resulted in the corresponding imines, although the yield are moderate in some cases. Analoguos reaction of ferrocenylated oxo derivatives gave similar results.