Asymmetric reduction of oxime ethers. Distinction of anti and syn isomers leading to enantiomeric amines.
作者:Yoji Sakito、Yukio Yoneyoshi、Gohfu Suzukamo
DOI:10.1016/s0040-4039(00)80059-3
日期:1988.1
Anti and syn ketoxime ethers were reduced with a chiral reducing agent prepared from (−)-norephedrine and 2 eq of BH3 to give S and R amines respectively in up to 92% ee. The preferred absolute configuration of the amine was depended on the geometry of the oxime ether.
The TiIV -mediated synthesis of spirocyclic NH-azetidines from oximeethers using either an alkyl Grignard reagent or terminal olefin ligand exchange coupling partner is described. Through a proposed Kulinkovich-type mechanism, a titanacyclopropane intermediate forms and serves as a 1,2-aliphatic dianion equivalent, inserting into the 1,2-dielectrophilc oximeether to ultimately give rise to the desired
Synthesis of Aldehydes from Carboxylic Acids via<i>N</i>-Methoxyimidoyl Bromides: Deoximation of<i>O</i>-Methyloximes
作者:Takeshi Sakamoto、Yasuo Kikugawa
DOI:10.1055/s-1993-25903
日期:——
Aldehydes are synthesized by hydrogenation and subsequent deoximation of substituted N-methoxyalkanimidoyl bromides, which are prepared in one pot by reaction of the corresponding carboxylic acids with methoxyamine and triphenylphosphine carbon tetrabromide. Regeneration of aldehydes and ketones from O-methyloximes under mild conditions is also described.
Intramolecular cyclization of alkylhydroxylamines in acids.
作者:MASAMI KAWASE、YASUO KIKUGAWA
DOI:10.1248/cpb.29.1615
日期:——
Alkylhydroxylamines having a benzene ring in the molecule were subjected to intramolecular cyclization in trifluoroacetic acid or in the presence of Lewis acids, and benzenefused six-membered heterocycles were obtained in moderate yields from the cyclization reaction of O-acylhydroxylamines. The effect of a methoxyl group on the benzene ring was also investigated. The m-methoxy compound (1j) cyclized to give 6-methoxy-2-methyl-1, 2, 3, 4-tetrahydroquinoline (2e), while the p-methoxy compound (1k or 1l) cyclized to give the same product (2e). These unusual results could be explained in terms of a spiro-intermediate (3a).