Cadmium(II) Chloride-Catalyzed Dehydrative C−P Coupling of Propargyl Alcohols with Diarylphosphine Oxides to Afford Allenylphosphine Oxides
作者:Jianlin Yang、Ming Zhang、Kang Qiu、Lize Wang、Jingjing Yu、Zefeng Xia、Ruwei Shen、Li-Biao Han
DOI:10.1002/adsc.201700957
日期:2017.12.19
The reaction can also be easily scaled up to a gram‐scale synthesis. A mechanism study indicates that the reaction may proceed through a process of propargylic substitution to generate phosphonite intermediates followed by [2,3] sigmatropic rearrangement to produce the allenyl products, rather than through a common allenylative substitution resulting from P‐nucleophilicity.
We describe herein a highly stereoselective access to Cbz-protected β-enaminones 2 based on the NaOH catalyzed rearrangement of propargylichydroxylamines 1. The synthetic potential of these β-enaminones is illustrated in an original synthesis of pyrimidines.
Dehydrogenative Meyer-Schuster-Like Rearrangement: A Gold-Catalyzed Reaction Generating an Alkyne
作者:Yang Yu、Weibo Yang、Daniel Pflästerer、A. Stephen K. Hashmi
DOI:10.1002/anie.201307647
日期:2014.1.20
oxidative gold‐catalyzed reaction. Gagosz’s catalyst in combination with PhI(OAc)2 is the best system for this conversion and 18 examples with yields up to 80 % are reported. The results indicate that the triple bond in the product is formed by elimination from a vinylgold intermediate. In a formal sense the new conversion overall is a dehydrogenative Meyer–Schuster rearrangement.
Pd(II)-catalyzed ligand-controlled switching between cyclization-carbonylation and cyclization-carbonylation-cyclization-coupling (CCC-coupling) reactions of propargylic N-hydroxylamines was investigated. The use of a [Pd(tfa)2(box)] catalyst in MeOH afforded symmetric ketones bearing two 2,3-dihydroisoxazoles in good yields; replacing the catalyst and solvent with Pd(tfa)(2) and MeOH/DMSO led to the formation of methyl 2,3-dihydroisoxazole-4-carboxylates in good yields.