Selenium-mediated conversion of alkynes into .alpha.-dicarbonyl compounds
摘要:
The reaction of terminal and internal alkynes with diphenyl diselenide and ammonium peroxydisulfate in methanol proceeds smoothly to give alpha-keto acetals and alpha-keto ketals, respectively. This one-pot procedure is suggested to proceed through the initial formation of phenylselenenyl sulfate, a strong electrophilic reagent which effects the methoxyselenenylation of the alkynes. The addition products thus formed suffer methoxydeselenenylation giving the observed products and regenerating the phenylselenenylating agent. In some cases the reaction can be carried out using only catalytic amounts of diphenyl diselenide. The same reaction carried out in the presence of water or of ethylene glycol gives the unprotected or the diprotected alpha-dicarbonyl compounds, respectively.
The Weinreb amides 2a,b were prepared from the α,α-dimethoxyacetic acids 1c,d. A number of representative nucleophilic additions (RMgX and RLi) on 2 afforded α-ketoacetals 3a–j in 70–99% yield. These compounds represent a versatile arrangement of functional groups of significant synthetic value, as demonstrated in the synthesis of (±)-salbutamol.
Selective Protection of the Functionalities of α-Hydroxy Unsaturated Aldehydes
作者:L. Khamliche、S. Bakkas、A. Robert
DOI:10.1055/s-1994-25652
日期:——
The polyfunctionalized title compounds α-enol aldehydes are selectively protected either as ethylenic aldehyde acetates, ethylenic aldehyde sulfonates, ethylenic acetal sulfonates, or oxo acetal derivatives.
Kinetic and mechanistic studies on the rearrangement of 1-(substituted phenyl)-1,3-dimethoxy-2-propanones
作者:Guo-qiang Cheng、Zhi-fen Li、Pang Zhang
DOI:10.1016/s0008-6215(00)90539-1
日期:1991.8
mechanism of rearrangement of 1-(substituted phenyl)-1,3-dimethoxy-2-propanones to give substituted benzylglyoxal dimethyl acetals ( 5 ) was studied by kinetic measurements, by the effects of acid catalysis, by rearangements in the absence of acid and in the presence of base, by solventeffects, by effects of temperature, and by mass spectroscopy. It is concluded that the title ketones rearrange by a sigmatropic
摘要通过动力学测量,酸催化作用,在不存在苯甲酸的情况下进行重排,研究了1-(取代苯基)-1,3-二甲氧基-2-丙烷重排生成取代的苄基乙二醛二甲基乙缩醛(5)的机理。酸和碱的存在下,通过溶剂的作用,通过温度的影响,和通过质谱。结论是,标题酮是通过σ而不是S n 1'的烯丙基位移而重排的。
DDQ mediated one step dimerisation of beta-asarone or beta-asarone rich acorus calamus oil in the formation of novel neolignan
申请人:Council of Scientific & Industrial Research
公开号:US20030187306A1
公开(公告)日:2003-10-02
The present invention relates to a novel neolignan (NEOLASA-I) 3-ethyl-2-methyl-3-(2″,4″,5″-trimethoxy-phenyl-1-(2′,4′,5′-trimethoxy)phenyl-1-(2′,4′,5′-trimethoxy)phenyl-1-propene and a process for the preparation of high purity, higher yield neolignan, &agr;-asarone, 2,4,5-trimethoxy-phenyl propionone from &bgr;-asarone or &bgr;-asarone rich
Acorus calamus
oil containing &agr; and &ggr;-asarone by hydrogenating and dimerizing by treatment with DDQ in presence of an organic acid.
Process for 3,4-dimethoxyphenyl-acetone preparation
申请人:LARK S.p.A.
公开号:EP0247526A2
公开(公告)日:1987-12-02
A process for preparing 3,4-dimethoxyphenylacetone is disclosed, which consists in electrolytically epoxidating isoeugenol-methylether in a mixture consisting of water and of a dipolar aprotic solvent, in the presence of Br⁻ ions, and in isomerizing the so-obtained epoxide, in an inert organic solvent, in the presence of catalytic amounts of lithium salts, by means of a heating at temperatures comprised within the range of from 50°C up to the solvent refluxing temperatures.