铑(II)可以通过分子内的氮杂C–H插入反应有效地促进芳基氨基甲酸酯底物的活化和环化,从而生成苯并恶唑啉酮。对底物范围的研究表明,该反应在更不稳定的o -C(sp 3)-H键上进行了选择性芳族C(sp 2)-H胺化反应。反向二次KIE的观察结果(P H / P D = 0.42±0.03)表明,芳族亲电取代机理参与了芳基CH酰胺化反应。
Alkyl-phenylcarbamate derivative of polysaccharide
申请人:DAICEL CHEMICAL INDUSTRIES, LTD.
公开号:EP0281951A1
公开(公告)日:1988-09-14
An alkyl-phenylcarbamate derivative of a polysaccharide has in 80 to 100 percent of hydrogen atoms of the amino and hydroxyl groups an alkylphenyl-carbamoyl group having the formula (I):
in which (1) at least one of R1 to R5 is a straight alkyl having 4 to 8 or a branched alkyl having 3 to 8 carbon atoms or at least two of R1 to R5 each are a straight alkyl having 1 to 3 when the polysaccharide is cellulose; (2) at least one of R1 to R5 is a straight alkyl having 1 to 8 carbon atoms or a branched alkyl having 3 to 8 carbon atoms when the polysaccharide is any one other than cellulose; and the other(s) of R1 to R5 is hydrogen. It is useful to optical separation of a racemic mixture.
The invention relates to polyphenyl polymethylene polyisocyanates having an NCO number of at least 29% comprising less than 2% by weight ureas, less than 8% by weight carbodiimides or uretonimines and less than 1000 ppm organic chlorine compounds.
The polyphenyl polymethylene polyisocyanates can be prepared according to the invention by reacting
(i) polyphenyl polymethylene polyamines with organic carbonates to give the corresponding polyphenyl polymethylene polycarbamates,
(ii) by thermally cleaving the polyphenyl polymethylene polycarbamates to give the polyphenyl polymethylene polyisocyanates,
wherein, prior to the thermal cleavage, the free amino groups or urea groups present in the carhamate crude mixture comprising the polyphenyl polymethylene polycarbamates are reacted with a derivatizing reagent to give amide groups or urethane groups.
The polyphenyl polymethylene polyisocyanates can further be prepared according to the invention, prior to the thermal cleavage, by removing compounds having free amino groups or urea groups present in the carbamate crude mixture from the carbamate crude mixture by filtration of the carbamate crude mixture comprising the polyphenyl polymethylene polycarbamates over a solid acidic adsorbent in the presence of an acid dissolved in the carbamate crude mixture.