Base catalyzed cyclization of N-aryl and N-alkyl-O-propargyl carbamates to 4-alkylidene-2-oxazolidinones
- 作者：Ramapanicker Ramesh ; Yogesh Ch ; rasekaran ; Rajendran Megha ; Srinivasan Ch ; rasekaran
- 关键词：Carbamates ; Oxazolidinones ; Cyclization ; Solvent effects ; Chloroformates
- 刊名：Tetrahedron
- 出版年：2007
- 期刊代码：107_00404020
- 类别：ch
- 出版时间：10 September 2007
- 卷：63
- 期：37
- 页码：9153-9162
- 文件大小：1106 K
摘要
The base catalyzed cyclization of N-aryl and N-alkyl-O-propargyl carbamates is studied in detail. The effect of various bases and solvents on the efficacy of this cyclization reaction is analyzed and a new base–solvent system (LiOH in DMF) for effective cyclization of these carbamates is reported. A number of differentially substituted O-propargyl carbamates were cyclized to the corresponding 2-oxazolidinones under these conditions. The reaction conditions reported here are mild and no side reactions were observed in any of the substrates studied. A propargyl carbonate group was unaffected during the course of the cyclization of the O-propargyl carbamate group. The propargyl carbamates were prepared from the corresponding alkyl or aryl amines and the corresponding propargyl chloroformate, resulting in oxazolidinones diversely substituted at the nitrogen atom. N-Aryl-O-propargyl carbamates cyclized readily to the corresponding oxazolidinones with LiOH in DMF, whereas N-alkyl-O-propargyl carbamates reacted slowly under the same conditions. O-Propargyl carbamates substituted at the 1-position tend to cyclize faster whereas those substituted at 3-position cyclize considerably slower than the unsubstituted carbamates.