Base catalyzed cyclization of N-aryl and N-alkyl-O-propargyl carbamates to 4-alkylidene-2-oxazolidinones
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.
Dimethylsulfonium analogues of the muscarinic agent McN-A-343: [4-[[N-3 or 4-halophenyl)carbamoyl]oxy]-2-butynyl]dimethylsulfonium perchlorates
Some 3- and 4-bromophenyl and dimethylsulfonium analogues of the muscarinic agent [4-[[N-(3-chlorophenyl)-carbamoyl]oxy]-2-butynyl]trimethylammonium chloride (McN-Al-343) (1) were synthesized. The new compounds were assayed for effects on arterial blood p
Mellin,Vargas,Ringdahl
p. 1590 - 1593
(2007/10/02)
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