Cyclizations of β-Chloroethyl Substituted Ammonocarbonic Acids

Abstract

A consideration of carbamic acid, urea, and guanidine as mono-, di-, and tri-ammonocarbonic acids indicated that the cyclizations of their /3-chloroethyl derivatives might have some properties in common, so compounds of types (I), (II), and (III) were re-examined.In 1885, Nemirowsky (6) prepared N-phenyl /3-chloroethyl carbamate (I, R = phenyl) from /3-chloroethyl chlorocarbonate and aniline. He observed this carbamate to cyclize in alkaline solution to 3-phenyI-2-oxazolidone. This reaction was employed later by Otto (8) to prepare 3-a-napthyl-and 3-,8-napthyl-2oxazolidones. The new carbamates (I) and 2-oxazolidones prepared by these procedures are given in Tables I and II respectively. The cyclization of carbamates to 2-oxazolidones is explained by the participation of a carbonium ion intermediate.

The Chemistry of Chloroformates

“…Reaction of hydroxylamine with a chloroformate leads to N-acylation preferentially, viz. (292) pared by this route in the synthesis of 3-aryl-substituted 2-oxazolidones has been reported (5, 453). A similar cyclization has yielded cyclic ureas (738).…”

Novel Conformationally Constrained Analogues of Agomelatine as New Melatoninergic Ligands

“…N -acetylated derivatives 6a , b were derived from 2-(7-methoxynaphth-1-yl)acetonitrile by reduction of the nitrile group and reaction with the appropriate acyl chloride. Carbamate 6a was then cyclized by heating in an alkaline solution (NaOH) to afford the desired oxazolidinone 7a [ 39 ]. Compounds 6b and 7b were synthesized as previously described by us [ 40 ].…”

2-Oxazolidones

“…In Eq 39 the displacement occurs with nitrogen-alkyl cleavage (normally either R or Ri = H), and alkaline catalysts are usually present. A mechanism involving intermediate carbonium ions + RX has also been suggested (341) but does not appear as likely as the ones suggested.…”

“…As Table XXXI shows, yields are generally fairly good. A variety of bases have been used: alcoholic potassium hydroxide (279,380,420,531), aqueous potassium hydroxide (277,341), sodium hydroxide (23, 497), sodium ethoxide (116,119,120,122,123,367,395), sodium methoxide (163, 403), trimethylamine (117,366), triethylamine (492), diethylamine (396), potassium (459), and fused urea (318). Only two groups of workers (318,359) report alkaline cyclizations via oxygen-alkyl cleavage.…”