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Rearrangement of 2-aryl-3,3-dichloroazetidines: Intermediacy of 2-azetines
Dejaegher, Yves,Mangelinckx, Sven,De Kimpe, Norbert
, p. 2075 - 2081 (2007/10/03)
An easy synthesis of 2-aryl-3,3-dichloroazetidines, a rather unexplored class of azaheterocycles, is described. The title compounds were easily obtained by reduction of the corresponding 4-aryl-3,3-dichloro-2-azetidinones with monochloroalane, which in turn were synthesized by a ketene-imine [2 + 2] cycloaddition. The reactivity of 3,3-dichloroazetidines with bases was investigated, yielding 2-[dimethoxy(aryl)methyl]aziridines by ring contraction when treated with sodium methoxide. Furthermore, reacting the 3,3-dichloroazetidines with sodium hydride in DMSO, followed by aqueous workup, afforded 1-alkyl-2-aroylaziridines, by hydrolysis of the intermediate 2-azetines and ring closure of the transient 3-amino-2-chloro-1-phenyl-1-propanone derivatives. Monitoring this reaction in an NMR tube, using sodium hydride in DMSO-d6, allowed the characterization of the intermediate strained heterocyclic enamines, i.e., 2-azetines, by 1H and 13C NMR.
