Reactions of several substituted 1H‐4,5‐dihydroimidazolium salts 1 with nucleophilic and electrophilic reducing agents acting via hydride transfer were explored. Reaction of compounds 1 with lithium aluminum hydride in THF afforded the corresponding imidazolidines 2. When alkaline borohydrides (sodium borohydride, potassium borohydride, sodium cyanoborohydride) in ethanol at room temperature were used, partial or total over‐reduction of compounds 2 leading to N,N,N'‐trisubstituted ethylenediamines took place on occasion. Results may be explained taking into account that reductive cleavage of 2 proceeds via a stabilized iminium ion present in protic solvents. Treatment of compounds 1 with an excess of borane in THF afforded the corresponding imidazolidines 2 or their borane complexes, according to the substituent type.

1H‐4,5‐Dihydroimidazolium salts 1 react readily with nucleophilic reagents originating cyclic products which may be stable or become transformed into acyclic compounds maintaining the structural ethylenediamine unit. With methylmagnesium iodide compound 1e affords the expected imidazolidine, but in the case of substituted 1‐aryl‐3‐methyl‐2‐phenyl salts 1b‐d the N‐aryl‐N′‐methylethylenediamines 3b‐d and acetophenone (4) were isolated, the process representing the transfer of the C‐2 unit to a nucleophilic carbon. With alkaline cyanides salts 1 react efficiently affording α,α‐diaminonitriles 5. In these compounds the cyano group may be readily substituted by nucleophiles (hydroxyl anion, species with nucleophilic carbon and reagents that act by hydride ion transfer), in a way similar to the salts but with better yields.

Nucleophilic Addition to Substituted 1H-4,5-Dihydroimidazolium Salts.-1H-4,5-Dihydroimidazolium salts (I), (IV) and (IX) react readily with nucleophilic reagents affording imidazolidines (III) and (X) or the further transformed acyclic compounds (V), (VIII) and (XII), still maintaining the ethylenediamine unit. -(SALERNO, A.; CERIANI, V.; PERILLO, I. A.; J. Heterocycl. Chem. 34 (1997) 3, 709-716; Dep. Quim. Org., Fac. Farm.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.