Desymmetrization of α-diimines: synthesis of new 3-(diaziridin-3-yl)oxaziridines

Water-controlled chiral inversion of a nitrogen atom during the synthesis of diaziridines from α-branched N,N'-dialkyl α-diimines

“…The first one could slow down the cyclization reaction as a consequence of the steric hindrance present in the anion intermediate II, which, stabilized by water solvation, undergoes rotation around the C-N single bond leading to the more stable isomers 3. These last compounds did not form when the reaction was performed either using only CH 2 Cl 2 as solvent 7 or starting from cyclic or unbranched N-alkyl substituted a-diimines, 8 in both cases lacking one of the two aforementioned effects.…”

“…For these N-protected bidiaziridines we observed, by means of ROESY NMR experiments, how both the alkylated nitrogen and the carbamic nitrogen showed a stable configuration. 7 More recently, a water-promoted desymmetrization reaction of a-diimines was successfully reported by us, 8 and starting from these preliminary results, reaction performed by using water as a co-solvent was extended to chiral a-diimines obtained by condensation reaction between glyoxal and differently branched amines with the aim of studying the possible influence of water on the stereochemical outcome of monoaziridination reactions.…”

New Trends in Diaziridine Formation and Transformation (a Review)

“…N,N-Disubstituted diaziridines 119 were also successfully synthesized by the reaction of trifluoromethyl imines 120 with NsONHCO 2 t-Bu, a carbamate, which is known to give amination reactions only by an ionic pathway involving the corresponding aza-anion (Scheme 8B). The advantage of using conventional methods for the synthesis of N,N-disubstituted diaziridines was also observed when synthesizing bidiaziridine 121 from α-diimines 122 [89]. A two-phase H 2 O/CH 2 Cl 2 system and the portion-wise addition of both amination agent and base (NsONHCO 2 Et and CaO) is considered to favor the formation of the monodiaziridine (E)-3-(iminomethyl)diaziridine-1-carboxylates 123, rather than its bidiaziridine 121 (Figure 16A).…”

“…A two-phase H 2 O/CH 2 Cl 2 system and the portion-wise addition of both amination agent and base (NsONHCO 2 Et and CaO) is considered to favor the formation of the monodiaziridine (E)-3-(iminomethyl)diaziridine-1-carboxylates 123, rather than its bidiaziridine 121 (Figure 16A). Further functionalization of this monodiaziridine, 123a,c,d, can be performed to obtain a hybrid compound containing an diaziridine and oxaziridine ring in one molecule of 3-(diaziridin-3-yl)oxaziridines 124 (Figure 16B) [89]. In line with the synthesis of the hybrid compound, a diastereoselective method for the synthesis of diaziridines with N-and/or C-cyclopropyl substituents (125 and/or 126) was developed [90] using the conventional methods.…”

Photocatalytic Generation of Nitrenes for Rapid Diaziridination

“…Diaziridines are frequently used as synthons for dipolar cycloadditions, ring expansions, alkylations, and the syntheses of carbenes and N-heterocycles . In addition to the early reports on diaziridines, modern syntheses are focused on hydroxylamine- O -sulfonic acid or ethyl nosyloxycarbamate mediated condensations of carbonyl compounds, amines, and ammonia/ N -chloramines to generate primarily the 1,3-disubstituted diaziridines and its analogues. Most of the reported methods are limited by very slow reaction rates, the necessity of specially designed precursors, metal catalysts, and costly reagents.…”