1,2-Diamines aziridine ring

This methodology has also been employed for the preparation of tetradentate ligands by exchanging the primary amines for C2-symmetric primary diamines (eq 4). For example, from (/ ,/ -1,2-diamino-1,2-diphenylethane, diastereomeric ligand B was obtained in 84% yield. These aromatic amines are sufficiently reactive to open the aziridine ring. Due to steric hindrance, no further reaction of the secondary amine moieties with (5)-A -trifluoromethylsulfonyl-2-isopropylaziridine was observed. This tetradentate ligand was inferior to his(sulfonamides) as catalyst... 

In 2007, AntiUa and coworkers described the Brpnsted add-catalyzed desymmetrization of me yo-aziridines giving vicinal diamines [75]. hi recent years, chiral phosphoric acids have been widely recognized as powerful catalysts for the activation of imines. However, prior to this work, electrophiles other than imines or related substrates like enecarbamates or enamides have been omitted. In the presence of VAPOL-derived phosphoric acid catalyst (5)-16 (10 mol%) and azidotrimethylsilane as the nucleophile, aziridines 129 were converted into the corresponding ring-opened prodncts 130 in good yields and enantioselectivities (49-97%, 70-95% ee) (Scheme 53). 

Alternatively, the remaining sulfate ester of 70 may serve as a leaving group for a second nucleophilic displacement reaction. When this displacement is by an intramolecular nucleophile, a new ring is formed, as was first shown in the synthesis of a cyclopropane with malonate as the nucleophile [68] and of aziridines with amines as the nucleophiles [76]. The concept is further illustrated in the double displacement on (/J,/ )-stilbenediol cyclic sulfate (72) by benzamidine (73) to produce the chiral imidazoline 74 [79]. Conversion of the imidazoline (74) to (.V,.S )-stilbenediaminc 75 demonstrates an alternative route to optically active 1,2-diamines. Acylation of 75 with chloroacetyl chloride forms a bisamide, which, after reduction with diborane, is cyclized to the enantiomerically pure trans-2,3-diphenyl- 1,4-diazabicy-clo[2.2.2]octane (76) [81],... 

Extensive optimization studies identified highly electron-deficient 2,4-dinitrobenzyl-substituted aziridines as the most reactive substrates, chromium as the metal of choice, and indanol-derived Schiff bases as the most effective ligands. In this ring-opening process, catalyst 61 provided the highest selectivities. Using these optimized conditions, a variety of aziridines were selectively opened in a very efficient manner (Scheme 17.21).51 This reaction can provide an easy access to C2-symmetric 1,2-diamines, a valuable class of chiral auxiliaries, and even to less accessible non-C2-symmetric 1,2-diamines because of the differentially protected amines of the ring-opened products. 

Lew and Kim [66] recently synthesized a sulfide isostere of carbocyclic influenza neuraminidase inhibitor 268, moving from trityl protected aziridine 266, in turn prepared from (-)-quinic acid 159 (Scheme 43). Ring opening of 266 with 1-propanethiol promoted by BF3 etherate, followed by acetylation, gave sulfide 267 which was finally hydrogenated to diamine 268, in a good chemical yield. As the authors expected, mercapto-derivative 268 resulted to be a strong inhibitor of... 

This review covers the chemical literature on epoxides and aziridines for the year 2007. As in previous years, this review is not comprehensive but rather covers a selection of synthetically useful and interesting reactions. Three-membered ring systems, epoxides and aziridines in particular, are excellent synthetic intermediates. This is largely due to their ability to be converted into other functional groups such as diols, diamines, and amino alcohols to name but a few. The chapter has been divided into two sections, one covering epoxides and the other covering aziridines. Each of these sections has been further divided into two additional sections, one on the synthesis of the heterocycle and one on the reactions of the heterocycle. There is some overlap between methods for the synthesis of epoxides and aziridines and any overlap has been noted in the text. 

Diamines are another highly useful class of molecules with potent biological activity and use as synthetic intermediates and metal ligands. The ring-opening reactions of aziridines with amines and azide provides a facile route for the synthesis of 1,2-diamines. 

The synthesis of trans-1,2-diamines via the ring opening of aziridines has been reported to be catalyzed by Bids (10 mol%) in acetonitrile [87]. Interestingly, the use of Bi(0Tf)3 xH20 as a catalyst under the same conditions and solvent gave N-substituted P-amino nitriles instead [88]. 

A similar catalyst system was also effective for asymmetric ring opening of meso-aziridines with TMSN3. The reaction provided a direct method for the synthesis of optically active 1,2-diamines. In the reaction, bimetallic lanthanide... 

Bicyclic meso-N-ary aziridines are ring-opened by anilines, giving trans-1,2-diamines in the presence of a Ti(0-Bu-t)4/(l )-BlN0L catalyst in CH2Cl2." The reactions occur in yields between 65 and 96% with 57-99% ee. Lower enantioselectivities were found when electron-withdrawing and orifto-substituents were on the aniline. Alkyl amines failed to react. ESI-MS experiments indicate that the catalyst contains two titanium and two linked bis-BINOL ligands. 

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