Chiral vicinal diamine

Optically active chiral vicinal diamines are produced by Sml2-promoted reductive coupling of an imine derived from benzaldehyde and l-isopropyl-2-methoxyethylamine. Intermolecular coupling proceeds in a diastereoselective... 

The imidazolinium salts, which are being used as ligand precursors, are generally prepared from C2-symmetric chiral vicinal diamines [43,44]. 

He and coworkers utilised catalyst 48e prepared from quinine and ben-zotriazole, which catalysed the aza-Henry reaction efficiently for a wide range of a-amidosulfones to give the desired products in good yields and with excellent enantioselectivities (up to 99% enantiomeric excess) and diaster-eoselectivities (up to 99 l). Compared with the N-benzyl catalyst 48d, the benzotriazole derivative of quinine 48e yielded the opposite enantiomer of p-nitroamines [(5 )-86, (S, J )-87a]. The practicability of this methodology was demonstrated by the conversion of the optically enriched aza-Henry products into chiral vicinal diamines or a-amino acids (Scheme 16.28). ... 

A wide number of chiral palladium complexes have been used in the context of DKR. In 1999, Cook et al. reported the palladium-mediated synthesis of chiral vicinal diamines from chiral oxazolidinones. The process involved successive oxidative insertion, loss of CO2 and subsequent cyclisation at the amide oxygen atom. The intermediate re-allyl palladium complexes underwent a rapid equilibration. Moreover, the intermediate oxazoline was also ionised by the palladium catalyst and was in equilibrium with the 7t-allylpalladium complexes, giving rise to thermodynamically controlled product ratios. These dynamic intermediates could be trapped with phthalimide under kinetic control to afford enantio- and diastereoselectively the corresponding syn-ch x 1,2-diamines (Scheme 2.46). 

Ma, Y, Liu, H., Chen, L., Cui, X., Zhu, J. and Deng, J., Asymmetric transfer hydrogenation of prochiral ketones in aqueous media with new water-soluble chiral vicinal diamine as hgand, Org. Lett., 2003,5,2103. 

Rondot, C., Zhu, J. (2005). Synthesis of chiral vicinal diamines by highly diastereose-lective three-component phenolic Mannich reaction temperature-dependent stereodivergency. Organic Letters, 7, 1641-1644. 

We identified an efficient DDQ-mediated CDC reaction between IV-phenyl THIQ and nitromethane that provides access to a number of rare chiral vicinal diamines [via 27d, Scheme 11.22). ° In the course of this work we observed NMR spectroscopic evidence for the long-supposed iminium ion and noted the precipitation of a solid in the reaction mixture which when isolated and then dissolved led to the reaction product. Subsequent focus on this solid using elemental analysis led to its suggested identity being 26c, where an iminium ion paired with the anion of the DDQ reaction product (the dihydroquinone) and this salt precipitated with another molecule of the protonated dihydroquinone (DDQHa). The solid was successfully... 

The authors then investigated the chiral vicinal diamine directly in the Michael addition for the synthesis of warfarin (Table 9.13). Importantly, the authors postulated that the diimine intermediate was an essential element for the high degree of asymmetric induction and concluded that the size of the... 

Iminium catalysis has been quite successful for asymmetric epoxidation of a,P-unsaturated carbonyl compounds, particularly, enals. Enones have remained difficult substrates. Recently, List and coworkers reported an enantioselective epoxidation of cyclic enones with either cinchona-based primary amine 38 or a counter-anion catalytic systan 149 combining a chiral vicinal diamine and a chiral phosphoric acid [69], High enantioseleclivities could be achieved in a number of cyclic enones (Scheme 5.40). 

Very recently, Kotsuki and coworkers reported an enantioselective Robinson annulation reaction for the synthesis of cyclohexenone derivatives bearing a quaternary center. Chiral vicinal diamine-chiral Bronsted acid conjugate 168 was found to be the optimal catalyst. The reactions afforded chiral cyclohexenone with moderate yields and good enantioselectivity [75], It was proposed that simultaneous enamine activation of donor and iminium activation of acceptor were involved in the catalytic cycle (Scheme 5.47). 

Syntheses and use of vicinal diamines with one or two N atoms included in heterocycle as chiral auxiliaries 98AG(E)2580. 

A diastereoselective synthesis of vicinal diamines has been described79. The aldehydes 56 derived from chiral amino acids 55 were converted into the A-benzylimines 57 and the latter were treated with organometallic reagents R2M in the presence of cerium(III)... 

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). 

By using glycine diphenylmethyl (Dpm) amide-derived Schiff base 22 as a key substrate and N-spiro chiral quaternary ammonium bromide lg as an ideal catalyst, a high enantioselectivity was achieved, even in the alkylation with less-reactive simple secondary alkyl halides, as shown in Table 5.5 [21]. This system offers a facile access to structurally diverse optically active vicinal diamines in combination with the subsequent reduction (Scheme 5.14) [21]. 

Finally, enantiomerically pure sulfinimines have also been used as precursors of chiral imidazolidines by 1,3-dipolar cycloaddition with azomethine ylids [181]. Reactions of different arylsulfinimines 245 with dipoles 246 are highly stereoselective, mainly affording diastereoisomer 247 (absolute configuration unequivocally established by X-ray studies), which was readily transformed into vicinal diamine 248 (Scheme 111). 

Scheme 5.17).40 A three-step reduction-deprotection protocol liberated the aratz -vicinal diamine 21. A six-membered cyclic transition-state structure was proposed to account for the anti selectivity after a two-electron reduction of the nitrone. The chiral A-tert-butylsulfinyl group directs the attack of the carban-ion to the Sz-face of the C=N double bond of the imine. 

Chiral C2-symmetric vicinal diamines have emerged as powerful tools for the synthesis of enantiomerically pure compounds and are now commonly used as chiral auxiliaries or ligands for a wide array of asymmetric chemical transformations, with efficiencies comparable to those obtained with the closely related... 

Utility. Many asymmetric syntheses have been developed using vicinal diamines as the source of chirality. The major interest lies in their use as precursors for the synthesis of a broad family of bidentate ligands. Many reactions have also been described using the N-alkyl derivatives of these diamines as chiral auxiliaries and protecting groups of aldehydes. Most of these applications generally use the framework of l,2-diphenyl-l,2-diaminoethane (7) or 1,2-diaminocyclohexane (8), whose preparations have been fully described. ... 

However, 1,2-diamino-l,2-di-(cr(-butylethane (3) holds particular interest because of its increased steric bulk and the absence of benzylic protons. Its recent ready availability should render it as attractive as the frequently used vicinal diamines 7 and 8. To our knowledge, only one application of this diamine has been previously described in the literature (eq 5), where the regio- and enantioselective epoxidation of conjugated aliphatic dienes were studied using the chiral manganese salen complex (9). 

Synthesis of Enantiomerically Pure C2-symmetric Vicinal Diamines via Chirality Transfer from DPEN. Several C2-sym-metric vicinal diamines and their derivatives are prepared in optically pure form by chirality transfer from DPEN. For example, condensation of (5, 5)-DPEN with butane-2,3-dione in benzene at the reflux temperature is followed by stereoselective reduction with NaBHsCN and PPTS at -20 °C to afford the (25,35,5R,6R)-piperazine 4 and its diastereomer in a 15 1 ratio (eq 12). The crude product is purified by silica gel column chromatography. Formation of the biscarbamate followed by reductive cleavage of benzylic C-N bonds with lithium in liquid ammonia, and then removal of isobutyloxycarbonyl with HBr in acetic acid results in (/ ,/ )-2,3-diaminobutane dihydrobromide 5 in 99% ee. 

Strukil V, Igrc MD, Eckert-Maksid M, FriScid T. Click mechanochemistry quantitative synthesis of ready to use chiral organocatalysts by efficient two-fold thiourea couphng to vicinal diamines. Chem Eur J 2012 18 8464-73. 

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