Electrophilic α-amination of carbonyl compounds

Highly enantioselective synthesis of 3-amino-2-oxindole derivatives: catalytic asymmetric alpha-amination of 3-substituted 2-oxindoles with a chiral scandium complex

A highly enantioselective alpha-amination of 3-substituted oxindoles with azodicarboxylates catalyzed by a chiral Sc(OTf)(3)/N,N'-dioxide complex (Tf: triflate) has been developed and affords the corresponding 3-amino-2-oxindole derivatives in high yields (up to 98%) with excellent enantioselectivities (up to 99% ee). The procedure is capable of tolerating a relatively wide range of substrates, and excellent results (92-96% ee) can also be obtained, even in the presence of 0.5 mol % of catalyst loading under mild conditions. These results showed the potential value of the catalytic approach. Moreover, with high synthetic versatility, the product could be easily transformed into optically active 3-amino-3-methyloxindole bearing a chiral quaternary stereogenic center.

Enantioselective alpha-amination of 1,3-dicarbonyl compounds using squaramide derivatives as hydrogen bonding catalysts

Catalytic enantioselective alpha-hydrazination of 1,3-dicarbonyl compounds with azodicarboxylates was investigated in the presence of our newly developed hydrogen bonding catalyst, squaramide 3j. High yields and high enantioselectivities were achieved with low catalyst loading under mild conditions.

Expanding the scope of cinchona alkaloid-catalyzed enantioselective alpha-aminations of oxindoles: a versatile approach to optically active 3-amino-2-oxindole derivatives

A cinchona alkaloid-catalyzed, highly enantioselective, alpha-amination of oxindoles has been developed. The reaction is general, operationally simple, and affords the desired products in high yields with good to excellent enantioselectivity. Significantly, this study provides a general catalytic method for the construction of a C-N bond at the C3 position of oxindoles as well as for the creation of a nitrogen-containing, tetrasubstituted chiral center.

Managing highly coordinative substrates in asymmetric catalysis: a catalytic asymmetric amination with a lanthanum-based ternary catalyst

Full details of a catalytic asymmetric amination with a lanthanum/amide-based ligand catalyst system are described. A catalyst comprising La(NO(3))(3)*6H(2)O, (R)-3a and H-d-Val-O(t)Bu was identified to promote the catalytic asymmetric amination of nonprotected succinimide derivative 1 with as little as 1 mol % catalyst loading. Mechanistic studies by various spectroscopic analyses and several control and kinetic experiments suggested that the catalyst components were in equilibrium between the associated and dissociated forms, and that the reaction likely proceeded through a La(NO(3))(3)*6H(2)O/(R)-3a/H-d-Val-O(t)Bu ternary complex. This catalyst system was also effective for asymmetric amination of N-nonsubstituted alpha-alkoxycarbonyl amides 7, hitherto unprecedented substrates in asymmetric catalysis, probably due to their attenuated reactivity and difficult stereocontrol, affording the amination products in up to >99% yield and >99% ee. The high catalytic performance and enantiocontrol of the reaction with highly coordinative substrates were achieved by the activation/recognition of the substrates exerted by coordination to lanthanum and hydrogen bonding cooperatively in the transition state.

Recent Progress on the Stereoselective Synthesis of Cyclic Quaternary alpha-Amino Acids

The most recent papers describing the stereoselective synthesis of cyclic quaternary alpha-amino acids are collected in this review. The diverse synthetic approaches are classified according to the size of the ring and taking into account the bond that is formed to complete the quaternary skeleton.

Amination of heterocyclic compounds with o-benzoylhydroxylamine derivatives

The N-amination of heterocyclic compounds 1a-k with O-benzoylhydroxylamine derivatives 5 was developed and demonstrated to be a superior alternative to existing N-amination methods. A structure-reactivity relationship study was performed on variously substituted O-benzoylhydroxylamine derivatives, leading to the discovery of the novel and more efficient aminating reagents 5h and 5i.

Organic azides: an exploding diversity of a unique class of compounds

Since the discovery of organic azides by Peter Griess more than 140 years ago, numerous syntheses of these energy-rich molecules have been developed. In more recent times in particular, completely new perspectives have been developed for their use in peptide chemistry, combinatorial chemistry, and heterocyclic synthesis. Organic azides have assumed an important position at the interface between chemistry, biology, medicine, and materials science. In this Review, the fundamental characteristics of azide chemistry and current developments are presented. The focus will be placed on cycloadditions (Huisgen reaction), aza ylide chemistry, and the synthesis of heterocycles. Further reactions such as the aza-Wittig reaction, the Sundberg rearrangement, the Staudinger ligation, the Boyer and Boyer-Aubé rearrangements, the Curtius rearrangement, the Schmidt rearrangement, and the Hemetsberger rearrangement bear witness to the versatility of modern azide chemistry.

Copper-catalyzed electrophilic amination of organozinc nucleophiles: documentation of O-benzoyl hydroxylamines as broadly useful R2N(+) and RHN(+) synthons

[reaction: see text] This paper details new copper-catalyzed electrophilic amination reactions of diorganozinc reagents using O-benzoyl hydroxylamines as electrophilic nitrogen sources that may be accessed in one step. Simple and functionalized aryl, heteroaryl-, benzyl, n-alkyl, sec-alkyl, and tert-alkyl nucleophiles couple with R2NOC(O)Ph and RHNOC(O)Ph reagents in the presence of catalytic quantities of copper salts to provide tertiary and secondary amines, respectively, in generally good yields. In many cases, the product may be isolated analytically pure after a simple extractive workup. The amination process is shown to tolerate a significant degree of steric demand. The amination of nominally unreactive C(aryl)-H bonds via a sequential directed ortho metalation/transmetalation/catalytic amination reaction sequence is detailed. The direct Cu-catalyzed amination of Grignard reagents using cocatalysis by ZnCl2 is described.