Diastereoselective Aldol Reaction of Zincated 3-Chloro-3-methyl-1-azaallylic Anions as Key Step in the Synthesis of 1,2,3,4-Tetrasubstituted 3-Chloroazetidines

Stereocontrolled Synthesis of Triols Containing Four Asymmetric Centers: Application of C, O-Chelated Germyl Enolates to a Diastereoselective Aldol Reaction

The treatment of α,β-unsaturated ketones with divalent germanium salts cleanly generated C, O-chelated germyl enolates. The aldol reactions of the chelated enolates with the aldehydes achieved a high diastereoselectivity in the construction of the five-membered aldol adducts. Furthermore, the subsequent transformation of the Ge-C bond in the aldol adduct enabled the stereocontrolled synthesis of triols bearing four asymmetric centers.

Recent advances in synthetic facets of immensely reactive azetidines

Recent developments in synthetic strategies towards functionalized azetidines along with their versatility as heterocyclic synthons.

Diastereoselective Mannich Reactions Using Fluorinated Ketones: Synthesis of Stereogenic Carbon-Fluorine Units

A diastereoselective Mannich reaction of simple α-fluoro ketones with N-tert-butylsulfinylimines was developed. This method provides a concise route to a variety of structurally diverse α-fluoro-β-amino ketones containing fluorinated stereogenic carbon centers; good yields and high diastereoselectivities were achieved. This method uses readily accessible starting materials and has a broad substrate scope: cyclic and linear α-fluoro ketones and fluoromethyl ketones are all suitable substrates.

Nucleophile-dependent regio- and stereoselective ring opening of 1-azoniabicyclo[3.1.0]hexane tosylate

1-[(1R)-(1-Phenylethyl)]-1-azoniabicyclo[3.1.0]hexane tosylate was generated as a stable bicyclic aziridinium salt from the corresponding 2-(3-hydroxypropyl)aziridine upon reaction with p-toluenesulfonyl anhydride. This bicyclic aziridinium ion was then treated with various nucleophiles including halides, azide, acetate, and cyanide in CH3CN to afford either piperidines or pyrrolidines through regio- and stereoselective ring opening, mediated by the characteristics of the applied nucleophile. On the basis of DFT calculations, ring-opening reactions under thermodynamic control yield piperidines, whereas reactions under kinetic control can yield both piperidines and pyrrolidines depending on the activation energies for both pathways.

Asymmetric synthesis of γ-chloro-α,β-diamino- and β,γ-aziridino-α-aminoacylpyrrolidines and -piperidines via stereoselective Mannich-type additions of N-(diphenylmethylene)glycinamides across α-chloro-N-sulfinylimines

The asymmetric synthesis of new chiral γ-chloro-α,β-diaminocarboxylamide derivatives by highly diastereoselective Mannich-type reactions of N-(diphenylmethylene)glycinamides across chiral α-chloro-N-p-toluenesulfinylaldimines was developed. The resulting (S_S,2S,3S)-γ-chloro-α,β-diaminocarboxylamides were formed with the opposite enantiotopic face selectivity as compared to the (S_S,2R,3R)-γ-chloro-α,β-diaminocarboxyl esters obtained via Mannich-type addition of analogous N-(diphenylmethylene)glycine esters across a chiral α-chloro-N-p-toluenesulfinylaldimine. Selective deprotection under different acidic reaction conditions and ring closure of the γ-chloro-α,β-diaminocarboxylamides was optimized, which resulted in N^α-deprotected syn-γ-chloro-α,β-diaminocarboxylamides, N-sulfinyl-β,γ-aziridino-α-aminocarboxylamide derivatives, a trans-imidazolidine, and an N^α,N^β-deprotected syn-γ-chloro-α,β-diaminocarboxylamide.