Peiming Gu

Enantioselective preparation of cis-β-azidocyclopropane esters by cyclopropanation of azido alkenes using a chiral dirhodium catalyst.

A diastereo- and enantiocontrolled preparation of the conformationally restricted cis-β-azidocyclopropane esters have been developed. The Rh(2)(S-DOSP)(4) was found to be an efficient catalyst in hexane for the cyclopropanation of azido alkenes with diazo esters, and 19 cis-β-azidocyclopropane esters were prepared in excellent yields. The value of the diastereomer ratio was up to 99:1, and the enantiomeric excess was up to 95%. Furthermore, the relative and absolute configuration was confirmed by X-ray analysis.

A formal metal-free N-arylation via the Schmidt reaction of aromatic aldehydes with an azido amine.

A formal metal-free N-arylation of aromatic aldehydes with 3-azido-N-tosylpropan-1-amine through the Schmidt process was realized in the presence of acids. TfOH was found to be a good promoter, and the exclusive 1,2-aryl migration was observed. Furthermore, the conversion of an aliphatic aldehyde to the N,N-disubstituted formamide was achieved in excellent yield.

Intramolecular Schmidt reaction of acyl chlorides with alkyl azides: capture of N-acyliminium ion intermediates with aromatic rings.

Intramolecular Schmidt reaction of acyl chlorides with alkyl azides through N-acyliminium ion intermediates is designed and realized. The intramolecular capture of the intermediates with aromatic rings affords several nitrogen-containing tricyclic skeletons. The important feature of the domino process is the efficiency in bond reorganization and ring formation.

Tf2O-Promoted Intramolecular Schmidt Reaction of the ω-Azido Carboxylic Acids

A designed Tf2O-promoted intramolecular Schmidt reaction of 2-substituted ω-azido carboxylic acids was demonstrated. Tf2O was used as an activation reagent for the carboxylic acid, and ω-azido anhydride was in situ generated, releasing a molecular TfOH, which acted as an acid promoter for the Schmidt process. A series of 2-substituted pyrrolidines was produced and acetylated for better purification. The strategy was also efficient for conversion of a 4-substituted ω-azido carboxylic acid to the tricyclic lactam.

Correction to Catalytic Enantioselective Desymmetrization of 1,3-Diazido-2-propanol via Intramolecular Interception of Alkyl Azides with Diazo(aryl)acetates

The first catalytic enantioselective desymmetrization of 1,3-diazido-2-propanol via an intramolecular interception of alkyl azides by Cu–carbenoids has been realized. A wide range of 1,3-diazidoisopropyl diazo(aryl)acetates were converted to cyclic α-imino esters in the presence of bisoxazoline ligand (S,S)-Ph-Box with good to excellent yields, and the enantiomeric excess was up to 97%.