Study On The CO₂Insertion Reaction And Mechanism Of Chiral Bisamino Hydrospirophosphoranes With Second Amines

Pentacoordinate phosphorus compounds as a special type of oganic phosphoruscompounds have developed a new research field of bio-oganic phosphoruschemistry and drived the development of high coordinated oganic phosphoruschemistry including hexacoordinate phosphorus compounds. BisaminoHydrospirophosphorane includes two carbon chiral centers in addition to the centralphosphorus chiral centerand it is becoming one of the most suitable pentacoordinatephosphorane models to investigate thestereochemical characteristics of thehydrospirophosphoranes.Bisamino Hydrospirophosphorane is a new type ofpentacoordinate spirophosphorane model involving P–H bond, which is sufficientlyactive to be precursor for organic synthesis, such as the Atherton-Todd reaction. Anovel CO2insertion reaction into pentacoordinate P–N bond under mild conditionswas developed when the Atherton-Todd-type reaction of pentacoordinatehydrospirophosphoranes with amines was investigated.Therefore, in this thesis weuse the bisamino hydrospirophosphorane as the model to study the CO2insertionreaction with second amines and the reaction mechanism in this paper.By optimizingthe reaction conditions we synthesizedthe CO2insertion products in good yields anda serious of spirophosphorane carbamates compounds were obtained. Furthermore,the reaction mechanism was investigated and proposed.At first, the bisamino hydrospirophosphorane was synthesized from L-aminoacids, which is a pair of diastereoisomers. One of the hydrospirophosphoraneisomers with better solubility was selected to perform the CO2insertion reaction inthe CO2atmosphere.28new type of spirophosphorane carbamates compoundshavebeen synthesized in total, and their structures were confirmed by NMR、XRD、HRMS and IR. The CO2insertion reaction of different bisaminohydrospirophosphoranes with a series of second amines was explored. At the sametime, the mechanism and stereochemistry of the CO2insertion reaction wereinvestigated. Moreover, the rotation of N–C(=O) carbamate bond was investigatedby NMR spectroscopic experiments. The rotational barriers were determined usingdynamic NMR calculations and molecular mechanics calculations.In addition, thefragmentation pathways of spirophosphorane carbamates compoundswere studiedbyelectrospray ionization multistage mass spectrometry (ESI-MSn). The stereochemical characteristicand the reaction mechanism of the CO2insertion reaction were investigated.The results showed that thechlorinatedspirophosphorane intermediate was first generated with stereoretention of theconfiguration at phosphorus, and subsequently was attacked by a carbamate anionformed from CO2in base condition. It was found that rear attack of nucleophilicsubstitution with stereoinversion at phosphorus was the preferred route, althoughfront attack happened for sterically hindered reactants. The configuration of theinsertion product depended mainly upon the original phosphorus configuration ofthe hydrospirophosphoranes.The investigations of the CO2insertion reaction mightstep forward in the studies of the stereochemistry and other type reactionofpentacoordinate phosphorus compounds.