Fragmentation studies of pentacoordinated bisaminoacylspirophosphoranes by negative electrospray ionization mass spectrometry.
Fragmentation pathways of a series of pentacoordinated bisaminoacylspirophosphoranes were elucidated by electrospray ionization multistage mass spectrometry (ESI-MS(n)) in negative mode. The deprotonated ions of pentacoordinated bisaminoacylspirophosphoranes tend to eliminate a corresponding amino acid to form base peak. The hydrogen/deuterium exchange experiment, the high-resolution mass spectrometry, (13)C stable isotope labeling experiment and theoretical calculations were used to rationalize the proposed fragmentation pathways and to verify the differences between the fragmentation pathways. The results indicate that the negative molecular ions of pentacoordinated bisaminoacylspirophosphoranes dissociate through its open-chain tricoordinated tautomers. The relative Gibbs free energies (ΔG) of the product ions and proposed fragmentation pathways were estimated using the B3LYP/6-31 + + G(d, p) model. The results have some potential applications in the identification structures of similar spirophosphorane compounds by ESI-MS(n).
Synthesis and Characterization of Alkoxy Spirophosphoranes Prepared from Hydrospirophosphoranes and Sodium Alcoholates
The Atherton–Todd-type reaction of hydrospirophosphoranes (HSPs) and sodium alcoholates was investigated. Direct alkoxylation of HSPs was accomplished with sodium alcoholates in acetonitrile under nitrogen atmosphere. The stereochemistry mechanism of the alkoxidation of HSPs was proposed by the 31P NMR tracing experiment. The reaction proceeded via the chlorinated spirophosphorane intermediate with stereoretention of the configuration at phosphorus, followed by the rear and front attack of alkoxide anions to produce alkoxy spirophosphoranes. The reaction mechanism well explained the results of the reaction of HSPs with sodium alcoholates.
Structure et acidite de composes a atome de bore et de phosphore hypercoordonnes
La reaction de l'acide borique, en solution dans le DMF, avec des α-hydroxyacides, acides, le methyl-3-pyrocatechol, les acides oxalique, phenylhydroxamique, citrique et tartrique, conduit a des spirannes. Les borates de l'acide tartrique sont des derives dimeres comparables aux emetiques de l'antimoine. La structure spirannique a eteetablie au moyen de la RMN (11B, 13C, 1H). Dans le cas de l'acide acetonique, nous avons mis en evidence, en solution dans des solvants peu basiques (THF, CH3CN), un equilibre borane ⇌ borate spirannique. Le pKa de ces composes, determine par titration par la triethylamine, suivie par potentiometrie, correspond a des acides forts (1.5 < pKa < 2.5, dans le DMF, −2.5 < pKa < −0.3 dans le DMSO). Un pentaoxyspirophosphorane contenant deux ligands α-hydroxyacide et presentant un equilibre tautomere avec un compose a phosphore hexacoordonne, comparable a celui des spirannes de bore, a ete etudie par les memes techniques. Son pKa correspond encore a une acidite forte (pKa = 1.8 dans le DMF, −0.3 dans le DMSO). Dans les deux systemes, borates et phosphorane, le remplacement du ligand α-hydroxyacide par le ligand ethanediol, amene une baisse importante de l'acidite.