A Facile And Efficient Synthesis Of Diethyl α,α-Dihalogenomethanephosphonates

a-Functionalized phosphonates have attracted considerable attention in the field of biology, pharmacology and organic chemistry. In particular, a-halogenated phosphonates, which are widely utilized as synthetic reagents and especially as good precursors for the synthesis of symmetrical or unsymmetrical a-halogenoalkenes and alkynes in mild conditions by the Wittig-Horner reaction, are fascinating organophosphorus compounds. Moreover, the a-monohalogenated and a,a-dihalogenated phosphonates are often designed as phosphate mimics to be used as enzyme inhibitors and metabolite probes due to their structural and electronic similarities to the parent phosphate groups. A number of methods for the introduction of a halogen and two same halogens at the a-CH2 position of phosphonates by the nucleophilic and electrophilic halogenations have been reported. In this thesis, We have demonstrated that a variety of a,a-difluorobenzylphosphonates and a,a-chlorofluoroalkanephosphonates can be readily prepared via a two-step halogenation procedure, and the synthesis of isoquinuclidine by the one-pot, three-component aza[4+2] reaction can be catalyzed by NFSI.1. We have developed a general, versatile and unambiguous approach for the preparation of a,a-difluorobenzylphosphonates in good yields via a two-step halogenation procedure. First step was nucleophilic fluorination of a-hydroxyphosphonates with DAST, second step was electrophilic fluorination with N-fluorobenzenesulfonimide (NFSI). The experimental conditions offer a more efficient and convenient preparation than those early reported, each step of this reaction sequence being executed in good yields. These compounds could be as potential inhibitor of PTPs.2. We have developed an efficient and practical approach for the preparation of a,a-chlorofluoroalkanephosphonates from a-hydroxyphosphonates by a two-step procedure. First step was nucleophilic chlorination of a-hydroxyphosphonates with PPh3 and CCl4, second step was electrophilic fluorination with NFSI. These compounds could be as potential inhibitor of PTPs and could be converted into various useful quaternary carbon-containing a-fluorophosphonates by using nucleophilic substitution. 3. We have successfully developed a convenient, effective and mild strategy for the synthesis of isoquinuclidine derivatives by the one-pot, three-component aza[4+2] reaction of cyclohexenone with a number of aromatic aldehydes and amine catalyzed by NFSI. The reactions generated the desired products in good yields at room temperature with acceptable stereoselectivity in air. The present method avoids using metals and complex molecules obtained by multistep synthesis, and instead it employs user-friendly and commercially available catalyst NFSI. In addition, the reaction may expand the scope of N-F electrophilic fluorinating agents as versatile tool in organic synthesis.