Studies On The Transformation Of P(O)-H Bonds And Its Applications In Organic Synthesis

P(O)-H compound, one of the most important organophosphorus compounds, via tautomeric rearrangement, it has trivalent and pentavalent phosphorus’s properties at the same time. Through the transformation of its activing P(O)-H bond, various of organic phosphorus-containing functional compounds which are widely used in medical drugs, agricultural productions, building materials, petrochemical and other areas, can be readily synthesized via addition, coupling, oxidation or reduction reactions. Thus the transformation of P(O)-H compounds attracts great attention.This paper focuses on applications of P(O)-H compounds in organic synthesis, including the synthesis of α-amino phosphonate and its derivatives, the synthesis of a-acyl phosphine oxide, the stereoselective reduction of gem-dibromides and the synthesis of tetranuclear Cu4P4complexes with R2P-O-PR2ligands. The contents and results are summarized as follows:1. Selective R-N bond (R=H or C) functionalization is achieved by simply combining an amine (primary, secondary, tertiary of alkyl or aryl amine), a>P(O)H compound (//-phosphonate,H-phosphinate or secondary phosphine oxide) and dihalomethane (Cl, Br or I substituted), a one-pot three-component coupling reaction takes place stereospecifically and selectively to afford the a-aminophosphorus compounds in high yields. Importantly, for the first time, by using this method, P-chiral aminophosphorus compounds were produced stereospecifically in high yield, which are difficult to be synthesized through other methods by employing the easily accessible optically pure P-chiral P(O)-H compounds as substrates. The absolute configuration at the phosphorus atom of the product was determined unambiguously by X-ray analysis, showing that this three-component coupling took place with retention of the configuration at phosphorus. The approaches described here obviously have significant advantages in terms of simplicity of experimental operation, convenience of products separation, mild reaction conditions and wide range of substrates, and would represent a general and efficient route for the synthesis of the important a-aminophosphorus compounds in high yields. Finaly, the mechanism of the reaction was studied, and the ease of R-N cleavage in the coupling reactions was summarized.2. Mediated by a simple base, a-acyloxyphosphoryl compounds are produced via a redox esterification of unsaturated aldehydes with P(O)-H compounds. Worth noting is that, compared to conventional procedures, this transformation also features high atom, step, and redox economic efficiency, and is applicable to prepare a wide range of a-acyloxyphosphoryl compounds. In addition, the mechanism of reaction was also investigated and described in detail, confirming that this redox strategy was a one-pot stepwise reaction for the synthesis a-acyloxyphosphoryl compounds.3. An efficient and highly stereoselective reduction of a gem-dibromides to the corresponding monobromides under mild reaction conditions was developed by using a combination of dimethyl phosphite and potassium carbonate. In addition to gem-dibromocyclopropanes, gem-dibromoalkyenes can also react efficiently and selectively under this system to give the corresponding monobromides in high yields. This reaction provided a simple and practical way for the synthesis of the valuable monobromocyclopropanes and (3-monobromoalkenes in high yield (up to96%isolated yield) with high selectivity (up to99/1cis/trans selectivity).4. By simply mixing R.2P(O)H with Cu(OAc)2in THF, an unique tetranuclear [(R2P)2O(CuOAc)2]2complex1was produced, in which R2P-O-PR2formally derived in situ from the dehydration of two secondary phosphine oxides.1is difficult to handle because it is extremely air sensitive and decomposes readily in air. However, after treatment of1with a chilled saturated aqueous NH4CI solution, a complex [(R2P)2O(CuCl)2]22was obtained via ligand exchange of the acetate group in1with the chloro anion of NH4CI. Contrary to complex1, complex2could be handled in air without decomposition, and could be easily separated by using a normal method with preparative GPC. The core structures of2vary with the R group.