Formation Of Organophosphorus Compounds Via P-C Bond Cleavage

The 7-phosphanorbornenes are easily obtained by cycloaddition of dienophiles such as N-phenylmaleimide or maleic anhydride or acrylonitril or dimethyl acetylenedicarboxylate with phospholes or their derivatives, or synthesis by dimerized of phosphole derivatives. The 7-R-7-phosphanorbornenes can be functionalized by oxidation, sulfuration, coordination, quaternary, and R can be introduced by using phospholide ions react with organic functional groups. These bicyclic phosphorus-carbon heterocyclics have strong strains; they are easily collapsed of the phosphorus bridges to decompose to phosphinidene or its derivatives. Methods of synthesis of useful organophosphorus compounds via this kind of P-C bond cleavage were discussed in this thesis.Synthesis, characteristic, reactions and application of 7-phosphanorbornenes are summarized in the first chapter.In the second chapter, a non-conventional synthesis of dibromophosphines by P-C bond cleavage was introduced. Dibromophosphines are versatile synthetic intermediates in organophosphorus chemistry. However, only a restricted number of methods are available in the literature for their preparation and most of them are not compatible with a wide range of functional groups on the R substituent. In our research, dibromophosphines RPBr2 are obtained by reaction of tetrabromomethane with-7-phosphanorbornenes in toluene at ca. 100 oC and the the proposed reaction mechanism was discussed. The reactions were monitored by 31 P NMR spectroscopy. The rate of the reaction sharply varied according to the nature of the substituent at phosphorus(completion needed between 10 min and 4 h). The 7-phosphanorbornenes are obtained in situ by cycloaddition of N-phenylmaleimide with 1-R-3, 4-dimethylphospholes. The overall reaction sequence shows a good compatibility with functional groups. The dibromophosphine was characterized by its 31P NMR resonance and by complexation with tungsten pentacarbonyl or by reaction with diethylamine and sulfur.In the third chapter, a new mild synthetic method of dichlorophosphines and its application in synthesis of 6-methoxy-5-phosphaphenanthrene were discussed. Theoretical analysis and experimental research about the reactivity of 6-methoxy-5-phosphaphenanthrene were carried out. On the basis of last chapter, Dichlorophosphines RPCl2 are obtained by reaction of(COCl)2 with 7-phosphanorbornenes in toluene at room temperature and monitored by 31 P NMR spectroscopy. The overall reaction sequence shows a very good compatibility with functional groups and the yields much higher than that of dibromophosphines. This method can be widely applied to synthesize dichlorophosphines. Using a special 7-phosphanorbornene which contains methoxy-, reacted with oxalyl choride then gave a cyclic chlorophosphine, whose structure was established by X-ray crystal analysis of its P-W(CO)5 complex. 6-methoxy-5-phosphaphenanthrene was obtained from the cyclic chlorophosphine by dehydrochlorination with 1, 4-diazabicyclo [2.2.2] octane. It was characterized by 31 P NMR, 1H NMR, 13 C NMR and HRMS and the structure was confirmed by the X-ray crystal analysis of the P-W(CO)5 complex also. The low reacticity and the planar structure of 6-methoxy-5-phosphaphenanthrene suggest that it could be used as conjugated materials for optoelectronic applications or as a ligand in homogeneous catalysis.In the fourth chapter, the reaction of triethylamine with the [4+2] cycloadducts of phosphole sulfides and 3-bromo-N-phenylmaleimide provides a convenient access under very mild conditions to phosphinidene sulfides [RP=S]. And this new kind of [4+2] cycloadducts 7-phosphanorbornenes can be easily eliminated HBr to 7-phosphanorbornadienes. This reaction will give a new direction on the research of 7-phosphanorbornenes. The [RP=S] transient species are trapped by 2, 3-dimethyl-1, 3-butadiene to give the previously unknown trivalent [4+2] cycloadducts. One of these(R = Ph) has been characterized as its P-W(CO)5 complex by X-ray crystal structure analysis. With cyclopentadiene, the subsequent insertion of a second molecule of [RP=S] leads to a new type of bicyclic product containing a P-P-S ring.