Developing The Chemistry Of 7-Phosphanorbornene Derivatives

The development of phosphorus heterocyclic chemistry was rapid in recent decades. The results showed that P-C heterocycles bear only a limited resemblance to their nitrogen analogues. Contrary to the quick development and intensive investigation of monocyclic P-C heterocyclics, such as phospholes and phosphinines, the chemistry of bicyclic phosphorus-carbon heterocyclics, such as 7-phosphanorbornenes, remained underdeveloped. Hence, this dissertation focuses on the chemistry of 7-phosphanorbornenes derivatives. Several new reactions based on the collapse of the phosphorus bridge of 7-phosphanorbornenes derivatives were discovered and developed.Some of the typical reactions and new developments of P-C heterocycles are summarized in chapter one.In the second chapter, we describe a novel and versatile synthetic equivalent sequence of nucleophilic phosphinidenes [RP] from 7-R-7-phosphanorbornenes (phosphole-N-phenylmaleimide cycloadducts) (Scheme 1). This synthetic equivalent sequence avoids the use of unstable phosphinidenes, but yields the same product as the one obtained in the reaction of phosphinidenes with identical reagents. The synthetic potential offered by this sequence also prompted us to investigate the synthesis of phosphines containing different substituents and secondary phosphine oxides. The different substituents in the target phosphines were introduced by three steps in different ways.The third chapter reports a novel phosphonium salt hydrolysis route based on the split of 7-phosphanorbornenium salt by the controlling the stability of reaction intermediates. This abnormal hydrolysis route gives a new, mild pathway to the synthesis secondary phosphine oxide.7-Phosphanorbornenium salt is rapidly hydrolyzed in the presence of triethylamine to give the classic phosphine oxide. When triethylamine is replaced by a-picoline, the reaction pathway changes completely, and the sole product is the secondary phosphine oxide (Scheme 3). These findings were rationally explained by our DFT calculations. A versatile and powerful route to functional secondary phosphine-borane complexes from 7-phosphanorbornenium salts was described in the fourth chapter. [BH4]- was used as soft nucleophile which attacks the positively charged phosphorus of 7-phosphanorbornenium salt and gives a pentacoordinate 7-phosphanorbornenium borohydride intermediate. This intermediate leads to the decomposition products: secondary phosphine borane complexes (Scheme 5). The huge synthetic potential of the resulting functional secondary phosphine borane complex was shown in preliminary.In the last chapter, we describe the photochemistry of several phosphanorbornene derivatives. The photochemistry of 7-phosphanorbornene sulfide shows solvent dependence. The product of the same reaction is completely different in different solvent due to a different mechanism. The first photochemistry method to prepare phosphindole derivatives was developed from the 3-methyl-1-phenylphosphole oxide dimer. The functionalizations of the preformed phosphindole ring were investigated in preliminary. A novel momophospha-cage compound was designed and prepared via intramolecular [2+2] cycloaddition reaction under the UV irradiation.