Phospholes and Phosphorins

The chemistry of phosphorins and related compounds has been critically reviewed.  

The 4-monosubstituted phosphabenzene (102) has been obtained from the corresponding 1,4-dihydrostannin by reaction with phosphorus tribromide. Phosphorins having one carbon- and one oxygen-linked substituent on phosphorus may be made directly by the reaction of phosphorins (103) with diazo-alkanes in the presence of alcohols or phenols.  

Anhydrous gold(i) chloride or iodide gave crystalline 1 1 complexes with 2,4,6-triphenylphosphabenzene in which the ring is attracted to gold via the lone-pair of electrons on the heteroatom. 

Eberlein, and H. Schmidbaur, Synth. Inorg. Metal-org- Chemistry, 1973, 3, 375. 

A comparative study of the photoelectron spectra of (106) and (107) indicates a similarity in the electronic effects produced by an rp hybridized carbon atom substituted by hydrogen and an sp phosphorus atom.  

Some highly substituted phospholium salts, e.g., (180), and phosphole oxides have been prepared by a ring-expansion reaction of aluminium chloride-cyclobutadiene complexes with dichlorophosphines. The [4 - - 2] dimer (181) 

1- phenylphosphindole (185). Cleavage of the exocyclic phenyl group occurs on treatment with lithium in THF to generate the phosphindolyl anion, which has a higher basicity and lower cyclic delocalization than related non-annelated phospholyl anions.  

2- position on treatment with t-butyl-lithium. The reactions of the metallated phosphole with electrophiles have been studied.  

Interest in the chemistry of diazaphosphole systems continues. 1,3,2-Diazaphos-pholes are formed in the reactions of diaminomaleonitrile with dialkylamino-phosphines and related halogenophosphines. A number of papers have 

Markl has continued to explore approaches to the synthesis of X - and X -phosphorins. The halogenofunctional X -systems, e.g., (189), figure prominently in this work. Thermal decomposition of compounds of this type lead to X -systems, e.g., (190). In solution in polar solvents the X -phosphorin 

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Phenyl derivatives of phosphole and phosphorin will react with alkali metals at low temperatures to produce radical anions which can be represented as Equation 13.206. As the temperature is raised, phenyl radicals are obtained. 

H. Bonnard, and Mathey, J. org. Chem., 1982, AT, 2376). The initial conversions of phospholes into phosphorins involve a number of stages, the first being the treatment of the phosphole with benzoyl chloride in ether in the presence of triethylamine, for example, the preparation of 4,5-dimethy1-2--phenylphosphorin (Mathey, loQ. ait. Tetrahedron Letters, 1978, 133 J.M. Alcaraz, A. Breque, and Mathey, ibid. 1982, 1565). 4,5-Dimethyl-2-pyridylphosphorin is prepared in a similar manner. For the conversion of 1-phenylphosphole to 2--phenylphosphorin and 3,4-dimethyl-1-phenylphosphole to 4,5--dimethyl-2-(furoyl or thenoyDphosphorin see Alcaraz,... 

Another A3-phosphorin synthesis from phospholes involves a 1,5-shift of the phenyl group of 1-phenylphosphole into the 2-position. 3,4-Dimethyl-l-phenylphosphole and 1,2,3-triphenylphosphole react with diphenylacetylene at 170 and 230 °C, respectively, in this manner (equation 66) (81TL4713, 81JA4595). 

The cycloaddition of phospholes with alkynes to synthesize phosphorins comes under this classification. For phosphorins to form, the transient 2H-phosphole has to react with alkynes followed by elimination of a carbene. This type of synthetic approach is less common and is discussed in the earlier chapter <1996CHEC-II(5)639>. 

The reaction between 1,2,5-triphenylphosphole (4) and tolane at 230°C affords 2,3,6-triphenylphosphorin (5), m.p. 150°, directly in a 80% yield, along with diphenylmethane, which is known to be one of the main products resulting from the formation of diphenylcarbene at high temperature (F. Mathey et at., Ainer. chem. Soc., 1981, 103, 4595). This one-step synthesis of a phosphorin from a phosphole offers numerous possibilities and supplements earlier procedures (Markl, Phosphorus Sulphur, 1977, 3, 77 Ashe, Acc. chem. Res., 1978, 11, 153 Mathey, Tetrahedron Letters, 1979, 1753). 

Greater interest has, however, been directed towards unsaturated ring systems. Phosphorins, phospholes, phospholenes, phosphetes, phosphirenes and so forth (Chapters 6.20 through 6.22). These are all capable of forming metal complexes of one kind or another. 

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