Lithium reagents, with phosphorus

In fact, lithium diphenylphosphide can be reacted in situ with alkyl halides to give phosphines. Obviously, this reaction could be a serious side reaction in mixtures obtained from lithium reagents and phosphorus trichloride in which residual lithium was present. It should be noted also that metalation of triphenylphosphine with butyllithium occurred at the meta position on one ring to a small extent (58). Consequently, in the condensation of phosphorus halides with lithium reagents prepared by an exchange reaction employing butyllithium, an excess of the latter could result in mixtures. 

When an aminophosphonium species is used with an aryl lithium reagent, cleavage of the amino functionality from phosphorus is observed, producing the parent phosphine.10 This reaction has been used to prepare stable phosphoranes from aminophosphonium species using dilithium reagents (Figure 5.6).10 It should be noted that the... 

Alkyl lithium reagents react with the hydridophosphazenes to generate phosphazeno anions [241]. These anions undergo facile reactions with non-metal halides or alkyl halides to produce phosphazenes with the phosphorus... 

Wittig-type olefinations can also be performed using selenoaldehydes. Phosphorus ylides initially attack the carbon atom of the selenocarbonyl functionality.405 Aromatic selenoketones undergo reductive dimerization with organo-lithium reagents probably via an electron transfer mechanism.406 Also the addition of organolithium reagents takes... 

Other types of leaving groups and of nucleophilic reagents also show greater reactivity at the 4-position 2,4-dichloropyrimidine with alcoholic potassium thiocyanate ° (to 304) and with chemical monodehalogenation (zinc and ammonia or ammonium chlor-ide), 2,4-(lH,3/f)-pyrimidinedithione with ammonia or amines to give 305, 2,4-(l/f,3 f)-pyrimidinedione thiona-tion o 8 o with phosphorus pentasulfide (of. 126 and 127), pyrimidine with phenyl lithium, and 2,4,6-trichloropyrimidine with several sulfanilamide anions. In the latter reaction, the absence of a... 

AnoAer procedure which was thought to pass through a mixed phosphorus anhydride was the acylation of Grignard reagents with an adduct formed between lithium carboxylates and triphenylphosphine dichloride (Scheme 26). The betaine (70) was the proposed tetrahedral intermediate however, since no evidence is provided, Ae reaction may have also proceeded by way of the acid chloride. Surprisingly, good yields of ketone are preserved even in the presence of excess nucleophile and no tertiary alcohol formation was observed. Triethylamine can be used for prior deprotonation of the carboxylic acid how-... 

III. Reactions of Pentavalent Phosphorus Halides with Grignard and Lithium Reagents... 

Phosphorus pentabromide and various trialkylphosphine dihalides should be examined for mode of reactivity with Grignard and lithium reagents. The rare pentavalent phosphorus compounds substituted with organofunctional groups appear to offer interesting structural considerations. The preliminary x-ray diagram of pentaphenylphosphorus was published recently (193). ... 

Tetravalent phosphorus halides are known to react with lithium reagents, but data is scarce. Aryllithium reagents easily displace chloride ion from phosphoryl chloride in the synthesis of tertiary phosphine oxides (143,144,174). A small quantity of the corresponding phosphinic acid (42) was isolated in the preparation of tris(p-dimethylamino-phenyl)phosphine oxide (43) (174). Choice of conditions and concentrations of reactants may well favor either the single or the double dis-... 

Although metalation of aliphatic carbon attached to phosphorus is well documented (85,173), only recently has it been noted that the carbon-phosphorus bond in triphenylphosphine oxide can be cleaved with an equimolar amount of methyllithium at room temperature (185). Indeed, benzene is produced along with a new lithium reagent which, when hydrolyzed, gives diphenylmethylphosphine oxide in high yield (83.5%). 

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