Transmetallation phosphorus

Exocyclic phosphorus of aminophosphinodiazaphosphole 122 on oxidation with trimethylsilyl azide gave (((trimethylsilyl)imino)phosphorano)diazaphosphole (124) the latter by transmetalation reaction with Cp TiCl3 at elevated temperatures yielded titanium iminophosphorane 125 (Scheme 36) [83],... 

Lithiated aromatics, generated by a transmetalation reaction, have been used for the generation of carbon-phosphorus bonds by displacement of chloride from phosphorus trichloride in the overall... 

Preparation of 4-cyanophenylzinc bromide by transmetallation and its reaction with phosphorus trichloride preparation of tris (4-cyanophenyl)phosphine-borane complex8... 

Rearrangement processes of alkyltitanocene dichlorides that occur under electron impact have been investigated using deuterium labelling. A novel type of zirconium-mediated coupling reaction of alkynes with vinyl bromide to afford 2,3-disubstituted dienes has been reported (see Scheme 105), and an inter-intramolecular reaction sequence has been proposed for the observed formation of vinylcyclohexadienes and/or methylenecycloheptadienes from the copper-catalysed reaction of zirconacyclo-pentadienes with allylic dichlorides. The essential step in these processes appears to be transmetallation of the zirconium-carbon bond of the zirconacyclopentadiene to produce a more reactive copper-carbon bond. New phosphorus heterocycles, e.g. (417), have been constructed by the thermal rearrangement of a [l,4-bis(trimethylsilyl)->/ -cyclooctatetraene]- ,3,5-triphospha-7-hafhanorbomadiene complex (416). 

Summary The reaction of two equivalents of lithium phosphinomethanides with di- or trifunctional chlorosilanes yields novel five- and six-membered heterocycles by multistep rearrangements or transmetallation reactions. Silaethene intermediates and hypervalent intermediates are likely to be involved. The reaction of one or two equivalents of lithium phosphinomethanide Li[C(PMe2)2(SiMe2Ph)] TMEDA with pTolSiCb and ci QHbcii iCb yields novel penta- and hexacoordinated silicon complexes. Both are the first examples of truly hypervalent organosilicon species with phosphorus donors characterized by X-ray structure determination. 

Transmetallation reactions between allyltin compounds and other Lewis acid metal halides (e.g. Bu2SnCl2, BCI3, BBr AICI3, or TiCU) are similarly very fast,39 and the reaction between allyltriphenyltin and BCI3 (though not BF3-OEt2) is complete within one second.40 Reactions of this type have been used for preparing allylic derivatives of boron,41,42 indium,10,38 copper 43 phosphorus, arsenic, antimony,44 and other metals. 

Unquestionably, the most attractive procedure for the preparation of dialkyl l-(trimethylsilyl)meth-ylphosphonates is the carbanionic route. The obvious transmetallation difficulties occurring when carbanionic reagents are employed in conjunction with activated methylene groups have led to the development of procedures based on the trapping of a-metallated phosphonates with chlorosilanes in the presence of lithium diisopropylamide (LDA) in excess. For example, the addition at -70°C of chlorotrimethylsilane (1 eq) to a solution of dialkyl 1-lithioalkylphosphonates prepared from dialkyl alkylphosphonates (1 eq) and LDA (2 eq) produces, after workup, dialkyl l-(trimethylsilyl)alkylphos-phonates in 75-90% yields of isolated product, via the quantitative and clean generation of stable dialkyl l-lithio-l-(trimethylsilyl)alkylphosphonates (Scheme Varying the phosphorus reac-... 

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