Methylene phosphorane

Methylene phosphorane derivatives, Scheme 23, react with Se to give the corresponding selenoketones.18,24,223 225... 

A further example of the diazaphosphole synthesis by [3 + 2] cycloaddition is given by the reaction of a phosphoranediyl diazomethane (26) (R = NPr j) with P-chloro-bis(trimethylsilyl)-phosphaethene. The adduct loses trimethylchlorosilane and yields a 3-phosphoranediyl-l,2,4-diazaphosphole (or 3-phosphonio-l,2,4-diazaphospholide) (27). The analogous addition to the trimethylsilyl substituted P-chloro-bis(methylene)phosphorane (28) yields a 4-methylene derivative (29) of this diazaphosphole (molecular structure in Table 1). It provides the only fully characterized example of this type up to 1995. Methyl triflate methylates the compound at N-1 and gives a phosphonio methylene diazaphosphole cation (30). 

Vinyl ethers have also been prepared by addition of alkoxides to acetylene,6 7 6 elimination from halo ethers and related precursors,6 8 and vinyl exchange reactions.6 Reaction of an electrophilic tungsten carbenoid with methylene phosphorane or diazomethane also produces vinyl ethers.9 Enol ethers have resulted from the reaction of some tantalum and niobium carbenoids with esters,10 and the reaction of phosphoranes with electrophilic esters.4... 

Scheme 5 Bis-methylene-phosphorane-type bonding with the usual notations and resonance structures...

Scheme 6 Possible participation of bis-methylene-phosphorane-type bonding in Ji-systems...

Like ylides, bis-methylene-phosphoranes can also be built into 7i-systems in different ways (see Scheme 6), with one of the P=E bonds in an exocyclic position, or with the entire 3c-4e 7i-system incorporated into the cyclic delocalization. 

Die Umsetzung eines acylierten Diphenyl-ethoxy-methylen-phosphorans mit Benzyl-bromid liefert in quantitativer Ausbeute einen phosphorylierten Enolether, vermutlich iiber eine Alkoxyphosphoniumsalz-Zwischenstufe, die nach Art der Michaelis-Arbu-sov-Reaktion desalkyliert wird389 ... 

Alkyl-diphenyl-phosphanoxide mit weiteren Acceptorsubstituenten am Alkyl-Rest lassen sich in Methylen-phosphorane umwandeln. So liefert z.B. das aus Bis-[diphenylphos-phinyl]-methan und Natriumhydrid in Dimethylsulfoxid erhaltliche Carbanion bei der Alkylierung mit Alkylbromiden nicht das zu erwartende Kohlenstoffalkylierungspro-dukt (s. Bd. XII/1, S. 164), sondern ein Alkoxy-diphenyl-(diphenyIphosphinyl-methylen )-phosphoran 459. 

In the following example (Eq. 7) P—QH means styrene polymer where a di-ethylaminoethynyl moiety is built up via a formylation, Wittig reaction with dichloro-methylene phosphorane and elimination-substitution steps. This polymer-bound ynamine is till now unique 18). 

The Wittig reaction involves the interaction of an oxo compound (an aldehyde or ketone) (1) with phosphonium ylides [substituted methylene phosphoranes (2a,b)], through an intermediate betaine (3), to yield the appropriate alkene (4) and triphenylphosphine oxide (5), as shown in equation 1. 

Reaction of chlorobis(methylene)phosphorane 55 with K[(i73-C3H5)Fe(CO)3] in a mixture of THF and toluene gives the metallobis(meth-ylene)phosphorane 56 and the bis(methylene)propenylphosphorane 57 as major products. The dihydrophosphole complex 58 is obtained as a minor product (<10% yield) (Scheme 13).40 In contrast, treatment of 55 with K[Fe(CO)2Cp] gives rise to the formation of the metallobis(methylene) phosphorane 59 (39% yield) and the phosphaferrocene 60 (34-72% yield, dependent upon the reaction time). The phosphole ligand of 60 is con-... 

Metallobis(methylene)phosphorane, synthesis with phosphaalkenes, 19-20... 

The bis(methylene)phosphoranes hold two carbon atoms doubly bonded to the same phosphorus atom. The molecule is chiral in the solid state due to the propeller-like orientation of the silyl groups as demonstrated in Fig. 2. 

The deprotonation of amino-bis(methylene)phosphoranes leads to imino-bis(methylene) phosphate anions, which show one PN and two PC double bonds [Eq. (11)] (50a). 

It was soon realized that the far more readily available 1-chloro and bromo acetylenes could be used too and in fact phenylchloroacetylene gives with lithium dimethylamide in ether, 87 % of the corresponding ynamine Similarly, N-lithium pyrroline affords 67 % of the corresponding ynamine In the following example (Eq. 7) P—CgH4 means styrene polymer where a di-ethylaminoethynyl moiety is built up via a formylation, Wittig reaction with dichloro-methylene phosphorane and elimination-substitution steps. This polymer-bound ynamine is till now unique... 

The availability of phosphaalkenes led to a second route to phosphiranes with diazoalkanes as cycloaddition partners compare with Scheme 14. The first formed 4,5-dihydro-3//-l,2,4-diazaphospholes 43 decompose under the influence of light and extrusion of nitrogen to form the bis(methylene) phosphoranes 44, which cyclize in a 47t-electro-cyclic closure to the phosphiranes 45 (Scheme 17) <1996CHEC-II(I)298>. For the theoretical background, see Section 1.08.2.1.1, and for analogous reactions see <1995CC25> and <1997CB779>. 

Although strictly outside the remit of this chapter, it is appropriate to note continued activity in the chemistry of c X -p -bonded phosphorus compounds that do not possess a lone pair of electrons at phosphorus. A monomeric metaphosphonate species (262, X=0) has been stabilised by coordination via the P=0 bond), and Harger s group has provided evidence of the intermediacy of metathiophosphonates (262, X=S) in the reactions of phosphonami-dothioic acids with alcohols.The cation (263) has been stabilised by coordination at phosphorus with 4-dimethylaminopyridine and the reactivity of bis(methylene)phosphoranes (264) and related phosphoranylidene car-benoids has been investigated. ... 

A. BIS[ TRIMETHYL(METHYLENE)PHOSPHORANE] MERCURY DICHLORIDE (Bis(trimethylphosphoniuni methylide)mercury Dichloride)... 

The format of this chapter is similar to that used in previous volumes. The first section deals with methylene phosphoranes and their Wittig reactions, the second looks at the Horner-Wadsworth-Emmons reaction of phosphonate anions and the third the structure and reaction of lithiated phosphine oxides - an area which continues to receive particular attention. The majority of reports concerning ylides relate to their use in synthesis and in the final section some of these applications are reviewed. 

High-spin cation radicals 2 and 3 can be obtained by oxidation of the parent methylene phosphoranes. Dication radical 2 has a triplet state as evidenced from a AMs = 2 ESR transition exhibiting hyperfine coupling to two identical phosphorus nuclei. The trication radical 3 possesses a quartet state with D - 262 MHz and E = 0 MHz and exhibits a AA/s = 3 ESR transition. The archetypal methylene phosphorane H3P CH2 has been investigated in the gas phase using ion cyclotron resonance mass spectrometry. ... 

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