Reaction with phosphorus carbene

As the phosphonium diylides, lithium phosphonium yldiides, first described by Schlosser and Corey (Ph3P=CR-Li R=H, C3H7) [60-62], have a high nucleophilicity and reactivity. Recently, the a-silylated lithium phosphonium yldiide 20 has been prepared from the stable phosphanyl-(silyl)carbene 19 and alkyl-lithium (Scheme 13). The first crystal X-ray diffraction study of such a reagent was proposed for 20 and its reaction with methyl iodide or phosphorus elec-... 

The reactions of dichlorocarbene with phosphorus ylides result in the corresponding olefins and phosphines.66-68 In the reaction of dichlorocarbene generated in situ with tributyl- and triphenylmethylenephosphoranes or triphenylethylidenephosphorane, the olefin yield increases as the nucleo-philicity of phosphorus ylide increases. According to,67 the reaction starts from the electrophilic attack of carbene at the a-C atom of phosphorus ylide. Then the intermediately formed betaine (28) (Scheme 14) decomposes to eliminate the phosphine molecule and form dichloroolefin (29). 

The thermodynamic data presented in Table XYI are calculated for the temperature T=0K. Note that the entropy factor favors betaine decomposition via directions A and B at higher temperatures. The reactions of organoelement analogs of carbenes with phosphorus and arsenic ylides are yet poorly studied. The presented above results of calculations allow an optimistic prognosis about the possibility of developing a new method for the synthesis of elementaolefins R2E14=CH2 (E14 = Si, Ge, Sn) on the basis of these reactions. 

We theoretically studied the reactions of stable West silylenes 32 and 73 with phosphorus ylide H2C=PMe3.74 Similarly to the simplest analogs of carbenes, these compounds can form betaines in which the negative charge is localized on the silicon atom and the positive charge is localized on the phosphorus atom. These betaines can thermally decompose to form silenes (direction A, Scheme 39) or be isomerized to ylides via direction B. 

The reaction of triplet carbenes with a persistent nitroxide such as 2,2,6,6-tetra-methylpiperidine A -oxide (TEMPO, 84) to form benzophenone would be spin allowed and >100-kcal/mol exothermic (Scheme 9.26). The reaction has a few parallels in free radical chemistry, such as the reaction of tert-butoxyl with carbon monoxide (to yield CO2) or with phosphorus (111) substrates to yield P(V) products. " ... 

Alkoxide anion abstraction by a Lewis acid from phosphorus ligand on a transition metal is one of the most useful methods to prepare cationic phosphenium complexes. It has been reported that OR anion abstraction from an alkoxyalkyl ligand, C(OR)R2, on a transition metal complex leads to the formation of a cationic carbene complex.39-42 It is similarly expected that OR anion abstraction from an alkoxysilyl ligand, Si(OR)R2, would cause the formation of a cationic silylene complex. Therefore, increased attention has been focused on the reaction with a Lewis acid of transition metal complexes bearing both alkoxyalkyl and phosphite ligands and of complexes bearing both alkoxysilyl and phosphite ligands. 

An aminophosphinidene complex Cp Os(CO)2 PCl(N-Tr2) was prepared by reaction of [Cp Os(CO)2] with Tr2NPCl2. As with Fischer carbenes (see Fischer-type Carbene Complexes), the nitrogen group stabilizes the electron-deficient phosphorus atom of the phosphinidene ligand. Based on a crystal structure of the ruthenium analog, there is likely... 

The reactions of P-halophospha-alkenes with carbenes provide a new route to 1-chloro-lH-phosphirines (181). Such compounds are highly reactive, and a study of nucleophilic displacement reactions at phosphorus has been facilitated by preparation of the related P-W(CO)5 complexes.The first pentacoordinate systems derived from phosphirenes, (182), have been formed in the reactions of P-halo- or P-cyano-phosphirenes with tetrachloro-o-quinone. Evidence has been presented for the rearrangement of P-chlorophosphirenium ions (183) to the vinylphosphenium ions (184)... 

Other direct syntheses of halide free ionic liquids can be categorized into three groups (1) synthesis via N-heterocyclic carbene intermediates, (2) phosphorus based direct reactions with imidazoles and (3) sulfur-based direct reactions with imidazoles as discussed further below. 

A large variety of codimerization reactions under the catalytic action of copper complexes is known. Usually, these reactions proceed via carbene intermediates and provide substituted ethenylcyclopropanes. Most of the catalysts for these reactions consist of copper(I) chloride and a phosphorus ligand, such as triphenylphosphane or triphenyl phosphite. Under the influence of these catalysts, carbenes are presumably formed from various substituted cyclopropenes at temperatures ranging from —40 to - -20°C, and these carbenes can be trapped by reaction with alkenes. ... 

Fused cyclopropanes are obtained by intramolecular cyclopropanations or by intermolecular reactions with cyclic alkenes or aromatic derivatives. The phosphoryl carbenes are the only phosphorus-substituted carbenes used in these reactions. 

Khaskin, B.A., Molodova, O.D., and Torgasheva, N.A., Reactions of phosphorus-containing compounds with diazo-compounds and carbenes, Usp. Khim., 61, 564, 1992 Russ. Chem. Rev., 61, 306, 1992. 

The ease of insertion of an acylmethylene group (derived as the carbene from a diazoketone) is dependent on the nature of the bonding at tetracoordinate quinquevalent phosphorus. Thus, insertion is accompanied by rearrangement during reactions with... 

Addition reactions of low coordinate phosphorus compounds have proved to be an interesting route to novel acyclic phosphazenes. Phosphino carbenes, R2PCSiMej, exhibit typical multiple bond behavior in 2+3 cycloaddition reactions with trimethylsilylazide. The cycloadduct easily rearranges to the diazo derivatives R2P(=NSiMe3) C (=N2) SiMej. The addition of the... 

Reaction of PF R (R=Me, Ph, F) with a carbene results in the six-coordinate phosphorus species PF R(carbene). The phosphorus compound acts as a Lewis acid toward the Lewis basic carbene, and the phosphorus resonance is shifted upfield by about Afine structure of this upfield shift is of considerable interest. The electronegativity of the substituent R increases in the order Me < Ph < F in accord with an upfield shift in the phosphorus resonance. Therefore, we again witness a case where the loss in electron density through the donor interaction, in the present case from the fluoride substituents on phosphorus. As the influence of the. -bonding interaction on the phosphorus chemical shift is larger than that of the bonding interaction, we witness a net upfield shift. 

This same disconnection of a carbon atom is also helpful for epoxides (11) without carbonyl substituents. The reagent should be a nucleophilic carbene equivalent and a sulphur ylid (12) is the answer.These can be made from the sulphide (13) by a similar process to phosphorus ylid synthesis (Chapter 15), though the reactions of the two ylids with carbonyl compounds are significantly different (there is a third type of reaction with the ylid CH2N2 in Chapter 31). 

In a novel interconversion, the phosphine sulphide 192 reacts with nitrosyl chloride to give the phosphinothioic cyanate 193 which, when irradiated, isomerizes to the iso-cyanate. Two unusual reactions (equations 10 and 11) result from the photolysis of derivatives of (diazomethyl)phosphonothioic diamide derivatives. Yet a further unusual reaction is experienced by the monoanion 194 when irradiated in MeOH, and which is thought to proceed with the cyclization of the carbene intermediate to give an oxaphos-phirane, methanolysis of which results in ring opening with phosphorus arbon bond fission . ... 

Most of the reactions encountered with the carbon-substituted carbenes are found with phosphorus substitution. Typically, the irradiation of a-diazobenzylphosphonate in the presence of 2-methylbut-2-ene results in the formation of a cyclopropane. Group migration is also observed as in the irradiation of the diazo compound 506, which in benzene yields the product 507 formed by the 1,2-migration of an amino group from phosphorus to carbon, while in methanol the adduct 508 is formed . A 1,2-phenyl migration from phosphorus to carbene occurs on irradiation of 509 to yield 510. ... 

Oxazoles.—Formation. ci)-Diazoacetophenone reacts with benzonitrile in the presence of trifluoromethanesulphonic acid to give 2,5-diphenyloxazole (514). Bi-, ter-, and quater-oxazoles have been synthesized from a-metallated isocyanides thus lithiobenzyl isocyanide (PhCHLiNC) and dimethyl oxazole-3,4-dicarboxylate afford compound (515). Stable methylene-oxazolines (516 R = Me or Ph) are obtained by heating the iminesHN=C(Ph)OCHRC=CH. The fluorinated oxazoline (518) results from the action of benzonitrile on the oxiran (517), and also from the reaction of bis(trifluoromethyl)carbene with the benzoylimine (CF3)2C=NCOPh/ Treatment of 2-acylamino-l-aryl-alkan-l-ols (519) under the conditions of the Pictet-Gams reaction, i.e. with phosphorus pentoxide in boiling toluene or xylene, results in cis- and trans-2-oxazolines (520), rather than isoquinolines, as claimed previously. The spiro-oxazolines (521 R = Me or Ph) are formed when the lithiated di-isocyanide CN—CH2CH2CHLi—NC is treated with acetone or benzophenone, respec-tively. ... 

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