Carbon-phosphorus bond forming reactions

The a-methoxylated derivatives are shown to be versatile synthons because of the reactivity of the methoxy group near the nitrogen atom, a-Methoxycarbamates, prepared by anodic oxidation, were used as key intermediates in the synthesis of a-amino acids,200 a new carbon-phosphorus bond-forming reaction,200 and in a new method of acylation of aliphatic amines at the -position.201 The application of this reaction to the synthesis of pyrrolidine, piperidine, and tropane alkaloids is also described.202... 

Carbon - Phosphorus Bond Forming Reactions at Room... 

Isoprene is treated with diethyl phosphonate in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium and l,2-bis(diphenylphosphino) ethane (DIPHOS) to give diethyl 3-methyl-2-butenylphosphonate (24) selectively (Scheme 2.14) [24], This protocol is used in various carbon-phosphorus bond forming reactions [38 2],... 

SCHEME 1.7 Example of a palladium-catalyzed carbon-phosphorus bond-forming reaction [19]. 

The synthesis of phosphorus-containing heterocycles has been reported using a palladium-catalyzed approach (Scheme 4.172) [261]. The overall process involved two phosphorus-carbon(sp ) bond-forming reactions and started with a hydrophosphonylation reaction using a supported palladium catalyst to promote the addition. Conversion of the... 

Carbon-phosphorus bonds are formed by the allylation of various phosphorus compounds. The allyldiphenylphosphine sulfide 346 is formed by the reaction of allylic acetates with lithium diphenylthiophosphide 343[215]. 

The Arbusov reaction is one of the best known methods for creating a carbon-phosphorus bond. In its simplest form (Michaelis-Arbusov) an alkyl halide reacts with a trialkyl phosphite to an alkanephosphonic acid diester as shown in Eq. (29) ... 

Pd-catalyzed asymmetric allylic alkylation is a typical catalytic carbon-carbon bond forming reaction [ 126 -128]. The Pd-complex of the ligand (R)-3b bearing methyl, 2-biphenyl and cyclohexyl groups as the three substituents attached to the P-chirogenic phosphorus atom was found to be in situ an efficient catalyst in the asymmetric allylic alkylation of l-acetoxy-l,3-diphenylprop-2-en (4) with malonate derivatives in the presence of AT,0-bis(trimethylsilyl)acetamide (BSA) and potassium acetate, affording enantioselectivity up to 96% and quantitative... 

In this chapter, we first review the nature of the several forms of elemental phosphorus and then proceed to consider their uses for specific types of syntheses of compounds containing the carbon-phosphorus bond. Prior reviews have also been concerned with these topics.1 2 Our purpose here is to update these presentations and provide fundamentals for the practicing chemist venturing into the use of elemental phosphorus. We limit this discussion to the more-or-less direct syntheses of organophosphorus compounds from elemental phosphorus. We will consider reactions that generate monophosphorus species without C-P bonds as critical intermediates, pro-... 

The Wittig reaction and its numerous derivations have undoubtedly proven to be one of the most useful and efficient methods for forming carbon-carbon double bonds . The reaction of an organophosphorus reagent with an aldehyde or ketone has also been frequently employed to extend simple dienals and dienones into more elaborate polyene systems. A key step in the convergent synthesis of the TB DMS-protected leukotriene A4 methyl ester, 19/ ,5 -Z-butyldimethylsiloxy-5S, 6S -epoxyeicosa-7 ,9 , 1IZ, 14Z-tetraenoate (43), was accomplished using a Wittig reaction between homoallylic phosphorus ylide 44 and Cl—Cll chiral epoxy dienal 45, derived from (—)-2-deoxy-D-ribose, shown in equation 29. ... 

Carbon-silicon bonds can be formed by treating the lithio intermediate with halogen-containing silanes (Reaction 22) (28). Carbon-phosphorus bonds can be prepared similarly (Reaction 23) (29). 

Instability in the supposedly stable phosphorus-carbon bond displays itself not only in unfortunate ways, leading as it does to side reactions and the formation, in synthesis, of unwanted by-products, but also in a constructive manner, forming the basis of reaction sequences of outstanding value in synthesis, as for example in alkene-forming reactions. Instability is an inherent property of (a-hydroxyalkyl)phosphonic acids which manifests itself in phosphorus-carbon bond cleavage as a result of the action of heat or of alkali, and which can lead either to dissociation into precursors or to rearrangement to phosphates (a-oxoalkyl)phosphonic derivatives are susceptible to attack by nucleophiles, a process which also results in carbon-phosphorus bond fission. 

Finally, it should be noted that distonic ions can be synthesized via phosphorus-carbon bond-forming reactions (equations 77-79) ... 

The reaction between alkyl halides and the anion of diethyl phosphonate, made by the ionization of the P-H bond by a very strong base, such as BuLi, to form a new carbon-phosphorus bond is known as the Michaelis-Becker reaction. 

An alternative approach to the synthesis of polyphosphazenes has also been reported [29, 30). In this process, the condensation reactions of N-silylphosphor-animines yield medium molecular weight poly(alkyl- and atyl-phosphazenes). The advantage of this route is that it yields polymers in which all the side groups are alkyl-or aryl- units bonded to phosphorus through carbon-phosphorus bonds - precisely those structures that are the most difficult to prepare by the classical route. Catalysis of these condensation polymerizations by BU4NF has also been described [31]. It has been demonstrated [32] that alkyl side groups can be lithiated, and these sites can form the basis of a lithium-replacement macromolecular substitution chemistry. 

Carbon-phosphorus bonds are formed by the Pd-catlyzed allylation of various phosphorus compounds (Scheme 13). The reaction of l-acetoxy-2-cyclohexene with LiPPh2 in refluxing THF provides an allylic phosphine in low yield (<15%). The phosphine produced deactivates the catalyst by coordination, which lowers the yield. In contrast, the reaction of LiP(S)Ph2 with l-acetoxy-2-cyclohexene takes place at room temperature to give allylic diphenylphosphine sulfides in 85% yield. ° Pd-catalyzed Michaelis-Arbuzov reaction of cinnamyl acetate with trimethyl phosphite affords a dimethyl allylic phospho-nate. With the reaction conditions being rather severe, this method may not be applicable to an allylic acetate that can produce a conjugated diene via /3-hydride elimination from the intermediate 7r-allylpalladium complex. 

A novel catalytic phosphorus-carbon bond forming-reaction, which proceeds in good yield without an additive, provides a powerful and environmentally sound entry to allylic //-phosphinic acids (132) (Scheme 45). ... 

Carbon-phosphorus bonds may also be formed. Chemists at Merck developed a synthesis of either enantiomer of the valuable ligand BINAP 133 from the more easily resolved BINOL 2.612, using a triflate-phosphine coupling reaction (Scheme 2.183). They reasoned that nickel catalysis would be more effective as this metal is harder than palladium and, therefore, less susceptible to catalyst poisoning by the product. BINAP 133 could be obtained with no loss of chirality. They also reported a resolution procedure for BINOL 2.612.224... 

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