Aryl phosphines, synthesis

The dithienophospholes 74 are obtained in good yields by lithiation of dibromo-bithiophenes 73, followed by addition of dihalo (aryl) phosphines (Scheme 4.22) [57]. The Lewis basicity of the P center of 74 enables a broad range of facile chemical modifications to be undertaken, as exemplified with the synthesis of derivatives 75-77 (Scheme 4.22) [57]. 

These nucleophilic reagents react with most common electrophiles such as organohalides, tosylates, aldehydes, ketones, epoxides, and activated alkenes. It should be noted that many workers have found much higher yields if the phosphides are protected as phosphine oxide or borane anions (see Section 3). Phosphide reagents also react with activated arenes to give mixed aryl phosphines (Protocol 2). Metal phosphides therefore provide an alternative, complementary tertiary phosphine synthesis to the electrophilic routes outlined in Section 2.1. 

Functionalized tertiary aryl phosphines play an important role in transition metal coordination chemistry. These compounds have been used as ligands in synthesis, catalysis, mechanistic studies, and in the study of coordination compounds as structural models. In this contribution the syntheses of two new types of these ligands, tertiary aryl phosphines functionalized by an amide group, are detailed. The published coordination chemistry of these compounds includes the study of intramolecular N—H oxidative addition, the synthesis of chelates stabilized amido complexes, and the preparation of complexes with both ftve- and six-membered chelate rings. ... 

Miscellaneous Methods of Preparing Phosphines. - Transformation of functional groups present in alkyl- and aryl-phosphines has been widely employed in the synthesis of new systems. Further examples of azine formation... 

The authors found that branched alkyl phosphines were not useful at all, whereas aryl phosphines afforded 1145 in acceptable yield but modest trans/cis selectivity (Scheme 1.298). However, both triethylphosphine and tri- -butylphosphine produced 1145 in nearly quantitative yield with 100 0 trans/cis selectivity. Operationally, the phosphonium salts were generated in situ, triethylphosphine was the reagent of choice. Similarly, the tranr-2-alkenyl bis- and ttis-oxazoles 1147—1150 were readily prepared. A further application of this methodology for the synthesis of ulapuahde A is discussed in Section 1.5.6. 

Imamoto and coworkers described phosphine-borane complexes as a coupling partner for the synthesis of aryl phosphines with aryl electrophiles using Pd(PPh3),j at room temperature (Scheme 20.68) [228,229], The borane moiety can be easily removed ljy excess use of diethyl amine or morpholine. Gaumont and coworkers demonstrated the palladium-catalyzed C—P cross-coupling in imidazolium-based ionic liquid and that the catalyst can be recycled up to six cycles [230]. 

Optically pure synthesis of IDX899 An aryl phosphinate-indole (API) as novel NNRTI with potent anti-HIV activity and enhanced barrier to resistance... 

While much of the attention in phosphine synthesis has been devoted to the use of aryl iodides, bromides, and chlorides, aryl fluorides can also be used. In addition to functionalizing aryl fluorides in superbasic conditions [277-279], Thiel reported the phosphorus-carbon bond-forming reaction using Me3SiPPli2 as the phosphinating agent and CsF as the... 

The development of new routes for the synthesis of phosphines is crucial for the synthesis of organophosphorus ligands for use in transition metal catalysis. Chemical transformations involving triple C-C bonds, such as nucleophilic addition and cycloaddition, are widely used for the synthesis of a diverse range of phosphines, which cannot be synthesized by other means [100], On the other hand, the [2- -2- -2] cycloaddition of alkynes catalyzed by transition metals are attracting much attention due to their use in the synthesis of various substituted aryl phosphines. This methodology can also be applied with other methods to synthesize various aryl phosphines [100, 101]. 

Carbon-carbon bond forming reactions constitute die core of organic synthesis, and novel, efficient methods are always desirable. One such reaction that has attracted much attention in recent days is the Morita-Baylis-Hillman (MBH) reaction the reaction of activated olefins with reactive carbonyls or imines in the presence of a catalytic amount of trialkyl(aryl)phosphine or amine (i-i). Of all the amines tested, 1,4-diazabicyclo[2.2.2]octane (Dabco) has been found to be superior (Scheme 1). This reaction, which provides multifunctional molecules has been accommodated in certain undergraduate curriculum (4), and does not demand any sophisticated techniques or instrumentation. 

The benzoic acid derivative 457 is formed by the carbonylation of iodoben-zene in aqueous DMF (1 1) without using a phosphine ligand at room temperature and 1 atm[311]. As optimum conditions for the technical synthesis of the anthranilic acid derivative 458, it has been found that A-acetyl protection, which has a chelating effect, is important[312]. Phase-transfer catalysis is combined with the Pd-catalyzed carbonylation of halides[3l3]. Carbonylation of 1,1-dibromoalkenes in the presence of a phase-transfer catalyst gives the gem-inal dicarboxylic acid 459. Use of a polar solvent is important[314]. Interestingly, addition of trimethylsilyl chloride (2 equiv.) increased yield of the lactone 460 remarkabiy[3l5]. Formate esters as a CO source and NaOR are used for the carbonylation of aryl iodides under a nitrogen atmosphere without using CO[316]. Chlorobenzene coordinated by Cr(CO)j is carbonylated with ethyl formate[3l7]. 

Synthesis. The first hiUy alkyl/aryl-substituted polymers were reported in 1980 via a condensation—polymeri2ation route. The method involves, first, the synthesis of organophosphine-containing alkyl or aryl substituents, followed by the ready oxidation of the phosphine to a phosphorane with leaving groups suitable for a 1,2-elimination reaction. This phosphorane is then thermally condensed to polymers in which all phosphoms atoms bear alkyl or aryl substituents. This condensation synthesis is depicted in Eigure 2 (5—7,64). 

They display the considerable trans-influence of hydride and aryl groups (the Pt-Cl bond lengths should be compared with the value of c. 2.31 A in PtCl4 ). The Pt-P bond lengths are more insensitive to the phosphine, but by synthesis of ds-Pt(PR3)(PR3)Cl2 [150] complexes, it has been possible to study the effect of electron-withdrawing substituents on the Pt-P bond, as well as on the trans-influence of the phosphine (Figure 3.94). 

Synthesis of Simple Alkyl/Aryl Primary Phosphines.123... 

Among /1-thiosubstituted organophosphorus compounds bearing chiral groups, phosphono methyl thiazolines (Sect. 2.2.1, Scheme 8) and o-sulfanyl aryl phos-phonamides or phosphinoxides (Sect. 3.3, schemes 20 and 21) have already been mentioned. As a complement to this, some recent synthesis of non racemic /1-sulfinyl phosphines and phosphonates and thiazolidinyl phosphonates are reported below. Moreover, some chiral )8-thio-substituted phosphines have been used as metal ligands in asymmetric catalysis and are listed in Sect. 5.3. 

---