Phosphines, Trimethylsilyl

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]. 

Fig. 3. Synthesis of diacidic and monoacidic N-1 a2etidinone phosphonates and phosphinates where TMSBr is trimethylsilyl bromide BSA is...

An alternative method for preparing phosphinous amides makes a profit on the high affinity between silicon and halogen atoms. This is the driving force of the reactions between halophosphanes and Ar-(trimethylsilyl)anilines, AT-(tri-methylsilyl)amides or AT-(trimethylsilyl)ureas and thioureas, as represented in the Scheme 6. In these processes the desired P-N bond and an halosilane are simultaneously formed [53,58-60]. 

An interesting [1,3]-Si shift from nitrogen to nitrogen has been observed in the Staudinger imination reaction of AT-ferf-butyl-iV-trimethylsilyl-P,P-di-methyl phosphinous amide 32 with trimethylsilylazide [137]. The steric bulk provided by the tert-hutjl group seems to determine the direction of the silyl shift (Scheme 32). 

Another method that has been used to prepare phosphaalkenes is the phos-pha-Peterson reaction, a phosphorus analog of the Peterson olefination [46-49]. In this reaction a lithium silylphosphide is treated with an aldehyde or ketone to yield the phosphaalkene (9). Analogous reactions can be conducted with bis(trimethylsilyl)phosphines (10) and ketones (11) using a catalytic quantity of anhydrous base (i.e., NaOH, KOH) [50]. Generally, the reactions proceed cleanly and in high yield. Sufficiently bulky substituents must be employed to stabilize the P=C bond and prevent rapid dimerization to 1,3-diphosphetaines. 

Bis(trimethylsilyl)phosphines 1681, whose chemistry has been reviewed [5], condense with DMF and eliminate HMDSO 7 to give, e.g., the phosphaalkene 1682 [6]. Bis(trimethylsilyl)phosphines 1681 react with bis(dialkylamino)difluoro-methanes 1683 with elimination of Me3SiF 71 to give the phosphaalkenes 1684 [7, 8], whereas acid chlorides such as Me3CCOCl afford, with elimination of TCS 14, the O-trimethylsilylphosphaalkenes 1685 [9]. Bis(trimethylsilyl)phosphines 1681 condense with CO2 to the phosphacarbamates 1686 [10] whereas CS2 furnishes the methylenephosphanes 1687 [11, 12] (Scheme 11.1). 

Carbon-phosphorus double bonds are also formed in addition reactions of tris(trimethylsilyl)phosphine 1692 (which can be readily prepared from white phosphorus, sodium, and TCS 14 [13a,b,c]) to give oxazohum fluorides 1691 which then give the azaphospholes 1694, via 1693 [3, 14]. On addition of 1692 to 1695, the diazaphosphole 1696 [3, 15] is prepared, whereas l,3-azaphospholo[l,2a]pyridines 1698 [16] are formed from 1692 and 1697, and 1,3-thiaphospholes 1700 are formed from the dithiohum fluorides 1699 [17]. l,3-Benzodiphospholyl anions 1703 are generated by reaction of acid chlorides with the dihthium salts 1701, via 1702 [18] (Scheme 11.3). 

The catalytic arylation of SEM-protected azoles (SEM = [2-(trimethylsilyl) ethoxy]methyl) with monocarbene-Pd(ll) complexes [72], and the reductive Heck or hydroarylation of norbomenes with NHC-phosphine chelating ligands... 

Bis(trimethylsilyl)peroxide (1) can be used to produce phosphine oxides stereospecifically from either phosphines (with retention) or phosphine sulphides (with inversion).1 A variety of organoelement substituted pentadienes, including the phosphine oxides (2) and (3),... 

Dialkyl zinc compounds form phosphine complexes of formula RZnP(SiMe3)2 on addition of one equivalent of bis(trimethylsilyl)phosphine. Solution and solid-state studies showed that the complexes are dimeric or trimeric in solution or the solid state. Bis(trimethylsilyl)phosphido-methylzinc crystallizes as a trimeric molecule with a Zn3P3 core in the twist-boat conformation. Bis(trimethylsilyl)phosphido- -butylzinc, shows a similar central Zn3P3 fragment. The sterically more demanding trimethylsilylmethyl substituent forms a dimeric species of bis(trimethylsilyl) phosphido-trimethylsilylmethylzinc. Solution studies of bis(trimethylsilyl)phosphido- .vo-propyl-zinc demonstrate a temperature-dependent equilibrium of the dimeric and trimeric species and the crystalline state contains a 1 1 mixture of these two oligomers. A monomeric bis(trimethyl-silyl)phosphido-tris(trimethylsilyl)methylzinc has also been synthesized.313... 

Phosphides and amides are closely related, as a synthetic route is based on metathesis of metal amides, especially the respective trimethylsilyl amides, with the appropriate free acidic phosphine or an anion derived therefrom. Reaction of metal halides and trisilylphosphines is an alternative for preparing metal phosphides. 

Niecke, E. et al., Angew. Chem. (Intern. Ed.), 1983, 22, 486 Highly pyrophoric, like the tetrakis(trimethylsilyl) analogue. See related alkylsilanes, phosphines... 

Heterocyclic phosphines 32 were prepared from base-induced condensation of a secondary 1,8-diamino-naphthalene with phosphorus trichloride (the corresponding As- and Sb-analogues were obtained analogously) and converted into cyclic phosphenium cations 33 by Lewis acid promoted halide abstraction using GaCl3 or trimethylsilyl triflate as reagents (Scheme 18) [15, 92],... 

Use of tris(trimethylsilyl)phosphine as the phosphorus furnishing reagent in condensation reaction with a-diazocarboxylic chlorides (7) gave 2-trimethylsilyl-[l,2,3]diazaphospholes (9) in good yields (Scheme 3) [18],... 

Similar results for the replacement of halogen on an olefinic linkage by phosphorus have been accomplished using dialkyl phosphites with palladium(O) catalysts.4179 Another reaction involving replacement of a vinylic halide by phosphorus utilizes palladium catalysis with a trimethylsilyl-substituted phosphine (Figure 6.19).80... 

A convenient route to j3-phosphorus nitroxides involves the 1,3-addition of trimethylsilyl phosphites (e.g., diethyl) or trimethylsilyl phosphines (e.g., diphenyl) to aldo nitrones (e.g., a-PBN, DMPO), or keto nitrones (e.g., 2-Et-DMPO or 2-Ph-DMPO), to form a-phosphityl- or a-phosphinyl-O-silylhydroxyl-amines. Acidic hydrolysis provides the corresponding hydroxylamines which are easily oxidized to p-phosphorus-nitroxides (690). 

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