3.4- Dimethyl- 1-phenylphosphole, complex

Another intriguing example of reactivity specific to phospholes and their complexes is given by the formation of 3,4-dimethyl-phenylphosphole in the coordination sphere of a metal as illustrated in Scheme 115 (see also Section 3.15.5.2.2) <2004JOMC4647>. Here, treatment of the phospholyl complex 344 with Bu Li affords the corresponding 77 -bound phosphole complex 345, which reacts with Pd(ii) to generate the bimetallic 7] -Mn cr-Pd complex 346 that has been characterized in the solid state by X-ray diffraction. Notably, the P-Mn bite angle of 65° is typical of other dimeric Pd2Cl2 complexes. The 77 -bound C4 moiety shows the expected bond localization. 

UV irradiation. Indeed, thermal reaction of 1-phenyl-3,4-dimethylphosphole with (C5HloNH)Mo(CO)4 leads to 155 (M = Mo) and not to 154 (M = Mo, R = Ph). Complex 155 (M = Mo) converts into 154 (M = Mo, R = Ph) under UV irradiation. This route was confirmed by a photochemical reaction between 3,4-dimethyl-l-phenylphosphole and Mo(CO)6 when both 146 (M = Mo, R = Ph, R = R = H, R = R" = Me) and 155 (M = Mo) resulted (89IC4536). In excess phosphole, the product was 156. A similar chromium complex is known [82JCS(CC)667]. Complex 146 (M = Mo, R = Ph, r2 = R = H, R = R = Me) enters [4 -H 2] Diels-Alder cycloaddition with diphenylvinylphosphine to give 157. However, from the viewpoint of Woodward-Hoffmann rules and on the basis of the study of UV irradiation of 1,2,5-trimethylphosphole, it is highly probable that [2 - - 2] dimers are the initial products of dimerization, and [4 - - 2] dimers are the final results of thermally allowed intramolecular rearrangement of [2 - - 2] dimers. This hypothesis was confirmed by the data obtained from the reaction of 1-phenylphosphole with molybdenum hexacarbonyl under UV irradiation the head-to-tail structure of the complex 158. 

Reaction of the 3,4-dimethyl-1-phenylphosphole (L) complex [PdLjClj] with 1-vinylimidazole in the presence of silver perchlorate carried out in... 

The 3,4-dimethyl-l-phenylphosphole (the so called Mathey-phosphole ) entered into Friedel-Crafts acylation only through its molybdenum complex (20). Elimination of the Mo(CO)5 moiety from product 21 furnished 2-acylphosphole 22 (.Scheme 5) [42],... 

Phosphinidenes (R-P), short-lived, reactive intermediates that are isoelec-tronic with nitrenes and carbenes, are accessible by fragmentation of phos-phiranes, phosphol-3-enes, triazaphospholenes, and oxazaphospholenes and can be characterized by trapping reactions. The metal-complexed species [R-P-M, e.g., M = W(CO)5] are more stable (but also not isolable) and react more selectively. As a model example we describe the transformation of (3,4-dimethyl-l-phenylphosphole)(pentacarbonyl)tungsten 4 with dimethyl acetylenedicarboxylate to the 7-phosphanorbomadiene derivative 5.11 The (phosphinidene)(pentacarbonyl)tungsten complex 6 is generated from the latter by a [4+ 1]-cycloreversion and trapped with diphenylacetylene via a [2+1]-cycloaddition to furnish the triphenyl-2-phosphirene complex 7 (Scheme l).12... 

Notably, it is not just heteroatom-functionalized alkenes that can behave as dienophiles with metal-bound phospholes. It has been demonstrated that reaction of 2equiv of 3,4-dimethyl-l-phenylphosphole with a cationic platinum(n) complex of an enantiomerically pure cyclometallated A, A -dimethyl-l-(l-naphthyl)ethylamine ligand affords, following decomplexation with cyanide, the novel optically pure diphosphine (-f)-267 quantitatively as an air-sensitive oil (Scheme 93) <2000CC167>. The high-frequency chemical shift of one of the phosphoms centers (5 4.9 and 104.2 ppm (7pp = 43.9 Hz)) is indicative of rwt>-jy -stereochemistry. Similar reactivity has been... 

Planar chiral phosphaferrocene-oxazolines (379) constitute another family of complexes that are usefiil as ligands in asymmetric catalysis. Preparation of these takes advantage of a modified Friedel-Crafts acylation of (373) and an unusual conversion of the resulting trifluoromethyl ketone into an amide that is then cyclized to an oxazoline. The diastereomeric complexes thus formed are chromatographically separable and are used in a palladium-catalyzed asymmetric allylic substitution. Modification of this complex by using the anion derived from 3,4-dimethyl-2-phenylphosphole gives more... 

Compounds.- A third part of a review of P-H addition to unsaturated systems has appeared, covering addition to unsaturated ligands in the coordination sphere of a metal.Addition of diphenylphosphine to the free vinyl group of the [4+2]cycloadduct of 3,4-dimethyl-l-phenylphosphole and phenyldivinylphosphine (both in the form of metal complexes) has led to the unsymmetrical triphosphine (40), isolated as the related metal complex.A similar u.v.-induced addition to methyl(vinyl)cyclotetrasiloxane has given a tetraphosphine which, on treatment with acid, forms an... 

A vinylcarbene complex (76) also is capable of acting as a dienophile towards 3,4-dimethyl-1-phenylphosphole, again considered to be an intramolecular cycloaddition within the coordination sphere <880M2233>. A novel 7-phosphanorbornene derivative (77) was formed (Equation (11)). 

A Lewis salt (192) of 3,4-dimethyl-1-phenylphosphole with BHj is formed by reaction with H3B SMe2. The reaction occurs rapidly at 0°C and is near quantitative <940M925>. The salt can be deprotonated at a methyl group at — 80°C with sec-butyllithium the allylic ion (193) so produced reacts at the 2-position on protonation or methylation, giving the novel phosphine complexes (194) and (196) that are isomeric with phosphole complexes and can generate the free phosphole isomers (195) and (197) on decomplexation (Scheme 44). 

E = As, Sb or Bi) react similarly with Grignard reagents, providing routes to cyclic arsines, stibines and bismuthines. Leung s group has reported further applications of asymmetric Diels-Alder cyclisation reactions in phosphine synthesis. A platinum complex chiral auxiliary has been used to promote the asymmetric [4-1-2] Diels-Alder addition of diphenyl(vinyl)-phosphine to 3-diphenylphosphinofuran, giving the eradocycloadduct (70) as the predominant stereoisomer. Related cycloadditions between 3,4-dimethyl-1 -phenylphosphole and ester-functionalised allylic phosphines have provided chemoselective routes to optically-pure P-chiral 1,2- and... 

Leung et al. [152-167] proposed the Diels-Alder reaction of phospholes with various dienophiles catalyzed by palladium complexes 235 as a method for the synthesis of chiral phosphines. The chiral compounds containing S)-ortho-(l-dimethylaminoethyl)-naphthalene palladium 235 were complexed with diene, for example with 3,4-dimethyl-1-phenylphosphole, which then entered into the Diels-Alder reaction with dienophiles (W,W-dimethylacrylamide, styrene, and others) to result in diastereoisomers of entio-amidophosphanorbomenon complexes 236 and 237. After separation, purification, and decomplexation, the... 

Organopalladium complexes containing the (S)-form of ort/jo-palladated (l-(dimeth-ylamino)ethyl)-naphthalene have been used successfully as chiral templates to promote asymmetric cycloaddition reactions between coordinated 3,4-dimethyl-1 -phenylphosphole 8.34 and two dienophiles (A, A-dimethy lacrylamide and styrene) via two pathways, endo (compounds 8.35) with X=C1 and exo (com-ponnds 8.36) with X=0C103, which proceed as shown in Scheme 8.3 [23]. 

The cyclopalladated complex (naphthyl)ethylamine-6, iV]-dipalladium has been used as a chiral template to promote the intramolecular [4 -h 2] Diels-Alder reaction between diphenyl-vinylphosphine and 1-phenyl-3,4-dimethylphosphole. Halide-bridged palladium(ii) dimers of orthopalladated (S)-(-h)-7V,7V-dimethyl-Q -methylbenzylamine and (naphthyl)ethyl]amine were reported by the same authors.Solution and solid-state structures were determined as well as reactions with 3,4-dimethyl-1-phenylphosphole and allyldiphenylphosphine carried out. 

Asymmetric dimerisation of 3,4-dimethyl-1-phenylphosphole in the presence of an organoplatinum(II) complex derived from (R)-Ar,AT-dimethyl-l-(l-naph-thyl)ethylamine affords an optically pure P-chiral diphosphine. " " Reaction of racemic Sb-chiral (+ )-l-phenyl-2-trimethylsilylstibindole with di-p-chloro-bis (iS)-2-[l-(dimethylamino)ethyl]phenyl-C,Ar dipalladium(II) gives a 1 1 mixture of the diastereomeric complexes 51a and 51b. Separation of the complexes by chromatography followed by treatment with triphenylphosphine affords the optically pure l-phenyl-2-trimethylsilylstibinoles in quantitative yields. " The... 

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