Phosphines, reactions with alkynes

Enantioselective catalysts have been developed for cyclization of dienyl aldehydes and coupling of aldehydes with alkynes (Equations (74) and (75)). For reactions with dienes see Refs 433 and 433a, and for reactions with alkynes see Refs 433b I33e. Chiral monodentate phosphines have proved to be effective. 

Kawamoto, A.M., and Campbell, M.M., A new method for the synthesis of a phosphonic acid analogue of phosphoserine via a novel 1,1-difluorophosphonate intermediate, J. Fluorine Chem.. 81, 181, 1997. Burton, D.J., Naae. D.G., Flynn, R.M., Smart, B.E., and Brittelli, D.R.. Phosphine- and phosphite-mediated difluorocarbene exchange reactions of (bromodifluoromethyl)phosphonium salts. Evidence for facile dissociation of (difluoromethylene)triphenylphosphorane. J. Org. Chem.. 48. 3616, 1983. Li, A.-R., and Chen. Q.-Y., Diethyl iododifluoromethylphosphonate. A new synthetic method and its reaction with alkynes. Synthesis, 606, 1996. 

Neat reactions of liquid substrates can be quite successful. For example, the addition of P(0)-H bonds to alkenes has been accomplished using microwave irradiation in the absence of added solvent or catalyst (Scheme 25.4b). Tandem hydrophosphinylation reactions with alkynes afforded unsymmetrical species such as phosphine oxide—phosphinates. 

Fluoromethylidyne and Difluoromethylidene. Bismethylidyne complexes of iron are themselves somewhat rare. For example, when Lentz and co-workers first prepared nonacarbonylbis( i3-fluoromethylidyne)triiron, [Fe3(CO)9( X3-CF)2] (137), it was only the second known compound to contain the Fe3(CR)2 moiety. Since then, Lentz has extended the chemistry of this compound by studying (1) its reactions with alkynes (138-140), a phosphaalkyne (140,141), and Lewis acids (140,142), (2) its carbonyl substitution chemistry with nitriles and phosphines (143),... 

Addition Reactions of sec-Phosphine Oxides with Alkynes. 179... 

Reaction of benzonitrile A-oxide with alkynic phosphinate (343) gave exclusively 5-phosphinylisoxazole (344), whereas reaction with enamine phosphinate (345) gave the otherwise inaccessible 5-unsubstituted 4-phosphinylisoxazole (346) (80JOC529). 

The diiridium complex [Ir(CO)(PPh3)(/x-pz)]2 forms a diiridacyclobutene adduct of the type 143 with Me02CCsCC02Me, while the same reaction with F3CC=CCF3 leads to alkyne polymerization owing to dissociation of triphenyl-phosphine (85OM2106). 

The diamagnetic ylide complexes 34 have been obtained from the reaction of electron-deficient complexes [MoH(SR)3(PMePh2)] and alkynes (HC=CTol for the scheme), via the formal insertion of the latter into the Mo-P bond. The structural data show that 34 corresponds to two different resonance-stabilized ylides forms 34a (a-vinyl form) and 34b (carbene ylide form) (Scheme 17) [73]. Concerning the group 7 recent examples of cis ylide rhenium complexes 36 cis-Me-Re-Me) have been reported from the reaction of the corresponding trans cationic alkyne derivatives 35 with PR" via a nucleophilic attack of this phosphine at the alkyne carbon. 

A related unprecedented double insertion of electron-deficient alkynes has also been reported in the reactions of the linear Pt2Pd heterotrimetallic complex 64 with 65 (RO2CCSCR) (Scheme 24) [95,96]. A series of unsymmetri-cal A-frame clusters 68 has thus been obtained in which a first insertion of the alkyne takes place site-selectively into the Pt-Pd bond vs the Pt-Pt bond (66). After a zwitter-ionic polar activation of the resulting inserted alkene (67), a subsequent reaction with the phosphine unit of the dpmp allows one to obtain the products 68 via the nucleophilic migration of the terminal P atom from the Pd center to the CH terminal carbon (formation of the P-C bond). 

The chemistry of the phosphirene system is attracting increasing attention, with the eventual goal of preparing the potentially aromatic Huckel system (214). A simple preparation of tervalent phosphirenes (215) is afforded by the reactions of dichloro-phosphines with alkynes in the presence of aluminium chloride,... 

Recently, a further unique domino methodology has been reported by Lu and coworkers (Scheme 2.74) [173]. Herein, a triphenyl phosphine-catalyzed umpolung addition/cyclization of allenes and alkynes containing an electron-withdrawing group 2-316-2-318 followed by reaction with a double nucleophile 2-319 is assumed to account for the production of a broad palette of various heterocycles 2-321 and 2-323 via 2-320 and 2-322, respectively. Dihydrofurans, piperazines, morpholines and diazepanes were obtained during the process. 

Figure 18.11 NHS-PEG4-azide can be used to modify an amine-containing molecule to create an amide derivative terminating in azido groups. The azide modifications then can be used in a click chemistry reaction that forms a triazole linkage with an alkyne-containing molecule. Alternatively, the azide derivative can be used in a Staudinger ligation reaction with a phosphine derivative, which results in an amide bond linkage.

A Michael-type addition reaction of phosphine generated from red phosphorus in concentrated aqueous KOH solution has been noted to provide moderate isolable yields of pure organophosphorus products.27 For example, tris-(2-cyanoethyl)phosphine is produced in 45% isolable yield from acrylonitrile, and tris-(2-[y-pyridyl]ethyl) phosphine oxide is isolated in 40% yield from 4-vinylpyridine under these conditions. Excellent yields of the tertiary phosphine oxide, tris-(2-cyanoethyl)phosphine oxide, have been reported using white phosphorus in absolute ethanol with KOH at ice/salt-bath temperatures.28 A variety of solvent systems were examined for this reaction involving a Michael-type addition to acrylonitrile. Similarly, tris-(Z-styryl)phosphine is produced from phenylacetylene under these conditions in 55% isolated yield. It is noteworthy that this last cited reaction involves stereospecific syn- addition of the phosphine to the alkyne. 

A palladium(0)-phosphine complex also catalyzes insertion of phenylacetylene into the Ge-Ge bond of a benzo-digermacyclobutene (Equation (57)).138 Reaction of a cyclotetragermane with alkynes was also reported.139... 

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