Olefins tris phosphite

Tolman, C.A. (1974) Olefin complexes of nickel(0). III. Formation constants of (olefin)bis(tri-o-tolyl phosphite) nickel complexes. /. Am. Chem. Soc., 96, 2780. 

The trimethylsilylated ylides (1), easily generated from trimethyl chlorosilane and ylides, react with aldehydes 2 to form vi-nylsilanes 3 (2,3). The vinylphosphonium silanolates 4 are also formed. Compounds 3 are versatile reagents for further reactions (4). The ylide J (with R1 =H) reacts with aldehydes 2 to give the dienes j). The oxidation of with the adduct 6, from triphenyl-phosphite and ozone, gives access to a generaT synthesis of acyl-silanes (trimethylsilylketones) (2). The silylated ylides react to form phosphonium salts 7 with halogen compounds. The salts 7.can be desilylated by fluorine ions. The disubstituted ylides JO Tormed can be converted in statu nascendi with aldehydes V[ into the tris-substituted olefin J2 (2,3). In the case of R3-I, vinyl... 

The di-O-tosylates (prepared by action of tosyl chloride in pyridine) are reduced with zinc (Nal/Zn route e Tipson-Cohen reaction) [13]. Cyclic ortho-esters (prepared by reaction of the diol with ethyl orthoformate) are transformed into olefins by simple heating in the presence of acids (Eastwood reaction, route b) [14]. Cyclic thiocarbonates (obtained by reaction of a diol with thiophosgene or (V,(V -thiocarbonyl-di-imidazole) are reduced to olefin with trimethyl phosphite (Corey-Winter method, route c) [15]. Finally, reduction of vicinal di-xanthates with tri- -butyltin hydride according to the Barton procedure [16] affords olefins via a reductive elimination process route a). The Corey-Winter, Garegg, and Tipson-Cohen methods are most commonly applied for deoxygenation of sugar diols. 

The employment of bulky phosphite ligands , e.g., tri(o-t-butylphenyl)phos-phite, yields high reactivity catalysts for the hydroformylation of very low reactivity j8-alkyl-a-olefins, e.g. isoprene. Diorganophosphites such as 3 overcome many of the problems associated with the employment of simple triarylphosphites under hydroformylation reaction conditions such as reaction of the phosphite with the product aldehyde, trans-esterification and organometallic degradation reactions. 

Tris(tri-o-tolyl phosphite)nickel(O),4 likewise a useful catalyst,5 is conveniently prepared by displacement of ethylene from the olefin complex by a mole of phosphite ligand as described in Sec. B. Alternatively, it can be prepared directly by reduction of hydrated nickel nitrate with sodium tetrahydroborate in acetonitrile (Sec. C). This method avoids the need to handle spontaneously flammable triethylaluminum. 

The prq>aTatioa of NiC3F2CFssCF2CF2 P(0-o-tolyl)3 2 (138) from C2F4 and tris(tri-o-tolyl phosphite)nickel under conditions where other olefins give three-... 

Nickel(0) catalysts have featured prominently in this field with tetrakis(tri- -tolyl phosphite)nickel(O) allowing regio-selective Markovnikov addition of hydrogen cyanide to olefins at temperatures above 50°C. Interestingly, addition of Lewis acid hydrocyanation promoters reduced the selectivity of the reaction. 

The authors have also demonstrated that the chemoselective binding of the Rh catalyst to the allene r-system could be altered by changing the electronic property of the catalyst system. Employing tris(hexafluoro-2-propyl)phosphite as the additive, the Rh catal3rst selectively reacted with the terminal olefin of the allene 98 to furnish the 6-6-fiised ring product 99, which is analogous to the nickel-catalyzed reaction (97) (Scheme 50). 

Sterically demanding phosphites such as tris(o-t-butylphenyl) phosphite and phosphites with low basicity such as tris(hexafluoroisopropyl) phosphite were found to give high rates of hydroformylation even in the case of less reactive olefins such as 2-methyl-1-hexene, limonene, or cyclohexene (249). 

Dissociation of a ligand is accelerated for bulky ligands. We shall see in Section 9.4 how this affects the dissociation of a phosphite from NiL4 in a key step in olefin hydrocyanation, an important catalytic reaction. The degree of dissociation can be predicted from the appropriate cone angles, and the bulky phosphite P(0-o-tolyl)3 makes one of the very best catalysts. Tri-phenylphosphine is very useful in a wide variety of catalysts for the same reason. 

Tris(nonylphenyl)phosphate (TNPP) is a common commercial phosphite. Note that this is not n-nonyl, hut rather a mixture of branched C9 isomers. Nonylphenol is commercially synthesized through Friedel-Crafts alkylation of phenol with nonene. Technical nonene ( propylene trimer ) is a mixture of predominantly C9-olefins with varying degrees of branching. The resulting nonylphenol is mainly a mixture of 4-substituted monoalkylphenols with various isomeric, branched nonyl groups [13]. Tris(2,4-di-t-butylphenyl)phosphite is another commonly used phosphite. 

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