Tris phosphine, reaction

In Figure 1, the observed reactions are indicated in the context of a proposed catalytic scheme for terminal hydroformy-lation. The reaction pathway involving the alkyl phosphine intermediate (VIII) is the most likely. Overall, the results of the NMR studies provide consistent explanations for the process parameters of selective hydroformylation, particularly of the low pressure continuous product flashoff process (.5,15). it was shown that, in contrast to prior indications (3), the tris-phosphine complex (I) is a remarkably stable and favored species in the presence of excess phosphine and H2. This complex (I) is postulated to have a key role in the reversible generation and... 

The mechanism of the oxidative addition of aryl bromides to the bis-P(o-tolyl)3 Pd(0) complex 3 was surprising [196]. It has been well established that aryl halides undergo oxidative addition to L2Pd fragments [197 -200] thus, one would expect oxidative addition of the aryl halide to occur directly to 3 and ligand dissociation and dimerization to occur subsequently. Instead, the addition of aryl halide to [Pd[P(o-tolyl)3]2] occurs after phosphine dissociation, as shown by an inverse first-order dependence of the reaction rate on phosphine concentration and the absence of any tris-phosphine complex in solution [196]. 

Many of the complexes discussed in the previous sections are catalysts for alkyne oligomerization. In fact, alkyne dimerization and trimerization (see Cyclodimerization -tri-merization Reactions) at a cobalt center is recognized as one of the most synthetically useful catalytic reactions mediated by a homogeneous transition metal complex. The cobalt complexes most useful and extensively studied are CpCoL2, where L is CO, alkene, diene, or phosphine. The complex types... 

The preparation of chelating surface-active diphosphines proved to be more successful. The BDPP analogue R,R-(9) was synthesized by lithiation of tris[p-(3-phe-nylpropyl)phenyl]phosphine, reaction with (R,R)-2,4-pentane-diylditosylate and subsequent sulfonation with concentrated sulfuric acid [16]. Hydrogenation of the prochiral olefin (Z)-2-(N-acetamido)cinnamic acid ester in a two-phase system (ET0Ac/H20) with Rh complexes derived from R,R-(9) was accomplished with identical selectivity compared with the unsulfonated BDPP and improved reactivity compared with BDPPTS (2). 

The tris(phosphine) alkylidyne derivatives similarly serve as precursors for ligand displacement reactions. The alkylidyne complex m r-Mo( = CC6H40Me-2) Cl(CO) P(OMe)3 3 reacts with K[Bp] leading to rm -BpMo( = CC6H40Me-2) (CO) P(OMe)3 2 (Scheme 7). The dimethylphenyl phosphine analogue... 

The coupling of the enol triflate 703 with the vinylstannane 704[397] has been applied to the synthesis of glycinoeclepin[576]. The introduction of a (Z)-propenyl group in the / -lactam derivative 705 proceeds by use of tri-2-furylphosphine[577]. However, later a smooth reaction to give the propenyl-iactam in 82% yield was achieved simply by treating with Pd(OAc)2 in NMP or CH2CI2 for 3-5 min without addition of LiCI and the phosphine ligand[578]. 

The mixed triarylphosphine 787 can be prepared by the reaction of (trimethylsily )dipheny phosphine (786) with aryl halides[647]. Ph3P is converted into the alkenylphosphonium salt 788 by the reaction of alkenyl tri-flates[648]. 

Formic acid behaves differently. The expected octadienyl formate is not formed. The reaction of butadiene carried out in formic acid and triethylamine affords 1,7-octadiene (41) as the major product and 1,6-octadiene as a minor product[41-43], Formic acid is a hydride source. It is known that the Pd hydride formed from palladium formate attacks the substituted side of tt-allylpalladium to form the terminal alkene[44] (see Section 2.8). The reductive dimerization of isoprene in formic acid in the presence of Et3N using tri(i)-tolyl)phosphine at room temperature afforded a mixture of dimers in 87% yield, which contained 71% of the head-to-tail dimers 42a and 42b. The mixture was treated with concentrated HCl to give an easily separable chloro derivative 43. By this means, a- and d-citronellol (44 and 45) were pre-pared[45]. 

The unsaturated c.vo-enol lactone 17 is obtained by the coupling of propargylic acetate with 4-pentynoic acid in the presence of KBr using tri(2-furyl)-phosphine (TFP) as a ligand. The reaction is explained by the oxypalladation of the triple bond of 4-pentynoic acid with the ailenyipailadium and the carbox-ylate as shown by 16, followed by reductive elimination to afford the lactone 17. The ( -alkene bond is formed because the oxypalladation is tnins addition[8]. 

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