Addition Reaction of Phenylphosphines to Styrenes as the Model of Polyaddition. Study on the Rate-Determining Step and Substituent Effect

Abstract

ABSTRACT:The addition reactions of phenylphosphine or diphenylphosphine to styrenes or a-methylstyrene were carried out to know the reaction mechanism and the transition state of the addition reaction. Phenylphosphine having two reactive hydrogens added to two styrenes, and the I: 2 adduct [q,CH2 CH2P(q,)CH 2 CH2 q,J of the anti-Markownikoff's structure was obtained in a 94% yield. But, a little amount of the by-product containing styrene-styrene unit was produced as compared with the reaction of thiophenol to styrene. Such a side reaction was suppressed by using a-methyl styrene instead of styrene. The kinetics of the addition reaction of the P-H group to the vinyl group was investigated in detail by the addition reaction of diphenylphosphine to styrene, to give scarcely by-product. The rate-determining step of the reaction was the chain transfer step between the intermediate carbon radical (q,CHCH 2 Pq,2) and diphenylphosphine. In the para substituent effect of styrenes on the chain transfer step, fairly good linear correlation was obtained with modified Hammett's equation including the resonance effect. The rate-determining step and the substituent effect on this reaction were found to be similar to those of the addition reaction ofthiophenol to styrenes. The results were also compared with the polyaddition of phenyl phosphine to 1,4-divinylbenzene or 1,4-diisopropenylbenzene.KEY WORDS Kinetics / Polyaddition / Addition Reaction / Reaction Mechanism / Rate-Determining Step / Substituent Effect / Hammett Correlation / Phenylphosphine / Diphenylphosphine / Styrene Derivatives / Primary and secondary phosphines have been known to add to alkenes, similar to the addition reactions of thiols to alkenes. The radical addition initiated by UV light,l radical initiator, 2 or X-ray2 is the convenient way of carrying out the addition reaction. For example, bis(2-cyanoethyl)phosphine reacted with l-octene in the presence of AIBN at 7S-140°C to give the tertiary phosphine in a 74% yield. 2 Such the addition reaction seems to proceed by a radical chain mechanism. 3 However, no extensive investigation about the addition mechanism has been undertaken.In the present paper, two model addition reactions were investigated in detail to know the polymerization mechanism and the polymer structure of phenylphosphine (PH) with 1,4-divinylbenzene (DVB) or 1,4-diisopropenylbenzene (DIPB). The model addition reactions of PH to styrene (St) and to oc-methylstyrene (MSt) were studied to make clear the reaction behavior with primary phosphines and olefins. The detailed kinetic behavior such as the rate-determining step and substituent effect on the addition reaction of P-H group to vinyl group were also inves-* To whom all correspondence should be addressed. 1039T. OBATA et al. tigated by the model addition reaction of diphenylphosphine (DPH) to St. These results were discussed by comparing with the addition reaction ofthiophenol (TP) to St 4 and with the polyaddition of PH to DVB 5 or DIPB. 5 EXPERIMENTAL ReagentsPH 6 and DPH 7 were p...

Zirconium-Catalyzed Intermolecular Double Hydrophosphination of Alkynes with a Primary Phosphine

“…Attempts to isolate the vinyl phosphine intermediate by vacuum distillation were hindered by the similar volatilities of both the vinyl and saturated phosphines. Isolation of 5 by vacuum distillation provided identical spectroscopic data as that for the authentic compound. , …”

“…Isolation of 5 by vacuum distillation provided identical spectroscopic data as that for the authentic compound. 25,31 Nakazawa's iron catalyst that successfully engages in double hydrophosphination of terminal aryl alkynes has not been demonstrated to be effective with internal alkyne substrates. 12,17 In this regard, compound 1 and CpFeMe(CO) 2 represent a highly complementary pair of catalysts in this exceedingly rare double hydrophosphination reaction.…”

“…Treatment of a vinyl phosphine product with a second equivalent of PhPH 2 provides the corresponding 1,2-bis-(phosphino)ethane as a mixture of rac and meso isomers in high yields with 31 P NMR chemical shifts in the range of −28 to −41 ppm. The reaction proceeds with regioselective addition of the P−H bond across the alkyne such that no formation of the 1,1 addition product is observed.…”

Synthesis and Characterization of a Family of Air-Stable Ferrocene- and Ruthenocene-Containing Primary, Secondary, and Tertiary Phosphines

“…Two additional portions of vinylruthenocene and AIBN were then added, and the reaction mixture was heated to produce secondary and tertiary phosphines 8b and 8c . We favored a strategy that employed multiple AIBN/vinylruthenocene additions in order to limit radical concentration and disfavor formation of α-addition byproducts (i.e., 9 ) . As vinylruthenocene and primary phosphine 8a have similar polarities, their separation by column chromatography is not trivial.…”